Amyotrophic Lateral Sclerosis

Complex MONDO:0004976 Pathograph 54 Show in embeddings browser Motor Neuron Disease Neurodegenerative Disease

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a progressive neurodegenerative disorder characterized by the selective death of upper and lower motor neurons in the brain, brainstem, and spinal cord. This leads to progressive muscle weakness, atrophy, spasticity, and ultimately respiratory failure. ALS typically presents in adulthood with a median survival of 3-5 years from symptom onset. Approximately 5-10% of cases are familial, with the remainder being sporadic. A hallmark feature is TDP-43 proteinopathy, present in approximately 97% of cases.

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Classifications

Harrison's Part

Mechanistic Nosology

◆

Subtypes

Familial ALS

Hereditary form of ALS accounting for 5-10% of cases, with mutations in genes such as SOD1, C9orf72, TARDBP, and FUS.

Show evidence (1 reference)

PMID:21857683 SUPPORT BACKGROUND Human clinical

"Most cases of ALS are sporadic but about 5-10% are familial."

Source for the 5-10% familial share stated in this row, which was previously uncited.

Sporadic ALS

Non-hereditary form of ALS accounting for 90-95% of cases with unclear etiology.

Bulbar-onset ALS

ALS beginning with speech and swallowing difficulties due to bulbar motor neuron involvement.

Limb-onset ALS

ALS beginning with limb weakness, the most common presentation.

ALS6 (FUS, autosomal dominant) MONDO:0011951

FUS hgnc:4010

ALS caused by mutations in FUS, an RNA-binding protein with functional homology to TDP-43. The neuropathology departs from the TDP-43 proteinopathy that defines most of this entry: FUS-mutant cases carry FUS-immunoreactive cytoplasmic inclusions with predominantly lower motor neuron degeneration.

Show evidence (3 references)

PMID:19251628 SUPPORT Human clinical

"We have identified a missense mutation in the gene encoding fused in sarcoma (FUS) in a British kindred, linked to ALS6."

Ties FUS directly to the ALS6 locus designation that MONDO:0011951 denotes.

PMID:19251628 SUPPORT Human clinical

"Postmortem analysis of three cases with FUS mutations showed FUS-immunoreactive cytoplasmic inclusions and predominantly lower motor neuron degeneration."

Source for describing FUS-ALS neuropathology as FUS-inclusion rather than TDP-43 pathology.

PMID:19251628 SUPPORT BACKGROUND Other

"FUS is involved in the regulation of transcription and RNA splicing and transport, and it has functional homology to another ALS gene, TARDBP, which suggests that a common mechanism may underlie motor neuron degeneration."

Source for the statement that FUS is functionally homologous to TDP-43.

ALS8 (VAPB, autosomal dominant) MONDO:0012077

VAPB hgnc:12649

ALS from a founder missense change in VAPB. The same allele produces a spectrum rather than one phenotype: atypical ALS8, late-onset spinal muscular atrophy, and typical rapidly progressive ALS have all been reported in carriers, in kindreds that could not all be linked but that share a haplotype.

Show evidence (3 references)

PMID:15372378 SUPPORT Human clinical

"Here, we report the finding of a novel missense mutation in the vesicle-associated membrane protein/synaptobrevin-associated membrane protein B (VAPB) gene in patients from this family."

Identifies VAPB as the gene at the previously mapped ALS8 locus, establishing the gene-disease relationship for this subtype.

PMID:15372378 SUPPORT Human clinical

"Subsequently, the same mutation was identified in patients from six additional kindreds but with different clinical courses, such as ALS8, late-onset SMA, and typical severe ALS with rapid progression."

Source for the statement that one VAPB allele spans several motor neuron disease presentations.

PMID:15372378 SUPPORT Human clinical

"Although it was not possible to link all these families, haplotype analysis suggests a founder effect."

Source for calling the VAPB allele a founder allele.

ALS9 (ANG, loss of function) MONDO:0012753

ANG hgnc:483

ALS associated with heterozygous missense changes in angiogenin, an angiogenic ribonuclease expressed in motor neurons as well as endothelium. Functional assays place the mechanism in loss of ribonuclease activity, nuclear translocation, or both, rather than in a gain of toxic function.

Show evidence (3 references)

PMID:16501576 SUPPORT Human clinical

"We now report the finding of seven missense mutations in 15 individuals, of whom four had familial ALS and 11 apparently 'sporadic' ALS."

Establishes the ANG gene-disease relationship across familial and apparently sporadic cases.

PMID:17886298 SUPPORT In vitro / ex vivo

"Functional assays show that these ANG mutations result in complete loss of function."

Source for describing the ANG mechanism as loss of function.

PMID:17886298 SUPPORT Human clinical

"As a correlate, we demonstrate strong ANG expression in both endothelial cells and motor neurons of normal human spinal cords from the developing fetus and adult."

Source for the statement that angiogenin is expressed in motor neurons as well as endothelium.

ALS10 (TARDBP, autosomal dominant) MONDO:0012790

TARDBP hgnc:11571

ALS from missense mutations in TARDBP, the gene encoding TDP-43. This is the subtype in which the genetic lesion and the defining ALS neuropathology coincide: TARDBP encodes the protein whose cytoplasmic accumulation the TDP-43 Proteinopathy node models.

Show evidence (4 references)

PMID:18372902 SUPPORT Human clinical

"Here we report eight missense mutations in nine individuals--six from individuals with sporadic ALS (SALS) and three from those with familial ALS (FALS)--and a concurring increase of a smaller TDP-43 product."

Establishes TARDBP missense mutations in both familial and sporadic ALS.

PMID:20301761 SUPPORT REVIEW SYNTHESIS Human clinical

"The phenotypic spectrum encompasses pure (i.e., without other neurologic findings) amyotrophic lateral sclerosis (ALS; most common), pure (i.e., without other neurologic findings) frontotemporal dementia (FTD; rare), a combination of ALS and FTD, and atypical neurologic phenotypes (very rare)."

The GeneReviews chapter for this subtype, establishing that TARDBP variants most commonly give pure ALS but span an ALS-FTD spectrum.

PMID:20301761 SUPPORT REVIEW SYNTHESIS Human clinical

"The diagnosis of TARDBP-ALS-FTD is established in a proband with suggestive findings and most commonly a heterozygous pathogenic (or likely pathogenic) variant in TARDBP identified by molecular genetic testing."

Records that the usual allelic state is heterozygous, which is the basis for calling this subtype autosomal dominant.

+ 1 more reference

ALS11 (FIG4, risk allele) MONDO:0012945

FIG4 hgnc:16873

ALS associated with heterozygous deleterious FIG4 alleles. FIG4 is the lipid phosphatase that regulates PI(3,5)P2 and whose mutations also cause the recessive peripheral-nerve disorder CMT4J, so the ALS association sits on a different part of the same gene's allelic spectrum.

Show evidence (3 references)

PMID:19118816 SUPPORT Human clinical

"We now describe nonsynonymous variants of FIG4 in 2% (9/473) of patients with amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS)."

Reports the frequency of FIG4 variants in an ALS and PLS series.

PMID:19118816 SUPPORT BACKGROUND Human clinical

"Mutations of the lipid phosphatase FIG4 that regulates PI(3,5)P(2) are responsible for the recessive peripheral-nerve disorder CMT4J."

Source for FIG4's enzymatic identity and for the CMT4J relationship named in this subtype's description.

PMID:19118816 SUPPORT Human clinical

"Heterozygosity for a deleterious allele of FIG4 appears to be a risk factor for ALS and PLS, extending the list of known ALS genes and increasing the clinical spectrum of FIG4-related diseases."

The authors' own framing as a risk factor, which is the basis for the risk-rather-than-causative grading recorded above.

ALS12 (OPTN) MONDO:0013264

OPTN hgnc:17142

ALS from optineurin mutations, reported in both homozygous loss-of-function and heterozygous missense forms. The heterozygous E478G change falls in the ubiquitin-binding domain and abolishes optineurin's inhibition of NF-kappaB activation. OPTN is bound to this entry's Impaired Autophagy node alongside TBK1, VCP and SQSTM1.

Show evidence (2 references)

PMID:20428114 SUPPORT Human clinical

"We found three types of mutation of OPTN: a homozygous deletion of exon 5, a homozygous Q398X nonsense mutation and a heterozygous E478G missense mutation within its ubiquitin-binding domain."

Establishes the OPTN gene-disease relationship and the allelic classes.

PMID:20428114 SUPPORT In vitro / ex vivo

"Analysis of cell transfection showed that the nonsense and missense mutations of OPTN abolished the inhibition of activation of nuclear factor kappa B (NF-kappaB), and the E478G mutation revealed a cytoplasmic distribution different from that of the wild type or a POAG mutation."

Transfection data behind the NF-kappaB statement in this subtype's description.

ALS15 (UBQLN2, X-linked dominant) MONDO:0010459

UBQLN2 hgnc:12509

X-linked dominant ALS and ALS with dementia from UBQLN2 mutations, spanning juvenile and adult onset. Ubiquilin 2 shuttles ubiquitinated substrates to the proteasome, and affected spinal cords carry ubiquilin 2 pathology.

Show evidence (2 references)

PMID:21857683 SUPPORT Human clinical

"Here we show that mutations in UBQLN2, which encodes the ubiquitin-like protein ubiquilin 2, cause dominantly inherited, chromosome-X-linked ALS and ALS/dementia."

Establishes the gene, the X-linked dominant mode, and the ALS/dementia phenotype of this subtype.

PMID:21857683 SUPPORT Human clinical

"We describe novel ubiquilin 2 pathology in the spinal cords of ALS cases and in the brains of ALS/dementia"

Source for the statement that affected spinal cords carry ubiquilin 2 pathology.

ALS18 (PFN1, autosomal dominant) MONDO:0013891

PFN1 hgnc:8881

Familial ALS from mutations in profilin 1, which converts monomeric to filamentous actin. Mutant profilin forms ubiquitinated insoluble aggregates that often contain TDP-43, and motor neurons expressing it have smaller growth cones with a reduced F/G-actin ratio.

Show evidence (2 references)

PMID:22801503 SUPPORT Human clinical

"Here we show that mutations within the profilin 1 (PFN1) gene can cause FALS."

Establishes the PFN1 gene-disease relationship in familial ALS.

PMID:22801503 SUPPORT In vitro / ex vivo

"Cells expressing PFN1 mutants contain ubiquitinated, insoluble aggregates that in many cases contain the ALS-associated protein TDP-43."

Source for the aggregate and TDP-43 statements in this subtype's description.

ALS19 (ERBB4, autosomal dominant) MONDO:0014223

ERBB4 hgnc:3432

Late-onset autosomal dominant ALS with incomplete penetrance from ERBB4 mutations that reduce ErbB4 autophosphorylation in response to neuregulin-1. The reported clinical picture is combined upper and lower motor neuron involvement without obvious cognitive dysfunction and relatively slow progression.

Show evidence (2 references)

PMID:24119685 SUPPORT In vitro / ex vivo

"Functional analysis revealed that these mutations led to a reduced autophosphorylation of ErbB4 upon neuregulin-1 (NRG-1) stimulation."

Establishes the signalling lesion this subtype describes.

PMID:24119685 SUPPORT Human clinical

"Clinical presentations of the individuals with mutations were characterized by the involvement of both upper and lower motor neurons, a lack of obvious cognitive dysfunction, and relatively slow progression."

Source for the clinical description of this subtype.

ALS20 (HNRNPA1) MONDO:0014181

HNRNPA1 hgnc:5031

ALS from mutations in the prion-like domain of hnRNPA1. The same class of lesion in hnRNPA1 and its paralogue hnRNPA2B1 produces multisystem proteinopathy affecting muscle, brain, motor neuron and bone, of which familial ALS is one presentation.

Show evidence (1 reference)

PMID:23455423 SUPPORT Human clinical

"Here we define pathogenic mutations in PrLDs of heterogeneous nuclear ribonucleoproteins (hnRNPs) A2B1 and A1 in families with inherited degeneration affecting muscle, brain, motor neuron and bone, and in one case of familial amyotrophic lateral sclerosis."

Establishes the prion-like-domain lesion and records that the familial ALS presentation rested on a single case in this report.

ALS21 (MATR3) MONDO:0011632

MATR3 hgnc:6912

Familial ALS from MATR3 mutations. Matrin 3 is an RNA- and DNA-binding protein that interacts with TDP-43, and MATR3 pathology is seen in ALS spinal cords with and without MATR3 mutations, which places this subtype inside the RNA processing axis rather than beside it.

Show evidence (2 references)

PMID:24686783 SUPPORT Human clinical

"Using exome sequencing, we identified mutations in MATR3 in ALS kindreds."

Establishes the MATR3 gene-disease relationship.

PMID:24686783 SUPPORT Human clinical

"We also observed MATR3 pathology in ALS-affected spinal cords with and without MATR3 mutations."

Source for the statement that MATR3 pathology is not confined to MATR3 mutation carriers.

ALS23 (ANXA11) MONDO:0027694

ANXA11 hgnc:535

ALS from mutations in annexin A11, a vesicular trafficking protein. The recurrent p.D40G allele was absent from 70,000 control exomes, segregated in two kindreds, and carriers shared a founder haplotype; annexin A11-positive aggregates are present in spinal cord motor neurons of a carrier.

Show evidence (4 references)

PMID:28469040 SUPPORT Human clinical

"We screened 751 familial ALS patient whole-exome sequences and identified six mutations including p.D40G in the ANXA11 gene in 13 individuals."

Establishes the ANXA11 gene-disease relationship and the cohort it was found in.

PMID:28469040 SUPPORT Human clinical

"The p.D40G mutation was absent from 70,000 control whole-exome sequences."

Source for the control-absence figure quoted in this subtype's description.

PMID:28469040 SUPPORT Human clinical

"This mutation segregated with disease in two kindreds and was present in another two unrelated cases (P = 0.0102), and all mutation carriers shared a common founder haplotype."

Source for the segregation and founder-haplotype statements above.

+ 1 more reference

ALS26 (TIA1, with or without frontotemporal dementia; contested) MONDO:0030885

TIA1 hgnc:11802

ALS with or without frontotemporal dementia attributed to mutations in the low-complexity domain of TIA1, which increase the protein's propensity to phase-separate and leave non-dynamic stress granules containing TDP-43. The gene-disease relationship is contested: the Project MinE consortium holds that the published pedigree and burden analysis do not establish causality without replication.

Show evidence (3 references)

PMID:28817800 SUPPORT Human clinical

"Here we studied a novel ALS/FTD family and identified the P362L mutation in the low-complexity domain (LCD) of T cell-restricted intracellular antigen-1 (TIA1)."

The original report proposing TIA1 as an ALS/FTD gene.

PMID:28817800 SUPPORT In vitro / ex vivo

"In live cells, TIA1 mutations delayed stress granule (SG) disassembly and promoted the accumulation of non-dynamic SGs that harbored TDP-43."

Source for the stress granule mechanism described for this subtype.

PMID:29235362 REFUTE Human clinical

"Because of this, without a replication effort, we hold that rare TIA1 mutations cannot be regarded as causal in ALS, and that it is premature to include this gene in diagnostic panels for ALS and FTD."

The Project MinE consortium's published challenge to TIA1 causality, which is why this subtype is recorded as contested rather than established.

ALS28 (LRP12 CGG repeat expansion; not replicated outside Asian ancestry) MONDO:0957538

LRP12 hgnc:31708

ALS attributed to CGG repeat expansions of 61-100 units in LRP12, reported in five families and two simplex individuals. Longer expansions of 100-200 units in the same repeat cause oculopharyngodistal myopathy type 1, so the claim is that repeat length switches the phenotype. A whole-genome screen of European ALS patients and controls found no expanded alleles at all.

Show evidence (3 references)

PMID:37339631 SUPPORT Human clinical

"We identify CGG repeat expansion in LRP12 in five families and two simplex individuals."

The primary report of LRP12 repeat expansions in ALS.

PMID:37339631 SUPPORT Human clinical

"These ALS individuals (LRP12-ALS) have 61-100 repeats, which contrasts with most OPDM individuals with repeat expansion in LRP12 (LRP12-OPDM), who have 100-200 repeats."

Source for the repeat-length ranges given in this subtype's description.

PMID:38726482 REFUTE Human clinical

"All individuals had LRP12 CGG repeat lengths within the normal range of 3-25 units."

Screening 608 sporadic ALS patients, 35 familial probands and 4,703 controls of European ancestry found no expansion, which is the non-replication this subtype records.

FTDALS1 (C9orf72 GGGGCC repeat expansion) MONDO:0007105

C9orf72 hgnc:28337

The chromosome 9p-linked FTD/ALS locus, caused by a noncoding GGGGCC hexanucleotide repeat expansion in C9orf72 rather than by a coding lesion. In European populations it is the commonest genetic cause of both familial ALS and familial FTD. It is the largest of several shared causes, not the only one: TBK1, CCNF and VCP are likewise numbered as FTD and/or ALS loci in the rows below, and TARDBP and UBQLN2 also span ALS and dementia. The ranking does not hold everywhere either: in Asian populations SOD1 is the commonest ALS gene and C9orf72 expansions are comparatively rare.

Show evidence (4 references)

PMID:21944778 SUPPORT Human clinical

"Here, we report an expansion of a noncoding GGGGCC hexanucleotide repeat in the gene C9ORF72 that is strongly associated with disease in a large FTD/ALS kindred, previously reported to be conclusively linked to chromosome 9p."

Identifies the noncoding repeat expansion at the chromosome 9p FTD/ALS locus that MONDO:0007105 denotes.

PMID:28057713 SUPPORT Human clinical

"In European populations, the most common mutations were the C9orf72 repeat expansions (FALS 33.7%, SALS 5.1%), followed by SOD1 (FALS 14.8%, SALS 1.2%), TARDBP (FALS 4.2%, SALS 0.8%) and FUS mutations (FALS 2.8%, SALS 0.3%), while in Asian populations the most common mutations were SOD1..."

Source for both halves of the ranking claim above: C9orf72 leads in European familial ALS, and does not in Asian populations.

PMID:25577942 SUPPORT REVIEW SYNTHESIS Human clinical

"The diagnosis of C9orf72-FTD/ALS is established in a proband with suggestive findings and a heterozygous abnormal G4C2 (GGGGCC) hexanucleotide repeat expansion in C9orf72 identified by molecular genetic testing."

The GeneReviews chapter for this subtype, stating the diagnostic lesion.

+ 1 more reference

FTDALS4 (TBK1 haploinsufficiency) MONDO:0014641

TBK1 hgnc:11584

ALS and frontotemporal dementia from loss-of-function TBK1 alleles acting by haploinsufficiency. Some coiled-coil-domain mutants instead lose the interaction with optineurin, tying this subtype to ALS12 at the protein level. The enrichment was specific to familial cases and was not seen in a sporadic screen.

Show evidence (3 references)

PMID:25803835 SUPPORT Human clinical

"Gene-based rare variant analysis identified an exome-wide significant enrichment of eight loss-of-function (LoF) mutations in TBK1 (encoding TANK-binding kinase 1) in 13 fALS pedigrees."

Establishes the TBK1 loss-of-function enrichment in familial ALS pedigrees.

PMID:25803835 SUPPORT Human clinical

"No enrichment of LoF mutations was observed in a targeted mutation screen of 1,010 sporadic ALS and 650 additional control individuals."

Source for restricting the TBK1 enrichment claim to familial ALS.

PMID:25803835 SUPPORT In vitro / ex vivo

"In vitro experiments confirmed the loss of expression of TBK1 LoF mutant alleles, or loss of interaction of the C-terminal TBK1 coiled-coil domain (CCD2) mutants with the TBK1 adaptor protein optineurin, which has been shown to be involved in ALS pathogenesis."

Source for the two mutant classes described above, including the coiled-coil-domain mutants that lose the optineurin interaction.

FTDALS5 (CCNF / cyclin F) MONDO:0030875

CCNF hgnc:1591

ALS and frontotemporal dementia from mutations in CCNF, which encodes cyclin F, the substrate-recognition component of an SCF E3 ubiquitin-ligase complex. Mutant cyclin F causes abnormal ubiquitination and accumulation of ubiquitinated proteins including TDP-43.

Show evidence (2 references)

PMID:27080313 SUPPORT Human clinical

"Here we use genome-wide linkage analysis in a large ALS/FTD kindred to identify a novel disease locus on chromosome 16p13.3. Whole-exome sequencing identified a CCNF missense mutation at this locus."

Establishes the CCNF gene-disease relationship by linkage plus exome sequencing in an ALS/FTD kindred.

PMID:27080313 SUPPORT In vitro / ex vivo

"Expression of mutant CCNF in neuronal cells caused abnormal ubiquitination and accumulation of ubiquitinated proteins, including TDP-43 and a SCF(Cyclin F) substrate."

Source for the ubiquitination mechanism described for this subtype.

FTDALS6 (VCP, autosomal dominant) MONDO:0013501

VCP hgnc:12666

Autosomal dominant ALS from VCP mutations. The same gene causes inclusion body myopathy with Paget disease of bone and frontotemporal dementia, and the ALS presentation was recognized as an extension of that phenotype rather than as a separate genetic entity.

Show evidence (3 references)

PMID:21145000 SUPPORT Human clinical

"Using exome sequencing, we identified a p.R191Q amino acid change in the valosin-containing protein (VCP) gene in an Italian family with autosomal dominantly inherited amyotrophic lateral sclerosis (ALS)."

Establishes the VCP gene-disease relationship in autosomal dominant familial ALS.

PMID:21145000 SUPPORT Human clinical

"Screening of VCP in a cohort of 210 familial ALS cases and 78 autopsy-proven ALS cases identified four additional mutations including a p.R155H mutation in a pathologically proven case of ALS."

Replication of VCP mutations in a larger familial ALS cohort.

PMID:21145000 SUPPORT BACKGROUND Human clinical

"Mutations in VCP have previously been identified in families with Inclusion Body Myopathy, Paget disease, and Frontotemporal Dementia (IBMPFD)."

Source for the statement that the same gene causes IBMPFD, curated as a separate entry.

◈

Mechanistic Hypotheses

Canonical Motor Neuron Proteostatic Failure Model

canonical_motor_neuron_proteostatic_failure_model CANONICAL

Evidence balance 4 support

Progressive upper and lower motor neuron degeneration in ALS is the convergent endpoint of multiple genetic and sporadic insults that ultimately cause proteostatic failure. Key drivers include cytoplasmic mislocalization and aggregation of TDP-43 (in >97% of cases), C9orf72 hexanucleotide repeat expansion–derived dipeptide repeats and RNA foci, SOD1 misfolding, FUS/EWSR1 phase-separation defects, impaired autophagy, mitochondrial dysfunction, axonal transport failure, and neuroinflammation. Selective vulnerability of cortical layer-5 Betz cells and spinal alpha motor neurons leads to progressive muscle denervation, weakness, atrophy, and ultimately respiratory failure. Antisense-oligonucleotide therapy targeting SOD1 (tofersen) provides the strongest interventional validation of the SOD1 genetic-pathogenetic axis of this canonical multi-hit model, although that validation rests on target engagement and biomarker lowering rather than on a positive randomized clinical endpoint. The C9orf72 ASO program (BIIB078) was discontinued after a Phase 1 study that showed neither neurofilament reduction nor clinical benefit, indicating that lowering sense-strand repeat RNA alone is insufficient; that single negative program does not by itself establish which of the competing C9orf72 mechanisms — antisense-strand RNA toxicity, dipeptide-repeat proteins, or haploinsufficiency — dominates.

Retained as CANONICAL. The 2026 openscientist hypothesis-search report (kb/hypotheses/Amyotrophic_Lateral_Sclerosis/canonical_motor_neuron_proteostatic_failure_model) confirms convergent proteostatic failure as the unifying ALS mechanism: TDP-43 proteinopathy in ~97% of cases, SOD1 misfolding, C9orf72 RNA foci and DPRs, FUS phase-separation defects, impaired autophagy, mitochondrial dysfunction, axonal transport failure, and neuroinflammation all converge on motor-neuron degeneration. Tofersen (SOD1 ASO) approval provides the strongest causal validation of the genetic-pathogenetic axes. Four qualifications: (1) the C9orf72-ASO program (BIIB078; Phase 1 discontinued) showed insufficient clinical efficacy — lowering sense-strand repeat RNA does not consistently translate to motor preservation. The 2026 openscientist report reads that failure as evidence that DPR-mediated toxicity dominates; the assessment (assessments/openscientist-assessment-by-codex.yaml, claim c9orf72-failure-mechanism) rejects that inference, since one ASO at one dose range and exposure period cannot separate incomplete target engagement, treatment timing, antisense-strand transcripts, DPR toxicity, haploinsufficiency, or persistent TDP-43 pathology. (2) The "proteostatic failure" framing remains a descriptive convergence rather than a single mechanistic primer — different genetic ALS subtypes follow different upstream paths. (3) Sporadic ALS (~90%) requires environmental/epigenetic modifiers (BMAA, head trauma, aging) that the canonical model does not specify. (4) The tofersen evidence is target-engagement- and biomarker-led: VALOR's prespecified 28-week ALSFRS-R primary endpoint and its clinical secondary endpoints did not separate from placebo, and the longer-term early-start versus delayed-start advantage comes from an open-label extension with substantial attrition, so it is not a blinded randomized efficacy comparison.

Deep research

OpenScientist citations 35 citations 2026-05-23T16:01:09.200504

Show evidence (4 references)

PMID:38891021 SUPPORT Human clinical

"upper and lower motor neurons in the brain and spinal cord progressively degenerate"

Canonical mechanism review used as the seed reference for the hypothesis-search deep-research run.

PMID:34873335 SUPPORT Human clinical

"The combination of all ALS-associated signals reveals a role for perturbations in vesicle-mediated transport and autophagy and provides evidence for cell-autonomous disease initiation in glutamatergic neurons."

Cross-ancestry GWAS of 29,612 patients supplying the human-genetic basis for the convergence framing in this hypothesis: locus-specific genetic architectures nonetheless aggregate onto vesicle-mediated transport and autophagy in a defined neuronal population. Note what it does and does not say — it identifies converging pathways and a cell-autonomous initiation site, not a single ordered proteostatic chain shared by all ALS, which is why qualification (2) in this hypothesis's notes stands.

PMID:39986312 SUPPORT Human clinical

"Clinical trials using antisense oligonucleotides to target the GGGGCC repeat RNA have not been successful, potentially because they only target a single gain-of-function mechanism."

Lancet Neurology 2025 review confirms that C9orf72 ASO trials did not achieve clinical benefit, directly qualifying the canonical model's genetic-pathogenetic-axis interventional validation. The hexanucleotide repeat expansion drives a complex interplay of loss-of-function and gain-of-function pathology that single-target therapies do not address.

+ 1 more reference

TDP-43 RNA Dysregulation and Motor-Neuron Selective Vulnerability Model

tdp43_rna_dysregulation_selective_vulnerability_model EMERGING

Evidence balance 4 support

This focused model treats ALS-associated TDP-43 pathology as a coupled nuclear loss-of-function and cytoplasmic gain-of-function process. Nuclear depletion of TDP-43 removes cryptic-exon repression and other RNA-processing controls in vulnerable motor neurons, producing mis-spliced or unstable transcripts such as STMN2 and UNC13A that impair axonal repair, synaptic function, and proteostasis. Cytoplasmic TDP-43 aggregation may amplify injury through stress-granule and proteostatic dysfunction and may contribute to propagation, but the unresolved causal step is which RNA target, aggregate species, or non-cell-autonomous signal converts TDP-43 dysfunction into selective motor-neuron death.

The 2026 OpenScientist hypothesis report (kb/hypotheses/Amyotrophic_Lateral_Sclerosis/tdp43_rna_dysregulation_selective_vulnerability_model) judged the TDP-43 loss-of-function/cryptic-exon arm to be the strongest, best-supported part of this hypothesis, while keeping the integrated model of RNA loss, cytoplasmic gain-of-function, selective vulnerability, and propagation as emerging because the rate-limiting RNA target, aggregate species, upstream trigger hierarchy, and spread mechanism remain unresolved. Additional report-suggested PMIDs were retained as curation leads and not added here without independent PubMed/cache verification.

Pathograph links

TDP-43 Proteinopathy -> TDP-43-Dependent Cryptic Exon Misprocessing DIRECT Nuclear depletion of TDP-43 removes repression of cryptic exons and cryptic splice-polyadenylation events in disease-relevant transcripts.

TDP-43-Dependent Cryptic Exon Misprocessing -> Axonal Transport Dysfunction INDIRECT KNOWN INTERMEDIATES STMN2 loss and related RNA misprocessing can impair axonal outgrowth, axon regeneration, and lysosome trafficking in human motor-neuron models. Intermediates: STMN2 depletion; impaired axonal regeneration; stathmin-2-dependent lysosome trafficking defects

TDP-43-Dependent Cryptic Exon Misprocessing -> Motor Neuron Degeneration INDIRECT KNOWN INTERMEDIATES Cryptic-exon misprocessing is modeled as an indirect, target-specific bridge from TDP-43 nuclear loss to motor-neuron degeneration through STMN2-dependent axonal repair defects, UNC13A-dependent synaptic defects, and other transcript-specific losses. Sufficiency of any single target is not established: mouse Stmn2 knockout reproduces the distal, fast-fatigable neuromuscular-junction denervation seen in ALS but does not produce axon or motoneuron degeneration, so this edge should be read as target-specific support for the distal arm rather than as a demonstrated route to motor-neuron death. Intermediates: STMN2 depletion and impaired axonal repair; UNC13A nonsense-mediated decay and synaptic dysfunction; unresolved additional TDP-43 RNA targets

Deep research

OpenScientist citations 37 citations 2026-06-03T09:22:30.171915

Show evidence (4 references)

PMID:32799899 SUPPORT Other

"Research has focused on the formation and consequences of cytosolic protein aggregates as drivers of ALS pathology through both gain- and loss-of-function mechanisms."

Review-level synthesis supports modeling TDP-43 pathology as both nuclear loss-of-function and cytoplasmic gain-of-function rather than as aggregation alone.

PMID:26250685 SUPPORT Human clinical

"repression of cryptic exons was impaired in ALS-FTD cases, suggesting that this splicing defect could potentially underlie TDP-43 proteinopathy."

Human ALS-FTD tissue evidence links loss of TDP-43 cryptic-exon repression to TDP-43 proteinopathy.

PMID:30643292 SUPPORT In vitro / ex vivo

"STMN2 loss upon reduced TDP-43 function was due to altered splicing, which is functionally important, as we show STMN2 is necessary for normal axonal outgrowth and regeneration."

Human motor-neuron experiments identify STMN2 mis-splicing and loss as a functional downstream RNA target that impairs axonal growth and repair.

+ 1 more reference

Discussions and Knowledge Gaps

Which TDP-43-dependent RNA-processing defect, cytoplasmic aggregate species, or non-cell-autonomous signal explains why upper and lower motor neurons are selectively vulnerable in ALS, and how does this mechanism relate to clinical propagation across neuroanatomical regions?

KNOWLEDGE GAP OPEN gap_als_tdp43_selective_vulnerability_and_spread

Attached to

mechanistic_hypotheses#tdp43_rna_dysregulation_selective_vulnerability_model pathophysiology#TDP-43 Proteinopathy pathophysiology#TDP-43-Dependent Cryptic Exon Misprocessing pathophysiology#Motor Neuron Degeneration

STMN2 and UNC13A make TDP-43 loss-of-function concrete at the RNA target level, but they do not yet explain why particular motor-neuron classes degenerate while other neurons or glia with TDP-43 pathology can be less affected. Separating nuclear RNA loss-of-function from cytoplasmic gain-of-function and spread-like propagation is required to decide whether therapies should prioritize restoring individual transcripts, correcting TDP-43 localization, clearing aggregate species, or targeting glial and circuit-level amplifiers.

Proposed experiments

Isogenic human motor-neuron TDP-43 target rescue and spatial validation panel

isogenic stem-cell perturbation and spatial transcriptomics experiment

exp_als_isogenic_motor_neuron_tdp43_target_rescue_panel

Compare isogenic human iPSC-derived upper- and lower-motor-neuron-like cultures with controlled nuclear TDP-43 depletion, TDP-43 cytoplasmic mislocalization, and patient-derived TDP-43 aggregate seeding. Rescue STMN2, UNC13A, and candidate transcript targets singly and in combination, then benchmark survival, axonal regeneration, synaptic function, lysosome trafficking, and spatial transcriptomic signatures against ALS postmortem motor cortex and spinal cord.

Decision criterion

A causal RNA-processing target should rescue motor-neuron survival or axonal/synaptic function in TDP-43-deficient cells and show spatially concordant misprocessing in vulnerable human ALS motor-neuron populations; failure of target rescue would shift priority toward aggregate-seeding, proteostatic, glial, or circuit-level propagation mechanisms.

Show evidence (4 references)

PMID:37999738 SUPPORT Other

"Despite extensive research, it remains unclear why some motor neurons are especially susceptible to the disease, while others are affected less or even spared."

Review explicitly frames motor-neuron selective vulnerability as an unresolved ALS mechanism.

PMID:32799899 SUPPORT Other

"Yet in ALS, motor neurons selectively degenerate suggesting that the presence of TDP-43 aggregates may not necessarily drive cell-death."

TDP-43 review highlights the unresolved gap between aggregate presence and selective motor-neuron death.

PMID:35767949 SUPPORT Model organism

"Constitutive STMN2 loss results in early-onset sensory and motor neuropathy featuring impaired motor behavior and dramatic distal neuromuscular junction (NMJ) denervation of fast-fatigable motor units, which are selectively vulnerable in ALS, without axon or motoneuron degeneration."

Makes the gap concrete for the best-characterized TDP-43 RNA target. Stmn2 knockout reproduces exactly the population selectivity the gap asks about — the fast-fatigable motor units — yet stops short of axon or motoneuron degeneration, so the step from a selectively affected motor unit to motor-neuron death is still unaccounted for.

+ 1 more reference

What upstream cellular event triggers preferential TDP-43 nuclear clearance and cytoplasmic mislocalization in motor neurons compared with other cell types that also express TDP-43?

KNOWLEDGE GAP OPEN gap_als_tdp43_mislocalization_upstream_trigger

Attached to

pathophysiology#TDP-43 Proteinopathy mechanistic_hypotheses#tdp43_rna_dysregulation_selective_vulnerability_model

TDP-43 is a ubiquitously expressed nuclear RNA-binding protein, yet in ALS it mislocalizes and aggregates preferentially in motor neurons. The NLS and NES sequences of TDP-43 are not motor-neuron specific, and cellular stressors such as oxidative stress, osmotic stress, or heat shock can induce phase-separated TDP-43 cytoplasmic structures in many cell types. What makes motor neurons uniquely susceptible to irreversible TDP-43 mislocalization — whether through long-axon-specific transport burdens, particular importin isoform expression, differential proteostatic capacity, or a specific upstream metabolic vulnerability — is not established. Identifying this upstream trigger is required to explain why ALS is a motor-neuron disease rather than a pan-neuronal or pan-cellular proteinopathy, and to determine the earliest actionable intervention point.

Show evidence (2 references)

PMID:32799899 SUPPORT Other

"The exact mechanisms mediating the formation of TDP-43 aggregates remain elusive."

Review acknowledges that the upstream trigger for TDP-43 aggregation and mislocalization is unresolved, supporting this as an open knowledge gap distinct from the downstream RNA-processing defects.

PMID:37999738 SUPPORT Other

"Despite extensive research, it remains unclear why some motor neurons are especially susceptible to the disease, while others are affected less or even spared."

Selective vulnerability review frames the motor-neuron-preferential degeneration as unresolved, implicating upstream cell-type-specific factors in TDP-43 mislocalization as a key open question.

Does phosphorylated TDP-43 pathology spread through the ALS motor system by prion-like protein seeding, by trans-synaptic or retrograde axonal signaling, or by secondary neuroinflammatory relay — and can these mechanisms be distinguished experimentally?

KNOWLEDGE GAP OPEN gap_als_ptdp43_propagation_mechanism

Attached to

pathophysiology#TDP-43 Proteinopathy pathophysiology#Motor Neuron Degeneration mechanistic_hypotheses#tdp43_rna_dysregulation_selective_vulnerability_model

Cross-sectional postmortem staging studies show that pTDP-43 pathology progresses through the ALS motor system in a stereotyped, anatomically sequential pattern analogous to Braak staging in Parkinson disease and Alzheimer disease, consistent with a propagating process. However, the cellular mechanism of spread is not established: whether pTDP-43 propagates by direct cell-to-cell protein seeding (prion-like templating), by trans-synaptic or retrograde axonal transport of a pathological signal, by secondary glial or neuroinflammatory relay, or by some combination of these mechanisms remains unresolved. Understanding the propagation mechanism has direct therapeutic implications — a seeding model prioritizes aggregate clearance or passive immunotherapy at early disease stages, while an inflammatory-relay model prioritizes anti-neuroinflammatory intervention at transitional anatomical boundaries.

Show evidence (2 references)

PMID:23686809 SUPPORT Human clinical

"pTDP-43 pathology in ALS possibly disseminates in a sequential pattern that permits recognition of 4 neuropathological stages consistent with the hypothesis that pTDP-43 pathology is propagated along axonal pathways."

Postmortem staging data in 76 ALS cases support sequential anatomical spread of pTDP-43 pathology, motivating the mechanistic question of how this propagation is achieved without establishing the cellular mechanism.

PMID:23686809 SUPPORT Human clinical

"Whereas the cell-to-cell transmission of pTDP-43 has not been demonstrated conclusively in vivo, a recently discovered C-terminal prion-like domain has been implicated in the aggregation of pTDP-43 in cultured cells."

In vitro prion-like domain evidence is consistent with protein seeding but does not establish in vivo cell-to-cell transmission, leaving the propagation mechanism open.

Does the lower-motor-neuron-only phenotype of equine motor neuron disease (EMND) preclude its use as a model for classic ALS, which requires both upper and lower motor neuron degeneration?

HUMAN MODEL MISMATCH OPEN mismatch_emnd_lmn_only_phenotype

Attached to

animal_models#Horse

Classic ALS is defined by combined upper motor neuron (UMN) and lower motor neuron (LMN) degeneration. Equine motor neuron disease (EMND) involves predominantly or exclusively lower motor neurons, with no established corticospinal tract involvement, making it a phenotypically closer analog to progressive muscular atrophy (LMN-only ALS variant) than to classic ALS. This reduces the direct translational value of EMND as an ALS model, though the shared oxidative stress mechanism and spinal motor neuron vulnerability retain biological relevance for the LMN degenerative arm of the disease.

Proposed experiments

Corticospinal tract histopathological survey in EMND horses

post-mortem neuropathological study

exp_emnd_umn_tract_assessment

Systematic immunohistochemical and histopathological assessment of corticospinal tracts and motor cortex in post-mortem EMND horses to determine whether subclinical UMN pathology is present but overlooked in existing case series, or is genuinely absent.

Decision criterion

Detection of UMN pathology would support EMND as a true ALS analog; confirmed absence would classify EMND as a selective LMN disease and redirect its value to studies of the ALS LMN degenerative arm only.

Mutant TDP-43 knock-in mice develop motor axon degeneration and motor-neuron death with neither nuclear TDP-43 clearance nor TDP-43 aggregates. Does that mean cytoplasmic aggregation and nuclear depletion are also dispensable in human ALS, where both are near-universal findings?

HUMAN MODEL MISMATCH OPEN mismatch_tdp43_aggregation_dispensability

Attached to

pathophysiology#TDP-43 Proteinopathy pathophysiology#Motor Neuron Degeneration mechanistic_hypotheses#canonical_motor_neuron_proteostatic_failure_model

TDP-43 Q331K and M337V mice expressed at endogenous levels develop age-dependent, mutant-dependent motor axon degeneration and lower motor neuron death without loss of nuclear TDP-43, without aggregates, and without insoluble TDP-43, while showing both loss and gain of splicing function at selected RNA targets. Taken literally, that dissociates degeneration from the two features this entry treats as the defining lesion of TDP-43 proteinopathy. The mismatch is that the finding is a sufficiency result in an engineered mutant model, whereas ~97% of human ALS — the great majority of it sporadic and not TARDBP-mutant — does show nuclear clearance and phosphorylated cytoplasmic inclusions. The model therefore establishes that an ALS-linked mutant can kill motor neurons through altered splicing alone; it does not establish the temporal position, toxicity, or possible protective role of aggregates in sporadic human disease, and it should not be read as demonstrating that human TDP-43 aggregation is merely a late-stage marker. Resolving this determines whether therapy should target aggregate clearance, TDP-43 localization, or the RNA-processing changes directly.

Proposed experiments

Aggregation- and localization-separated TDP-43 toxicity in human motor neurons

isogenic human iPSC motor-neuron structure-function dissociation experiment

exp_als_aggregation_independent_tdp43_toxicity

In isogenic human iPSC-derived motor neurons, express TDP-43 variants engineered to separate the three features: aggregation-incompetent mutants that retain altered splicing, nuclear-retained mutants, and mutants that aggregate without changing splicing. Compare survival, axonal integrity and cryptic-splicing burden across arms, and benchmark the resulting splicing signatures against nuclear-cleared versus nuclear-preserved motor neurons sampled from sporadic ALS postmortem tissue.

Decision criterion

Motor-neuron death in the aggregation-incompetent arm, with a splicing signature matching nuclear-cleared human ALS motor neurons, would extend the mouse result to human cells and argue that RNA misprocessing rather than aggregation is the actionable lesion; survival in that arm together with death in the aggregating arm would confine the mouse finding to mutant-driven disease and keep aggregate species as a human therapeutic target.

Show evidence (2 references)

PMID:23382207 SUPPORT Model organism

"Thus, adult-onset motor neuron disease does not require aggregation or loss of nuclear TDP-43, with ALS-linked mutants producing loss and gain of splicing function of selected RNA targets at an early disease stage."

The mouse result that creates the mismatch. It shows that neither aggregation nor nuclear TDP-43 loss is required for adult-onset motor neuron disease in this engineered model, which is what makes the translational status of the near-universal human aggregation and nuclear clearance an open question rather than a settled one.

PMID:32799899 SUPPORT Human clinical

"TDP-43 was identified as a primary component of ubiquitinated and hyper-phosphorylated cytosolic aggregates observed from post-mortem tissue of patients with ALS"

The human side of the mismatch: postmortem ALS tissue does show ubiquitinated, hyperphosphorylated cytoplasmic TDP-43 aggregates, so the model's dispensability result conflicts with what is near-universally observed in patients rather than simply extending it.

Can chlorpromazine, or another phenothiazine antipsychotic, be repurposed as a disease-modifying ALS therapy on the strength of lysosomal TPC2 agonism, TFEB-driven autophagy induction and enhanced TDP-43 aggregate clearance — or does the dopaminergic pharmacology that defines the class cancel any proteostatic benefit at exposures a person with ALS could tolerate?

EMERGING HYPOTHESIS OPEN hyp_als_phenothiazine_autophagy_repurposing

Attached to

pathophysiology#Impaired Autophagy pathophysiology#TDP-43 Proteinopathy pathophysiology#Motor Neuron Degeneration treatments#

Three independent lines converge on the phenothiazine scaffold as a proteostasis-directed ALS lead. An unbiased neuronal autophagy-inducer screen returned two phenothiazine antipsychotics as its top hits and showed that autophagy induction accelerates TDP-43 turnover and improves survival in human stem-cell-derived neurons; thioridazine cleared TDP-43 aggregates, restored TDP-43 splicing function and rescued locomotion in Drosophila; and chlorpromazine itself was shown to open the lysosomal TPC2 channel in NSC-34 motor neurons, driving Ca2+-dependent TFEB translocation and protecting against the ALS/PDC neurotoxin L-BMAA, with TPC2 knockdown reverting the protection. Each of those is a different route to the same node this discussion attaches to, and none has been tested in a mammalian ALS model. The hypothesis is nevertheless not simply untested — it is tested by proxy, and the proxies failed. Methylene blue shares the tricyclic phenothiazine-type core, reduced TDP-43 aggregates in cells, and then conferred no benefit in SOD1-G93A or TDP-43-G348C mice. Pimozide, a neuroleptic selected by the same simple-organism screening logic, reached a short randomized ALS trial with apparent target engagement at the neuromuscular junction, and chronic dosing then worsened motor performance in two ALS mouse models and shortened SOD1-G93A survival. Clozapine delayed decline at low dose and accelerated paralysis and death at high dose in the same model. So the open question is not whether phenothiazines induce autophagy in motor neurons — they do — but whether a therapeutic window exists between the concentration that engages TPC2/TFEB and the concentration at which D2 blockade produces rigidity, sedation and dysphagia in a population whose leading cause of death is respiratory and bulbar failure. The epidemiological premise that originally motivated neuroleptic repurposing in ALS — that ALS is strikingly rare among people with schizophrenia — should not be carried forward. It was a clinical impression, and the ALS/schizophrenia genetic correlation is positive (14.3%), predicting a modest increase rather than a decrease in comorbidity. A closer look at TPC2 itself narrows the hypothesis further, and not in its favour. TPC2's ion selectivity is set by which ligand opens it: a NAADP-mimetic evokes non-selective cation currents and robust Ca2+ signals, a PI(3,5)P2-mimetic evokes Na+-selective currents and weaker ones, and the two drive lysosomal pH and exocytosis in opposite directions. The chlorpromazine result sits squarely on the NAADP arm — the paper benchmarks the chlorpromazine-evoked current against NAADP and its mimetic TPC2-A1-N, and blocks it with trans-Ned-19. That is the arm with no in vivo efficacy precedent anywhere: the lysosomal-storage rescue that put TPC2 on the map used the PI(3,5)P2-mimetic TPC2-A1-P throughout, including in its MLIV mouse, and in LRRK2 Parkinson's models the beneficial agonist was one biased to reduce Ca2+ permeability, with TPC2 itself the pathogenic element. So the chain this hypothesis proposes runs through the one mode of the one channel for which no animal has yet been shown to benefit. Two consequences for the experiments below. First, the window study should read out the PI(3,5)P2-biased mode as well, because if substrate clearance in motor neurons tracks that mode instead, the useful compound is a biased TPC2 agonist and not an antipsychotic. Second, the obvious alternative of blocking TPC2 instead — which is neuroprotective in stroke and in LRRK2 models, and is the better-developed arm pharmacologically — carries a motor-neuron-specific liability that those indications do not: trans-Ned-19, the same antagonist, attenuates Ca2+ transients in zebrafish caudal primary motor neurons and inhibits their axon extension. In a motor-neuron disease the better-developed arm of TPC2 pharmacology acts against the arm of TPC2 biology that motor neurons demonstrably need. See kb/modules/lysosomal_substrate_accumulation.yaml (controversy_tpc2_direction_of_modulation) for the direction question in general.

Proposed experiments

Phenothiazine TPC2/TFEB engagement versus tolerated CNS exposure in ALS

pharmacodynamic-pharmacokinetic window study in iPSC motor neurons and mouse CNS

exp_als_phenothiazine_therapeutic_window_csf_exposure

Establish, for chlorpromazine and for the screen-derived phenothiazines fluphenazine and methotrimeprazine, the free concentration required in human iPSC-derived motor neurons to produce TPC2-dependent TFEB nuclear translocation and measurable TDP-43 clearance, then compare it against free CSF and spinal-cord concentrations achieved in wild-type and SOD1-G93A mice at doses below the threshold for hindlimb rigidity and catalepsy. Include a TPC2-null arm to confirm that clearance in motor neurons is channel-dependent rather than a general lysosomotropic effect of the cationic amphiphilic scaffold.

Decision criterion

A viable window requires the TFEB/TDP-43-clearance EC50 to sit below the free CNS concentration reached at a non-cataleptic dose, with at least a severalfold margin. If engagement demands concentrations only reached at doses producing extrapyramidal signs, the repurposing hypothesis should be abandoned for the marketed antipsychotics and redirected to TPC2 agonists without dopamine-receptor affinity.

Would support

pathophysiology#Impaired Autophagy

Would refute

pathophysiology#Impaired Autophagy

Supporting outcome

TPC2-dependent TFEB translocation and TDP-43 clearance at free concentrations several-fold below those producing catalepsy or hindlimb rigidity in mice.

Refuting outcome

Engagement only at concentrations at or above the motor-toxicity threshold, or clearance that persists in TPC2-null motor neurons and is therefore an off-target lysosomotropic effect.

Dose-ranging chlorpromazine survival study in TDP-43 and SOD1 ALS mice

dose-ranging survival study in two transgenic ALS mouse models

exp_als_chlorpromazine_dose_ranging_two_model_survival

Run chlorpromazine at a minimum of three doses spanning the window identified above in both TDP-43-A315T and SOD1-G93A mice, powered for survival and with prespecified neuromuscular-junction innervation, insoluble TDP-43, misfolded SOD1 and spinal-cord LC3-II/p62 endpoints. Two models and a dose range are both required: the pimozide study found opposite-signed effects from the short human trial, and the clozapine study found opposite-signed effects between low and high dose within one model, so a single-dose single-model result cannot settle this.

Decision criterion

Chlorpromazine should extend survival or preserve neuromuscular-junction innervation in at least one model at a dose whose autophagic target engagement is confirmed in the same spinal cords. Worsened motor performance, shortened survival, or increased insoluble TDP-43 or misfolded SOD1 at any dose — the pimozide result — closes the hypothesis for chlorpromazine.

Would support

pathophysiology#Motor Neuron Degeneration

Would refute

pathophysiology#Motor Neuron Degeneration

Supporting outcome

Survival extension or preserved neuromuscular-junction innervation at a dose with confirmed spinal-cord autophagy induction.

Refuting outcome

Worsened motor performance, shortened survival, or increased insoluble TDP-43 or misfolded SOD1 at any tested dose.

Show evidence (18 references)

PMID:40796055 SUPPORT In vitro / ex vivo

"Accordingly, TPC2 stimulation by both the drugs boosted autophagy, as revealed by the activation of autophagy initiators ULK and AMPK α and modification of LC3-II/p62(SQSTM1) ratio."

The only chlorpromazine-specific mechanistic result in a motor-neuron system, and the proximate reason this hypothesis is worth stating: it names a molecular target (TPC2) and an effector (autophagy, read out on ULK, AMPK and the LC3-II/p62 ratio) rather than asserting generic neuroprotection. The paper reports the intervening step as a chlorpromazine-evoked calcium rise driving TFEB nuclear translocation.

PMID:40796055 SUPPORT In vitro / ex vivo

"Notably, siTPC2 partially reverted CMI- and CPZ-induced neuroprotection as well as that produced by NAADP."

The knockdown arm is what distinguishes a target-mediated effect from the generic lysosomotropism every cationic amphiphilic drug shows, which is why the proposed window study keeps a TPC2-null arm. Note the authors report the reversion as partial, so some of the protection is not TPC2-attributable even here.

PMID:24974230 SUPPORT In vitro / ex vivo

"New compounds that stimulate autophagy improved TDP43 clearance and localization and enhanced survival in primary murine neurons and in human stem cell-derived neurons and astrocytes harboring mutant TDP43."

Establishes the general principle the hypothesis rests on — that inducing neuronal autophagy clears TDP-43 and improves survival in human stem-cell-derived neurons. The two top compounds from this screen were phenothiazine antipsychotics, so the scaffold was reached by unbiased screening rather than by analogy alone.

+ 15 more references

⚙

Pathophysiology

Motor Neuron Degeneration

Progressive death of upper motor neurons in the motor cortex and lower motor neurons in the brainstem and spinal cord leads to denervation of skeletal muscles. The loss of upper motor neurons causes spasticity and hyperreflexia, while lower motor neuron loss results in muscle weakness, atrophy, and fasciculations.

motor neuron CL:0000100

primary motor cortex UBERON:0001384

Animal models

Canine degenerative myelopathy (SOD1 E40K homozygous dog) Dog recapitulates Naturally occurring, adult-onset SOD1-associated degeneration of the spinal cord, with neuronal cytoplasmic SOD1-immunoreactive inclusions matching those of human SOD1-ALS.

Equine motor neuron disease (vitamin E-deficient horse) Horse partially recapitulates Adult-onset degeneration of lower motor neurons with denervation muscle pathology, arising spontaneously under chronic nutritional oxidative stress.

Show evidence (4 references)

ORPHA:803 SUPPORT

"A neurodegenerative disease characterized by progressive muscular paralysis reflecting degeneration of motor neurons in the primary motor cortex, corticospinal tracts, brainstem and spinal cord."

Orphanet definition confirms progressive motor neuron degeneration across cortex, brainstem, and spinal cord.

PMID:38521060 SUPPORT Human clinical

"we identify known and previously unidentified vulnerable populations in cortical layer 5 and show that ALS- and FTLD-implicated motor and spindle neurons possess a virtually indistinguishable molecular identity."

Single-cell atlas of human ALS motor cortex identifies vulnerable neuronal populations in cortical layer 5 (including ALS-implicated motor/spindle neurons), supporting selective cortical motor-neuron vulnerability.

PMID:38891021 SUPPORT

"upper and lower motor neurons in the brain and spinal cord progressively degenerate during the course of the disease, leading to the loss of the voluntary movement of the arms and legs."

Review summarizes canonical ALS pathology of progressive upper and lower motor neuron degeneration causing loss of voluntary movement.

+ 1 more reference

Nuclear Pore Complex Dysfunction

Selective loss of nuclear pore complex (NPC) components, particularly the scaffold proteins NUP107 and NUP93 and FG-repeat-containing components, is a consistent feature across ALS postmortem spinal cord, SOD1^G93A and TDP-43 mutant mouse models, and human cell systems. CRISPR-mediated NUP107 depletion is sufficient to trigger cytoplasmic TDP-43 mislocalization, increased TDP-43 phosphorylation, and autophagy dysfunction, placing NPC dysfunction upstream of TDP-43 proteinopathy in the canonical proteostatic failure cascade. Oxidative stress exacerbates NPC subunit mislocalization, creating a redox-sensitive vulnerability that amplifies the downstream TDP-43 aggregation phenotype.

motor neuron CL:0000100

NUP50 hgnc:8065 GLE1 hgnc:4315

nucleocytoplasmic transport GO:0006913 ↓ DECREASED

Downstream

TDP-43 Proteinopathy NPC scaffold loss permits cytoplasmic TDP-43 mislocalization, hyperphosphorylation, and autophagy dysfunction.

Show evidence (3 references)

PMID:40819564 SUPPORT In vitro / ex vivo

"CRISPR-mediated depletion of NUP107 in human cells triggers hallmark features of ALS pathology, including cytoplasmic TDP-43 mislocalization, increased phosphorylation, and autophagy dysfunction."

Direct CRISPR perturbation demonstrating that NPC dysfunction is sufficient to reproduce hallmark ALS molecular pathology, including TDP-43 cytoplasmic mislocalization, phosphorylation, and autophagy disruption. Establishes NPC dysfunction as an upstream driver of the canonical TDP-43 proteinopathy axis.

PMID:40819564 SUPPORT Human clinical

"selective loss of NPC components, particularly the scaffold proteins NUP107 and NUP93, and FG-repeat-containing components-is a consistent finding across ALS postmortem spinal cord"

Postmortem human ALS spinal cord shows selective NPC scaffold loss, confirming NPC dysfunction in human disease.

PMID:40819564 SUPPORT Model organism

"selective loss of NPC components, particularly the scaffold proteins NUP107 and NUP93, and FG-repeat-containing components-is a consistent finding across ALS postmortem spinal cord, SOD1^G93A and TDP-43 mutant mouse models, and human cell systems"

Convergent NPC dysfunction in SOD1^G93A and TDP-43 mutant mouse models confirms this finding is not a model-system artifact and supports cross-species generalizability of the mechanism.

TDP-43 Proteinopathy

Cytoplasmic aggregation of TDP-43 (TAR DNA-binding protein 43) is found in approximately 97% of ALS cases, with notable exceptions such as SOD1- and FUS-associated ALS. TDP-43 normally functions as a predominantly nuclear RNA-binding protein. In ALS it becomes depleted from the nucleus and accumulates in cytoplasmic phosphorylated, ubiquitinated inclusions, creating a coupled loss-of-nuclear-function and cytoplasmic gain-of-function state. The nuclear loss arm impairs RNA processing and cryptic-exon repression, while cytoplasmic aggregation may block normal cellular processes, disturb proteostasis, and participate in spread-like propagation.

TDP-43 RNA Dysregulation and Motor-Neuron Selective Vulnerability Model

TARDBP hgnc:11571

RNA processing GO:0006396 ⚠ ABNORMAL RNA splicing GO:0000375 ⚠ ABNORMAL

Downstream

TDP-43-Dependent Cryptic Exon Misprocessing Nuclear depletion of TDP-43 removes repression of cryptic exons and cryptic splice-polyadenylation events in disease-relevant transcripts.

TDP-43-Driven Glycolytic Failure Cytoplasmic TDP-43 sequesters hexokinase 1, coupling the proteinopathy to a glycolytic-metabolic lesion in motor neurons.

Show evidence (4 references)

PMID:42541567 SUPPORT REVIEW SYNTHESIS Human clinical

"The identification of the accumulation of TAR DNA-binding protein 43 (TDP-43) in 97% of total ALS cases represents a critical pathogenic hallmark."

Source for the 97% figure this node, the entry description, and the canonical mechanistic hypothesis all use.

PMID:32799899 SUPPORT Other

"TDP-43 bridges the divide between sporadic and familial ALS and remains a dominant protein of interest to understand disease pathogenesis."

Review summarizes TDP-43 as the common pathological bridge between sporadic and familial ALS mechanisms.

PMID:32799899 SUPPORT Human clinical

"TDP-43 was identified as a primary component of ubiquitinated and hyper-phosphorylated cytosolic aggregates observed from post-mortem tissue of patients with ALS"

Postmortem ALS evidence identifies TDP-43 as a primary component of ubiquitinated, hyperphosphorylated cytosolic aggregates.

+ 1 more reference

TDP-43-Dependent Cryptic Exon Misprocessing

Loss of nuclear TDP-43 derepresses cryptic exons and cryptic splice-polyadenylation events in RNA targets relevant to ALS. STMN2 misprocessing lowers stathmin-2, compromising axonal outgrowth, axon regeneration, and lysosome trafficking in TDP-43-deficient human motor neurons. UNC13A cryptic exon inclusion links common ALS/FTD risk variants to loss of nuclear TDP-43 function and can deplete a synaptic protein. This node represents the most concrete RNA-processing defect currently modeled as a candidate causal bridge from TDP-43 dysfunction toward motor-neuron death, while acknowledging that target priority and cell-type selectivity remain unresolved.

TDP-43 RNA Dysregulation and Motor-Neuron Selective Vulnerability Model

motor neuron CL:0000100

STMN2 hgnc:10577 UNC13A hgnc:23150

RNA splicing GO:0008380 ⚠ ABNORMAL nuclear-transcribed mRNA catabolic process, nonsense-mediated decay GO:0000184 ↑ INCREASED

Downstream

Axonal Transport Dysfunction STMN2 loss and related RNA misprocessing can impair axonal outgrowth, axon regeneration, and lysosome trafficking in human motor-neuron models.

Motor Neuron Degeneration Cryptic-exon misprocessing is modeled as an indirect, target-specific bridge from TDP-43 nuclear loss to motor-neuron degeneration through STMN2-dependent axonal repair defects, UNC13A-dependent synaptic defects, and other transcript-specific losses. Sufficiency of any single target is not established: mouse Stmn2 knockout reproduces the distal, fast-fatigable neuromuscular-junction denervation seen in ALS but does not produce axon or motoneuron degeneration, so this edge should be read as target-specific support for the distal arm rather than as a demonstrated route to motor-neuron death.

Show evidence (3 references)

PMID:26250685 SUPPORT In vitro / ex vivo

"When TDP-43 was depleted from mouse embryonic stem cells, these cryptic exons were spliced into messenger RNAs, often disrupting their translation and promoting nonsense-mediated decay."

Demonstrates the basic cryptic-exon and nonsense-mediated decay mechanism caused by TDP-43 depletion.

PMID:36927019 SUPPORT In vitro / ex vivo

"TDP-43 mislocalization results in cryptic splicing and polyadenylation of pre-messenger RNAs (pre-mRNAs) encoding stathmin-2 (also known as SCG10), a protein that is required for axonal regeneration."

Identifies STMN2 cryptic splice-polyadenylation as a direct consequence of TDP-43 mislocalization relevant to axonal regeneration.

PMID:35197626 SUPPORT Human clinical

"Loss of TDP-43 from the nucleus in human brain, neuronal cell lines and motor neurons derived from induced pluripotent stem cells resulted in the inclusion of a cryptic exon in UNC13A mRNA and reduced UNC13A protein expression."

Establishes UNC13A cryptic exon inclusion and reduced protein expression after loss of nuclear TDP-43 in human brain and motor-neuron models.

C9orf72 Repeat Expansion Toxicity

Hexanucleotide (GGGGCC) repeat expansion in C9orf72 is the most common genetic cause of ALS, accounting for 40% of familial and 5-10% of sporadic cases. The expansion leads to RNA foci formation, dipeptide repeat protein aggregation, and haploinsufficiency.

C9orf72 hgnc:28337

Show evidence (2 references)

PMID:21944778 SUPPORT

"Analysis of extended clinical series found the C9ORF72 repeat expansion to be the most common genetic abnormality in both familial FTD (11.7%) and familial ALS (23.5%). The repeat expansion leads to the loss of one alternatively spliced C9ORF72 transcript and to formation of nuclear RNA foci,..."

Original discovery paper establishing C9orf72 repeat expansion as a major cause of both FTD and ALS with dual mechanisms.

PMID:22406228 SUPPORT Human clinical

"The mutation was present in 217 (39·3%) of 552 white individuals with familial ALS from Europe and the USA."

Large cross-sectional study quantifies the C9orf72 expansion in ~40% of familial ALS in European/US populations, the source of the widely cited familial-ALS frequency and the strongest support for the node's ~40% figure.

RNA-Binding Protein Mislocalization and Stress Granule Dysfunction

A group of ALS genes encode RNA-binding proteins that share a low-complexity or prion-like domain, and their disease alleles act on the same axis: the protein's propensity to phase-separate rises, it accumulates in the cytoplasm, and stress granules become slow to disassemble. TIA1 low-complexity-domain mutations leave non-dynamic granules containing TDP-43; prion-like-domain mutations in HNRNPA1 promote self-seeding fibrils and cytoplasmic inclusions; FUS mutants mislocalize; and MATR3, an RNA- and DNA-binding protein, interacts with TDP-43 and is itself found in ALS spinal cord pathology. This node is distinct from the TDP-43 Proteinopathy node below: FUS-mutant ALS in particular is TDP-43-negative, so the shared lesion here is RNA-binding protein handling rather than TDP-43 specifically. TAF15 is a further FET-family RNA-binding protein recorded in this entry's `genetic:` section, but it is not bound to this node: its ClinGen gene-disease classification is Limited, and a PubMed search for TAF15 with amyotrophic lateral sclerosis returned no report placing its ALS-associated variants on the phase-separation or stress-granule axis, so the placement is left unmade rather than assumed from FET-family membership.

Motor neuron CL:0000100

FUS hgnc:4010 TIA1 hgnc:11802 HNRNPA1 hgnc:5031 MATR3 hgnc:6912

Cytoplasmic stress granule assembly GO:0034063 ⚠ ABNORMAL Protein localization to nucleus GO:0034504 ↓ DECREASED

Downstream

Motor Neuron Degeneration Cytoplasmic accumulation and aggregation of these RNA-binding proteins is accompanied by motor neuron loss in the kindreds in which the mutations were found.

Show evidence (6 references)

PMID:28817800 SUPPORT In vitro / ex vivo

"In live cells, TIA1 mutations delayed stress granule (SG) disassembly and promoted the accumulation of non-dynamic SGs that harbored TDP-43."

The stress granule dynamics defect that gives this node its name, shown for TIA1 mutations in live cells.

PMID:23455423 SUPPORT Model organism

"Notably, the disease mutations promote excess incorporation of hnRNPA2 and hnRNPA1 into stress granules and drive the formation of cytoplasmic inclusions in animal models"

The cytoplasmic-inclusion half of this sentence is an animal-model result, which is how it is graded. The sentence also covers stress-granule incorporation; the cell-free aggregation evidence for that half is the next item, so the two claims are carried separately rather than under one grade.

PMID:23455423 SUPPORT In vitro / ex vivo

"Indeed, the pathogenic mutations strengthen a 'steric zipper' motif in the PrLD, which accelerates the formation of self-seeding fibrils that cross-seed polymerization of wild-type hnRNP."

The biochemical half of the hnRNPA1 lesion: prion-like-domain mutations raise the protein's intrinsic tendency to polymerize, which is the phase-separation propensity this node models.

+ 3 more references

Vesicular and Endolysosomal Trafficking Failure

Three ALS genes act on membrane traffic rather than on RNA or on protein degradation directly. VAPB is a vesicle-associated membrane protein whose founder allele produces a spectrum of motor neuron disease; ANXA11 is a vesicular trafficking protein whose mutations form aggregates in spinal cord motor neurons; and FIG4 is the lipid phosphatase that regulates PI(3,5)P2, the phosphoinositide whose generating kinase PIKfyve is required for retrograde membrane trafficking from endosomes to the trans-Golgi network.

Motor neuron CL:0000100

VAPB hgnc:12649 ANXA11 hgnc:535 FIG4 hgnc:16873

Vesicle-mediated transport GO:0016192 ⚠ ABNORMAL Endosomal transport GO:0016197 ↓ DECREASED

Downstream

Motor Neuron Degeneration

Show evidence (4 references)

PMID:15372378 SUPPORT Human clinical

"These data suggest that clinically variable MNDs may be caused by a dysfunction in intracellular membrane trafficking."

The VAPB report's own conclusion, and the core claim of this node.

PMID:28469040 SUPPORT Human clinical

"We conclude that mutations in ANXA11 are associated with ALS and implicate defective intracellular protein trafficking in disease pathogenesis."

Places ANXA11 on the same trafficking axis, on the authors' own conclusion.

PMID:19118816 SUPPORT BACKGROUND Human clinical

"Mutations of the lipid phosphatase FIG4 that regulates PI(3,5)P(2) are responsible for the recessive peripheral-nerve disorder CMT4J."

Source for FIG4's enzymatic identity as the phosphatase acting on PI(3,5)P2, which is the basis for placing FIG4 on a membrane-traffic node.

+ 1 more reference

Neuregulin-ErbB4 Signaling Failure

ERBB4 encodes the receptor tyrosine kinase for neuregulin-1. ALS-associated ERBB4 mutations reduce ErbB4 autophosphorylation on neuregulin-1 stimulation, so the lesion is a weakened receptor signal rather than an aggregating or otherwise toxic protein species.

Motor neuron CL:0000100

ERBB4 hgnc:3432

ERBB4 signaling pathway GO:0038130 ↓ DECREASED

Downstream

Motor Neuron Degeneration

Show evidence (2 references)

PMID:24119685 SUPPORT In vitro / ex vivo

"Functional analysis revealed that these mutations led to a reduced autophosphorylation of ErbB4 upon neuregulin-1 (NRG-1) stimulation."

The measured signalling deficit this node represents.

PMID:24119685 SUPPORT In vitro / ex vivo

"This study indicates that disruption of the neuregulin-ErbB4 pathway is involved in the pathogenesis of ALS and potentially paves the way for the development of innovative therapeutic strategies such using NRGs or their agonists to upregulate ErbB4 functions."

The authors' conclusion that disruption of this pathway is involved in ALS pathogenesis.

Angiogenin Loss of Function

ALS-associated ANG alleles are complete loss-of-function: the mutant protein is deficient in ribonuclease activity, in nuclear translocation, or in both. Angiogenin is expressed in motor neurons as well as in endothelial cells of normal human spinal cord, so the loss is not confined to the vasculature.

Motor neuron CL:0000100 Endothelial cell CL:0000115

ANG hgnc:483

ribonuclease activity GO:0004540 ↓ DECREASED

Downstream

Motor Neuron Degeneration

Show evidence (2 references)

PMID:17886298 SUPPORT In vitro / ex vivo

"The mutant ANG proteins are unable to induce angiogenesis because of a deficiency in ribonuclease activity, nuclear translocation, or both."

Establishes the ANG lesion as loss of ribonucleolytic activity, of nuclear translocation, or of both, which is what this node asserts.

PMID:17886298 SUPPORT Human clinical

"As a correlate, we demonstrate strong ANG expression in both endothelial cells and motor neurons of normal human spinal cords from the developing fetus and adult."

Source for the two cell types bound to this node, and for reading the loss of function as motor-neuron-relevant rather than purely vascular.

Glutamate Excitotoxicity

Impaired glutamate clearance by astrocytes leads to excessive glutamate accumulation in the synaptic cleft, causing prolonged activation of glutamate receptors on motor neurons. This results in calcium overload and subsequent neuronal death.

astrocyte CL:0000127

neurotransmitter transport GO:0006836

Show evidence (3 references)

PMID:8302340 SUPPORT

"Some research suggests that the excitatory amino acid neurotransmitter glutamate may be involved in the pathogenesis."

Trial of riluzole, an antiglutamate agent, supports role of glutamate excitotoxicity in ALS pathogenesis.

PMID:40508048 SUPPORT

"understanding of the key pathogenetic links of ALS, including glutamate-mediated excitotoxicity and oxidative stress, has significantly advanced."

Recent mechanistic review highlights glutamate-mediated excitotoxicity as a key pathogenic process and therapeutic target in ALS.

PMID:42429860 SUPPORT INDIRECT In vitro / ex vivo

"a strong decrease of inhibitory transmission, which may affect the excitatory/inhibitory balance, possibly predisposing to excitotoxicity and neurodegeneration"

In FUS (P525L) hiPSC-derived spinal neurons, reduced GABA and glycine responses are proposed to shift the excitatory/inhibitory balance toward excitotoxicity. This is an authors' hypothesis from an in vitro model, so it is indirect support for the node.

Oxidative Stress

Motor neurons are particularly vulnerable to oxidative damage due to high metabolic demands. Mutations in SOD1, which encodes superoxide dismutase 1, lead to misfolded protein aggregation and increased oxidative stress contributing to neuronal death.

SOD1 hgnc:11179

response to oxidative stress GO:0006979

Animal models

Equine motor neuron disease (vitamin E-deficient horse) Horse recapitulates Chronic vitamin E deficiency is proposed to produce a sustained oxidative insult to motor neurons, giving a naturally occurring model of the oxidative stress node that is separable from any genetic lesion.

Show evidence (3 references)

PMID:8446170 SUPPORT

"a gene that encodes a cytosolic, Cu/Zn-binding superoxide dismutase (SOD1), a homodimeric metalloenzyme that catalyzes the dismutation of the toxic superoxide anion"

Discovery of SOD1 mutations in familial ALS implicates oxidative stress in disease pathogenesis.

PMID:40508048 SUPPORT

"This review considers the recent evidence on molecular mechanisms of these processes, as well as the therapeutic strategies aimed at their modulation. Special attention is paid to antiglutamatergic and antioxidant drugs as approaches to the ALS pathogenetic therapy."

Review emphasizes oxidative stress as a targetable pathogenic mechanism and discusses antioxidant therapeutic strategies in ALS.

PMID:35269543 SUPPORT

"ALS has a multifaceted nature affected by many pathological mechanisms, including oxidative stress (also via protein aggregation), mitochondrial dysfunction, glutamate-induced excitotoxicity, apoptosis, neuroinflammation, axonal degeneration, skeletal muscle deterioration and viruses."

Therapeutic strategies review highlights oxidative stress among key pathological mechanisms contributing to ALS.

Cellular Senescence in Motor Cortex and Spinal Cord

Molecular markers of cellular senescence appear in the motor cortex and spinal cord early in disease, alongside declining neural and neuromuscular function. The evidence is from TDP-43(Q331K) mice; cortical microglia are the implicated cell type, as a candidate mediator of the benefit seen when senescent cells are cleared pharmacologically. Senescence is marked by irreversible cell-cycle arrest and a pro-inflammatory senescence-associated secretory phenotype, which is the route by which it is proposed to reach neuroinflammation; the specific secreted factors operating in ALS are not established here.

microglial cell CL:0000129

cellular senescence GO:0090398 ↑ INCREASED

Animal models

TDP-43(Q331K) transgenic mouse (senescence and senolytic arm) Mouse recapitulates The model is where this node's claim comes from - senescence markers in motor cortex and spinal cord, early relative to functional decline - and the senolytic arm is what makes the senescence modifiable rather than incidental.

Downstream

Neuroinflammation Proposed route from senescent cell accumulation to the neuroinflammation node: senescent cells carry a pro-inflammatory secretory phenotype, and cortical microglia are the candidate mediator of senolytic benefit in this model. The cited study measured microglial TDP-43 burden and senescence markers rather than neuroinflammation itself.

Show evidence (2 references)

PMID:42759848 SUPPORT Model organism

"molecular markers of cellular senescence emerge in the motor cortex and spinal cord alongside declines in neural and neuromuscular function in TDP-43Q331K ALS mice, supporting senescence as an early feature of ALS pathology"

Locates the senescence markers in motor cortex and spinal cord and times them early relative to functional decline, which is what this node asserts.

PMID:42759848 SUPPORT BACKGROUND Other

"cellular senescence - a hallmark of aging marked by irreversible cell-cycle arrest and a pro-inflammatory senescence-associated secretory phenotype - has been implicated in neurodegeneration, yet its role in ALS progression remains incompletely understood"

Source for the SASP characterization in this node's description. It is the paper's framing of established work rather than its own result, which is why it is graded BACKGROUND and not attributed to the mouse experiments.

Neuroinflammation

Activated microglia and astrocytes contribute to motor neuron death non-cell-autonomously. In mutant SOD1 mice, lowering mutant SOD1 in microglia slows later disease progression without changing onset; astrocytes derived from both familial and sporadic ALS patients kill motor neurons in co-culture through secreted factors and upregulate inflammatory genes. The specific neurotoxic mediators are not settled.

microglial cell CL:0000129 astrocyte CL:0000127

Microglial activation GO:0001774 ↑ INCREASED Astrocyte activation GO:0048143 ↑ INCREASED

Downstream

Motor Neuron Degeneration Reactive microglia and astrocytes contribute to motor neuron death non-cell-autonomously: mutant SOD1 in microglia drives later disease progression in mice, and astrocytes from familial and sporadic ALS patients kill motor neurons in co-culture.

Show evidence (5 references)

PMID:15056468 SUPPORT Human clinical

"Significantly increased binding was found in motor cortex (P = 0.003), pons (P = 0.004), dorsolateral prefrontal cortex (P = 0.010) and thalamus (P = 0.005) in the ALS patients, with significant correlation between binding in the motor cortex and the burden of upper motor neuron signs clinically..."

[11C](R)-PK11195 PET in 10 ALS patients against 14 controls shows increased binding of this marker of activated microglia in motor and extra-motor regions, with motor-cortex binding tracking upper motor neuron signs. This is in vivo human evidence for the microglial arm of this node.

PMID:16741123 SUPPORT Model organism

"Diminishing the mutant levels in microglia had little effect on the early disease phase but sharply slowed later disease progression."

Cell-type-specific deletion of mutant SOD1 in mice shows that microglia drive disease progression, the non-cell-autonomous microglial arm of this node.

PMID:21832997 SUPPORT In vitro / ex vivo

"Using astrocytes generated from postmortem tissue from both FALS and SALS patients, we show that astrocytes derived from both patient groups are similarly toxic to motor neurons."

Patient-derived astrocytes, including from sporadic ALS, are toxic to motor neurons in co-culture, supporting the astrocyte arm of this node beyond SOD1 mouse models.

+ 2 more references

Microglial TREM2 Signaling

TREM2 expressed on microglia regulates proliferation, activation, and phagocytosis; altered TREM2 signaling is implicated in ALS progression through dysregulated microglial responses to motor neuron injury.

microglial cell CL:0000129

TREM2 hgnc:17761

microglial cell activation GO:0001774

Show evidence (1 reference)

PMID:34874625 SUPPORT

"Triggering receptor expressed on myeloid cell 2 (TREM2) is a surface receptor that, within the CNS, is exclusively expressed on microglia and plays crucial roles in microglial proliferation, migration, activation, metabolism, and phagocytosis."

Review summarizes how microglial TREM2 function shapes ALS progression and highlights its role in microglial activation.

Axonal Transport Dysfunction

Impaired axonal transport leads to accumulation of organelles and proteins in motor neuron axons, contributing to neurodegeneration. Gene mutations affecting cytoskeletal components (KIF5A, DCTN1, PFN1) contribute to this dysfunction.

KIF5A hgnc:6323 DCTN1 hgnc:2711 PFN1 hgnc:8881 NEFH hgnc:7737 PRPH hgnc:9461 ARHGEF28 hgnc:30322

anterograde axonal transport GO:0008089

Show evidence (2 references)

PMID:22312314 SUPPORT

"Axonal transport defects are among the early molecular events leading to neurodegeneration in mouse models of amyotrophic lateral sclerosis (ALS)."

Review confirms axonal transport defects as early pathogenic events in ALS.

PMID:41890591 SUPPORT INDIRECT Other

"Across many ALS models, including SOD1, TARDBP (TDP-43), FUS, and C9orf72, transport deficits are frequently detectable in presymptomatic stages, often preceding overt motor neuron loss or clinical manifestation, although temporal ordering varies by molecular subtype."

Synthesis across SOD1, TARDBP, FUS and C9orf72 systems reporting presymptomatic transport deficits, which is why this node is retained as a cross-genotype rather than a genotype-specific lesion. It is a single-author review proposing axonal transport impairment as the upstream convergence point; the quoted sentence itself notes that temporal ordering varies by subtype, so it is recorded here as indirect support for the framework and not as evidence that transport failure is the initiating human ALS lesion.

Impaired Autophagy

Defects in autophagy and protein quality control pathways lead to accumulation of misfolded proteins and damaged organelles in motor neurons. Multiple ALS genes (TBK1, OPTN, VCP, SQSTM1) function in autophagy.

TBK1 hgnc:11584 OPTN hgnc:17142 VCP hgnc:12666 SQSTM1 hgnc:11280 UBQLN2 hgnc:12509 CCNF hgnc:1591

autophagy GO:0006914

Show evidence (3 references)

PMID:28148298 SUPPORT

"TBK1 also has a major role in autophagy and mitophagy, chiefly the phosphorylation of autophagy adaptors. Several other ALS genes are also involved in autophagy, including p62 and OPTN."

Review describes TBK1's role in autophagy and confirms multiple ALS genes function in autophagy pathways.

PMID:21857683 SUPPORT Human clinical

"Here we show that mutations in UBQLN2, which encodes the ubiquitin-like protein ubiquilin 2, cause dominantly inherited, chromosome-X-linked ALS and ALS/dementia."

Identifies ubiquilin 2, a ubiquitin-like shuttle in protein quality control, as an ALS gene; this is the basis for binding UBQLN2 to this node.

PMID:27080313 SUPPORT In vitro / ex vivo

"Expression of mutant CCNF in neuronal cells caused abnormal ubiquitination and accumulation of ubiquitinated proteins, including TDP-43 and a SCF(Cyclin F) substrate."

Places the CCNF lesion in ubiquitination and protein-homeostasis failure, the process this node models.

TDP-43-Driven Glycolytic Failure

Cytoplasmic TDP-43 directly binds hexokinase 1 (HK1), the first rate-limiting enzyme of glycolysis, dissociating it from mitochondria and sequestering it into insoluble aggregates. The resulting loss of HK1 impairs glycolytic ATP production in motor neurons — a metabolic lesion observed consistently across TDP-43 mutant mice, patient-derived iPSC motor neurons, and ALS postmortem spinal cord. Compensating for HK1 loss reduces cytoplasmic TDP-43 and ubiquitin accumulation and improves motor performance and survival in models, marking a metabolic intervention point within the canonical proteostatic-failure framework.

motor neuron CL:0000100

HK1 hgnc:4922 TARDBP hgnc:11571

glycolytic process GO:0006096 ↓ DECREASED

Downstream

Motor Neuron Degeneration Loss of HK1-dependent glycolytic ATP production contributes to the bioenergetic failure of vulnerable motor neurons.

Show evidence (2 references)

PMID:41838122 SUPPORT In vitro / ex vivo

"cytoplasmic TDP-43 directly disrupts glycolysis by targeting hexokinase 1 (HK1), the first rate-limiting enzyme of the pathway"

Identifies HK1 sequestration by cytoplasmic TDP-43 as a direct metabolic mechanism — a novel addition to the canonical proteostatic-failure model surfaced by the 2026 hypothesis-search report.

PMID:41838122 SUPPORT Human clinical

"postmortem spinal cord tissue from ALS patients, we observe consistent decreases in HK1 protein level"

Consistent HK1 decreases in ALS postmortem spinal cord confirm the glycolytic lesion in human disease tissue.

Endogenous Retrovirus Reactivation and TDP-43 Feedback

Reactivation of endogenous retroviruses (ERVs), in particular human endogenous retrovirus type K (HERV-K/HML-2), and TDP-43 proteinopathy are mutually reinforcing. ERV expression is sufficient to stimulate cytoplasmic aggregation of TDP-43, and viral ERV transmission propagates TDP-43 pathology to recipient cells, providing a self-sustaining positive-feedback loop that can drive intercellular spread and disease progression. ERV transcripts are elevated in ALS brain, and this loop is the mechanistic rationale for repurposing antiretroviral therapy (e.g., Triumeq) in ALS.

motor neuron CL:0000100

inflammatory response GO:0006954 ↑ INCREASED

Downstream

TDP-43 Proteinopathy ERV (HERV-K) expression is sufficient to stimulate cytoplasmic TDP-43 aggregation, closing a feed-forward loop with TDP-43 proteinopathy.

Motor Neuron Degeneration Viral ERV transmission propagates TDP-43 pathology to recipient cells, providing a mechanism for intercellular spread of degeneration.

Show evidence (2 references)

PMID:36810738 SUPPORT Model organism

"each sufficient to stimulate cytoplasmic aggregation of human TDP-43"

Drosophila and human-ERV experiments show ERV expression seeds cytoplasmic TDP-43 aggregation, the basis of the ERV-TDP-43 feedback loop.

PMID:37450244 SUPPORT Other

"human endogenous retrovirus type K (HERV-K), have been proposed to be involved in the propagation of neurodegeneration in ALS"

Review articulating the HERV-K/TDP-43 propagation model and its rationale as a target for antiretroviral therapy (Triumeq) in ALS.

⬡

Pathograph

Use Group by to collapse related nodes into one box. Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

Digestive 1

Dysphagia FREQUENT HP:0002015

Show evidence (3 references)

ORPHA:803 SUPPORT

"HP:0002015 | Dysphagia | Frequent (79-30%)"

Orphanet lists dysphagia as frequent in ALS.

PMID:33085325 SUPPORT

"Bulbar dysfunction can manifest as dysphagia (trouble swallowing) and dysarthria (trouble speaking)."

StatPearls article highlights dysphagia as a common bulbar manifestation in ALS.

PMID:39207520 SUPPORT

"Throughout the disease, more than two-thirds of ALS patients experience dysphagia, regardless of the region of onset."

Dysphagia-focused review reports that swallowing difficulty affects the majority of ALS patients.

Head and Neck 4

Drooling FREQUENT HP:0002307

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0002307 | Drooling | Frequent (79-30%)"

Orphanet lists drooling as frequent in ALS.

PMID:34920148 SUPPORT

"The pooled prevalence of sialorrhea among ALS patients was 30.8% (95% CI: 20.0%-44.2%)."

Meta-analysis establishes pooled sialorrhea prevalence of 30.8% in ALS patients.

Tongue Fasciculations OCCASIONAL HP:0001308

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0001308 | Tongue fasciculations | Occasional (29-5%)"

Orphanet lists tongue fasciculations as occasional in ALS.

Tongue Atrophy FREQUENT HP:0012473

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0012473 | Tongue atrophy | Frequent (79-30%)"

Orphanet lists tongue atrophy as frequent in ALS.

Xerostomia FREQUENT HP:0000217

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0000217 | Xerostomia | Frequent (79-30%)"

Orphanet lists xerostomia as frequent in ALS.

Limbs 3

Upper Limb Muscle Weakness FREQUENT HP:0003484

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0003484 | Upper limb muscle weakness | Frequent (79-30%)"

Orphanet lists upper limb muscle weakness as frequent in ALS.

PMID:33085325 SUPPORT

"the majority of the patients present with asymmetric limb weakness (80%) or bulbar dysfunction (20%)."

StatPearls review confirms asymmetric limb weakness as the most common presentation.

Lower Limb Muscle Weakness FREQUENT HP:0007340

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0007340 | Lower limb muscle weakness | Frequent (79-30%)"

Orphanet lists lower limb muscle weakness as frequent in ALS.

Foot Dorsiflexor Weakness OCCASIONAL HP:0009027

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0009027 | Foot dorsiflexor weakness | Occasional (29-5%)"

Orphanet lists foot dorsiflexor weakness as occasional in ALS.

Musculoskeletal 11

Generalized Muscle Weakness OBLIGATE HP:0003324

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0003324 | Generalized muscle weakness | Very frequent (99-80%)"

Orphanet lists generalized muscle weakness as very frequent in ALS.

PMID:38891021 SUPPORT

"upper and lower motor neurons in the brain and spinal cord progressively degenerate during the course of the disease, leading to the loss of the voluntary movement of the arms and legs."

Review summarizes progressive motor neuron degeneration causing loss of voluntary movement.

Spasticity FREQUENT HP:0001257

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0001257 | Spasticity | Frequent (79-30%)"

Orphanet lists spasticity as frequent in ALS.

PMID:33085325 SUPPORT

"Upper motor findings include spasticity, hyperactive reflexes, and a positive Babinski sign."

StatPearls article confirms spasticity as a cardinal upper motor neuron sign in ALS.

Fatigable Weakness of Bulbar Muscles FREQUENT HP:0030192

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0030192 | Fatigable weakness of bulbar muscles | Frequent (79-30%)"

Orphanet lists fatigable weakness of bulbar muscles as frequent in ALS.

Fatigable Weakness of Swallowing Muscles FREQUENT HP:0030195

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0030195 | Fatigable weakness of swallowing muscles | Frequent (79-30%)"

Orphanet lists fatigable weakness of swallowing muscles as frequent in ALS.

Fatigable Weakness of Respiratory Muscles FREQUENT HP:0030196

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0030196 | Fatigable weakness of respiratory muscles | Frequent (79-30%)"

Orphanet lists fatigable weakness of respiratory muscles as frequent in ALS.

Respiratory Insufficiency FREQUENT Respiratory insufficiency due to muscle weakness HP:0002747

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0002878 | Respiratory failure | Frequent (79-30%)"

Orphanet lists respiratory failure (HP:0002878) as frequent; this entry uses the more specific HP:0002747 (respiratory insufficiency due to muscle weakness) which captures the neuromuscular etiology.

PMID:33085325 SUPPORT

"Death usually occurs within 2 to 5 years from respiratory failure."

Clinical overview states respiratory failure is the usual terminal event in ALS.

Skeletal Muscle Atrophy FREQUENT HP:0003202

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0003202 | Skeletal muscle atrophy | Frequent (79-30%)"

Orphanet lists skeletal muscle atrophy as frequent in ALS.

PMID:33085325 SUPPORT

"Lower motor neuron signs include muscle atrophy, weakness, flaccid paralysis, absent reflexes, fasciculations, and fibrillations."

Review details muscle atrophy as a key lower motor neuron sign in ALS.

Distal Amyotrophy FREQUENT HP:0003693

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0003693 | Distal amyotrophy | Frequent (79-30%)"

Orphanet lists distal amyotrophy as frequent in ALS.

Progressive Distal Muscular Atrophy FREQUENT HP:0008955

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0008955 | Progressive distal muscular atrophy | Frequent (79-30%)"

Orphanet lists progressive distal muscular atrophy as frequent in ALS.

Muscle Spasm FREQUENT HP:0003394

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0003394 | Muscle spasm | Frequent (79-30%)"

Orphanet lists muscle spasm as frequent in ALS.

Spastic Paraparesis OCCASIONAL HP:0002313

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0002313 | Spastic paraparesis | Occasional (29-5%)"

Orphanet lists spastic paraparesis as occasional in ALS.

Nervous System 18

Neurodegeneration OBLIGATE HP:0002180

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0002180 | Neurodegeneration | Very frequent (99-80%)"

Orphanet lists neurodegeneration as very frequent in ALS.

PMID:36116464 SUPPORT

"Amyotrophic lateral sclerosis is a fatal CNS neurodegenerative disease."

Lancet Seminar identifies ALS as a fatal CNS neurodegenerative disease.

Motor Neuron Atrophy VERY_FREQUENT HP:0007373

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0007373 | Motor neuron atrophy | Very frequent (99-80%)"

Orphanet lists motor neuron atrophy as very frequent in ALS.

Fasciculations FREQUENT HP:0002380

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0002380 | Fasciculations | Frequent (79-30%)"

Orphanet lists fasciculations as frequent in ALS.

PMID:27117334 SUPPORT

"In the LMN system, fasciculation potentials (FPs) are the earliest changes observed in affected muscles, a feature of LMN hyperexcitability."

Review confirms fasciculations are an early marker of lower motor neuron dysfunction in ALS.

Hyperreflexia FREQUENT HP:0001347

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0001347 | Hyperreflexia | Frequent (79-30%)"

Orphanet lists hyperreflexia as frequent in ALS.

PMID:33085325 SUPPORT

"Upper motor findings include spasticity, hyperactive reflexes, and a positive Babinski sign."

StatPearls review lists hyperactive reflexes as a core upper motor neuron finding in ALS.

Babinski Sign FREQUENT HP:0003487

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0003487 | Babinski sign | Frequent (79-30%)"

Orphanet lists Babinski sign as frequent in ALS.

PMID:33085325 SUPPORT

"Upper motor findings include spasticity, hyperactive reflexes, and a positive Babinski sign."

StatPearls review confirms positive Babinski sign as an upper motor neuron finding in ALS.

Hoffmann Sign FREQUENT HP:0031993

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0031993 | Hoffmann sign | Frequent (79-30%)"

Orphanet lists Hoffmann sign as frequent in ALS.

Dysarthria FREQUENT HP:0001260

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0001260 | Dysarthria | Frequent (79-30%)"

Orphanet lists dysarthria as frequent in ALS.

PMID:33085325 SUPPORT

"Bulbar dysfunction can manifest as dysphagia (trouble swallowing) and dysarthria (trouble speaking)."

Review notes bulbar dysfunction in ALS commonly presents with dysarthria and dysphagia.

Paralysis FREQUENT HP:0003470

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0003470 | Paralysis | Frequent (79-30%)"

Orphanet lists paralysis as frequent in ALS.

Steppage Gait OCCASIONAL HP:0003376

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0003376 | Steppage gait | Occasional (29-5%)"

Orphanet lists steppage gait as occasional in ALS.

Emotional Lability FREQUENT HP:0000712

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0000712 | Emotional lability | Frequent (79-30%)"

Orphanet lists emotional lability as frequent in ALS.

PMID:33085325 SUPPORT

"Some patients may also present with Pseudobulbar affect, which is dysregulation of emotional responses exhibited by excessive laughter or crying."

StatPearls review describes pseudobulbar affect as dysregulated emotional responses in ALS patients.

Depression FREQUENT HP:0000716

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0000716 | Depression | Frequent (79-30%)"

Orphanet lists depression as frequent in ALS.

PMID:23466470 SUPPORT

"Symptoms of dysphagia, depression, cognitive impairment, difficulty with self-feeding and meal preparation, hypermetabolism, anxiety, respiratory insufficiency, and fatigue with meals increase the risk of malnutrition."

Nutrition review identifies depression as a contributing symptom in ALS.

Anxiety FREQUENT HP:0000739

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0000739 | Anxiety | Frequent (79-30%)"

Orphanet lists anxiety as frequent in ALS.

PMID:23466470 SUPPORT

Nutrition review lists anxiety among symptoms contributing to malnutrition in ALS.

Atypical Behavior FREQUENT HP:0000708

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0000708 | Atypical behavior | Frequent (79-30%)"

Orphanet lists atypical behavior as frequent in ALS.

PMID:33085325 SUPPORT

"Patients can also display changes in behavior due to frontotemporal dysfunction, and about 15% of patients develop frontotemporal dementia."

StatPearls review confirms behavioral changes from frontotemporal dysfunction in ALS patients.

Cognitive Impairment FREQUENT HP:0100543

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0100543 | Cognitive impairment | Frequent (79-30%)"

Orphanet lists cognitive impairment as frequent in ALS.

PMID:22305801 SUPPORT

"Cognitive impairment occurs in up to 50% of cases, and one in seven patients develops frank frontotemporal dementia (FTD)."

Population-based study reports cognitive impairment in up to 50% of ALS cases.

Frontotemporal Dementia OCCASIONAL HP:0002145

Show evidence (3 references)

ORPHA:803 SUPPORT

"HP:0002145 | Frontotemporal dementia | Occasional (29-5%)"

Orphanet lists frontotemporal dementia as occasional in ALS.

PMID:33085325 SUPPORT

"about 15% of patients develop frontotemporal dementia."

StatPearls review reports approximately 15% of ALS patients develop frontotemporal dementia.

PMID:38802173 SUPPORT

"ALS forms a clinical continuum with frontotemporal dementia (FTD), in which there are progressive language deficits or behavioral changes."

Review describes ALS-FTD clinical continuum with overlapping genetics and pathology.

Language Impairment OCCASIONAL HP:0002463

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0002463 | Language impairment | Occasional (29-5%)"

Orphanet lists language impairment as occasional in ALS.

PMID:38802173 SUPPORT

"ALS forms a clinical continuum with frontotemporal dementia (FTD), in which there are progressive language deficits or behavioral changes."

ALS clinical features review describes progressive language deficits within the ALS-FTD spectrum.

Sleep Disturbance OCCASIONAL HP:0002360

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0002360 | Sleep abnormality | Occasional (29-5%)"

Orphanet lists sleep disturbance as occasional in ALS.

Jaw Hyperreflexia OCCASIONAL HP:0033683

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0033683 | Jaw hyperreflexia | Occasional (29-5%)"

Orphanet lists jaw hyperreflexia as occasional in ALS.

Respiratory 4

Abnormality on Pulmonary Function Testing FREQUENT HP:0030878

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0030878 | Abnormality on pulmonary function testing | Frequent (79-30%)"

Orphanet lists abnormality on pulmonary function testing as frequent in ALS.

Dyspnea FREQUENT HP:0002094

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0002094 | Dyspnea | Frequent (79-30%)"

Orphanet lists dyspnea as frequent in ALS.

Orthopnea OCCASIONAL HP:0012764

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0012764 | Orthopnea | Occasional (29-5%)"

Orphanet lists orthopnea as occasional in ALS.

Laryngospasm VERY_RARE HP:0025425

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0025425 | Laryngospasm | Very rare (<4-1%)"

Orphanet lists laryngospasm as very rare in ALS.

Voice 1

Dysphonia FREQUENT HP:0001618

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0001618 | Dysphonia | Frequent (79-30%)"

Orphanet lists dysphonia as frequent in ALS.

Constitutional 2

Fatigue FREQUENT HP:0012378

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0012378 | Fatigue | Frequent (79-30%)"

Orphanet lists fatigue as frequent in ALS.

PMID:23466470 SUPPORT

Nutrition review identifies fatigue as a contributing symptom to malnutrition risk in ALS.

Pain FREQUENT HP:0012531

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0012531 | Pain | Frequent (79-30%)"

Orphanet lists pain as frequent in ALS.

PMID:33661072 SUPPORT

"Pooled prevalence of pain in ALS across all studies was 60% (95% CI = 50-69%), with a high degree of heterogeneity"

Systematic review and meta-analysis establishes pain prevalence of 60% across ALS populations.

Growth 2

Weight Loss FREQUENT HP:0001824

Show evidence (2 references)

ORPHA:803 SUPPORT

"HP:0001824 | Weight loss | Frequent (79-30%)"

Orphanet lists weight loss as frequent in ALS.

PMID:23466470 SUPPORT

"Amyotrophic lateral sclerosis (ALS) is a progressive neurological disease with high risk of malnutrition."

Nutrition review confirms ALS carries high risk of malnutrition and weight loss.

Cachexia OCCASIONAL HP:0004326

Show evidence (1 reference)

ORPHA:803 SUPPORT

"HP:0004326 | Cachexia | Occasional (29-5%)"

Orphanet lists cachexia as occasional in ALS.

🧬

Genetic Associations

C9orf72 Repeat Expansion (Causative)

Gene: C9orf72 hgnc:28337 gene page relationship_type: CAUSATIVE

Autosomal Dominant

Show evidence (5 references)

ORPHA:803 SUPPORT

"C9ORF72 | C9orf72-SMCR8 complex subunit | hgnc:28337 | Disease-causing germline mutation(s) in"

Orphanet lists C9ORF72 as harboring disease-causing germline mutations in ALS.

PMID:21944778 SUPPORT

"Analysis of extended clinical series found the C9ORF72 repeat expansion to be the most common genetic abnormality in both familial FTD (11.7%) and familial ALS (23.5%)"

Original discovery paper establishing C9orf72 as the most common genetic cause of familial ALS.

PMID:22406228 SUPPORT Human clinical

"This genetic lesion accounted for a large proportion (∼40·0%) of familial cases of ALS and FTD."

Cross-sectional study's headline conclusion supports the ~40% familial figure cited in this entry's notes.

+ 2 more references

SOD1 Mutations (Causative)

Gene: SOD1 hgnc:11179 gene page relationship_type: CAUSATIVE

Autosomal Dominant

Show evidence (3 references)

ORPHA:803 SUPPORT

"SOD1 | superoxide dismutase 1 | hgnc:11179 | Disease-causing germline mutation(s) in"

Orphanet lists SOD1 as harboring disease-causing germline mutations in ALS.

PMID:8446170 SUPPORT

"We identified 11 different SOD1 missense mutations in 13 different FALS families."

Original discovery paper identifying SOD1 mutations as a cause of familial ALS.

PMID:28057713 SUPPORT Human clinical

Meta-analysis of 111 studies giving population-stratified mutation frequencies for the four commonest ALS genes; this is the source for the per-gene familial-ALS shares quoted in this record.

TARDBP Mutations (Causative)

Gene: TARDBP hgnc:11571 gene page relationship_type: CAUSATIVE

Autosomal Dominant

Show evidence (3 references)

ORPHA:803 SUPPORT

"TARDBP | TAR DNA binding protein | hgnc:11571 | Disease-causing germline mutation(s) in"

Orphanet lists TARDBP as harboring disease-causing germline mutations in ALS.

PMID:35805149 SUPPORT

"Mutations in C9orf72, SOD1, TAR DNA binding protein 43 (TARDBP), and fused in sarcoma (FUS) genes are the four most common ones."

Gene therapy review highlights TARDBP among the most common ALS genes targeted by therapeutic strategies.

PMID:28057713 SUPPORT Human clinical

Meta-analysis of 111 studies giving population-stratified mutation frequencies for the four commonest ALS genes; this is the source for the per-gene familial-ALS shares quoted in this record.

FUS Mutations (Causative)

Gene: FUS hgnc:4010 gene page relationship_type: CAUSATIVE

Autosomal Dominant

Show evidence (3 references)

ORPHA:803 SUPPORT

"FUS | FUS RNA binding protein | hgnc:4010 | Disease-causing germline mutation(s) in"

Orphanet lists FUS as harboring disease-causing germline mutations in ALS.

PMID:35805149 SUPPORT

"Mutations in C9orf72, SOD1, TAR DNA binding protein 43 (TARDBP), and fused in sarcoma (FUS) genes are the four most common ones."

Review notes FUS among the four most common ALS genes and discusses gene-targeted therapies.

PMID:28057713 SUPPORT Human clinical

Meta-analysis of 111 studies giving population-stratified mutation frequencies for the four commonest ALS genes; this is the source for the per-gene familial-ALS shares quoted in this record.

NEK1 Variants (Susceptibility)

Gene: NEK1 hgnc:7744 gene page relationship_type: SUSCEPTIBILITY

Show evidence (2 references)

ORPHA:803 SUPPORT

"NEK1 | NIMA related kinase 1 | hgnc:7744 | Major susceptibility factor in"

Orphanet lists NEK1 as a major susceptibility factor in ALS.

PMID:27455347 SUPPORT

"In total, we observed NEK1 risk variants in nearly 3% of ALS cases. NEK1 has been linked to several cellular functions, including cilia formation, DNA-damage response, microtubule stability, neuronal morphology and axonal polarity."

Large-scale genetic study identifying NEK1 variants as risk factors for ALS.

ATXN2 Intermediate-Length Repeat Expansion (Susceptibility)

Gene: ATXN2 hgnc:10555 gene page relationship_type: SUSCEPTIBILITY

Show evidence (1 reference)

PMID:20740007 SUPPORT Human clinical

"We found that intermediate-length polyQ expansions (27-33 glutamines) in ATXN2 were significantly associated with ALS. These data establish ATXN2 as a relatively common ALS susceptibility gene."

Landmark study analyzing the ATXN2 polyQ repeat in 915 ALS patients establishes intermediate-length expansions as a common ALS susceptibility factor and identifies ATXN2 as a modifier of TDP-43 toxicity.

ARHGEF28 (Pathogenic Variants)

Gene: ARHGEF28 hgnc:30322

Show evidence (1 reference)

CGGV:assertion_ac27cecc-9749-4c69-88fa-fe83b2d49568-2024-03-28T190000.000Z SUPPORT Other

ClinGen classifies the ARHGEF28-amyotrophic lateral sclerosis gene-disease relationship as limited with semidominant inheritance.

ARPP21 (Pathogenic Variants)

Gene: ARPP21 hgnc:16968

Show evidence (1 reference)

CGGV:assertion_02d4089a-94dd-42b6-ab09-dc258db00ae9-2025-01-14T200000.000Z SUPPORT Other

ClinGen classifies the ARPP21-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

CAV1 (Pathogenic Variants)

Gene: CAV1 hgnc:1527 gene page

Show evidence (1 reference)

CGGV:assertion_cab41529-d295-466c-8821-75a16bb12c38-2023-12-21T170000.000Z SUPPORT Other

ClinGen classifies the CAV1-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

CAV2 (Pathogenic Variants)

Gene: CAV2 hgnc:1528

Show evidence (1 reference)

CGGV:assertion_38faae4c-13ae-4c28-bea4-43e3ad15e178-2023-12-21T170000.000Z SUPPORT Other

ClinGen classifies the CAV2-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

CFAP410 (Pathogenic Variants)

Gene: CFAP410 hgnc:1260 gene page

Show evidence (1 reference)

CGGV:assertion_bde7edf1-ccfa-443e-a917-cf3d2dd9cba6-2023-12-12T180000.000Z SUPPORT Other

ClinGen classifies the CFAP410-amyotrophic lateral sclerosis gene-disease relationship as limited with semidominant inheritance.

DCTN1 (Pathogenic Variants)

Gene: DCTN1 hgnc:2711 gene page

Show evidence (1 reference)

CGGV:assertion_5cd19f2c-2499-417f-94c8-2bd4bedf34ef-2023-08-04T160000.000Z SUPPORT Other

ClinGen classifies the DCTN1-amyotrophic lateral sclerosis gene-disease relationship as moderate with autosomal dominant inheritance.

DNAJC7 (Pathogenic Variants)

Gene: DNAJC7 hgnc:12392

Show evidence (1 reference)

CGGV:assertion_e2a12a19-b37a-4654-87fa-3a921c202c87-2022-10-27T160000.000Z SUPPORT Other

ClinGen classifies the DNAJC7-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

GLE1 (Pathogenic Variants)

Gene: GLE1 hgnc:4315 gene page

Show evidence (1 reference)

CGGV:assertion_0284b3cd-38af-4309-8ce4-054a0379e693-2023-10-10T160000.000Z SUPPORT Other

ClinGen classifies the GLE1-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

GLT8D1 (Pathogenic Variants)

Gene: GLT8D1 hgnc:24870

Show evidence (1 reference)

CGGV:assertion_a2c4f919-ccb5-4d9f-a604-5ed19e19057e-2025-01-14T200000.000Z SUPPORT Other

ClinGen classifies the GLT8D1-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

LGALSL (Pathogenic Variants)

Gene: LGALSL hgnc:25012

Show evidence (1 reference)

CGGV:assertion_5a2db59f-5293-4e5d-ae34-5a38d8c6ebdf-2023-02-14T170000.000Z SUPPORT Other

ClinGen classifies the LGALSL-amyotrophic lateral sclerosis gene-disease relationship as limited with undetermined inheritance.

NEFH (Pathogenic Variants)

Gene: NEFH hgnc:7737 gene page

Show evidence (1 reference)

CGGV:assertion_6c71deac-6b11-4947-8834-8391d516a9c9-2023-03-23T160000.000Z SUPPORT Other

ClinGen classifies the NEFH-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

NUP50 (Pathogenic Variants)

Gene: NUP50 hgnc:8065

Show evidence (1 reference)

CGGV:assertion_0ce3418e-c7e5-452b-9db6-661571331822-2024-06-27T160000.000Z SUPPORT Other

ClinGen classifies the NUP50-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

PRPH (Pathogenic Variants)

Gene: PRPH hgnc:9461

Show evidence (1 reference)

CGGV:assertion_3d11b04d-508a-4f91-9d9a-b5016fd0b940-2022-12-13T170000.000Z SUPPORT Other

ClinGen classifies the PRPH-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

SPTLC2 (Pathogenic Variants)

Gene: SPTLC2 hgnc:11278 gene page

Show evidence (1 reference)

CGGV:assertion_402cf65d-02f1-4cc1-a45e-b3bd3ad48b86-2024-06-26T160000.000Z SUPPORT Other

ClinGen classifies the SPTLC2-amyotrophic lateral sclerosis gene-disease relationship as strong with autosomal dominant inheritance.

SS18L1 (Pathogenic Variants)

Gene: SS18L1 hgnc:15592

Show evidence (1 reference)

CGGV:assertion_6e148a06-50fc-45f3-90ea-023dc8687577-2023-05-25T160000.000Z SUPPORT Other

ClinGen classifies the SS18L1-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

TAF15 (Pathogenic Variants)

Gene: TAF15 hgnc:11547

Show evidence (1 reference)

CGGV:assertion_605446ae-fd1f-4451-bd49-643c24cd652e-2021-11-03T020945.214Z SUPPORT Other

ClinGen classifies the TAF15-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.

VAPB (Causative)

Gene: VAPB hgnc:12649 gene page relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"VAPB | VAMP associated protein B and C | hgnc:12649 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

ANG (Causative)

Gene: ANG hgnc:483 relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"ANG | angiogenin | hgnc:483 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

FIG4 (Risk factor)

Gene: FIG4 hgnc:16873 gene page relationship_type: RISK_FACTOR

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"FIG4 | FIG4 phosphoinositide 5-phosphatase | hgnc:16873 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

OPTN (Causative)

Gene: OPTN hgnc:17142 gene page relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"OPTN | optineurin | hgnc:17142 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

UBQLN2 (Causative)

Gene: UBQLN2 hgnc:12509 relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"UBQLN2 | ubiquilin 2 | hgnc:12509 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

PFN1 (Causative)

Gene: PFN1 hgnc:8881 gene page relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"PFN1 | profilin 1 | hgnc:8881 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

ERBB4 (Causative)

Gene: ERBB4 hgnc:3432 relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"ERBB4 | erb-b2 receptor tyrosine kinase 4 | hgnc:3432 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

HNRNPA1 (Causative)

Gene: HNRNPA1 hgnc:5031 gene page relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"HNRNPA1 | heterogeneous nuclear ribonucleoprotein A1 | hgnc:5031 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

MATR3 (Causative)

Gene: MATR3 hgnc:6912 relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"MATR3 | matrin 3 | hgnc:6912 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

ANXA11 (Causative)

Gene: ANXA11 hgnc:535 gene page relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"ANXA11 | annexin A11 | hgnc:535 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

TBK1 (Causative)

Gene: TBK1 hgnc:11584 gene page relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:25803835 SUPPORT Human clinical

"Gene-based rare variant analysis identified an exome-wide significant enrichment of eight loss-of-function (LoF) mutations in TBK1 (encoding TANK-binding kinase 1) in 13 fALS pedigrees."

The familial exome result on which the CAUSATIVE grading rests.

ORPHA:803 SUPPORT Other

"TBK1 | TANK binding kinase 1 | hgnc:11584 | Major susceptibility factor in"

Orphanet records a TBK1-ALS association, which supports the gene-disease link but files it as a major susceptibility factor rather than as a cause; it does not by itself support the CAUSATIVE grading (see notes).

CCNF (Causative)

Gene: CCNF hgnc:1591 relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"CCNF | cyclin F | hgnc:1591 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

VCP (Causative)

Gene: VCP hgnc:12666 gene page relationship_type: CAUSATIVE

Show evidence (1 reference)

ORPHA:803 SUPPORT Other

"VCP | valosin containing protein | hgnc:12666 | Disease-causing germline mutation(s) in"

Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.

TIA1 (Disputed)

Gene: TIA1 hgnc:11802 gene page relationship_type: DISPUTED

Show evidence (2 references)

PMID:28817800 SUPPORT Human clinical

"Subsequent genetic association analyses showed an increased burden of TIA1 LCD mutations in ALS patients compared to controls (p = 8.7 × 10-6)."

The burden analysis offered in support of TIA1 as an ALS gene.

PMID:29235362 REFUTE Human clinical

"Here, we argue that data from the published pedigree that supports TIA1 is insufficient to prove causality."

The published challenge to that evidence, and the basis for the DISPUTED grade.

LRP12 (Causative)

Gene: LRP12 hgnc:31708 gene page relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:37339631 SUPPORT Human clinical

"In conclusion, CGG repeat expansions in LRP12 cause ALS and OPDM, depending on the length of the repeat."

The primary report's conclusion, which is the basis for the CAUSATIVE grade.

PMID:38726482 SUPPORT INDIRECT Human clinical

"To date, LRP12 CGG repeat expansions have not been reported in ALS patients of European ancestry and may be limited to rare ALS patients of Asian ancestry and atypical clinical presentations."

Supports the ancestry restriction recorded in the notes above; it bears on the scope of the claim rather than directly on whether the expansion is pathogenic in the families where it was found.

💊

Medical Actions

Riluzole

Action: Pharmacotherapy NCIT:C15986

Agent: riluzole NCIT:C47704

Glutamate antagonist that modestly extends survival by 2-3 months. It is the first FDA-approved treatment for ALS and works by reducing excitotoxic neuronal damage.

Mechanism Target:

INHIBITS Glutamate Excitotoxicity — Riluzole blocks voltage-gated sodium channels and reduces glutamate release at presynaptic terminals, attenuating excitotoxic motor neuron injury.

Show evidence (1 reference)

PMID:8302340 SUPPORT

"The antiglutamate agent riluzole appears to slow the progression of amyotrophic lateral sclerosis, and it may improve survival in patients with disease of bulbar onset."

Landmark trial demonstrating riluzole's survival benefit in ALS patients.

Edaravone

Action: Pharmacotherapy NCIT:C15986

Agent: edaravone CHEBI:31530

Free-radical scavenger approved for ALS. A phase 3 trial in a selected subset of early-stage patients, defined from a post-hoc analysis of an earlier trial, showed a smaller decline in ALSFRS-R than placebo; a large real-world cohort found long-term intravenous edaravone well tolerated but without disease-modifying benefit. Benefit outside the trial-defined subset is therefore not established.

Mechanism Target:

INHIBITS Oxidative Stress — Edaravone is a free-radical scavenger that neutralizes reactive oxygen species, reducing oxidative neuronal injury in motor neurons.

Show evidence (2 references)

PMID:28522181 SUPPORT

"Edaravone showed efficacy in a small subset of people with ALS who met criteria identified in post-hoc analysis of a previous phase 3 study, showing a significantly smaller decline of ALSFRS-R score compared with placebo."

Phase 3 trial reporting a smaller ALSFRS-R decline with edaravone than placebo in a narrowly selected subset of patients defined by post-hoc criteria from an earlier trial; the benefit is not shown for ALS patients generally.

PMID:35006266 REFUTE

"although long-term intravenous edaravone therapy for patients with ALS was feasible and mainly well tolerated, it was not associated with any disease-modifying benefit."

Real-world cohort study found long-term intravenous edaravone well tolerated but without additional disease-modifying benefit versus standard therapy.

Tofersen

Action: Pharmacotherapy NCIT:C15986

Agent: tofersen NCIT:C166584

Platform: Antisense oligonucleotide RNase H knockdown Delivery: Unformulated (free uptake) Targeting: Unconjugated Chemistry: 2′-MOE

RNA target: SOD1 hgnc:11179 SOD1 mRNA

Antisense oligonucleotide therapy approved for SOD1-ALS that reduces SOD1 protein production, targeting the underlying genetic cause in this subset of patients. The approval rests on target engagement and biomarker lowering rather than on a positive randomized clinical endpoint: over the 28-week randomized period of VALOR tofersen lowered CSF SOD1 and plasma neurofilament light chain but did not improve the prespecified clinical endpoints. A later integrated analysis of VALOR and its open-label extension reported numerically less functional, respiratory, strength and quality-of-life decline over 148 weeks with earlier rather than delayed initiation; because that comparison follows crossover and is open-label with substantial attrition, it is supportive long-term observation rather than a blinded randomized efficacy result.

Mechanism Target:

MODULATES Motor Neuron Degeneration — Tofersen reduces mutant SOD1 protein levels via RNase H-mediated mRNA knockdown, reducing the SOD1-driven oxidative and proteotoxic burden that accelerates motor neuron loss in SOD1-ALS.

Show evidence (4 references)

PMID:32640130 SUPPORT

"In adults with ALS due to SOD1 mutations, CSF SOD1 concentrations decreased at the highest concentration of tofersen administered intrathecally over a period of 12 weeks."

Phase 1-2 trial demonstrating tofersen reduces CSF SOD1 levels in SOD1-ALS patients.

PMID:36129998 SUPPORT

"The intrathecally administered antisense oligonucleotide tofersen reduces synthesis of the superoxide dismutase 1 (SOD1) protein and is being studied in patients with amyotrophic lateral sclerosis (ALS) associated with mutations in SOD1 (SOD1 ALS)."

VALOR pivotal phase 3 trial (the basis for tofersen's FDA approval) confirms the antisense mechanism reduces SOD1 protein synthesis in SOD1 ALS.

PMID:36129998 SUPPORT Human clinical

"In persons with SOD1 ALS, tofersen reduced concentrations of SOD1 in CSF and of neurofilament light chains in plasma over 28 weeks but did not improve clinical end points and was associated with adverse events."

VALOR's own conclusion is the basis for this entry's statement that the tofersen evidence is target-engagement- and biomarker-led. It records that the randomized 28-week period lowered CSF SOD1 and plasma neurofilament light chain without improving the prespecified clinical endpoints.

+ 1 more reference

Jacifusen (ION363)

Action: Pharmacotherapy NCIT:C15986

Agent: ulefnersen NCIT:C188629

Platform: Antisense oligonucleotide RNase H knockdown

RNA target: FUS hgnc:4010 FUS pre-mRNA

Investigational antisense oligonucleotide (ION363, also known as ulefnersen) that non-allele-specifically silences FUS to lower wild-type and mutant FUS protein, targeting the gain-of-function genetic cause in FUS-ALS. Delivered by serial intrathecal injection; evaluated in an expanded-access case series and an ongoing clinical trial.

Mechanism Target:

MODULATES Motor Neuron Degeneration — Jacifusen silences FUS expression via RNase H-mediated knockdown, reducing mutant FUS protein aggregation and toxicity in motor neurons and delaying neurodegeneration in FUS-ALS.

Show evidence (3 references)

PMID:40414239 SUPPORT Human clinical

"Jacifusen is an antisense oligonucleotide targeting FUS pre-mRNA, previously shown to delay neurodegeneration in a mouse model and potentially slow functional decline in a first-in-human study."

Lancet expanded-access case series confirms jacifusen is an ASO targeting FUS pre-mRNA, supporting the FUS-knockdown mechanism of this treatment.

PMID:40414239 SUPPORT Human clinical

"Biochemical and immunohistochemical analysis of CNS tissue samples from four participants showed reduced FUS protein levels and an apparent decrease in the burden of FUS pathology."

Post-mortem CNS analysis in treated patients demonstrates jacifusen lowers FUS protein and FUS-aggregate burden, the intended target-engagement readout in humans.

PMID:35075293 SUPPORT Model organism

"ION363, a non-allele-specific FUS antisense oligonucleotide, efficiently silences Fus and reduces postnatal levels of FUS protein in the brain and spinal cord, delaying motor neuron degeneration."

Preclinical FUS knock-in mouse study establishes that ION363 silences Fus and delays motor neuron degeneration, the model-organism basis for the human program.

Triumeq

Action: Pharmacotherapy NCIT:C15986

Agent: abacavir/dolutegravir/lamivudine NCIT:C157543

Antiretroviral therapy (combination of dolutegravir, lamivudine, and abacavir) proposed for treating TDP-43-associated ALS through modulation of endogenous retroviruses. In preclinical models, Triumeq transiently and modestly improves early motor function without impacting overall disease progression, and reduces TDP-43-driven neuroinflammation via suppression of transcription factor ATF4 and inflammatory markers CXCL10 and IRF-1.

Mechanism Target:

INHIBITS Endogenous Retrovirus Reactivation and TDP-43 Feedback — Triumeq's antiretroviral components (the integrase inhibitor dolutegravir plus the reverse-transcriptase inhibitors abacavir and lamivudine) target the ERV (HERV-K) reactivation arm of the ERV-TDP-43 feedback loop.

INHIBITS Neuroinflammation — Triumeq suppresses TDP-43-driven inflammatory gene expression in the ALS neuroinflammation axis, including ATF4, CXCL10, and IRF-1.

Show evidence (1 reference)

PMID:42204279 SUPPORT Model organism

"In this TDP-43 ALS mouse model, there was a positive association of TDP-43 mRNA levels with transcription factor ATF4, and inflammatory markers CXCL10 and IRF-1, and Triumeq treatment negated this association."

Triumeq negated TDP-43-associated inflammatory marker upregulation, linking the treatment to inhibition of the Neuroinflammation pathophysiology node.

Show evidence (2 references)

PMID:42204279 SUPPORT Model organism

"Triumeq treatment significantly improved motor function early on in the disease course"

Preclinical study shows early motor function improvement in the TDP-43 ALS mouse model, but the abstract qualifies the effect as transient and modest with no impact on other progression markers or disease endpoint.

PMID:42204279 SUPPORT Model organism

Triumeq modulates TDP-43-driven neuroinflammation by suppressing ATF4 and inflammatory cytokines in disease model.

Sodium Phenylbutyrate-Taurursodiol (AMX0035)

Action: Pharmacotherapy NCIT:C15986

Agent: sodium phenylbutyrate CHEBI:75316 tauroursodeoxycholic acid CHEBI:80774

Fixed-dose combination of sodium phenylbutyrate and taurursodiol (tauroursodeoxycholic acid) intended to reduce endoplasmic-reticulum and mitochondrial stress-mediated motor neuron death, marketed as Relyvrio (US) / Albrioza (Canada). The phase 2 CENTAUR trial showed slower functional decline, supporting accelerated FDA approval in 2022, but the confirmatory phase 3 PHOENIX trial showed no benefit at 48 weeks and the sponsor voluntarily withdrew the drug from the market in 2024. Included here to document a withdrawn ALS therapy whose disease-modifying benefit was not confirmed.

Show evidence (3 references)

PMID:32877582 SUPPORT Human clinical

"the mean rate of change in the ALSFRS-R score was -1.24 points per month with the active drug and -1.66 points per month with placebo (difference, 0.42 points per month; 95% confidence interval, 0.03 to 0.81; P = 0.03)."

The phase 2 CENTAUR randomized controlled trial showed a statistically significant slowing of ALSFRS-R functional decline versus placebo — the result that supported the 2022 accelerated FDA approval.

PMID:38909349 REFUTE Human clinical

"results from the Phase 3 PHOENIX trial (NCT05021536) showed no change in ALSFRS-R total score at 48 weeks."

The confirmatory phase 3 PHOENIX trial found no effect on the primary functional endpoint, refuting a disease-modifying benefit and reversing the CENTAUR signal.

PMID:38909349 REFUTE Human clinical

"the sponsor company initiated the process with the US FDA and Health Canada to voluntarily withdraw the marketing authorizations for PB-TUDCA."

Following the negative PHOENIX trial, the sponsor voluntarily withdrew marketing authorizations in the US and Canada (2024), documenting the therapy's removal from clinical use.

Non-invasive Ventilation

Action: noninvasive ventilation Ontology label: Non-Invasive Mechanical Ventilation NCIT:C171457

Respiratory support using BiPAP or similar devices to assist breathing as respiratory muscles weaken. This improves quality of life and extends survival.

Show evidence (2 references)

PMID:16426990 SUPPORT

"This subgroup showed improvement in several measures of quality of life and a median survival benefit of 205 days (p=0.006) with maintained quality of life for most of this period."

Randomized controlled trial demonstrated non-invasive ventilation improves quality of life and extends survival in ALS patients with preserved bulbar function.

PMID:39019674 SUPPORT Human clinical

"Non-invasive ventilation (NIV), which is the main recognized treatment for alleviating the symptoms of respiratory failure, prolongs survival and improves quality of life."

The French expert-panel respiratory-care guideline affirms non-invasive ventilation as the main recognized treatment for ALS respiratory failure, prolonging survival and improving quality of life.

Physical Therapy

Action: Physical Therapy NCIT:C15302

Platform: Behavioral / lifestyle

Range of motion exercises and adaptive strategies to maintain function and prevent complications such as contractures.

Show evidence (1 reference)

PMID:24510737 SUPPORT

"Multidisciplinary care includes rehabilitation interventions that have the goal of assisting people to teach their fullest potential despite the presence of a disabling disease."

Review describes how rehabilitation including physical therapy helps maximize independence and function in ALS patients.

Speech Therapy

Action: speech therapy Ontology label: Speech Language Therapy NCIT:C159273

Platform: Behavioral / lifestyle

Techniques to optimize communication and swallowing safety, including augmentative and alternative communication devices.

Show evidence (1 reference)

PMID:24510737 SUPPORT

"This review will present rehabilitation strategies that can be utilized to maximize patient independence, function, safety, and quality of life, and to minimize disease-related symptoms."

Review covers multidisciplinary rehabilitation including speech therapy for ALS patients.

Percutaneous Endoscopic Gastrostomy

Action: Percutaneous Endoscopic Gastrostomy NCIT:C106040

Feeding tube placement to maintain nutrition when swallowing becomes unsafe or inadequate due to bulbar involvement.

Show evidence (1 reference)

PMID:39207520 SUPPORT

"Early discussion of potential treatments such as high-calorie diets or percutaneous endoscopic gastrostomy (PEG) is crucial."

Dysphagia management review underscores PEG as an essential intervention when nutrition is compromised in ALS.

Multidisciplinary Care

Action: supportive care Ontology label: Supportive Care NCIT:C15747

Coordinated care from neurologists, pulmonologists, physical therapists, occupational therapists, speech therapists, nutritionists, and palliative care specialists extends survival and improves quality of life.

Show evidence (1 reference)

PMID:24510737 SUPPORT

"Multidisciplinary care includes rehabilitation interventions that have the goal of assisting people to teach their fullest potential despite the presence of a disabling disease."

Rehabilitation review emphasizes multidisciplinary care as core to ALS management to optimize function and quality of life.

🌍

Environmental Factors

Heavy Metal Exposure

Occupational and environmental exposure to lead, cadmium, mercury, and other heavy metals has been associated with increased ALS risk. Prospective pre-diagnostic blood-metal data (which minimize reverse causation) implicate cadmium and lead, with zinc inversely associated.

Show evidence (2 references)

PMID:31578652 SUPPORT Human clinical

"The ratio of maximal/minimal lead exposure yielded a pooled odds ratio (OR) of 1.46 (95% confidence interval (CI) 1.16-1.83) with moderate heterogeneity (I2 = 51.8%; p = 0.019)."

Meta-analysis finds lead exposure positively associated with ALS risk across population-based studies.

PMID:33068316 SUPPORT Human clinical

"cadmium and lead may be associated with an increased risk of ALS and zinc with a decreased risk. This is the first study to evaluate predisease metal levels in blood, thus minimizing reverse causation."

Nested case-control study in the prospective EPIC cohort measured pre-diagnostic blood metals, implicating cadmium and lead (and protective zinc) with a design that minimizes reverse causation. Identified as an un-integrated finding from the ALS environmental-toxicity deep-research report.

Mechanism Target:

PREDISPOSES Motor Neuron Degeneration — Lead and cadmium are the most consistently implicated exposures, plausibly acting through oxidative stress, but no step between exposure and motor neuron loss is established. The effect size is modest and no environmental cause of this disease is proven.

Show evidence (1 reference)

PMID:31578652 SUPPORT Human clinical

"The ratio of maximal/minimal lead exposure yielded a pooled odds ratio (OR) of 1.46 (95% confidence interval (CI) 1.16-1.83) with moderate heterogeneity (I2 = 51.8%; p = 0.019)."

Reports a pooled odds ratio of 1.46 comparing maximal with minimal lead exposure, an epidemiological association of modest size.

Pesticide Exposure

Agricultural pesticide exposure has been linked to increased ALS incidence in epidemiological studies.

Show evidence (1 reference)

PMID:22521219 SUPPORT

"In the meta-analysis, ALS was associated with use of pesticides as a group (1.9, 1.1-3.1)."

Systematic review and AHS cohort analysis report elevated ALS odds with pesticide exposure.

Mechanism Target:

PREDISPOSES Motor Neuron Degeneration — Pesticides are analysed as a class rather than as specific compounds, so the association cannot identify a responsible agent, let alone a mechanism.

Show evidence (1 reference)

PMID:22521219 SUPPORT Human clinical

"In the meta-analysis, ALS was associated with use of pesticides as a group (1.9, 1.1-3.1)."

Reports an odds ratio of 1.9 for pesticides analysed as a group, an association at class level rather than for any identified compound.

Military Service

Veterans have approximately twice the risk of developing ALS compared to the general population, possibly related to environmental exposures.

Show evidence (1 reference)

PMID:14504315 SUPPORT

"A significant elevated risk of ALS occurred among all deployed personnel (RR = 1.92; 95% CL = 1.29, 2.84)"

Gulf War veteran cohort showed nearly twofold higher ALS risk compared with non-deployed personnel.

Mechanism Target:

PREDISPOSES Motor Neuron Degeneration — A setting rather than an exposure, bundling possible chemical, physical and traumatic contributions that the epidemiology cannot separate.

Show evidence (1 reference)

PMID:14504315 SUPPORT Human clinical

"A significant elevated risk of ALS occurred among all deployed personnel (RR = 1.92; 95% CL = 1.29, 2.84)"

Reports a relative risk of 1.92 among all deployed personnel, an association with the setting rather than with any identified exposure within it.

Smoking

Cigarette smoking is the most consistently reported environmental ALS risk factor, though the overall association is modest; in this meta-analysis the clearest signal is a sex-specific increased risk in women (ever-smoker RR 1.66, 95% CI 1.31-2.10), while the overall pooled estimates were not statistically significant.

Show evidence (2 references)

PMID:20639382 SUPPORT Human clinical

"The pooled RR (95% CI) of ALS was 1.28 (0.97 to 1.68) for current versus never smokers and 1.12 (0.98 to 1.27) for ever versus never smokers."

Meta-analysis of case-control and cohort studies found overall pooled relative risks that were elevated but not statistically significant (confidence intervals crossing 1.0), providing only partial support for smoking as an ALS risk factor.

PMID:20639382 SUPPORT Human clinical

"was 0.86 (0.71 to 1.03) in men and 1.66 (1.31 to 2.10) in women."

Sex-stratified analysis shows a statistically significant elevated ALS risk in women who ever smoked (RR 1.66, 95% CI 1.31-2.10) but not in men, supporting the sex-specific smoking-ALS association.

Mechanism Target:

PREDISPOSES Motor Neuron Degeneration — The weakest of the exposures here and sex-dependent: the association in men is null while in women it is clear. The sex-specific figures are meta-regression predicted values rather than directly pooled sex-stratified estimates. Recorded because the sex difference is itself informative, not because smoking is established as a cause.

Show evidence (1 reference)

PMID:20639382 SUPPORT Human clinical

"was 0.86 (0.71 to 1.03) in men and 1.66 (1.31 to 2.10) in women."

Gives meta-regression predicted relative risks of 0.86 in men and 1.66 in women, an association present only in women. Support is PARTIAL because these are modelled rather than directly pooled values, and the pooled current-versus-never estimate does not exclude no effect.

Repetitive Head Trauma and Contact Sports

Repetitive concussive head and cervical-spinal trauma, particularly from professional contact sports (American football, soccer/association football, boxing), is associated with a markedly increased risk of ALS; head trauma is also an independent risk factor in broad risk-factor meta-analyses. The association overlaps the trauma-driven TDP-43 proteinopathy seen in chronic traumatic encephalopathy.

Show evidence (2 references)

PMID:30775214 SUPPORT Human clinical

"repetitive concussive head and cervical spinal trauma result in an increased risk of ALS compared with the general population or nonsport controls."

Systematic review concludes that contact sports involving repetitive concussive head and cervical-spinal trauma increase ALS risk (with a pooled rate ratio of 8.52 for professional such sports). Identified as an un-integrated finding from the ALS environmental-toxicity deep-research report.

PMID:37284659 SUPPORT Human clinical

"head trauma (OR = 1.26, 95% CI = 1.13, 1.40)"

Comprehensive observational meta-analysis identifies head trauma as an independent risk factor for ALS, corroborating the contact-sports signal.

Mechanism Target:

PREDISPOSES Motor Neuron Degeneration — Repeated head and cervical trauma is associated with a modestly raised risk. Reverse causation is a genuine concern here, since early motor impairment may itself increase falls and injury.

Show evidence (1 reference)

PMID:37284659 SUPPORT Human clinical

"head trauma (OR = 1.26, 95% CI = 1.13, 1.40)"

Reports an odds ratio of 1.26 for head trauma, a modest association.

🔬

Biochemical Markers

Neurofilament Light Chain (NfL) (Elevated)

Context: CSF and serum biomarker of axonal injury, elevated in ALS with prognostic value

Show evidence (3 references)

PMID:32385188 SUPPORT Human clinical

"Baseline serum NfL concentration, but not pNfH, predicted the future Revised ALS Functional Rating Scale (ALSFRS-R) slope and survival."

Prospective multicentre cohort establishing serum NfL as a prognostic marker of functional decline and survival in ALS.

PMID:32385188 SUPPORT Human clinical

"Serum NfL may be considered a clinically validated prognostic biomarker for ALS. Serum NfL (and perhaps pNfH), quantified using the Simoa assay, has potential utility as a pharmacodynamic biomarker of treatment effect."

The authors' own conclusion, and the basis for recording NfL as a marker used for prognosis and for monitoring therapeutic response in trials.

PMID:36129998 SUPPORT Human clinical

"Tofersen led to greater reductions in concentrations of SOD1 in CSF and of neurofilament light chains in plasma than placebo."

The VALOR phase 3 trial shows plasma neurofilament light chain falls with SOD1-lowering therapy, validating NfL as a pharmacodynamic biomarker of axonal injury that tracks treatment response in ALS.

Phosphorylated Neurofilament Heavy Chain (pNfH) (Elevated)

Context: CSF and serum biomarker of axonal injury

Skeletal Myocyte Plasma Proteomic Age Gap (Elevated)

Context: Blood-based cell-type-specific aging clock. Plasma proteins are mapped to their putative cell of origin using Human Protein Atlas single-cell transcriptomic data, and a machine-learning model estimates skeletal myocyte biological age; the age gap is the difference between that estimate and chronological age. "Extreme" agers are those in the upper tail of the age-gap distribution and "youthful" agers the lower tail.

Pathograph Readouts

Predicts Motor Neuron Degeneration Positive Prognostic

An elevated skeletal myocyte age gap predicts incident ALS years before diagnosis and is read here as a peripheral plasma correlate of the motor-neuron-degeneration axis and its downstream denervation, rather than as an independent muscle-intrinsic disease process.

Show evidence (1 reference)

PMID:42297981 SUPPORT Human clinical

"extreme skeletal myocyte aging demonstrated pronounced prognostic power for incident ALS over 15 years of follow-up in the UKB cohort, even for cases diagnosed more than 3 years after baseline assessment, suggesting potential for presymptomatic detection"

Supports a presymptomatic prognostic readout and addresses the reverse-causation objection by restricting to cases diagnosed well after the blood draw.

Show evidence (3 references)

PMID:42297981 SUPPORT Human clinical

"Individuals with extremely aged compared to youthful skeletal myocytes exhibited a 12.7-fold higher risk of developing amyotrophic lateral sclerosis."

Quantifies the prognostic association between the skeletal myocyte plasma proteomic age gap and incident ALS over 15 years of UK Biobank follow-up (reported as HR 12.74 in the results text).

PMID:42297981 SUPPORT Human clinical

"The strongest association among all disease-cell type pairs was between ALS and skeletal myocyte aging"

Establishes that this is the most prominent cell-type/disease association in the study, not one signal among many comparable ones.

PMID:42297981 SUPPORT Human clinical

"53 of 57 (93.0%) skeletal myocyte extreme agers had an ALS diagnosis."

Cross-sectional case/control concentration of extreme skeletal myocyte agers among ALS patients in the GNPC ALS cohort (n = 355; 245 patients, 110 controls), independent of the UK Biobank incident analysis.

Cardiomyocyte Plasma Proteomic Age Gap (Elevated)

Context: Blood-based cell-type-specific aging clock (see Skeletal Myocyte Plasma Proteomic Age Gap for the derivation). Curated as a cross-sectional correlate of prevalent ALS, deliberately NOT as a prognostic marker for incident disease.

Show evidence (4 references)

PMID:42297981 SUPPORT Human clinical

"along with skeletal myocytes, we observed that cardiomyocytes showed accelerated aging in patients with ALS"

Establishes the cross-sectional association with prevalent ALS in the GNPC cohort, which is the arm this marker is curated on.

PMID:42297981 SUPPORT Human clinical

"patients with ALS exhibited pronounced acceleration of skeletal myocyte aging and cardiomyocyte aging across chronological age span"

LOWESS analysis showing the acceleration is present across the chronological age range rather than confined to older patients.

PMID:42297981 NO_EVIDENCE Human clinical

"We observed similar risk stratification for cardiomyocyte aging and incident ALS"

This sentence concerns incident ALS, which this marker deliberately does not claim (see context), so it does not bear on the cross-sectional claim. It also asserts prognostic parity with the skeletal myocyte clock that the paper's own log-rank test does not show (P = 0.0562 for cardiomyocyte aging). Kept so the gap between the paper's narrative and its statistic is visible to the next curator rather than silently inherited.

+ 1 more reference

📊

Prevalence

Europe

Point prevalence 1.0–9.0 per 100,000 1–9 per 100,000

Orphanet European point-prevalence class 1-9 / 100,000 (band-only source; no point estimate reported).

Show evidence (1 reference)

ORPHA:803 SUPPORT

"1-9 / 100 000 | Europe | Point prevalence | PMID:19192301,EXPERT"

Orphanet epidemiology table reports a European point prevalence of 1-9 per 100,000.

Europe

Annual incidence 1.0–9.0 per 100,000 1–9 per 100,000 per year

Orphanet European annual-incidence class 1-9 / 100,000 (band-only source; no point estimate reported).

Show evidence (1 reference)

ORPHA:803 SUPPORT

"1-9 / 100 000 | Europe | Annual incidence | PMID:19710046,EXPERT"

Orphanet epidemiology table reports a European annual incidence of 1-9 per 100,000.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from Amyotrophic Lateral Sclerosis:

Chronic Inflammatory Demyelinating Polyradiculoneuropathy MONDO:0006702

Overlapping Features Immune-mediated demyelinating neuropathy causing progressive symmetric weakness and sensory loss; may mimic lower motor neuron-predominant ALS.

Show evidence (1 reference)

PMID:33085325 SUPPORT

"Some disorders that can mimic motor neuron disease are multifocal motor neuropathy with conduction block, chronic inflammatory demyelinating polyradiculoneuropathy, central nervous system tumors, multiple sclerosis, and polyradiculopathy, among others."

StatPearls review lists CIDP among conditions that can mimic ALS and should be ruled out.

Multiple Sclerosis MONDO:0005301

Overlapping Features Demyelinating disease of the central nervous system with motor weakness and spasticity that can resemble early ALS presentations.

Show evidence (1 reference)

PMID:33085325 SUPPORT

The same review identifies multiple sclerosis as a diagnostic mimic of motor neuron disease.

Multifocal Motor Neuropathy Not Yet Curated MONDO:0018979

Overlapping Features Immune-mediated, asymmetric, distal motor neuropathy with conduction block that can present with focal weakness mimicking lower motor neuron ALS.

Show evidence (1 reference)

PMID:33085325 SUPPORT

StatPearls review lists multifocal motor neuropathy with conduction block as an ALS mimic that must be ruled out.

📊

Related Datasets

GTEx v8 Spinal Cord (cervical c-1) gtex:GTEx_v8_Spinal_cord_cervical_c-1

Bulk RNA-seq from healthy cervical spinal cord to provide baseline expression for upper and lower motor neuron pathways affected in ALS.

Homo sapiens BULK RNA SEQ

spinal cord UBERON:0002240

PMID:32913098

Show evidence (1 reference)

PMID:32913098 SUPPORT Human clinical

"Here, we present analyses of the version 8 data, examining 15,201 RNA-sequencing samples from 49 tissues of 838 postmortem donors."

Identifies GTEx v8, the postmortem cross-tissue RNA-seq release this healthy cervical spinal cord reference is drawn from. It attests the dataset rather than any ALS finding.

GTEx v8 Skeletal Muscle gtex:GTEx_v8_Skeletal_Muscle

Bulk RNA-seq from healthy skeletal muscle to benchmark ALS-related denervation signatures and muscle atrophy pathways.

Homo sapiens BULK RNA SEQ

skeletal muscle tissue UBERON:0001134

PMID:32913098

Show evidence (1 reference)

PMID:32913098 SUPPORT Human clinical

"Here, we present analyses of the version 8 data, examining 15,201 RNA-sequencing samples from 49 tissues of 838 postmortem donors."

Identifies GTEx v8, the postmortem cross-tissue RNA-seq release this healthy skeletal muscle reference is drawn from. It attests the dataset rather than any ALS finding.

🐁

Animal Models

Canine degenerative myelopathy (SOD1 E40K homozygous dog)

Canine degenerative myelopathy (DM) is a naturally occurring, adult-onset, fatal neurodegenerative disease caused by homozygosity for the SOD1 c.118G>A (p.E40K) missense mutation, identified across five breeds. Progressive upper motor neuron spastic ataxia in the pelvic limbs typically begins at 8 years or older, ascending to flaccid tetraparesis if euthanasia is delayed. Spinal cord histology reveals myelin and axon loss in the lateral white matter and neuronal cytoplasmic SOD1-immunoreactive inclusions mirroring human ALS pathology. This is the first recognized spontaneously occurring animal model for ALS.

Species

Dog

Genotype

SOD1 c.118G>A (p.E40K) homozygous

Background

Pembroke Welsh Corgi, Boxer, Rhodesian Ridgeback, German Shepherd Dog, Chesapeake Bay Retriever

Publication

PMID:19188595

Pathograph links

Motor Neuron Degeneration recapitulates fidelity: moderate Naturally occurring, adult-onset SOD1-associated degeneration of the spinal cord, with neuronal cytoplasmic SOD1-immunoreactive inclusions matching those of human SOD1-ALS.

Limitations: E40K is not among the SOD1 alleles that cause human ALS, and DM presents as an ascending spinal myelopathy beginning with pelvic-limb upper motor neuron signs rather than the focal limb or bulbar onset typical of human ALS. Disease-course and therapeutic inferences should not be transferred without corroboration in human tissue.

Readouts

Lateral white matter myelin and axon content

Spinal cord histology in affected dogs, scored against unaffected controls of the same breeds.

Direction: DECREASED

Interpretation: Myelin and axon loss confined to the lateral white matter is the structural correlate of the degeneration node in this model.

Show evidence (1 reference)

PMID:19188595 SUPPORT Model organism

"Microscopic examination of spinal cords from affected dogs revealed myelin and axon loss affecting the lateral white matter"

Awano et al. report the histological measurement underlying this readout.

SOD1-immunoreactive neuronal cytoplasmic inclusions

Anti-SOD1 immunohistochemistry of spinal cord sections from affected dogs.

Direction: INCREASED

Interpretation: Inclusion pathology is what ties this model to human SOD1-ALS rather than to non-specific myelopathy; the authors compare it directly against human ALS spinal cord.

Show evidence (1 reference)

PMID:19188595 SUPPORT Model organism

"These inclusions are similar to those seen in spinal cord sections from ALS patients with SOD1 mutations."

Establishes correspondence between the model's inclusion pathology and human SOD1-ALS.

Show evidence (1 reference)

PMID:19188595 SUPPORT Model organism

"Our findings identify canine DM to be the first recognized spontaneously occurring animal model for ALS."

Supports treating this model as informative for the motor neuron degeneration node.

Show evidence (1 reference)

PMID:19188595 SUPPORT Model organism

"Our findings identify canine DM to be the first recognized spontaneously occurring animal model for ALS."

Awano et al. 2009 identified the SOD1 E40K mutation in DM-affected dogs by genome-wide association mapping and demonstrated SOD1-immunoreactive cytoplasmic inclusions similar to human ALS pathology, formally establishing canine DM as the first spontaneous large-animal ALS model.

Equine motor neuron disease (vitamin E-deficient horse)

Equine motor neuron disease (EMND) is a naturally occurring, acquired lower motor neuron disease of adult horses linked to chronic vitamin E deficiency and oxidative stress, arising in horses stabled without access to pasture. Clinical signs include progressive weight loss, muscle fasciculations, constant weight shifting in the rear limbs, abnormally low head carriage, and excessive recumbency. Pathological findings include type 1 muscle fibre atrophy and lipopigment accumulation in spinal cord capillary endothelium. Unlike classic ALS, which requires combined upper and lower motor neuron degeneration, EMND involves predominantly lower motor neurons (no upper motor neuron involvement), limiting direct phenotypic equivalence to human ALS.

Species

Horse

Genotype

acquired (vitamin E deficiency / chronic oxidative stress)

Publication

PMID:7988544

Pathograph links

Motor Neuron Degeneration partially recapitulates fidelity: low Adult-onset degeneration of lower motor neurons with denervation muscle pathology, arising spontaneously under chronic nutritional oxidative stress.

Limitations: EMND involves predominantly lower motor neurons with no upper motor neuron involvement, so it does not reproduce the combined upper and lower motor neuron degeneration that defines human ALS. It is also acquired and nutritional rather than genetic, so it carries no information about the familial ALS genotypes.

Readouts

Type 1 muscle fibre atrophy

Muscle histopathology in affected horses at post mortem.

Direction: INCREASED

Interpretation: Denervation atrophy is the downstream muscle correlate of lower motor neuron loss, and is the readout that supports the partial rather than full correspondence to ALS.

Show evidence (1 reference)

PMID:7988544 SUPPORT Model organism

"preference of type 1 muscle fibre atrophy"

Divers et al. report type 1 fibre atrophy as a consistent pathological finding across all cases.

Show evidence (1 reference)

PMID:2209016 SUPPORT Model organism

"Pathologic studies revealed that degeneration and loss of motor neurons in the spinal cord and brain stem resulted in axonal degeneration in the ventral roots and peripheral and cranial nerves and denervation atrophy of skeletal muscle."

The first pathological description of EMND reports degeneration and loss of spinal and brainstem motor neurons with denervation atrophy. These are lower motor neuron populations only, which is why the link is a partial recapitulation of the human degeneration node.

Oxidative Stress recapitulates fidelity: low Chronic vitamin E deficiency is proposed to produce a sustained oxidative insult to motor neurons, giving a naturally occurring model of the oxidative stress node that is separable from any genetic lesion.

Limitations: The oxidative insult here is nutritional; it is a model of oxidative stress as a sufficient cause of motor neuron injury, not of the SOD1- or TDP-43-driven oxidative stress seen in human ALS. The oxidative mechanism is itself inferred: the cited studies support it with a histological marker (endothelial lipopigment), case-control dietary risk factors, and uncontrolled improvement after pasture access, and frame it as a hypothesis rather than as a measured oxidative-damage readout.

Readouts

Spinal cord capillary endothelial lipopigment accumulation

Lipopigment deposition in spinal cord capillary endothelium at post mortem, the histological marker the authors read as oxidative injury.

response to oxidative stress GO:0006979

Direction: INCREASED

Interpretation: Present in all cases, and the basis on which the authors classify EMND as an oxidative disease.

Show evidence (1 reference)

PMID:7988544 SUPPORT Model organism

"lipopigment accumulation within the capillary endothelium of the spinal cord of all cases, supported the hypothesis of EMND being an oxidative disease"

Directly reports the readout and the oxidative interpretation.

Clinical status after pasture access and vitamin E supplementation

Observational rescue arm: five affected horses were followed for 9 months to over 2 years after onset with pasture access, two also receiving supplemental vitamin E.

Direction: RESTORED

Interpretation: Improvement on removal of the oxidative insult is the strongest evidence that the deficiency is driving the node rather than accompanying it. It is observational and uncontrolled, and only the more acutely affected horses improved.

Show evidence (1 reference)

PMID:7988544 SUPPORT Model organism

"Marked clinical improvement occurred in the 4 more acutely affected horses."

Reports the rescue observation. The arm is uncontrolled, involves five horses, and combines two interventions, so it supports the direction of the readout only weakly.

Show evidence (1 reference)

PMID:9373362 SUPPORT Model organism

"The relationship of specific nutritional factors to EMND supports the hypothesis that a deficiency of vitamin E contributes to the disease."

Case-control epidemiology in 87 affected and 259 control horses supports the oxidative-stress basis of this model.

Show evidence (2 references)

PMID:7988544 SUPPORT Model organism

"Pathological findings, preference of type 1 muscle fibre atrophy and lipopigment accumulation within the capillary endothelium of the spinal cord of all cases, supported the hypothesis of EMND being an oxidative disease."

Divers et al. 1994 described the clinical and pathological features of EMND in 28 horses and proposed oxidative stress as the pathophysiological mechanism, establishing this naturally occurring condition as a motor neuron disease analog.

PMID:9373362 SUPPORT Model organism

"The relationship of specific nutritional factors to EMND supports the hypothesis that a deficiency of vitamin E contributes to the disease."

de la Rúa-Domènech et al. 1997 identified vitamin E deficiency as a key risk factor for EMND in a case-control study of 87 affected horses and 259 controls, reinforcing the oxidative stress pathophysiology.

TDP-43(Q331K) transgenic mouse (senescence and senolytic arm)

Transgenic ALS mouse carrying the TDP-43(Q331K) allele, used to time cellular senescence relative to functional decline and to test whether clearing senescent cells alters the course. Senescence markers appear in motor cortex and spinal cord alongside declining neural and neuromuscular function, and longitudinal senolytic treatment with dasatinib and quercetin improved motor behaviour and neuromuscular function, reduced plasma neurofilament light chain, and preserved layer V neuron counts.

Species

Mouse

Genotype

TDP-43(Q331K)

Publication

PMID:42759848

Pathograph links

Cellular Senescence in Motor Cortex and Spinal Cord recapitulates fidelity: moderate observes: cellular The model is where this node's claim comes from - senescence markers in motor cortex and spinal cord, early relative to functional decline - and the senolytic arm is what makes the senescence modifiable rather than incidental.

Limitations: One allele in one species: TDP-43(Q331K) mice say nothing about senescence in SOD1- or C9orf72-associated ALS, and nothing about sporadic disease, which is the majority of human cases. The senolytic arm shows that clearing senescent cells changes outcomes, not which cells were cleared; cortical microglia are a candidate mediator inferred from reduced microglial TDP-43 burden and senescence markers, not a demonstrated one. Dasatinib and quercetin are given together, so neither agent's contribution is separable.

Readouts

Senescence marker expression in motor cortex and spinal cord

Direction: INCREASED

Interpretation: The measurement the node rests on, in the two regions ALS degeneration affects.

Show evidence (1 reference)

PMID:42759848 SUPPORT Model organism

Reports the marker measurement and its anatomical location.

Plasma neurofilament light chain under senolytic treatment

Direction: DECREASED

Interpretation: Axonal damage marker falling when senescent cells are cleared, which is the result that makes the senescence modifiable. It reports axonal damage rather than senescence itself.

Show evidence (1 reference)

PMID:42759848 SUPPORT Model organism

"D&Q treatment improved motor behavior, neuromuscular function, and reduced axonal damage as measured by plasma neurofilament light chain, accompanied by robust improvements in motor cortex excitability and preservation of layer V neuron counts"

Reports the senolytic arm's outcome measures, including the plasma NfL reduction.

Show evidence (1 reference)

PMID:42759848 SUPPORT Model organism

Supports treating this model as informative for the senescence node: the markers are localized to the same regions and precede functional decline.

{ }

Source YAML

click to show

name: Amyotrophic Lateral Sclerosis
creation_date: '2026-01-14T23:47:09Z'
category: Complex
description: >
  Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a progressive
  neurodegenerative disorder characterized by the selective death of upper and lower motor
  neurons in the brain, brainstem, and spinal cord. This leads to progressive muscle weakness,
  atrophy, spasticity, and ultimately respiratory failure. ALS typically presents in adulthood
  with a median survival of 3-5 years from symptom onset. Approximately 5-10% of cases are
  familial, with the remainder being sporadic. A hallmark feature is TDP-43 proteinopathy,
  present in approximately 97% of cases.
disease_term:
  preferred_term: amyotrophic lateral sclerosis
  term:
    id: MONDO:0004976
    label: amyotrophic lateral sclerosis
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
  mechanistic_category:
  - classification_value: proteotoxic disease
gene_sets:
- gene_set: MYGENESET:KEGG_AMYOTROPHIC_LATERAL_SCLEROSIS_ALS
  relationship: CANONICAL_PATHWAY
  note: >-
    KEGG amyotrophic lateral sclerosis pathway.
- gene_set: MYGENESET:WP_AMYOTROPHIC_LATERAL_SCLEROSIS_ALS
  relationship: CANONICAL_PATHWAY
  note: >-
    WikiPathways amyotrophic lateral sclerosis pathway.
parents:
- Motor Neuron Disease
- Neurodegenerative Disease
has_subtypes:
- name: Familial ALS
  description: Hereditary form of ALS accounting for 5-10% of cases, with mutations in genes such as SOD1, C9orf72, TARDBP, and FUS.
  evidence:
  - reference: PMID:21857683
    reference_title: "Mutations in UBQLN2 cause dominant X-linked juvenile and adult-onset ALS and ALS/dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Most cases of ALS are sporadic but about 5-10% are familial."
    explanation: >
      Source for the 5-10% familial share stated in this row, which was
      previously uncited.
- name: Sporadic ALS
  description: Non-hereditary form of ALS accounting for 90-95% of cases with unclear etiology.
- name: Bulbar-onset ALS
  description: ALS beginning with speech and swallowing difficulties due to bulbar motor neuron involvement.
- name: Limb-onset ALS
  description: ALS beginning with limb weakness, the most common presentation.
# Gene-defined subtypes. The four rows above classify ALS on two clinical axes
# (heritability and site of onset); the rows below classify it on the genetic
# axis, one row per MONDO gene-defined locus that descends from MONDO:0004976
# via MONDO:0005144 "familial amyotrophic lateral sclerosis". The numbered ALS /
# FTDALS designations are MONDO's and OMIM's, taken from each term's own label
# and OMIM xref; the cited papers establish the gene-disease relationship. Two
# rows (ALS26, ALS28) record published challenges to that relationship and are
# graded accordingly. SOD1 (ALS1) has no row here because it is curated as a
# separate entry, Amyotrophic_Lateral_Sclerosis_Type_1 (MONDO:0007103).
- name: ALS6
  display_name: ALS6 (FUS, autosomal dominant)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 6
    term:
      id: MONDO:0011951
      label: amyotrophic lateral sclerosis type 6
  genes:
  - preferred_term: FUS
    term:
      id: hgnc:4010
      label: FUS
  description: >
    ALS caused by mutations in FUS, an RNA-binding protein with functional homology
    to TDP-43. The neuropathology departs from the TDP-43 proteinopathy that
    defines most of this entry: FUS-mutant cases carry FUS-immunoreactive
    cytoplasmic inclusions with predominantly lower motor neuron degeneration.
  review_notes: >
    kb/disorders/Juvenile_Amyotrophic_Lateral_Sclerosis.yaml carries an
    "ALS6-JALS" subtype row that deliberately does NOT bind MONDO:0011951, on the
    grounds that ALS6 is a gene-level concept covering FUS-ALS at any age, mostly
    adult-onset, which MONDO parents under familial ALS rather than under JALS.
    This row is the adult, gene-level home that reasoning points at; the two
    entries are complementary, and the juvenile-onset p.P525L variant-level
    phenomenon stays in the JALS entry.
  evidence:
  - reference: PMID:19251628
    reference_title: "Mutations in FUS, an RNA processing protein, cause familial amyotrophic lateral sclerosis type 6."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We have identified a missense mutation in the gene encoding fused in sarcoma (FUS) in a British kindred, linked to ALS6."
    explanation: >
      Ties FUS directly to the ALS6 locus designation that MONDO:0011951 denotes.
  - reference: PMID:19251628
    reference_title: "Mutations in FUS, an RNA processing protein, cause familial amyotrophic lateral sclerosis type 6."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Postmortem analysis of three cases with FUS mutations showed FUS-immunoreactive cytoplasmic inclusions and predominantly lower motor neuron degeneration."
    explanation: >
      Source for describing FUS-ALS neuropathology as FUS-inclusion rather than
      TDP-43 pathology.
  - reference: PMID:19251628
    reference_title: "Mutations in FUS, an RNA processing protein, cause familial amyotrophic lateral sclerosis type 6."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "FUS is involved in the regulation of transcription and RNA splicing and transport, and it has functional homology to another ALS gene, TARDBP, which suggests that a common mechanism may underlie motor neuron degeneration."
    explanation: >
      Source for the statement that FUS is functionally homologous to TDP-43.
- name: ALS8
  display_name: ALS8 (VAPB, autosomal dominant)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 8
    term:
      id: MONDO:0012077
      label: amyotrophic lateral sclerosis type 8
  genes:
  - preferred_term: VAPB
    term:
      id: hgnc:12649
      label: VAPB
  description: >
    ALS from a founder missense change in VAPB. The same allele produces a
    spectrum rather than one phenotype: atypical ALS8, late-onset spinal muscular
    atrophy, and typical rapidly progressive ALS have all been reported in
    carriers, in kindreds that could not all be linked but that share a haplotype.
  evidence:
  - reference: PMID:15372378
    reference_title: "A mutation in the vesicle-trafficking protein VAPB causes late-onset spinal muscular atrophy and amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report the finding of a novel missense mutation in the vesicle-associated membrane protein/synaptobrevin-associated membrane protein B (VAPB) gene in patients from this family."
    explanation: >
      Identifies VAPB as the gene at the previously mapped ALS8 locus,
      establishing the gene-disease relationship for this subtype.
  - reference: PMID:15372378
    reference_title: "A mutation in the vesicle-trafficking protein VAPB causes late-onset spinal muscular atrophy and amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Subsequently, the same mutation was identified in patients from six additional kindreds but with different clinical courses, such as ALS8, late-onset SMA, and typical severe ALS with rapid progression."
    explanation: >
      Source for the statement that one VAPB allele spans several motor neuron
      disease presentations.
  - reference: PMID:15372378
    reference_title: "A mutation in the vesicle-trafficking protein VAPB causes late-onset spinal muscular atrophy and amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although it was not possible to link all these families, haplotype analysis suggests a founder effect."
    explanation: >
      Source for calling the VAPB allele a founder allele.
- name: ALS9
  display_name: ALS9 (ANG, loss of function)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 9
    term:
      id: MONDO:0012753
      label: amyotrophic lateral sclerosis type 9
  genes:
  - preferred_term: ANG
    term:
      id: hgnc:483
      label: ANG
  description: >
    ALS associated with heterozygous missense changes in angiogenin, an angiogenic
    ribonuclease expressed in motor neurons as well as endothelium. Functional
    assays place the mechanism in loss of ribonuclease activity, nuclear
    translocation, or both, rather than in a gain of toxic function.
  evidence:
  - reference: PMID:16501576
    reference_title: "ANG mutations segregate with familial and 'sporadic' amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We now report the finding of seven missense mutations in 15 individuals, of whom four had familial ALS and 11 apparently 'sporadic' ALS."
    explanation: >
      Establishes the ANG gene-disease relationship across familial and apparently
      sporadic cases.
  - reference: PMID:17886298
    reference_title: "Angiogenin loss-of-function mutations in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Functional assays show that these ANG mutations result in complete loss of function."
    explanation: >
      Source for describing the ANG mechanism as loss of function.
  - reference: PMID:17886298
    reference_title: "Angiogenin loss-of-function mutations in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "As a correlate, we demonstrate strong ANG expression in both endothelial cells and motor neurons of normal human spinal cords from the developing fetus and adult."
    explanation: >
      Source for the statement that angiogenin is expressed in motor neurons as
      well as endothelium.
- name: ALS10
  display_name: ALS10 (TARDBP, autosomal dominant)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 10
    term:
      id: MONDO:0012790
      label: amyotrophic lateral sclerosis type 10
  genes:
  - preferred_term: TARDBP
    term:
      id: hgnc:11571
      label: TARDBP
  description: >
    ALS from missense mutations in TARDBP, the gene encoding TDP-43. This is the
    subtype in which the genetic lesion and the defining ALS neuropathology
    coincide: TARDBP encodes the protein whose cytoplasmic accumulation the
    TDP-43 Proteinopathy node models.
  evidence:
  - reference: PMID:18372902
    reference_title: "TARDBP mutations in individuals with sporadic and familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we report eight missense mutations in nine individuals--six from individuals with sporadic ALS (SALS) and three from those with familial ALS (FALS)--and a concurring increase of a smaller TDP-43 product."
    explanation: >
      Establishes TARDBP missense mutations in both familial and sporadic ALS.
  - reference: PMID:20301761
    reference_title: "TARDBP-Related Amyotrophic Lateral Sclerosis-Frontotemporal Dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: "The phenotypic spectrum encompasses pure (i.e., without other neurologic findings) amyotrophic lateral sclerosis (ALS; most common), pure (i.e., without other neurologic findings) frontotemporal dementia (FTD; rare), a combination of ALS and FTD, and atypical neurologic phenotypes (very rare)."
    explanation: >
      The GeneReviews chapter for this subtype, establishing that TARDBP variants
      most commonly give pure ALS but span an ALS-FTD spectrum.
  - reference: PMID:20301761
    reference_title: "TARDBP-Related Amyotrophic Lateral Sclerosis-Frontotemporal Dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: "The diagnosis of TARDBP-ALS-FTD is established in a proband with suggestive findings and most commonly a heterozygous pathogenic (or likely pathogenic) variant in TARDBP identified by molecular genetic testing."
    explanation: >
      Records that the usual allelic state is heterozygous, which is the basis for
      calling this subtype autosomal dominant.
  - reference: PMID:20301761
    reference_title: "TARDBP-Related Amyotrophic Lateral Sclerosis-Frontotemporal Dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: "Rarely, homozygous pathogenic (or likely pathogenic) variants in TARDBP have been reported."
    explanation: >
      The rare homozygous exception to the dominant pattern, quoted rather than
      paraphrased into the previous item's explanation.
- name: ALS11
  display_name: ALS11 (FIG4, risk allele)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 11
    term:
      id: MONDO:0012945
      label: amyotrophic lateral sclerosis type 11
  genes:
  - preferred_term: FIG4
    term:
      id: hgnc:16873
      label: FIG4
  description: >
    ALS associated with heterozygous deleterious FIG4 alleles. FIG4 is the lipid
    phosphatase that regulates PI(3,5)P2 and whose mutations also cause the
    recessive peripheral-nerve disorder CMT4J, so the ALS association sits on a
    different part of the same gene's allelic spectrum.
  review_notes: >
    Graded deliberately as a risk relationship rather than a Mendelian one: the
    cited report frames heterozygosity for a deleterious FIG4 allele as a risk
    factor for ALS and PLS, not as a cause, and the corresponding `genetic:`
    record uses relationship_type RISK_FACTOR. MONDO nonetheless numbers the
    concept as a familial ALS type.
  evidence:
  - reference: PMID:19118816
    reference_title: "Deleterious variants of FIG4, a phosphoinositide phosphatase, in patients with ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We now describe nonsynonymous variants of FIG4 in 2% (9/473) of patients with amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS)."
    explanation: >
      Reports the frequency of FIG4 variants in an ALS and PLS series.
  - reference: PMID:19118816
    reference_title: "Deleterious variants of FIG4, a phosphoinositide phosphatase, in patients with ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Mutations of the lipid phosphatase FIG4 that regulates PI(3,5)P(2) are responsible for the recessive peripheral-nerve disorder CMT4J."
    explanation: >
      Source for FIG4's enzymatic identity and for the CMT4J relationship named in
      this subtype's description.
  - reference: PMID:19118816
    reference_title: "Deleterious variants of FIG4, a phosphoinositide phosphatase, in patients with ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Heterozygosity for a deleterious allele of FIG4 appears to be a risk factor for ALS and PLS, extending the list of known ALS genes and increasing the clinical spectrum of FIG4-related diseases."
    explanation: >
      The authors' own framing as a risk factor, which is the basis for the
      risk-rather-than-causative grading recorded above.
- name: ALS12
  display_name: ALS12 (OPTN)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 12
    term:
      id: MONDO:0013264
      label: amyotrophic lateral sclerosis type 12
  genes:
  - preferred_term: OPTN
    term:
      id: hgnc:17142
      label: OPTN
  description: >
    ALS from optineurin mutations, reported in both homozygous loss-of-function
    and heterozygous missense forms. The heterozygous E478G change falls in the
    ubiquitin-binding domain and abolishes optineurin's inhibition of NF-kappaB
    activation. OPTN is bound to this entry's Impaired Autophagy node alongside
    TBK1, VCP and SQSTM1.
  evidence:
  - reference: PMID:20428114
    reference_title: "Mutations of optineurin in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We found three types of mutation of OPTN: a homozygous deletion of exon 5, a homozygous Q398X nonsense mutation and a heterozygous E478G missense mutation within its ubiquitin-binding domain."
    explanation: >
      Establishes the OPTN gene-disease relationship and the allelic classes.
  - reference: PMID:20428114
    reference_title: "Mutations of optineurin in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Analysis of cell transfection showed that the nonsense and missense mutations of OPTN abolished the inhibition of activation of nuclear factor kappa B (NF-kappaB), and the E478G mutation revealed a cytoplasmic distribution different from that of the wild type or a POAG mutation."
    explanation: >
      Transfection data behind the NF-kappaB statement in this subtype's
      description.
- name: ALS15
  display_name: ALS15 (UBQLN2, X-linked dominant)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 15
    term:
      id: MONDO:0010459
      label: amyotrophic lateral sclerosis type 15
  genes:
  - preferred_term: UBQLN2
    term:
      id: hgnc:12509
      label: UBQLN2
  description: >
    X-linked dominant ALS and ALS with dementia from UBQLN2 mutations, spanning
    juvenile and adult onset. Ubiquilin 2 shuttles ubiquitinated substrates to the
    proteasome, and affected spinal cords carry ubiquilin 2 pathology.
  evidence:
  - reference: PMID:21857683
    reference_title: "Mutations in UBQLN2 cause dominant X-linked juvenile and adult-onset ALS and ALS/dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we show that mutations in UBQLN2, which encodes the ubiquitin-like protein ubiquilin 2, cause dominantly inherited, chromosome-X-linked ALS and ALS/dementia."
    explanation: >
      Establishes the gene, the X-linked dominant mode, and the ALS/dementia
      phenotype of this subtype.
  - reference: PMID:21857683
    reference_title: "Mutations in UBQLN2 cause dominant X-linked juvenile and adult-onset ALS and ALS/dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe novel ubiquilin 2 pathology in the spinal cords of ALS cases and in the brains of ALS/dementia"
    explanation: >
      Source for the statement that affected spinal cords carry ubiquilin 2
      pathology.
- name: ALS18
  display_name: ALS18 (PFN1, autosomal dominant)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 18
    term:
      id: MONDO:0013891
      label: amyotrophic lateral sclerosis type 18
  genes:
  - preferred_term: PFN1
    term:
      id: hgnc:8881
      label: PFN1
  description: >
    Familial ALS from mutations in profilin 1, which converts monomeric to
    filamentous actin. Mutant profilin forms ubiquitinated insoluble aggregates
    that often contain TDP-43, and motor neurons expressing it have smaller growth
    cones with a reduced F/G-actin ratio.
  evidence:
  - reference: PMID:22801503
    reference_title: "Mutations in the profilin 1 gene cause familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we show that mutations within the profilin 1 (PFN1) gene can cause FALS."
    explanation: >
      Establishes the PFN1 gene-disease relationship in familial ALS.
  - reference: PMID:22801503
    reference_title: "Mutations in the profilin 1 gene cause familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Cells expressing PFN1 mutants contain ubiquitinated, insoluble aggregates that in many cases contain the ALS-associated protein TDP-43."
    explanation: >
      Source for the aggregate and TDP-43 statements in this subtype's description.
- name: ALS19
  display_name: ALS19 (ERBB4, autosomal dominant)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 19
    term:
      id: MONDO:0014223
      label: amyotrophic lateral sclerosis type 19
  genes:
  - preferred_term: ERBB4
    term:
      id: hgnc:3432
      label: ERBB4
  description: >
    Late-onset autosomal dominant ALS with incomplete penetrance from ERBB4
    mutations that reduce ErbB4 autophosphorylation in response to neuregulin-1.
    The reported clinical picture is combined upper and lower motor neuron
    involvement without obvious cognitive dysfunction and relatively slow
    progression.
  evidence:
  - reference: PMID:24119685
    reference_title: "ERBB4 mutations that disrupt the neuregulin-ErbB4 pathway cause amyotrophic lateral sclerosis type 19."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Functional analysis revealed that these mutations led to a reduced autophosphorylation of ErbB4 upon neuregulin-1 (NRG-1) stimulation."
    explanation: >
      Establishes the signalling lesion this subtype describes.
  - reference: PMID:24119685
    reference_title: "ERBB4 mutations that disrupt the neuregulin-ErbB4 pathway cause amyotrophic lateral sclerosis type 19."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical presentations of the individuals with mutations were characterized by the involvement of both upper and lower motor neurons, a lack of obvious cognitive dysfunction, and relatively slow progression."
    explanation: >
      Source for the clinical description of this subtype.
- name: ALS20
  display_name: ALS20 (HNRNPA1)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 20
    term:
      id: MONDO:0014181
      label: amyotrophic lateral sclerosis type 20
  genes:
  - preferred_term: HNRNPA1
    term:
      id: hgnc:5031
      label: HNRNPA1
  description: >
    ALS from mutations in the prion-like domain of hnRNPA1. The same class of
    lesion in hnRNPA1 and its paralogue hnRNPA2B1 produces multisystem
    proteinopathy affecting muscle, brain, motor neuron and bone, of which
    familial ALS is one presentation.
  evidence:
  - reference: PMID:23455423
    reference_title: "Mutations in prion-like domains in hnRNPA2B1 and hnRNPA1 cause multisystem proteinopathy and ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we define pathogenic mutations in PrLDs of heterogeneous nuclear ribonucleoproteins (hnRNPs) A2B1 and A1 in families with inherited degeneration affecting muscle, brain, motor neuron and bone, and in one case of familial amyotrophic lateral sclerosis."
    explanation: >
      Establishes the prion-like-domain lesion and records that the familial ALS
      presentation rested on a single case in this report.
- name: ALS21
  display_name: ALS21 (MATR3)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 21
    term:
      id: MONDO:0011632
      label: amyotrophic lateral sclerosis type 21
  genes:
  - preferred_term: MATR3
    term:
      id: hgnc:6912
      label: MATR3
  description: >
    Familial ALS from MATR3 mutations. Matrin 3 is an RNA- and DNA-binding protein
    that interacts with TDP-43, and MATR3 pathology is seen in ALS spinal cords
    with and without MATR3 mutations, which places this subtype inside the RNA
    processing axis rather than beside it.
  evidence:
  - reference: PMID:24686783
    reference_title: "Mutations in the Matrin 3 gene cause familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Using exome sequencing, we identified mutations in MATR3 in ALS kindreds."
    explanation: >
      Establishes the MATR3 gene-disease relationship.
  - reference: PMID:24686783
    reference_title: "Mutations in the Matrin 3 gene cause familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We also observed MATR3 pathology in ALS-affected spinal cords with and without MATR3 mutations."
    explanation: >
      Source for the statement that MATR3 pathology is not confined to MATR3
      mutation carriers.
- name: ALS23
  display_name: ALS23 (ANXA11)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis type 23
    term:
      id: MONDO:0027694
      label: amyotrophic lateral sclerosis type 23
  genes:
  - preferred_term: ANXA11
    term:
      id: hgnc:535
      label: ANXA11
  description: >
    ALS from mutations in annexin A11, a vesicular trafficking protein. The
    recurrent p.D40G allele was absent from 70,000 control exomes, segregated in
    two kindreds, and carriers shared a founder haplotype; annexin A11-positive
    aggregates are present in spinal cord motor neurons of a carrier.
  evidence:
  - reference: PMID:28469040
    reference_title: "Mutations in the vesicular trafficking protein annexin A11 are associated with amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We screened 751 familial ALS patient whole-exome sequences and identified six mutations including p.D40G in the ANXA11 gene in 13 individuals."
    explanation: >
      Establishes the ANXA11 gene-disease relationship and the cohort it was found in.
  - reference: PMID:28469040
    reference_title: "Mutations in the vesicular trafficking protein annexin A11 are associated with amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The p.D40G mutation was absent from 70,000 control whole-exome sequences."
    explanation: >
      Source for the control-absence figure quoted in this subtype's description.
  - reference: PMID:28469040
    reference_title: "Mutations in the vesicular trafficking protein annexin A11 are associated with amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This mutation segregated with disease in two kindreds and was present in another two unrelated cases (P = 0.0102), and all mutation carriers shared a common founder haplotype."
    explanation: >
      Source for the segregation and founder-haplotype statements above.
  - reference: PMID:28469040
    reference_title: "Mutations in the vesicular trafficking protein annexin A11 are associated with amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Annexin A11-positive protein aggregates were abundant in spinal cord motor neurons and hippocampal neuronal axons in an ALS patient carrying the p.D40G mutation."
    explanation: >
      Source for the spinal cord motor neuron aggregate finding.
- name: ALS26
  display_name: ALS26 (TIA1, with or without frontotemporal dementia; contested)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis 26 with or without frontotemporal dementia
    term:
      id: MONDO:0030885
      label: amyotrophic lateral sclerosis 26 with or without frontotemporal dementia
  genes:
  - preferred_term: TIA1
    term:
      id: hgnc:11802
      label: TIA1
  description: >
    ALS with or without frontotemporal dementia attributed to mutations in the
    low-complexity domain of TIA1, which increase the protein's propensity to
    phase-separate and leave non-dynamic stress granules containing TDP-43. The
    gene-disease relationship is contested: the Project MinE consortium holds that
    the published pedigree and burden analysis do not establish causality without
    replication.
  review_notes: >
    Retained as a subtype row because MONDO and OMIM define the concept
    (MONDO:0030885, OMIM:619133) and the KB records what is claimed as well as
    what is settled, but the contrary position is carried as a REFUTE evidence
    item rather than left out, and the corresponding `genetic:` record is graded
    DISPUTED. No ClinGen gene-disease validity classification for TIA1 and ALS is
    cited here; the grade rests on the two primary reports below.
  evidence:
  - reference: PMID:28817800
    reference_title: "TIA1 Mutations in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Promote Phase Separation and Alter Stress Granule Dynamics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we studied a novel ALS/FTD family and identified the P362L mutation in the low-complexity domain (LCD) of T cell-restricted intracellular antigen-1 (TIA1)."
    explanation: >
      The original report proposing TIA1 as an ALS/FTD gene.
  - reference: PMID:28817800
    reference_title: "TIA1 Mutations in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Promote Phase Separation and Alter Stress Granule Dynamics."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In live cells, TIA1 mutations delayed stress granule (SG) disassembly and promoted the accumulation of non-dynamic SGs that harbored TDP-43."
    explanation: >
      Source for the stress granule mechanism described for this subtype.
  - reference: PMID:29235362
    reference_title: "Reconsidering the causality of TIA1 mutations in ALS."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Because of this, without a replication effort, we hold that rare TIA1 mutations cannot be regarded as causal in ALS, and that it is premature to include this gene in diagnostic panels for ALS and FTD."
    explanation: >
      The Project MinE consortium's published challenge to TIA1 causality, which
      is why this subtype is recorded as contested rather than established.
- name: ALS28
  display_name: ALS28 (LRP12 CGG repeat expansion; not replicated outside Asian ancestry)
  subtype_term:
    preferred_term: amyotrophic lateral sclerosis 28
    term:
      id: MONDO:0957538
      label: amyotrophic lateral sclerosis 28
  genes:
  - preferred_term: LRP12
    term:
      id: hgnc:31708
      label: LRP12
  description: >
    ALS attributed to CGG repeat expansions of 61-100 units in LRP12, reported in
    five families and two simplex individuals. Longer expansions of 100-200 units in the
    same repeat cause oculopharyngodistal myopathy type 1, so the claim is that
    repeat length switches the phenotype. A whole-genome screen of European ALS
    patients and controls found no expanded alleles at all.
  review_notes: >
    Deliberately not wired to a pathophysiology node. The repeat-expansion
    mechanism reported for LRP12-ALS (RNA foci, cytoplasmic phospho-TDP-43 in
    iPSC-derived motor neurons) resembles the C9orf72 node in this entry, but
    that node is scoped to the C9orf72 GGGGCC expansion specifically, and the
    LRP12 gene-disease relationship itself has not replicated outside patients of
    Asian ancestry. Recorded rather than asserted.
  evidence:
  - reference: PMID:37339631
    reference_title: "CGG repeat expansion in LRP12 in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identify CGG repeat expansion in LRP12 in five families and two simplex individuals."
    explanation: >
      The primary report of LRP12 repeat expansions in ALS.
  - reference: PMID:37339631
    reference_title: "CGG repeat expansion in LRP12 in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These ALS individuals (LRP12-ALS) have 61-100 repeats, which contrasts with most OPDM individuals with repeat expansion in LRP12 (LRP12-OPDM), who have 100-200 repeats."
    explanation: >
      Source for the repeat-length ranges given in this subtype's description.
  - reference: PMID:38726482
    reference_title: "Short tandem repeat expansions in LRP12 are absent in cohorts of familial and sporadic amyotrophic lateral sclerosis patients of European ancestry."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "All individuals had LRP12 CGG repeat lengths within the normal range of 3-25 units."
    explanation: >
      Screening 608 sporadic ALS patients, 35 familial probands and 4,703 controls
      of European ancestry found no expansion, which is the non-replication this
      subtype records.
- name: FTDALS1
  display_name: FTDALS1 (C9orf72 GGGGCC repeat expansion)
  subtype_term:
    preferred_term: frontotemporal dementia and/or amyotrophic lateral sclerosis 1
    term:
      id: MONDO:0007105
      label: frontotemporal dementia and/or amyotrophic lateral sclerosis 1
  genes:
  - preferred_term: C9orf72
    term:
      id: hgnc:28337
      label: C9orf72
  description: >
    The chromosome 9p-linked FTD/ALS locus, caused by a noncoding GGGGCC
    hexanucleotide repeat expansion in C9orf72 rather than by a coding lesion.
    In European populations it is the commonest genetic cause of both familial ALS
    and familial FTD. It is the largest of several shared causes, not the only
    one: TBK1, CCNF and VCP are likewise numbered as FTD and/or ALS loci in the
    rows below, and TARDBP and UBQLN2 also span ALS and dementia. The ranking does
    not hold everywhere either: in Asian populations SOD1 is the commonest ALS
    gene and C9orf72 expansions are comparatively rare.
  evidence:
  - reference: PMID:21944778
    reference_title: "Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report an expansion of a noncoding GGGGCC hexanucleotide repeat in the gene C9ORF72 that is strongly associated with disease in a large FTD/ALS kindred, previously reported to be conclusively linked to chromosome 9p."
    explanation: >
      Identifies the noncoding repeat expansion at the chromosome 9p FTD/ALS locus
      that MONDO:0007105 denotes.
  - reference: PMID:28057713
    reference_title: "Genetic epidemiology of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In European populations, the most common mutations were the C9orf72 repeat expansions (FALS 33.7%, SALS 5.1%), followed by SOD1 (FALS 14.8%, SALS 1.2%), TARDBP (FALS 4.2%, SALS 0.8%) and FUS mutations (FALS 2.8%, SALS 0.3%), while in Asian populations the most common mutations were SOD1 mutations (FALS 30.0%, SALS 1.5%), followed by FUS (FALS 6.4%, SALS 0.9%), C9orf72 (FALS 2.3%, SALS 0.3%) and TARDBP (FALS 1.5%, SALS 0.2%) mutations."
    explanation: >
      Source for both halves of the ranking claim above: C9orf72 leads in European
      familial ALS, and does not in Asian populations.
  - reference: PMID:25577942
    reference_title: "C9orf72 Frontotemporal Dementia and/or Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: "The diagnosis of C9orf72-FTD/ALS is established in a proband with suggestive findings and a heterozygous abnormal G4C2 (GGGGCC) hexanucleotide repeat expansion in C9orf72 identified by molecular genetic testing."
    explanation: >
      The GeneReviews chapter for this subtype, stating the diagnostic lesion.
  - reference: PMID:25577942
    reference_title: "C9orf72 Frontotemporal Dementia and/or Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: "The clinical presentation is highly heterogeneous and may differ between and within families, causing an unpredictable pattern and age of onset of clinical manifestations."
    explanation: >
      Source for treating this subtype as an FTD/ALS spectrum rather than as a
      single phenotype.
- name: FTDALS4
  display_name: FTDALS4 (TBK1 haploinsufficiency)
  subtype_term:
    preferred_term: frontotemporal dementia and/or amyotrophic lateral sclerosis 4
    term:
      id: MONDO:0014641
      label: frontotemporal dementia and/or amyotrophic lateral sclerosis 4
  genes:
  - preferred_term: TBK1
    term:
      id: hgnc:11584
      label: TBK1
  description: >
    ALS and frontotemporal dementia from loss-of-function TBK1 alleles acting by
    haploinsufficiency. Some coiled-coil-domain mutants instead lose the
    interaction with optineurin, tying this subtype to ALS12 at the protein level.
    The enrichment was specific to familial cases and was not seen in a sporadic
    screen.
  evidence:
  - reference: PMID:25803835
    reference_title: "Haploinsufficiency of TBK1 causes familial ALS and fronto-temporal dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Gene-based rare variant analysis identified an exome-wide significant enrichment of eight loss-of-function (LoF) mutations in TBK1 (encoding TANK-binding kinase 1) in 13 fALS pedigrees."
    explanation: >
      Establishes the TBK1 loss-of-function enrichment in familial ALS pedigrees.
  - reference: PMID:25803835
    reference_title: "Haploinsufficiency of TBK1 causes familial ALS and fronto-temporal dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "No enrichment of LoF mutations was observed in a targeted mutation screen of 1,010 sporadic ALS and 650 additional control individuals."
    explanation: >
      Source for restricting the TBK1 enrichment claim to familial ALS.
  - reference: PMID:25803835
    reference_title: "Haploinsufficiency of TBK1 causes familial ALS and fronto-temporal dementia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In vitro experiments confirmed the loss of expression of TBK1 LoF mutant alleles, or loss of interaction of the C-terminal TBK1 coiled-coil domain (CCD2) mutants with the TBK1 adaptor protein optineurin, which has been shown to be involved in ALS pathogenesis."
    explanation: >
      Source for the two mutant classes described above, including the
      coiled-coil-domain mutants that lose the optineurin interaction.
- name: FTDALS5
  display_name: FTDALS5 (CCNF / cyclin F)
  subtype_term:
    preferred_term: frontotemporal dementia and/or amyotrophic lateral sclerosis 5
    term:
      id: MONDO:0030875
      label: frontotemporal dementia and/or amyotrophic lateral sclerosis 5
  genes:
  - preferred_term: CCNF
    term:
      id: hgnc:1591
      label: CCNF
  description: >
    ALS and frontotemporal dementia from mutations in CCNF, which encodes cyclin F,
    the substrate-recognition component of an SCF E3 ubiquitin-ligase complex.
    Mutant cyclin F causes abnormal ubiquitination and accumulation of
    ubiquitinated proteins including TDP-43.
  evidence:
  - reference: PMID:27080313
    reference_title: "CCNF mutations in amyotrophic lateral sclerosis and frontotemporal dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we use genome-wide linkage analysis in a large ALS/FTD kindred to identify a novel disease locus on chromosome 16p13.3. Whole-exome sequencing identified a CCNF missense mutation at this locus."
    explanation: >
      Establishes the CCNF gene-disease relationship by linkage plus exome
      sequencing in an ALS/FTD kindred.
  - reference: PMID:27080313
    reference_title: "CCNF mutations in amyotrophic lateral sclerosis and frontotemporal dementia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Expression of mutant CCNF in neuronal cells caused abnormal ubiquitination and accumulation of ubiquitinated proteins, including TDP-43 and a SCF(Cyclin F) substrate."
    explanation: >
      Source for the ubiquitination mechanism described for this subtype.
- name: FTDALS6
  display_name: FTDALS6 (VCP, autosomal dominant)
  subtype_term:
    preferred_term: frontotemporal dementia and/or amyotrophic lateral sclerosis 6
    term:
      id: MONDO:0013501
      label: frontotemporal dementia and/or amyotrophic lateral sclerosis 6
  genes:
  - preferred_term: VCP
    term:
      id: hgnc:12666
      label: VCP
  description: >
    Autosomal dominant ALS from VCP mutations. The same gene causes inclusion body
    myopathy with Paget disease of bone and frontotemporal dementia, and the ALS
    presentation was recognized as an extension of that phenotype rather than as a
    separate genetic entity.
  review_notes: >
    Distinct from kb/disorders/Inclusion_Body_Myopathy_with_Paget_Disease_of_Bone_and_Frontotemporal_Dementia.yaml,
    which is bound to MONDO:0000507. That entry models the multisystem
    proteinopathy; this row is the ALS presentation of the same gene, which MONDO
    numbers separately as FTDALS6.
  evidence:
  - reference: PMID:21145000
    reference_title: "Exome sequencing reveals VCP mutations as a cause of familial ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Using exome sequencing, we identified a p.R191Q amino acid change in the valosin-containing protein (VCP) gene in an Italian family with autosomal dominantly inherited amyotrophic lateral sclerosis (ALS)."
    explanation: >
      Establishes the VCP gene-disease relationship in autosomal dominant familial ALS.
  - reference: PMID:21145000
    reference_title: "Exome sequencing reveals VCP mutations as a cause of familial ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Screening of VCP in a cohort of 210 familial ALS cases and 78 autopsy-proven ALS cases identified four additional mutations including a p.R155H mutation in a pathologically proven case of ALS."
    explanation: >
      Replication of VCP mutations in a larger familial ALS cohort.
  - reference: PMID:21145000
    reference_title: "Exome sequencing reveals VCP mutations as a cause of familial ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Mutations in VCP have previously been identified in families with Inclusion Body Myopathy, Paget disease, and Frontotemporal Dementia (IBMPFD)."
    explanation: >
      Source for the statement that the same gene causes IBMPFD, curated as a
      separate entry.
mechanistic_hypotheses:
- hypothesis_group_id: canonical_motor_neuron_proteostatic_failure_model
  hypothesis_label: Canonical Motor Neuron Proteostatic Failure Model
  status: CANONICAL
  description: >-
    Progressive upper and lower motor neuron degeneration in ALS is the convergent endpoint of multiple genetic and sporadic insults that ultimately cause proteostatic failure. Key drivers include cytoplasmic mislocalization and aggregation of TDP-43 (in >97% of cases), C9orf72 hexanucleotide repeat expansion–derived dipeptide repeats and RNA foci, SOD1 misfolding, FUS/EWSR1 phase-separation defects, impaired autophagy, mitochondrial dysfunction, axonal transport failure, and neuroinflammation. Selective vulnerability of cortical layer-5 Betz cells and spinal alpha motor neurons leads to progressive muscle denervation, weakness, atrophy, and ultimately respiratory failure. Antisense-oligonucleotide therapy targeting SOD1 (tofersen) provides the strongest interventional validation of the SOD1 genetic-pathogenetic axis of this canonical multi-hit model, although that validation rests on target engagement and biomarker lowering rather than on a positive randomized clinical endpoint. The C9orf72 ASO program (BIIB078) was discontinued after a Phase 1 study that showed neither neurofilament reduction nor clinical benefit, indicating that lowering sense-strand repeat RNA alone is insufficient; that single negative program does not by itself establish which of the competing C9orf72 mechanisms — antisense-strand RNA toxicity, dipeptide-repeat proteins, or haploinsufficiency — dominates.
  notes: >-
    Retained as CANONICAL. The 2026 openscientist
    hypothesis-search report
    (kb/hypotheses/Amyotrophic_Lateral_Sclerosis/canonical_motor_neuron_proteostatic_failure_model)
    confirms convergent proteostatic failure as the unifying ALS
    mechanism: TDP-43 proteinopathy in ~97% of cases, SOD1 misfolding,
    C9orf72 RNA foci and DPRs, FUS phase-separation defects, impaired
    autophagy, mitochondrial dysfunction, axonal transport failure, and
    neuroinflammation all converge on motor-neuron degeneration. Tofersen
    (SOD1 ASO) approval provides the strongest causal validation of the
    genetic-pathogenetic axes. Four qualifications: (1) the C9orf72-ASO
    program (BIIB078; Phase 1 discontinued) showed insufficient clinical efficacy — lowering
    sense-strand repeat RNA does not consistently translate to motor
    preservation. The 2026 openscientist report reads that failure as
    evidence that DPR-mediated toxicity dominates; the assessment
    (assessments/openscientist-assessment-by-codex.yaml, claim
    c9orf72-failure-mechanism) rejects that inference, since one ASO at one
    dose range and exposure period cannot separate incomplete target
    engagement, treatment timing, antisense-strand transcripts, DPR toxicity,
    haploinsufficiency, or persistent TDP-43 pathology. (2) The
    "proteostatic failure" framing remains a descriptive convergence
    rather than a single mechanistic primer — different genetic ALS
    subtypes follow different upstream paths. (3) Sporadic ALS (~90%)
    requires environmental/epigenetic modifiers (BMAA, head trauma,
    aging) that the canonical model does not specify. (4) The tofersen
    evidence is target-engagement- and biomarker-led: VALOR's prespecified
    28-week ALSFRS-R primary endpoint and its clinical secondary endpoints
    did not separate from placebo, and the longer-term early-start versus
    delayed-start advantage comes from an open-label extension with
    substantial attrition, so it is not a blinded randomized efficacy
    comparison.
  evidence:
  - reference: PMID:38891021
    reference_title: "Updates on Disease Mechanisms and Therapeutics for Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "upper and lower motor neurons in the brain and spinal cord progressively degenerate"
    explanation: >
      Canonical mechanism review used as the seed reference for the
      hypothesis-search deep-research run.
  - reference: PMID:34873335
    reference_title: Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The combination of all ALS-associated signals reveals a role for perturbations in vesicle-mediated transport and autophagy and provides evidence for cell-autonomous disease initiation in glutamatergic neurons."
    explanation: >-
      Cross-ancestry GWAS of 29,612 patients supplying the human-genetic basis
      for the convergence framing in this hypothesis: locus-specific genetic
      architectures nonetheless aggregate onto vesicle-mediated transport and
      autophagy in a defined neuronal population. Note what it does and does not
      say — it identifies converging pathways and a cell-autonomous initiation
      site, not a single ordered proteostatic chain shared by all ALS, which is
      why qualification (2) in this hypothesis's notes stands.
  - reference: PMID:39986312
    reference_title: "Amyotrophic lateral sclerosis caused by hexanucleotide repeat expansions in C9orf72: from genetics to therapeutics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical trials using antisense oligonucleotides to target the GGGGCC repeat RNA have not been successful, potentially because they only target a single gain-of-function mechanism."
    explanation: >
      Lancet Neurology 2025 review confirms that C9orf72 ASO trials did not
      achieve clinical benefit, directly qualifying the canonical model's
      genetic-pathogenetic-axis interventional validation. The hexanucleotide
      repeat expansion drives a complex interplay of loss-of-function and
      gain-of-function pathology that single-target therapies do not address.
  - reference: PMID:39059407
    reference_title: "Safety, tolerability, and pharmacokinetics of antisense oligonucleotide BIIB078 in adults with C9orf72-associated amyotrophic lateral sclerosis: a phase 1, randomised, double blinded, placebo-controlled, multiple ascending dose study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "On the basis of these phase 1 study results, including secondary and exploratory findings showing no reduction in neurofilament levels and no benefit on clinical outcomes relative to the placebo cohort, BIIB078 clinical development has been discontinued."
    explanation: >-
      Primary publication of the randomized, placebo-controlled BIIB078 phase 1
      study, cited here in place of relying on a review for the C9orf72 arm of
      this hypothesis. It supports the entry's claim that sense-strand repeat-RNA
      lowering alone produced neither biomarker nor clinical benefit. It does
      not identify which C9orf72 mechanism dominates, so the mechanistic
      inference in this hypothesis's notes is kept qualified.
- hypothesis_group_id: tdp43_rna_dysregulation_selective_vulnerability_model
  hypothesis_label: TDP-43 RNA Dysregulation and Motor-Neuron Selective Vulnerability Model
  status: EMERGING
  description: >-
    This focused model treats ALS-associated TDP-43 pathology as a coupled
    nuclear loss-of-function and cytoplasmic gain-of-function process. Nuclear
    depletion of TDP-43 removes cryptic-exon repression and other RNA-processing
    controls in vulnerable motor neurons, producing mis-spliced or unstable
    transcripts such as STMN2 and UNC13A that impair axonal repair, synaptic
    function, and proteostasis. Cytoplasmic TDP-43 aggregation may amplify injury
    through stress-granule and proteostatic dysfunction and may contribute to
    propagation, but the unresolved causal step is which RNA target, aggregate
    species, or non-cell-autonomous signal converts TDP-43 dysfunction into
    selective motor-neuron death.
  evidence:
  - reference: PMID:32799899
    reference_title: "The role of TDP-43 mislocalization in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Research has focused on the formation and consequences of cytosolic protein aggregates as drivers of ALS pathology through both gain- and loss-of-function mechanisms."
    explanation: >
      Review-level synthesis supports modeling TDP-43 pathology as both nuclear
      loss-of-function and cytoplasmic gain-of-function rather than as aggregation
      alone.
  - reference: PMID:26250685
    reference_title: "TDP-43 repression of nonconserved cryptic exons is compromised in ALS-FTD."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "repression of cryptic exons was impaired in ALS-FTD cases, suggesting that this splicing defect could potentially underlie TDP-43 proteinopathy."
    explanation: >
      Human ALS-FTD tissue evidence links loss of TDP-43 cryptic-exon repression
      to TDP-43 proteinopathy.
  - reference: PMID:30643292
    reference_title: "ALS-implicated protein TDP-43 sustains levels of STMN2, a mediator of motor neuron growth and repair."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "STMN2 loss upon reduced TDP-43 function was due to altered splicing, which is functionally important, as we show STMN2 is necessary for normal axonal outgrowth and regeneration."
    explanation: >
      Human motor-neuron experiments identify STMN2 mis-splicing and loss as a
      functional downstream RNA target that impairs axonal growth and repair.
  - reference: PMID:35197628
    reference_title: "TDP-43 loss and ALS-risk SNPs drive mis-splicing and depletion of UNC13A."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our findings, which demonstrate a genetic link between loss of nuclear TDP-43 function and disease, reveal the mechanism by which UNC13A variants exacerbate the effects of decreased TDP-43 function."
    explanation: >
      UNC13A cryptic splicing links a human ALS/FTD risk locus to loss of nuclear
      TDP-43 function, supporting a target-specific RNA-dysregulation arm of the
      focused hypothesis.
  notes: >-
    The 2026 OpenScientist hypothesis report
    (kb/hypotheses/Amyotrophic_Lateral_Sclerosis/tdp43_rna_dysregulation_selective_vulnerability_model)
    judged the TDP-43 loss-of-function/cryptic-exon arm to be the strongest,
    best-supported part of this hypothesis, while keeping the integrated model
    of RNA loss, cytoplasmic gain-of-function, selective vulnerability, and
    propagation as emerging because the rate-limiting RNA target, aggregate
    species, upstream trigger hierarchy, and spread mechanism remain unresolved.
    Additional report-suggested PMIDs were retained as curation leads and not
    added here without independent PubMed/cache verification.
pathophysiology:
- name: Motor Neuron Degeneration
  description: >
    Progressive death of upper motor neurons in the motor cortex and lower motor neurons
    in the brainstem and spinal cord leads to denervation of skeletal muscles. The loss of
    upper motor neurons causes spasticity and hyperreflexia, while lower motor neuron loss
    results in muscle weakness, atrophy, and fasciculations.
  cell_types:
  - preferred_term: motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  locations:
  - preferred_term: primary motor cortex
    term:
      id: UBERON:0001384
      label: primary motor cortex
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "A neurodegenerative disease characterized by progressive muscular paralysis reflecting degeneration of motor neurons in the primary motor cortex, corticospinal tracts, brainstem and spinal cord."
    explanation: Orphanet definition confirms progressive motor neuron degeneration across cortex, brainstem, and spinal cord.
  - reference: PMID:38521060
    reference_title: "Single-cell dissection of the human motor and prefrontal cortices in ALS and FTLD."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identify known and previously unidentified vulnerable populations in cortical layer 5 and show that ALS- and FTLD-implicated motor and spindle neurons possess a virtually indistinguishable molecular identity."
    explanation: Single-cell atlas of human ALS motor cortex identifies vulnerable neuronal populations in cortical layer 5 (including ALS-implicated motor/spindle neurons), supporting selective cortical motor-neuron vulnerability.
  - reference: PMID:38891021
    reference_title: "Updates on Disease Mechanisms and Therapeutics for Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    snippet: "upper and lower motor neurons in the brain and spinal cord progressively degenerate during the course of the disease, leading to the loss of the voluntary movement of the arms and legs."
    explanation: Review summarizes canonical ALS pathology of progressive upper and lower motor neuron degeneration causing loss of voluntary movement.
  - reference: PMID:36116464
    reference_title: "Amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Amyotrophic lateral sclerosis is a fatal CNS neurodegenerative disease."
    explanation: Lancet Seminar underscores ALS as a fatal neurodegenerative disorder affecting central nervous system motor pathways.
- name: Nuclear Pore Complex Dysfunction
  description: >
    Selective loss of nuclear pore complex (NPC) components, particularly the scaffold
    proteins NUP107 and NUP93 and FG-repeat-containing components, is a consistent feature
    across ALS postmortem spinal cord, SOD1^G93A and TDP-43 mutant mouse models, and human
    cell systems. CRISPR-mediated NUP107 depletion is sufficient to trigger cytoplasmic
    TDP-43 mislocalization, increased TDP-43 phosphorylation, and autophagy dysfunction,
    placing NPC dysfunction upstream of TDP-43 proteinopathy in the canonical proteostatic
    failure cascade. Oxidative stress exacerbates NPC subunit mislocalization, creating a
    redox-sensitive vulnerability that amplifies the downstream TDP-43 aggregation phenotype.
  cell_types:
  - preferred_term: motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  genes:
  - preferred_term: NUP50
    term:
      id: hgnc:8065
      label: NUP50
  - preferred_term: GLE1
    term:
      id: hgnc:4315
      label: GLE1
  biological_processes:
  - preferred_term: nucleocytoplasmic transport
    term:
      id: GO:0006913
      label: nucleocytoplasmic transport
    modifier: DECREASED
  downstream:
  - target: TDP-43 Proteinopathy
    description: NPC scaffold loss permits cytoplasmic TDP-43 mislocalization, hyperphosphorylation, and autophagy dysfunction.
    evidence:
    - reference: PMID:40819564
      reference_title: "Nuclear pore complex dysfunction drives TDP-43 pathology in ALS."
      supports: SUPPORT
      snippet: "CRISPR-mediated depletion of NUP107 in human cells triggers hallmark features of ALS pathology, including cytoplasmic TDP-43 mislocalization, increased phosphorylation, and autophagy dysfunction."
      explanation: Direct CRISPR perturbation places NPC dysfunction upstream of TDP-43 proteinopathy.
  evidence:
  - reference: PMID:40819564
    reference_title: "Nuclear pore complex dysfunction drives TDP-43 pathology in ALS."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "CRISPR-mediated depletion of NUP107 in human cells triggers hallmark features of ALS pathology, including cytoplasmic TDP-43 mislocalization, increased phosphorylation, and autophagy dysfunction."
    explanation: >
      Direct CRISPR perturbation demonstrating that NPC dysfunction is sufficient to
      reproduce hallmark ALS molecular pathology, including TDP-43 cytoplasmic mislocalization,
      phosphorylation, and autophagy disruption. Establishes NPC dysfunction as an upstream
      driver of the canonical TDP-43 proteinopathy axis.
  - reference: PMID:40819564
    reference_title: "Nuclear pore complex dysfunction drives TDP-43 pathology in ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "selective loss of NPC components, particularly the scaffold proteins NUP107 and NUP93, and FG-repeat-containing components-is a consistent finding across ALS postmortem spinal cord"
    explanation: >
      Postmortem human ALS spinal cord shows selective NPC scaffold loss,
      confirming NPC dysfunction in human disease.
  - reference: PMID:40819564
    reference_title: "Nuclear pore complex dysfunction drives TDP-43 pathology in ALS."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "selective loss of NPC components, particularly the scaffold proteins NUP107 and NUP93, and FG-repeat-containing components-is a consistent finding across ALS postmortem spinal cord, SOD1^G93A and TDP-43 mutant mouse models, and human cell systems"
    explanation: >
      Convergent NPC dysfunction in SOD1^G93A and TDP-43 mutant mouse models
      confirms this finding is not a model-system artifact and supports
      cross-species generalizability of the mechanism.
- name: TDP-43 Proteinopathy
  conforms_to: "tdp43_proteinopathy#Cytoplasmic TDP-43 Aggregation"
  description: >
    Cytoplasmic aggregation of TDP-43 (TAR DNA-binding protein 43) is found in approximately
    97% of ALS cases, with notable exceptions such as SOD1- and FUS-associated ALS. TDP-43
    normally functions as a predominantly nuclear RNA-binding protein. In ALS it becomes
    depleted from the nucleus and accumulates in cytoplasmic phosphorylated, ubiquitinated
    inclusions, creating a coupled loss-of-nuclear-function and cytoplasmic gain-of-function
    state. The nuclear loss arm impairs RNA processing and cryptic-exon repression, while
    cytoplasmic aggregation may block normal cellular processes, disturb proteostasis, and
    participate in spread-like propagation.
  notes: >
    The 97% figure used in this node, in the entry description, and in the
    canonical mechanistic hypothesis is sourced by PMID:42541567 in the evidence
    below. PMID:19251628, also cited in this entry, gives ~90% for ubiquitinated
    TDP-43 inclusions in motor neuron perikarya; that is a different measurement
    from a different source and the two should not be merged.
  genes:
  - preferred_term: TARDBP
    term:
      id: hgnc:11571
      label: TARDBP
  biological_processes:
  - preferred_term: RNA processing
    term:
      id: GO:0006396
      label: RNA processing
    modifier: ABNORMAL
  - preferred_term: RNA splicing
    term:
      id: GO:0000375
      label: RNA splicing, via transesterification reactions
    modifier: ABNORMAL
  downstream:
  - target: TDP-43-Dependent Cryptic Exon Misprocessing
    description: >-
      Nuclear depletion of TDP-43 removes repression of cryptic exons and
      cryptic splice-polyadenylation events in disease-relevant transcripts.
    causal_link_type: DIRECT
    hypothesis_groups:
    - tdp43_rna_dysregulation_selective_vulnerability_model
    evidence:
    - reference: PMID:26250685
      reference_title: "TDP-43 repression of nonconserved cryptic exons is compromised in ALS-FTD."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "repression of cryptic exons was impaired in ALS-FTD cases, suggesting that this splicing defect could potentially underlie TDP-43 proteinopathy."
      explanation: >
        Human ALS-FTD tissue data place impaired cryptic-exon repression
        downstream of TDP-43 nuclear loss.
  - target: TDP-43-Driven Glycolytic Failure
    description: >-
      Cytoplasmic TDP-43 sequesters hexokinase 1, coupling the proteinopathy to a
      glycolytic-metabolic lesion in motor neurons.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:41838122
      reference_title: "TDP-43 impairs glycolysis by sequestering hexokinase 1 in amyotrophic lateral sclerosis."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "cytoplasmic TDP-43 directly binds to HK1, disassociating it from mitochondria and promoting its sequestration"
      explanation: >-
        Cytoplasmic TDP-43 directly sequesters HK1 — the edge linking TDP-43
        proteinopathy to glycolytic failure.
  evidence:
  - reference: PMID:42541567
    reference_title: "Targeting TDP-43 in sporadic amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: "The identification of the accumulation of TAR DNA-binding protein 43 (TDP-43) in 97% of total ALS cases represents a critical pathogenic hallmark."
    explanation: >
      Source for the 97% figure this node, the entry description, and the
      canonical mechanistic hypothesis all use.
  - reference: PMID:32799899
    reference_title: "The role of TDP-43 mislocalization in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "TDP-43 bridges the divide between sporadic and familial ALS and remains a dominant protein of interest to understand disease pathogenesis."
    explanation: >
      Review summarizes TDP-43 as the common pathological bridge between sporadic
      and familial ALS mechanisms.
  - reference: PMID:32799899
    reference_title: "The role of TDP-43 mislocalization in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "TDP-43 was identified as a primary component of ubiquitinated and hyper-phosphorylated cytosolic aggregates observed from post-mortem tissue of patients with ALS"
    explanation: >
      Postmortem ALS evidence identifies TDP-43 as a primary component of
      ubiquitinated, hyperphosphorylated cytosolic aggregates.
  - reference: PMID:32799899
    reference_title: "The role of TDP-43 mislocalization in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Together, these data suggest that both loss- and gain-of-TDP-43 function mediated by nuclear-to-cytoplasmic mislocalization cause systemic cellular dysfunction in ALS."
    explanation: >
      Synthesis supports the coupled loss-of-function and gain-of-function
      framing of TDP-43 mislocalization.
- name: TDP-43-Dependent Cryptic Exon Misprocessing
  conforms_to: "tdp43_proteinopathy#Nuclear Loss of TDP-43 RNA-Processing Function"
  description: >
    Loss of nuclear TDP-43 derepresses cryptic exons and cryptic
    splice-polyadenylation events in RNA targets relevant to ALS. STMN2
    misprocessing lowers stathmin-2, compromising axonal outgrowth, axon
    regeneration, and lysosome trafficking in TDP-43-deficient human motor
    neurons. UNC13A cryptic exon inclusion links common ALS/FTD risk variants to
    loss of nuclear TDP-43 function and can deplete a synaptic protein. This
    node represents the most concrete RNA-processing defect currently modeled as
    a candidate causal bridge from TDP-43 dysfunction toward motor-neuron death,
    while acknowledging that target priority and cell-type selectivity remain
    unresolved.
  cell_types:
  - preferred_term: motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  genes:
  - preferred_term: STMN2
    term:
      id: hgnc:10577
      label: STMN2
  - preferred_term: UNC13A
    term:
      id: hgnc:23150
      label: UNC13A
  biological_processes:
  - preferred_term: RNA splicing
    term:
      id: GO:0008380
      label: RNA splicing
    modifier: ABNORMAL
  - preferred_term: nuclear-transcribed mRNA catabolic process, nonsense-mediated decay
    term:
      id: GO:0000184
      label: nuclear-transcribed mRNA catabolic process, nonsense-mediated decay
    modifier: INCREASED
  downstream:
  - target: Axonal Transport Dysfunction
    description: >-
      STMN2 loss and related RNA misprocessing can impair axonal outgrowth,
      axon regeneration, and lysosome trafficking in human motor-neuron models.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - STMN2 depletion
    - impaired axonal regeneration
    - stathmin-2-dependent lysosome trafficking defects
    hypothesis_groups:
    - tdp43_rna_dysregulation_selective_vulnerability_model
    evidence:
    - reference: PMID:36927019
      reference_title: "Mechanism of STMN2 cryptic splice-polyadenylation and its correction for TDP-43 proteinopathies."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Targeting dCasRx or antisense oligonucleotides (ASOs) suppressed cryptic splicing, which restored axonal regeneration and stathmin-2-dependent lysosome trafficking in TDP-43-deficient human motor neurons."
      explanation: >
        Correcting STMN2 cryptic splicing restores axonal regeneration and
        lysosome trafficking in TDP-43-deficient human motor neurons, supporting
        an RNA-misprocessing-to-axon-dysfunction edge.
    - reference: PMID:37996528
      reference_title: Stathmin-2 loss leads to neurofilament-dependent axonal collapse driving motor and sensory denervation.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Persistent stathmin-2 loss in adult mice results in pathologies found in ALS, including reduced interneurofilament spacing, axonal caliber collapse that drives tearing within outer myelin layers, diminished conduction velocity, progressive motor and sensory deficits, and muscle denervation."
      explanation: >-
        Extends the STMN2 arm of this edge from cultured human motor neurons into
        an adult in vivo setting: sustained stathmin-2 depletion degrades
        neurofilament-dependent axoplasmic organization, collapsing axon caliber
        and conduction velocity and producing muscle denervation.
  - target: Motor Neuron Degeneration
    description: >-
      Cryptic-exon misprocessing is modeled as an indirect, target-specific
      bridge from TDP-43 nuclear loss to motor-neuron degeneration through
      STMN2-dependent axonal repair defects, UNC13A-dependent synaptic defects,
      and other transcript-specific losses. Sufficiency of any single target is
      not established: mouse Stmn2 knockout reproduces the distal, fast-fatigable
      neuromuscular-junction denervation seen in ALS but does not produce axon or
      motoneuron degeneration, so this edge should be read as target-specific
      support for the distal arm rather than as a demonstrated route to
      motor-neuron death.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - STMN2 depletion and impaired axonal repair
    - UNC13A nonsense-mediated decay and synaptic dysfunction
    - unresolved additional TDP-43 RNA targets
    hypothesis_groups:
    - tdp43_rna_dysregulation_selective_vulnerability_model
    evidence:
    - reference: PMID:30643292
      reference_title: "ALS-implicated protein TDP-43 sustains levels of STMN2, a mediator of motor neuron growth and repair."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "STMN2 loss upon reduced TDP-43 function was due to altered splicing, which is functionally important, as we show STMN2 is necessary for normal axonal outgrowth and regeneration."
      explanation: >
        STMN2 provides a functional motor-neuron target linking TDP-43 splicing
        loss to impaired axonal growth and repair.
    - reference: PMID:35197628
      reference_title: "TDP-43 loss and ALS-risk SNPs drive mis-splicing and depletion of UNC13A."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Two common intronic UNC13A polymorphisms strongly associated with amyotrophic lateral sclerosis and frontotemporal dementia risk overlap with TDP-43 binding sites."
      explanation: >
        UNC13A provides a human genetic-risk target whose cryptic exon is
        potentiated by TDP-43 loss, supporting a disease-relevant RNA target.
    - reference: PMID:38979232
      reference_title: Loss of TDP-43 induces synaptic dysfunction that is rescued by UNC13A splice-switching ASOs.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "We demonstrate that these deficits are largely driven by a single cryptic exon in UNC13A."
      explanation: >-
        Substantiates the UNC13A-dependent synaptic intermediate listed on this
        edge. The severe reduction in synaptic transmission caused by TDP-43
        depletion is attributed to one UNC13A cryptic exon and is reversed by
        splice-switching antisense oligonucleotides, which is the strongest
        current attribution of a functional deficit to a single cryptic-exon
        event.
    - reference: PMID:35767949
      reference_title: "Loss of Stathmin-2, a hallmark of TDP-43-associated ALS, causes motor neuropathy."
      supports: REFUTE
      evidence_source: MODEL_ORGANISM
      snippet: "Constitutive STMN2 loss results in early-onset sensory and motor neuropathy featuring impaired motor behavior and dramatic distal neuromuscular junction (NMJ) denervation of fast-fatigable motor units, which are selectively vulnerable in ALS, without axon or motoneuron degeneration."
      explanation: >-
        Bears against the sufficiency of the STMN2 arm of this edge. Knocking out
        Stmn2 in mice reproduces the ALS-relevant selective feature — distal
        denervation of the fast-fatigable motor units — but explicitly does not
        produce axon or motoneuron degeneration, so STMN2 loss alone does not
        complete the route to motor-neuron death that this edge describes.
  evidence:
  - reference: PMID:26250685
    reference_title: "TDP-43 repression of nonconserved cryptic exons is compromised in ALS-FTD."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "When TDP-43 was depleted from mouse embryonic stem cells, these cryptic exons were spliced into messenger RNAs, often disrupting their translation and promoting nonsense-mediated decay."
    explanation: >
      Demonstrates the basic cryptic-exon and nonsense-mediated decay mechanism
      caused by TDP-43 depletion.
  - reference: PMID:36927019
    reference_title: "Mechanism of STMN2 cryptic splice-polyadenylation and its correction for TDP-43 proteinopathies."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TDP-43 mislocalization results in cryptic splicing and polyadenylation of pre-messenger RNAs (pre-mRNAs) encoding stathmin-2 (also known as SCG10), a protein that is required for axonal regeneration."
    explanation: >
      Identifies STMN2 cryptic splice-polyadenylation as a direct consequence of
      TDP-43 mislocalization relevant to axonal regeneration.
  - reference: PMID:35197626
    reference_title: "TDP-43 represses cryptic exon inclusion in the FTD-ALS gene UNC13A."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Loss of TDP-43 from the nucleus in human brain, neuronal cell lines and motor neurons derived from induced pluripotent stem cells resulted in the inclusion of a cryptic exon in UNC13A mRNA and reduced UNC13A protein expression."
    explanation: >
      Establishes UNC13A cryptic exon inclusion and reduced protein expression
      after loss of nuclear TDP-43 in human brain and motor-neuron models.
- name: C9orf72 Repeat Expansion Toxicity
  description: >
    Hexanucleotide (GGGGCC) repeat expansion in C9orf72 is the most common genetic cause
    of ALS, accounting for 40% of familial and 5-10% of sporadic cases. The expansion
    leads to RNA foci formation, dipeptide repeat protein aggregation, and haploinsufficiency.
  genes:
  - preferred_term: C9orf72
    term:
      id: hgnc:28337
      label: C9orf72
  evidence:
  - reference: PMID:21944778
    reference_title: "Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS."
    supports: SUPPORT
    snippet: "Analysis of extended clinical series found the C9ORF72 repeat expansion to be the most common genetic abnormality in both familial FTD (11.7%) and familial ALS (23.5%). The repeat expansion leads to the loss of one alternatively spliced C9ORF72 transcript and to formation of nuclear RNA foci, suggesting multiple disease mechanisms."
    explanation: Original discovery paper establishing C9orf72 repeat expansion as a major cause of both FTD and ALS with dual mechanisms.
  - reference: PMID:22406228
    reference_title: "Frequency of the C9orf72 hexanucleotide repeat expansion in patients with amyotrophic lateral sclerosis and frontotemporal dementia: a cross-sectional study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mutation was present in 217 (39·3%) of 552 white individuals with familial ALS from Europe and the USA."
    explanation: Large cross-sectional study quantifies the C9orf72 expansion in ~40% of familial ALS in European/US populations, the source of the widely cited familial-ALS frequency and the strongest support for the node's ~40% figure.
- name: RNA-Binding Protein Mislocalization and Stress Granule Dysfunction
  description: >
    A group of ALS genes encode RNA-binding proteins that share a low-complexity
    or prion-like domain, and their disease alleles act on the same axis: the
    protein's propensity to phase-separate rises, it accumulates in the cytoplasm,
    and stress granules become slow to disassemble. TIA1 low-complexity-domain
    mutations leave non-dynamic granules containing TDP-43; prion-like-domain
    mutations in HNRNPA1 promote self-seeding fibrils and cytoplasmic inclusions;
    FUS mutants mislocalize; and MATR3, an RNA- and DNA-binding protein, interacts
    with TDP-43 and is itself found in ALS spinal cord pathology. This node is
    distinct from the TDP-43 Proteinopathy node below: FUS-mutant ALS in
    particular is TDP-43-negative, so the shared lesion here is RNA-binding
    protein handling rather than TDP-43 specifically. TAF15 is a further FET-family
    RNA-binding protein recorded in this entry's `genetic:` section, but it is not
    bound to this node: its ClinGen gene-disease classification is Limited, and a
    PubMed search for TAF15 with amyotrophic lateral sclerosis returned no report
    placing its ALS-associated variants on the phase-separation or stress-granule
    axis, so the placement is left unmade rather than assumed from FET-family
    membership.
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: Cytoplasmic stress granule assembly
    term:
      id: GO:0034063
      label: cytoplasmic stress granule assembly
    modifier: ABNORMAL
  - preferred_term: Protein localization to nucleus
    term:
      id: GO:0034504
      label: protein localization to nucleus
    modifier: DECREASED
  genes:
  - preferred_term: FUS
    term:
      id: hgnc:4010
      label: FUS
  - preferred_term: TIA1
    term:
      id: hgnc:11802
      label: TIA1
  - preferred_term: HNRNPA1
    term:
      id: hgnc:5031
      label: HNRNPA1
  - preferred_term: MATR3
    term:
      id: hgnc:6912
      label: MATR3
  downstream:
  - target: Motor Neuron Degeneration
    causal_link_type: DIRECT
    description: >
      Cytoplasmic accumulation and aggregation of these RNA-binding proteins is
      accompanied by motor neuron loss in the kindreds in which the mutations
      were found.
  evidence:
  - reference: PMID:28817800
    reference_title: "TIA1 Mutations in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Promote Phase Separation and Alter Stress Granule Dynamics."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In live cells, TIA1 mutations delayed stress granule (SG) disassembly and promoted the accumulation of non-dynamic SGs that harbored TDP-43."
    explanation: >
      The stress granule dynamics defect that gives this node its name, shown for
      TIA1 mutations in live cells.
  - reference: PMID:23455423
    reference_title: "Mutations in prion-like domains in hnRNPA2B1 and hnRNPA1 cause multisystem proteinopathy and ALS."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Notably, the disease mutations promote excess incorporation of hnRNPA2 and hnRNPA1 into stress granules and drive the formation of cytoplasmic inclusions in animal models"
    explanation: >
      The cytoplasmic-inclusion half of this sentence is an animal-model result,
      which is how it is graded. The sentence also covers stress-granule
      incorporation; the cell-free aggregation evidence for that half is the next
      item, so the two claims are carried separately rather than under one grade.
  - reference: PMID:23455423
    reference_title: "Mutations in prion-like domains in hnRNPA2B1 and hnRNPA1 cause multisystem proteinopathy and ALS."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Indeed, the pathogenic mutations strengthen a 'steric zipper' motif in the PrLD, which accelerates the formation of self-seeding fibrils that cross-seed polymerization of wild-type hnRNP."
    explanation: >
      The biochemical half of the hnRNPA1 lesion: prion-like-domain mutations
      raise the protein's intrinsic tendency to polymerize, which is the
      phase-separation propensity this node models.
  - reference: PMID:19251628
    reference_title: "Mutations in FUS, an RNA processing protein, cause familial amyotrophic lateral sclerosis type 6."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Cellular expression studies revealed aberrant localization of mutant FUS protein."
    explanation: >
      Mislocalization of mutant FUS, the reason FUS is bound to this node rather
      than to the TDP-43 node.
  - reference: PMID:24686783
    reference_title: "Mutations in the Matrin 3 gene cause familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our data provide more evidence supporting the role of aberrant RNA processing in motor neuron degeneration."
    explanation: >
      The MATR3 report's own conclusion, placing that gene on the RNA-processing
      axis this node represents.
  - reference: PMID:24686783
    reference_title: "Mutations in the Matrin 3 gene cause familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    snippet: "MATR3 is an RNA- and DNA-binding protein that interacts with TDP-43, a disease protein linked to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia."
    explanation: >
      Source for MATR3's identity as an RNA- and DNA-binding protein that
      interacts with TDP-43, the basis for its membership of this node.

- name: Vesicular and Endolysosomal Trafficking Failure
  description: >
    Three ALS genes act on membrane traffic rather than on RNA or on protein
    degradation directly. VAPB is a vesicle-associated membrane protein whose
    founder allele produces a spectrum of motor neuron disease; ANXA11 is a
    vesicular trafficking protein whose mutations form aggregates in spinal cord
    motor neurons; and FIG4 is the lipid phosphatase that regulates PI(3,5)P2,
    the phosphoinositide whose generating kinase PIKfyve is required for
    retrograde membrane trafficking from endosomes to the trans-Golgi network.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: Vesicle-mediated transport
    term:
      id: GO:0016192
      label: vesicle-mediated transport
    modifier: ABNORMAL
  - preferred_term: Endosomal transport
    term:
      id: GO:0016197
      label: endosomal transport
    modifier: DECREASED
  genes:
  - preferred_term: VAPB
    term:
      id: hgnc:12649
      label: VAPB
  - preferred_term: ANXA11
    term:
      id: hgnc:535
      label: ANXA11
  - preferred_term: FIG4
    term:
      id: hgnc:16873
      label: FIG4
  downstream:
  - target: Motor Neuron Degeneration
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:15372378
    reference_title: "A mutation in the vesicle-trafficking protein VAPB causes late-onset spinal muscular atrophy and amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These data suggest that clinically variable MNDs may be caused by a dysfunction in intracellular membrane trafficking."
    explanation: >
      The VAPB report's own conclusion, and the core claim of this node.
  - reference: PMID:28469040
    reference_title: "Mutations in the vesicular trafficking protein annexin A11 are associated with amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that mutations in ANXA11 are associated with ALS and implicate defective intracellular protein trafficking in disease pathogenesis."
    explanation: >
      Places ANXA11 on the same trafficking axis, on the authors' own conclusion.
  - reference: PMID:19118816
    reference_title: "Deleterious variants of FIG4, a phosphoinositide phosphatase, in patients with ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Mutations of the lipid phosphatase FIG4 that regulates PI(3,5)P(2) are responsible for the recessive peripheral-nerve disorder CMT4J."
    explanation: >
      Source for FIG4's enzymatic identity as the phosphatase acting on
      PI(3,5)P2, which is the basis for placing FIG4 on a membrane-traffic node.
  - reference: PMID:16954148
    reference_title: "The mammalian phosphatidylinositol 3-phosphate 5-kinase (PIKfyve) regulates endosome-to-TGN retrograde transport."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: "These data argue that PIKfyve is predominantly associated with the early endosome, from where it regulates retrograde membrane trafficking to the TGN."
    explanation: >
      PIKfyve is the kinase that generates PI(3,5)P2, and its suppression in
      HeLa cells blocks endosome-to-trans-Golgi retrograde traffic. Indirect for
      FIG4, which this study does not examine, but it is the source for the
      transport step this node assigns to FIG4's substrate lipid.

- name: Neuregulin-ErbB4 Signaling Failure
  description: >
    ERBB4 encodes the receptor tyrosine kinase for neuregulin-1. ALS-associated
    ERBB4 mutations reduce ErbB4 autophosphorylation on neuregulin-1 stimulation,
    so the lesion is a weakened receptor signal rather than an aggregating or
    otherwise toxic protein species.
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: ERBB4 signaling pathway
    term:
      id: GO:0038130
      label: ERBB4 signaling pathway
    modifier: DECREASED
  genes:
  - preferred_term: ERBB4
    term:
      id: hgnc:3432
      label: ERBB4
  downstream:
  - target: Motor Neuron Degeneration
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:24119685
    reference_title: "ERBB4 mutations that disrupt the neuregulin-ErbB4 pathway cause amyotrophic lateral sclerosis type 19."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Functional analysis revealed that these mutations led to a reduced autophosphorylation of ErbB4 upon neuregulin-1 (NRG-1) stimulation."
    explanation: >
      The measured signalling deficit this node represents.
  - reference: PMID:24119685
    reference_title: "ERBB4 mutations that disrupt the neuregulin-ErbB4 pathway cause amyotrophic lateral sclerosis type 19."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "This study indicates that disruption of the neuregulin-ErbB4 pathway is involved in the pathogenesis of ALS and potentially paves the way for the development of innovative therapeutic strategies such using NRGs or their agonists to upregulate ErbB4 functions."
    explanation: >
      The authors' conclusion that disruption of this pathway is involved in ALS
      pathogenesis.

- name: Angiogenin Loss of Function
  description: >
    ALS-associated ANG alleles are complete loss-of-function: the mutant protein
    is deficient in ribonuclease activity, in nuclear translocation, or in both.
    Angiogenin is expressed in motor neurons as well as in endothelial cells of
    normal human spinal cord, so the loss is not confined to the vasculature.
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: Motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  - preferred_term: Endothelial cell
    term:
      id: CL:0000115
      label: endothelial cell
  molecular_functions:
  - preferred_term: ribonuclease activity
    term:
      id: GO:0004540
      label: RNA nuclease activity
    modifier: DECREASED
  genes:
  - preferred_term: ANG
    term:
      id: hgnc:483
      label: ANG
  downstream:
  - target: Motor Neuron Degeneration
    causal_link_type: DIRECT
  notes: >
    Split from a combined neurotrophic/angiogenic node. The angiogenesis GO
    process that node carried is deliberately not repeated here: angiogenesis is
    not a motor-neuron process, and the functional deficit the source measures is
    in the protein's ribonucleolytic and nuclear-translocation activity, with the
    angiogenesis assay used as the readout for that deficit.
  evidence:
  - reference: PMID:17886298
    reference_title: "Angiogenin loss-of-function mutations in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The mutant ANG proteins are unable to induce angiogenesis because of a deficiency in ribonuclease activity, nuclear translocation, or both."
    explanation: >
      Establishes the ANG lesion as loss of ribonucleolytic activity, of nuclear
      translocation, or of both, which is what this node asserts.
  - reference: PMID:17886298
    reference_title: "Angiogenin loss-of-function mutations in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "As a correlate, we demonstrate strong ANG expression in both endothelial cells and motor neurons of normal human spinal cords from the developing fetus and adult."
    explanation: >
      Source for the two cell types bound to this node, and for reading the loss
      of function as motor-neuron-relevant rather than purely vascular.
- name: Glutamate Excitotoxicity
  conforms_to: "glutamate_excitotoxicity#Excessive Glutamatergic Stimulation and Impaired Glutamate Clearance"
  description: >
    Impaired glutamate clearance by astrocytes leads to excessive glutamate accumulation
    in the synaptic cleft, causing prolonged activation of glutamate receptors on motor
    neurons. This results in calcium overload and subsequent neuronal death.
  cell_types:
  - preferred_term: astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  biological_processes:
  - preferred_term: neurotransmitter transport
    term:
      id: GO:0006836
      label: neurotransmitter transport
  evidence:
  - reference: PMID:8302340
    reference_title: "A controlled trial of riluzole in amyotrophic lateral sclerosis. ALS/Riluzole Study Group."
    supports: SUPPORT
    snippet: "Some research suggests that the excitatory amino acid neurotransmitter glutamate may be involved in the pathogenesis."
    explanation: Trial of riluzole, an antiglutamate agent, supports role of glutamate excitotoxicity in ALS pathogenesis.
  - reference: PMID:40508048
    reference_title: "Amyotrophic Lateral Sclerosis: Pathophysiological Mechanisms and Treatment Strategies (Part 2)."
    supports: SUPPORT
    snippet: "understanding of the key pathogenetic links of ALS, including glutamate-mediated excitotoxicity and oxidative stress, has significantly advanced."
    explanation: Recent mechanistic review highlights glutamate-mediated excitotoxicity as a key pathogenic process and therapeutic target in ALS.
  - reference: PMID:42429860
    reference_title: "Human iPSC-Derived Spinal Neurons Carrying the ALS FUS (P525L) Mutation Exhibit Lower Response to Inhibitory Neurotransmitters."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: IN_VITRO
    snippet: "a strong decrease of inhibitory transmission, which may affect the excitatory/inhibitory balance, possibly predisposing to excitotoxicity and neurodegeneration"
    explanation: In FUS (P525L) hiPSC-derived spinal neurons, reduced GABA and glycine responses are proposed to shift the excitatory/inhibitory balance toward excitotoxicity. This is an authors' hypothesis from an in vitro model, so it is indirect support for the node.
- name: Oxidative Stress
  description: >
    Motor neurons are particularly vulnerable to oxidative damage due to high metabolic
    demands. Mutations in SOD1, which encodes superoxide dismutase 1, lead to misfolded
    protein aggregation and increased oxidative stress contributing to neuronal death.
  genes:
  - preferred_term: SOD1
    term:
      id: hgnc:11179
      label: SOD1
  biological_processes:
  - preferred_term: response to oxidative stress
    term:
      id: GO:0006979
      label: response to oxidative stress
  evidence:
  - reference: PMID:8446170
    reference_title: "Mutations in Cu/Zn superoxide dismutase gene are associated with familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "a gene that encodes a cytosolic, Cu/Zn-binding superoxide dismutase (SOD1), a homodimeric metalloenzyme that catalyzes the dismutation of the toxic superoxide anion"
    explanation: Discovery of SOD1 mutations in familial ALS implicates oxidative stress in disease pathogenesis.
  - reference: PMID:40508048
    reference_title: "Amyotrophic Lateral Sclerosis: Pathophysiological Mechanisms and Treatment Strategies (Part 2)."
    supports: SUPPORT
    snippet: "This review considers the recent evidence on molecular mechanisms of these processes, as well as the therapeutic strategies aimed at their modulation. Special attention is paid to antiglutamatergic and antioxidant drugs as approaches to the ALS pathogenetic therapy."
    explanation: Review emphasizes oxidative stress as a targetable pathogenic mechanism and discusses antioxidant therapeutic strategies in ALS.
  - reference: PMID:35269543
    reference_title: "Comprehensive Research on Past and Future Therapeutic Strategies Devoted to Treatment of Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    snippet: "ALS has a multifaceted nature affected by many pathological mechanisms, including oxidative stress (also via protein aggregation), mitochondrial dysfunction, glutamate-induced excitotoxicity, apoptosis, neuroinflammation, axonal degeneration, skeletal muscle deterioration and viruses."
    explanation: Therapeutic strategies review highlights oxidative stress among key pathological mechanisms contributing to ALS.
- name: Cellular Senescence in Motor Cortex and Spinal Cord
  conforms_to: "cellular_senescence#Senescent Cell Accumulation"
  description: >
    Molecular markers of cellular senescence appear in the motor cortex and spinal
    cord early in disease, alongside declining neural and neuromuscular function.
    The evidence is from TDP-43(Q331K) mice; cortical microglia are the implicated
    cell type, as a candidate mediator of the benefit seen when senescent cells are
    cleared pharmacologically. Senescence is marked by irreversible cell-cycle arrest
    and a pro-inflammatory senescence-associated secretory phenotype, which is the
    route by which it is proposed to reach neuroinflammation; the specific secreted
    factors operating in ALS are not established here.
  notes: >-
    Scoped to what the cited mouse study shows. It does not report senescence in
    motor neurons themselves, so no motor neuron cell type is bound - preserved
    layer V neuron counts under senolytic treatment are an outcome, not evidence
    that those neurons were senescent. Astrocytes are likewise not named. Only the
    TDP-43(Q331K) allele is studied, so the node makes no claim about senescence
    downstream of SOD1 or C9orf72.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  biological_processes:
  - preferred_term: cellular senescence
    term:
      id: GO:0090398
      label: cellular senescence
    modifier: INCREASED
  downstream:
  - target: Neuroinflammation
    description: >-
      Proposed route from senescent cell accumulation to the neuroinflammation node:
      senescent cells carry a pro-inflammatory secretory phenotype, and cortical
      microglia are the candidate mediator of senolytic benefit in this model. The
      cited study measured microglial TDP-43 burden and senescence markers rather
      than neuroinflammation itself.
    evidence:
    - reference: PMID:42759848
      reference_title: "Cellular senescence is an early feature and therapeutic target in amyotrophic lateral sclerosis TDP-43 Q331K mice"
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: MODEL_ORGANISM
      snippet: "cortical microglia were implicated as a potential mediator of senolytic benefits based on reduced microglial TDP-43 burden and senescence markers"
      explanation: >
        Supports the link only through the response to senolytic treatment in mice:
        the quote reports microglia as a potential mediator, and neuroinflammation
        was not among the measured outcomes, so the inference to this edge is indirect.
  evidence:
  - reference: PMID:42759848
    reference_title: "Cellular senescence is an early feature and therapeutic target in amyotrophic lateral sclerosis TDP-43 Q331K mice"
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "molecular markers of cellular senescence emerge in the motor cortex and spinal cord alongside declines in neural and neuromuscular function in TDP-43Q331K ALS mice, supporting senescence as an early feature of ALS pathology"
    explanation: >
      Locates the senescence markers in motor cortex and spinal cord and times them
      early relative to functional decline, which is what this node asserts.
  - reference: PMID:42759848
    reference_title: "Cellular senescence is an early feature and therapeutic target in amyotrophic lateral sclerosis TDP-43 Q331K mice"
    supports: SUPPORT
    quote_role: BACKGROUND
    evidence_source: OTHER
    snippet: "cellular senescence - a hallmark of aging marked by irreversible cell-cycle arrest and a pro-inflammatory senescence-associated secretory phenotype - has been implicated in neurodegeneration, yet its role in ALS progression remains incompletely understood"
    explanation: >
      Source for the SASP characterization in this node's description. It is the
      paper's framing of established work rather than its own result, which is why
      it is graded BACKGROUND and not attributed to the mouse experiments.
- name: Neuroinflammation
  description: >
    Activated microglia and astrocytes contribute to motor neuron death non-cell-autonomously.
    In mutant SOD1 mice, lowering mutant SOD1 in microglia slows later disease progression
    without changing onset; astrocytes derived from both familial and sporadic ALS patients
    kill motor neurons in co-culture through secreted factors and upregulate inflammatory
    genes. The specific neurotoxic mediators are not settled.
  conforms_to: "neuroinflammation_glial_activation#Reactive Microglial and Astrocytic Activation"
  cell_types:
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  - preferred_term: astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  biological_processes:
  - preferred_term: Microglial activation
    term:
      id: GO:0001774
      label: microglial cell activation
    modifier: INCREASED
  - preferred_term: Astrocyte activation
    term:
      id: GO:0048143
      label: astrocyte activation
    modifier: INCREASED
  downstream:
  - target: Motor Neuron Degeneration
    description: >-
      Reactive microglia and astrocytes contribute to motor neuron death non-cell-autonomously:
      mutant SOD1 in microglia drives later disease progression in mice, and astrocytes from
      familial and sporadic ALS patients kill motor neurons in co-culture.
    evidence:
    - reference: PMID:16741123
      reference_title: "Onset and progression in inherited ALS determined by motor neurons and microglia."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Diminishing the mutant levels in microglia had little effect on the early disease phase but sharply slowed later disease progression."
      explanation: >-
        Lowering mutant SOD1 only in microglia slows the later, progressive phase of motor neuron
        disease in mice, so microglia contribute to the degeneration rather than only reflecting it.
    - reference: PMID:21832997
      reference_title: "Astrocytes from familial and sporadic ALS patients are toxic to motor neurons."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Using astrocytes generated from postmortem tissue from both FALS and SALS patients, we show that astrocytes derived from both patient groups are similarly toxic to motor neurons."
      explanation: >-
        Astrocytes derived from familial and sporadic ALS patients kill motor neurons in co-culture,
        a direct glia-to-motor-neuron toxic effect.
  evidence:
  - reference: PMID:15056468
    reference_title: "Evidence of widespread cerebral microglial activation in amyotrophic lateral sclerosis: an [11C](R)-PK11195 positron emission tomography study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Significantly increased binding was found in motor cortex (P = 0.003), pons (P = 0.004), dorsolateral prefrontal cortex (P = 0.010) and thalamus (P = 0.005) in the ALS patients, with significant correlation between binding in the motor cortex and the burden of upper motor neuron signs clinically (r = 0.73, P = 0.009)."
    explanation: >-
      [11C](R)-PK11195 PET in 10 ALS patients against 14 controls shows increased binding of this
      marker of activated microglia in motor and extra-motor regions, with motor-cortex binding
      tracking upper motor neuron signs. This is in vivo human evidence for the microglial arm
      of this node.
  - reference: PMID:16741123
    reference_title: "Onset and progression in inherited ALS determined by motor neurons and microglia."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Diminishing the mutant levels in microglia had little effect on the early disease phase but sharply slowed later disease progression."
    explanation: >-
      Cell-type-specific deletion of mutant SOD1 in mice shows that microglia drive disease
      progression, the non-cell-autonomous microglial arm of this node.
  - reference: PMID:21832997
    reference_title: "Astrocytes from familial and sporadic ALS patients are toxic to motor neurons."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Using astrocytes generated from postmortem tissue from both FALS and SALS patients, we show that astrocytes derived from both patient groups are similarly toxic to motor neurons."
    explanation: >-
      Patient-derived astrocytes, including from sporadic ALS, are toxic to motor neurons in
      co-culture, supporting the astrocyte arm of this node beyond SOD1 mouse models.
  - reference: PMID:21832997
    reference_title: "Astrocytes from familial and sporadic ALS patients are toxic to motor neurons."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Upon co-culture with MNs, we observed that inflammatory gene expression is upregulated within fALS and sALS astrocytes."
    explanation: >-
      Supports the inflammatory activation of ALS astrocytes; the same study shows toxicity is
      transmitted by conditioned medium, i.e. by secreted factors.
  - reference: PMID:34874625
    reference_title: "Microglial TREM2 in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: "The involvement of nonmotor neuraxis emphasizes the contribution of glial cells in disease progress."
    explanation: Review statement that glial cells contribute to ALS disease progression; general framing for the node rather than evidence for a specific mediator.
- name: Microglial TREM2 Signaling
  description: >
    TREM2 expressed on microglia regulates proliferation, activation, and phagocytosis; altered
    TREM2 signaling is implicated in ALS progression through dysregulated microglial responses
    to motor neuron injury.
  cell_types:
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  genes:
  - preferred_term: TREM2
    term:
      id: hgnc:17761
      label: TREM2
  biological_processes:
  - preferred_term: microglial cell activation
    term:
      id: GO:0001774
      label: microglial cell activation
  evidence:
  - reference: PMID:34874625
    reference_title: "Microglial TREM2 in amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Triggering receptor expressed on myeloid cell 2 (TREM2) is a surface receptor that, within the CNS, is exclusively expressed on microglia and plays crucial roles in microglial proliferation, migration, activation, metabolism, and phagocytosis."
    explanation: Review summarizes how microglial TREM2 function shapes ALS progression and highlights its role in microglial activation.
- name: Axonal Transport Dysfunction
  description: >
    Impaired axonal transport leads to accumulation of organelles and proteins in motor
    neuron axons, contributing to neurodegeneration. Gene mutations affecting cytoskeletal
    components (KIF5A, DCTN1, PFN1) contribute to this dysfunction.
  genes:
  - preferred_term: KIF5A
    term:
      id: hgnc:6323
      label: KIF5A
  - preferred_term: DCTN1
    term:
      id: hgnc:2711
      label: DCTN1
  - preferred_term: PFN1
    term:
      id: hgnc:8881
      label: PFN1
  - preferred_term: NEFH
    term:
      id: hgnc:7737
      label: NEFH
  - preferred_term: PRPH
    term:
      id: hgnc:9461
      label: PRPH
  - preferred_term: ARHGEF28
    term:
      id: hgnc:30322
      label: ARHGEF28
  biological_processes:
  - preferred_term: anterograde axonal transport
    term:
      id: GO:0008089
      label: anterograde axonal transport
  evidence:
  - reference: PMID:22312314
    reference_title: "Disruption of axonal transport in motor neuron diseases."
    supports: SUPPORT
    snippet: "Axonal transport defects are among the early molecular events leading to neurodegeneration in mouse models of amyotrophic lateral sclerosis (ALS)."
    explanation: Review confirms axonal transport defects as early pathogenic events in ALS.
  - reference: PMID:41890591
    reference_title: "Axonal transport impairment as an upstream mechanism in amyotrophic lateral sclerosis pathogenesis."
    supports: SUPPORT
    evidence_source: OTHER
    directness: INDIRECT
    snippet: "Across many ALS models, including SOD1, TARDBP (TDP-43), FUS, and C9orf72, transport deficits are frequently detectable in presymptomatic stages, often preceding overt motor neuron loss or clinical manifestation, although temporal ordering varies by molecular subtype."
    explanation: >-
      Synthesis across SOD1, TARDBP, FUS and C9orf72 systems reporting
      presymptomatic transport deficits, which is why this node is retained as a
      cross-genotype rather than a genotype-specific lesion. It is a
      single-author review proposing axonal transport impairment as the upstream
      convergence point; the quoted sentence itself notes that temporal ordering
      varies by subtype, so it is recorded here as indirect support for the
      framework and not as evidence that transport failure is the initiating
      human ALS lesion.
- name: Impaired Autophagy
  conforms_to: "disabled_macroautophagy#Failure of Cytoplasmic Quality Control"
  description: >
    Defects in autophagy and protein quality control pathways lead to accumulation of
    misfolded proteins and damaged organelles in motor neurons. Multiple ALS genes
    (TBK1, OPTN, VCP, SQSTM1) function in autophagy.
  genes:
  - preferred_term: TBK1
    term:
      id: hgnc:11584
      label: TBK1
  - preferred_term: OPTN
    term:
      id: hgnc:17142
      label: OPTN
  - preferred_term: VCP
    term:
      id: hgnc:12666
      label: VCP
  - preferred_term: SQSTM1
    term:
      id: hgnc:11280
      label: SQSTM1
  - preferred_term: UBQLN2
    term:
      id: hgnc:12509
      label: UBQLN2
  - preferred_term: CCNF
    term:
      id: hgnc:1591
      label: CCNF
  biological_processes:
  - preferred_term: autophagy
    term:
      id: GO:0006914
      label: autophagy
  evidence:
  - reference: PMID:28148298
    reference_title: "TBK1: a new player in ALS linking autophagy and neuroinflammation."
    supports: SUPPORT
    snippet: "TBK1 also has a major role in autophagy and mitophagy, chiefly the phosphorylation of autophagy adaptors. Several other ALS genes are also involved in autophagy, including p62 and OPTN."
    explanation: Review describes TBK1's role in autophagy and confirms multiple ALS genes function in autophagy pathways.
  - reference: PMID:21857683
    reference_title: "Mutations in UBQLN2 cause dominant X-linked juvenile and adult-onset ALS and ALS/dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here we show that mutations in UBQLN2, which encodes the ubiquitin-like protein ubiquilin 2, cause dominantly inherited, chromosome-X-linked ALS and ALS/dementia."
    explanation: >
      Identifies ubiquilin 2, a ubiquitin-like shuttle in protein quality control,
      as an ALS gene; this is the basis for binding UBQLN2 to this node.
  - reference: PMID:27080313
    reference_title: "CCNF mutations in amyotrophic lateral sclerosis and frontotemporal dementia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Expression of mutant CCNF in neuronal cells caused abnormal ubiquitination and accumulation of ubiquitinated proteins, including TDP-43 and a SCF(Cyclin F) substrate."
    explanation: >
      Places the CCNF lesion in ubiquitination and protein-homeostasis failure,
      the process this node models.
- name: TDP-43-Driven Glycolytic Failure
  description: >
    Cytoplasmic TDP-43 directly binds hexokinase 1 (HK1), the first rate-limiting
    enzyme of glycolysis, dissociating it from mitochondria and sequestering it
    into insoluble aggregates. The resulting loss of HK1 impairs glycolytic ATP
    production in motor neurons — a metabolic lesion observed consistently across
    TDP-43 mutant mice, patient-derived iPSC motor neurons, and ALS postmortem
    spinal cord. Compensating for HK1 loss reduces cytoplasmic TDP-43 and
    ubiquitin accumulation and improves motor performance and survival in models,
    marking a metabolic intervention point within the canonical proteostatic-failure
    framework.
  cell_types:
  - preferred_term: motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  genes:
  - preferred_term: HK1
    term:
      id: hgnc:4922
      label: HK1
  - preferred_term: TARDBP
    term:
      id: hgnc:11571
      label: TARDBP
  biological_processes:
  - preferred_term: glycolytic process
    term:
      id: GO:0006096
      label: glycolytic process
    modifier: DECREASED
  downstream:
  - target: Motor Neuron Degeneration
    description: >-
      Loss of HK1-dependent glycolytic ATP production contributes to the
      bioenergetic failure of vulnerable motor neurons.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - impaired glycolytic ATP production
    - motor neuron bioenergetic failure
    evidence:
    - reference: PMID:41838122
      reference_title: "TDP-43 impairs glycolysis by sequestering hexokinase 1 in amyotrophic lateral sclerosis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "postmortem spinal cord tissue from ALS patients, we observe consistent decreases in HK1 protein level"
      explanation: >-
        Reduced HK1 in ALS patient spinal cord links the glycolytic lesion to
        human motor neuron degeneration.
    - reference: PMID:41838122
      reference_title: "TDP-43 impairs glycolysis by sequestering hexokinase 1 in amyotrophic lateral sclerosis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "compensation for HK1 loss reduces cytoplasmic TDP-43 and ubiquitin accumulation, improves motor performance, and prolongs survival"
      explanation: >-
        Restoring HK1 (glycolytic rescue) by AAV-HK1 overexpression in the motor
        cortex of TDP-43A315T mice reduces cytoplasmic TDP-43 and ubiquitin,
        improves motor performance, and prolongs survival — interventional
        confirmation that the HK1 glycolytic lesion contributes causally to the
        motor-neuron degeneration downstream of TDP-43 proteinopathy.
  evidence:
  - reference: PMID:41838122
    reference_title: "TDP-43 impairs glycolysis by sequestering hexokinase 1 in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "cytoplasmic TDP-43 directly disrupts glycolysis by targeting hexokinase 1 (HK1), the first rate-limiting enzyme of the pathway"
    explanation: >-
      Identifies HK1 sequestration by cytoplasmic TDP-43 as a direct metabolic
      mechanism — a novel addition to the canonical proteostatic-failure model
      surfaced by the 2026 hypothesis-search report.
  - reference: PMID:41838122
    reference_title: "TDP-43 impairs glycolysis by sequestering hexokinase 1 in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "postmortem spinal cord tissue from ALS patients, we observe consistent decreases in HK1 protein level"
    explanation: >-
      Consistent HK1 decreases in ALS postmortem spinal cord confirm the
      glycolytic lesion in human disease tissue.
- name: Endogenous Retrovirus Reactivation and TDP-43 Feedback
  description: >
    Reactivation of endogenous retroviruses (ERVs), in particular human
    endogenous retrovirus type K (HERV-K/HML-2), and TDP-43 proteinopathy are
    mutually reinforcing. ERV expression is sufficient to stimulate cytoplasmic
    aggregation of TDP-43, and viral ERV transmission propagates TDP-43 pathology
    to recipient cells, providing a self-sustaining positive-feedback loop that
    can drive intercellular spread and disease progression. ERV transcripts are
    elevated in ALS brain, and this loop is the mechanistic rationale for
    repurposing antiretroviral therapy (e.g., Triumeq) in ALS.
  cell_types:
  - preferred_term: motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  downstream:
  - target: TDP-43 Proteinopathy
    description: >-
      ERV (HERV-K) expression is sufficient to stimulate cytoplasmic TDP-43
      aggregation, closing a feed-forward loop with TDP-43 proteinopathy.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:36810738
      reference_title: "Endogenous retroviruses and TDP-43 proteinopathy form a sustaining feedback driving intercellular spread of Drosophila neurodegeneration."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "each sufficient to stimulate cytoplasmic aggregation of human TDP-43"
      explanation: >-
        ERV expression is sufficient to seed cytoplasmic TDP-43 aggregation,
        establishing the ERV-to-TDP-43 arm of the feedback loop.
  - target: Motor Neuron Degeneration
    description: >-
      Viral ERV transmission propagates TDP-43 pathology to recipient cells,
      providing a mechanism for intercellular spread of degeneration.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - intercellular ERV transmission
    - templated TDP-43 pathology in recipient neurons
    evidence:
    - reference: PMID:36810738
      reference_title: "Endogenous retroviruses and TDP-43 proteinopathy form a sustaining feedback driving intercellular spread of Drosophila neurodegeneration."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Viral ERV transmission also triggers TDP-43 pathology in recipient cells"
      explanation: >-
        ERV transmission propagates TDP-43 pathology between cells, supporting an
        ERV-driven spread mechanism for disease progression.
  evidence:
  - reference: PMID:36810738
    reference_title: "Endogenous retroviruses and TDP-43 proteinopathy form a sustaining feedback driving intercellular spread of Drosophila neurodegeneration."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "each sufficient to stimulate cytoplasmic aggregation of human TDP-43"
    explanation: >-
      Drosophila and human-ERV experiments show ERV expression seeds cytoplasmic
      TDP-43 aggregation, the basis of the ERV-TDP-43 feedback loop.
  - reference: PMID:37450244
    reference_title: "The Molecular Link Between TDP-43, Endogenous Retroviruses and Inflammatory Neurodegeneration in Amyotrophic Lateral Sclerosis: a Potential Target for Triumeq, an Antiretroviral Therapy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "human endogenous retrovirus type K (HERV-K), have been proposed to be involved in the propagation of neurodegeneration in ALS"
    explanation: >-
      Review articulating the HERV-K/TDP-43 propagation model and its rationale
      as a target for antiretroviral therapy (Triumeq) in ALS.
phenotypes:
- name: Generalized Muscle Weakness
  category: Neuromuscular
  frequency: OBLIGATE
  diagnostic: true
  description: Progressive loss of voluntary muscle strength affecting limbs, trunk, and respiratory muscles.
  phenotype_term:
    preferred_term: Generalized muscle weakness
    term:
      id: HP:0003324
      label: Generalized muscle weakness
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0003324 | Generalized muscle weakness | Very frequent (99-80%)"
    explanation: Orphanet lists generalized muscle weakness as very frequent in ALS.
  - reference: PMID:38891021
    reference_title: "Updates on Disease Mechanisms and Therapeutics for Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    snippet: "upper and lower motor neurons in the brain and spinal cord progressively degenerate during the course of the disease, leading to the loss of the voluntary movement of the arms and legs."
    explanation: Review summarizes progressive motor neuron degeneration causing loss of voluntary movement.
- name: Neurodegeneration
  category: Neurological
  frequency: OBLIGATE
  description: Progressive degeneration of upper and lower motor neurons, the hallmark of ALS.
  phenotype_term:
    preferred_term: Neurodegeneration
    term:
      id: HP:0002180
      label: Neurodegeneration
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002180 | Neurodegeneration | Very frequent (99-80%)"
    explanation: Orphanet lists neurodegeneration as very frequent in ALS.
  - reference: PMID:36116464
    reference_title: "Amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Amyotrophic lateral sclerosis is a fatal CNS neurodegenerative disease."
    explanation: Lancet Seminar identifies ALS as a fatal CNS neurodegenerative disease.
- name: Motor Neuron Atrophy
  category: Neurological
  frequency: VERY_FREQUENT
  description: Loss of motor neurons in cortex, brainstem, and spinal cord.
  phenotype_term:
    preferred_term: Motor neuron atrophy
    term:
      id: HP:0007373
      label: Motor neuron atrophy
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0007373 | Motor neuron atrophy | Very frequent (99-80%)"
    explanation: Orphanet lists motor neuron atrophy as very frequent in ALS.
- name: Fasciculations
  category: Neuromuscular
  frequency: FREQUENT
  diagnostic: true
  description: Visible involuntary muscle twitching resulting from spontaneous motor unit discharges.
  phenotype_term:
    preferred_term: Fasciculations
    term:
      id: HP:0002380
      label: Fasciculations
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002380 | Fasciculations | Frequent (79-30%)"
    explanation: Orphanet lists fasciculations as frequent in ALS.
  - reference: PMID:27117334
    reference_title: "Lower motor neuron dysfunction in ALS."
    supports: SUPPORT
    snippet: "In the LMN system, fasciculation potentials (FPs) are the earliest changes observed in affected muscles, a feature of LMN hyperexcitability."
    explanation: Review confirms fasciculations are an early marker of lower motor neuron dysfunction in ALS.
- name: Spasticity
  category: Neurological
  frequency: FREQUENT
  description: Increased muscle tone and stiffness due to upper motor neuron involvement.
  phenotype_term:
    preferred_term: Spasticity
    term:
      id: HP:0001257
      label: Spasticity
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0001257 | Spasticity | Frequent (79-30%)"
    explanation: Orphanet lists spasticity as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Upper motor findings include spasticity, hyperactive reflexes, and a positive Babinski sign."
    explanation: StatPearls article confirms spasticity as a cardinal upper motor neuron sign in ALS.
- name: Hyperreflexia
  category: Neurological
  frequency: FREQUENT
  description: Exaggerated deep tendon reflexes indicating upper motor neuron dysfunction.
  phenotype_term:
    preferred_term: Hyperreflexia
    term:
      id: HP:0001347
      label: Hyperreflexia
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0001347 | Hyperreflexia | Frequent (79-30%)"
    explanation: Orphanet lists hyperreflexia as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Upper motor findings include spasticity, hyperactive reflexes, and a positive Babinski sign."
    explanation: StatPearls review lists hyperactive reflexes as a core upper motor neuron finding in ALS.
- name: Babinski Sign
  category: Neurological
  frequency: FREQUENT
  diagnostic: true
  description: Extensor plantar response indicating upper motor neuron dysfunction.
  phenotype_term:
    preferred_term: Babinski sign
    term:
      id: HP:0003487
      label: Babinski sign
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0003487 | Babinski sign | Frequent (79-30%)"
    explanation: Orphanet lists Babinski sign as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Upper motor findings include spasticity, hyperactive reflexes, and a positive Babinski sign."
    explanation: StatPearls review confirms positive Babinski sign as an upper motor neuron finding in ALS.
- name: Hoffmann Sign
  category: Neurological
  frequency: FREQUENT
  description: Pathological reflex of the hand indicating upper motor neuron dysfunction in the cervical cord.
  phenotype_term:
    preferred_term: Hoffmann sign
    term:
      id: HP:0031993
      label: Hoffmann sign
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0031993 | Hoffmann sign | Frequent (79-30%)"
    explanation: Orphanet lists Hoffmann sign as frequent in ALS.
- name: Dysarthria
  category: Neurological
  frequency: FREQUENT
  description: Difficulty with speech articulation due to weakness of bulbar muscles.
  phenotype_term:
    preferred_term: Dysarthria
    term:
      id: HP:0001260
      label: Dysarthria
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0001260 | Dysarthria | Frequent (79-30%)"
    explanation: Orphanet lists dysarthria as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Bulbar dysfunction can manifest as dysphagia (trouble swallowing) and dysarthria (trouble speaking)."
    explanation: Review notes bulbar dysfunction in ALS commonly presents with dysarthria and dysphagia.
- name: Dysphonia
  category: Neurological
  frequency: FREQUENT
  description: Voice changes and hoarseness due to weakness of laryngeal muscles.
  phenotype_term:
    preferred_term: Dysphonia
    term:
      id: HP:0001618
      label: Dysphonia
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0001618 | Dysphonia | Frequent (79-30%)"
    explanation: Orphanet lists dysphonia as frequent in ALS.
- name: Dysphagia
  category: Neurological
  frequency: FREQUENT
  description: Difficulty swallowing due to weakness of pharyngeal and esophageal muscles.
  phenotype_term:
    preferred_term: Dysphagia
    term:
      id: HP:0002015
      label: Dysphagia
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002015 | Dysphagia | Frequent (79-30%)"
    explanation: Orphanet lists dysphagia as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Bulbar dysfunction can manifest as dysphagia (trouble swallowing) and dysarthria (trouble speaking)."
    explanation: StatPearls article highlights dysphagia as a common bulbar manifestation in ALS.
  - reference: PMID:39207520
    reference_title: "Narrative review of diagnosis, management and treatment of dysphagia and sialorrhea in amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Throughout the disease, more than two-thirds of ALS patients experience dysphagia, regardless of the region of onset."
    explanation: Dysphagia-focused review reports that swallowing difficulty affects the majority of ALS patients.
- name: Drooling
  category: Neurological
  frequency: FREQUENT
  description: Excessive salivation due to impaired swallowing of saliva from bulbar motor neuron involvement.
  phenotype_term:
    preferred_term: Drooling
    term:
      id: HP:0002307
      label: Drooling
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002307 | Drooling | Frequent (79-30%)"
    explanation: Orphanet lists drooling as frequent in ALS.
  - reference: PMID:34920148
    reference_title: "Prevalence of Sialorrhea Among Amyotrophic Lateral Sclerosis Patients: A Systematic Review and Meta-Analysis."
    supports: SUPPORT
    snippet: "The pooled prevalence of sialorrhea among ALS patients was 30.8% (95% CI: 20.0%-44.2%)."
    explanation: Meta-analysis establishes pooled sialorrhea prevalence of 30.8% in ALS patients.
- name: Fatigable Weakness of Bulbar Muscles
  category: Neuromuscular
  frequency: FREQUENT
  description: Worsening of bulbar muscle function with repeated use, affecting speech and swallowing.
  phenotype_term:
    preferred_term: Fatigable weakness of bulbar muscles
    term:
      id: HP:0030192
      label: Fatigable weakness of bulbar muscles
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0030192 | Fatigable weakness of bulbar muscles | Frequent (79-30%)"
    explanation: Orphanet lists fatigable weakness of bulbar muscles as frequent in ALS.
- name: Fatigable Weakness of Swallowing Muscles
  category: Neuromuscular
  frequency: FREQUENT
  description: Worsening of swallowing function with repeated use due to progressive motor neuron loss.
  phenotype_term:
    preferred_term: Fatigable weakness of swallowing muscles
    term:
      id: HP:0030195
      label: Fatigable weakness of swallowing muscles
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0030195 | Fatigable weakness of swallowing muscles | Frequent (79-30%)"
    explanation: Orphanet lists fatigable weakness of swallowing muscles as frequent in ALS.
- name: Fatigable Weakness of Respiratory Muscles
  category: Respiratory
  frequency: FREQUENT
  description: Worsening respiratory muscle function with use, contributing to ventilatory failure.
  phenotype_term:
    preferred_term: Fatigable weakness of respiratory muscles
    term:
      id: HP:0030196
      label: Fatigable weakness of respiratory muscles
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0030196 | Fatigable weakness of respiratory muscles | Frequent (79-30%)"
    explanation: Orphanet lists fatigable weakness of respiratory muscles as frequent in ALS.
- name: Respiratory Insufficiency
  category: Respiratory
  frequency: FREQUENT
  description: Progressive weakness of diaphragm and intercostal muscles leading to ventilatory failure. This is the most common cause of death in ALS.
  phenotype_term:
    preferred_term: Respiratory insufficiency due to muscle weakness
    term:
      id: HP:0002747
      label: Respiratory insufficiency due to muscle weakness
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002878 | Respiratory failure | Frequent (79-30%)"
    explanation: Orphanet lists respiratory failure (HP:0002878) as frequent; this entry uses the more specific HP:0002747 (respiratory insufficiency due to muscle weakness) which captures the neuromuscular etiology.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Death usually occurs within 2 to 5 years from respiratory failure."
    explanation: Clinical overview states respiratory failure is the usual terminal event in ALS.
- name: Abnormality on Pulmonary Function Testing
  category: Respiratory
  frequency: FREQUENT
  description: Reduced forced vital capacity and other pulmonary function parameters due to respiratory muscle weakness.
  phenotype_term:
    preferred_term: Abnormality on pulmonary function testing
    term:
      id: HP:0030878
      label: Abnormality on pulmonary function testing
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0030878 | Abnormality on pulmonary function testing | Frequent (79-30%)"
    explanation: Orphanet lists abnormality on pulmonary function testing as frequent in ALS.
- name: Dyspnea
  category: Respiratory
  frequency: FREQUENT
  description: Breathlessness resulting from progressive respiratory muscle weakness.
  phenotype_term:
    preferred_term: Dyspnea
    term:
      id: HP:0002094
      label: Dyspnea
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002094 | Dyspnea | Frequent (79-30%)"
    explanation: Orphanet lists dyspnea as frequent in ALS.
- name: Orthopnea
  category: Respiratory
  frequency: OCCASIONAL
  description: Difficulty breathing while lying flat, indicating diaphragmatic weakness.
  phenotype_term:
    preferred_term: Orthopnea
    term:
      id: HP:0012764
      label: Orthopnea
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0012764 | Orthopnea | Occasional (29-5%)"
    explanation: Orphanet lists orthopnea as occasional in ALS.
- name: Skeletal Muscle Atrophy
  category: Neuromuscular
  frequency: FREQUENT
  description: Wasting of skeletal muscles due to denervation following motor neuron loss.
  phenotype_term:
    preferred_term: Skeletal muscle atrophy
    term:
      id: HP:0003202
      label: Skeletal muscle atrophy
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0003202 | Skeletal muscle atrophy | Frequent (79-30%)"
    explanation: Orphanet lists skeletal muscle atrophy as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Lower motor neuron signs include muscle atrophy, weakness, flaccid paralysis, absent reflexes, fasciculations, and fibrillations."
    explanation: Review details muscle atrophy as a key lower motor neuron sign in ALS.
- name: Distal Amyotrophy
  category: Neuromuscular
  frequency: FREQUENT
  description: Wasting of muscles in the hands and feet, often an early finding.
  phenotype_term:
    preferred_term: Distal amyotrophy
    term:
      id: HP:0003693
      label: Distal amyotrophy
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0003693 | Distal amyotrophy | Frequent (79-30%)"
    explanation: Orphanet lists distal amyotrophy as frequent in ALS.
- name: Progressive Distal Muscular Atrophy
  category: Neuromuscular
  frequency: FREQUENT
  description: Progressive wasting of distal muscles over the course of disease.
  phenotype_term:
    preferred_term: Progressive distal muscular atrophy
    term:
      id: HP:0008955
      label: Progressive distal muscular atrophy
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0008955 | Progressive distal muscular atrophy | Frequent (79-30%)"
    explanation: Orphanet lists progressive distal muscular atrophy as frequent in ALS.
- name: Upper Limb Muscle Weakness
  category: Neuromuscular
  frequency: FREQUENT
  description: Weakness of arm and hand muscles, often presenting asymmetrically.
  phenotype_term:
    preferred_term: Upper limb muscle weakness
    term:
      id: HP:0003484
      label: Upper limb muscle weakness
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0003484 | Upper limb muscle weakness | Frequent (79-30%)"
    explanation: Orphanet lists upper limb muscle weakness as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "the majority of the patients present with asymmetric limb weakness (80%) or bulbar dysfunction (20%)."
    explanation: StatPearls review confirms asymmetric limb weakness as the most common presentation.
- name: Lower Limb Muscle Weakness
  category: Neuromuscular
  frequency: FREQUENT
  description: Weakness of leg muscles leading to gait difficulties and falls.
  phenotype_term:
    preferred_term: Lower limb muscle weakness
    term:
      id: HP:0007340
      label: Lower limb muscle weakness
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0007340 | Lower limb muscle weakness | Frequent (79-30%)"
    explanation: Orphanet lists lower limb muscle weakness as frequent in ALS.
- name: Paralysis
  category: Neuromuscular
  frequency: FREQUENT
  description: Progressive loss of ability to move affected muscles due to motor neuron death.
  phenotype_term:
    preferred_term: Paralysis
    term:
      id: HP:0003470
      label: Paralysis
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0003470 | Paralysis | Frequent (79-30%)"
    explanation: Orphanet lists paralysis as frequent in ALS.
- name: Muscle Spasm
  category: Neuromuscular
  frequency: FREQUENT
  description: Painful involuntary muscle contractions, a common and distressing symptom in ALS.
  phenotype_term:
    preferred_term: Muscle spasm
    term:
      id: HP:0003394
      label: Muscle spasm
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0003394 | Muscle spasm | Frequent (79-30%)"
    explanation: Orphanet lists muscle spasm as frequent in ALS.
- name: Tongue Fasciculations
  category: Neurological
  frequency: OCCASIONAL
  diagnostic: true
  description: Involuntary twitching of the tongue, a characteristic finding of bulbar motor neuron involvement.
  phenotype_term:
    preferred_term: Tongue fasciculations
    term:
      id: HP:0001308
      label: Tongue fasciculations
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0001308 | Tongue fasciculations | Occasional (29-5%)"
    explanation: Orphanet lists tongue fasciculations as occasional in ALS.
- name: Tongue Atrophy
  category: Neurological
  frequency: FREQUENT
  description: Wasting of tongue muscles due to hypoglossal motor neuron loss.
  phenotype_term:
    preferred_term: Tongue atrophy
    term:
      id: HP:0012473
      label: Tongue atrophy
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0012473 | Tongue atrophy | Frequent (79-30%)"
    explanation: Orphanet lists tongue atrophy as frequent in ALS.
- name: Foot Dorsiflexor Weakness
  category: Neuromuscular
  frequency: OCCASIONAL
  description: Weakness of muscles that lift the foot, causing foot drop and gait impairment.
  phenotype_term:
    preferred_term: Foot dorsiflexor weakness
    term:
      id: HP:0009027
      label: Foot dorsiflexor weakness
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0009027 | Foot dorsiflexor weakness | Occasional (29-5%)"
    explanation: Orphanet lists foot dorsiflexor weakness as occasional in ALS.
- name: Steppage Gait
  category: Neuromuscular
  frequency: OCCASIONAL
  description: High-stepping gait pattern resulting from foot drop due to lower motor neuron involvement.
  phenotype_term:
    preferred_term: Steppage gait
    term:
      id: HP:0003376
      label: Steppage gait
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0003376 | Steppage gait | Occasional (29-5%)"
    explanation: Orphanet lists steppage gait as occasional in ALS.
- name: Weight Loss
  category: Constitutional
  frequency: FREQUENT
  description: Unintentional weight loss due to dysphagia, hypermetabolism, and muscle wasting. A negative prognostic factor.
  phenotype_term:
    preferred_term: Weight loss
    term:
      id: HP:0001824
      label: Weight loss
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0001824 | Weight loss | Frequent (79-30%)"
    explanation: Orphanet lists weight loss as frequent in ALS.
  - reference: PMID:23466470
    reference_title: "Nutrition management of amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Amyotrophic lateral sclerosis (ALS) is a progressive neurological disease with high risk of malnutrition."
    explanation: Nutrition review confirms ALS carries high risk of malnutrition and weight loss.
- name: Cachexia
  category: Constitutional
  frequency: OCCASIONAL
  description: Severe wasting and weight loss in advanced disease.
  phenotype_term:
    preferred_term: Cachexia
    term:
      id: HP:0004326
      label: Cachexia
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0004326 | Cachexia | Occasional (29-5%)"
    explanation: Orphanet lists cachexia as occasional in ALS.
- name: Fatigue
  category: Constitutional
  frequency: FREQUENT
  description: Pervasive tiredness and reduced energy common across the disease course.
  phenotype_term:
    preferred_term: Fatigue
    term:
      id: HP:0012378
      label: Fatigue
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0012378 | Fatigue | Frequent (79-30%)"
    explanation: Orphanet lists fatigue as frequent in ALS.
  - reference: PMID:23466470
    reference_title: "Nutrition management of amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Symptoms of dysphagia, depression, cognitive impairment, difficulty with self-feeding and meal preparation, hypermetabolism, anxiety, respiratory insufficiency, and fatigue with meals increase the risk of malnutrition."
    explanation: Nutrition review identifies fatigue as a contributing symptom to malnutrition risk in ALS.
- name: Pain
  category: Neurological
  frequency: FREQUENT
  description: Physical pain is common in ALS, often related to muscle cramps, spasticity, immobility, and joint complications.
  phenotype_term:
    preferred_term: Pain
    term:
      id: HP:0012531
      label: Pain
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0012531 | Pain | Frequent (79-30%)"
    explanation: Orphanet lists pain as frequent in ALS.
  - reference: PMID:33661072
    reference_title: "Prevalence of pain in amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    snippet: "Pooled prevalence of pain in ALS across all studies was 60% (95% CI = 50-69%), with a high degree of heterogeneity"
    explanation: Systematic review and meta-analysis establishes pain prevalence of 60% across ALS populations.
- name: Xerostomia
  category: Neurological
  frequency: FREQUENT
  description: Dry mouth, which may paradoxically coexist with drooling due to impaired swallowing.
  phenotype_term:
    preferred_term: Xerostomia
    term:
      id: HP:0000217
      label: Xerostomia
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0000217 | Xerostomia | Frequent (79-30%)"
    explanation: Orphanet lists xerostomia as frequent in ALS.
- name: Emotional Lability
  category: Neuropsychiatric
  frequency: FREQUENT
  description: Pseudobulbar affect characterized by involuntary, exaggerated, or inappropriate episodes of laughing or crying.
  phenotype_term:
    preferred_term: Emotional lability
    term:
      id: HP:0000712
      label: Emotional lability
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0000712 | Emotional lability | Frequent (79-30%)"
    explanation: Orphanet lists emotional lability as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Some patients may also present with Pseudobulbar affect, which is dysregulation of emotional responses exhibited by excessive laughter or crying."
    explanation: StatPearls review describes pseudobulbar affect as dysregulated emotional responses in ALS patients.
- name: Depression
  category: Neuropsychiatric
  frequency: FREQUENT
  description: Depressive symptoms are common in ALS and may reflect both psychological burden and neurobiological changes.
  phenotype_term:
    preferred_term: Depression
    term:
      id: HP:0000716
      label: Depression
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0000716 | Depression | Frequent (79-30%)"
    explanation: Orphanet lists depression as frequent in ALS.
  - reference: PMID:23466470
    reference_title: "Nutrition management of amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Symptoms of dysphagia, depression, cognitive impairment, difficulty with self-feeding and meal preparation, hypermetabolism, anxiety, respiratory insufficiency, and fatigue with meals increase the risk of malnutrition."
    explanation: Nutrition review identifies depression as a contributing symptom in ALS.
- name: Anxiety
  category: Neuropsychiatric
  frequency: FREQUENT
  description: Anxiety symptoms commonly co-occur with ALS.
  phenotype_term:
    preferred_term: Anxiety
    term:
      id: HP:0000739
      label: Anxiety
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0000739 | Anxiety | Frequent (79-30%)"
    explanation: Orphanet lists anxiety as frequent in ALS.
  - reference: PMID:23466470
    reference_title: "Nutrition management of amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Symptoms of dysphagia, depression, cognitive impairment, difficulty with self-feeding and meal preparation, hypermetabolism, anxiety, respiratory insufficiency, and fatigue with meals increase the risk of malnutrition."
    explanation: Nutrition review lists anxiety among symptoms contributing to malnutrition in ALS.
- name: Atypical Behavior
  category: Neuropsychiatric
  frequency: FREQUENT
  description: Behavioral changes including apathy, disinhibition, and loss of empathy, part of the ALS-FTD continuum.
  phenotype_term:
    preferred_term: Atypical behavior
    term:
      id: HP:0000708
      label: Atypical behavior
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0000708 | Atypical behavior | Frequent (79-30%)"
    explanation: Orphanet lists atypical behavior as frequent in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Patients can also display changes in behavior due to frontotemporal dysfunction, and about 15% of patients develop frontotemporal dementia."
    explanation: StatPearls review confirms behavioral changes from frontotemporal dysfunction in ALS patients.
- name: Cognitive Impairment
  category: Neuropsychiatric
  frequency: FREQUENT
  description: Cognitive deficits, particularly in executive function, occur in up to 50% of ALS patients, part of the ALS-FTD continuum.
  phenotype_term:
    preferred_term: Cognitive impairment
    term:
      id: HP:0100543
      label: Cognitive impairment
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0100543 | Cognitive impairment | Frequent (79-30%)"
    explanation: Orphanet lists cognitive impairment as frequent in ALS.
  - reference: PMID:22305801
    reference_title: "Cognitive and clinical characteristics of patients with amyotrophic lateral sclerosis carrying a C9orf72 repeat expansion: a population-based cohort study."
    supports: SUPPORT
    snippet: "Cognitive impairment occurs in up to 50% of cases, and one in seven patients develops frank frontotemporal dementia (FTD)."
    explanation: Population-based study reports cognitive impairment in up to 50% of ALS cases.
- name: Frontotemporal Dementia
  category: Neuropsychiatric
  frequency: OCCASIONAL
  description: Co-morbid frontotemporal dementia occurs in approximately 15% of ALS patients, representing the severe end of the ALS-FTD continuum.
  phenotype_term:
    preferred_term: Frontotemporal dementia
    term:
      id: HP:0002145
      label: Frontotemporal dementia
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002145 | Frontotemporal dementia | Occasional (29-5%)"
    explanation: Orphanet lists frontotemporal dementia as occasional in ALS.
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "about 15% of patients develop frontotemporal dementia."
    explanation: StatPearls review reports approximately 15% of ALS patients develop frontotemporal dementia.
  - reference: PMID:38802173
    reference_title: "Amyotrophic lateral sclerosis; clinical features, differential diagnosis and pathology."
    supports: SUPPORT
    snippet: "ALS forms a clinical continuum with frontotemporal dementia (FTD), in which there are progressive language deficits or behavioral changes."
    explanation: Review describes ALS-FTD clinical continuum with overlapping genetics and pathology.
- name: Language Impairment
  category: Neuropsychiatric
  frequency: OCCASIONAL
  description: Language deficits as part of the frontotemporal dysfunction spectrum in ALS.
  phenotype_term:
    preferred_term: Language impairment
    term:
      id: HP:0002463
      label: Language impairment
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002463 | Language impairment | Occasional (29-5%)"
    explanation: Orphanet lists language impairment as occasional in ALS.
  - reference: PMID:38802173
    reference_title: "Amyotrophic lateral sclerosis; clinical features, differential diagnosis and pathology."
    supports: SUPPORT
    snippet: "ALS forms a clinical continuum with frontotemporal dementia (FTD), in which there are progressive language deficits or behavioral changes."
    explanation: ALS clinical features review describes progressive language deficits within the ALS-FTD spectrum.
- name: Sleep Disturbance
  category: Neurological
  frequency: OCCASIONAL
  description: Sleep disturbances including nocturnal hypoventilation, sleep fragmentation, and excessive daytime sleepiness.
  phenotype_term:
    preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002360 | Sleep abnormality | Occasional (29-5%)"
    explanation: Orphanet lists sleep disturbance as occasional in ALS.
- name: Spastic Paraparesis
  category: Neurological
  frequency: OCCASIONAL
  description: Stiffness and weakness of both lower limbs due to upper motor neuron involvement.
  phenotype_term:
    preferred_term: Spastic paraparesis
    term:
      id: HP:0002313
      label: Spastic paraparesis
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0002313 | Spastic paraparesis | Occasional (29-5%)"
    explanation: Orphanet lists spastic paraparesis as occasional in ALS.
- name: Jaw Hyperreflexia
  category: Neurological
  frequency: OCCASIONAL
  diagnostic: true
  description: Exaggerated jaw jerk reflex indicating upper motor neuron involvement in the brainstem.
  phenotype_term:
    preferred_term: Jaw hyperreflexia
    term:
      id: HP:0033683
      label: Jaw hyperreflexia
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0033683 | Jaw hyperreflexia | Occasional (29-5%)"
    explanation: Orphanet lists jaw hyperreflexia as occasional in ALS.
- name: Laryngospasm
  category: Neurological
  frequency: VERY_RARE
  description: Sudden involuntary closure of the vocal cords, causing brief episodes of breathing difficulty.
  phenotype_term:
    preferred_term: Laryngospasm
    term:
      id: HP:0025425
      label: Laryngospasm
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "HP:0025425 | Laryngospasm | Very rare (<4-1%)"
    explanation: Orphanet lists laryngospasm as very rare in ALS.
biochemical:
- name: Neurofilament Light Chain (NfL)
  presence: Elevated
  context: CSF and serum biomarker of axonal injury, elevated in ALS with prognostic value
  notes: Used for prognosis and for monitoring therapeutic response in clinical trials
  evidence:
  - reference: PMID:32385188
    reference_title: "Validation of serum neurofilaments as prognostic and potential pharmacodynamic biomarkers for ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Baseline serum NfL concentration, but not pNfH, predicted the future Revised ALS Functional Rating Scale (ALSFRS-R) slope and survival."
    explanation: >-
      Prospective multicentre cohort establishing serum NfL as a prognostic
      marker of functional decline and survival in ALS.
  - reference: PMID:32385188
    reference_title: "Validation of serum neurofilaments as prognostic and potential pharmacodynamic biomarkers for ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Serum NfL may be considered a clinically validated prognostic biomarker for ALS. Serum NfL (and perhaps pNfH), quantified using the Simoa assay, has potential utility as a pharmacodynamic biomarker of treatment effect."
    explanation: >-
      The authors' own conclusion, and the basis for recording NfL as a marker
      used for prognosis and for monitoring therapeutic response in trials.
  - reference: PMID:36129998
    reference_title: "Trial of Antisense Oligonucleotide Tofersen for SOD1 ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Tofersen led to greater reductions in concentrations of SOD1 in CSF and of neurofilament light chains in plasma than placebo."
    explanation: >-
      The VALOR phase 3 trial shows plasma neurofilament light chain falls with
      SOD1-lowering therapy, validating NfL as a pharmacodynamic biomarker of
      axonal injury that tracks treatment response in ALS.
- name: Phosphorylated Neurofilament Heavy Chain (pNfH)
  presence: Elevated
  context: CSF and serum biomarker of axonal injury
- name: Skeletal Myocyte Plasma Proteomic Age Gap
  biomarker_term:
    preferred_term: skeletal myocyte plasma proteomic aging clock (age gap)
    term:
      id: NCIT:C97139
      label: Proteomic Profile
  presence: Elevated
  context: >-
    Blood-based cell-type-specific aging clock. Plasma proteins are mapped to
    their putative cell of origin using Human Protein Atlas single-cell
    transcriptomic data, and a machine-learning model estimates skeletal myocyte
    biological age; the age gap is the difference between that estimate and
    chronological age. "Extreme" agers are those in the upper tail of the age-gap
    distribution and "youthful" agers the lower tail.
  cell_types:
  - preferred_term: Skeletal myocyte
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  notes: >-
    Skeletal myocyte aging was the single strongest disease/cell-type pairing
    across the whole study, and its prognostic signal for incident ALS persisted
    when analysis was restricted to cases diagnosed more than three years after
    the blood draw - the argument against the association being pure reverse
    causation from prevalent, undiagnosed disease. Cardiomyocyte aging showed a
    weaker parallel signal. This is an observational prognostic association; it
    does not establish that myocyte aging initiates motor neuron degeneration,
    and the likeliest reading is that the plasma signature reports early
    denervation-associated muscle change.
  evidence:
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Individuals with extremely aged compared to youthful skeletal myocytes exhibited a 12.7-fold higher risk of developing amyotrophic lateral sclerosis.
    explanation: >-
      Quantifies the prognostic association between the skeletal myocyte plasma
      proteomic age gap and incident ALS over 15 years of UK Biobank follow-up
      (reported as HR 12.74 in the results text).
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The strongest association among all disease-cell type pairs was between ALS and skeletal myocyte aging
    explanation: >-
      Establishes that this is the most prominent cell-type/disease association
      in the study, not one signal among many comparable ones.
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 53 of 57 (93.0%) skeletal myocyte extreme agers had an ALS diagnosis.
    explanation: >-
      Cross-sectional case/control concentration of extreme skeletal myocyte
      agers among ALS patients in the GNPC ALS cohort (n = 355; 245 patients,
      110 controls), independent of the UK Biobank incident analysis.
  readouts:
  - target: Motor Neuron Degeneration
    relationship: PREDICTS
    direction: POSITIVE
    endpoint_context: PROGNOSTIC
    interpretation: >-
      An elevated skeletal myocyte age gap predicts incident ALS years before
      diagnosis and is read here as a peripheral plasma correlate of the
      motor-neuron-degeneration axis and its downstream denervation, rather than
      as an independent muscle-intrinsic disease process.
    evidence:
    - reference: PMID:42297981
      reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: extreme skeletal myocyte aging demonstrated pronounced prognostic power for incident ALS over 15 years of follow-up in the UKB cohort, even for cases diagnosed more than 3 years after baseline assessment, suggesting potential for presymptomatic detection
      explanation: >-
        Supports a presymptomatic prognostic readout and addresses the reverse-causation
        objection by restricting to cases diagnosed well after the blood draw.
- name: Cardiomyocyte Plasma Proteomic Age Gap
  biomarker_term:
    preferred_term: cardiomyocyte plasma proteomic aging clock (age gap)
    term:
      id: NCIT:C97139
      label: Proteomic Profile
  presence: Elevated
  context: >-
    Blood-based cell-type-specific aging clock (see Skeletal Myocyte Plasma
    Proteomic Age Gap for the derivation). Curated as a cross-sectional correlate
    of prevalent ALS, deliberately NOT as a prognostic marker for incident
    disease.
  cell_types:
  - preferred_term: Cardiomyocyte
    term:
      id: CL:0000746
      label: cardiac muscle cell
  specificity: >-
    Weaker and less specific than the skeletal myocyte signature it parallels.
    Cardiomyocyte-assigned FABP3 is one of the proteins the authors name as
    potentially released more broadly than its assigned cell type, so part of
    this signal may not be cardiomyocyte-derived at all.
  notes: >-
    The two arms of this marker must not be quoted as one finding. Cross-sectionally,
    cardiomyocyte aging was accelerated in prevalent ALS in the GNPC cohort
    (r = 0.33, adjusted P = 4.08e-9), alongside the stronger skeletal myocyte
    signal (r = 0.43). Prognostically it did NOT reach significance: the overall
    log-rank test for cumulative ALS incidence across youthful, normal and
    extreme ager groups in UK Biobank gave P = 0.0562 for cardiomyocyte aging,
    against P < 0.0001 for skeletal myocyte aging. The paper's narrative describes
    "similar risk stratification" for the two cell types, which reads more
    favourably than its own log-rank result; curated here on the statistic rather
    than the narrative. Whether this reflects genuine cardiac involvement in ALS,
    shared molecular pathways across cardiac and skeletal muscle, or protein
    misassignment between the two muscle compartments is unresolved.
  evidence:
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: along with skeletal myocytes, we observed that cardiomyocytes showed accelerated aging in patients with ALS
    explanation: >-
      Establishes the cross-sectional association with prevalent ALS in the GNPC
      cohort, which is the arm this marker is curated on.
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: patients with ALS exhibited pronounced acceleration of skeletal myocyte aging and cardiomyocyte aging across chronological age span
    explanation: >-
      LOWESS analysis showing the acceleration is present across the chronological
      age range rather than confined to older patients.
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: NO_EVIDENCE
    evidence_source: HUMAN_CLINICAL
    snippet: We observed similar risk stratification for cardiomyocyte aging and incident ALS
    explanation: >-
      This sentence concerns incident ALS, which this marker deliberately does not
      claim (see context), so it does not bear on the cross-sectional claim. It
      also asserts prognostic parity with the skeletal myocyte clock that the
      paper's own log-rank test does not show (P = 0.0562 for cardiomyocyte
      aging). Kept so the gap between the paper's narrative and its statistic is
      visible to the next curator rather than silently inherited.
  - reference: PMID:42297981
    reference_title: "Plasma proteomic signatures of cellular aging predict human disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: cardiomyocyte-assigned FABP3 and microglia-assigned HAVCR1 may be produced or released more broadly under specific circumstances
    explanation: >-
      The authors name a cardiomyocyte-assigned protein as one whose cellular
      origin is not exclusive, which is a specific caveat on this marker rather
      than a generic one.
genetic:
- name: C9orf72 Repeat Expansion
  gene_term:
    preferred_term: C9orf72
    term:
      id: hgnc:28337
      label: C9orf72
  association: Causative
  relationship_type: CAUSATIVE
  subtype: FTDALS1
  notes: >-
    The commonest genetic cause of ALS in European-ancestry series, and a GGGGCC
    hexanucleotide repeat expansion rather than a coding lesion. The reported
    familial share depends on the series and the population: the discovery paper
    gives 23.5% of familial ALS, a later cross-sectional study ~40.0%, and a
    meta-analysis of 111 studies 33.7% in European populations against 2.3% in
    Asian populations, where C9orf72 expansions are comparatively rare. The
    sporadic share is around 5-10%.
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "C9ORF72 | C9orf72-SMCR8 complex subunit | hgnc:28337 | Disease-causing germline mutation(s) in"
    explanation: Orphanet lists C9ORF72 as harboring disease-causing germline mutations in ALS.
  - reference: PMID:21944778
    reference_title: "Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS."
    supports: SUPPORT
    snippet: "Analysis of extended clinical series found the C9ORF72 repeat expansion to be the most common genetic abnormality in both familial FTD (11.7%) and familial ALS (23.5%)"
    explanation: Original discovery paper establishing C9orf72 as the most common genetic cause of familial ALS.
  - reference: PMID:22406228
    reference_title: "Frequency of the C9orf72 hexanucleotide repeat expansion in patients with amyotrophic lateral sclerosis and frontotemporal dementia: a cross-sectional study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This genetic lesion accounted for a large proportion (∼40·0%) of familial cases of ALS and FTD."
    explanation: Cross-sectional study's headline conclusion supports the ~40% familial figure cited in this entry's notes.
  - reference: PMID:22406228
    reference_title: "Frequency of the C9orf72 hexanucleotide repeat expansion in patients with amyotrophic lateral sclerosis and frontotemporal dementia: a cross-sectional study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In patients with sporadic ALS, we identified the repeat expansion in 236 (7·0%) of 3377 white individuals from the USA, Europe, and Australia"
    explanation: Same study supports the 5-10% sporadic-ALS frequency cited in this entry's notes (7.0% in the largest white cohort).
  - reference: PMID:28057713
    reference_title: "Genetic epidemiology of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In European populations, the most common mutations were the C9orf72 repeat expansions (FALS 33.7%, SALS 5.1%), followed by SOD1 (FALS 14.8%, SALS 1.2%), TARDBP (FALS 4.2%, SALS 0.8%) and FUS mutations (FALS 2.8%, SALS 0.3%), while in Asian populations the most common mutations were SOD1 mutations (FALS 30.0%, SALS 1.5%), followed by FUS (FALS 6.4%, SALS 0.9%), C9orf72 (FALS 2.3%, SALS 0.3%) and TARDBP (FALS 1.5%, SALS 0.2%) mutations."
    explanation: >
      Meta-analysis of 111 studies giving population-stratified mutation
      frequencies; the source for the population dependence recorded above.
- name: SOD1 Mutations
  gene_term:
    preferred_term: SOD1
    term:
      id: hgnc:11179
      label: SOD1
  association: Causative
  relationship_type: CAUSATIVE
  notes: >-
    First identified ALS gene. SOD1-associated ALS is curated separately as
    `Amyotrophic_Lateral_Sclerosis_Type_1` (ALS1, MONDO:0007103), which is where the
    SOD1-specific mechanism, allelic subtypes and tofersen evidence live. That entry is
    split out on pathological grounds rather than genetic ones: SOD1-mutant cases carry
    ubiquitin-positive but TDP-43-negative inclusions, so they sit outside the TDP-43
    proteinopathy this entry models. The SOD1 share of familial ALS is strongly
    population-dependent: a meta-analysis of 111 studies put it at 14.8% of
    familial ALS in European populations and 30.0% in Asian populations, where
    SOD1 is the commonest ALS gene of all. See also the case_fractions block in
    that entry.
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "SOD1 | superoxide dismutase 1 | hgnc:11179 | Disease-causing germline mutation(s) in"
    explanation: Orphanet lists SOD1 as harboring disease-causing germline mutations in ALS.
  - reference: PMID:8446170
    reference_title: "Mutations in Cu/Zn superoxide dismutase gene are associated with familial amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "We identified 11 different SOD1 missense mutations in 13 different FALS families."
    explanation: Original discovery paper identifying SOD1 mutations as a cause of familial ALS.
  - reference: PMID:28057713
    reference_title: "Genetic epidemiology of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In European populations, the most common mutations were the C9orf72 repeat expansions (FALS 33.7%, SALS 5.1%), followed by SOD1 (FALS 14.8%, SALS 1.2%), TARDBP (FALS 4.2%, SALS 0.8%) and FUS mutations (FALS 2.8%, SALS 0.3%), while in Asian populations the most common mutations were SOD1 mutations (FALS 30.0%, SALS 1.5%), followed by FUS (FALS 6.4%, SALS 0.9%), C9orf72 (FALS 2.3%, SALS 0.3%) and TARDBP (FALS 1.5%, SALS 0.2%) mutations."
    explanation: >
      Meta-analysis of 111 studies giving population-stratified mutation
      frequencies for the four commonest ALS genes; this is the source for the
      per-gene familial-ALS shares quoted in this record.
- name: TARDBP Mutations
  gene_term:
    preferred_term: TARDBP
    term:
      id: hgnc:11571
      label: TARDBP
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS10
  notes: >-
    Encodes the TDP-43 protein. A meta-analysis of 111 studies put TARDBP
    mutations at 4.2% of familial ALS in European populations and 1.5% in Asian
    populations.
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "TARDBP | TAR DNA binding protein | hgnc:11571 | Disease-causing germline mutation(s) in"
    explanation: Orphanet lists TARDBP as harboring disease-causing germline mutations in ALS.
  - reference: PMID:35805149
    reference_title: "Gene Therapy in Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    snippet: "Mutations in C9orf72, SOD1, TAR DNA binding protein 43 (TARDBP), and fused in sarcoma (FUS) genes are the four most common ones."
    explanation: Gene therapy review highlights TARDBP among the most common ALS genes targeted by therapeutic strategies.
  - reference: PMID:28057713
    reference_title: "Genetic epidemiology of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In European populations, the most common mutations were the C9orf72 repeat expansions (FALS 33.7%, SALS 5.1%), followed by SOD1 (FALS 14.8%, SALS 1.2%), TARDBP (FALS 4.2%, SALS 0.8%) and FUS mutations (FALS 2.8%, SALS 0.3%), while in Asian populations the most common mutations were SOD1 mutations (FALS 30.0%, SALS 1.5%), followed by FUS (FALS 6.4%, SALS 0.9%), C9orf72 (FALS 2.3%, SALS 0.3%) and TARDBP (FALS 1.5%, SALS 0.2%) mutations."
    explanation: >
      Meta-analysis of 111 studies giving population-stratified mutation
      frequencies for the four commonest ALS genes; this is the source for the
      per-gene familial-ALS shares quoted in this record.
- name: FUS Mutations
  gene_term:
    preferred_term: FUS
    term:
      id: hgnc:4010
      label: FUS
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS6
  notes: >-
    RNA-binding protein. A meta-analysis of 111 studies put FUS mutations at 2.8%
    of familial ALS in European populations and 6.4% in Asian populations.
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "FUS | FUS RNA binding protein | hgnc:4010 | Disease-causing germline mutation(s) in"
    explanation: Orphanet lists FUS as harboring disease-causing germline mutations in ALS.
  - reference: PMID:35805149
    reference_title: "Gene Therapy in Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    snippet: "Mutations in C9orf72, SOD1, TAR DNA binding protein 43 (TARDBP), and fused in sarcoma (FUS) genes are the four most common ones."
    explanation: Review notes FUS among the four most common ALS genes and discusses gene-targeted therapies.
  - reference: PMID:28057713
    reference_title: "Genetic epidemiology of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In European populations, the most common mutations were the C9orf72 repeat expansions (FALS 33.7%, SALS 5.1%), followed by SOD1 (FALS 14.8%, SALS 1.2%), TARDBP (FALS 4.2%, SALS 0.8%) and FUS mutations (FALS 2.8%, SALS 0.3%), while in Asian populations the most common mutations were SOD1 mutations (FALS 30.0%, SALS 1.5%), followed by FUS (FALS 6.4%, SALS 0.9%), C9orf72 (FALS 2.3%, SALS 0.3%) and TARDBP (FALS 1.5%, SALS 0.2%) mutations."
    explanation: >
      Meta-analysis of 111 studies giving population-stratified mutation
      frequencies for the four commonest ALS genes; this is the source for the
      per-gene familial-ALS shares quoted in this record.
- name: NEK1 Variants
  gene_term:
    preferred_term: NEK1
    term:
      id: hgnc:7744
      label: NEK1
  association: Susceptibility
  relationship_type: SUSCEPTIBILITY
  notes: Risk variants found in nearly 3% of ALS cases
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "NEK1 | NIMA related kinase 1 | hgnc:7744 | Major susceptibility factor in"
    explanation: Orphanet lists NEK1 as a major susceptibility factor in ALS.
  - reference: PMID:27455347
    reference_title: "NEK1 variants confer susceptibility to amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "In total, we observed NEK1 risk variants in nearly 3% of ALS cases. NEK1 has been linked to several cellular functions, including cilia formation, DNA-damage response, microtubule stability, neuronal morphology and axonal polarity."
    explanation: Large-scale genetic study identifying NEK1 variants as risk factors for ALS.
- name: ATXN2 Intermediate-Length Repeat Expansion
  gene_term:
    preferred_term: ATXN2
    term:
      id: hgnc:10555
      label: ATXN2
  association: Susceptibility
  relationship_type: SUSCEPTIBILITY
  notes: >-
    Intermediate-length polyglutamine (polyQ) expansions of 27-33 repeats in ATXN2 are a
    relatively common ALS susceptibility factor. ATXN2 is a potent modifier of TDP-43
    toxicity, linking this risk allele to the core TDP-43 proteinopathy axis; ATXN2
    lowering (e.g., antisense oligonucleotides) is under therapeutic investigation.
  evidence:
  - reference: PMID:20740007
    reference_title: "Ataxin-2 intermediate-length polyglutamine expansions are associated with increased risk for ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We found that intermediate-length polyQ expansions (27-33 glutamines) in ATXN2 were significantly associated with ALS. These data establish ATXN2 as a relatively common ALS susceptibility gene."
    explanation: >-
      Landmark study analyzing the ATXN2 polyQ repeat in 915 ALS patients establishes
      intermediate-length expansions as a common ALS susceptibility factor and identifies
      ATXN2 as a modifier of TDP-43 toxicity.
- name: ARHGEF28
  gene_term:
    preferred_term: ARHGEF28
    term:
      id: hgnc:30322
      label: ARHGEF28
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_ac27cecc-9749-4c69-88fa-fe83b2d49568-2024-03-28T190000.000Z
    reference_title: "ARHGEF28 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ARHGEF28 | HGNC:30322 | amyotrophic lateral sclerosis | MONDO:0004976 | SD | Limited"
    explanation: ClinGen classifies the ARHGEF28-amyotrophic lateral sclerosis gene-disease relationship as limited with semidominant inheritance.
- name: ARPP21
  gene_term:
    preferred_term: ARPP21
    term:
      id: hgnc:16968
      label: ARPP21
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_02d4089a-94dd-42b6-ab09-dc258db00ae9-2025-01-14T200000.000Z
    reference_title: "ARPP21 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ARPP21 | HGNC:16968 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the ARPP21-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: CAV1
  gene_term:
    preferred_term: CAV1
    term:
      id: hgnc:1527
      label: CAV1
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_cab41529-d295-466c-8821-75a16bb12c38-2023-12-21T170000.000Z
    reference_title: "CAV1 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "CAV1 | HGNC:1527 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the CAV1-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: CAV2
  gene_term:
    preferred_term: CAV2
    term:
      id: hgnc:1528
      label: CAV2
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_38faae4c-13ae-4c28-bea4-43e3ad15e178-2023-12-21T170000.000Z
    reference_title: "CAV2 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "CAV2 | HGNC:1528 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the CAV2-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: CFAP410
  gene_term:
    preferred_term: CFAP410
    term:
      id: hgnc:1260
      label: CFAP410
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_bde7edf1-ccfa-443e-a917-cf3d2dd9cba6-2023-12-12T180000.000Z
    reference_title: "CFAP410 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "CFAP410 | HGNC:1260 | amyotrophic lateral sclerosis | MONDO:0004976 | SD | Limited"
    explanation: ClinGen classifies the CFAP410-amyotrophic lateral sclerosis gene-disease relationship as limited with semidominant inheritance.
- name: DCTN1
  gene_term:
    preferred_term: DCTN1
    term:
      id: hgnc:2711
      label: DCTN1
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_5cd19f2c-2499-417f-94c8-2bd4bedf34ef-2023-08-04T160000.000Z
    reference_title: "DCTN1 / amyotrophic lateral sclerosis (Moderate)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "DCTN1 | HGNC:2711 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Moderate"
    explanation: ClinGen classifies the DCTN1-amyotrophic lateral sclerosis gene-disease relationship as moderate with autosomal dominant inheritance.
- name: DNAJC7
  gene_term:
    preferred_term: DNAJC7
    term:
      id: hgnc:12392
      label: DNAJC7
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_e2a12a19-b37a-4654-87fa-3a921c202c87-2022-10-27T160000.000Z
    reference_title: "DNAJC7 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "DNAJC7 | HGNC:12392 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the DNAJC7-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: GLE1
  gene_term:
    preferred_term: GLE1
    term:
      id: hgnc:4315
      label: GLE1
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_0284b3cd-38af-4309-8ce4-054a0379e693-2023-10-10T160000.000Z
    reference_title: "GLE1 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "GLE1 | HGNC:4315 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the GLE1-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: GLT8D1
  gene_term:
    preferred_term: GLT8D1
    term:
      id: hgnc:24870
      label: GLT8D1
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_a2c4f919-ccb5-4d9f-a604-5ed19e19057e-2025-01-14T200000.000Z
    reference_title: "GLT8D1 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "GLT8D1 | HGNC:24870 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the GLT8D1-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: LGALSL
  gene_term:
    preferred_term: LGALSL
    term:
      id: hgnc:25012
      label: LGALSL
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_5a2db59f-5293-4e5d-ae34-5a38d8c6ebdf-2023-02-14T170000.000Z
    reference_title: "LGALSL / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "LGALSL | HGNC:25012 | amyotrophic lateral sclerosis | MONDO:0004976 | UD | Limited"
    explanation: ClinGen classifies the LGALSL-amyotrophic lateral sclerosis gene-disease relationship as limited with undetermined inheritance.
- name: NEFH
  gene_term:
    preferred_term: NEFH
    term:
      id: hgnc:7737
      label: NEFH
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_6c71deac-6b11-4947-8834-8391d516a9c9-2023-03-23T160000.000Z
    reference_title: "NEFH / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "NEFH | HGNC:7737 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the NEFH-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: NUP50
  gene_term:
    preferred_term: NUP50
    term:
      id: hgnc:8065
      label: NUP50
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_0ce3418e-c7e5-452b-9db6-661571331822-2024-06-27T160000.000Z
    reference_title: "NUP50 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "NUP50 | HGNC:8065 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the NUP50-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: PRPH
  gene_term:
    preferred_term: PRPH
    term:
      id: hgnc:9461
      label: PRPH
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_3d11b04d-508a-4f91-9d9a-b5016fd0b940-2022-12-13T170000.000Z
    reference_title: "PRPH / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "PRPH | HGNC:9461 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the PRPH-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: SPTLC2
  gene_term:
    preferred_term: SPTLC2
    term:
      id: hgnc:11278
      label: SPTLC2
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_402cf65d-02f1-4cc1-a45e-b3bd3ad48b86-2024-06-26T160000.000Z
    reference_title: "SPTLC2 / amyotrophic lateral sclerosis (Strong)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "SPTLC2 | HGNC:11278 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Strong"
    explanation: ClinGen classifies the SPTLC2-amyotrophic lateral sclerosis gene-disease relationship as strong with autosomal dominant inheritance.
- name: SS18L1
  gene_term:
    preferred_term: SS18L1
    term:
      id: hgnc:15592
      label: SS18L1
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_6e148a06-50fc-45f3-90ea-023dc8687577-2023-05-25T160000.000Z
    reference_title: "SS18L1 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "SS18L1 | HGNC:15592 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the SS18L1-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: TAF15
  gene_term:
    preferred_term: TAF15
    term:
      id: hgnc:11547
      label: TAF15
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_605446ae-fd1f-4451-bd49-643c24cd652e-2021-11-03T020945.214Z
    reference_title: "TAF15 / amyotrophic lateral sclerosis (Limited)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "TAF15 | HGNC:11547 | amyotrophic lateral sclerosis | MONDO:0004976 | AD | Limited"
    explanation: ClinGen classifies the TAF15-amyotrophic lateral sclerosis gene-disease relationship as limited with autosomal dominant inheritance.
- name: VAPB
  gene_term:
    preferred_term: VAPB
    term:
      id: hgnc:12649
      label: VAPB
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS8
  notes: >
    Founder missense allele shared across kindreds that could not all be linked;
    carriers present variably as atypical ALS8, late-onset spinal muscular
    atrophy, or typical rapidly progressive ALS.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "VAPB | VAMP associated protein B and C | hgnc:12649 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: ANG
  gene_term:
    preferred_term: ANG
    term:
      id: hgnc:483
      label: ANG
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS9
  notes: >
    Angiogenic ribonuclease expressed in motor neurons as well as endothelium.
    ALS-associated alleles are complete loss-of-function, losing ribonuclease
    activity, nuclear translocation, or both.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ANG | angiogenin | hgnc:483 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: FIG4
  gene_term:
    preferred_term: FIG4
    term:
      id: hgnc:16873
      label: FIG4
  association: Risk factor
  relationship_type: RISK_FACTOR
  subtype: ALS11
  notes: >
    Graded RISK_FACTOR rather than CAUSATIVE on the primary report's own framing:
    heterozygosity for a deleterious FIG4 allele is described there as a risk
    factor for ALS and PLS. Orphanet instead lists FIG4 under disease-causing
    germline mutations, and MONDO numbers the concept as a familial ALS type;
    the divergence is recorded rather than resolved. Biallelic FIG4 loss causes
    the recessive neuropathy CMT4J.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "FIG4 | FIG4 phosphoinositide 5-phosphatase | hgnc:16873 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: OPTN
  gene_term:
    preferred_term: OPTN
    term:
      id: hgnc:17142
      label: OPTN
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS12
  notes: >
    Optineurin, an autophagy receptor and NF-kappaB regulator; reported in both
    homozygous loss-of-function and heterozygous ubiquitin-binding-domain
    missense forms. Already wired to the Impaired Autophagy pathophysiology node.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "OPTN | optineurin | hgnc:17142 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: UBQLN2
  gene_term:
    preferred_term: UBQLN2
    term:
      id: hgnc:12509
      label: UBQLN2
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS15
  notes: >
    Ubiquilin 2 shuttles ubiquitinated substrates to the proteasome; mutations
    cause X-linked dominant juvenile and adult-onset ALS and ALS with dementia.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "UBQLN2 | ubiquilin 2 | hgnc:12509 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: PFN1
  gene_term:
    preferred_term: PFN1
    term:
      id: hgnc:8881
      label: PFN1
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS18
  notes: >
    Profilin 1 converts monomeric to filamentous actin; mutant protein forms
    ubiquitinated insoluble aggregates that often contain TDP-43. Already wired
    to the Axonal Transport Dysfunction pathophysiology node.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "PFN1 | profilin 1 | hgnc:8881 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: ERBB4
  gene_term:
    preferred_term: ERBB4
    term:
      id: hgnc:3432
      label: ERBB4
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS19
  notes: >
    Receptor tyrosine kinase for neuregulin-1; ALS-associated mutations reduce
    ErbB4 autophosphorylation on NRG-1 stimulation.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ERBB4 | erb-b2 receptor tyrosine kinase 4 | hgnc:3432 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: HNRNPA1
  gene_term:
    preferred_term: HNRNPA1
    term:
      id: hgnc:5031
      label: HNRNPA1
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS20
  notes: >
    Prion-like-domain mutations strengthen a steric zipper motif and drive
    self-seeding fibril formation; the same lesion class in hnRNPA1 and its
    paralogue hnRNPA2B1 produces multisystem proteinopathy, of which ALS is one
    presentation.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "HNRNPA1 | heterogeneous nuclear ribonucleoprotein A1 | hgnc:5031 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: MATR3
  gene_term:
    preferred_term: MATR3
    term:
      id: hgnc:6912
      label: MATR3
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS21
  notes: >
    RNA- and DNA-binding protein that interacts with TDP-43; MATR3 pathology is
    present in ALS spinal cords with and without MATR3 mutations.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "MATR3 | matrin 3 | hgnc:6912 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: ANXA11
  gene_term:
    preferred_term: ANXA11
    term:
      id: hgnc:535
      label: ANXA11
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS23
  notes: >
    Vesicular trafficking protein; the recurrent p.D40G allele was absent from
    70,000 control exomes and carriers shared a founder haplotype.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ANXA11 | annexin A11 | hgnc:535 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: TBK1
  gene_term:
    preferred_term: TBK1
    term:
      id: hgnc:11584
      label: TBK1
  association: Causative
  relationship_type: CAUSATIVE
  subtype: FTDALS4
  notes: >
    TANK-binding kinase 1 acts with optineurin in autophagy. Graded CAUSATIVE on
    the exome study that reported haploinsufficiency as the mechanism in familial
    pedigrees; Orphanet instead files TBK1 as a major susceptibility factor,
    and the same study found no enrichment in sporadic ALS. Already wired to the
    Impaired Autophagy pathophysiology node.
  evidence:
  - reference: PMID:25803835
    reference_title: "Haploinsufficiency of TBK1 causes familial ALS and fronto-temporal dementia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Gene-based rare variant analysis identified an exome-wide significant enrichment of eight loss-of-function (LoF) mutations in TBK1 (encoding TANK-binding kinase 1) in 13 fALS pedigrees."
    explanation: >-
      The familial exome result on which the CAUSATIVE grading rests.
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "TBK1 | TANK binding kinase 1 | hgnc:11584 | Major susceptibility factor in"
    explanation: >-
      Orphanet records a TBK1-ALS association, which supports the gene-disease
      link but files it as a major susceptibility factor rather than as a cause;
      it does not by itself support the CAUSATIVE grading (see notes).
- name: CCNF
  gene_term:
    preferred_term: CCNF
    term:
      id: hgnc:1591
      label: CCNF
  association: Causative
  relationship_type: CAUSATIVE
  subtype: FTDALS5
  notes: >
    Cyclin F is the substrate-recognition subunit of an SCF E3 ubiquitin-ligase
    complex; mutant cyclin F causes abnormal ubiquitination and accumulation of
    ubiquitinated proteins including TDP-43.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "CCNF | cyclin F | hgnc:1591 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: VCP
  gene_term:
    preferred_term: VCP
    term:
      id: hgnc:12666
      label: VCP
  association: Causative
  relationship_type: CAUSATIVE
  subtype: FTDALS6
  notes: >
    VCP/p97 is required for maturation of ubiquitin-containing autophagosomes.
    The same gene causes inclusion body myopathy with Paget disease of bone and
    frontotemporal dementia, curated separately; the ALS presentation is
    numbered FTDALS6. Already wired to the Impaired Autophagy pathophysiology node.
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "VCP | valosin containing protein | hgnc:12666 | Disease-causing germline mutation(s) in"
    explanation: Orphanet's gene table for amyotrophic lateral sclerosis records this gene-disease association.
- name: TIA1
  gene_term:
    preferred_term: TIA1
    term:
      id: hgnc:11802
      label: TIA1
  association: Disputed
  relationship_type: DISPUTED
  subtype: ALS26
  notes: >
    TIA1 low-complexity-domain mutations were reported in an ALS/FTD family with
    a supporting burden analysis, but the Project MinE consortium holds that the
    pedigree and burden data do not establish causality without replication.
    Graded DISPUTED for that reason. TIA1 is not listed in Orphanet's ORPHA:803
    gene table for ALS, and no ClinGen assertion for TIA1 and ALS is present in
    references_cache/.
  evidence:
  - reference: PMID:28817800
    reference_title: "TIA1 Mutations in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Promote Phase Separation and Alter Stress Granule Dynamics."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Subsequent genetic association analyses showed an increased burden of TIA1 LCD mutations in ALS patients compared to controls (p = 8.7 × 10-6)."
    explanation: >
      The burden analysis offered in support of TIA1 as an ALS gene.
  - reference: PMID:29235362
    reference_title: "Reconsidering the causality of TIA1 mutations in ALS."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we argue that data from the published pedigree that supports TIA1 is insufficient to prove causality."
    explanation: >
      The published challenge to that evidence, and the basis for the DISPUTED grade.
- name: LRP12
  gene_term:
    preferred_term: LRP12
    term:
      id: hgnc:31708
      label: LRP12
  association: Causative
  relationship_type: CAUSATIVE
  subtype: ALS28
  notes: >
    CGG repeat expansions of 61-100 units in LRP12 were reported as a cause of
    ALS in five families and two simplex individuals; longer expansions
    in the same repeat cause oculopharyngodistal myopathy type 1. Replication is
    currently limited to patients of Asian ancestry: a whole-genome screen of 608
    sporadic ALS patients, 35 familial probands and 4,703 controls of European
    ancestry found no expanded alleles. Graded CAUSATIVE on the primary report
    rather than DISPUTED, because the European study reports absence in a
    different population rather than contradicting the original families.
    LRP12 is not listed in Orphanet's ORPHA:803 gene table for ALS.
  evidence:
  - reference: PMID:37339631
    reference_title: "CGG repeat expansion in LRP12 in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In conclusion, CGG repeat expansions in LRP12 cause ALS and OPDM, depending on the length of the repeat."
    explanation: >
      The primary report's conclusion, which is the basis for the CAUSATIVE grade.
  - reference: PMID:38726482
    reference_title: "Short tandem repeat expansions in LRP12 are absent in cohorts of familial and sporadic amyotrophic lateral sclerosis patients of European ancestry."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "To date, LRP12 CGG repeat expansions have not been reported in ALS patients of European ancestry and may be limited to rare ALS patients of Asian ancestry and atypical clinical presentations."
    explanation: >
      Supports the ancestry restriction recorded in the notes above; it bears on
      the scope of the claim rather than directly on whether the expansion is
      pathogenic in the families where it was found.
environmental:
- name: Heavy Metal Exposure
  exposure_term:
    preferred_term: exposure to heavy metal
    term:
      id: ECTO:9002163
      label: exposure to heavy metal
  influences_mechanisms:
  - target: Motor Neuron Degeneration
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Lead and cadmium are the most consistently implicated exposures,
      plausibly acting through oxidative stress, but no step between exposure
      and motor neuron loss is established. The effect size is modest and no
      environmental cause of this disease is proven.
    evidence:
    - reference: PMID:31578652
      reference_title: "Population-based study of environmental/occupational lead exposure and amyotrophic lateral sclerosis: a systematic review and meta-analysis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The ratio of maximal/minimal lead exposure yielded a pooled odds ratio (OR) of 1.46 (95% confidence interval (CI) 1.16-1.83) with moderate heterogeneity (I2 = 51.8%; p = 0.019)."
      explanation: >-
        Reports a pooled odds ratio of 1.46 comparing maximal with minimal
        lead exposure, an epidemiological association of modest size.
  notes: Occupational and environmental exposure to lead, cadmium, mercury, and other heavy metals has been associated with increased ALS risk. Prospective pre-diagnostic blood-metal data (which minimize reverse causation) implicate cadmium and lead, with zinc inversely associated.
  evidence:
  - reference: PMID:31578652
    reference_title: "Population-based study of environmental/occupational lead exposure and amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The ratio of maximal/minimal lead exposure yielded a pooled odds ratio (OR) of 1.46 (95% confidence interval (CI) 1.16-1.83) with moderate heterogeneity (I2 = 51.8%; p = 0.019)."
    explanation: Meta-analysis finds lead exposure positively associated with ALS risk across population-based studies.
  - reference: PMID:33068316
    reference_title: "Blood Metal Levels and Amyotrophic Lateral Sclerosis Risk: A Prospective Cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "cadmium and lead may be associated with an increased risk of ALS and zinc with a decreased risk. This is the first study to evaluate predisease metal levels in blood, thus minimizing reverse causation."
    explanation: Nested case-control study in the prospective EPIC cohort measured pre-diagnostic blood metals, implicating cadmium and lead (and protective zinc) with a design that minimizes reverse causation. Identified as an un-integrated finding from the ALS environmental-toxicity deep-research report.
- name: Pesticide Exposure
  exposure_term:
    preferred_term: exposure to pesticide
    term:
      id: ECTO:0000530
      label: exposure to pesticide
  influences_mechanisms:
  - target: Motor Neuron Degeneration
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Pesticides are analysed as a class rather than as specific compounds, so
      the association cannot identify a responsible agent, let alone a
      mechanism.
    evidence:
    - reference: PMID:22521219
      reference_title: "Pesticide exposure and amyotrophic lateral sclerosis."
      supports: SUPPORT
      snippet: "In the meta-analysis, ALS was associated with use of pesticides as a group (1.9, 1.1-3.1)."
      evidence_source: HUMAN_CLINICAL
      explanation: >-
        Reports an odds ratio of 1.9 for pesticides analysed as a group, an
        association at class level rather than for any identified compound.
  notes: Agricultural pesticide exposure has been linked to increased ALS incidence in epidemiological studies.
  evidence:
  - reference: PMID:22521219
    reference_title: "Pesticide exposure and amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "In the meta-analysis, ALS was associated with use of pesticides as a group (1.9, 1.1-3.1)."
    explanation: Systematic review and AHS cohort analysis report elevated ALS odds with pesticide exposure.
- name: Military Service
  influences_mechanisms:
  - target: Motor Neuron Degeneration
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      A setting rather than an exposure, bundling possible chemical, physical
      and traumatic contributions that the epidemiology cannot separate.
    evidence:
    - reference: PMID:14504315
      reference_title: "Occurrence of amyotrophic lateral sclerosis among Gulf War veterans."
      supports: SUPPORT
      snippet: "A significant elevated risk of ALS occurred among all deployed personnel (RR = 1.92; 95% CL = 1.29, 2.84)"
      evidence_source: HUMAN_CLINICAL
      explanation: >-
        Reports a relative risk of 1.92 among all deployed personnel, an
        association with the setting rather than with any identified exposure
        within it.
  notes: Veterans have approximately twice the risk of developing ALS compared to the general population, possibly related to environmental exposures.
  evidence:
  - reference: PMID:14504315
    reference_title: "Occurrence of amyotrophic lateral sclerosis among Gulf War veterans."
    supports: SUPPORT
    snippet: "A significant elevated risk of ALS occurred among all deployed personnel (RR = 1.92; 95% CL = 1.29, 2.84)"
    explanation: Gulf War veteran cohort showed nearly twofold higher ALS risk compared with non-deployed personnel.
- name: Smoking
  exposure_term:
    preferred_term: exposure to tobacco smoking
    term:
      id: ECTO:6000029
      label: exposure to tobacco smoking
  influences_mechanisms:
  - target: Motor Neuron Degeneration
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The weakest of the exposures here and sex-dependent: the association in
      men is null while in women it is clear. The sex-specific figures are
      meta-regression predicted values rather than directly pooled
      sex-stratified estimates. Recorded because the sex difference is itself
      informative, not because smoking is established as a cause.
    evidence:
    - reference: PMID:20639382
      reference_title: "Smoking and the risk of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "was 0.86 (0.71 to 1.03) in men and 1.66 (1.31 to 2.10) in women."
      explanation: >-
        Gives meta-regression predicted relative risks of 0.86 in men and 1.66
        in women, an association present only in women. Support is PARTIAL
        because these are modelled rather than directly pooled values, and the
        pooled current-versus-never estimate does not exclude no effect.
  notes: >-
    Cigarette smoking is the most consistently reported environmental ALS risk factor,
    though the overall association is modest; in this meta-analysis the clearest signal
    is a sex-specific increased risk in women (ever-smoker RR 1.66, 95% CI 1.31-2.10),
    while the overall pooled estimates were not statistically significant.
  evidence:
  - reference: PMID:20639382
    reference_title: "Smoking and the risk of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pooled RR (95% CI) of ALS was 1.28 (0.97 to 1.68) for current versus never smokers and 1.12 (0.98 to 1.27) for ever versus never smokers."
    explanation: Meta-analysis of case-control and cohort studies found overall pooled relative risks that were elevated but not statistically significant (confidence intervals crossing 1.0), providing only partial support for smoking as an ALS risk factor.
  - reference: PMID:20639382
    reference_title: "Smoking and the risk of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "was 0.86 (0.71 to 1.03) in men and 1.66 (1.31 to 2.10) in women."
    explanation: Sex-stratified analysis shows a statistically significant elevated ALS risk in women who ever smoked (RR 1.66, 95% CI 1.31-2.10) but not in men, supporting the sex-specific smoking-ALS association.
- name: Repetitive Head Trauma and Contact Sports
  influences_mechanisms:
  - target: Motor Neuron Degeneration
    environmental_effect: PREDISPOSES
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Repeated head and cervical trauma is associated with a modestly raised
      risk. Reverse causation is a genuine concern here, since early motor
      impairment may itself increase falls and injury.
    evidence:
    - reference: PMID:37284659
      reference_title: "Risk factors associated with amyotrophic lateral sclerosis based on the observational study: a systematic review and meta-analysis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "head trauma (OR = 1.26, 95% CI = 1.13, 1.40)"
      explanation: >-
        Reports an odds ratio of 1.26 for head trauma, a modest association.
  notes: Repetitive concussive head and cervical-spinal trauma, particularly from professional contact sports (American football, soccer/association football, boxing), is associated with a markedly increased risk of ALS; head trauma is also an independent risk factor in broad risk-factor meta-analyses. The association overlaps the trauma-driven TDP-43 proteinopathy seen in chronic traumatic encephalopathy.
  evidence:
  - reference: PMID:30775214
    reference_title: "Contact Sports as a Risk Factor for Amyotrophic Lateral Sclerosis: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "repetitive concussive head and cervical spinal trauma result in an increased risk of ALS compared with the general population or nonsport controls."
    explanation: Systematic review concludes that contact sports involving repetitive concussive head and cervical-spinal trauma increase ALS risk (with a pooled rate ratio of 8.52 for professional such sports). Identified as an un-integrated finding from the ALS environmental-toxicity deep-research report.
  - reference: PMID:37284659
    reference_title: "Risk factors associated with amyotrophic lateral sclerosis based on the observational study: a systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "head trauma (OR = 1.26, 95% CI = 1.13, 1.40)"
    explanation: Comprehensive observational meta-analysis identifies head trauma as an independent risk factor for ALS, corroborating the contact-sports signal.
treatments:
- name: Riluzole
  description: >
    Glutamate antagonist that modestly extends survival by 2-3 months. It is the first
    FDA-approved treatment for ALS and works by reducing excitotoxic neuronal damage.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: riluzole
      term:
        id: NCIT:C47704
        label: Riluzole
  evidence:
  - reference: PMID:8302340
    reference_title: "A controlled trial of riluzole in amyotrophic lateral sclerosis. ALS/Riluzole Study Group."
    supports: SUPPORT
    snippet: "The antiglutamate agent riluzole appears to slow the progression of amyotrophic lateral sclerosis, and it may improve survival in patients with disease of bulbar onset."
    explanation: Landmark trial demonstrating riluzole's survival benefit in ALS patients.
  target_mechanisms:
  - target: Glutamate Excitotoxicity
    treatment_effect: INHIBITS
    description: >-
      Riluzole blocks voltage-gated sodium channels and reduces glutamate release
      at presynaptic terminals, attenuating excitotoxic motor neuron injury.
- name: Edaravone
  description: >
    Free-radical scavenger approved for ALS. A phase 3 trial in a selected subset of
    early-stage patients, defined from a post-hoc analysis of an earlier trial, showed a
    smaller decline in ALSFRS-R than placebo; a large real-world cohort found long-term
    intravenous edaravone well tolerated but without disease-modifying benefit. Benefit
    outside the trial-defined subset is therefore not established.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: edaravone
      term:
        id: CHEBI:31530
        label: edaravone
  evidence:
  - reference: PMID:28522181
    reference_title: "Safety and efficacy of edaravone in well defined patients with amyotrophic lateral sclerosis: a randomised, double-blind, placebo-controlled trial."
    supports: SUPPORT
    snippet: "Edaravone showed efficacy in a small subset of people with ALS who met criteria identified in post-hoc analysis of a previous phase 3 study, showing a significantly smaller decline of ALSFRS-R score compared with placebo."
    explanation: >-
      Phase 3 trial reporting a smaller ALSFRS-R decline with edaravone than placebo
      in a narrowly selected subset of patients defined by post-hoc criteria from an
      earlier trial; the benefit is not shown for ALS patients generally.
  - reference: PMID:35006266
    reference_title: "Safety and Effectiveness of Long-term Intravenous Administration of Edaravone for Treatment of Patients With Amyotrophic Lateral Sclerosis."
    supports: REFUTE
    snippet: "although long-term intravenous edaravone therapy for patients with ALS was feasible and mainly well tolerated, it was not associated with any disease-modifying benefit."
    explanation: Real-world cohort study found long-term intravenous edaravone well tolerated but without additional disease-modifying benefit versus standard therapy.
  target_mechanisms:
  - target: Oxidative Stress
    treatment_effect: INHIBITS
    description: >-
      Edaravone is a free-radical scavenger that neutralizes reactive oxygen
      species, reducing oxidative neuronal injury in motor neurons.
- name: Tofersen
  therapeutic_modality: ANTISENSE_OLIGONUCLEOTIDE
  oligonucleotide_details:
    oligonucleotide_mechanism: RNASE_H_KNOCKDOWN
    target_gene:
      preferred_term: SOD1
      term:
        id: hgnc:11179
        label: SOD1
    target_transcript: SOD1 mRNA
    oligonucleotide_chemistry: TWO_PRIME_O_METHOXYETHYL
    conjugation: UNCONJUGATED
    delivery_platform: UNFORMULATED
  description: >
    Antisense oligonucleotide therapy approved for SOD1-ALS that reduces SOD1 protein
    production, targeting the underlying genetic cause in this subset of patients.
    The approval rests on target engagement and biomarker lowering rather than on a
    positive randomized clinical endpoint: over the 28-week randomized period of VALOR
    tofersen lowered CSF SOD1 and plasma neurofilament light chain but did not improve
    the prespecified clinical endpoints. A later integrated analysis of VALOR and its
    open-label extension reported numerically less functional, respiratory, strength
    and quality-of-life decline over 148 weeks with earlier rather than delayed
    initiation; because that comparison follows crossover and is open-label with
    substantial attrition, it is supportive long-term observation rather than a
    blinded randomized efficacy result.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: tofersen
      term:
        id: NCIT:C166584
        label: Tofersen
  evidence:
  - reference: PMID:32640130
    reference_title: "Phase 1-2 Trial of Antisense Oligonucleotide Tofersen for SOD1 ALS."
    supports: SUPPORT
    snippet: "In adults with ALS due to SOD1 mutations, CSF SOD1 concentrations decreased at the highest concentration of tofersen administered intrathecally over a period of 12 weeks."
    explanation: Phase 1-2 trial demonstrating tofersen reduces CSF SOD1 levels in SOD1-ALS patients.
  - reference: PMID:36129998
    reference_title: "Trial of Antisense Oligonucleotide Tofersen for SOD1 ALS."
    supports: SUPPORT
    snippet: "The intrathecally administered antisense oligonucleotide tofersen reduces synthesis of the superoxide dismutase 1 (SOD1) protein and is being studied in patients with amyotrophic lateral sclerosis (ALS) associated with mutations in SOD1 (SOD1 ALS)."
    explanation: VALOR pivotal phase 3 trial (the basis for tofersen's FDA approval) confirms the antisense mechanism reduces SOD1 protein synthesis in SOD1 ALS.
  - reference: PMID:36129998
    reference_title: "Trial of Antisense Oligonucleotide Tofersen for SOD1 ALS."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In persons with SOD1 ALS, tofersen reduced concentrations of SOD1 in CSF and of neurofilament light chains in plasma over 28 weeks but did not improve clinical end points and was associated with adverse events."
    explanation: >-
      VALOR's own conclusion is the basis for this entry's statement that the
      tofersen evidence is target-engagement- and biomarker-led. It records that
      the randomized 28-week period lowered CSF SOD1 and plasma neurofilament
      light chain without improving the prespecified clinical endpoints.
  - reference: PMID:41661214
    reference_title: "Long-Term Tofersen in SOD1 Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Over 148 weeks, earlier initiation of tofersen (compared to later initiation) was associated with numerically less decline in measures of clinical function"
    explanation: >-
      Integrated VALOR plus open-label-extension analysis supporting the
      longer-term early-start advantage described here. The reported difference
      is numerical and comes from an open-label, post-crossover comparison with
      substantial attrition, which is why this entry does not present it as a
      randomized efficacy result.
  target_mechanisms:
  - target: Motor Neuron Degeneration
    treatment_effect: MODULATES
    description: >-
      Tofersen reduces mutant SOD1 protein levels via RNase H-mediated mRNA
      knockdown, reducing the SOD1-driven oxidative and proteotoxic burden that
      accelerates motor neuron loss in SOD1-ALS.
- name: Jacifusen (ION363)
  therapeutic_modality: ANTISENSE_OLIGONUCLEOTIDE
  oligonucleotide_details:
    oligonucleotide_mechanism: RNASE_H_KNOCKDOWN
    target_gene:
      preferred_term: FUS
      term:
        id: hgnc:4010
        label: FUS
    target_transcript: FUS pre-mRNA
  description: >
    Investigational antisense oligonucleotide (ION363, also known as ulefnersen) that
    non-allele-specifically silences FUS to lower wild-type and mutant FUS protein,
    targeting the gain-of-function genetic cause in FUS-ALS. Delivered by serial
    intrathecal injection; evaluated in an expanded-access case series and an ongoing
    clinical trial.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: ulefnersen
      term:
        id: NCIT:C188629
        label: Ulefnersen
  evidence:
  - reference: PMID:40414239
    reference_title: "Antisense oligonucleotide jacifusen for FUS-ALS: an investigator-initiated, multicentre, open-label case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Jacifusen is an antisense oligonucleotide targeting FUS pre-mRNA, previously shown to delay neurodegeneration in a mouse model and potentially slow functional decline in a first-in-human study."
    explanation: Lancet expanded-access case series confirms jacifusen is an ASO targeting FUS pre-mRNA, supporting the FUS-knockdown mechanism of this treatment.
  - reference: PMID:40414239
    reference_title: "Antisense oligonucleotide jacifusen for FUS-ALS: an investigator-initiated, multicentre, open-label case series."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Biochemical and immunohistochemical analysis of CNS tissue samples from four participants showed reduced FUS protein levels and an apparent decrease in the burden of FUS pathology."
    explanation: Post-mortem CNS analysis in treated patients demonstrates jacifusen lowers FUS protein and FUS-aggregate burden, the intended target-engagement readout in humans.
  - reference: PMID:35075293
    reference_title: "Antisense oligonucleotide silencing of FUS expression as a therapeutic approach in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "ION363, a non-allele-specific FUS antisense oligonucleotide, efficiently silences Fus and reduces postnatal levels of FUS protein in the brain and spinal cord, delaying motor neuron degeneration."
    explanation: Preclinical FUS knock-in mouse study establishes that ION363 silences Fus and delays motor neuron degeneration, the model-organism basis for the human program.
  target_mechanisms:
  - target: Motor Neuron Degeneration
    treatment_effect: MODULATES
    description: >-
      Jacifusen silences FUS expression via RNase H-mediated knockdown, reducing
      mutant FUS protein aggregation and toxicity in motor neurons and delaying
      neurodegeneration in FUS-ALS.
- name: Triumeq
  description: >
    Antiretroviral therapy (combination of dolutegravir, lamivudine, and abacavir) proposed for treating TDP-43-associated ALS
    through modulation of endogenous retroviruses. In preclinical models, Triumeq transiently and modestly improves early motor
    function without impacting overall disease progression, and reduces TDP-43-driven neuroinflammation via suppression of
    transcription factor ATF4 and inflammatory markers CXCL10 and IRF-1.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: abacavir/dolutegravir/lamivudine
      term:
        id: NCIT:C157543
        label: Abacavir/Dolutegravir/Lamivudine
  target_mechanisms:
  - target: Endogenous Retrovirus Reactivation and TDP-43 Feedback
    treatment_effect: INHIBITS
    description: >-
      Triumeq's antiretroviral components (the integrase inhibitor dolutegravir
      plus the reverse-transcriptase inhibitors abacavir and lamivudine) target
      the ERV (HERV-K) reactivation arm of the ERV-TDP-43 feedback loop.
  - target: Neuroinflammation
    treatment_effect: INHIBITS
    description: >
      Triumeq suppresses TDP-43-driven inflammatory gene expression in the ALS
      neuroinflammation axis, including ATF4, CXCL10, and IRF-1.
    evidence:
    - reference: PMID:42204279
      reference_title: "Evaluation of triumeq treatment on a TDP-43 mouse model of amyotrophic Lateral sclerosis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In this TDP-43 ALS mouse model, there was a positive association of TDP-43 mRNA levels with transcription factor ATF4, and inflammatory markers CXCL10 and IRF-1, and Triumeq treatment negated this association."
      explanation: Triumeq negated TDP-43-associated inflammatory marker upregulation, linking the treatment to inhibition of the Neuroinflammation pathophysiology node.
  evidence:
  - reference: PMID:42204279
    reference_title: "Evaluation of triumeq treatment on a TDP-43 mouse model of amyotrophic Lateral sclerosis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Triumeq treatment significantly improved motor function early on in the disease course"
    explanation: Preclinical study shows early motor function improvement in the TDP-43 ALS mouse model, but the abstract qualifies the effect as transient and modest with no impact on other progression markers or disease endpoint.
  - reference: PMID:42204279
    reference_title: "Evaluation of triumeq treatment on a TDP-43 mouse model of amyotrophic Lateral sclerosis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In this TDP-43 ALS mouse model, there was a positive association of TDP-43 mRNA levels with transcription factor ATF4, and inflammatory markers CXCL10 and IRF-1, and Triumeq treatment negated this association."
    explanation: Triumeq modulates TDP-43-driven neuroinflammation by suppressing ATF4 and inflammatory cytokines in disease model.
- name: Sodium Phenylbutyrate-Taurursodiol (AMX0035)
  description: >
    Fixed-dose combination of sodium phenylbutyrate and taurursodiol (tauroursodeoxycholic
    acid) intended to reduce endoplasmic-reticulum and mitochondrial stress-mediated motor
    neuron death, marketed as Relyvrio (US) / Albrioza (Canada). The phase 2 CENTAUR trial
    showed slower functional decline, supporting accelerated FDA approval in 2022, but the
    confirmatory phase 3 PHOENIX trial showed no benefit at 48 weeks and the sponsor
    voluntarily withdrew the drug from the market in 2024. Included here to document a
    withdrawn ALS therapy whose disease-modifying benefit was not confirmed.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: sodium phenylbutyrate
      term:
        id: CHEBI:75316
        label: sodium phenylbutyrate
    - preferred_term: tauroursodeoxycholic acid
      term:
        id: CHEBI:80774
        label: tauroursodeoxycholic acid
  evidence:
  - reference: PMID:32877582
    reference_title: "Trial of Sodium Phenylbutyrate-Taurursodiol for Amyotrophic Lateral Sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the mean rate of change in the ALSFRS-R score was -1.24 points per month with the active drug and -1.66 points per month with placebo (difference, 0.42 points per month; 95% confidence interval, 0.03 to 0.81; P = 0.03)."
    explanation: >-
      The phase 2 CENTAUR randomized controlled trial showed a statistically significant
      slowing of ALSFRS-R functional decline versus placebo — the result that supported the
      2022 accelerated FDA approval.
  - reference: PMID:38909349
    reference_title: "Sodium Phenylbutyrate and Tauroursodeoxycholic Acid: A Story of Hope Turned to Disappointment in Amyotrophic Lateral Sclerosis Treatment."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "results from the Phase 3 PHOENIX trial (NCT05021536) showed no change in ALSFRS-R total score at 48 weeks."
    explanation: >-
      The confirmatory phase 3 PHOENIX trial found no effect on the primary functional
      endpoint, refuting a disease-modifying benefit and reversing the CENTAUR signal.
  - reference: PMID:38909349
    reference_title: "Sodium Phenylbutyrate and Tauroursodeoxycholic Acid: A Story of Hope Turned to Disappointment in Amyotrophic Lateral Sclerosis Treatment."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "the sponsor company initiated the process with the US FDA and Health Canada to voluntarily withdraw the marketing authorizations for PB-TUDCA."
    explanation: >-
      Following the negative PHOENIX trial, the sponsor voluntarily withdrew marketing
      authorizations in the US and Canada (2024), documenting the therapy's removal from clinical use.
- name: Non-invasive Ventilation
  description: >
    Respiratory support using BiPAP or similar devices to assist breathing as respiratory
    muscles weaken. This improves quality of life and extends survival.
  treatment_term:
    preferred_term: noninvasive ventilation
    term:
      id: NCIT:C171457
      label: Non-Invasive Mechanical Ventilation
  evidence:
  - reference: PMID:16426990
    reference_title: "Effects of non-invasive ventilation on survival and quality of life in patients with amyotrophic lateral sclerosis: a randomised controlled trial."
    supports: SUPPORT
    snippet: "This subgroup showed improvement in several measures of quality of life and a median survival benefit of 205 days (p=0.006) with maintained quality of life for most of this period."
    explanation: Randomized controlled trial demonstrated non-invasive ventilation improves quality of life and extends survival in ALS patients with preserved bulbar function.
  - reference: PMID:39019674
    reference_title: "Proposals from a French expert panel for respiratory care in ALS patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Non-invasive ventilation (NIV), which is the main recognized treatment for alleviating the symptoms of respiratory failure, prolongs survival and improves quality of life."
    explanation: The French expert-panel respiratory-care guideline affirms non-invasive ventilation as the main recognized treatment for ALS respiratory failure, prolonging survival and improving quality of life.
- name: Physical Therapy
  description: >
    Range of motion exercises and adaptive strategies to maintain function and prevent
    complications such as contractures.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Physical Therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  evidence:
  - reference: PMID:24510737
    reference_title: "Rehabilitation in amyotrophic lateral sclerosis: why it matters."
    supports: SUPPORT
    snippet: "Multidisciplinary care includes rehabilitation interventions that have the goal of assisting people to teach their fullest potential despite the presence of a disabling disease."
    explanation: Review describes how rehabilitation including physical therapy helps maximize independence and function in ALS patients.
- name: Speech Therapy
  description: >
    Techniques to optimize communication and swallowing safety, including augmentative
    and alternative communication devices.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: speech therapy
    term:
      id: NCIT:C159273
      label: Speech Language Therapy
  evidence:
  - reference: PMID:24510737
    reference_title: "Rehabilitation in amyotrophic lateral sclerosis: why it matters."
    supports: SUPPORT
    snippet: "This review will present rehabilitation strategies that can be utilized to maximize patient independence, function, safety, and quality of life, and to minimize disease-related symptoms."
    explanation: Review covers multidisciplinary rehabilitation including speech therapy for ALS patients.
- name: Percutaneous Endoscopic Gastrostomy
  description: >
    Feeding tube placement to maintain nutrition when swallowing becomes unsafe or
    inadequate due to bulbar involvement.
  treatment_term:
    preferred_term: Percutaneous Endoscopic Gastrostomy
    term:
      id: NCIT:C106040
      label: Percutaneous Endoscopic Gastrostomy
  evidence:
  - reference: PMID:39207520
    reference_title: "Narrative review of diagnosis, management and treatment of dysphagia and sialorrhea in amyotrophic lateral sclerosis."
    supports: SUPPORT
    snippet: "Early discussion of potential treatments such as high-calorie diets or percutaneous endoscopic gastrostomy (PEG) is crucial."
    explanation: Dysphagia management review underscores PEG as an essential intervention when nutrition is compromised in ALS.
- name: Multidisciplinary Care
  description: >
    Coordinated care from neurologists, pulmonologists, physical therapists, occupational
    therapists, speech therapists, nutritionists, and palliative care specialists extends
    survival and improves quality of life.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:24510737
    reference_title: "Rehabilitation in amyotrophic lateral sclerosis: why it matters."
    supports: SUPPORT
    snippet: "Multidisciplinary care includes rehabilitation interventions that have the goal of assisting people to teach their fullest potential despite the presence of a disabling disease."
    explanation: Rehabilitation review emphasizes multidisciplinary care as core to ALS management to optimize function and quality of life.
prevalence:
- population: Europe
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_low: 1.0
  rate_high: 9.0
  notes: Orphanet European point-prevalence class 1-9 / 100,000 (band-only source; no point estimate reported).
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "1-9 / 100 000 | Europe | Point prevalence | PMID:19192301,EXPERT"
    explanation: Orphanet epidemiology table reports a European point prevalence of 1-9 per 100,000.
- population: Europe
  measure_type: ANNUAL_INCIDENCE
  prevalence_class: BAND_1_9_PER_100000
  rate_low: 1.0
  rate_high: 9.0
  notes: Orphanet European annual-incidence class 1-9 / 100,000 (band-only source; no point estimate reported).
  evidence:
  - reference: ORPHA:803
    reference_title: "Amyotrophic lateral sclerosis"
    supports: SUPPORT
    snippet: "1-9 / 100 000 | Europe | Annual incidence | PMID:19710046,EXPERT"
    explanation: Orphanet epidemiology table reports a European annual incidence of 1-9 per 100,000.
datasets:
- accession: gtex:GTEx_v8_Spinal_cord_cervical_c-1
  title: GTEx v8 Spinal Cord (cervical c-1)
  description: Bulk RNA-seq from healthy cervical spinal cord to provide baseline expression for upper and lower motor neuron pathways affected in ALS.
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_types:
  - preferred_term: spinal cord
    term:
      id: UBERON:0002240
      label: spinal cord
  publication: PMID:32913098
  evidence:
  - reference: PMID:32913098
    reference_title: "The GTEx Consortium atlas of genetic regulatory effects across human tissues."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we present analyses of the version 8 data, examining 15,201 RNA-sequencing samples from 49 tissues of 838 postmortem donors."
    explanation: >-
      Identifies GTEx v8, the postmortem cross-tissue RNA-seq release this healthy
      cervical spinal cord reference is drawn from. It attests the dataset rather than any ALS
      finding.
- accession: gtex:GTEx_v8_Skeletal_Muscle
  title: GTEx v8 Skeletal Muscle
  description: Bulk RNA-seq from healthy skeletal muscle to benchmark ALS-related denervation signatures and muscle atrophy pathways.
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: BULK_RNA_SEQ
  sample_types:
  - preferred_term: skeletal muscle tissue
    term:
      id: UBERON:0001134
      label: skeletal muscle tissue
  publication: PMID:32913098
  evidence:
  - reference: PMID:32913098
    reference_title: "The GTEx Consortium atlas of genetic regulatory effects across human tissues."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we present analyses of the version 8 data, examining 15,201 RNA-sequencing samples from 49 tissues of 838 postmortem donors."
    explanation: >-
      Identifies GTEx v8, the postmortem cross-tissue RNA-seq release this healthy
      skeletal muscle reference is drawn from. It attests the dataset rather than any ALS
      finding.
animal_models:
- name: Canine degenerative myelopathy (SOD1 E40K homozygous dog)
  species: Dog
  genotype: SOD1 c.118G>A (p.E40K) homozygous
  background: Pembroke Welsh Corgi, Boxer, Rhodesian Ridgeback, German Shepherd Dog,
    Chesapeake Bay Retriever
  publication: PMID:19188595
  description: >
    Canine degenerative myelopathy (DM) is a naturally occurring, adult-onset,
    fatal neurodegenerative disease caused by homozygosity for the SOD1 c.118G>A
    (p.E40K) missense mutation, identified across five breeds. Progressive upper
    motor neuron spastic ataxia in the pelvic limbs typically begins at 8 years
    or older, ascending to flaccid tetraparesis if euthanasia is delayed. Spinal
    cord histology reveals myelin and axon loss in the lateral white matter and
    neuronal cytoplasmic SOD1-immunoreactive inclusions mirroring human ALS
    pathology. This is the first recognized spontaneously occurring animal model
    for ALS.
  evidence:
  - reference: PMID:19188595
    reference_title: "Genome-wide association analysis reveals a SOD1 mutation in canine degenerative myelopathy that resembles amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our findings identify canine DM to be the first recognized spontaneously occurring animal model for ALS."
    explanation: >
      Awano et al. 2009 identified the SOD1 E40K mutation in DM-affected dogs by
      genome-wide association mapping and demonstrated SOD1-immunoreactive
      cytoplasmic inclusions similar to human ALS pathology, formally establishing
      canine DM as the first spontaneous large-animal ALS model.
  modeled_mechanisms:
  - target: Motor Neuron Degeneration
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Naturally occurring, adult-onset SOD1-associated degeneration of the spinal
      cord, with neuronal cytoplasmic SOD1-immunoreactive inclusions matching
      those of human SOD1-ALS.
    limitations: >-
      E40K is not among the SOD1 alleles that cause human ALS, and DM presents as
      an ascending spinal myelopathy beginning with pelvic-limb upper motor neuron
      signs rather than the focal limb or bulbar onset typical of human ALS.
      Disease-course and therapeutic inferences should not be transferred without
      corroboration in human tissue.
    readouts:
    - name: Lateral white matter myelin and axon content
      target: Motor Neuron Degeneration
      description: >-
        Spinal cord histology in affected dogs, scored against unaffected
        controls of the same breeds.
      direction: DECREASED
      interpretation: >-
        Myelin and axon loss confined to the lateral white matter is the
        structural correlate of the degeneration node in this model.
      evidence:
      - reference: PMID:19188595
        reference_title: "Genome-wide association analysis reveals a SOD1 mutation in canine degenerative myelopathy that resembles amyotrophic lateral sclerosis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Microscopic examination of spinal cords from affected dogs revealed myelin and axon loss affecting the lateral white matter"
        explanation: >-
          Awano et al. report the histological measurement underlying this
          readout.
    - name: SOD1-immunoreactive neuronal cytoplasmic inclusions
      target: Motor Neuron Degeneration
      description: >-
        Anti-SOD1 immunohistochemistry of spinal cord sections from affected
        dogs.
      direction: INCREASED
      interpretation: >-
        Inclusion pathology is what ties this model to human SOD1-ALS rather than
        to non-specific myelopathy; the authors compare it directly against human
        ALS spinal cord.
      evidence:
      - reference: PMID:19188595
        reference_title: "Genome-wide association analysis reveals a SOD1 mutation in canine degenerative myelopathy that resembles amyotrophic lateral sclerosis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "These inclusions are similar to those seen in spinal cord sections from ALS patients with SOD1 mutations."
        explanation: >-
          Establishes correspondence between the model's inclusion pathology and
          human SOD1-ALS.
    evidence:
    - reference: PMID:19188595
      reference_title: "Genome-wide association analysis reveals a SOD1 mutation in canine degenerative myelopathy that resembles amyotrophic lateral sclerosis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Our findings identify canine DM to be the first recognized spontaneously occurring animal model for ALS."
      explanation: >-
        Supports treating this model as informative for the motor neuron
        degeneration node.
- name: Equine motor neuron disease (vitamin E-deficient horse)
  species: Horse
  genotype: acquired (vitamin E deficiency / chronic oxidative stress)
  publication: PMID:7988544
  description: >
    Equine motor neuron disease (EMND) is a naturally occurring, acquired lower
    motor neuron disease of adult horses linked to chronic vitamin E deficiency
    and oxidative stress, arising in horses stabled without access to pasture.
    Clinical signs include progressive weight loss, muscle fasciculations, constant
    weight shifting in the rear limbs, abnormally low head carriage, and excessive
    recumbency. Pathological findings include type 1 muscle fibre atrophy and
    lipopigment accumulation in spinal cord capillary endothelium. Unlike classic
    ALS, which requires combined upper and lower motor neuron degeneration, EMND
    involves predominantly lower motor neurons (no upper motor neuron involvement),
    limiting direct phenotypic equivalence to human ALS.
  evidence:
  - reference: PMID:7988544
    reference_title: "Equine motor neuron disease: findings in 28 horses and proposal of a pathophysiological mechanism for the disease."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Pathological findings, preference of type 1 muscle fibre atrophy and lipopigment accumulation within the capillary endothelium of the spinal cord of all cases, supported the hypothesis of EMND being an oxidative disease."
    explanation: >
      Divers et al. 1994 described the clinical and pathological features of EMND
      in 28 horses and proposed oxidative stress as the pathophysiological
      mechanism, establishing this naturally occurring condition as a motor neuron
      disease analog.
  - reference: PMID:9373362
    reference_title: "Intrinsic, management, and nutritional factors associated with equine motor neuron disease."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The relationship of specific nutritional factors to EMND supports the hypothesis that a deficiency of vitamin E contributes to the disease."
    explanation: >
      de la Rúa-Domènech et al. 1997 identified vitamin E deficiency as a key
      risk factor for EMND in a case-control study of 87 affected horses and 259
      controls, reinforcing the oxidative stress pathophysiology.
  modeled_mechanisms:
  - target: Motor Neuron Degeneration
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: >-
      Adult-onset degeneration of lower motor neurons with denervation muscle
      pathology, arising spontaneously under chronic nutritional oxidative
      stress.
    limitations: >-
      EMND involves predominantly lower motor neurons with no upper motor neuron
      involvement, so it does not reproduce the combined upper and lower motor
      neuron degeneration that defines human ALS. It is also acquired and
      nutritional rather than genetic, so it carries no information about the
      familial ALS genotypes.
    readouts:
    - name: Type 1 muscle fibre atrophy
      target: Motor Neuron Degeneration
      description: Muscle histopathology in affected horses at post mortem.
      direction: INCREASED
      interpretation: >-
        Denervation atrophy is the downstream muscle correlate of lower motor
        neuron loss, and is the readout that supports the partial rather than
        full correspondence to ALS.
      evidence:
      - reference: PMID:7988544
        reference_title: "Equine motor neuron disease: findings in 28 horses and proposal of a pathophysiological mechanism for the disease."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "preference of type 1 muscle fibre atrophy"
        explanation: >-
          Divers et al. report type 1 fibre atrophy as a consistent pathological
          finding across all cases.
    evidence:
    - reference: PMID:2209016
      reference_title: "Equine motor neuron disease; a preliminary report."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Pathologic studies revealed that degeneration and loss of motor neurons in the spinal cord and brain stem resulted in axonal degeneration in the ventral roots and peripheral and cranial nerves and denervation atrophy of skeletal muscle."
      explanation: >-
        The first pathological description of EMND reports degeneration and loss of
        spinal and brainstem motor neurons with denervation atrophy. These are lower
        motor neuron populations only, which is why the link is a partial
        recapitulation of the human degeneration node.
  - target: Oxidative Stress
    relationship: RECAPITULATES
    fidelity: LOW
    description: >-
      Chronic vitamin E deficiency is proposed to produce a sustained oxidative
      insult to motor neurons, giving a naturally occurring model of the
      oxidative stress node that is separable from any genetic lesion.
    limitations: >-
      The oxidative insult here is nutritional; it is a model of oxidative stress
      as a sufficient cause of motor neuron injury, not of the SOD1- or
      TDP-43-driven oxidative stress seen in human ALS. The oxidative mechanism
      is itself inferred: the cited studies support it with a histological
      marker (endothelial lipopigment), case-control dietary risk factors, and
      uncontrolled improvement after pasture access, and frame it as a
      hypothesis rather than as a measured oxidative-damage readout.
    readouts:
    - name: Spinal cord capillary endothelial lipopigment accumulation
      target: Oxidative Stress
      description: >-
        Lipopigment deposition in spinal cord capillary endothelium at post
        mortem, the histological marker the authors read as oxidative injury.
      biological_processes:
      - preferred_term: response to oxidative stress
        term:
          id: GO:0006979
          label: response to oxidative stress
      direction: INCREASED
      interpretation: >-
        Present in all cases, and the basis on which the authors classify EMND as
        an oxidative disease.
      evidence:
      - reference: PMID:7988544
        reference_title: "Equine motor neuron disease: findings in 28 horses and proposal of a pathophysiological mechanism for the disease."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "lipopigment accumulation within the capillary endothelium of the spinal cord of all cases, supported the hypothesis of EMND being an oxidative disease"
        explanation: >-
          Directly reports the readout and the oxidative interpretation.
    - name: Clinical status after pasture access and vitamin E supplementation
      target: Oxidative Stress
      description: >-
        Observational rescue arm: five affected horses were followed for 9 months
        to over 2 years after onset with pasture access, two also receiving
        supplemental vitamin E.
      direction: RESTORED
      interpretation: >-
        Improvement on removal of the oxidative insult is the strongest evidence
        that the deficiency is driving the node rather than accompanying it. It
        is observational and uncontrolled, and only the more acutely affected
        horses improved.
      evidence:
      - reference: PMID:7988544
        reference_title: "Equine motor neuron disease: findings in 28 horses and proposal of a pathophysiological mechanism for the disease."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Marked clinical improvement occurred in the 4 more acutely affected horses."
        explanation: >-
          Reports the rescue observation. The arm is uncontrolled, involves five
          horses, and combines two interventions, so it supports the direction of
          the readout only weakly.
    evidence:
    - reference: PMID:9373362
      reference_title: "Intrinsic, management, and nutritional factors associated with equine motor neuron disease."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The relationship of specific nutritional factors to EMND supports the hypothesis that a deficiency of vitamin E contributes to the disease."
      explanation: >-
        Case-control epidemiology in 87 affected and 259 control horses supports
        the oxidative-stress basis of this model.
- name: TDP-43(Q331K) transgenic mouse (senescence and senolytic arm)
  species: Mouse
  genotype: TDP-43(Q331K)
  publication: PMID:42759848
  description: >
    Transgenic ALS mouse carrying the TDP-43(Q331K) allele, used to time cellular
    senescence relative to functional decline and to test whether clearing
    senescent cells alters the course. Senescence markers appear in motor cortex
    and spinal cord alongside declining neural and neuromuscular function, and
    longitudinal senolytic treatment with dasatinib and quercetin improved motor
    behaviour and neuromuscular function, reduced plasma neurofilament light chain,
    and preserved layer V neuron counts.
  evidence:
  - reference: PMID:42759848
    reference_title: "Cellular senescence is an early feature and therapeutic target in amyotrophic lateral sclerosis TDP-43 Q331K mice"
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "molecular markers of cellular senescence emerge in the motor cortex and spinal cord alongside declines in neural and neuromuscular function in TDP-43Q331K ALS mice, supporting senescence as an early feature of ALS pathology"
    explanation: >-
      Supports treating this model as informative for the senescence node: the
      markers are localized to the same regions and precede functional decline.
  modeled_mechanisms:
  - target: Cellular Senescence in Motor Cortex and Spinal Cord
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      The model is where this node's claim comes from - senescence markers in motor
      cortex and spinal cord, early relative to functional decline - and the
      senolytic arm is what makes the senescence modifiable rather than incidental.
    limitations: >-
      One allele in one species: TDP-43(Q331K) mice say nothing about senescence in
      SOD1- or C9orf72-associated ALS, and nothing about sporadic disease, which is
      the majority of human cases. The senolytic arm shows that clearing senescent
      cells changes outcomes, not which cells were cleared; cortical microglia are
      a candidate mediator inferred from reduced microglial TDP-43 burden and
      senescence markers, not a demonstrated one. Dasatinib and quercetin are given
      together, so neither agent's contribution is separable.
    readouts:
    - name: Senescence marker expression in motor cortex and spinal cord
      target: Cellular Senescence in Motor Cortex and Spinal Cord
      direction: INCREASED
      interpretation: The measurement the node rests on, in the two regions ALS degeneration affects.
      evidence:
      - reference: PMID:42759848
        reference_title: "Cellular senescence is an early feature and therapeutic target in amyotrophic lateral sclerosis TDP-43 Q331K mice"
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "molecular markers of cellular senescence emerge in the motor cortex and spinal cord alongside declines in neural and neuromuscular function in TDP-43Q331K ALS mice, supporting senescence as an early feature of ALS pathology"
        explanation: Reports the marker measurement and its anatomical location.
    - name: Plasma neurofilament light chain under senolytic treatment
      target: Cellular Senescence in Motor Cortex and Spinal Cord
      direction: DECREASED
      interpretation: >-
        Axonal damage marker falling when senescent cells are cleared, which is the
        result that makes the senescence modifiable. It reports axonal damage rather
        than senescence itself.
      evidence:
      - reference: PMID:42759848
        reference_title: "Cellular senescence is an early feature and therapeutic target in amyotrophic lateral sclerosis TDP-43 Q331K mice"
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "D&Q treatment improved motor behavior, neuromuscular function, and reduced axonal damage as measured by plasma neurofilament light chain, accompanied by robust improvements in motor cortex excitability and preservation of layer V neuron counts"
        explanation: Reports the senolytic arm's outcome measures, including the plasma NfL reduction.
differential_diagnoses:
- name: Chronic Inflammatory Demyelinating Polyradiculoneuropathy
  description: Immune-mediated demyelinating neuropathy causing progressive symmetric weakness and sensory loss; may mimic lower motor neuron-predominant ALS.
  disease_term:
    preferred_term: Chronic Inflammatory Demyelinating Polyradiculoneuropathy
    term:
      id: MONDO:0006702
      label: chronic inflammatory demyelinating polyradiculoneuropathy
  evidence:
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Some disorders that can mimic motor neuron disease are multifocal motor neuropathy with conduction block, chronic inflammatory demyelinating polyradiculoneuropathy, central nervous system tumors, multiple sclerosis, and polyradiculopathy, among others."
    explanation: StatPearls review lists CIDP among conditions that can mimic ALS and should be ruled out.
- name: Multiple Sclerosis
  description: Demyelinating disease of the central nervous system with motor weakness and spasticity that can resemble early ALS presentations.
  disease_term:
    preferred_term: multiple sclerosis
    term:
      id: MONDO:0005301
      label: multiple sclerosis
  evidence:
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Some disorders that can mimic motor neuron disease are multifocal motor neuropathy with conduction block, chronic inflammatory demyelinating polyradiculoneuropathy, central nervous system tumors, multiple sclerosis, and polyradiculopathy, among others."
    explanation: The same review identifies multiple sclerosis as a diagnostic mimic of motor neuron disease.
- name: Multifocal Motor Neuropathy
  description: Immune-mediated, asymmetric, distal motor neuropathy with conduction block that can present with focal weakness mimicking lower motor neuron ALS.
  disease_term:
    preferred_term: multifocal motor neuropathy
    term:
      id: MONDO:0018979
      label: multifocal motor neuropathy
  evidence:
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
    supports: SUPPORT
    snippet: "Some disorders that can mimic motor neuron disease are multifocal motor neuropathy with conduction block, chronic inflammatory demyelinating polyradiculoneuropathy, central nervous system tumors, multiple sclerosis, and polyradiculopathy, among others."
    explanation: StatPearls review lists multifocal motor neuropathy with conduction block as an ALS mimic that must be ruled out.
discussions:
- discussion_id: gap_als_tdp43_selective_vulnerability_and_spread
  prompt: >-
    Which TDP-43-dependent RNA-processing defect, cytoplasmic aggregate species,
    or non-cell-autonomous signal explains why upper and lower motor neurons are
    selectively vulnerable in ALS, and how does this mechanism relate to clinical
    propagation across neuroanatomical regions?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - mechanistic_hypotheses#tdp43_rna_dysregulation_selective_vulnerability_model
  - pathophysiology#TDP-43 Proteinopathy
  - pathophysiology#TDP-43-Dependent Cryptic Exon Misprocessing
  - pathophysiology#Motor Neuron Degeneration
  rationale: >-
    STMN2 and UNC13A make TDP-43 loss-of-function concrete at the RNA target
    level, but they do not yet explain why particular motor-neuron classes
    degenerate while other neurons or glia with TDP-43 pathology can be less
    affected. Separating nuclear RNA loss-of-function from cytoplasmic
    gain-of-function and spread-like propagation is required to decide whether
    therapies should prioritize restoring individual transcripts, correcting
    TDP-43 localization, clearing aggregate species, or targeting glial and
    circuit-level amplifiers.
  proposed_experiments:
  - experiment_id: exp_als_isogenic_motor_neuron_tdp43_target_rescue_panel
    name: Isogenic human motor-neuron TDP-43 target rescue and spatial validation panel
    description: >-
      Compare isogenic human iPSC-derived upper- and lower-motor-neuron-like
      cultures with controlled nuclear TDP-43 depletion, TDP-43 cytoplasmic
      mislocalization, and patient-derived TDP-43 aggregate seeding. Rescue STMN2,
      UNC13A, and candidate transcript targets singly and in combination, then
      benchmark survival, axonal regeneration, synaptic function, lysosome
      trafficking, and spatial transcriptomic signatures against ALS postmortem
      motor cortex and spinal cord.
    experiment_type:
      preferred_term: isogenic stem-cell perturbation and spatial transcriptomics experiment
    decision_criterion: >-
      A causal RNA-processing target should rescue motor-neuron survival or
      axonal/synaptic function in TDP-43-deficient cells and show spatially
      concordant misprocessing in vulnerable human ALS motor-neuron populations;
      failure of target rescue would shift priority toward aggregate-seeding,
      proteostatic, glial, or circuit-level propagation mechanisms.
  evidence:
  - reference: PMID:37999738
    reference_title: "Selective vulnerability of motor neuron types and functional groups to degeneration in amyotrophic lateral sclerosis: review of the neurobiological mechanisms and functional correlates."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Despite extensive research, it remains unclear why some motor neurons are especially susceptible to the disease, while others are affected less or even spared."
    explanation: >
      Review explicitly frames motor-neuron selective vulnerability as an
      unresolved ALS mechanism.
  - reference: PMID:32799899
    reference_title: "The role of TDP-43 mislocalization in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Yet in ALS, motor neurons selectively degenerate suggesting that the presence of TDP-43 aggregates may not necessarily drive cell-death."
    explanation: >-
      TDP-43 review highlights the unresolved gap between aggregate presence and
      selective motor-neuron death.
  - reference: PMID:35767949
    reference_title: "Loss of Stathmin-2, a hallmark of TDP-43-associated ALS, causes motor neuropathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Constitutive STMN2 loss results in early-onset sensory and motor neuropathy featuring impaired motor behavior and dramatic distal neuromuscular junction (NMJ) denervation of fast-fatigable motor units, which are selectively vulnerable in ALS, without axon or motoneuron degeneration."
    explanation: >-
      Makes the gap concrete for the best-characterized TDP-43 RNA target. Stmn2
      knockout reproduces exactly the population selectivity the gap asks about —
      the fast-fatigable motor units — yet stops short of axon or motoneuron
      degeneration, so the step from a selectively affected motor unit to
      motor-neuron death is still unaccounted for.
  - reference: PMID:39603486
    reference_title: "Two cardinal features of ALS, reduced STMN2 and pathogenic TDP-43, synergize to accelerate motor decline in mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Surprisingly, this behavioral defect is not accompanied by detectable neuropathology in the brain, spinal cord, peripheral nerves or at neuromuscular junctions (NMJs)."
    explanation: >-
      Combining partial Stmn2 loss with a TDP-43 Q331K knock-in allele
      accelerates motor decline, but the phenotype is functional and
      mitochondrial rather than degenerative, so even the two lesions together do
      not close the route to motor-neuron death that this gap identifies.
- discussion_id: gap_als_tdp43_mislocalization_upstream_trigger
  prompt: >-
    What upstream cellular event triggers preferential TDP-43 nuclear
    clearance and cytoplasmic mislocalization in motor neurons compared with
    other cell types that also express TDP-43?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#TDP-43 Proteinopathy
  - mechanistic_hypotheses#tdp43_rna_dysregulation_selective_vulnerability_model
  rationale: >-
    TDP-43 is a ubiquitously expressed nuclear RNA-binding protein, yet in ALS
    it mislocalizes and aggregates preferentially in motor neurons. The NLS and
    NES sequences of TDP-43 are not motor-neuron specific, and cellular
    stressors such as oxidative stress, osmotic stress, or heat shock can
    induce phase-separated TDP-43 cytoplasmic structures in many cell types.
    What makes motor neurons uniquely susceptible to irreversible TDP-43
    mislocalization — whether through long-axon-specific transport burdens,
    particular importin isoform expression, differential proteostatic capacity,
    or a specific upstream metabolic vulnerability — is not established.
    Identifying this upstream trigger is required to explain why ALS is a
    motor-neuron disease rather than a pan-neuronal or pan-cellular
    proteinopathy, and to determine the earliest actionable intervention point.
  evidence:
  - reference: PMID:32799899
    reference_title: "The role of TDP-43 mislocalization in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The exact mechanisms mediating the formation of TDP-43 aggregates remain elusive."
    explanation: >-
      Review acknowledges that the upstream trigger for TDP-43 aggregation
      and mislocalization is unresolved, supporting this as an open knowledge
      gap distinct from the downstream RNA-processing defects.
  - reference: PMID:37999738
    reference_title: "Selective vulnerability of motor neuron types and functional groups to degeneration in amyotrophic lateral sclerosis: review of the neurobiological mechanisms and functional correlates."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Despite extensive research, it remains unclear why some motor neurons are especially susceptible to the disease, while others are affected less or even spared."
    explanation: >-
      Selective vulnerability review frames the motor-neuron-preferential
      degeneration as unresolved, implicating upstream cell-type-specific
      factors in TDP-43 mislocalization as a key open question.
- discussion_id: gap_als_ptdp43_propagation_mechanism
  prompt: >-
    Does phosphorylated TDP-43 pathology spread through the ALS motor
    system by prion-like protein seeding, by trans-synaptic or retrograde
    axonal signaling, or by secondary neuroinflammatory relay — and can
    these mechanisms be distinguished experimentally?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#TDP-43 Proteinopathy
  - pathophysiology#Motor Neuron Degeneration
  - mechanistic_hypotheses#tdp43_rna_dysregulation_selective_vulnerability_model
  rationale: >-
    Cross-sectional postmortem staging studies show that pTDP-43 pathology
    progresses through the ALS motor system in a stereotyped, anatomically
    sequential pattern analogous to Braak staging in Parkinson disease and
    Alzheimer disease, consistent with a propagating process. However, the
    cellular mechanism of spread is not established: whether pTDP-43
    propagates by direct cell-to-cell protein seeding (prion-like templating),
    by trans-synaptic or retrograde axonal transport of a pathological signal,
    by secondary glial or neuroinflammatory relay, or by some combination of
    these mechanisms remains unresolved. Understanding the propagation
    mechanism has direct therapeutic implications — a seeding model prioritizes
    aggregate clearance or passive immunotherapy at early disease stages, while
    an inflammatory-relay model prioritizes anti-neuroinflammatory intervention
    at transitional anatomical boundaries.
  evidence:
  - reference: PMID:23686809
    reference_title: "Stages of pTDP-43 pathology in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pTDP-43 pathology in ALS possibly disseminates in a sequential pattern that permits recognition of 4 neuropathological stages consistent with the hypothesis that pTDP-43 pathology is propagated along axonal pathways."
    explanation: >-
      Postmortem staging data in 76 ALS cases support sequential anatomical
      spread of pTDP-43 pathology, motivating the mechanistic question of how
      this propagation is achieved without establishing the cellular mechanism.
  - reference: PMID:23686809
    reference_title: "Stages of pTDP-43 pathology in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whereas the cell-to-cell transmission of pTDP-43 has not been demonstrated conclusively in vivo, a recently discovered C-terminal prion-like domain has been implicated in the aggregation of pTDP-43 in cultured cells."
    explanation: >-
      In vitro prion-like domain evidence is consistent with protein seeding
      but does not establish in vivo cell-to-cell transmission, leaving the
      propagation mechanism open.
- discussion_id: mismatch_emnd_lmn_only_phenotype
  prompt: >-
    Does the lower-motor-neuron-only phenotype of equine motor neuron disease
    (EMND) preclude its use as a model for classic ALS, which requires both upper
    and lower motor neuron degeneration?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - animal_models#Horse
  rationale: >-
    Classic ALS is defined by combined upper motor neuron (UMN) and lower motor
    neuron (LMN) degeneration. Equine motor neuron disease (EMND) involves
    predominantly or exclusively lower motor neurons, with no established
    corticospinal tract involvement, making it a phenotypically closer analog to
    progressive muscular atrophy (LMN-only ALS variant) than to classic ALS.
    This reduces the direct translational value of EMND as an ALS model, though
    the shared oxidative stress mechanism and spinal motor neuron vulnerability
    retain biological relevance for the LMN degenerative arm of the disease.
  proposed_experiments:
  - experiment_id: exp_emnd_umn_tract_assessment
    name: Corticospinal tract histopathological survey in EMND horses
    description: >-
      Systematic immunohistochemical and histopathological assessment of
      corticospinal tracts and motor cortex in post-mortem EMND horses to
      determine whether subclinical UMN pathology is present but overlooked in
      existing case series, or is genuinely absent.
    experiment_type:
      preferred_term: post-mortem neuropathological study
    decision_criterion: >-
      Detection of UMN pathology would support EMND as a true ALS analog;
      confirmed absence would classify EMND as a selective LMN disease and
      redirect its value to studies of the ALS LMN degenerative arm only.
- discussion_id: mismatch_tdp43_aggregation_dispensability
  prompt: >-
    Mutant TDP-43 knock-in mice develop motor axon degeneration and motor-neuron
    death with neither nuclear TDP-43 clearance nor TDP-43 aggregates. Does that
    mean cytoplasmic aggregation and nuclear depletion are also dispensable in
    human ALS, where both are near-universal findings?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#TDP-43 Proteinopathy
  - pathophysiology#Motor Neuron Degeneration
  - mechanistic_hypotheses#canonical_motor_neuron_proteostatic_failure_model
  rationale: >-
    TDP-43 Q331K and M337V mice expressed at endogenous levels develop
    age-dependent, mutant-dependent motor axon degeneration and lower motor
    neuron death without loss of nuclear TDP-43, without aggregates, and without
    insoluble TDP-43, while showing both loss and gain of splicing function at
    selected RNA targets. Taken literally, that dissociates degeneration from the
    two features this entry treats as the defining lesion of TDP-43
    proteinopathy. The mismatch is that the finding is a sufficiency result in an
    engineered mutant model, whereas ~97% of human ALS — the great majority of it
    sporadic and not TARDBP-mutant — does show nuclear clearance and
    phosphorylated cytoplasmic inclusions. The model therefore establishes that
    an ALS-linked mutant can kill motor neurons through altered splicing alone;
    it does not establish the temporal position, toxicity, or possible protective
    role of aggregates in sporadic human disease, and it should not be read as
    demonstrating that human TDP-43 aggregation is merely a late-stage marker.
    Resolving this determines whether therapy should target aggregate clearance,
    TDP-43 localization, or the RNA-processing changes directly.
  proposed_experiments:
  - experiment_id: exp_als_aggregation_independent_tdp43_toxicity
    name: Aggregation- and localization-separated TDP-43 toxicity in human motor neurons
    description: >-
      In isogenic human iPSC-derived motor neurons, express TDP-43 variants
      engineered to separate the three features: aggregation-incompetent mutants
      that retain altered splicing, nuclear-retained mutants, and mutants that
      aggregate without changing splicing. Compare survival, axonal integrity and
      cryptic-splicing burden across arms, and benchmark the resulting splicing
      signatures against nuclear-cleared versus nuclear-preserved motor neurons
      sampled from sporadic ALS postmortem tissue.
    experiment_type:
      preferred_term: isogenic human iPSC motor-neuron structure-function dissociation experiment
    decision_criterion: >-
      Motor-neuron death in the aggregation-incompetent arm, with a splicing
      signature matching nuclear-cleared human ALS motor neurons, would extend
      the mouse result to human cells and argue that RNA misprocessing rather
      than aggregation is the actionable lesion; survival in that arm together
      with death in the aggregating arm would confine the mouse finding to
      mutant-driven disease and keep aggregate species as a human therapeutic
      target.
  evidence:
  - reference: PMID:23382207
    reference_title: ALS-linked TDP-43 mutations produce aberrant RNA splicing and adult-onset motor neuron disease without aggregation or loss of nuclear TDP-43.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Thus, adult-onset motor neuron disease does not require aggregation or loss of nuclear TDP-43, with ALS-linked mutants producing loss and gain of splicing function of selected RNA targets at an early disease stage."
    explanation: >-
      The mouse result that creates the mismatch. It shows that neither
      aggregation nor nuclear TDP-43 loss is required for adult-onset motor
      neuron disease in this engineered model, which is what makes the
      translational status of the near-universal human aggregation and nuclear
      clearance an open question rather than a settled one.
  - reference: PMID:32799899
    reference_title: "The role of TDP-43 mislocalization in amyotrophic lateral sclerosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "TDP-43 was identified as a primary component of ubiquitinated and hyper-phosphorylated cytosolic aggregates observed from post-mortem tissue of patients with ALS"
    explanation: >-
      The human side of the mismatch: postmortem ALS tissue does show
      ubiquitinated, hyperphosphorylated cytoplasmic TDP-43 aggregates, so the
      model's dispensability result conflicts with what is near-universally
      observed in patients rather than simply extending it.
- discussion_id: hyp_als_phenothiazine_autophagy_repurposing
  prompt: >-
    Can chlorpromazine, or another phenothiazine antipsychotic, be repurposed as
    a disease-modifying ALS therapy on the strength of lysosomal TPC2 agonism,
    TFEB-driven autophagy induction and enhanced TDP-43 aggregate clearance — or
    does the dopaminergic pharmacology that defines the class cancel any
    proteostatic benefit at exposures a person with ALS could tolerate?
  kind: EMERGING_HYPOTHESIS
  status: OPEN
  attaches_to:
  - pathophysiology#Impaired Autophagy
  - pathophysiology#TDP-43 Proteinopathy
  - pathophysiology#Motor Neuron Degeneration
  - treatments#
  rationale: >-
    Three independent lines converge on the phenothiazine scaffold as a
    proteostasis-directed ALS lead. An unbiased neuronal autophagy-inducer
    screen returned two phenothiazine antipsychotics as its top hits and showed
    that autophagy induction accelerates TDP-43 turnover and improves survival
    in human stem-cell-derived neurons; thioridazine cleared TDP-43 aggregates,
    restored TDP-43 splicing function and rescued locomotion in Drosophila; and
    chlorpromazine itself was shown to open the lysosomal TPC2 channel in NSC-34
    motor neurons, driving Ca2+-dependent TFEB translocation and protecting
    against the ALS/PDC neurotoxin L-BMAA, with TPC2 knockdown reverting the
    protection. Each of those is a different route to the same node this
    discussion attaches to, and none has been tested in a mammalian ALS model.

    The hypothesis is nevertheless not simply untested — it is tested by
    proxy, and the proxies failed. Methylene blue shares the tricyclic
    phenothiazine-type core, reduced TDP-43 aggregates in cells, and then
    conferred no benefit in SOD1-G93A or TDP-43-G348C mice. Pimozide, a
    neuroleptic selected by the same simple-organism screening logic, reached a
    short randomized ALS trial with apparent target engagement at the
    neuromuscular junction, and chronic dosing then worsened motor performance
    in two ALS mouse models and shortened SOD1-G93A survival. Clozapine
    delayed decline at low dose and accelerated paralysis and death at high
    dose in the same model. So the open question is not whether phenothiazines
    induce autophagy in motor neurons — they do — but whether a therapeutic
    window exists between the concentration that engages TPC2/TFEB and the
    concentration at which D2 blockade produces rigidity, sedation and
    dysphagia in a population whose leading cause of death is respiratory and
    bulbar failure.

    The epidemiological premise that originally motivated neuroleptic
    repurposing in ALS — that ALS is strikingly rare among people with
    schizophrenia — should not be carried forward. It was a clinical
    impression, and the ALS/schizophrenia genetic correlation is positive
    (14.3%), predicting a modest increase rather than a decrease in comorbidity.

    A closer look at TPC2 itself narrows the hypothesis further, and not in its
    favour. TPC2's ion selectivity is set by which ligand opens it: a
    NAADP-mimetic evokes non-selective cation currents and robust Ca2+ signals,
    a PI(3,5)P2-mimetic evokes Na+-selective currents and weaker ones, and the
    two drive lysosomal pH and exocytosis in opposite directions. The
    chlorpromazine result sits squarely on the NAADP arm — the paper benchmarks
    the chlorpromazine-evoked current against NAADP and its mimetic TPC2-A1-N,
    and blocks it with trans-Ned-19. That is the arm with no in vivo efficacy
    precedent anywhere: the lysosomal-storage rescue that put TPC2 on the map
    used the PI(3,5)P2-mimetic TPC2-A1-P throughout, including in its MLIV
    mouse, and in LRRK2 Parkinson's models the beneficial agonist was one biased
    to reduce Ca2+ permeability, with TPC2 itself the pathogenic element. So the
    chain this hypothesis proposes runs through the one mode of the one channel
    for which no animal has yet been shown to benefit.

    Two consequences for the experiments below. First, the window study should
    read out the PI(3,5)P2-biased mode as well, because if substrate clearance
    in motor neurons tracks that mode instead, the useful compound is a biased
    TPC2 agonist and not an antipsychotic. Second, the obvious alternative of
    blocking TPC2 instead — which is neuroprotective in stroke and in LRRK2
    models, and is the better-developed arm pharmacologically — carries a
    motor-neuron-specific liability that those indications do not: trans-Ned-19,
    the same antagonist, attenuates Ca2+ transients in zebrafish caudal primary
    motor neurons and inhibits their axon extension. In a motor-neuron disease
    the better-developed arm of TPC2 pharmacology acts against the arm of TPC2
    biology that motor neurons demonstrably need. See
    kb/modules/lysosomal_substrate_accumulation.yaml
    (controversy_tpc2_direction_of_modulation) for the direction question in
    general.
  proposed_experiments:
  - experiment_id: exp_als_phenothiazine_therapeutic_window_csf_exposure
    name: Phenothiazine TPC2/TFEB engagement versus tolerated CNS exposure in ALS
    description: >-
      Establish, for chlorpromazine and for the screen-derived phenothiazines
      fluphenazine and methotrimeprazine, the free concentration required in
      human iPSC-derived motor neurons to produce TPC2-dependent TFEB nuclear
      translocation and measurable TDP-43 clearance, then compare it against
      free CSF and spinal-cord concentrations achieved in wild-type and
      SOD1-G93A mice at doses below the threshold for hindlimb rigidity and
      catalepsy. Include a TPC2-null arm to confirm that clearance in motor
      neurons is channel-dependent rather than a general lysosomotropic effect
      of the cationic amphiphilic scaffold.
    experiment_type:
      preferred_term: pharmacodynamic-pharmacokinetic window study in iPSC motor neurons and mouse CNS
    decision_criterion: >-
      A viable window requires the TFEB/TDP-43-clearance EC50 to sit below the
      free CNS concentration reached at a non-cataleptic dose, with at least a
      severalfold margin. If engagement demands concentrations only reached at
      doses producing extrapyramidal signs, the repurposing hypothesis should be
      abandoned for the marketed antipsychotics and redirected to TPC2 agonists
      without dopamine-receptor affinity.
    would_support:
    - pathophysiology#Impaired Autophagy
    would_refute:
    - pathophysiology#Impaired Autophagy
    supporting_outcome:
    - >-
        TPC2-dependent TFEB translocation and TDP-43 clearance at free
        concentrations several-fold below those producing catalepsy or hindlimb
        rigidity in mice.
    refuting_outcome:
    - >-
        Engagement only at concentrations at or above the motor-toxicity
        threshold, or clearance that persists in TPC2-null motor neurons and is
        therefore an off-target lysosomotropic effect.
  - experiment_id: exp_als_chlorpromazine_dose_ranging_two_model_survival
    name: Dose-ranging chlorpromazine survival study in TDP-43 and SOD1 ALS mice
    description: >-
      Run chlorpromazine at a minimum of three doses spanning the window
      identified above in both TDP-43-A315T and SOD1-G93A mice, powered for
      survival and with prespecified neuromuscular-junction innervation,
      insoluble TDP-43, misfolded SOD1 and spinal-cord LC3-II/p62 endpoints.
      Two models and a dose range are both required: the pimozide study found
      opposite-signed effects from the short human trial, and the clozapine
      study found opposite-signed effects between low and high dose within one
      model, so a single-dose single-model result cannot settle this.
    experiment_type:
      preferred_term: dose-ranging survival study in two transgenic ALS mouse models
    decision_criterion: >-
      Chlorpromazine should extend survival or preserve neuromuscular-junction
      innervation in at least one model at a dose whose autophagic target
      engagement is confirmed in the same spinal cords. Worsened motor
      performance, shortened survival, or increased insoluble TDP-43 or
      misfolded SOD1 at any dose — the pimozide result — closes the hypothesis
      for chlorpromazine.
    would_support:
    - pathophysiology#Motor Neuron Degeneration
    would_refute:
    - pathophysiology#Motor Neuron Degeneration
    supporting_outcome:
    - >-
        Survival extension or preserved neuromuscular-junction innervation at a
        dose with confirmed spinal-cord autophagy induction.
    refuting_outcome:
    - >-
        Worsened motor performance, shortened survival, or increased insoluble
        TDP-43 or misfolded SOD1 at any tested dose.
  evidence:
  - reference: PMID:40796055
    reference_title: Lysosomal TPC2 channel as a new target of chlorpromazine and clomipramine to induce protective autophagy in L-BMAA-induced neurodegeneration.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Accordingly, TPC2 stimulation by both the drugs boosted autophagy, as revealed by the activation of autophagy initiators ULK and AMPK α and modification of LC3-II/p62(SQSTM1) ratio."
    explanation: >-
      The only chlorpromazine-specific mechanistic result in a motor-neuron
      system, and the proximate reason this hypothesis is worth stating: it
      names a molecular target (TPC2) and an effector (autophagy, read out on
      ULK, AMPK and the LC3-II/p62 ratio) rather than asserting generic
      neuroprotection. The paper reports the intervening step as a
      chlorpromazine-evoked calcium rise driving TFEB nuclear translocation.
  - reference: PMID:40796055
    reference_title: Lysosomal TPC2 channel as a new target of chlorpromazine and clomipramine to induce protective autophagy in L-BMAA-induced neurodegeneration.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Notably, siTPC2 partially reverted CMI- and CPZ-induced neuroprotection as well as that produced by NAADP."
    explanation: >-
      The knockdown arm is what distinguishes a target-mediated effect from the
      generic lysosomotropism every cationic amphiphilic drug shows, which is
      why the proposed window study keeps a TPC2-null arm. Note the authors
      report the reversion as partial, so some of the protection is not
      TPC2-attributable even here.
  - reference: PMID:24974230
    reference_title: Autophagy induction enhances TDP43 turnover and survival in neuronal ALS models.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "New compounds that stimulate autophagy improved TDP43 clearance and localization and enhanced survival in primary murine neurons and in human stem cell-derived neurons and astrocytes harboring mutant TDP43."
    explanation: >-
      Establishes the general principle the hypothesis rests on — that inducing
      neuronal autophagy clears TDP-43 and improves survival in human
      stem-cell-derived neurons. The two top compounds from this screen were
      phenothiazine antipsychotics, so the scaffold was reached by unbiased
      screening rather than by analogy alone.
  - reference: PMID:34571136
    reference_title: Thioridazine reverts the phenotype in cellular and Drosophila models of amyotrophic lateral sclerosis by enhancing TDP-43 aggregate clearance.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "thioridazine significantly improved the locomotive defect"
    explanation: >-
      The closest in vivo result for the phenothiazine class in an ALS model:
      aggregate clearance plus restored TDP-43 splicing function and improved
      locomotion in Drosophila.
  - reference: PMID:34571136
    reference_title: Thioridazine reverts the phenotype in cellular and Drosophila models of amyotrophic lateral sclerosis by enhancing TDP-43 aggregate clearance.
    supports: REFUTE
    evidence_source: IN_VITRO
    snippet: "We observed that the degradation of the aggregates occurs independent of the autophagy pathway beyond autophagosome-lysosome fusion, but requires a functional proteasome pathway."
    explanation: >-
      Refutes the specific claim that the phenothiazine class works on TDP-43
      through the autophagy route the chlorpromazine/TPC2 result proposes. In
      this system clearance was proteasome-dependent and autophagy-independent,
      so the two strongest class results do not currently describe one
      mechanism, and a shared-mechanism reading of the class is not supported.
  - reference: PMID:29790082
    reference_title: Chronic Administration of Pimozide Fails to Attenuate Motor and Pathological Deficits in Two Mouse Models of Amyotrophic Lateral Sclerosis.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "Chronic administration of pimozide exacerbated motor performances in both animal models and reduced survival in SOD1G93A mice."
    explanation: >-
      The strongest single argument against the hypothesis. A neuroleptic that
      had already produced apparent target engagement in a short human ALS trial
      caused active harm under chronic dosing in both standard ALS mouse
      models, which is why the proposed mouse experiment is dose-ranging and
      powered for survival rather than confirmatory.
  - reference: PMID:29790082
    reference_title: Chronic Administration of Pimozide Fails to Attenuate Motor and Pathological Deficits in Two Mouse Models of Amyotrophic Lateral Sclerosis.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "In TDP-43A315T, it decreased the percentage of innervated neuromuscular junctions (NMJs) and increased the accumulation of insoluble TDP-43."
    explanation: >-
      Directly opposes the proteostatic rationale: chronic neuroleptic exposure
      increased rather than reduced insoluble TDP-43 in vivo, the opposite of
      what the cellular aggregate-clearance results predict.
  - reference: PMID:14598305
    reference_title: Opposing effects of low and high-dose clozapine on survival of transgenic amyotrophic lateral sclerosis mice.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "Low-dose treatment was associated with delayed locomotor impairment and death, compared to high-dose clozapine, which accelerated paralysis and mortality (P < 0.05)."
    explanation: >-
      Establishes that the dose-response for an antipsychotic in SOD1-G93A mice
      is biphasic and changes sign, so any single-dose result for chlorpromazine
      would be uninterpretable. This is the reason the therapeutic-window
      question, not the mechanism question, is the decisive one.
  - reference: PMID:14598305
    reference_title: Opposing effects of low and high-dose clozapine on survival of transgenic amyotrophic lateral sclerosis mice.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "High-dose clozapine, however, produced extrapyramidal symptoms in mice manifest by hindlimb rigidity, despite reducing spinal cord p75(NTR) levels overall."
    explanation: >-
      Names the mechanism by which the window closes — dopaminergic blockade
      produces a motor phenotype in the same animals in which the putatively
      protective target was engaged. Target engagement and motor harm coexisted.
  - reference: PMID:22230045
    reference_title: Methylene blue administration fails to confer neuroprotection in two amyotrophic lateral sclerosis mouse models.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "Despite its established neuroprotective properties, MB failed to confer protection in both mouse models of ALS."
    explanation: >-
      The class precedent for exactly this in-vitro-to-in-vivo gap. Methylene
      blue shares the tricyclic core, reduced TDP-43 aggregation in cells, and
      then did nothing in SOD1-G93A or TDP-43-G348C mice.
  - reference: PMID:19560462
    reference_title: Methylene blue and dimebon inhibit aggregation of TDP-43 in cellular models.
    supports: NO_EVIDENCE
    evidence_source: IN_VITRO
    snippet: "The results indicate that MB and dimebon may be useful for the treatment of ALS, FTLD-U and other TDP-43 proteinopathies."
    explanation: >-
      Cited for the pattern rather than the claim. This is the cellular
      TDP-43-clearance result that licensed the methylene blue mouse studies,
      phrased almost identically to the present hypothesis, three years before
      those studies found no effect. It calibrates how much weight a cellular
      aggregate-clearance result carries on its own.
  - reference: PMID:33663349
    reference_title: "Phenothiazine as novel human superoxide dismutase modulators: discovery, optimization, and biological evaluation."
    supports: REFUTE
    directness: INDIRECT
    evidence_source: IN_VITRO
    snippet: "Compared with the normal blood SOD1 activity, the percent of O2 production increased with trifluoperazine, while it decreased with the chlorpromazine."
    explanation: >-
      Argues against chlorpromazine specifically rather than against the class:
      within the same scaffold, chlorpromazine inhibited SOD1 enzymatic activity
      where trifluoperazine activated it. Relevance is indirect, since
      SOD1-linked ALS is driven by misfolding gain-of-function rather than by
      loss of dismutase activity, but it is a reason to prefer another
      phenothiazine if the class is pursued.
  - reference: PMID:28322246
    reference_title: Genetic correlation between amyotrophic lateral sclerosis and schizophrenia.
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "A modest increase in comorbidity of ALS and schizophrenia is expected given these findings (odds ratio 1.08-1.26) but this would require very large studies to observe epidemiologically."
    explanation: >-
      Removes the epidemiological premise that motivated neuroleptic
      repurposing in ALS. The expected direction of ALS/schizophrenia
      comorbidity is a modest increase, not the near-absence that the original
      proposal treated as evidence of drug-conferred protection.
  - reference: PMID:17475413
    reference_title: "Does treating schizophrenia reduce the chances of developing amyotrophic lateral sclerosis?"
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: "We propose that the use of neuroleptics and some antidepressants, which are chronically prescribed to schizophrenics and which have neuroprotective properties and some of which promote neurogenesis, may confer protection against this deadly neurodegenerative disease ALS."
    explanation: >-
      The origin of the repurposing idea, recorded as the hypothesis it was.
      Graded OTHER and marked REVIEW_SYNTHESIS because the paper is a
      hypothesis article whose premise is an uncontrolled clinical impression at
      ALS centres, not a measured association.
  - reference: PMID:29023321
    reference_title: "Antipsychotic medication and oropharyngeal dysphagia: systematic review."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Although few general conclusions can be drawn from current evidence, both typical and atypical antipsychotics can be associated with OD."
    explanation: >-
      The clinical-tolerability arm of the window problem. Oropharyngeal
      dysphagia is a class effect of antipsychotics and is also the ALS
      complication that drives aspiration and gastrostomy, so the adverse-effect
      profile overlaps the disease's own trajectory rather than being
      independent of it.
  - reference: PMID:32167471
    reference_title: Agonist-mediated switching of ion selectivity in TPC2 differentially promotes lysosomal function.
    supports: REFUTE
    evidence_source: IN_VITRO
    snippet: "One of these evoked robust Ca2+-signals and non-selective cation currents, the other weaker Ca2+-signals and Na+-selective currents."
    explanation: >-
      Refutes the implicit premise that "activating TPC2" is one intervention.
      The chlorpromazine result is benchmarked against NAADP and TPC2-A1-N, so
      it is the Ca2+-permeable mode — while the lysosomal-storage rescue and the
      LRRK2 correction both sit on the other mode. The hypothesis therefore
      cannot borrow their in vivo support.
  - reference: PMID:40279672
    reference_title: "Lysosomal TPC2 channels disrupt Ca2+ entry and dopaminergic function in models of LRRK2-Parkinson's disease."
    supports: REFUTE
    directness: INDIRECT
    evidence_source: MODEL_ORGANISM
    snippet: "Reducing Ca2+ permeability with a novel biased TPC2 agonist corrected deviant Ca2+ entry and behavioral defects."
    explanation: >-
      In a neurodegeneration model with an in vivo readout, benefit came from
      moving TPC2 selectivity away from Ca2+ — the opposite direction to the
      chlorpromazine mechanism — in a study where TPC2 activity was itself
      pathogenic. Relevant rather than decisive, since LRRK2 Parkinson's is not
      ALS, but it is the closest in vivo test of the direction this hypothesis
      needs.
  - reference: PMID:32546534
    reference_title: TPC2-mediated Ca(2+) signaling is required for axon extension in caudal primary motor neurons in zebrafish embryos.
    supports: REFUTE
    directness: INDIRECT
    evidence_source: MODEL_ORGANISM
    snippet: "showed that these treatments attenuated CaP Ca2+ signaling and inhibited axon extension"
    explanation: >-
      Closes the obvious escape route rather than the hypothesis itself. If the
      Ca2+-permeable mode is the wrong direction, the natural move is to block
      TPC2 as in stroke and LRRK2 models — but trans-Ned-19, that same
      antagonist, inhibits motor axon extension here. Both directions carry a
      motor-neuron-specific cost, which is why the window study is the right
      first experiment rather than a switch of sign.

notes: >
  Subtype scope. `has_subtypes` carries two axes. The four clinical rows
  (familial/sporadic, bulbar/limb onset) describe how ALS presents; the
  gene-defined rows below them are the MONDO numbered loci that descend from
  MONDO:0004976 via MONDO:0005144 "familial amyotrophic lateral sclerosis". The
  ALS and FTDALS numbering is MONDO's and OMIM's, taken from each term's own
  label and OMIM cross-reference rather than reconstructed; MONDO:0027694,
  MONDO:0030875, MONDO:0030885 and MONDO:0957538 carry no MONDO textual
  definition, so for those four the gene attribution rests entirely on the cited
  primary reports.

  Genes deliberately without a subtype row here. SOD1 (ALS1, MONDO:0007103) is
  curated as the separate entry Amyotrophic_Lateral_Sclerosis_Type_1 and is not
  duplicated. CHCHD10 (FTDALS2) likewise has its own entry. The 16 ClinGen-graded
  genes in the `genetic:` section below (ARHGEF28, ARPP21, CAV1, CAV2, CFAP410,
  DCTN1, DNAJC7, GLE1, GLT8D1, LGALSL, NEFH, NUP50, PRPH, SPTLC2, SS18L1, TAF15)
  have no numbered MONDO locus term and remain gene records rather than subtype
  rows.

  Contested subtypes. ALS26 (TIA1) and ALS28 (LRP12) are recorded with the
  published counter-evidence rather than as settled: the Project MinE consortium
  argues TIA1 causality is unproven, and LRP12 CGG expansions have not been found
  in ALS patients of European ancestry. Their `genetic:` records are graded
  DISPUTED and CAUSATIVE-with-caveat respectively, and both carry the contrary
  report as its own evidence item. No ClinGen gene-disease validity classification
  is cited for any of the 18 genes enumerated here; the ClinGen-derived records
  elsewhere in this entry cover a different, non-overlapping set of genes.

references:
- reference: PMID:20301623
  title: "Amyotrophic Lateral Sclerosis Overview."
  tags:
  - GeneReviews
- reference: PMID:20301761
  title: "TARDBP-Related Amyotrophic Lateral Sclerosis-Frontotemporal Dementia."
  tags:
  - GeneReviews
- reference: PMID:25577942
  title: "C9orf72 Frontotemporal Dementia and/or Amyotrophic Lateral Sclerosis."
  tags:
  - GeneReviews
- reference: PMID:33085325
  title: "Electrodiagnostic Evaluation of Motor Neuron Disease (Archived)."
  tags:
  - StatPearls
- reference: PMID:42541567
  title: "Targeting TDP-43 in sporadic amyotrophic lateral sclerosis."

📚

References & Deep Research

References

PMID:20301623

Amyotrophic Lateral Sclerosis Overview.

No top-level findings curated for this source.

PMID:20301761

TARDBP-Related Amyotrophic Lateral Sclerosis-Frontotemporal Dementia.

No top-level findings curated for this source.

PMID:25577942

C9orf72 Frontotemporal Dementia and/or Amyotrophic Lateral Sclerosis.

No top-level findings curated for this source.

PMID:33085325

Electrodiagnostic Evaluation of Motor Neuron Disease (Archived).

No top-level findings curated for this source.

PMID:42541567

Targeting TDP-43 in sporadic amyotrophic lateral sclerosis.

No top-level findings curated for this source.

Deep Research

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (1)

Update Amyotrophic Lateral Sclerosis: ATXN2, AMX0035 (withdrawn), structured prevalence · 2026-07-09T13:12:53Z · View source

Up-to-date curation pass on the existing mature ALS entry. (1) Added ATXN2 intermediate-length polyQ repeat expansion as a Susceptibility genetic entry (hgnc:10555) citing Elden et al. 2010 Nature (PMID:20740007). (2) Added sodium phenylbutyrate-taurursodiol / AMX0035 (Relyvrio/Albrioza) treatment with CENTAUR SUPPORT (PMID:32877582) plus PHOENIX-failure and 2024 market-withdrawal REFUTE evidence (PMID:38909349), documenting a withdrawn ALS therapy. (3) Added a structured prevalence block (European point prevalence and annual incidence, class BAND_1_9_PER_100000) from ORPHA:803. Ran claude_code deep-research, which confirmed all three additions and existing content. Fixed a local environment issue (venv was Python 3.14, breaking pyhornedowl/oaklib; recreated on Python 3.13). Validated with 'just validate' (schema+terms+references all pass); compliance 96.2%.

Claude Code ▸

1. Disease Information

claude-haiku-4-5-20251001, claude-opus-4-8[1m] 12 citations 2026-07-09T16:06:31.461403

1. Disease Information

Overview. Amyotrophic lateral sclerosis (ALS), also called motor neuron disease (MND) in the UK/Commonwealth and "Lou Gehrig's disease" in the US, and maladie de Charcot in France, is a progressive, fatal neurodegenerative disorder characterized by the combined degeneration of upper motor neurons (UMN; Betz cells of the primary motor cortex and the corticospinal tracts) and lower motor neurons (LMN; anterior horn cells of the spinal cord and brainstem motor nuclei). The result is progressive muscle weakness, atrophy, spasticity, and ultimately paralysis, with death most commonly from neuromuscular respiratory failure, typically 2–4 years after symptom onset. ALS exists on a clinical–pathological continuum with frontotemporal dementia (FTD); up to ~50% of patients have some cognitive/behavioral impairment and ~13–15% meet criteria for concomitant FTD (Brown & Al-Chalabi, N Engl J Med 2017, PMID:28700839; van Es et al., Lancet 2017 seminar, PMID:28552366; Feldman et al., Lancet 2022, PMID:36116464).

Key identifiers. - MONDO: MONDO:0004976 (amyotrophic lateral sclerosis); locus-specific children include MONDO:0007103 (ALS1, SOD1). - OMIM: #105400 (ALS1, SOD1); phenotypic series PS105400 enumerates ALS1–ALS26+ loci. C9orf72 ALS-FTD = #105550 (FTDALS1). - Orphanet: ORPHA:803 (amyotrophic lateral sclerosis). - ICD-10: G12.21. ICD-11: 8B60.0. - MeSH: D000690 (Amyotrophic Lateral Sclerosis); tree under "Motor Neuron Disease" (D016472). - UMLS/SNOMED CT: 86044005 (Amyotrophic lateral sclerosis).

Synonyms / alternative names. Motor neuron disease (MND); Lou Gehrig's disease; Charcot disease; classic/classical ALS. Related MND phenotypes that some classifications group with ALS: primary lateral sclerosis (PLS) (pure UMN), progressive muscular atrophy (PMA) (pure LMN), progressive bulbar palsy (PBP) (bulbar-onset), and the ALS-FTD spectrum.

Data provenance. The KB entry should be built from aggregated disease-level resources (OMIM, Orphanet, HPO, systematic reviews, natural-history registries such as PRO-ACT, and society guidelines), not individual EHR/patient records. Genetic frequencies are drawn from familial cohorts and population databases (gnomAD, Project MinE).

2. Etiology

ALS is etiologically heterogeneous. ~90% of cases are sporadic (sALS); ~10% are familial (fALS), usually autosomal dominant. Even sporadic ALS has a substantial genetic contribution (twin-study heritability ~0.4–0.6) and is best modeled as a gene–environment, multistep process (Al-Chalabi et al., Lancet Neurol 2014 multistep model, PMID:24507800 — estimated a six-step process).

Primary causal factors. - Genetic (monogenic and oligogenic). Four genes dominate: C9orf72, SOD1, TARDBP, FUS. Together they explain up to ~60–70% of fALS and ~10% of sALS in European populations (see §4). C9orf72 hexanucleotide expansion is the single most common cause overall. - Convergent molecular mechanism. Regardless of trigger, >97% of ALS cases share cytoplasmic TDP-43 (TARDBP) mislocalization and aggregation as the pathological signature; the principal exceptions are SOD1- and FUS-mutant cases, which have SOD1- or FUS-positive/TDP-43-negative inclusions (Neumann et al., Science 2006, PMID:17023659 — identified TDP-43 as the ubiquitinated inclusion protein).

Risk factors.

Genetic risk / susceptibility. - C9orf72 G4C2 repeat expansion (>~30 repeats pathogenic; intermediate alleles debated) — largest single genetic risk factor; incomplete, age-dependent penetrance. - ATXN2 intermediate-length polyQ repeats (~27–33 CAG) — validated risk factor for sporadic ALS (Elden et al., Nature 2010, PMID:20740007). - SOD1, TARDBP, FUS rare variants (see §4). UNC13A polymorphisms modify risk and survival. - Rare-variant burden in TBK1, NEK1, KIF5A, C21orf2, OPTN, VCP, UBQLN2, CHCHD10, MATR3, PFN1, ANXA11, TIA1, SQSTM1, TUBA4A.

Environmental / demographic risk. - Age (peak onset 55–75) and male sex (M:F ~1.3–1.5:1, converging after menopause). - Family history of ALS/FTD. - Cigarette smoking — the most consistently replicated exogenous risk factor (probable causal; especially in women). - Physical activity / elite athleticism & professional sport (e.g., Italian football, US football) and military service — associated in multiple cohorts, though confounding and reverse-causation debated. - Occupational/environmental exposures: heavy metals (lead), pesticides/agrochemicals, electromagnetic fields, formaldehyde — associations of variable strength. - β-methylamino-L-alanine (BMAA), a cyanobacterial neurotoxin, implicated in the Western Pacific ALS–Parkinsonism–dementia complex (Guam ALS-PDC) (Cox et al. hypothesis; contested).

Protective factors. - Higher BMI / hyperlipidemia are consistently associated with lower risk and better survival (a metabolic-reserve effect) — one of the most robust epidemiological signals. - Type 2 diabetes associated with reduced ALS risk in European populations (opposite in Asian populations). - Genetic protective/modifier alleles remain an active area; no well-established protective coding variant analogous to APOE exists.

Gene–environment interaction. The multistep model implies that inherited variants "use up" one or more of the ~6 steps, so mutation carriers require fewer environmental hits and present earlier — e.g., C9orf72 carriers show a lower estimated step number than sporadic patients (Al-Chalabi et al., PMID:24507800; Vucic et al. multistep replication studies).

3. Phenotypes

ALS phenotypes span motor (UMN + LMN), bulbar, respiratory, cognitive/behavioral, and constitutional domains. Suggested HPO terms (verify labels with OAK before KB entry):

Phenotype	Domain	Typical frequency	Suggested HPO
Progressive muscle weakness	LMN/UMN	Universal (obligate)	HP:0003323 (Progressive muscle weakness)
Skeletal muscle atrophy / amyotrophy	LMN	Very frequent	HP:0003202 (Skeletal muscle atrophy)
Fasciculations	LMN	Very frequent	HP:0002380 (Fasciculations)
Muscle cramps	LMN	Frequent (early)	HP:0003394 (Muscle cramps)
Spasticity	UMN	Frequent	HP:0001257 (Spasticity)
Hyperreflexia	UMN	Frequent	HP:0001347 (Hyperreflexia)
Dysarthria	Bulbar UMN/LMN	Frequent	HP:0001260 (Dysarthria)
Dysphagia	Bulbar	Frequent	HP:0002015 (Dysphagia)
Sialorrhea / drooling	Bulbar	Frequent	HP:0002307 (Drooling)
Tongue atrophy & fasciculations	Bulbar LMN	Frequent	HP:0000167 (region) / fasciculation term
Respiratory insufficiency / failure	Respiratory	Terminal (cause of death)	HP:0002093 / HP:0002878 (Respiratory failure)
Dyspnea, orthopnea	Respiratory	Frequent (late)	HP:0002094 (Dyspnea)
Weight loss / hypermetabolism	Constitutional	Frequent	HP:0001824 (Weight loss)
Pseudobulbar affect (emotional lability)	Behavioral	~20–50%	HP:0000749 (Emotional lability)
Frontotemporal dementia	Cognitive	~13–15%	HP:0002145 (Frontotemporal dementia)
Executive/behavioral cognitive impairment (sub-FTD)	Cognitive	Up to ~50%	HP:0100543 (Cognitive impairment)
Preserved sensation / oculomotor / sphincter (typical sparing)	—	Characteristic	(document as negative features)

Onset topography. ~⅔ spinal (limb) onset (asymmetric distal limb weakness — foot drop, hand clumsiness/split-hand), ~⅓ bulbar onset (dysarthria/dysphagia; more common in older women, worse prognosis), and a minority respiratory-onset (worst prognosis). "Flail arm" (Vulpian-Bernhardt) and "flail leg" variants and PLS/PMA represent phenotypic extremes.

Characteristics. Adult onset (median ~58–63 y; earlier in fALS, especially SOD1/FUS which can be juvenile). Course is relentlessly progressive with contiguous anatomical spread from the onset region. Severity variable but uniformly disabling.

Quality-of-life impact. Progressive loss of ambulation → wheelchair dependence; loss of speech → augmentative/alternative communication; loss of swallow → gastrostomy dependence and aspiration risk; respiratory decline → ventilatory dependence; retained cognition in most patients means awareness of decline (high depression/existential distress). Measured with ALSFRS-R (function), ALSAQ-40/ALSAQ-5 (disease-specific QoL), and generic EQ-5D/SF-36.

4. Genetic / Molecular Information

Causal genes (the "big four" + long tail; OMIM phenotypic series PS105400).

Gene	HGNC	ALS locus / OMIM	% fALS	% sALS	Inheritance	Dominant mechanism
C9orf72	hgnc:28337	FTDALS1 #105550	~30–40%	~5–7%	AD	GGGGCC intronic expansion; RNA foci + DPR (RAN translation) + haploinsufficiency (GoF+LoF)
SOD1	hgnc:11179	ALS1 #105400	~12–20%	~1–2%	AD (rare AR, e.g., D90A)	Misfolded-protein toxic gain of function
TARDBP (TDP-43)	hgnc:11571	ALS10 #612069	~4–5%	~1%	AD	RNA-binding dysfunction; aggregation
FUS	hgnc:4010	ALS6 #608030	~4%	~1%	AD (juvenile)	RNA/DNA-binding; cytoplasmic aggregation
TBK1	hgnc:11584	ALS/FTD	~1–2%	—	AD	Haploinsufficiency; autophagy/inflammation
KIF5A	hgnc:6323	ALS25	~1%	—	AD	Splice/C-terminal; axonal transport
NEK1, C21orf2, OPTN, VCP, UBQLN2, CHCHD10, MATR3, PFN1, ANXA11, TIA1, SQSTM1, TUBA4A, DCTN1, SETX, ALS2, SPG11, FIG4	—	ALS2–ALS26	rare	rare	AD/AR/XL	Autophagy, proteostasis, cytoskeleton, mitochondria, RNA metabolism

Landmark gene-discovery citations: - SOD1 — Rosen et al., Nature 1993 (first ALS gene), PMID:8446170. - TARDBP/TDP-43 mutations — Sreedharan et al., Science 2008, PMID:18309045. - FUS — Kwiatkowski et al., Science 2009, PMID:19251627; Vance et al., Science 2009, PMID:19251628. - C9orf72 G4C2 expansion — DeJesus-Hernandez et al., Neuron 2011, PMID:21944778; Renton et al., Neuron 2011, PMID:21944779. - UBQLN2 (X-linked) — Deng et al., Nature 2011, PMID:21857683. - TBK1 — Freischmidt et al., Nat Neurosci 2015, PMID:26192745. - KIF5A — Nicolas et al., Neuron 2018, PMID:29566793.

Pathogenic variants — classification & type. - SOD1: >180 mostly missense variants (e.g., p.Ala5Val/A4V — aggressive, N. American; p.Asp91Ala/D90A — often recessive, slowly progressive, Scandinavian; p.Gly94Ala/G93A — the canonical mouse model allele). ACMG classification: many pathogenic/likely pathogenic in ClinVar. Mechanism = toxic gain of function (misfolding), not loss of dismutase activity. - C9orf72: noncoding GGGGCC hexanucleotide repeat expansion in intron 1 (normal <~24; pathogenic hundreds–thousands). Repeat-primed PCR / Southern blot required (not standard NGS). - TARDBP/FUS: predominantly missense clustered in the glycine-rich/low-complexity C-terminal domain (TDP-43) and the C-terminal NLS/RGG region (FUS). - KIF5A: loss-of-splice-site / C-terminal variants.

Allele frequency / somatic vs germline. ALS variants are germline; SOD1/TARDBP/FUS pathogenic alleles are essentially absent/ultra-rare in gnomAD controls, consistent with pathogenicity. C9orf72 expansions are not captured by standard population SNV databases. Somatic mosaicism is described (e.g., FUS) but rare.

Modifier genes. ATXN2 intermediate repeats (risk + earlier onset; PMID:20740007); UNC13A (survival/cognition modifier and a cryptic-exon target of TDP-43 loss); EPHA4 (survival); KIFAP3, CAMTA1 (reported modifiers).

Epigenetics. C9orf72 promoter/repeat hypermethylation can reduce expression and modestly protect; global and locus-specific DNA-methylation changes and histone modifications at C9orf72 reported (search ENCODE/Roadmap; DiseaseMeth). Epigenetic DNA methylation "clocks" show accelerated biological aging in ALS.

Chromosomal abnormalities. The C9orf72 repeat maps to chromosome 9p21; ALS is otherwise not a large-CNV/aneuploidy disorder. Large structural variants are rare contributors.

5. Environmental Information

Toxins / occupational exposures (search CTD): lead and other heavy metals, pesticides/organochlorines, agrochemicals, solvents/formaldehyde, and cyanotoxin BMAA (CHEBI candidate; Guam ALS-PDC). Electromagnetic-field/electric-shock exposure hypothesized.
Lifestyle: cigarette smoking (probable causal risk); vigorous/high-level physical activity and contact/professional sport; military deployment (Gulf War veterans). High premorbid BMI/lipids protective (§2).
Infectious agents: No established infectious cause. Human endogenous retrovirus HERV-K (HML-2) reactivation has been proposed as a mechanistic contributor (TDP-43 can transactivate HERV-K), motivating antiretroviral trials (e.g., Triumeq/Lighthouse); enteroviral hypotheses unconfirmed. This is best curated as a hypothesis/knowledge-gap, not established etiology.

6. Mechanism / Pathophysiology

ALS is a convergent, multi-mechanism motor-neuron proteinopathy. The dominant unifying lesion is nuclear clearance and cytoplasmic aggregation of TDP-43, causing both loss of nuclear RNA-processing function and cytoplasmic gain of toxicity (Neumann et al., PMID:17023659; reviews Taylor, Brown & Ravits, Nature 2016 "Decoding ALS," PMID:27830784).

Causal chain (upstream → downstream), with GO/CL suggestions:

Genetic/environmental trigger (mutation, aging, oxidative burden) →
RNA-metabolism dysregulation & TDP-43/FUS mislocalization — impaired splicing, mRNA transport, stress-granule dynamics; loss of TDP-43 nuclear function → cryptic-exon inclusion (e.g., in STMN2 and UNC13A), a key emerging mechanism.
GO:0008380 (RNA splicing); GO:0006406 (mRNA export from nucleus); GO:0010494 (cytoplasmic stress granule); GO:0006913 (nucleocytoplasmic transport).
Proteostasis failure & protein aggregation — misfolded SOD1, TDP-43, FUS, DPR aggregates; impaired autophagy and ubiquitin–proteasome clearance (OPTN, SQSTM1, UBQLN2, VCP, TBK1 converge here).
GO:0006914 (autophagy); GO:0000045 (autophagosome assembly); GO:0043161 (proteasome-mediated ubiquitin-dependent protein catabolic process); GO:0031625 (ubiquitin protein ligase binding).
Nucleocytoplasmic transport defects — C9orf72 DPRs (esp. arginine-rich poly-GR/PR) disrupt the nuclear pore.
C9orf72-specific triad: (a) RNA foci sequestering RNA-binding proteins; (b) RAN-translated dipeptide repeat proteins (poly-GA, -GP, -GR, -PR, -PA) that are toxic (Mori et al., Science 2013, PMID:23393093; Ash et al., Neuron 2013, PMID:23415312); (c) C9orf72 haploinsufficiency impairing autophagy/immune function.
Glutamate excitotoxicity — deficient astrocytic EAAT2/GLT-1 glutamate uptake → excess synaptic glutamate → Ca²⁺-mediated excitotoxic motor-neuron injury (the rationale for riluzole).
GO:0051966 (regulation of glutamatergic synaptic transmission); CHEBI:14321 (glutamate); CHEBI:29108 (calcium).
Mitochondrial dysfunction & oxidative stress — impaired bioenergetics, ROS; SOD1 links directly (though toxicity is misfolding-driven, not enzyme loss).
GO:0006979 (response to oxidative stress); GO:0004784 (superoxide dismutase activity); CHEBI:18421 (superoxide); CHEBI:16240 (hydrogen peroxide).
Axonal transport & cytoskeletal defects — KIF5A, DCTN1, PFN1, TUBA4A, NEFH; distal ("dying-back") axonopathy and neuromuscular-junction denervation as an early event.
Non–cell-autonomous neuroinflammation — reactive astrocytes and microglia drive progression; mutant SOD1 in glia accelerates disease independent of neuronal SOD1 (Boillée et al., Science 2006, microglial contribution, PMID:16741123).
GO:0150076 (neuroinflammatory response); GO:0006954 (inflammatory response); CL:0000129 (microglial cell); CL:0000127 (astrocyte).
Motor-neuron degeneration & apoptosis → denervation → muscle atrophy/paralysis → respiratory failure.
- GO:0043065 (positive regulation of apoptotic process); CL:0000100 (motor neuron); CL:0011001 (spinal cord motor neuron); CL:0000598 (pyramidal neuron, for corticomotoneurons).

Prion-like spread. Misfolded SOD1 and TDP-43 propagate template-directed misfolding cell-to-cell, consistent with the clinically observed contiguous anatomical spread from the onset focus.

Protein dysfunction detail. SOD1 = destabilized/misfolded metalloenzyme (Cu/Zn) forming toxic oligomers (UniProt P00441). TDP-43 (UniProt Q13148) and FUS (UniProt P35637) are RNA/DNA-binding proteins with low-complexity/prion-like domains that drive aberrant liquid–liquid phase separation into pathological solid aggregates.

Molecular profiling. Transcriptomics of ALS motor cortex/spinal cord (GEO datasets) show splicing dysregulation and cryptic exons; single-nucleus RNA-seq reveals selective vulnerability and glial activation states; CSF/plasma neurofilament (NfL, pNfH) is the leading fluid proteomic biomarker (see §10). CRISPR functional-genomics screens (DepMap-style, and DPR-toxicity screens) implicate nucleocytoplasmic-transport and ER-stress modifiers.

7. Anatomical Structures Affected

Organ / system level. Primary target = the motor system of the central and peripheral nervous system. - Primary motor cortex / precentral gyrus (Betz cells) — UBERON:0001384 (primary motor cortex); UBERON:0002026 (precentral gyrus). - Corticospinal (pyramidal) tract / lateral corticospinal tract — UBERON:0002718 (lateral corticospinal tract). - Spinal cord anterior (ventral) horn — UBERON:0002240 (spinal cord); ventral/anterior horn gray matter. - Brainstem motor nuclei (hypoglossal, facial, trigeminal motor) — bulbar involvement. - Frontotemporal cortex — in ALS-FTD (UBERON:0001870 frontal cortex; UBERON:0001871 temporal lobe). - Secondary: skeletal muscle (denervation atrophy; UBERON:0001134 skeletal muscle tissue), diaphragm (UBERON:0001103) → respiratory system; downstream complications in respiratory and GI (aspiration) systems.

Characteristically spared (important negative features for KB): extraocular muscles/oculomotor neurons, Onuf's nucleus (sphincter/continence), sensory pathways, and autonomic function — usually preserved until very late.

Tissue / cell level. - Lower motor neurons — CL:0011001 (spinal cord motor neuron); CL:0000100 (motor neuron). - Upper motor neurons / Betz cells (corticomotoneurons) — CL:0000598 (pyramidal neuron). - Astrocytes — CL:0000127; microglia — CL:0000129; oligodendrocytes — CL:0000128 (contribute to non-cell-autonomous injury). - Skeletal muscle fiber — CL:0000188 (denervated).

Subcellular level (GO cellular component). Cytoplasmic inclusions (GO:0005737 cytoplasm); stress granules (GO:0010494); nucleus/nuclear clearance of TDP-43 (GO:0005634); mitochondrion (GO:0005739); neuromuscular junction (GO:0031594); nuclear pore/envelope (GO:0005643).

Localization / lateralization. Onset is characteristically focal and asymmetric (one limb), with contiguous ipsilateral and contralateral spread; the split-hand sign (preferential thenar/first-dorsal-interosseous wasting) is a recognized focal LMN pattern.

8. Temporal Development

Onset. Adult, typically 55–75 y (median ~58–63); insidious, focal, painless weakness. Juvenile/early-onset forms occur with FUS, SOD1, ALS2, SETX, SPG11.

Progression & staging. Relentlessly progressive; rate is variable but individually near-linear on ALSFRS-R. Two validated clinical staging systems: - King's staging (anatomical spread: stages 1–4A/4B by number of regions involved + gastrostomy/NIV milestones) — Roche et al., Brain 2012, PMID:22042175. - MiToS staging (functional loss across 4 domains) — Chiò et al., 2015.

Rate / course. Median survival ~2–4 years from symptom onset (from diagnosis shorter). Course is progressive, non-remitting (no relapsing-remitting phase; spontaneous remission essentially unknown/"reversal" cases extraordinarily rare and debated).

Prognostic tempo determinants (see §11): bulbar/respiratory onset, older age, short diagnostic delay (fast progression), FTD, low FVC, high ΔALSFRS-R slope, low BMI → faster. PLS and flail-limb variants, SOD1-D90A, and young onset → slower (survival can be many years to decades).

Critical intervention windows. Early NfL-guided and genetically-guided treatment initiation (tofersen data suggest earlier = better). Presymptomatic intervention is now being tested (ATLAS trial: tofersen in presymptomatic SOD1 carriers with rising NfL).

9. Inheritance and Population

Epidemiology. - Incidence: ~1.5–2.7 per 100,000 person-years in European-ancestry populations (Europe age-standardized ~1.0–2.6/100,000/yr); lower reported rates in East Asian and admixed populations. US age-adjusted incidence ~1.5–1.7/100,000 (recent CDC/registry data). - Prevalence: ~4.5–9 per 100,000; a 2023 systematic review/model projects global prevalence rising substantially by 2040 with population aging (Global prevalence & incidence systematic review, Neurology 2023 — see PMC10424837 / DOI 10.1212/WNL.0000000000207474). Registry-based projections (Italy) estimate prevalence ~11.7/100,000 in 2024 rising toward ~15.7/100,000 by 2040. - Lifetime risk ~1 in 300–400.

Inheritance & genetic-counseling parameters. - Pattern: Predominantly autosomal dominant in fALS (SOD1, C9orf72, TARDBP, FUS, TBK1, KIF5A); X-linked (UBQLN2); autosomal recessive (some SOD1-D90A, ALS2/alsin, SPG11); and multifactorial/oligogenic/polygenic in sporadic disease. - Penetrance: Incomplete and age-dependent — notably C9orf72 (near-complete only by ~80 y) and SOD1 (allele-dependent; A4V high, D90A variable/recessive). ATXN2 = risk factor, not fully penetrant. - Expressivity: Highly variable — same C9orf72 expansion can yield pure ALS, pure FTD, or ALS-FTD within one family. - Anticipation: C9orf72 shows repeat instability and some evidence of anticipation, but it is not a classic clean anticipation disorder. - Oligogenic inheritance: Increasingly recognized (e.g., co-occurring C9orf72 + ATXN2 or + TBK1 variants worsen/modify phenotype) — relevant to the dismech digenic/oligogenic curation pattern. - Founder effects: SOD1-D90A (Scandinavian/Finnish recessive founder haplotype); C9orf72 shares a common founder haplotype across European populations. - Consanguinity: relevant for recessive juvenile forms (ALS2, SPG11) in consanguineous populations.

Population demographics. Higher measured burden in European-ancestry populations; male predominance (M:F ~1.2–1.5:1, attenuating with age). Geographic clusters historically: Western Pacific ALS-PDC (Guam Chamorro, Kii Peninsula Japan, West Papua) — declining, environmentally linked.

10. Diagnostics

ALS is a clinical diagnosis (UMN + LMN signs, progressive spread, exclusion of mimics) supported by electrophysiology; no single confirmatory test.

Diagnostic criteria. - Gold Coast criteria (2020/2021) — current consensus; simplified dichotomous (ALS vs not-ALS), higher sensitivity (~93–96%) than revised El Escorial (Airlie House) and Awaji-shima criteria (Shefner et al., Clin Neurophysiol 2020, PMID:32410883). - Prior systems: revised El Escorial, Awaji (incorporates EMG as clinical-equivalent).

Electrophysiology (core). Needle EMG shows active + chronic denervation/reinnervation (fibrillations, positive sharp waves, fasciculation potentials, large/unstable motor units) in ≥2 body regions; nerve conduction studies exclude conduction block/neuropathy; motor unit number estimation (MUNE) and transcranial magnetic stimulation (threshold tracking → cortical hyperexcitability) as research/supportive tools.

Laboratory & biomarkers. - Neurofilaments — the key fluid biomarker: elevated serum/CSF neurofilament light chain (NfL) and phosphorylated neurofilament heavy chain (pNfH) support diagnosis, correlate with progression rate, and are used as pharmacodynamic/prognostic markers. NfL reduction was the surrogate endpoint for tofersen's accelerated approval (Miller et al., N Engl J Med 2022 VALOR, PMID:36170501). - Routine labs to exclude mimics: CK (mildly elevated), TSH, PTH, serum protein electrophoresis, anti-GM1 (to exclude multifocal motor neuropathy), HIV, Lyme, heavy metals, hexosaminidase A, VLCFA, CSF. - LOINC codes exist for NfL and the exclusionary panel.

Imaging. MRI brain/spinal cord primarily to exclude structural mimics (cervical spondylotic myelopathy, structural lesions); may show corticospinal-tract T2/FLAIR hyperintensity and motor-cortex "iron" hypointensity. Advanced DTI/functional MRI and PET (e.g., TSPO neuroinflammation) are research tools.

Genetic testing. Increasingly standard given gene-targeted therapy: at minimum C9orf72 repeat-primed PCR and SOD1 sequencing (therapeutically actionable), plus ALS gene panels / exome (TARDBP, FUS, TBK1, etc.). Testing now recommended for all ALS patients per updated consensus (actionability + trial eligibility + reproductive counseling). C9orf72 requires repeat-expansion testing (not captured by standard NGS).

Pathology (confirmatory at autopsy). Loss of anterior-horn and Betz cells; ubiquitin/p62-positive, TDP-43-positive cytoplasmic inclusions (Bunina bodies, skein-like inclusions); TDP-43 immunohistochemistry (Neumann et al., PMID:17023659). SOD1- and FUS-cases are TDP-43-negative.

Differential diagnosis. Multifocal motor neuropathy with conduction block, cervical spondylotic myelopathy, inclusion-body myositis, Kennedy disease (SBMA), spinal muscular atrophy, myasthenia gravis, ALS mimics (paraneoplastic, thyrotoxic), and monomelic amyotrophy (Hirayama).

Screening. No population screening. Cascade genetic testing / presymptomatic testing offered in known-mutation families (with counseling); presymptomatic NfL monitoring is emerging in SOD1 carriers (ATLAS).

11. Outcome / Prognosis

Survival: median ~2–4 years from symptom onset; ~50% die within 30 months of onset; ~10–20% survive >5 years, ~5–10% >10 years. Respiratory failure is the leading cause of death.
Mortality: essentially a uniformly fatal disease; disease-specific mortality dominates.
Prognostic factors (worse): bulbar or respiratory onset, older age at onset, short diagnosis delay / steep ALSFRS-R slope, low/declining FVC, low BMI and weight loss, cognitive impairment/FTD, high baseline NfL. Better: limb onset, young age, PLS/flail variants, SOD1-D90A, high BMI. The validated ENCALS survival model integrates these predictors.
Morbidity / disability: progressive tetraparesis, anarthria, dysphagia (malnutrition, aspiration pneumonia), ventilatory dependence, communication loss, and (in a subset) dementia — profound disability captured by ICF and ALSFRS-R.
QoL measures: ALSAQ-40/-5, EQ-5D, SF-36; caregiver burden is high.
Prognostic biomarkers: NfL/pNfH (rate + survival), ALSFRS-R slope, FVC/SNIP, and genotype (C9orf72 → shorter survival + FTD risk).

12. Treatment

No cure; management is multidisciplinary and largely disease-modifying-modest + supportive. Multidisciplinary ALS-clinic care itself improves survival and QoL (MAXO:0000950 supportive care; multidisciplinary care).

Disease-modifying pharmacotherapy. - Riluzole (CHEBI:8863) — anti-glutamatergic (Na⁺-channel/glutamate-release inhibitor). First and only globally licensed drug; prolongs survival/time-to-tracheostomy by ~2–3 months (Bensimon et al., N Engl J Med 1994, PMID:8302340). Oral tablet, liquid, and film formulations. MAXO: pharmacotherapy. - Edaravone (CHEBI:31530) — free-radical scavenger; IV and oral; slowed ALSFRS-R decline in a defined early-stage subgroup (Writing Group/Edaravone ALS-19 Study Group, Lancet Neurol 2017, PMID:28522181). Benefit debated; approved in US/Japan/others, not by EMA. - Tofersen (Qalsody) — antisense oligonucleotide (ASO), RNase-H knockdown of SOD1 mRNA; intrathecal. FDA accelerated approval April 2023 for SOD1-ALS — the first therapy targeting a genetic cause of ALS, approved on NfL reduction as surrogate; VALOR + open-label extension (Miller et al., N Engl J Med 2022, PMID:36170501). This maps directly to the dismech antisense_oligonucleotide_therapy module (RNase-H arm, target_gene SOD1) and therapeutic_modality: ANTISENSE_OLIGONUCLEOTIDE, aso_mechanism: RNASE_H_KNOCKDOWN. - Sodium phenylbutyrate/taurursodiol (AMX0035, Relyvrio/Albrioza) — approved 2022, then withdrawn from market in 2024 after the confirmatory PHOENIX phase 3 failed. Curate as historical/withdrawn (important accuracy point).

Pharmacogenomics / precision. SOD1 and C9orf72 genotype now gate therapy (tofersen for SOD1; investigational C9orf72 ASOs). This is genotype-guided precision neurology.

Advanced / investigational therapeutics. - C9orf72-targeted ASOs (e.g., BIIB078 — failed; afinersen; next-generation candidates) and RNA-targeting/gene therapies. - Gene therapy / gene editing (AAV-delivered, CRISPR) for SOD1/C9orf72 — preclinical/early clinical. - Cell therapy — mesenchymal stromal cell (NurOwn/debamestrocel — failed primary endpoint; FDA rejected), neural progenitor approaches. - Other trials: HERV-K antiretrovirals (Triumeq), CuATSM, pridopidine, DNL343 (integrated stress-response inhibitor), tofersen presymptomatic (ATLAS), masitinib, ANX005, and platform trials (HEALEY ALS Platform Trial, MND-SMART, TRICALS).

Symptomatic / supportive care (core of management). - Respiratory: non-invasive ventilation (NIV) improves survival and QoL (Bourke et al., Lancet Neurol 2006, PMID:16488378); tracheostomy/invasive ventilation as chosen; cough-assist/secretion management. MAXO: mechanical ventilation / respiratory therapy. - Nutrition: percutaneous endoscopic gastrostomy (PEG) for dysphagia/weight maintenance; high-calorie diet (MAXO: gastrostomy / dietary intervention MAXO:0000088). - Sialorrhea: anticholinergics, botulinum toxin, salivary-gland radiotherapy. - Spasticity/cramps: baclofen, tizanidine, mexiletine (cramps). - Pseudobulbar affect: dextromethorphan/quinidine (Nuedexta). - Rehabilitation: physical (MAXO:0000011), occupational, and speech therapy / AAC communication devices; mobility aids. - Palliative & advance-care planning: hospice, symptom control, respect for ventilation/withdrawal decisions.

Treatment outcomes. Approved drugs yield modest slowing (months), not reversal; combination riluzole + edaravone + supportive care is common. Adverse events: riluzole — transaminitis, asthenia, nausea; edaravone — gait disturbance, bruising, hypersensitivity; tofersen — CSF pleocytosis, myelitis/radiculitis (serious neurologic AEs), headache.

13. Prevention

Primary prevention: No proven strategy; modifiable-risk-factor reduction (smoking cessation) is reasonable. No vaccine/immunization (not infectious).
Secondary prevention / early detection: No population screening. In known-mutation families, presymptomatic genetic testing + NfL surveillance enables early/pre-symptomatic intervention trials (ATLAS in SOD1). Cascade testing with genetic counseling.
Tertiary prevention (complication avoidance): early NIV, PEG, aspiration-pneumonia prevention, DVT/pressure-sore prevention, multidisciplinary clinic follow-up — these prevent complications and extend survival.
Genetic counseling & reproductive options: risk assessment for AD/X-linked/recessive/oligogenic inheritance; preimplantation genetic testing (PGT) and prenatal diagnosis available for known familial mutations (NSGC/ACMG frameworks).
Public-health/environmental: in historical Guam ALS-PDC, dietary/environmental change coincided with declining incidence (BMAA hypothesis).

14. Other Species / Natural Disease

Taxonomy of models/natural disease: human (NCBITaxon:9606); models in mouse (NCBITaxon:10090), rat (NCBITaxon:10116), zebrafish (NCBITaxon:7955), Drosophila (NCBITaxon:7227), C. elegans (NCBITaxon:6239), pig, and non-human primate.
Natural / veterinary disease: Canine degenerative myelopathy (DM) is a naturally-occurring SOD1-associated progressive spinal-cord/motor disorder (notably in German Shepherds, Pembroke Welsh Corgis, Boxers), caused by SOD1 c.118G>A (p.E40K) and a second SOD1 variant — a recognized large-animal ortholog model of SOD1-ALS (OMIA entry for degenerative myelopathy/SOD1 in Canis lupus familiaris). Equine motor neuron disease (EMND), linked to vitamin-E deficiency/oxidative stress, is a naturally-occurring LMN disease in horses resembling sporadic ALS. (Both = MODEL_ORGANISM evidence per dismech rules; document breed with VBO where possible.)
Comparative biology / evolutionary conservation: SOD1, TARDBP, FUS, C9orf72 orthologs are deeply conserved; core mechanisms (proteostasis, RNA metabolism, oxidative stress) are conserved from yeast to human, enabling cross-species modeling (Alliance of Genome Resources).
Transmission / zoonosis: none — ALS is not infectious or zoonotic (prion-like propagation is intracellular templating, not transmissible between individuals).

15. Model Organisms

Rodent (mammalian) — dominant models. - SOD1-G93A transgenic mouse — the classic ALS model; recapitulates progressive motor-neuron loss, paralysis, and shortened lifespan (Gurney et al., Science 1994, PMID:8209258). SOD1-G37R, G85R, D90A lines also used. Rat SOD1-G93A/H46R models for larger-CNS studies (intrathecal dosing, CSF sampling). - TDP-43 models (TARDBP overexpression/knock-in, e.g., Q331K, M337V) — reproduce TDP-43 pathology but overexpression toxicity confounds interpretation. - FUS transgenic/knock-in models — cytoplasmic FUS pathology, motor deficits. - C9orf72 models — BAC-transgenic mice carrying the human expansion (RNA foci + DPRs; variable motor phenotype across labs), AAV-(G4C2)n models, and C9orf72-knockout mice (immune/autophagy phenotype, models haploinsufficiency arm).

Genetic-model types available. Knockout, knock-in, transgenic (BAC), conditional (cell-type-specific to dissect neuron vs astrocyte vs microglia contributions), and humanized lines (MGI/IMPC/IMSR resources).

Non-mammalian & cellular. - Zebrafish (sod1, tardbp, fus, c9orf72 morphants/mutants) — rapid axonal/NMJ phenotyping. - Drosophila and C. elegans — DPR-toxicity and modifier screens (large-scale genetic screens defined nucleocytoplasmic-transport and RNA-metabolism modifiers). - iPSC-derived motor neurons from patient fibroblasts — the leading human in vitro platform (TDP-43 mislocalization, hyperexcitability, survival assays); iPSC-derived astrocytes/microglia and organoids/assembloids for non-cell-autonomous and NMJ modeling. Immortalized lines (NSC-34) for biochemistry.

Phenotype recapitulation & limitations. SOD1 mice reproduce the motor phenotype well but SOD1 accounts for a minority of human ALS and lacks TDP-43 pathology; C9orf72 mouse motor phenotypes are inconsistent between labs (a documented HUMAN_MODEL_MISMATCH: robust molecular pathology without reliable neurodegeneration/paralysis). No single model captures the full sporadic-ALS, TDP-43-centric human disease — a key knowledge gap and a driver of the shift toward patient iPSC systems. (Model databases: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, Cellosaurus.)

Consolidated Ontology-Term Suggestions (for KB population)

MONDO: MONDO:0004976 (ALS); MONDO:0007103 (ALS1/SOD1).
HP (phenotypes): HP:0003323, HP:0003202, HP:0002380, HP:0003394, HP:0001257, HP:0001347, HP:0001260, HP:0002015, HP:0002307, HP:0002878/HP:0002093, HP:0002094, HP:0001824, HP:0000749, HP:0002145, HP:0100543.
GO (processes/CC): GO:0008380, GO:0006406, GO:0010494, GO:0006913, GO:0006914, GO:0043161, GO:0006979, GO:0004784, GO:0051966, GO:0150076, GO:0043065; components GO:0005737, GO:0031594, GO:0005643.
CL (cells): CL:0000100, CL:0011001, CL:0000598, CL:0000127, CL:0000129, CL:0000188.
UBERON (anatomy): UBERON:0001384, UBERON:0002026, UBERON:0002718, UBERON:0002240, UBERON:0001103, UBERON:0001134.
CHEBI (chemicals): CHEBI:8863 (riluzole), CHEBI:31530 (edaravone), CHEBI:14321 (glutamate), CHEBI:29108 (calcium), CHEBI:18421 (superoxide), CHEBI:16240 (hydrogen peroxide).
HGNC (genes): hgnc:11179 (SOD1), hgnc:28337 (C9orf72), hgnc:11571 (TARDBP), hgnc:4010 (FUS), hgnc:11584 (TBK1), hgnc:6323 (KIF5A). (Verify all with OAK — lowercase hgnc: per repo convention.)
MAXO (treatments): pharmacotherapy (riluzole/edaravone/tofersen), mechanical/non-invasive ventilation, gastrostomy, physical therapy (MAXO:0000011), dietary intervention (MAXO:0000088), supportive/palliative care (MAXO:0000950).

Key Landmark Citations (verified real; snippets to be re-fetched before KB commit)

PMID	Citation	Use
8446170	Rosen et al., Nature 1993 — SOD1 mutations in fALS	First ALS gene
8302340	Bensimon et al., N Engl J Med 1994 — riluzole RCT	Treatment/survival
8209258	Gurney et al., Science 1994 — SOD1-G93A mouse	Model organism
16741123	Boillée et al., Science 2006 — microglia/non-cell-autonomous	Neuroinflammation
16488378	Bourke et al., Lancet Neurol 2006 — NIV RCT	Respiratory management
17023659	Neumann et al., Science 2006 — TDP-43 as inclusion protein	Core pathology
18309045	Sreedharan et al., Science 2008 — TARDBP mutations	Genetics
19251627 / 19251628	Kwiatkowski / Vance et al., Science 2009 — FUS	Genetics
20740007	Elden et al., Nature 2010 — ATXN2	Risk/modifier gene
21944778 / 21944779	DeJesus-Hernandez / Renton et al., Neuron 2011 — C9orf72	Most common gene
21857683	Deng et al., Nature 2011 — UBQLN2 (X-linked)	Genetics/proteostasis
23393093 / 23415312	Mori / Ash et al., 2013 — DPR/RAN translation	C9orf72 mechanism
22042175	Roche et al., Brain 2012 — King's staging	Staging
24507800	Al-Chalabi et al., Lancet Neurol 2014 — multistep model	Etiology
26192745	Freischmidt et al., Nat Neurosci 2015 — TBK1	Genetics
27830784	Taylor, Brown, Ravits, Nature 2016 — "Decoding ALS"	Mechanism review
28552366	van Es et al., Lancet 2017 — ALS seminar	Clinical review
28522181	Writing Group, Lancet Neurol 2017 — edaravone RCT	Treatment
28700839	Brown & Al-Chalabi, N Engl J Med 2017 — ALS review	Overview
29566793	Nicolas et al., Neuron 2018 — KIF5A	Genetics
32410883	Shefner et al., Clin Neurophysiol 2020 — Gold Coast criteria	Diagnosis
36170501	Miller et al., N Engl J Med 2022 — VALOR/tofersen	Gene-targeted therapy
36116464	Feldman et al., Lancet 2022 — ALS review	Overview/epidemiology

Sources (web-verified during research)

Curation flags for the KB entry: 1. Model as Complex disease with a monogenic subtype layer (SOD1, C9orf72, TARDBP, FUS, TBK1, KIF5A…) — good candidate for has_subtypes + oligogenic inheritance modeling (C9orf72+ATXN2/TBK1). 2. antisense_oligonucleotide_therapy module conformance (tofersen, RNase-H, SOD1) is a natural fit. 3. Record AMX0035/Relyvrio as withdrawn (2024) — accuracy-critical. 4. Flag C9orf72 mouse HUMAN_MODEL_MISMATCH and sporadic-ALS/TDP-43 model gap as discussions (kind: HUMAN_MODEL_MISMATCH / KNOWLEDGE_GAP). 5. All snippets require just fetch-reference verification before commit; treat HERV-K/BMAA as hypotheses, not established etiology.

Disorder ▸

Disorder

Name: Amyotrophic Lateral Sclerosis
Category: Complex
Existing deep-research providers: falcon
Existing evidence reference count in YAML: 52

Key Pathophysiology Nodes

Motor Neuron Degeneration
TDP-43 Proteinopathy
C9orf72 Repeat Expansion Toxicity
Glutamate Excitotoxicity
Oxidative Stress
Neuroinflammation
Microglial TREM2 Signaling
Axonal Transport Dysfunction
Impaired Autophagy
Genetic Drivers and Therapeutic Translation
Deep research literature mapping

Citation Inventory (for evidence mapping)

DOI:10.1016/s1474-4422(21
DOI:10.1038/s41573-022-00612-2
DOI:10.1093/brain/awae039
DOI:10.3389/fmolb.2025.1608853
DOI:10.3390/cells13110888

Falcon ▸

Pathophysiology description

Edison Scientific Literature 18 citations 2026-01-08T20:58:49.960392

Pathophysiology description ALS is a multisystem neurodegenerative disease characterized by progressive degeneration of upper and lower motor neurons with pervasive disturbances in RNA metabolism, proteostasis, axonal transport, mitochondrial function, excitatory signaling, and neuroimmune homeostasis. A unifying feature is proteinopathy: cytoplasmic aggregation and nuclear depletion of the RNA-binding protein TDP-43 occur in approximately 97% of ALS, disrupting splicing (e.g., STMN2) and RNA handling, with additional, largely mutually exclusive proteinopathies driven by SOD1 or FUS in subsets; C9orf72 repeat expansions add toxic gain-of-function via repeat RNA foci and dipeptide-repeat proteins (DPRs) plus possible haploinsufficiency (G4C2) (first described comprehensively and updated across mechanisms) (https://doi.org/10.1016/S1474-4422(21)00414-2, May 2022; https://doi.org/10.1038/s41573-022-00612-2, Dec 2023) (goutman2022emerginginsightsinto pages 6-8, mead2023amyotrophiclateralsclerosis pages 6-7). Nucleocytoplasmic transport (NCT) defects are a recurring axis linking these proteinopathies to motor neuron vulnerability through nuclear pore complex and Ran-GTPase cycle dysfunction, exacerbated by arginine-rich DPRs (poly-PR/GR) and by FUS/TDP-43 aggregation (https://doi.org/10.1016/S1474-4422(21)00414-2, May 2022) (goutman2022emerginginsightsinto pages 8-9). Excitotoxicity stemming from cortical hyperexcitability, impaired astrocytic glutamate clearance (EAAT2/SLC1A2), and altered receptor composition is increasingly viewed as a convergent pathway (“dying forward” hypothesis), even as clinical trial experience underscores the need to better map the route from hyperexcitability to neuronal death (https://doi.org/10.1093/brain/awae039, Feb 2024) (nguyen2024updatesondisease pages 1-2). Mitochondrial bioenergetic defects, oxidative stress, and mitophagy/autophagy impairment coexist with axonal transport failure and early neuromuscular junction (NMJ) denervation, while glial and peripheral immune responses (microglia, astrocytes, monocytes/NK cells) shape progression (https://doi.org/10.1016/S1474-4422(21)00414-2, May 2022; https://doi.org/10.1038/s41573-022-00612-2, Dec 2023) (goutman2022emerginginsightsinto pages 26-28, mead2023amyotrophiclateralsclerosis pages 6-7).

Key concepts and definitions with current understanding - Proteinopathy and ribostasis: “TDP-43 pathology is characteristic of the majority of ALS cases,” with mislocalization and aggregation that impair RNA splicing, including STMN2, and engage stress granule/LLPS biology; SOD1 and FUS drive alternative proteopathic subtypes (https://doi.org/10.1016/S1474-4422(21)00414-2, 2022) (goutman2022emerginginsightsinto pages 6-8). - C9orf72 repeat expansion: Dual mechanisms—loss of function (haploinsufficiency) and gain of function via repeat RNA and DPRs (poly-PR/GR/GA)—that converge on NCT, heterochromatin, proteostasis, and trigger TDP-43 pathology (https://doi.org/10.1016/S1474-4422(21)00414-2, 2022) (goutman2022emerginginsightsinto pages 8-9). - Nucleocytoplasmic transport (NCT): Nuclear pore, importin/Ran cycle, and nuclear envelope alterations present in human ALS tissue and models; DPRs and FUS/TDP-43 assemblies disrupt nuclear import/export (https://doi.org/10.1016/S1474-4422(21)00414-2, 2022) (goutman2022emerginginsightsinto pages 8-9). - Excitotoxicity: Cortical hyperexcitability and impaired EAAT2-mediated glutamate clearance contribute to glutamate-driven neuronal injury; translational gaps remain between biomarkers/physiology and therapy (https://doi.org/10.1093/brain/awae039, 2024) (nguyen2024updatesondisease pages 1-2). - Axonal transport/NMJ: Trafficking gene hits (KIF5A, DCTN1, PFN1) and early NMJ denervation align with a “dying-back” contribution to weakness (https://doi.org/10.1016/S1474-4422(21)00414-2, 2022; https://doi.org/10.1038/s41573-022-00612-2, 2023) (goutman2022emerginginsightsinto pages 22-26, mead2023amyotrophiclateralsclerosis pages 6-7). - Mitochondrial dysfunction/oxidative stress: Mutations/aggregates compromise mitochondrial dynamics and respiration, elevating ROS and linking to bioenergetic biomarkers (31P-MRS) (https://doi.org/10.1038/s41573-022-00612-2, 2023) (mead2023amyotrophiclateralsclerosis pages 6-7). - Neuroinflammation: Microglial/astrocytic activation states and infiltration of peripheral immune effectors (e.g., NK cells) accompany motor neuron loss and may modulate trajectory (https://doi.org/10.1016/S1474-4422(21)00414-2, 2022) (goutman2022emerginginsightsinto pages 26-28).

Recent developments and latest research (2023–2024 prioritized) - Comprehensive therapeutic translation map (2023): An advanced pipeline targets proteostasis, RNA metabolism, mitochondria, and inflammation; PB-TURSO (phenylbutyrate/taurursodiol) slowed ALSFRS-R decline and improved survival in a phase II study, highlighting mitochondrial/proteostasis targeting (https://doi.org/10.1038/s41573-022-00612-2, Dec 2023) (mead2023amyotrophiclateralsclerosis pages 6-7). - Excitotoxicity reappraisal (2024): Mechanistic synthesis clarifies primary (synaptic) and secondary (intracellular) cascades and emphasizes EAAT2 and cortical network-level hyperexcitability as strategic targets (https://doi.org/10.1093/brain/awae039, Feb 2024) (nguyen2024updatesondisease pages 1-2). - Biomarker integration (2025 review summarizing 2023–2024): Neurofilament light (NfL) and pNfH support diagnosis/prognosis; poly-GP DPRs serve as target-engagement readouts in C9orf72 trials; digital and imaging biomarkers are rising (https://doi.org/10.3389/fmolb.2025.1608853, Jun 2025, cites 2023–2024 primary data) (anjum2025emergingbiomarkersin pages 2-3).

Current applications and real-world implementations - Gene-directed therapy: Tofersen (SOD1 ASO) achieved CSF SOD1 reduction and is used in gene-directed contexts; biomarker (NfL) trajectories help demonstrate pharmacodynamic impact and support presymptomatic trial design (NCT references in 2022–2023 synthesis) (https://doi.org/10.1016/S1474-4422(21)00414-2, 2022; https://doi.org/10.1038/s41573-022-00612-2, 2023) (goutman2022emerginginsightsinto pages 6-8, mead2023amyotrophiclateralsclerosis pages 6-7). - Biomarkers in practice: Blood/CSF NfL and pNfH increasingly aid differential diagnosis and prognosis and are incorporated into trial enrichment and monitoring plans (https://doi.org/10.3389/fmolb.2025.1608853, 2025) (anjum2025emergingbiomarkersin pages 2-3).

Expert opinions and analysis from authoritative sources - “ALS is poised for successful therapeutic translation,” with mechanistic subclassification and biomarker-enabled trials expected to improve translation across heterogeneous subtypes (Nature Reviews Drug Discovery, Dec 2023) (mead2023amyotrophiclateralsclerosis pages 6-7). - “Evidence of increased glutamate and hyperexcitability… provides an empirical support base for the ‘dying forward’ excitotoxicity hypothesis,” yet mapping hyperexcitability to excitotoxicity requires refined experimental paradigms to guide therapy (Brain, Feb 2024) (nguyen2024updatesondisease pages 1-2).

Relevant statistics and data from recent studies - Epidemiology and genetics: Prevalence 4–8 per 100,000; onset 55–60 years; ~10% familial (fALS), ~90% sporadic; C9orf72 expansions are the most common genetic cause in Europe/USA fALS (~40–50%) and present in ~5–10% of sALS; SOD1 mutations ~2% of sALS (Cells, May 2024) (https://doi.org/10.3390/cells13110888) (nguyen2024updatesondisease pages 1-2). - Pathology ubiquity: “TAR DNA-binding protein 43 (TDP-43) inclusions are observed in ~97% of those diagnosed with amyotrophic lateral sclerosis,” underscoring TDP-43 as the dominant proteopathy (Lancet Neurology, May 2022) (goutman2022emerginginsightsinto pages 6-8).

Research Objectives Comprehensive report on the molecular and cellular mechanisms underlying ALS disease progression

1) Core Pathophysiology - Primary pathophysiological mechanisms - Protein aggregation with nuclear depletion of RBPs (TDP-43, FUS) and SOD1/FUS proteinopathy subtypes; TDP-43 proteinopathy dominates and impairs splicing (e.g., STMN2), RNA transport, and stress granule dynamics (LLPS) (https://doi.org/10.1016/S1474-4422(21)00414-2, 2022) (goutman2022emerginginsightsinto pages 6-8). - C9orf72 repeat RNA and DPR toxicity plus haploinsufficiency converge on NCT, chromatin, translation, and proteostasis; DPRs (poly-PR/GR) bind nucleic acids and NCT factors, impairing nuclear function (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 8-9). - NCT breakdown involving nuclear pore components, importins, Ran-GTPase cycle, and nuclear envelope morphology in ALS motor cortex and spinal motor neurons (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 8-9). - Glutamate excitotoxicity via cortical hyperexcitability and astrocytic EAAT2 downregulation, with primary synaptic and secondary intracellular cascades (Brain 2024) (nguyen2024updatesondisease pages 1-2). - Mitochondrial respiratory/bioenergetic dysfunction with oxidative stress; preclinical/clinical mitochondrial-targeting strategies are in development or translation (Nature Rev Drug Discov 2023) (mead2023amyotrophiclateralsclerosis pages 6-7). - Axonal transport failure and early NMJ denervation (dying-back) intersect with cytoskeletal gene defects (KIF5A, DCTN1, PFN1) (Lancet Neurology 2022; Nature Rev Drug Discov 2023) (goutman2022emerginginsightsinto pages 22-26, mead2023amyotrophiclateralsclerosis pages 6-7). - Neuroinflammation with CNS microglial/astrocytic activation and peripheral immune contributions (NK cells, monocytes), including infiltration and altered cytokines (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 26-28).

Dysregulated molecular pathways
RNA metabolism and splicing; stress granule/LLPS persistence; autophagy–lysosome and ubiquitin–proteasome systems (UPS) failure; NCT and nuclear pore dysfunction; glutamatergic transmission and transporter regulation; mitochondrial dynamics/mitophagy; axonal trafficking and cytoskeletal integrity; innate/adaptive immune signaling (Lancet Neurology 2022; Nature Rev Drug Discov 2023) (goutman2022emerginginsightsinto pages 22-26, mead2023amyotrophiclateralsclerosis pages 6-7).
Affected cellular processes
mRNA splicing (e.g., STMN2), RNA transport, ribostasis; protein quality control and degradation; organelle transport; calcium/ROS homeostasis; synaptic transmission; microglial–astrocyte reactivity states and leukocyte trafficking (Lancet Neurology 2022; Brain 2024; Nature Rev Drug Discov 2023) (goutman2022emerginginsightsinto pages 6-8, nguyen2024updatesondisease pages 1-2, mead2023amyotrophiclateralsclerosis pages 6-7).

2) Key Molecular Players - Genes/Proteins (HGNC recommended symbols) - TARDBP (TDP-43): RBP, aggregation/nuclear depletion in ~97% ALS; RNA splicing impairment (STMN2) (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 6-8). - SOD1: misfolding/aggregation, oxidative stress, mitochondrial/axonal transport defects; target of ASO therapy (Nature Rev Drug Discov 2023) (mead2023amyotrophiclateralsclerosis pages 6-7). - FUS: RBP with LLPS/stress granule biology and NCT linkage (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 22-26). - C9orf72: G4C2 repeat expansion driving RNA foci and DPRs (poly-PR/GR/GA) with NCT/chromatin/proteostasis toxicity plus potential haploinsufficiency (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 8-9). - Additional implicated/modifier genes: KIF5A, DCTN1, PFN1 (axonal/cytoskeleton); TBK1, OPTN, VCP, SQSTM1, CCNF, DNAJC7 (autophagy–UPS); NEK1, C21orf2 (DNA repair/axon cilium); TIA1 (RNA granules) (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 29-30, goutman2022emerginginsightsinto pages 22-26).

Chemical Entities / Biomarkers (CHEBI where applicable)
Glutamate (CHEBI:14321): excitatory neurotransmitter driving excitotoxic cascades; elevated CSF reported in subsets (Brain 2024; Cells 2024) (nguyen2024updatesondisease pages 1-2).
Neurofilament light (NfL) and phosphorylated neurofilament heavy (pNfH): fluid biomarkers of axonal injury with diagnostic/prognostic value and utility in trials (Frontiers Mol Biosci 2025) (anjum2025emergingbiomarkersin pages 2-3).
Cell Types (CL)
Motor neurons (upper cortical and lower spinal/brainstem) are primary degenerating cells; astrocytes and microglia show reactive phenotypes; peripheral NK cells/monocytes may contribute (Lancet Neurology 2022; Brain 2024) (goutman2022emerginginsightsinto pages 26-28, nguyen2024updatesondisease pages 1-2).
Anatomical Locations (UBERON)
Motor cortex and corticospinal tract; spinal anterior horn; brainstem motor nuclei; neuromuscular junctions and skeletal muscle (Lancet Neurology 2022; Nature Rev Drug Discov 2023) (mead2023amyotrophiclateralsclerosis pages 6-7, goutman2022emerginginsightsinto pages 22-26).

3) Biological Processes (for GO annotation) - RNA splicing and mRNA processing (GO:0008380), RNA transport (GO:0051028) perturbed by TDP-43/FUS (goutman2022emerginginsightsinto pages 6-8, goutman2022emerginginsightsinto pages 22-26). - Protein quality control via UPS (GO:0030433) and autophagy–lysosome pathways (GO:0006914) impaired (goutman2022emerginginsightsinto pages 22-26, mead2023amyotrophiclateralsclerosis pages 6-7). - Nucleocytoplasmic transport (GO:0006913/GO:0051169) disrupted (goutman2022emerginginsightsinto pages 8-9). - Glutamatergic synaptic transmission (GO:0098978) and glutamate uptake (EAAT2/SLC1A2) (GO:0015813) dysregulated (nguyen2024updatesondisease pages 1-2). - Mitochondrial organization (GO:0007005), oxidative phosphorylation (GO:0006119), and mitophagy (GO:0000422) impaired (mead2023amyotrophiclateralsclerosis pages 6-7). - Axonal transport (GO:0098930) and cytoskeletal organization (GO:0007010) defective (goutman2022emerginginsightsinto pages 22-26). - Microglial activation (GO:0001774) and astrocyte activation (GO:0061893) with peripheral immune cell infiltration (goutman2022emerginginsightsinto pages 26-28).

4) Cellular Components - Stress granules (GO:0010494), cytoplasmic aggregates/inclusions; nuclear pore complex (GO:0005643) and nuclear envelope; mitochondria (GO:0005739), ER (GO:0005783); synapse (GO:0045202) and NMJ (GO:0031594); axon (GO:0030424) (goutman2022emerginginsightsinto pages 8-9, mead2023amyotrophiclateralsclerosis pages 6-7, goutman2022emerginginsightsinto pages 22-26).

5) Disease Progression - Proposed sequence (population- and model-informed): Molecular triggers (genetic variants/environmental exposures) initiate ribostasis/proteostasis stress and NCT dysfunction; cortical hyperexcitability and impaired glutamate uptake promote “dying forward” stress on spinal motor neurons; in parallel, axonal transport failure and early NMJ denervation contribute “dying back” pathology; mitochondrial failure and oxidative stress amplify injury; reactive microglia/astrocytes and infiltrating immune cells modulate progression; clinical manifestations spread regionally following neuroanatomical connectivity (Lancet Neurology 2022; Brain 2024; Nature Rev Drug Discov 2023) (goutman2022emerginginsightsinto pages 22-26, nguyen2024updatesondisease pages 1-2, mead2023amyotrophiclateralsclerosis pages 6-7). - Stages: Presymptomatic biomarker phase (e.g., rising NfL) → focal onset (spinal/bulbar) → regional spread with mixed UMN/LMN signs → respiratory failure/end-stage (Nature Rev Drug Discov 2023; Cells 2024) (mead2023amyotrophiclateralsclerosis pages 6-7, nguyen2024updatesondisease pages 1-2).

6) Phenotypic Manifestations (HPO) - Muscle weakness (HP:0001324), fasciculations (HP:0003403), spasticity (HP:0001257), dysarthria (HP:0001260), dysphagia (HP:0002015), respiratory insufficiency (HP:0002093), frontotemporal cognitive/behavioral changes in a subset (HP:0002145) (Cells 2024) (nguyen2024updatesondisease pages 1-2). - Biological correlates: Elevated NfL/pNfH predict faster progression; CSF glutamate elevations in a subset correlate with spinal features; presence of TDP-43 inclusions is near-universal in non-SOD1/FUS subtypes (Brain 2024; Lancet Neurology 2022; Frontiers Mol Biosci 2025) (nguyen2024updatesondisease pages 1-2, goutman2022emerginginsightsinto pages 6-8, anjum2025emergingbiomarkersin pages 2-3).

Gene/Protein annotations with ontology terms (examples) - TARDBP (HGNC:11577): RNA splicing/transport (GO:0008380/GO:0051028); stress granule dynamics (GO:0010494); nucleus/cytoplasm (GO:0005634/GO:0005737). Evidence: TDP-43 pathology and splicing defects (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 6-8). - SOD1 (HGNC:11179): Response to oxidative stress (GO:0006979), mitochondrial organization (GO:0007005); cytosol/mitochondrion (GO:0005829/GO:0005739). Evidence: oxidative stress/mitochondrial dysfunction (Nature Rev Drug Discov 2023) (mead2023amyotrophiclateralsclerosis pages 6-7). - FUS (HGNC:4010): RNA binding/LLPS; nucleus/cytoplasm; NCT. Evidence: RBP with LLPS/NCT involvement (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 22-26). - C9orf72 (HGNC:28396): Autophagy/endolysosomal trafficking (GO:0006914), nucleocytoplasmic transport perturbation; cytosol/nucleus. Evidence: repeat RNA/DPR toxicity and NCT effects (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 8-9). - TBK1 (HGNC:11584), OPTN (HGNC:17195), VCP (HGNC:12666), SQSTM1 (HGNC:11276): Autophagy/UPS; cytoplasm/lysosome. Evidence: autophagy–proteostasis gene set in ALS (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 29-30). - KIF5A (HGNC:8939), DCTN1 (HGNC:2711), PFN1 (HGNC:8897): Axonal transport/cytoskeleton (GO:0098930/GO:0007010); axon. Evidence: trafficking/cytoskeletal defects in ALS (Lancet Neurology 2022) (goutman2022emerginginsightsinto pages 22-26).

Cell type involvement (CL terms) - Upper motor neurons (CL:0002603) and lower motor neurons (CL:1001608) degenerate; astrocytes (CL:0000127) show reactive states including EAAT2 dysregulation; microglia (CL:0000129) activate and interact with infiltrating immune cells; peripheral NK cells (CL:0000623) exhibit altered signatures (Lancet Neurology 2022; Brain 2024) (goutman2022emerginginsightsinto pages 26-28, nguyen2024updatesondisease pages 1-2).

Anatomical locations (UBERON terms) - Primary motor cortex (UBERON:0001384), corticospinal tract (UBERON:0005346), spinal cord anterior horn (UBERON:0002240), brainstem motor nuclei (UBERON:0019267), neuromuscular junction (UBERON:0001981), skeletal muscle (UBERON:0001134) (Lancet Neurology 2022; Nature Rev Drug Discov 2023) (goutman2022emerginginsightsinto pages 22-26, mead2023amyotrophiclateralsclerosis pages 6-7).

Chemical entities (CHEBI terms) - Glutamate (CHEBI:14321) (excitotoxic mediator) (Brain 2024) (nguyen2024updatesondisease pages 1-2). - Neurofilament light (not in CHEBI; protein biomarker) and pNfH (protein biomarker) (Frontiers Mol Biosci 2025) (anjum2025emergingbiomarkersin pages 2-3).

Evidence items with PMIDs/DOIs/URLs and dates - Goutman SA et al. Emerging insights into the complex genetics and pathophysiology of ALS. Lancet Neurol. May 2022. DOI: 10.1016/S1474-4422(21)00414-2; URL: https://doi.org/10.1016/S1474-4422(21)00414-2 (goutman2022emerginginsightsinto pages 6-8, goutman2022emerginginsightsinto pages 8-9, goutman2022emerginginsightsinto pages 29-30, goutman2022emerginginsightsinto pages 26-28, goutman2022emerginginsightsinto pages 22-26). - Mead RJ et al. ALS: poised for successful therapeutic translation. Nat Rev Drug Discov. Dec 2023. DOI: 10.1038/s41573-022-00612-2; URL: https://doi.org/10.1038/s41573-022-00612-2 (mead2023amyotrophiclateralsclerosis pages 6-7). - Odierna GL et al. How do we get from hyperexcitability to excitotoxicity in ALS? Brain. Feb 2024. DOI: 10.1093/brain/awae039; URL: https://doi.org/10.1093/brain/awae039 (nguyen2024updatesondisease pages 1-2). - Anjum F et al. Emerging biomarkers in ALS. Frontiers Mol Biosci. Jun 2025 (synthesizes 2023–2024 studies). DOI: 10.3389/fmolb.2025.1608853; URL: https://doi.org/10.3389/fmolb.2025.1608853 (anjum2025emergingbiomarkersin pages 2-3).

Direct quotes - “TAR DNA-binding protein 43 (TDP-43) inclusions are observed in ~97% of those diagnosed with amyotrophic lateral sclerosis” (Lancet Neurology, 2022) (goutman2022emerginginsightsinto pages 6-8). - “Evidence of increased glutamate and hyperexcitability… provides an empirical support base for the ‘dying forward’ excitotoxicity hypothesis” (Brain, 2024) (nguyen2024updatesondisease pages 1-2). - “ALS is… poised for successful therapeutic translation” with mechanistic subclassification and biomarkers enabling improved trial design (Nat Rev Drug Discov, 2023) (mead2023amyotrophiclateralsclerosis pages 6-7).

Notes and limitations - Where 2025 reviews are cited, we relied on their synthesis of 2023–2024 primary data for biomarker/application context; mechanistic anchors derive from 2022–2024 high-quality reviews and analyses. Future additions should incorporate single-cell atlases and proteomic maps as they are qualified and publicly accessible.

References

(goutman2022emerginginsightsinto pages 6-8): Stephen A Goutman, Orla Hardiman, Ammar Al-Chalabi, Adriano Chió, Masha G Savelieff, Matthew C Kiernan, and Eva L Feldman. Emerging insights into the complex genetics and pathophysiology of amyotrophic lateral sclerosis. The Lancet Neurology, 21:465-479, May 2022. URL: https://doi.org/10.1016/s1474-4422(21)00414-2, doi:10.1016/s1474-4422(21)00414-2. This article has 398 citations and is from a highest quality peer-reviewed journal.
(mead2023amyotrophiclateralsclerosis pages 6-7): Richard J. Mead, Ning Shan, H. Joseph Reiser, Fiona Marshall, and Pamela J. Shaw. Amyotrophic lateral sclerosis: a neurodegenerative disorder poised for successful therapeutic translation. Nature Reviews. Drug Discovery, 22:185-212, Dec 2023. URL: https://doi.org/10.1038/s41573-022-00612-2, doi:10.1038/s41573-022-00612-2. This article has 493 citations.
(goutman2022emerginginsightsinto pages 8-9): Stephen A Goutman, Orla Hardiman, Ammar Al-Chalabi, Adriano Chió, Masha G Savelieff, Matthew C Kiernan, and Eva L Feldman. Emerging insights into the complex genetics and pathophysiology of amyotrophic lateral sclerosis. The Lancet Neurology, 21:465-479, May 2022. URL: https://doi.org/10.1016/s1474-4422(21)00414-2, doi:10.1016/s1474-4422(21)00414-2. This article has 398 citations and is from a highest quality peer-reviewed journal.
(nguyen2024updatesondisease pages 1-2): Lien Nguyen. Updates on disease mechanisms and therapeutics for amyotrophic lateral sclerosis. Cells, 13:888, May 2024. URL: https://doi.org/10.3390/cells13110888, doi:10.3390/cells13110888. This article has 20 citations and is from a poor quality or predatory journal.
(goutman2022emerginginsightsinto pages 26-28): Stephen A Goutman, Orla Hardiman, Ammar Al-Chalabi, Adriano Chió, Masha G Savelieff, Matthew C Kiernan, and Eva L Feldman. Emerging insights into the complex genetics and pathophysiology of amyotrophic lateral sclerosis. The Lancet Neurology, 21:465-479, May 2022. URL: https://doi.org/10.1016/s1474-4422(21)00414-2, doi:10.1016/s1474-4422(21)00414-2. This article has 398 citations and is from a highest quality peer-reviewed journal.
(goutman2022emerginginsightsinto pages 22-26): Stephen A Goutman, Orla Hardiman, Ammar Al-Chalabi, Adriano Chió, Masha G Savelieff, Matthew C Kiernan, and Eva L Feldman. Emerging insights into the complex genetics and pathophysiology of amyotrophic lateral sclerosis. The Lancet Neurology, 21:465-479, May 2022. URL: https://doi.org/10.1016/s1474-4422(21)00414-2, doi:10.1016/s1474-4422(21)00414-2. This article has 398 citations and is from a highest quality peer-reviewed journal.
(anjum2025emergingbiomarkersin pages 2-3): Farah Anjum, Maha Bakhuraysah, Abdulaziz Alsharif, Taj Mohammad, Anas Shamsi, and Md. Imtaiyaz Hassan. Emerging biomarkers in amyotrophic lateral sclerosis: from pathogenesis to clinical applications. Frontiers in Molecular Biosciences, Jun 2025. URL: https://doi.org/10.3389/fmolb.2025.1608853, doi:10.3389/fmolb.2025.1608853. This article has 1 citations and is from a poor quality or predatory journal.
(goutman2022emerginginsightsinto pages 29-30): Stephen A Goutman, Orla Hardiman, Ammar Al-Chalabi, Adriano Chió, Masha G Savelieff, Matthew C Kiernan, and Eva L Feldman. Emerging insights into the complex genetics and pathophysiology of amyotrophic lateral sclerosis. The Lancet Neurology, 21:465-479, May 2022. URL: https://doi.org/10.1016/s1474-4422(21)00414-2, doi:10.1016/s1474-4422(21)00414-2. This article has 398 citations and is from a highest quality peer-reviewed journal.

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