Amyotrophic Lateral Sclerosis

Complex MONDO:0004976 Pathograph 14 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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Subtypes

Familial ALS

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

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.

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Mechanistic Hypotheses

Canonical Motor Neuron Proteostatic Failure Model

canonical_motor_neuron_proteostatic_failure_model CANONICAL

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; the C9orf72 ASO program (BIIB078) was discontinued after Phase 1 without clinical benefit, indicating that RNA-foci reduction alone is insufficient and DPR-mediated toxicity likely dominates the C9orf72 axis.

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. Three qualifications: (1) the C9orf72-ASO program (BIIB078; Phase 1 discontinued) showed insufficient clinical efficacy — RNA-foci reduction does not consistently translate to motor preservation, suggesting DPR-mediated toxicity may dominate; (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.

Deep research

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

Show evidence (2 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:39986312 PARTIAL 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.

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

tdp43_rna_dysregulation_selective_vulnerability_model EMERGING

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. 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

"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_hypothesis#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 (2 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.

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_hypothesis#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_hypothesis#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 PARTIAL 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.

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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

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 PARTIAL

"Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) share many clinical, pathological, and genetic features"

Single-cell analysis confirms motor neuron vulnerability in ALS and identifies vulnerable populations in cortical layer 5.

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

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

"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.

Show evidence (3 references)

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.

PMID:32799899 SUPPORT Other

"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."

Synthesis supports the coupled loss-of-function and gain-of-function framing of TDP-43 mislocalization.

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.

Show evidence (3 references)

PMID:26250685 SUPPORT In Vitro

"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

"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:37024676 SUPPORT

"Recent advances in sequencing technologies and collaborative efforts have led to substantial progress in identifying the genetic causes of amyotrophic lateral sclerosis (ALS). This momentum has, in turn, fostered the development of putative molecular therapies."

Review links expanding ALS genetic discoveries, including C9orf72, to the development of targeted molecular therapies.

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 (2 references)

PMID:8302340 PARTIAL

"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.

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

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.

Neuroinflammation

Activated microglia and astrocytes contribute to motor neuron death through the release of pro-inflammatory cytokines, reactive oxygen species, and other neurotoxic factors. This non-cell-autonomous mechanism amplifies neurodegeneration.

microglial cell CL:0000129 astrocyte CL:0000127

Show evidence (1 reference)

PMID:34440810 PARTIAL

"In the archetypical neurodegenerative disorder amyotrophic lateral sclerosis (ALS), the recruitment of T-cells is well known"

Review confirms immune cell involvement in ALS pathophysiology with T-cell recruitment to affected areas.

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

anterograde axonal transport GO:0008089

Show evidence (1 reference)

PMID:22312314 PARTIAL

"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.

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

autophagy GO:0006914

Show evidence (1 reference)

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.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

Digestive 1

Dysphagia FREQUENT Dysphagia 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 2

Drooling FREQUENT Drooling 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.

Xerostomia FREQUENT Xerostomia HP:0000217

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists xerostomia as frequent in ALS.

Musculoskeletal 6

Generalized Muscle Weakness OBLIGATE Generalized muscle weakness 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 Spasticity 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.

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 Skeletal muscle atrophy 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.

Muscle Spasm FREQUENT Muscle spasm 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 Spastic paraparesis 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 9

Fasciculations FREQUENT Fasciculations 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 Hyperreflexia 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.

Dysarthria FREQUENT Dysarthria 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 Paralysis HP:0003470

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists paralysis as frequent in ALS.

Depression FREQUENT Depression 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 Anxiety 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 Atypical behavior 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 Cognitive impairment 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.

Sleep Disturbance OCCASIONAL Sleep disturbance HP:0002360

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists sleep disturbance as occasional in ALS.

Respiratory 2

Dyspnea FREQUENT Dyspnea HP:0002094

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists dyspnea as frequent in ALS.

Orthopnea OCCASIONAL Orthopnea HP:0012764

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists orthopnea as occasional in ALS.

Constitutional 2

Fatigue FREQUENT Fatigue 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 Pain 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 1

Weight Loss FREQUENT Weight loss 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.

Other 23

Neurodegeneration OBLIGATE Neurodegeneration 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 Motor neuron atrophy 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.

Babinski Sign FREQUENT Babinski sign 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 Hoffmann sign HP:0031993

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists Hoffmann sign as frequent in ALS.

Dysphonia FREQUENT Dysphonia HP:0001618

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists dysphonia as frequent in ALS.

Fatigable Weakness of Bulbar Muscles FREQUENT Fatigable weakness of bulbar muscles 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 Fatigable weakness of swallowing muscles 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 Fatigable weakness of respiratory muscles 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.

Abnormality on Pulmonary Function Testing FREQUENT Abnormality on pulmonary function testing 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.

Distal Amyotrophy FREQUENT Distal amyotrophy 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 Progressive distal muscular atrophy 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.

Upper Limb Muscle Weakness FREQUENT Upper limb muscle weakness 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 Lower limb muscle weakness 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.

Tongue Fasciculations OCCASIONAL Tongue fasciculations 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 Tongue atrophy HP:0012473

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists tongue atrophy as frequent in ALS.

Foot Dorsiflexor Weakness OCCASIONAL Foot dorsiflexor weakness 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.

Steppage Gait OCCASIONAL Steppage gait HP:0003376

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists steppage gait as occasional in ALS.

Cachexia OCCASIONAL Cachexia HP:0004326

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists cachexia as occasional in ALS.

Emotional Lability FREQUENT Emotional lability 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.

Frontotemporal Dementia OCCASIONAL Frontotemporal dementia 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 Language impairment 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.

Jaw Hyperreflexia OCCASIONAL Jaw hyperreflexia HP:0033683

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists jaw hyperreflexia as occasional in ALS.

Laryngospasm VERY_RARE Laryngospasm HP:0025425

Show evidence (1 reference)

ORPHA:803 SUPPORT

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

Orphanet lists laryngospasm as very rare in ALS.

🧬

Genetic Associations

C9orf72 Repeat Expansion (Causative)

Autosomal Dominant

Show evidence (2 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.

SOD1 Mutations (Causative)

Autosomal Dominant

Show evidence (2 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.

TARDBP Mutations (Causative)

Autosomal Dominant

Show evidence (2 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.

FUS Mutations (Causative)

Autosomal Dominant

Show evidence (2 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.

NEK1 Variants (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.

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

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

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

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

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

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

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.

💊

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

Antioxidant that may slow functional decline in a subset of ALS patients. It reduces oxidative stress and has shown benefit in early-stage patients.

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 demonstrating edaravone slows functional decline in early-stage ALS patients.

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

Antisense oligonucleotide therapy approved for SOD1-ALS that reduces SOD1 protein production, targeting the underlying genetic cause in this subset of patients.

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 (3 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:36543887 SUPPORT

"Significant discoveries and advances have been made in ALS preclinical models, genetics, pathology, biomarkers, imaging and clinical readouts over the last 10-15 years."

Translational review highlights recent advances enabling gene-targeted therapies like tofersen.

Jacifusen (ION363)

Action: pharmacotherapy MAXO:0000058

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 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 PARTIAL 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.

Non-invasive Ventilation

Action: noninvasive ventilation MAXO:0000506

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

Show evidence (1 reference)

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.

Physical Therapy

Action: physical therapy MAXO:0000011

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 MAXO:0000930

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: supportive care MAXO:0000950

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 MAXO:0000950

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 exposure to lead, mercury, and other heavy metals has been associated with increased ALS risk.

Show evidence (1 reference)

PMID:31578652 SUPPORT

"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.

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.

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.

Smoking

Cigarette smoking is a confirmed risk factor for ALS, particularly in women.

Show evidence (1 reference)

PMID:20639382 SUPPORT

"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 indicates elevated ALS risk with smoking, especially among women.

🔬

Biochemical Markers

Neurofilament Light Chain (NfL) (Elevated)

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

Phosphorylated Neurofilament Heavy Chain (pNfH) (Elevated)

Context: CSF and serum biomarker of axonal injury

🔀

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

PMID:33085325

Show evidence (1 reference)

PMID:33085325 SUPPORT

"ALS is a neurodegenerative disorder leading to weakness of the bulbar, thoracic, limb, and abdominal muscles with sparing of sensory function."

Clinical overview notes degeneration across spinal motor systems; spinal cord baseline controls contextualize transcriptomic changes in ALS.

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

PMID:33085325

Show evidence (1 reference)

PMID:33085325 SUPPORT

"ALS is a neurodegenerative disorder leading to weakness of the bulbar, thoracic, limb, and abdominal muscles with sparing of sensory function."

Muscle weakness and atrophy are primary clinical consequences in ALS; healthy muscle RNA-seq provides comparative background for ALS muscle involvement.

{ }

Source YAML

click to show

name: Amyotrophic Lateral Sclerosis
creation_date: '2026-01-14T23:47:09Z'
updated_date: '2026-06-03T15:41:07Z'
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
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.
- 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.
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; the C9orf72 ASO program (BIIB078) was discontinued after Phase 1 without clinical benefit, indicating that RNA-foci reduction alone is insufficient and DPR-mediated toxicity likely dominates the C9orf72 axis.
  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. Three qualifications: (1) the C9orf72-ASO
    program (BIIB078; Phase 1 discontinued) showed insufficient clinical efficacy — RNA-foci
    reduction does not consistently translate to motor preservation,
    suggesting DPR-mediated toxicity may dominate; (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.
  evidence:
  - reference: PMID:38891021
    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:39986312
    reference_title: "Amyotrophic lateral sclerosis caused by hexanucleotide repeat expansions in C9orf72: from genetics to therapeutics."
    supports: PARTIAL
    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.
- 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
    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: PARTIAL
    snippet: "Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) share many clinical, pathological, and genetic features"
    explanation: Single-cell analysis confirms motor neuron vulnerability in ALS and identifies vulnerable populations in cortical layer 5.
  - 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: PARTIAL
    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
  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
      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.
  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
      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.
  evidence:
  - 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
      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.
  - 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.
    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
      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
      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.
  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:37024676
    reference_title: "Amyotrophic lateral sclerosis: translating genetic discoveries into therapies."
    supports: SUPPORT
    snippet: "Recent advances in sequencing technologies and collaborative efforts have led to substantial progress in identifying the genetic causes of amyotrophic lateral sclerosis (ALS). This momentum has, in turn, fostered the development of putative molecular therapies."
    explanation: Review links expanding ALS genetic discoveries, including C9orf72, to the development of targeted molecular therapies.
- 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: PARTIAL
    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.
- 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: Neuroinflammation
  description: >
    Activated microglia and astrocytes contribute to motor neuron death through the release
    of pro-inflammatory cytokines, reactive oxygen species, and other neurotoxic factors.
    This non-cell-autonomous mechanism amplifies neurodegeneration.
  cell_types:
  - preferred_term: microglial cell
    term:
      id: CL:0000129
      label: microglial cell
  - preferred_term: astrocyte
    term:
      id: CL:0000127
      label: astrocyte
  evidence:
  - reference: PMID:34440810
    reference_title: "What Guides Peripheral Immune Cells into the Central Nervous System?"
    supports: PARTIAL
    snippet: "In the archetypical neurodegenerative disorder amyotrophic lateral sclerosis (ALS), the recruitment of T-cells is well known"
    explanation: Review confirms immune cell involvement in ALS pathophysiology with T-cell recruitment to affected areas.
- 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
  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: PARTIAL
    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.
- name: Impaired Autophagy
  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
  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.
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
    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
    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
    supports: SUPPORT
    snippet: "HP:0002180 | Neurodegeneration | Very frequent (99-80%)"
    explanation: Orphanet lists neurodegeneration as very frequent in ALS.
  - reference: PMID:36116464
    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
    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
    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
    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."
    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
    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."
    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
    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."
    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
    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
    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."
    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
    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
    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."
    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
    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
    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
    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
    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
    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."
    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
    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
    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
    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
    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."
    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
    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
    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
    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."
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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
    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."
    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
    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
    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
    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."
    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
    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
    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."
    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
    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
    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
    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
    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
    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 diagnosis, prognosis, and monitoring therapeutic response in clinical trials
- name: Phosphorylated Neurofilament Heavy Chain (pNfH)
  presence: Elevated
  context: CSF and serum biomarker of axonal injury
genetic:
- name: C9orf72 Repeat Expansion
  association: Causative
  notes: Most common genetic cause of ALS (40% familial, 5-10% sporadic); GGGGCC hexanucleotide repeat expansion
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: ORPHA:803
    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.
- name: SOD1 Mutations
  association: Causative
  notes: First identified ALS gene; accounts for approximately 20% of familial ALS and 2% of sporadic cases
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: ORPHA:803
    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.
- name: TARDBP Mutations
  association: Causative
  notes: Encodes TDP-43 protein; mutations cause approximately 5% of familial ALS
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: ORPHA:803
    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.
- name: FUS Mutations
  association: Causative
  notes: RNA-binding protein; mutations cause approximately 5% of familial ALS
  inheritance:
  - name: Autosomal Dominant
  evidence:
  - reference: ORPHA:803
    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.
- name: NEK1 Variants
  association: Susceptibility
  notes: Risk variants found in nearly 3% of ALS cases
  evidence:
  - reference: ORPHA:803
    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: 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.
environmental:
- name: Heavy Metal Exposure
  notes: Occupational exposure to lead, mercury, and other heavy metals has been associated with increased ALS risk.
  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
    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.
- name: Pesticide Exposure
  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
  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
  notes: Cigarette smoking is a confirmed risk factor for ALS, particularly in women.
  evidence:
  - reference: PMID:20639382
    reference_title: "Smoking and the risk of amyotrophic lateral sclerosis: a systematic review and meta-analysis."
    supports: SUPPORT
    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 indicates elevated ALS risk with smoking, especially among women.
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: >
    Antioxidant that may slow functional decline in a subset of ALS patients. It reduces
    oxidative stress and has shown benefit in early-stage patients.
  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 demonstrating edaravone slows functional decline in early-stage ALS patients.
  - 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
  aso_details:
    aso_mechanism: RNASE_H_KNOCKDOWN
    target_gene:
      preferred_term: SOD1
      term:
        id: hgnc:11179
        label: SOD1
    target_transcript: SOD1 mRNA
    aso_chemistry: TWO_PRIME_O_METHOXYETHYL
    conjugation: UNCONJUGATED
  description: >
    Antisense oligonucleotide therapy approved for SOD1-ALS that reduces SOD1 protein
    production, targeting the underlying genetic cause in this subset of patients.
  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:36543887
    reference_title: "Amyotrophic lateral sclerosis: a neurodegenerative disorder poised for successful therapeutic translation."
    supports: SUPPORT
    snippet: "Significant discoveries and advances have been made in ALS preclinical models, genetics, pathology, biomarkers, imaging and clinical readouts over the last 10-15 years."
    explanation: Translational review highlights recent advances enabling gene-targeted therapies like tofersen.
  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
  aso_details:
    aso_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: MAXO:0000058
      label: pharmacotherapy
  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: 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
      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: PARTIAL
    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: 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: MAXO:0000506
      label: noninvasive 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.
- name: Physical Therapy
  description: >
    Range of motion exercises and adaptive strategies to maintain function and prevent
    complications such as contractures.
  treatment_term:
    preferred_term: physical therapy
    term:
      id: MAXO:0000011
      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.
  treatment_term:
    preferred_term: speech therapy
    term:
      id: MAXO:0000930
      label: speech 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: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  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: MAXO:0000950
      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.
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:33085325
  evidence:
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease."
    supports: SUPPORT
    snippet: "ALS is a neurodegenerative disorder leading to weakness of the bulbar, thoracic, limb, and abdominal muscles with sparing of sensory function."
    explanation: Clinical overview notes degeneration across spinal motor systems; spinal cord baseline controls contextualize transcriptomic changes in ALS.
- 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:33085325
  evidence:
  - reference: PMID:33085325
    reference_title: "Electrodiagnostic Evaluation of Motor Neuron Disease."
    supports: SUPPORT
    snippet: "ALS is a neurodegenerative disorder leading to weakness of the bulbar, thoracic, limb, and abdominal muscles with sparing of sensory function."
    explanation: Muscle weakness and atrophy are primary clinical consequences in ALS; healthy muscle RNA-seq provides comparative background for ALS muscle involvement.
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."
    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."
    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."
    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_hypothesis#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.
- 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_hypothesis#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_hypothesis#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: PARTIAL
    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.

📚

References & Deep Research

Deep Research

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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