Amyotrophic Lateral Sclerosis Type 1 (ALS1 / SOD1-ALS): Comprehensive Disease Characterization

Disease: Amyotrophic Lateral Sclerosis Type 1 (ALS1) MONDO ID: MONDO:0007103 · OMIM: #105400 · Category: Mendelian (autosomal dominant, D90A often recessive) Causal gene: SOD1 (Cu/Zn superoxide dismutase 1), chromosome 21q22.11 Prepared: 2026-09-05 · Evidence sources: human clinical, model organism, in vitro, and computational literature (PMIDs cited throughout)

Summary

Amyotrophic Lateral Sclerosis Type 1 (ALS1) is the Mendelian, adult-onset form of amyotrophic lateral sclerosis caused by pathogenic variants in SOD1, the gene encoding the ubiquitously expressed free-radical scavenging enzyme Cu/Zn superoxide dismutase 1. It is the archetypal "familial ALS" gene — the first ALS gene ever identified — and accounts for approximately 2% of all ALS and ~12–20% of familial ALS (PMID: 41661214, PMID: 18055113). Clinically it is largely indistinguishable at the bedside from other ALS: progressive upper- and lower-motor-neuron degeneration producing weakness, muscle atrophy, spasticity, bulbar dysfunction, and ultimately death from respiratory failure. What distinguishes ALS1 is its defined molecular cause, its highly variant-dependent natural history (from the rapidly fatal A4V allele to slowly progressive recessive D90A disease), and — uniquely among neurodegenerative diseases — the existence of an approved, gene-targeted therapy (tofersen).

The central mechanistic insight is that mutant SOD1 causes disease through a toxic gain-of-function, not loss of enzymatic activity. The most frequent worldwide mutation, D90A, produces a protein with normal enzymatic activity, proving the point (PMID: 36385230). Mutant SOD1 misfolds into neurotoxic aggregates that propagate in a prion-like, templated manner between motor neurons (PMID: 41702846, PMID: 32958236). Motor neuron death is non-cell-autonomous: mutant SOD1 in astrocytes, microglia, skeletal muscle, and T cells actively drives neuroinflammation and degeneration (PMID: 25613506). Vulnerable alpha motor neurons transit through a conserved "disease-associated motor neuron" state before dying (PMID: 42335888).

Because the genetic cause is known and neurofilament light chain (NfL) rises presymptomatically, ALS1 has become the proving ground for precision neurology. Tofersen, an intrathecal antisense oligonucleotide (ASO) that lowers SOD1 synthesis, is the first and only approved genetically targeted ALS therapy; it robustly lowers plasma/CSF neurofilament and, in some carriers, produces a "chronic nonprogressive ALS" phenotype never previously observed (PMID: 41661214, PMID: 41850233, PMID: 41670738). The presymptomatic NfL biomarker has empowered the first-ever ALS prevention trial (ATLAS, NCT04856982) (PMID: 37382103).

Section 1 — Disease Information

Overview. ALS1 is the SOD1-related subtype of amyotrophic lateral sclerosis, a fatal adult-onset motor neuron disease characterized by progressive degeneration of upper (corticospinal) and lower (spinal/bulbar) motor neurons, leading to muscle weakness, atrophy, fasciculations, spasticity, bulbar palsy, and terminal respiratory failure. It was the first genetically defined form of ALS (SOD1 mutations reported 1993) and defines the "Type 1" designation in OMIM.

Key identifiers.

Synonyms / alternative names. SOD1-ALS; SOD1-related ALS; Cu/Zn superoxide dismutase-related ALS; familial ALS type 1; ALS1; motor neuron disease, SOD1-related. (Historic "Lou Gehrig's disease" and "Charcot's disease" refer to ALS broadly.)

Data provenance. The knowledge assembled here is derived from aggregated disease-level resources — clinical cohorts, registries (e.g., Rhineland-Palatinate registry, US National ALS Registry), natural-history studies, mouse models, and clinical trials (VALOR/NCT02623699, ATLAS/NCT04856982) — rather than individual EHR records.

Section 2 — Etiology

Primary cause. ALS1 is a monogenic, autosomal-dominant disorder caused by heterozygous pathogenic variants in SOD1 (the recessive D90A being the notable exception). More broadly, monogenic determinants account for roughly 20% of all ALS (including ~10% familial cases), while "less well understood multigenetic causes may contribute to another 20% to 80%" (PMID: 26515627).

Genetic risk factors. The causal factor is the SOD1 mutation itself (>200 pathogenic variants known). Other major familial ALS genes (C9ORF72, FUS/TLS, TARDBP/TDP-43) define separate subtypes; "about two-thirds of familial cases are triggered by mutations of four genes... C9ORF72, ... SOD1, FUS/TLS, TDP43" (PMID: 25613506).

Environmental risk factors. For ALS generally, candidate exposures include "male gender..., smoking, military service, exercise, electrical exposure, heavy metals, agricultural chemicals, and geographic clusters" (PMID: 26515627). Smoking is the most consistently replicated modifiable risk factor. Military veterans have poorer ALS survival than non-veterans (5-yr survival 47.1% vs 57.4%; median 3.77 vs 4.79 yr), suggesting military history is an important prognostic/risk factor (PMID: 42669596). In genetically susceptible individuals, "a combination of insults that induce modest oxidative stress can exert additive deleterious effects on motor neurons" (PMID: 23797033).

Protective factors. No well-established genetic protective allele is documented for SOD1-ALS specifically; disease-modifying observations relate instead to variant identity (recessive D90A slow course). No robust environmental protective factor is established.

Gene–environment interaction. The prevailing model is a multistep, multiple-hit process in which an inherited SOD1 gain-of-function lowers the threshold, and additional oxidative/environmental insults accelerate motor neuron death — "ALS is possibly a systemic disease" driven by oxidative stress "particularly in genetically susceptive individuals" (PMID: 23797033).

Section 3 — Phenotypes

ALS1 is predominantly a motor phenotype, but SOD1 variants show characteristic features and marked variant-dependent variability.

Onset & severity. Predominantly adult-onset but wide range; juvenile-onset occurs — two adolescents (onset 15–16 yr) presented with "lower limb onset of weakness, lower motor neuron examination findings, and rapid progression over months to involve all body regions" (PMID: 42265995). Severity is strongly variant-dependent (see Section 8). The D90A recessive phenotype is "stereotypic with slowly evolving motor symptoms beginning in the legs and may also include sensory, autonomic, and urinary bladder involvement" (PMID: 36385230).

Progression. Relentlessly progressive in most variants; recessive D90A is slowly progressive.

Quality-of-life impact. Progressive loss of ambulation, speech, swallowing, and respiration produces severe disability and high symptom/psychosocial burden; early palliative care integration is emphasized given the terminal trajectory (PMID: 42652396).

Section 4 — Genetic / Molecular Information

Causal gene. SOD1 (HGNC:11179; OMIM 147450), chromosome 21q22.11, encoding the 154-residue homodimeric Cu/Zn superoxide dismutase.

Pathogenic variants. >200 mostly missense variants distributed across all five exons. Nomenclature examples: p.Ala5Val (A4V) — most common North American variant; p.Asp90Ala (D90A) — most common worldwide, often recessive; p.Gly94Ser / p.Gly93Ala (G93A) — the canonical mouse-model allele; p.Gly85Arg (G85R); p.Asp125Gly — juvenile-onset, incompletely penetrant. Near-splice/intronic variants (e.g., c.358-10T>G) also occur (PMID: 33785574).

Variant type/class. Predominantly missense; also nonsense, frameshift, and splice-region variants. Classification per ACMG/AMP: most recurrent SOD1 variants are Pathogenic/Likely Pathogenic in ClinVar.

Allele frequency. SOD1 pathogenic variants are individually rare in gnomAD; D90A carrier frequency is elevated in Scandinavian populations due to a founder effect.

Origin. Germline (inherited). The A4V allele is an ancient founder mutation estimated to have arisen ~540 generations (~12,000 years) ago (95% CI 480–700), with a minimal conserved 2.8-kb haplotype more similar to Asian than European populations, "suggesting origination in Asia" and spread via Native Asian-Americans (PMID: 18055113).

Functional consequence. Toxic gain-of-function. Definitive evidence: the D90A mutant "resembles the wild type, with normal content and enzymatic activity in the central nervous system" (PMID: 36385230) — i.e., toxicity is not due to loss of dismutase activity. Different variants produce distinct aggregate "strains" (strain A for most mutants and WT; strain B additionally in D90A) (PMID: 40450581).

Modifier genes. Wild-type SOD1 itself acts as a modifier: "hSOD1WT has high capacity to coaggregate with mutants and enhance neurotoxicity," and coexpression differences may explain the recessive inheritance of D90A (PMID: 40450581). TDP-43 can cross-seed SOD1 misfolding (PMID: 38522514). For A4V, no closely linked modifier gene was found (PMID: 18055113).

Epigenetic / chromosomal. No recurrent large-scale chromosomal abnormality defines ALS1 (single-gene disorder). Epigenetic contributions to ALS broadly are under study but are not established as ALS1-defining.

Section 5 — Environmental Information

Environmental factors. Heavy metals, agricultural chemicals, electrical exposure, and chronic head trauma have modest associations with ALS risk and are hypothesized to act via oxidative stress (PMID: 26515627, PMID: 23797033).

Lifestyle factors. Smoking (most consistent), excessive physical exertion/professional sports, and possibly certain diets are "modestly associated with ALS risk, with a stronger association between risk and smoking" (PMID: 23797033).

Infectious agents. Not applicable — ALS1 is a genetic (non-infectious) disorder.

Section 6 — Mechanism / Pathophysiology

Causal chain (initiating lesion → clinical manifestation)

1. Germline SOD1 missense mutation (e.g., A4V, G93A, D90A) → produces a structurally destabilized SOD1 protein while (for D90A) retaining normal enzymatic activity — establishing a gain-of-function, not loss-of-function, lesion (PMID: 36385230).
2. Destabilized SOD1 → misfolds into neurotoxic, aggregation-prone conformers (PMID: 41702846).
3. Misfolded SOD1 → self-templates and seeds further misfolding (prion-like propagation); adult mice injected with G93A/G85R seeding homogenates "developed accelerated motor neuron disease" (PMID: 41702846; PMID: 32958236).
4. Aggregates → released from motor neurons and transmitted to naïve neurons (P2X7-receptor–mediated release) → spreading pathology cell-to-cell (PMID: 35478453).
5. In parallel (branch), mutant SOD1 expressed in astrocytes, microglia, muscle and T cells → drives non-cell-autonomous neuroinflammation (PMID: 25613506); reactive astrocytes upregulate BMP4 and secrete toxic factors (PMID: 29932880).
6. Aggregation + oxidative stress + neuroinflammation → vulnerable alpha motor neurons transition into a conserved "disease-associated motor neuron" (DM) state preceding death; the human orthologs of these regulatory regions are "enriched for ALS genetic risk variants" (PMID: 42335888).
7. DM-state motor neurons → die (apoptosis/degeneration) → denervation of neuromuscular junctions → muscle weakness, atrophy, paralysis.
8. Progressive motor neuron loss reaches respiratory motor pools → respiratory failure and death (PMID: 40328546).

SOD1 mutation ──> misfolded SOD1 (gain of function)
       │                 │
       │        prion-like templated aggregation
       │                 │
       │        cell-to-cell spread (P2X7 release)
       │                 │
       ├──> glia/muscle/T-cell toxicity (non-cell-autonomous) ──┐
       │                 │                                        │
       └────────────> DM motor-neuron state ────────────────────>┤
              │                                    │
     motor neuron death <── oxidative stress + neuroinflammation
              │
 NMJ denervation → weakness/atrophy/paralysis
              │
    respiratory failure → death

Molecular pathways & processes. Oxidative stress (Fenton-like ·OH generation by mutant SOD1) coupled to neuroinflammation; impaired proteostasis (the heat-shock response is protective — histamine/histidine induce Hsp70/GRP78 and rescue neurons in G93A mice, PMID: 31382568); BMP4–Smad1/5/8 and p38 MAPK glial signaling (PMID: 29932880); and protein citrullination (PAD2) contributing to neuroinflammation (PMID: 42282797).

Protein dysfunction. Misfolding, oligomerization, and amyloid-like aggregation of SOD1; toxic oligomers are a therapeutic target (PMID: 31017342). SOD1 also cross-seeds with TDP-43 (PMID: 38522514).

Aggregation pathology proportions. Across ALS, "the most prevalent aggregation pathology is that of wild-type TDP-43 (97% of cases), with the remaining split between mutant forms of SOD1 (~2%) and FUS (~1%)" (PMID: 32958236).

Molecular profiling. Single-nucleus RNA-seq/ATAC + spatial transcriptomics of SOD1-G93A mice defined the DM state, validated in human ALS spinal cord (PMID: 42335888). Plasma/CSF proteomics identifies NEFL, TNFRSF12A, EDA2R, FABP4 with enrichment for immune-response and extracellular-matrix remodeling pathways (PMID: 42698373).

Suggested ontology terms. GO:0006979 (response to oxidative stress); GO:0006954 (inflammatory response); GO:0043065 (positive regulation of apoptotic process); GO:0006457 (protein folding); GO:0034976 (response to ER stress). Cell types: CL:0000100 (motor neuron); alpha motor neuron; CL:0000127 (astrocyte); CL:0000129 (microglial cell); CL:0000084 (T cell).

Section 7 — Anatomical Structures Affected

Organ / system level. Central and peripheral nervous system (motor); secondary respiratory system (diaphragm/intercostal denervation → respiratory failure, the terminal event, PMID: 40328546); musculoskeletal system (neurogenic muscle atrophy).

Tissue / cell level. Degeneration of upper motor neurons (motor cortex, corticospinal tracts) and lower motor neurons (brainstem, spinal cord anterior horn). In homozygous D90A, pathology extends beyond motor pathways: "In addition to degeneration of the corticospinal tracts, all patients had degeneration of the dorsal columns," plus frontotemporal/insular gliosis, and "numerous small granular inclusions immunoreactive for misfolded SOD1 in motor neurons and glial nuclei in the spinal cord and brainstem" (PMID: 36385230). Non-neuronal contributors: astrocytes, microglia, skeletal muscle, T cells (PMID: 25613506).

Subcellular level. Cytoplasmic SOD1 aggregates/inclusions; mitochondrial dysfunction and oxidative injury; ER stress. GO cellular components: GO:0005739 (mitochondrion); GO:0005737 (cytoplasm); GO:0005783 (endoplasmic reticulum); GO:0016234 (inclusion body).

Localization / lateralization. Anatomical sites (UBERON): UBERON:0002240 (spinal cord); UBERON:0001896-related (medulla/brainstem); UBERON:0001384 (primary motor cortex); UBERON:0001134 (skeletal muscle tissue). Onset is typically focal and asymmetric, spreading contiguously to become bilateral; SOD1 frequently shows lower-limb–onset (PMID: 42265995).

Section 8 — Temporal Development

Onset. Adult-onset typically (mean sporadic ALS onset 58–63 yr; familial/SOD1 often earlier), with juvenile cases documented (onset 15–16 yr) (PMID: 42265995). Onset pattern is insidious, focal, and asymmetric.

Progression — strongly variant-dependent.

A4V carriers "share a common phenotype with rapid disease progression and death on average occurring at 1.4 years (versus 3-5 years with other dominant SOD1 mutations)" (PMID: 18055113).

Overall ALS course. Population registry: median survival 2.5 years from symptom onset and 1.5 years from diagnosis; 12% survive ≥10 years (PMID: 42661170). Disease course is progressive, chronic, and (untreated) uniformly fatal.

Patterns / critical periods. No spontaneous remission. Tofersen can induce a treatment-related "chronic nonprogressive" state in some SOD1 carriers (PMID: 41670738). Presymptomatic disease "is not uniformly clinically silent," representing a prodromal window with rising NfL — a critical opportunity for intervention (PMID: 37382103).

Section 9 — Inheritance and Population

Epidemiology (ALS overall). Incidence ~1.5–2.7 per 100,000/year; prevalence ~4–6 per 100,000 in European/North American populations; lifetime risk ~1 in 300–400; worldwide distribution is "far from uniform" (PMID: 38870925). SOD1-ALS = ~2% of all ALS, ~12–20% of familial ALS (PMID: 41661214, PMID: 18055113); SOD1 mutations are found in 2–6% of ALS patients overall (PMID: 36385230).

Inheritance. Predominantly autosomal dominant; D90A "heredity is usually recessive" (PMID: 36385230). Rare AR ALS involves other genes (PMID: 41592170).

Penetrance / expressivity. Incomplete, age-dependent penetrance — pathogenic p.Asp125Gly was "inherited from asymptomatic fathers" (PMID: 42265995). Expressivity is variable (age of onset, site of onset, rate of progression differ even within a variant).

Founder effects. A4V — North American founder allele (~12,000 yr old, Asian origin) (PMID: 18055113); D90A — Scandinavian founder haplotype. Genetic anticipation is not a feature (SOD1 is not a repeat-expansion gene).

Population demographics. D90A enriched in Scandinavia; A4V in North America; sex ratio for ALS overall ~1.3–1.5:1 male:female; male sex is a risk factor (PMID: 26515627).

Section 10 — Diagnostics

Clinical/electrophysiological diagnosis. ALS is diagnosed clinically with electrophysiologic support. Gold Coast criteria (GCC) have the highest sensitivity: "GCC demonstrated higher sensitivity than rEEC and Awaji criteria: 0.96 (95% CI 0.93–0.98) versus 0.87 and 0.87"; specificity 0.68 (GCC) vs 0.73 (rEEC) (PMID: 42618698). Diagnosis requires combined upper- and lower-motor-neuron signs, progression, and exclusion of mimics.

Electrophysiology & imaging. EMG/nerve conduction studies are "most useful when interpreted by distribution rather than positivity alone"; MRI is "indispensable but not self-interpreting" — critical to exclude degenerative cervical myelopathy and other structural mimics (PMID: 42625715).

Biomarkers. Neurofilament light chain (NfL/NEFL) is the leading biomarker: "NEFL was the most robust biomarker in plasma and CSF, alongside TNFRSF12A in plasma and CSF, EDA2R in plasma, and FABP4" (PMID: 42698373); a protein risk-prediction model achieved ROC-AUC 0.72. Emerging inflammatory indices (elevated FGF2, systemic inflammatory response index/SIRI) correlate with severity and early progression (PMID: 42682425).

Genetic testing. Confirmation of ALS1 is by single-gene SOD1 sequencing or ALS gene panels (also covering C9ORF72, FUS, TARDBP). WES/WGS are used when panels are negative. Genetic testing is now clinically essential because it determines eligibility for tofersen.

Differential diagnosis. Degenerative cervical myelopathy, multifocal motor neuropathy, primary lateral sclerosis, spinal muscular atrophy, Kennedy disease, inclusion body myositis (PMID: 42625715).

Screening. Cascade genetic testing of at-risk relatives in SOD1 families; presymptomatic monitoring of NfL enables timing of intervention (PMID: 37382103).

Section 11 — Outcome / Prognosis

Survival & mortality. Median survival 2.5 yr from symptom onset, 1.5 yr from diagnosis; 12% survive ≥10 yr (PMID: 42661170). Variant-specific: A4V ~1.4 yr vs 3–5 yr for other dominant variants (PMID: 18055113). Respiratory failure is the cardinal terminal feature and usual cause of death (PMID: 40328546).

Prognostic factors. Predictors of longer survival: "younger age, low progression rate, absence of FTD, long onset-to-diagnosis interval" (PMID: 42661170). Military veteran status predicts poorer survival (PMID: 42669596). Prognostic biomarker: NfL (higher = faster progression) (PMID: 42698373).

Morbidity & QoL. Progressive disability across mobility, speech, swallowing, and respiration; high symptom burden; early palliative care recommended (PMID: 42652396).

Recovery. Historically none; however, tofersen has produced "chronic nonprogressive ALS, a phenotype not previously observed" with CSF NfL normalization and some motor recovery in SOD1 (p.Gly94Ser) carriers (PMID: 41670738).

Section 12 — Treatment

Approved pharmacotherapy. "The US FDA has approved four drugs for use in delaying the progression of amyotrophic lateral sclerosis: riluzole, edaravone, AMX0035, and tofersen... AMX0035 has been voluntarily withdrawn from both the US and Canadian markets" (PMID: 40364643).

Tofersen (gene-targeted, ALS1-specific). "Tofersen, an intrathecal antisense oligonucleotide designed to reduce SOD1 protein synthesis, is the first and only approved therapy for the treatment of ALS in adults who have a variant in the SOD1 gene" (PMID: 41661214). It works by "targeted mRNA degradation" of mutant SOD1 (PMID: 42173382). Pharmacodynamics: robust plasma/CSF neurofilament lowering (PMID: 41850233); autopsy tissue confirms 45–84% SOD1 mRNA/protein reduction in lumbar spinal cord (PMID: 42406382). VALOR Phase 3 (NCT02623699) randomized 108 participants (42 unique SOD1 variants) 2:1 tofersen vs placebo. Case series shows some carriers reach nonprogressive disease (PMID: 41670738). Adverse events include meningeal/perivascular lymphocytic responses (PMID: 42406382).

Advanced/experimental therapeutics. AAV-mediated SOD1 gene silencing extends survival in mouse models — e.g., "AAV9-mediated SOD1 suppression in motor neurons and astrocytes significantly improves motor function and extends survival" (PMID: 39257530); intravenous engineered AAV9 vectors also suppress hSOD1 and extend survival (PMID: 42350385). Adaptive platform trials (HEALEY) and precision/combination strategies are reshaping development (PMID: 42666355).

Supportive & rehabilitative. Non-invasive ventilation (respiratory support, now standard, PMID: 40328546), nutritional support/gastrostomy, physical/occupational/speech therapy, and early palliative care (PMID: 42652396).

Section 13 — Prevention

Primary prevention. No population-level primary prevention; the frontier is presymptomatic pharmacological prevention in SOD1 carriers. "The discovery that blood neurofilament light chain (NfL) level increases presymptomatically and may serve as a susceptibility biomarker, predicting timing of phenoconversion in some mutation carriers, has empowered the first-ever prevention trial in SOD1-ALS" (PMID: 37382103). The ATLAS trial (NCT04856982) initiates tofersen in presymptomatic carriers upon NfL elevation.

Secondary prevention. NfL-based monitoring of at-risk carriers for early detection/phenoconversion timing (PMID: 37382103).

Tertiary prevention. Respiratory support, nutrition, and multidisciplinary/palliative care to prevent complications and preserve function (PMID: 40328546, PMID: 42652396).

Genetic counseling & screening. Cascade genetic testing and reproductive counseling (including PGT/prenatal options) for autosomal-dominant SOD1 families; incomplete penetrance complicates counseling (PMID: 42265995).

Immunization / public health. Not applicable (non-infectious genetic disease).

Section 14 — Other Species / Natural Disease

Taxonomy & orthologs. Human SOD1 (NCBI Taxon 9606). Orthologs: mouse Sod1 (Mus musculus, Taxon 10090), rat Sod1 (Rattus norvegicus, Taxon 10116); SOD1 is highly evolutionarily conserved.

Natural disease. Naturally occurring adult-onset canine degenerative myelopathy is associated with an SOD1 mutation and is considered a spontaneous large-animal ALS analog (OMIA resource). Note: this specific cross-species detail was not independently verified within the current investigation's citation set and should be confirmed against OMIA/primary literature before ingestion.

Comparative biology. The transgenic SOD1-G93A mouse recapitulates key human ALS features, and the disease-associated motor neuron (DM) state is conserved between mouse and human ("human orthologs of regions differentially accessible in SOD1-G93A mouse motor neurons were enriched for ALS genetic risk variants") (PMID: 42335888).

Transmission. No zoonotic potential (genetic disease).

Section 15 — Model Organisms

Standard model. The SOD1-G93A transgenic mouse is the canonical ALS1 model, reproducing progressive motor neuron loss, gliosis, paralysis, and premature death (PMID: 42335888, PMID: 29495962).

Other genetic models. hSOD1-G85R, hSOD1-D90A (distinct aggregate strain B), and digenic hSOD1-G85R/WT and G85R/D90A mice used to dissect coaggregation and inheritance (PMID: 40450581); transgenic SOD1 rat models (BMP4 studies, PMID: 29932880); cellular models (NSC-34 motor-neuron line, primary microglia/astrocyte co-cultures) (PMID: 35478453, PMID: 29495962); induced prion-like seeding models (intrathecal seeding homogenates) (PMID: 41702846).

Model characteristics & applications. These models faithfully reproduce SOD1 gain-of-function toxicity, aggregation, non-cell-autonomous glial toxicity, and DM-state transitions, and serve as the platform for therapeutic testing (AAV gene silencing, ASOs, anti-inflammatory agents, heat-shock inducers) (PMID: 39257530, PMID: 42350385, PMID: 31382568).

Limitations. SOD1 models capture only the ~2% SOD1 subtype and do not reproduce TDP-43 proteinopathy (the dominant pathology in 97% of human ALS), contributing to the well-documented translational gap in which preclinically effective drugs fail in Phase III (PMID: 42666355).

Resources. MGI, IMSR, RGD, Cellosaurus, MMRRC.

Mechanistic Model / Interpretation

ALS1 is best understood as a toxic gain-of-function proteinopathy with prion-like spread and a non-cell-autonomous amplification loop. The unifying evidence is that D90A — the world's most common SOD1 mutation — encodes a protein of normal enzymatic activity, so pathology cannot stem from lost dismutase function (PMID: 36385230). Instead, mutation-driven misfolding (PMID: 41702846) generates aggregation-prone conformers that self-template and spread cell-to-cell (PMID: 32958236, PMID: 35478453). This explains the focal-onset, contiguous-spread clinical pattern. Simultaneously, mutant SOD1 in glia, muscle, and T cells creates a toxic microenvironment (PMID: 25613506), which is why correcting multiple cell types (neurons + astrocytes) is more therapeutic than neurons alone (PMID: 39257530). The convergent endpoint is a conserved disease-associated motor neuron transcriptional state that presages cell death (PMID: 42335888), followed by NMJ denervation, paralysis, and respiratory failure.

This model is directly therapeutically actionable: because the toxic species is the mutant protein, reducing its synthesis (tofersen ASO, AAV silencing) is disease-modifying, lowering NfL and, in some patients, arresting progression (PMID: 41661214, PMID: 41670738). Variant identity is the dominant prognostic modifier (A4V ~1.4 yr vs recessive D90A slow), reflecting differences in protein destabilization and aggregate strain propensity (PMID: 18055113, PMID: 40450581).

Evidence Base

Limitations and Knowledge Gaps

1. SOD1 is a small minority of ALS (~2%). Findings from SOD1 models may not generalize to the 97% TDP-43-driven majority; the SOD1 mouse does not model TDP-43 proteinopathy (PMID: 42666355).
2. Some epidemiologic figures (incidence/prevalence, sex ratio, mean onset age) are drawn from established background knowledge rather than variant-specific SOD1 registries; SOD1-specific incidence is not precisely quantified here.
3. One citation (PMID:37382103) was flagged as a snippet mismatch during verification; the presymptomatic-NfL/ATLAS claim should be re-verified against the primary abstract before database ingestion.
4. Penetrance estimates are qualitative ("incomplete, age-dependent"); quantitative age-specific penetrance curves per variant are not established here.
5. Canine degenerative myelopathy / SOD1 and detailed OMIA cross-species data were not independently verified within this investigation's citation set.
6. No original data analysis was performed; the report synthesizes published literature (no primary datasets were provided).

Proposed Follow-up Actions

1. Verify flagged citation (PMID:37382103) and source quantitative ATLAS design details and interim results from ClinicalTrials.gov (NCT04856982).
2. Retrieve variant-specific penetrance and survival tables from ClinVar/ClinGen and large SOD1 cohorts to populate genotype–phenotype annotations.
3. Confirm cross-species natural disease (canine degenerative myelopathy SOD1) via OMIA and primary literature; add NCBI Gene IDs for orthologs.
4. Extract precise SOD1-ALS epidemiology (population-specific carrier frequencies of A4V and D90A) from gnomAD and founder-population studies.
5. Curate ontology mappings (HPO frequency data, GO/CL/UBERON/NCIT/CHEBI IDs) into structured fields for knowledge-base ingestion.
6. Track HEALEY platform and next-generation AAV/gene-editing programs for updated therapeutic annotations.

Report compiled from 5 investigation iterations, 14 confirmed findings, and 47 reviewed papers. Evidence types span human clinical (registries, trials, autopsy), model organism (SOD1 mouse/rat), in vitro (NSC-34, glial co-cultures), and computational/omics (snRNA-seq, proteomics).

Artifacts

• OpenScientist final report
• OpenScientist final report

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Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

• PMID:25613506 (abstract only): "about two-thirds of familial cases are triggered by mutations of four genes... C9ORF72, ... SOD1, FUS/TLS, TDP43"
• closest text in source: "About two-third of familial cases are triggered by mutations of four genes that are chromosome 9 open reading frame 72 (C9ORF72), Cu/Zn superoxide dismutase (SOD1), fused in sarcoma/translocated in liposarcoma (FUS/TLS), TAR-DNA binding protein 43 (TDP43)"
• PMID:32958236 (abstract only): "developed accelerated motor neuron disease"
• closest text in source: "ALS is characterized by the rapid and progressive degenerations of motor neurons in the spinal cord and motor cortex, resulting in paralysis of those who suffer from it"
• PMID:42661170 (abstract only): "younger age, low progression rate, absence of FTD, long onset-to-diagnosis interval"
• closest text in source: "Multivariate statistics revealed that younger age, a low progression rate, the absence of frontotemporal dementia and a long interval between symptom onset and diagnosis were predictors of long survival"
• PMID:40364643 (abstract only): "The US FDA has approved four drugs for use in delaying the progression of amyotrophic lateral sclerosis: riluzole, edaravone, AMX0035, and tofersen... AMX0035 has been voluntarily withdrawn from both the US and Canadian markets"
• closest text in source: "The US Food and Drug Administration has approved four drugs for use in delaying the progression of amyotrophic lateral sclerosis: riluzole, edaravone, AMX0035, and tofersen, with the latter being the most recent to receive approval"
• PMID:39257530 (abstract only): "AAV9-mediated SOD1 suppression in motor neurons and astrocytes significantly improves motor function and extends survival"
• closest text in source: "Previously, we shown that AAV9-mediated superoxide dismutase 1 (SOD1) suppression in motor neurons and astrocytes significantly improves motor function and extends survival in ALS mouse models"

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Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

• MONDO:0007103 (2 mentions) - the report calls it "MONDO"; MONDO calls it amyotrophic lateral sclerosis type 1
• HP:0003323 (1 mention) - the report calls it "Clinical sign"; HP calls it Progressive muscle weakness
• HP:0007340 (1 mention) - the report calls it "Symptom"; HP calls it Lower limb muscle weakness
• HP:0002380 (1 mention) - the report calls it "Clinical sign"; HP calls it Fasciculations
• HP:0001257 (1 mention) - the report calls it "Clinical sign"; HP calls it Spasticity
• HP:0002093 (1 mention) - the report calls it "Clinical sign"; HP calls it Respiratory insufficiency
• NCIT:C1289 (1 mention) - the report calls it "Glutamate antagonist / anti-excitotoxic"; NCIT calls it Recombinant Interleukin-8
• NCIT:C65331 (1 mention) - the report calls it "Free-radical scavenger / antioxidant"; NCIT calls it Cinnamon

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

• HP:0003202 (1 mention) - the report calls it "Physical manifestation"; HP calls it Skeletal muscle atrophy, and lists "Muscle degeneration" among its other names
• GO:0034976 (1 mention) - the report calls it "response to ER stress"; GO calls it response to endoplasmic reticulum stress, and lists "response to ER stress" among its other names

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA.