ALS Risk and Your Genetics

By the ExomeDNA Research Team | Last reviewed: 2026-05-25

This page is for informational purposes only. For health decisions, consult a clinician.

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is a progressive neurodegenerative condition affecting the motor neurons that control voluntary muscle movement. It is a rare disease — affecting roughly 2 to 3 people per 100,000 globally — and its causes involve a complex interplay of genetic susceptibility, environmental exposures, and aging-related cellular stress. The vast majority of ALS cases are classified as sporadic, meaning no single causal mutation is identified.

What is amyotrophic lateral sclerosis?

ALS affects both upper motor neurons (in the brain and spinal cord) and lower motor neurons (connecting the spinal cord to muscles), producing progressive weakness, spasticity, and eventually respiratory failure. Most individuals with ALS present in middle to late adulthood, and the disease follows an aggressive course. Approximately 10 percent of ALS cases are familial, caused by highly penetrant mutations in genes such as C9orf72, SOD1, TARDBP, and FUS. The remaining 90 percent are sporadic, and these cases are thought to arise from the accumulation of many genetic risk factors — common variants across multiple loci — in combination with environmental and aging-related triggers.

Genome-wide association studies of ALS have identified common variants associated with modest increases in susceptibility. These variants are not diagnostic and do not cause ALS in the way that rare familial mutations do — rather, they represent genetic influences that may shift population-level risk. Most individuals carrying these common variants do not develop ALS.

The genetics behind ALS

The genetic loci associated with ALS susceptibility through population-level studies span a diverse set of biological functions — from RNA metabolism and protein quality control to DNA repair and calcium signaling. Several of the genes implicated connect to broader neurodegeneration biology.

ATXN1 — RNA metabolism and protein aggregation

ATXN1 encodes ataxin-1, a protein whose polyglutamine expansion causes spinocerebellar ataxia type 1 (SCA1). Beyond the repeat expansion, ataxin-1 is a nuclear RNA-binding protein involved in gene expression regulation and RNA processing. Research has revealed that ATXN1 physically interacts with TDP-43 — the RNA-binding protein that misfolds and aggregates in the motor neurons of the majority of ALS cases. Common variants near ATXN1 have been identified in ALS GWAS as potential susceptibility signals, suggesting that alterations in ATXN1-related RNA metabolism may modulate motor neuron vulnerability.

ATXN3 — deubiquitinase and protein quality control

ATXN3 encodes ataxin-3, a deubiquitinase whose polyglutamine expansion causes spinocerebellar ataxia type 3 (SCA3/Machado-Joseph disease). The deubiquitinase activity of ATXN3 is essential for regulating the ubiquitin-proteasome system — the cellular machinery responsible for clearing misfolded proteins. Impaired protein quality control is a central feature of ALS pathology: TDP-43, FUS, and SOD1 proteins all aggregate in motor neurons when clearance is compromised. Variants near ATXN3 that influence its deubiquitinase function may therefore affect the capacity of motor neurons to handle misfolded protein stress.

APTX — DNA repair in vulnerable neurons

APTX encodes aprataxin, a DNA repair enzyme that resolves abortive DNA ligation intermediates — a specific type of DNA damage that arises during base excision repair. Loss-of-function variants in APTX cause ataxia-oculomotor apraxia type 1 (AOA1), a rare progressive ataxia characterized by cerebellar and peripheral motor neuron degeneration. The overlap between APTX-related neuropathology and ALS phenotype points to DNA repair fidelity in post-mitotic neurons as a potential contributor to motor neuron disease susceptibility.

ACSL5 — fatty acid activation and mitochondrial energy supply

ACSL5 encodes acyl-CoA synthetase long-chain family member 5, which converts long-chain fatty acids into their acyl-CoA derivatives for entry into beta-oxidation and phospholipid synthesis. Motor neurons have exceptionally high energy demands and are vulnerable to mitochondrial dysfunction. Disruption of fatty acid activation and the associated mitochondrial energy supply has been proposed as a contributing mechanism in ALS, and variants near ACSL5 may affect this metabolic vulnerability.

ALDH1A2 — retinoic acid synthesis in motor neuron development

ALDH1A2 encodes an aldehyde dehydrogenase responsible for synthesizing retinoic acid — a signaling molecule critical for spinal motor neuron specification during embryonic development and for maintaining neuronal identity in adulthood. Disruption of retinoic acid signaling has been associated with motor neuron pathology in experimental models, and variants near ALDH1A2 may influence the retinoic acid environment in spinal cord tissue.

CAMK1G — calcium signaling and neuronal survival

CAMK1G encodes calcium/calmodulin-dependent protein kinase 1 gamma, an intracellular kinase activated by calcium signaling. Calcium dysregulation is a recognized feature of motor neuron degeneration in ALS — motor neurons are particularly susceptible to excitotoxic calcium overload due to their high expression of calcium-permeable AMPA receptors and low calcium-buffering capacity. Variants near CAMK1G may influence neuronal calcium handling and downstream survival signaling.

CABIN1, ACTR3B, B4GALT6, CENPV — additional susceptibility loci

CABIN1 (calcineurin-binding protein 1) modulates calcineurin phosphatase activity, a regulator of neuronal apoptosis and survival. ACTR3B is involved in branched actin cytoskeleton dynamics important for axonal integrity and transport. B4GALT6 encodes a galactosyltransferase involved in glycolipid synthesis, with potential roles in neuronal membrane stability. CENPV (centromere protein V) participates in chromosome segregation; its connection to ALS susceptibility likely reflects pleiotropic effects at its genomic locus.

What the research says

Schymick et al. (2007) published one of the first genome-wide association studies of ALS, performing genotyping across thousands of individuals with ALS and neurologically normal controls. This landmark study constituted a first-stage scan and established a public data repository that has supported subsequent large-scale ALS genetic research. The study identified nominal associations at multiple loci, contributing to the understanding that ALS susceptibility involves common genetic variation distributed across the genome.

First genome-wide ALS scan Schymick et al. (2007) performed one of the earliest genome-wide genotyping studies in ALS, identifying nominal susceptibility signals and releasing the dataset publicly — foundational infrastructure for subsequent meta-analyses and replication studies in motor neuron disease genetics.^[¹]

Subsequent ALS GWAS meta-analyses, building on the public data infrastructure established by early studies, have identified genome-wide significant loci and refined understanding of the polygenic architecture of ALS susceptibility. Common variants individually confer very small increases in risk; their aggregate effects, combined with rare penetrant variants, shape population-level ALS genetics.

Polygenic susceptibility architecture Large-scale ALS genetic research has established that susceptibility involves common variants distributed across loci spanning RNA metabolism, protein quality control, DNA repair, and calcium signaling pathways — consistent with the multi-mechanism nature of motor neuron degeneration.^[¹]

Research base: Robust.

How ALS risk affects you

Common genetic variants associated with ALS susceptibility confer modest population-level risk shifts rather than determining individual outcomes. ALS is a rare disease, and the baseline probability of developing it over a lifetime is low — typically estimated below 0.5 percent in the general population. Common susceptibility variants individually contribute risk changes of a fraction of a percent, meaning that carrying several such variants does not substantially elevate personal risk in absolute terms.

The situation is different for individuals with rare, highly penetrant familial ALS mutations (such as C9orf72 hexanucleotide repeat expansions), which are not captured by common-variant analysis. These require dedicated clinical genetic testing through a physician or neurologist. The common variants discussed on this page represent population genetics research findings, not clinical genetic testing results.

For individuals with a family member affected by ALS, clinical genetics referral through a healthcare provider offers the appropriate pathway for assessing familial risk through targeted molecular testing.

Working with your genetic profile

ALS genetic research remains an active and evolving field. The loci identified through GWAS represent biological hypotheses about motor neuron vulnerability rather than clinical predictors. No currently available intervention is proven to prevent ALS in those with common susceptibility variants.

For the general population, the most evidence-based approach to brain health includes regular physical activity, cardiovascular risk management, adequate sleep, and avoiding smoking and excessive alcohol — factors associated with general neurological resilience. For those with personal or family history of ALS, a neurologist or clinical geneticist is the appropriate source of personalized guidance.

ALS research is advancing rapidly, with ongoing clinical trials targeting TDP-43 pathology, SOD1, and other molecular mechanisms. Staying informed through patient advocacy organizations can help individuals with personal connections to ALS access current research and emerging opportunities.

Related traits and genes

• Frontotemporal Dementia — shares TDP-43 pathology with ALS; C9orf72 expansions cause both conditions in the ALS-FTD spectrum
• Parkinson's Disease — another progressive neurodegenerative condition with genetic risk factors across shared pathways
• Spinocerebellar Ataxia — ATXN1 and ATXN3 cause SCA1 and SCA3 when mutated; common variants near these genes appear in ALS GWAS
• Cognitive Decline — motor neuron disease may overlap with cognitive pathways through shared protein aggregation mechanisms

Frequently asked questions

What is the difference between sporadic and familial ALS?

Familial ALS accounts for approximately 10 percent of cases and involves highly penetrant mutations — particularly in C9orf72, SOD1, TARDBP, and FUS — that cause disease with high probability when inherited. Sporadic ALS comprises the remaining 90 percent of cases, where no single causal mutation is identified; susceptibility in sporadic cases likely reflects the combination of many common variants across multiple loci, plus environmental and aging-related factors. The genetic analysis on this page reflects common-variant susceptibility research relevant to population-level risk.

Why do ATXN1 and ATXN3 appear in ALS genetics?

ATXN1 and ATXN3 are best known for their roles in spinocerebellar ataxias when their polyglutamine tracts expand. However, common variants near these genes — not the repeat expansions — have appeared in ALS genome-wide studies as susceptibility signals. Both proteins participate in pathways highly relevant to ALS: ATXN1 interacts with TDP-43 in RNA metabolism, while ATXN3 is a deubiquitinase that regulates clearance of misfolded proteins — the same misfolded proteins that accumulate in ALS motor neurons.

How rare is ALS?

ALS affects approximately 2 to 3 individuals per 100,000 in the general population at any given time, making it a rare disease. Lifetime risk is estimated at less than 0.5 percent for the general population. Common genetic susceptibility variants identified by GWAS contribute very small individual risk increments; no currently available test can predict whether a specific individual will develop ALS based on common variant profiles alone.

Can lifestyle factors influence ALS risk?

Some research has associated certain environmental exposures with ALS risk — including prolonged intense physical exertion in occupational contexts, military service, and possibly heavy metal exposure — though the evidence is not conclusive and the effect sizes are modest. Protective factors are less well established. General neurological health maintenance (cardiovascular fitness, sleep, avoiding smoking) reflects the best current evidence for modifiable influences on brain health broadly.

What should someone with a family history of ALS do?

Individuals with a first-degree relative with a family history of ALS — particularly if onset occurred before age 60 or if multiple family members are affected — may benefit from consultation with a neurologist or clinical geneticist. Clinical genetic testing through medical channels can assess for known high-penetrance ALS mutations. The common-variant research discussed on this page is not equivalent to clinical genetic testing and does not evaluate familial mutation status.

This page is for informational purposes only and is not a clinical determination, treatment recommendation, or clinical genetic test.