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Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting upper and lower motor neurons. While approximately 5-10% of ALS cases are familial (genetic), the majority (~90-95%) are sporadic, occurring in individuals without a known family history. Understanding what initiates sporadic ALS remains one of the greatest challenges in neurodegenerative disease research[1].
Sporadic ALS and familial ALS share similar clinical presentations and pathological features, but differ in their underlying causes:
| Feature | Sporadic ALS | Familial ALS |
|---|---|---|
| Proportion | ~90-95% of cases | ~5-10% of cases |
| Onset | Typically 55-65 years | Typically earlier (40-60 years) |
| Genetic cause | Unknown in most cases | Known mutations (SOD1, C9orf72, FUS, TARDBP) |
| Risk factors | Age, environmental exposures | Inherited mutations |
The convergence of both sporadic and familial ALS on similar clinical and pathological phenotypes suggests common downstream mechanisms, even if the initiating events differ[2].
RNA metabolism defects are increasingly recognized as central to ALS pathogenesis. Key observations include:
Stress granules are cytoplasmic RNA-protein assemblies that form in response to cellular stress. In ALS:
Motor neurons have extremely long axons requiring robust cytoskeletal support:
Mitochondria are essential for neuronal survival:
Non-neuronal cells play critical roles in ALS progression:
Recent studies have advanced our understanding of ALS initiation:
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Zhang K, Daigle JG, Cullen KM, et al. Stress granule assembly disrupts nucleocytoplasmic transport. Nature. 2018. ↩︎