FUS (Fused in Sarcoma) proteinopathy is a neurodegenerative mechanism characterized by the abnormal accumulation of the FUS protein in the cytoplasm of neurons and glia. This pathological process is a hallmark of certain forms of amyotrophic lateral sclerosis (ALS) and Frontotemporal Dementia (FTD)[1]. FUS is a 526-amino acid RNA-binding protein that plays critical roles in RNA metabolism, including transcription, splicing, transport, and translation. Under normal conditions, FUS predominantly localizes to the nucleus, but in FUS proteinopathy, the protein mislocalizes to the cytoplasm where it forms insoluble inclusions[2]. The discovery of FUS mutations as a cause of familial ALS in 2009 marked a significant breakthrough in understanding ALS pathogenesis. Approximately 5-10% of familial ALS cases and a smaller percentage of FTD cases are associated with FUS mutations[3].
FUS is a member of the FET (FUS, EWS, TAF15) family of RNA-binding proteins characterized by:
FUS is involved in:
Mutations in FUS cause loss of nuclear localization signals (NLS), leading to cytoplasmic accumulation. The most common ALS-associated mutations include:[4]
FUS undergoes liquid-liquid phase separation (LLPS) to form stress granules and other RNA-protein complexes. Disease-causing mutations alter the material properties of these condensates, promoting:[5]
FUS proteinopathy disrupts multiple aspects of RNA metabolism:
FUS inclusions disrupt nuclear pore integrity and impair nucleocytoplasmic transport, a mechanism shared with TDP-43 Proteinopathy and C9orf72-associated diseases.[6]
FUS-ALS is characterized by:[4:1]
FUS-positive inclusions are found in:[7]
FUS pathology has been reported in Alzheimer's Disease (less common), Parkinson disease (rare), and Huntington's Disease (co-pathology).
FUS proteinopathy can be distinguished from other ALS-FTD subtypes:
| Feature | FUS-ALS | TDP-43-ALS | SOD1-ALS |
|---|---|---|---|
| Age of onset | Younger (<40) | Variable | Variable |
| Progression | Rapid | Moderate | Variable |
| Cognitive involvement | Common | Common | Rare |
| FUS IHC | Positive | Negative | Negative |
🟡 Moderate Confidence
| Dimension | Score |
|---|---|
| Supporting Studies | 11 references |
| Replication | 0% |
| Effect Sizes | 25% |
| Contradicting Evidence | 0% |
| Mechanistic Completeness | 75% |
Overall Confidence: 40%
Deng H, Gao K, Jankovic J. The role of FUS gene in neurodegenerative disease. 2014. ↩︎
Ling SC, Polymenidou M, Cleveland DW. 'Converging mechanisms in ALS and FTD: disrupted RNA and protein homeostasis'. 2013. ↩︎
Suzuki N, Aoki M. FUS mutations in ALS and FTD. 2012. ↩︎
Kwok CT, Morris AG, Fratta P, et al. 'FUS-ALS: Clinical features and genetic heterogeneity'. 2020. ↩︎ ↩︎ ↩︎
Murakami T, Qamar S, Lin JQ, et al. ALS/FTD Mutation-Induced Phase Transition of FUS. 2015. ↩︎ ↩︎
Jovicic A, Mertens J, Boeynaems S, et al. Modifiers of C9orf72 dipeptide repeat toxicity connect nucleocytoplasmic transport defects to FTD/ALS. 2015. ↩︎
Dormann D, Haass C. 'TDP-43 and FUS: Nuclear protein aggregation'. 2011. ↩︎