FUS-associated ALS in Taiwan: genetic spectrum, clinical features, and a founder haplotype of p.H517D

To characterize the genetic spectrum and clinical features of FUS -associated amyotrophic lateral sclerosis (ALS) in a Taiwanese cohort and to investigate whether the recurrent p.H517D variant represents a founder mutation. All coding exons and flanking intronic regions of FUS were analyzed by Sanger sequencing in 650 unrelated Taiwanese patients with ALS. Clinical characteristics of patients carrying FUS variants were evaluated. Haplotype analysis using polymorphic microsatellite markers flanking FUS was performed to assess a potential founder effect of the p.H517D variant. Eight distinct heterozygous pathogenic FUS variants were identified in 11 probands and five affected relatives, including six missense and two frameshift variants. The most frequent variant was p.H517D, detected in four probands. A novel frameshift variant, p.G499Vfs*30, was identified as a de novo mutation in a juvenile-onset ALS patient. Compared with the non FUS -associated ALS cohort, patients with FUS -associated ALS had a significantly younger mean age at onset (40.1 vs 56.6 years) and more frequent bulbar onset (50% vs 19%). Haplotype analysis suggested a common founder for the p.H517D variant. FUS mutations accounted for 1.7% of ALS cases in this Taiwanese cohort. The recurrent p.H517D variant appears to represent a population-specific founder mutation. Patients with FUS variants presented with earlier disease onset and heterogeneous clinical phenotypes, and de novo variants contributed to juvenile-onset disease.