Novel FUS/TLS Mutations and Pathology in Familial and Sporadic Amyotrophic Lateral Sclerosis

Objective To determine the frequency of and clinicopathologic phenotypes associated with FUS/TLS mutations in a large cohort of amyotrophic lateral sclerosis (ALS) cases from the north of England. Design Genetic screening project with neuropathologic examination of postmortem tissue in selected cases. The clinical details of selected cases are also presented. Setting Neurology departments of 2 university teaching hospitals in the north of England. Participants The 15 exons of FUS/TLS were sequenced in an initial cohort of 42 familial ALS (FALS) and 117 sporadic ALS (SALS) cases. Exons 14 and 15 were subsequently screened in a larger cohort of 431 SALS cases. Regions mutated in ALS cases were also screened in 293 controls. Main Outcome Measure Evaluation of gene-sequencing chromatographs and detailed histopathologic analysis of the central nervous system. Results Four heterozygous mutations, 1 of which is novel, were identified in 6 patients with ALS (4 with FALS and 2 with SALS). Two of the substitutions were not found to be present in controls, and neuropathology in these cases revealed neuronal and/or glial cytoplasmic inclusions positive for the FUS/TLS protein. One of these cases is also the first reported SALS case with an FUS / TLS mutation. The other 2 substitutions identified were also identified in control cases. Neuropathology in these cases revealed typical SALS pathology, suggesting that they are likely to represent benign polymorphisms. Conclusions FUS / TLS mutations represented approximately 5% of FALS cases screened. A FUS / TLS mutation was also identified in a single SALS case. Subsequent screening of this region in a larger cohort of SALS cases, however, did not reveal any additional mutations.