Genotype-phenotype association and functional analysis of mutations in amyotrophic lateral sclerosis.

BACKGROUND

Pathogenic variants in have been reported in amyotrophic lateral sclerosis (ALS) patients. However, studies on mutant spectrum and pathogenicity of variants were rare.

METHODS

We performed whole exome sequencing of ALS-associated genes and subsequent verification of rare variants in in our ALS patients. The mutations reported in literature were reviewed and combined with our results to determine the genotype-phenotype relationship. Functional analysis of the novel variant p.G195A was performed in vitro by transfection of mutant into 293T cell.

RESULTS

Among 207 ALS patients recruited, 3 rare variants were identified (mutant frequency 1.45%), including two recurrent mutations (p.P340S and p.G283R), and a novel rare variant p.G195A. In combination with previous reports, there are 27 ALS patients with 15 mutations identified. Disease onset age was 47.90 ± 1.52 years with predominant limb onset. The p.P340S mutation caused flail arm syndrome (FAS) in two independent families with extended life expectancy. The newly identified p.G195A mutation, lying at the start of the PrLD ("prion-like" domain)/LCD (low-complexity domain), causes local structural changes in 3D protein prediction. Upon sodium arsenite exposure, mutant hnRNPA1 retained in the nucleus but deficit of cytoplasmic G3BP1-positive stress granule clearance was observed. This is different from the p.P340S mutation which caused both cytoplasmic translocation and stress granule formation. No cytoplasmic TDP-43 translocation was observed.

CONCLUSION

Mutations in are overall minor in ALS patients. The p.P340S mutation is associated with manifestation of FAS. Mutations in LCD of cause stress granule misprocessing.