Pathogenic Effect of Gene Variants in People With Amyotrophic Lateral Sclerosis.

Objective: To identify novel disease associated loci for amyotrophic lateral sclerosis (ALS), we used sequencing data and performed in vitro and in vivo experiments to demonstrate pathogenicity of mutations identified in .

Methods: We analyzed exome sequences of 87 patients with sporadic ALS and 324 controls, with confirmatory sequencing in independent ALS cohorts of >2,800 patients. For the top hit, , a regulator of apoptosis and differentiation and a binding partner and homolog of the tumor suppressor gene , we assayed mutation effects using in vitro and in vivo experiments. C2C12 myoblast differentiation assays, characterization of myotube appearance, and immunoprecipitation of p53-p73 complexes were performed in vitro. In vivo, we used clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 targeting of zebrafish to assay motor neuron number and axon morphology.

Results: Four heterozygous rare, nonsynonymous mutations in were identified in our sporadic ALS cohort. In independent ALS cohorts, we identified an additional 19 rare, deleterious variants in . Patient mutations caused abnormal differentiation and increased apoptosis in the myoblast differentiation assay, with abnormal myotube appearance. Immunoprecipitation of mutant ΔN-p73 demonstrated that patient mutations hinder the ability of ΔN-p73 to bind p53. CRISPR/Cas9 knockout of in zebrafish led to impaired motor neuron development and abnormal axonal morphology, concordant with ALS pathology.

Conclusion: Together, these results strongly suggest that variants in correlate with risk for ALS and indicate a role for apoptosis in ALS disease pathology.