EPHA4 and amyotrophic lateral sclerosis: Many familial ALS cohorts carry mutations in the superoxide dismutase-1 (SOD1), TDP-43 (TARDBP) or fused in sarcoma (FUS) genes; however, the number of genes associated with ALS continues to grow, and is now at least 32, including C9orf72 and EphA4, indicating the extent of heterogeneity of the disease (Sreedharan and Brown, 2013).