C9orf72 and amyotrophic lateral sclerosis: Since superoxide dismutase 1 (SOD1) was reported as the first ALS-associated gene in 1993 (Rosen et al., 1993), more than 25 genes have been described to be associated with ALS, including TAR DNA-binding protein 43 (TARDBP), fused in sarcoma (FUS), valosin-containing protein (VCP), and C9ORF72 (Nguyen et al., 2018).