C9orf72 and amyotrophic lateral sclerosis: To date, there are more than 50 ALS-linked genes, including those that encode superoxide dismutase 1 (SOD1), chromosome 9 open reading frame 72 (C9ORF72), transactive response DNA-binding protein 43 (TDP-43) encoding gene (TARDBP), and the fused in sarcoma (FUS) gene (Paez-Colasante et al, 2015).