C9orf72 and amyotrophic lateral sclerosis: Since the discovery of superoxide dismutase 1 (SOD1), the first gene associated with ALS in 1993, more than 20 other genes have been found to be causally or highly correlated with its pathogenesis, including transactive response DNA binding protein 43 kDa (TDP-43) [10], fused in sarcoma/transfer in liposarcoma (FUS), matrin 3 (MATR3), coiled-coil-helix-coiled-coil-helix domain containing 10 (CHCHD10), tank-binding kinase 1 (TBK1), tubulin, alpha 4A (TUBA4A), chromosome 21 open reading frame 2 (C21orf2), chromosome 9 open reading frame 72 (C9orf72), and cyclin F (CCNF), among others.