C9orf72 and amyotrophic lateral sclerosis: The first ALS gene, cytosolic superoxide dismutase (SOD1), was reported in 1993 [130] as well as other genes such as TAR DNA binding protein (TARDBP) [131,132,133,134], angiogenin (ANG) [135], fused in sarcoma (FUS) [35,36], optineurin (OPTN) [136], and the recently described chromosome 9 open reading frame 72 (C9orf72) [26,137].