The latter form is believed to be due to several genes including SOD1, TARDBP, FUS, OPTN, and VCP. In addition, a hexanucleotide (GGGGCC) repeat expansion in the first intron of the C9ORF72 gene (DeJesus-Hernandez et al., 2011; Renton et al., 2011) has lately been demonstrated as being associated with ALS. Here, SOD1 is linked to amyotrophic lateral sclerosis.