Whilst familial studies have established that mutations in a number of genes can cause ALS, mutations in C9orf72 (DeJesus-Hernandez et al., 2011), Superoxide Dismutase 1 (SOD1) (Rosen et al., 1993), TAR Binding-Protein 43 (TARDBP) (Neumann et al., 2006), Ataxin 2 (ATXN2) (Elden et al., 2010), and FUS (Vance et al., 2009; Table 2) are the most common. Here, ATXN2 is linked to amyotrophic lateral sclerosis.