Familial ALS (approximately 10% of cases) is caused by various mutations in more than 20 genes (Sreedharan and Brown, 2013; Steinberg et al., 2015; Taylor et al., 2016), including Cu-Zn superoxide dismutase (SOD1, Bruijn et al., 1998), TAR DNA-binding protein of 43 kDa (TDP-43, Neumann et al., 2006), fused in sarcoma/translocated in liposarcoma (FUS/TLS Lagier-Tourenne et al., 2010) and the expansion of (G4C2) repeat in C9ORF72 (DeJesus-Hernandez et al., 2011). Here, SOD1 is linked to amyotrophic lateral sclerosis.