C9orf72 and frontotemporal dementia: After C9orf72, mutations in SOD1 (20% of FALS), TARDPB encoding TDP-43 (5% of FALS, >50% of FTD) (Rutherford et al., 2008; Sreedharan et al., 2008; Borroni et al., 2010; Kirby et al., 2010), Fused in sarcoma encoding FUS (FUS, 5% of FALS) (Belzil et al., 2009; Blair et al., 2009; Chiò et al., 2009; Kwiatkowski et al., 2009; Neumann et al., 2009; Vance et al., 2009), and CCNF encoding cyclin F (0.6–3.3% of FALS-FTD) are more frequent than the remaining 20 genes mutated in the much rarer forms of FALS (Supplementary Table 1).