C9orf72 and amyotrophic lateral sclerosis: Familial ALS (fALS) includes mutations of Cu/Zn superoxide dismutase (Rosen, 1993), TAR-DNA-binding protein of 43 kDa (Neumann et al., 2006), fused in sarcoma (Fus) (Kwiatkowski et al., 2009; Vance et al., 2009) and amplification of hexanucleotide (GGGGCC) repeat expansions in the chromosome 9 open reading frame 72 (C9orf72) (DeJesus-Hernandez et al., 2011; Renton et al., 2011).