C9orf72 and amyotrophic lateral sclerosis: While over 120 potential ALS genes (http://alsod.iop.kcl.ac.uk/) have been identified, more than half of familial ALS patients carry mutations in either ‘superoxide dismutase 1’ (SOD1), ‘TAR DNA binding protein’ (TARDBP), ‘fused in sarcoma’ (FUS), or carry a hexanucleotide repeat expansion in an intronic region of the ‘chromosome 9 open reading frame 72’ (C9ORF72) gene [190].