There are now mutations in > 20 genes identified as causative in ALS [2], of which the most common are mutations in SOD1, the RNA binding protein encoding genes TARDBP and FUS, and the recently identified C9orf72. Repeat expansions of C9orf72 have also been associated with neurodegeneration elsewhere in the central nervous system (CNS), within and outside of the motor system, as will be explored below. This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.