The most common forms of familial and sporadic ALS and FTD, referred to as c9ALS/FTD, are caused by a non-coding GGGGCC (G4C2) hexanucleotide repeat expansion in the C9orf72 gene on chromosome 9p21 [1, 2]. This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.