It has been identified that the C9orf72 gene mutation, characterized by the hexanucleotide repeat expansions (HREs) of GGGGCC (G4C2)n sequence located in the first non-coding region of C9orf72 gene, is the most common genetic cause of familial ALS and FTD (5–7). Here, C9orf72 is linked to amyotrophic lateral sclerosis.