C9orf72 and amyotrophic lateral sclerosis: Of particular note, in 2011, the discovery of a pathogenic G4C2 hexanucleotide repeat expansion in a non-coding region of C9orf72 gene causing both ALS and FTD, strengthened the genetic link between these neurodegenerative disorders (DeJesus-Hernandez et al., 2011; Renton et al., 2011).