In 2011, the discovery of a hexanucleotide (GGGGCC) repeat expansion mutation in C9orf72 finally explained the genetic link to the ninth chromosome in cases with ALS and FTD (DeJesus-Hernandez et al., 2011; Renton et al., 2011). The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.