C9orf72 and amyotrophic lateral sclerosis: In contrast, myotonic dystrophy (DM), benign adult familial myoclonic epilepsy, fragile X syndrome, fragile X-associated tremor/ataxia syndrome, several types of SCA, and other nucleotide repeat expansion disorders possess more than 30–10,000 times expansion of short nucleotide repeats (such as CTG, CCTG, TTTCA, etc.)in non-coding regions, which then generate abnormal RNAs and proteins and cause cytotoxicity via both gain-of-toxic function and loss-of-function, similar to C9orf72-linked FTD/ALS [51].