C9orf72 and amyotrophic lateral sclerosis: Three mechanisms by which a repeat expansion in chromosome 9 open reading frame 72 (C9ORF72) might be causative of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) [11, 31] are a loss of C9ORF72 expression [11], the formation of dipeptide-repeat proteins aberrantly translated from the repeat [2, 27], and the generation of RNA foci containing flawed RNA transcripts [11].