C9orf72 and amyotrophic lateral sclerosis: Recent findings demonstrate that an expanded non-coding hexanucleotide (GGGGCC) repeat in the chromosome 9 open reading frame 72 gene (C9orf72, OMIM *614260) is the most common known cause of FTD and ALS, collectively referred to as c9FTD/ALS [16, 36].