C9orf72 and amyotrophic lateral sclerosis: Healthy individuals carry up to 25 repeats of GGGGCC in c9orf72, with the majority having a couple of repeats, while in ALS and FTD cases the number of repeats ranges from 100s to 1000s (DeJesus-Hernandez et al., 2011; Renton et al., 2011; Beck et al., 2013).