C9orf72 and amyotrophic lateral sclerosis: The C9orf72 HRE variant is responsible for 30%–50% of familial ALS cases, 10% of sALS cases, and up to 50% of FTD cases (DeJesus-Hernandez et al., 2011; Renton et al., 2011; Cooper-Knock et al., 2015).