Increased H3K9 methylation has been reported in C9orf72-ALS (Belzil et al., 2013; Walker et al., 2017), which might be driven by the aberrant accumulation of R-loops in ALS (Haeusler et al., 2014; Walker et al., 2017). Here, C9orf72 is linked to amyotrophic lateral sclerosis.