Our previous study, along with others, suggested that two arginine‐rich DPRs, poly‐GR and poly‐PR, can localize to the nucleolus and are most toxic in cells and animal models (Mizielinska et al., 2014; Tao et al., 2015), suggesting that RAN‐translated DPR toxicity contributes to disease pathogenesis of C9orf72‐linked ALS/FTD. Here, RAN is linked to frontotemporal dementia.