RAN and amyotrophic lateral sclerosis: The contribution of antisense repeat expanded RNAs to C9FTD/ALS pathogenesis is understudied, although overexpression of PR DPR proteins as those RAN translated from the antisense RNAs has been shown to be toxic in various model systems (Jovičić et al., 2015; Wen et al., 2014; Zhang et al., 2019).