C9 and amyotrophic lateral sclerosis: In addition to the RNA foci, five dipeptide repeat protein (DRP) species, namely poly-glycine-alanine (poly-GA), poly-glycine-proline (poly-GP), poly-glycine-arginine (poly-GR), poly-proline-arginine (poly-PR), and poly-proline-alanine (poly-PA) are directly derived via repeat-associated non-AUG (RAN) translation from the C9-HRE-containing RNA and represent additional pathological hallmarks unique to C9-FTLD and C9-ALS (Zu et al., 2011, 2013; Ash et al., 2013; Gendron et al., 2013; Mori et al., 2013b).