C9orf72 and amyotrophic lateral sclerosis: Additionally, the expanded G4C2 hexanucleotide repeat in the C9orf72 gene, the most frequent genetic mutation in ALS, might impact the proper regulation of RNA metabolism, as a result of both the accumulation of RNAs containing the expansion, that might disrupt the activity of a number of RNA binding proteins (RBPs), and the expansion-driven production of poly-dipeptides (dipeptide repeat proteins, DPRs), that accumulate in cells and affect the proper intracellular trafficking of RNAs (Wen et al., 2017).