C9orf72 and amyotrophic lateral sclerosis: It is important to elucidate the contribution of RNA toxicity in C9 ALS/FTD since RBPs, shown to interact with sense and antisense C9orf72 hexanucleotide repeat RNAs, are candidate modifying proteins of interest in the modulation of C9 ALS/FTD heterogeneity [12, 18, 25].