C9orf72 and amyotrophic lateral sclerosis: Other mutations found in ALS patients include hexanucleotide expansion repeats in the C9orf72 locus, which lead to various dipeptide repeats (e.g., proline-arginine or glycine-arginine repeats: PR50 and GR50, respectively), and in the gene encoding the TDP43 RNA binding protein (Buratti, 2015; Wen et al., 2017).