C9orf72 and amyotrophic lateral sclerosis: Association between the C9ORF72 gene and ALS was observed in 2011 by two independent teams (9, 27) who identified a pathogenic G4C2 HRE in the intron 1 of the chromosome 9 open reading frame 72 gene, separating the non-coding first exons 1a and 1b.