For example, the pathogenic GGGGCC hexanucleotide repeat expansion (HRE) in the chromosome 9 open reading frame 72 (C9orf72) gene was identified as a common causative factor for ALS in Caucasian populations, accounting for 23.5–47% of familial ALS (3, 4) and 4.1–21.0% of sporadic ALS cases (5). Here, C9orf72 is linked to amyotrophic lateral sclerosis.