For example, the most common genetic cause of ALS, responsible for 40% of fALS and 8% sALS, is a G4C2 hexanucleotide repeat expansion (HRE) in the first intron of the C9ORF72 gene (hereafter referred to as C9-ALS) [7]. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.