Several ALS2 gene mutations have been identified, but only four (261delA, 553delA, G660A, and 1130delAT) were found in the RCC1 domain region expected to affect the protein, with the two mutations nearest to the amino-terminus (261delA and 553delA) resulting in frame shift mutations responsible for the development of juvenile ALS termed ALS type 2 (ALS2) [144,145,146]. The gene discussed is ALS2; the disease is amyotrophic lateral sclerosis.