In addition, in vivo experiments show that SOD1-D91A (p.Asp91Ala), the most common mutation affecting SOD1 linked to ALS, is less toxic than other tested mutants, while homozygous mice develop fatal motor neuron disease similar to that observed in homozygous-D91A human ALS patients [41,43]. The gene discussed is SOD1; the disease is amyotrophic lateral sclerosis.