Researchers identified three classes of mutations: a homozygous exon 5 deletion, a homozygous Q398X nonsense mutation, and a heterozygous E478G missense mutation within the ubiquitin binding domain . it has identified optineurin as the gene responsible for amyotrophic lateral sclerosis. In patients with familial and sporadic amyotrophic lateral sclerosis (ALS), mutations in the gene encoding optineurin (OPTN) are present. Additionally, a novel deletion mutation of OPTN has been identified in Japanese ALS . In a Filipino ALS family, the mutant SOD1 allele can be naturally suppressed by enhanced splicing of exon 2, and novel SOD1 deletions result in low penetrance in ALS families . Familial ALS is the result of mutations in SOD1 that generate pseudoexons .