To investigate the effect of NDUFS4 mutation found in some LS patients, such as NDUFS4 c.20C>G mutation, we generated NDUFS4-mutant by introducing the knock-in c.20C>G mutation in the NDUFS4 on both alleles of normal iPS to create Ndufs4-mutant iPS. The gene discussed is NDUFS4; the disease is Leigh syndrome.