Furthermore, maternally transmitted CV deficiency can be caused by mutations in the two mtDNA genes MTATP6 or MTATP8. Heteroplasmic missense mutations in MTATP6 [125,126] are associated with adult-onset NARP (neuropathy, ataxia, and retinitis pigmentosa) or maternally inherited LS (MILS). This evidence concerns the gene MT-ATP6 and NARP syndrome.