To determine the effects of mitochondrial targeting sequence (MTS) modified AAV gene delivery of wild-type human NADH dehydrogenase subunit 4 (ND4), mutated in most cases of the blinding disease Leber hereditary optic neuropathy (LHON), on the host mouse mitochondrial genome. The gene discussed is MT-ND4; the disease is Leber hereditary optic neuropathy.