Since approximately 85% of mitochondrial proteins are encoded in the nucleus, synthesized on cytoplasmic ribosomes, and then imported into the mitochondria under the direction of a mitochondrial targeting sequence, we used “allotopic” expression to import a synthetic ND4 recoded in the nuclear genetic code that induced a phenotype resembling human LHON in mice [8]. The gene discussed is MT-ND4; the disease is Leber hereditary optic neuropathy.