MT-ND4 and hereditary optic atrophy: In this report, we describe redirection of the adeno-associated virus (AAV) virion to mitochondria by adding an MTS to the viral outer capsid to deliver the mutant G11778A human ND4 gene in the mitochondrial genetic code to the visual system of mice where the mutant ND4 allele induced retinal ganglion cell (RGC) dysfunction and optic atrophy.