MT-ND4 and Atrophy: We then applied our MTS AAV technology to animals by testing for the presence and expression of the human ND4 gene in the adult rodent visual system that prevented visual loss and atrophy of the optic nerve induced by coadministration of a second AAV containing the allotopic human mutant ND4 allele; i.e., the arginine to histidine transition at amino acid 340 (R340H).