NDP and Leber hereditary optic neuropathy: Thus far, LHON-causing mutations were mostly located in the mitochondrial MT-ND genes encoding subunits of Complex I. Although they affect highly conserved residues of subunit a, equivalents of m.9016A>G and m.9139G>A had no obvious detrimental effects on the activity and assembly/stability of the yeast ATP synthase, which casts in doubt their potential, at least alone, to impair vision.