For instance, mitochondrial disorders include Leber's hereditary optic neuropathy (LHON) where a point mutation occurs in one of the genes coding for protein subunits forming the NADH dehydrogenase enzyme, affecting the activity of oxidative phosphorylation complex I located in the mitochondrion inner membrane (nucleotide positions 11778 G to A, 3460 G to A and 14484 T to C, respectively in the ND4, ND1 and ND6 subunits) and eventually causing optic atrophy. The gene discussed is MT-ND4; the disease is Leber hereditary optic neuropathy.