MT-ND6 and Leber hereditary optic neuropathy: In the past ten years, a variety of point mutations of ND6 gene were showed to affect NADH dehydrogenase activity [15-18] leading to NADH dehydrogenase deficiency, and were associated with maternally inherited diseases such as Leber’s hereditary optic neuropathy (LHON) [15,16] and mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) [17,18].