MT-ND4 and Leber hereditary optic neuropathy: Besides the nuclear DNA (nDNA) encoded subunits, aberrant mtDNA-encoded components, MT-ND1, MT-ND3, MT-ND4, MT-ND5, and MT-ND6, caused the dysfunction of CI that is also involved in the pathomechanism of neurological disorders, such as LS and Leber hereditary optic neuropathy (LHON; Catarino et al., 2017; Lee et al., 2020; Bakare et al., 2021).