Therefore, in this study, we tried to elucidate the role of the NDUFS4 (OMIM:602694 GenBank accession no: NM_002495 Protein accession no: O43181) nuclear encoding gene in LHON pathogenesis by analyzing the various histone modifications in LHON patients carrying ND4 mutations and in ND4 mutant cell lines. The gene discussed is NDUFS4; the disease is Leber hereditary optic neuropathy.