MT-CYB and Leber hereditary optic neuropathy: For example, m.15257G>A that causes a D to N substitution at position 171 (p.Asp171Asn) of the MT‐CYB polypeptide [Heher and Johns, 1993; Johns and Neufeld, 1993; Johns et al., 1993] is associated with Leber hereditary optic neuropathy (LHON) and a number of different disease cohorts, whereas m.14798T>C that causes a phenylalanine to leucine amino acid substitution in MT‐CYB (p.Phe18Leu) is frequently found in patient‐derived glioblastoma biopsy cells [Kirches et al., 2001; Larman et al., 2012; Lloyd et al., 2015], but biochemical data are often lacking.