NR4A2 and red color blindness: There were significantly fewer mtDNA methylations in patients with CBP than in healthy individuals in the following regions: RNR1, RNR2, TRNQ, TRNM, TRNW, TRNS1, ND2, ND5, CO1, CO2, CO3, ATP6 and CYB (all P < 0.05; Figure 1).