COX4I2 and diabetes mellitus: This was clearly established using immunostaining against TOMM20 (a translocator of the OMM), which delineated the whole mitochondrial network at the outer retina (Figure 2, F–I).Moreover, no changes of Cox4 mRNA levels (Cox4i1 and Cox4i2 isoforms) were detected in 2-month and 8-month-old hyperglycemic Ins2Akita/+ retinas (as compared with age-matched controls, Supplemental Figure 3), suggesting that mitochondrial changes occur due to an altered mitochondrial turnover in diabetes.