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Any biological process needs chemical energy. A major contemporary challenge in biomedical science is the topic of chemical energy supply in nervous system. In fact Retina and Central Nervous System (CNS) have an immense energy and oxygen demand. Myelin sheath is the multilayered glial membrane surrounding axons, for which a trophic role has been hypothesized.
Vision starts with light absorption by extremely specialized cells, i.e. the rods and cones of the retina. By immunohystochemical imaging studies with Confocal Laser and Transmission Electron Microscopy and classical biochemical techniques we have shown that the electron transport chain and F1F0-ATP synthase are functional in retinal rod outer segments and isolated myelin vesicles of the central nervous system, for aerobic ATP production, suggesting that myelin sheath and rod outer segments are the site of oxidative phosphorylation (OXPHOS).
The OXPHOS proteins would undergo a normal biogenesis in mitochondria, then be transferred "ready-to use" to the new locations, likely by fusion that may involve endoplasmic reticulum. Targeting of selected mitochondrial proteins to subcellular locations characterized by high energy demand and are relative scarcity of mitochondria may not even be peculiar of SNC and retina, rather be an evolutionary pivotal step towards a capillary use of ATP.
Strengths of these studies include solid biochemical data and exclusion of mitochondrial contamination, and ex vivo studies of the optic nerve and retina with classical fluorescent mitochondrial probes that stain IMV optic nerve sections and rod OS. Mitochondrial disorders, i.e. genetic errors in nuclear and mitochondrial genome that primarily affect retina and CNS.