Neuroscience
A gain-of-function Retsat variant from high-altitude adaptation promotes myelination via a neuronal dihydroretinoic acid-RXR-gamma pathway
Researchers discovered that a genetic variant evolved in high-altitude animals supercharges a neuron-to-oligodendrocyte signaling pathway, revealing a new therapeutic target for myelin diseases like multiple sclerosis.
Imagine your brain's nerve fibers are like electrical cables, and the insulation around them is called myelin. Without good insulation, signals get scrambled or lost, causing problems with movement, thinking, and sensation — which is what happens in diseases like multiple sclerosis. Scientists noticed that animals living at high altitude, where oxygen is scarce, evolved a genetic tweak that helps their brains maintain better insulation, perhaps as a protective response to low-oxygen stress. They found the specific gene change responsible (called Q247R in a gene called Retsat) and figured out exactly how it works: the altered gene makes neurons produce more of a vitamin A-related molecule called ATDR, which neurons then send out as a chemical message to neighboring brain cells called oligodendrocytes (the cells that actually make myelin), telling them to grow and wrap more insulation around nerve fibers. When scientists gave this ATDR molecule to mice with myelin damage, their brains repaired the insulation better. This opens the door to a new class of drugs for diseases where myelin is damaged.
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The Retsat Q247R variant found in high-altitude-adapted species enhances CNS myelination by increasing enzymatic activity and neuronal production of the signaling metabolite all-trans-13,14-dihydroretinol (ATDR).
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The pro-myelinating effect of Retsat Q247R is non-cell autonomous: the mutation acts in neurons, not oligodendrocytes, to promote OPC differentiation.
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Neurons convert ATDR to all-trans-13,14-dihydroretinoic acid (ATDRA), which acts as a paracrine signal to activate the RXR-gamma pathway in oligodendrocyte progenitor cells, driving their differentiation and myelination.
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Mice carrying the Q247R mutation show reduced neonatal hypoxia-induced hypomyelination and enhanced remyelination in adult demyelination models (LPC and cuprizone).
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Systemic administration of ATDR as a prodrug promotes remyelination in multiple myelin injury models including neonatal hypoxia, LPC-induced focal demyelination, and experimental autoimmune encephalomyelitis, with favorable safety profiles.
Evolutionary adaptations provide a powerful lens for discovering fundamental regulators. By studying a Retsat variant (Q247R) found in high-altitude-adapted species, we reveal a central pathway governing CNS myelination and repair. Mice harboring this variant show reduced neonatal hypoxia-induced hypomyelination and exhibit enhanced remyelination in adulthood. The variant exhibits heightened enzymatic activity, driving increased neuronal production of all-trans-13,14-dihydroretinol (ATDR). By ruling out an intrinsic role in oligodendrocytes, we define this pathway as non-cell autonomous. ATDR is converted in neurons to all-trans-dihydroretinoic acid, which acts as a neuron-to-glia paracrine signal to activate the RXR-gamma pathway in oligodendrocyte progenitor cells, thereby stimulating their differentiation and myelination. Administration of ATDR, a prodrug, potently promotes remyelination in multiple myelin injury models. Our work identifies Retsat and dihydroretinoids as pivotal regulators of white matter integrity and as a promising therapeutical avenue inspired by evolutionary genetics for white matter diseases.