New Publications Oligodendrocytes need mechanical cues to myelinate axons correctly

How brain cells called oligodendrocytes “measure” the thickness of nerve fibers (axons) so they can wrap them with the right amount of myelin, the insulating layer that helps electrical signals travel quickly and efficiently. A new study lead by Dr. Amit Agarwal and colleagues at the Institute for Anatomy and Cell Biology and Interdisciplinary Center for Neurosciences (IZN) solved this long-standing question, now published in Neuron (“Oligodendrocyte mechanotransduction channel TMEM63A enables axon caliber sensing and myelin size matching”, Dereddi et al. 2026).

For more than a century, neuroscience has lacked a clear molecular explanation for how oligodendrocytes measure axon diameter to set myelin thickness. This study identified TMEM63A  as key player, a tiny channel in the oligodendrocyte membrane that works like a mechanical sensor. When an oligodendrocyte process contacts an axon, the membrane is stretched; TMEM63A opens and lets calcium enter the cell, turning “physical stretch” into a biological signal that tells the cell how much myelin to build.

​When TMEM63A is missing or not working, oligodendrocytes lose this sizing ability and tend to wrap axons with a more uniform “one-size-fits-all” amount of myelin. That means large axons end up under-insulated while unusually small axons can become inappropriately wrapped, which the study links to slower nerve signal transmission and subtle movement and gait changes in mice.

Mechanistically, TMEM63A-dependent calcium signaling regulates the motor protein MYO5A, which transports mRNA for the myelin basic protein (MBP) toward developing myelin sheaths. When TMEM63A signaling is insufficient, MYO5A levels drop significantly, reducing targeted delivery of MBP mRNA to actively growing myelin sheaths.

​Beyond explaining a basic principle of myelination in the mammalian brain, the work also clarifies the pathophysiology behind a rare human condition, transient infantile hypomyelinating leukodystrophy-19 (HLD19; OMIM: 618688), caused by loss-of-function mutations in TMEM63A. This mechanistic insight opens the door for testing TMEM63A function in patient-derived oligodendrocytes and exploring ways to support myelin growth by targeting the downstream calcium-dependent pathway.

More broadly, the work strengthens the idea that mechanical sensing is a fundamental organizing principle in brain development and may motivate similar mechanotransduction-focused studies in other neural cell types.

This study was truly a team effort: other investigators from Heidelberg University include Annarita Patrizi, Oliver Kann, and Marc Freichel. The study was funded by the German Research Foundation (DFG), the Chica and Heinz Schaller Foundation, and an Alliance+ Program grant of the Health + Life Science Alliance Heidelberg Mannheim.