(mentions CMT) Turning back the clock for Schwann cells

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Turning back the clock for Schwann cells

http://www.eurekalert.org/pub_releases/2008-05/ru-tbt051608.php

Myelin-making Schwann cells have an ability every aging Hollywood

star would envy: they can become young again. According to a study

appearing in the May 19 issue of the Journal of Cell Biology,

B. Parkinson (University College London, London, UK) and collogues

have pinned down a protein that returns the cells to their youth, a

finding that might help researchers understand why myelin production

falters in some diseases.

Wrapped around neurons in the peripheral nervous system, Schwann

cells can " dedifferentiate " into a state in which they can't

manufacture myelin. Reverting to an immature type of cell speeds

healing of injured nerves. Researchers knew that the protein Krox-20

pushes immature Schwann cells to specialize and form myelin, but they

didn't know what prompts the reversal. One suspect was a protein

called c-Jun, which youthful Schwann cells make but Krox-20 blocks.

Parkinson et al. cultured neurons with Schwann cells whose c-Jun gene

they could activate. Turning on the gene curbed myelination,

suggesting that c-Jun prevents young Schwann cells from growing up. c-

Jun also prodded mature Schwann cells to become youthful again, the

researchers discovered. Schwann cells that are separated from neurons

normally dedifferentiate, but the team found that the cells remained

specialized if c-Jun was missing. They suspect that c-Jun works in

part by activating Sox-2, as this protein also inhibits myelination.

The researchers now want to investigate whether c-Jun is involved in

illnesses where myelin dwindles, such as Charcot-Marie Tooth disease

and Guillain-Barre syndrome. The results might also provide clues

about multiple sclerosis, in which immune attacks destroy myelin in

the central nervous system. Unlike Schwann cells, oligodendrocytes,

the myelin makers in the central nervous system, can't revert to an

immature state. Whether c-Jun affects oligodendrocyte differentiation

isn't known.