CRUCIAL ROLE FOR THE MYELIN-ASSOCIATED GLYCOPROTEIN IN THE MAINTENANCE OF AXON-MYELIN INTEGRITY

It has recently been shown that mice deficient in the gene for myelin- associated glycoprotein develop normal myelin sheaths in the periphera l nervous system. Here we report that in mutant mice older than 8 mont hs the maintenance of axon-myelin units is disturbed, resulting in bot h axon and myelin degeneration. Morphological features include those t ypically seen in human peripheral neuropathies, where demyelination-in duced Schwann cell proliferation and remyelination lead to the formati on of so-called onion bulbs. Expression of tenascin-C, a molecule indi cative of peripheral nerve degeneration, was up-regulated by axon-depr ived Schwann cells and regenerating axons were occasionally seen. Myel in-associated glycoprotein thus appears to play a crucial role in the long-term maintenance of the integrity of both myelin and axons.