DISRUPTION OF THE GENE FOR THE MYELIN-ASSOCIATED GLYCOPROTEIN IMPROVES AXONAL REGROWTH ALONG MYELIN IN C57BL WLD(S) MICE/

The myelin-associated glycoprotein (MAG) has been shown to be inhibito ry for certain neurons in vitro (Mukhopadhyay et al., 1994; McKerrache r et al., 1994). To investigate whether MAG is an inhibitory component in peripheral myelin in vivo, MAG-deficient mutant mice were cross-br ed with C57BL/Wld(s) mice that have delayed lesion-induced myelin dege neration and axon regrowth. While in crushed nerves of C57BL/Wld(s) mi ce expressing MAG, only 16% of myelin sheaths were associated with reg rowing axons, this number was doubled in MAG-deficient C57BL/Wld(s) mi ce. These observations suggest that the absence of MAG may contribute to the improved axonal regrowth in the double mutants. Therefore, dege neration of MAG-containing myelin might be an important prerequisite t o optimize axonal regrowth after peripheral nerve injury.