Myelin basic protein is necessary for the regulation of myelin-associated glycoprotein expression in mouse oligodendroglia

Myelin-associated glycoprotein (MAG) has currently been proposed to be a po ssible igniter of myelination in the central nervous system. We propose her e that myelin basic protein (MBP) is prerequisite, which is more diffusely expressed than MAG in early stages of myelination. MBP-deficient mice show significant reduction of MAG-positive immature oligodendroglia at early sta ges of myelination, although significant increase of such cells is noted in the adult. MBP/Fyn-double deficient adult mice also show moderate increase of the same type of immature glia, but to a lesser degree than MBP-deficie ncy alone. The present study suggests that MBP is required for the regulati on of MAG expression in oligodendroglia, involving Fyn therein. We discuss the possibility that hitherto unknown molecule, not MAG, may be in responsi ble for the ignition of the myelination. (C) 2001 Published by Elsevier Sci ence Ireland Ltd.