Microtubule‐associated protein MAP1B expression precedes the morphological differentiation of oligodendrocytes

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Abstract
The microtubule‐associated protein MAPIB is belieyed to play an important role in the outgrowth of neurites from neurons (Tucker and Matus, Dev Biol 130:423–434, 1988). We have investigated the possibility that MAPIB might participate in the formation of processes incultured oligodendrocytes by an anal‐ ysis of the expression of MAPIB during oligodendrocyte progenitor development. The appearance of the antigens recognized by the monoclonal antibodies A2B5, O4, and O1 which define distinct stages in the maiuration of progenitors, was compared with the developmental expression of MAPIB. MAPIB is first detectable in O4 + preoligodendrocytes prior to the acquisition ofgalactocerebroside and immediately before they develop the complex process‐bearing mor‐ phology characteristic of terminally differentiated myelin‐forming oligodendrocytes in the CNS. In contrast, astrocytes have negligible amounts of MAP1B. These results demonstrate that the expression of MAP1B precedes the development of the mature oligodendrocyte phenotype and suggest that interactions between microtubules and MAP1B might have a role in the formation and stabilization of myelinforming processes.