Adhesion molecules in the regulation of CNS myelination.

Myelination is necessary both for rapid salutatory conduction and the long-term survival of the axon. In the CNS the myelin sheath is formed by the oligodendrocytes. Each oligodendrocyte myelinates several axons and, as the number of wraps around each axon is determined precisely by the axon diameter, this requires a close, highly regulated interaction between the axons and each of the oligodendrocyte processes. Adhesion molecules are likely to play an important role in the bi-directional signalling between axon and oligodendrocyte that underlies this interaction. Here we review the current knowledge of the function of adhesion molecules in the different phases of oligodendrocyte differentiation and myelination, and discuss how the properties of these proteins defined by other cell biological systems indicates potential roles in oligodendrocytes. We show how the function of a number of different adhesion and cell-cell interaction molecules such as polysialic acid neural cell adhesion molecule, Lingo-1, Notch, neuregulin, integrins and extracellullar matrix proteins provide negative and positive signals that coordinate the formation of the myelin membrane. Compiling this information from a number of different cell biological and genetic experiments helps us to understand the pathology of multiple sclerosis and direct new areas of research that might eventually lead to potential drug targets to increase remyelination.