ROLE OF AXONAL COMPONENTS DURING MYELINATION

Myelination is a multistep ordered process whereby Schwann cells in th e peripheral nervous system (PNS) and oligodendrocytes in the central nervous system (CNS), produce and extend membranous processes that env elop axons. Mechanisms that regulate this complex process are not well understood. Advances in deciphering the regulatory components of myel ination have been carried out primarily in the PNS and although the me chanisms for triggering and directing myelination are not known, it is well established that myelination does not occur in the absence of ax ons or axon/neuron-derived factors. This appears to be true both in PN S and CNS. Progress in understanding CNS myelinogenesis has been relat ively slow because of the unavailability of a suitable culture system, which, in turn, is partly due to complexity in the cellular organizat ion of the CNS. Though the myelin composition differs between PNS and CNS, the regulation of myelination seems to parallel rather than diffe r between these two systems. This article reviews the regulatory role of axonal components during myelination. The first half consists of an overview of in vitro and in vivo studies carried out in the nervous s ystem. The second half discusses the use of a cerebellar slice culture system and generation of anti-axolemma monoclonal antibodies to inves tigate the role of axonal membrane components that participate in myel ination. It, also describes the characterization of an axonal protein involved in myelination. Microsc. Res. Tech. 41:379-392, 1998. (C) 199 8 Wiley-Liss, Inc.