Oligodendroglial Emergence and Deposition of Four Major Myelin Constituents in the Myelin Sheath During Development: An in Vivo Study

Abstract

In the CNS, myelin components are synthesized by the oligodendrocyte. Since the initial work of Autilio et al., (1964) which allowed purification of myelin, biochemical analysis of this membrane has been well established. The work of Leblond and coworkers (Privat and Leblond, 1972; Paterson et al., 1973) and more recently the studies conducted by the group of Raff (Raff et al., 1983–1985) have permited determination of the ontogenic origin of oligo-dendrocytes. In contrast, the first events of myelinogenesis, i.e. the time course of the synthesis of myelin constituents by the oligodendrocyte and their deposition in the nascent myelin sheath remain poorly understood. Most of the studies dealing with the developmental expression of myelin constituents have been performed on oligodendrocyte in culture (Mirsky et al., 1980; Abney et al., 1981; Bologa et al., 1981–1983; Saneto et al., 1985). Such data must be considered with caution as in vitro observations may not reflect the in vivo situation, in as much as most of these in vitro preparations do not lead to myelination, thus impairing studies on myelinogenesis.