Biogenesis and significance of central nervous system myelin.

The central nervous system is composed of neurons and glia cells. Although neurons have long been considered the functionally important cells, an ever-expanding body of research has revealed many critical functions of neuroglia. Among these, the myelin sheath elaborated by oligodendrocytes acts as a dynamic partner to the axons it enwraps and can no longer be considered as an inert membrane. In addition to its best known roles of providing insulation and optimizing conduction velocity, myelination modulates the maturation, survival, and regenerative capacity of axons through trophic support and signaling molecules. Myelin is produced through a complex process involving cell differentiation, biosynthesis of specialized lipids and proteins, interaction with environmental signals, and coordinated changes in cell morphology. Understanding the pathophysiology of primary myelin disorders, and the challenges faced in treating them, is facilitated through understanding of the structure, function, and generation/regeneration of myelin. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.