Chapter 31 - Formation and Maintenance of Myelin

Abstract

This chapter focuses on the formation of myelin that is the differentiation of two cell types; the Schwann cell in the peripheral nervous system (PNS) and the oligodendrocyte in the central nervous system (CNS). Myelination is the production of the myelin membrane that wraps axons in the central and peripheral nervous sys­tems. The nervous system matures first, portions of the PNS myelinate, then the spinal cord, and at last, the brain. In all parts of the nervous system there are many small axons that are never myelinated. It is true that large neural pathways become myelinated before they are com­pletely functional. A relevant observation is that rats and other nest-building animals are quite helpless at birth, and they myelinate predominantly at postnatal stage. More recently, zebrafish have become a valued model since they allow detailed analysis of cells in vivo with a series of fluorescently-tagged transgenic fish lines that can be used for live imaging of cell migration and differentiation, or for imaging the induction of specific signaling pathways, or other regulatory events in real time. Pathologies associated with demyelinating diseases and con­ditions are also discussed in the chapter.