In the central nervous system (CNS), oligodendrocytes are the glial cells which myelinate axons. Oligodendrocytes are the end products of oligodendrocyte lineage cells that arise through complex developmental processes under meticulous regulation. Similar to precursor cells for neurons and astrocytes, the precursor cells for oligodendrocytes initially derive from the neuroepithelial cells of the neural tube. The emergence of the oligodendrocyte precursors from the ventral ventricular zone depends on local signals which direct cells to assume the fate of the oligodendrocytes. Mature oligodendrocytes express the major myelin proteins, including myelin basic protein and proteolipid protein and eventually assemble myelin. Axonal electrical activity has been shown to modulate developing oligodendrocytes with respect to their proliferation, survival, terminal differentiation, and myelinogenesis oligodendrocyte precursor cells originate from the restricted ventricular zone of the neural tube during early development, whereas in adulthood, oligodendrocytes are widely distributed throughout the CNS.