Classically, the central nervous system (CNS) was considered to contain neurons and three main types of glial cells-astrocytes, oligodendrocytes, and microglia. Now, it has been clearly established that NG2-glia are a fourth glial cell type that are identified and defined by their expression of the NG2 chondroitin sulfate proteoglycan (Cspg4). NG2-glia differentiate into oligodendrocytes, the myelin-forming cells of the CNS, under the control of multiple extacellular and intrinsic factors. Due to this, NG2-glia are often referred to in the literature as oligodendrocyte progenitor cells...