During the development of the central nervous system (CNS), neuroepithelial cells in the ventricular zone are multipotent stem cells that can generate neurons and macroglia (astrocytes or oligodendrocytes).It is generally thought that these progenitor cells sequentially produce neurons followed by glia.The lineage relation between astrocytes and oligodendrocytes has long been under study, but remains controversial.In the 1980s, Martin Raff's group [1] described a glial progenitor cell, termed an O-2A cell, that can differentiate into astrocytes or oligodendrocytes in vitro, depending on the culture conditions.