Schematic representation of the oligodendroglial lineage markers highlighted in vitro (A). A2B5+ OPC differentiation through developmental time and its location in adult (B). (A) Oligodendrocyte precursor cells (OPC), also known as oligodendrocyte type-2 astrocyte progenitor cells (O-2A), are characterized by A2B5, NG2 and PDGFRα expression. In serum-free medium, A2B5+ OPCs/O-2A differentiate into GalC+ oligodendrocytes while losing A2B5, NG2 and PDGFRα as they differentiate. These oligodendrocytes can further differentiate to expressing myelin basic protein (MBP), but they never achieve a full mature myelinating oligodendrocyte phenotype. In the presence of serum, OPCs/O-2A differentiate into type-2 astrocytes characterized by A2B5 and GFAP co-expression. However, type-1 astrocyte precursors defined by the lack of A2B5 are not generated from OPC/O2A and differentiate into A2B5- GFAP+ type-1 astrocyte. They represent a different lineage. (B) A2B5+ OPCs/O-2A differentiate through developmental time into immature (O4+, GalC+) and mature (MBP+, GalC+) oligodendrocytes while losing A2B5 marker. Nevertheless, in adulthood, A2B5+ OPCs/O-2A persist in specific neurogenic areas and subcortical white matter of rodent and human brains. SVZ: subventricular zone; SGZ subgranular zone.