OLIGODENDROCYTE-TYPE-2 ASTROCYTE (O-2A) PROGENITOR CELLS EXPRESS GLUTAMINE-SYNTHETASE - DEVELOPMENTAL AND CELL-TYPE-SPECIFIC REGULATION

Glutamine synthetase (GS), the enzyme that catalyses glutamine synthes is from glutamate and ammonia, plays a central role in the detoxificat ion of brain ammonia.(1) In the central nervous system (CNS), GS also subserves additional important functions such as regulating glutamate, GABA and amino acid metabolism.(2) Oligodendrocytes (OL) form the mye lin sheath in the central nervous system (CNS) and are essential for e fficient propagation of nerve impulses. In culture, OL arise from bipo tential O-2A progenitor cells. These O-2A cells give rise to type-2 as trocytes in the presence of serum. GS is expressed in mature glial cel ls(3-7) in vivo and in vitro, but it is unknown whether GS is present in glial progenitors. In addition, a comparison of the GS expression l evel among the various types of glial cells has never been done in vit ro. The current study investigates in vitro GS expression levels in O- 2A progenitors, astrocytes and OL. We demonstrate that the GS gene is expressed in O-2A progenitors and is expressed at different levels in each cultured glial cell type. GS also is stimulated during OL develop mental maturation. Thus, the GS gene is expressed in O-2A cells and is regulated in a developmental and macroglial cell type-specific manner .