Expression of neuromodulin (GAP-43) and its regulation by basic fibroblast growth factor during the differentiation of O-2A progenitor cells.
In a recent work we have shown that neuromodulin (Nm, also known as GAP-43), a protein kinase C substrate, previously believed to be expressed exclusively in neurons, is also present in glial cells. Here we investigated the expression of Nm and its mRNA in O-2A glial progenitor cells (common precursor for oligodendrocytes and type-2 astrocytes) during their development in secondary culture and under the influence of basic fibroblast growth factor (bFGF). The different stages of oligodendrocyte development were characterized by the expression of surface markers: A2B5, which identifies O-2A glial precursor cells, and O4 and galactocerebroside (GC), which characterize later developmental stages. The number of cells expressing Nm (about 90% at culture initiation) decreased rapidly during the first 2 days and reached a plateau at around 30-40%. The level of Nm mRNA followed a similar kinetic. Immunocytochemistry demonstrated that at 4 days in vitro about 25-30% cells were A2B5+, 30-40% Nm+, a high percentage (60-70%) O4+, and 35-40% GC+. Nearly all of the morphologically immature A2B5+ cells expressed also the Nm antigen, very few of the O4+ cells still expressed Nm and almost no cells expressed both GC and Nm. Most O4+ cells developed a typical oligodendrocyte morphology and were essentially GC+. This study also showed that in the presence of serum, the A2B5+ Nm+ and O4+ Nm+ (GC-) cells retained their bipotentiality and differentiated into GFAP+ (glial fibrillary acidic protein) Nm+ type-2 astrocytes. The bFGF was found to stimulate the proliferation of Nm+ 0-2A precursor cells and to increase the level of Nm mRNA. At 4 days under this culture condition, the predominant cell type was A2B5+ and Nm+. Only 25-35% of the cells were O4+, but 90-95% of them were Nm+. Very few GC+ cells were visible in the presence of bFGF, but 20-40% of them were Nm+. These data indicate that Nm is essentially associated to glial O-2A precursor cells and further confirm that bFGF blocks the differentiation of these cells. It is suggested that Nm plays a role in the plasticity (developmental potential) of the bipotential 0-2A progenitor cells.
Deloulme
J C
JC
Laboratoire de Neurobiologie Ontogénique, CNRS UPR 417, Centre de Neurochimie, Strasbourg, France.
Laeng
P
P
Janet
T
T
Sensenbrenner
M
M
Baudier
J
J
D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004591:Electrophoresis, Polyacrylamide Gel; D016222:Fibroblast Growth Factor 2 / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D019922:GAP-43 Protein; D005904:Glial Fibrillary Acidic Protein / Q000096:biosynthesis / Q000276:immunology; D007150:Immunohistochemistry; D007457:Iodine Radioisotopes; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000276:immunology / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000276:immunology / Q000502:physiology; D016900:Neurofilament Proteins / Q000096:biosynthesis* / Q000276:immunology / Q000502:physiology; D009457:Neuroglia / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D013234:Stem Cells / Q000378:metabolism* / Q000502:physiology; D014529:Uridine / Q000378:metabolism
D019922:GAP-43 Protein; D005904:Glial Fibrillary Acidic Protein; D007457:Iodine Radioisotopes; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D012333:RNA, Messenger; D016222:Fibroblast Growth Factor 2; D004247:DNA; D014529:Uridine