EVIDENCE FOR NEURONAL REGULATION OF OLIGODENDROCYTE DEVELOPMENT - CELLULAR-LOCALIZATION OF PLATELET-DERIVED GROWTH-FACTOR-ALPHA RECEPTOR AND A-CHAIN MESSENGER-RNA DURING CEREBRAL-CORTEX DEVELOPMENT IN THE RAT

Oligodendrocyte responses in vitro to platelet-derived growth factor ( PDGF) include proliferation, survival, migration, and changes in cell morphology and molecular expression, Studies of mixed glial cultures e stablished that astrocytes secrete PDGF; thus astrocytes are considere d to be key regulators of oligodendrocyte development in vitro, We pre viously demonstrated PDGF alpha receptor mRNA expression by oligodendr ocyte progenitors and preoligodendrocytes during postnatal development of rat cerebral cortex, In the present study, we have mapped the spat ial and temporal expression of PDGF A-chain ligand mRNA and alpha rece ptor mRNA to determine if the cell-cell interactions that form the bas is for PDGF regulation of oligodendrocyte development in vitro are als o present in vivo, By in situ hybridization (ISH) we demonstrate that at embryonic day 17 (E17) cells expressing receptor mRNA (PDGFR alpha) are initially in the subventricular zone, at a distance from cells e xpressing ligand mRNA (PDGF+) in the cortical plate, By E20 PDGFR alph a+ cells are found throughout the corpus callosum and cortical gray ma tter, PDGF+ cells are restricted to the cortical plate prenatally and only appeared in the corpus callosum postnatally, Combined immunocytoc hemistry and ISH demonstrated the PDGF+ cells colocalized with neurofi lament, but not with GFAP, These data establish that PDGF is expressed by neurons during PDGFR alpha+ oligodendrocyte progenitor migration f rom the subventricular zone to the corpus callosum and gray matter, Fu rthermore, neurons continue to express PDGF during the generation and differentiation of appropriate numbers of oligodendrocytes needed to m yelinate axons as the nervous system matures. (C) 1996 Wiley-Liss, Inc .