Aldolase C/zebrin II expression in the neonatal rat forebrain reveals cellular heterogeneity within the subventricular zone and early astrocyte differentiation

During late gestational and early postnatal development, proliferating cell s in the subventricular zones of the lateral ventricles (SVZ) migrate into the gray and white matter of the forebrain and differentiate into astrocyte s and oligodendrocytes. Because the cellular composition and structure of t he neonatal SVZ is poorly understood, we performed a differential display P CR screen to identify genes preferentially expressed therein. One highly ex pressed gene encoded aldolase C. We used a specific monoclonal antibody, al dolase C/zebrin II (ALDC/ZII), in combination with markers of glial lineage and proliferation, to characterize the cells that express this gene. In th e neonatal SVZ, ALDC/ZII-positive cells, which are generally polygonal and display several processes, have a nonuniform spatial distribution. They do not express vimentin, GFAP, or NG2. A subset of ALDC/ZII-positive cells inc orporates bromodeoxyuridine, but progenitors identified by beta -galactosid ase expression after infection with recombinant BAG virus do not show ALDC/ ZII immunoreactivity. Outside of the SVZ, beta -galactosidase-positive/ALDC /ZII-positive cells have an astrocytic phenotype, suggesting that immunorea ctivity was acquired after exit from the SVZ. These studies demonstrate tha t the neonatal SVZ is composed of different populations of cells that can b e characterized by their antigenic phenotype, their proliferative capacity, and their spatial distributions. Nonrandom distributions of different cell types within the SVZ may permit the formation of microenvironments that st imulate the production of cells with specific potentials at appropriate poi nts in development. Analysis of ALDC/ZII expression by astrocyte lineage ce lls in the neonatal cerebral cortex and white matter may reveal insights in to the phenotype and behavior of undifferentiated astrocyte progenitors.