[P52]: Early fate restriction of embryonic neural stem cells

ponent are present in the ventricular and subventricular zones of the developing forebrain. The DSD-1-PG/Phosphacan is a CSPG and represents a splice variant of the receptor protein tyrosine phosphatase (RPTP)-beta gene. It is thought to be involved in the regulation of many developmental events. The DSD-1 epitope is a defined but complex cell surface-associated chondroitin sulfate-glycosaminoglycan (CS-GAG) motif recognized by the monoclonal antibody 473HD. We have isolated 473HD-positive cells by immunopanning and characterized them as actively cycling, BLBP-positive neurogenic radial glia during cortical development. When the 473HD-positive cells were cultivated under neurosphere-forming conditions an increase in the number of neurospheres compared to the non-selected cell population was observed at all stages examined. This describes a significant aspect of the biology of embryonic neural stem cells—a subset of early multipotent neural progenitor/stem cells express DSD1-PG/RPTP , which aids their identification and enrichment. To address the functional importance of CS-GAGs for development and differentiation of telencephalic neural stem/progenitor cells in vitro and in vivo we used GAG-lyases for deglycanation of CSPG and investigated the functional consequences of CSGAG removal on neural stem/progenitor cell behaviour using several cell biological assays. Our results show that removal of CS-GAGs from neural stem/progenitor cell-surface caused: (1) reduction in proliferation of these cells and their capacity to generate neurospheres in presence of EGF and bFGF and (2) changes of the composition of the precursor cell pool by a shift from neurogenic radial glia towards gliogenic radial glia after treatment. These findings revealed an important role of CS-GAGs for proliferation of neural stem/progenitor cells and suggest that this specific class of carbohydrates has a proneurogenic as well as an anti-gliogenic role during forebrain development.