Expression of multiple chondroitin/dermatan sulfotransferases in the neurogenic regions of the embryonic and adult central nervous system implies that complex chondroitin sulfates have a role in neural stem cell maintenance

Abstract

Chondroitin/dermatan sulfotransferases (C/D-STs) underlie the synthesis of diverse sulfated structures in chondroitin/dermatan sulfate (CS/DS) chains. Recent reports have suggested that particular sulfated structures on CS/DS polymers are involved in the regulation of neural stem cell proliferation. Here, we examined the gene expression profile of C/D-STs in the neurogenic regions of embryonic and adult mouse central nervous system. Using reverse transcription-polymerase chain reaction analysis, all presently known C/D-STs were detected in the dorsal and ventral telencephalon of the embryonic day 13 (E13) mouse embryo, with the exception of chondroitin 4-O-sulfotransferase (C4ST)-3. In situ hybridization for C4ST-1, dermatan 4-O-sulfotransferase-1, chondroitin 6-O-sulfotransferase (C6ST)-1 and -2, and uronosyl 2-O-sulfotransferase revealed a cellular expression of these sulfotransferase genes in the embryonic germinal zones of the forebrain. The expression of multiple C/D-STs is maintained on cells residing in the adult neural stem cell niche. Neural stem cells cultured as neurospheres maintained the expression of these enzymes. Consistent with the gene expression pattern of C/D-STs, disaccharide analysis revealed that neurospheres and E13 mouse brain cells synthesized CS/DS chains containing monosulfated, but also significant amounts of disulfated, disaccharide units. Functionally, the inhibition of sulfation with sodium chlorate resulted in a significant, dose-dependent decrease in neurosphere number that could not be rescued by the addition of individual purified glycosaminoglycan (GAG) chains, including heparin. These findings argue against a simple charge-based mechanism of GAG chains in neural stem cell maintenance. The synergistic activities of C/D-STs might allow for the adaptive modification of CS/DS proteoglycans with diversely sulfated CS/DS chains in the extracellular microenvironment that surrounds neural stem cells.