CHONDROITIN SULFATE PROTEOGLYCANS IN THE DEVELOPING CENTRAL-NERVOUS-SYSTEM .1. CELLULAR SITES OF SYNTHESIS OF NEUROCAN AND PHOSPHACAN

We have used in situ hybridization histochemistry to examine the cellu lar sites of synthesis of two major nervous tissue proteoglycans, neur ocan and phosphacan, in embryonic and postnatal rat brain and spinal c ord. Both proteoglycans were detected only in nervous tissue. Neurocan mRNA was evident in neurons, including cerebellar granule cells and P urkinje cells, and in neurons of the hippocampal formation and cerebel lar nuclei. In contrast, phosphacan message was detected only in astro glia, such as the Golgi epithelial cells of the cerebellum. At embryon ic day 13-16, phosphacan mRNA is largely confined to areas of active c ell proliferation (e.g., the ventricular zone of the ganglionic eminen ce and septal area of the brain and the ependymal layer surrounding th e central canal of the spinal cord) as well as being present in the ro of plate. The distribution of neurocan message is more widespread, ext ending to the cortex, hippocampal formation, caudate putamen, and basa l telencephalic neuroepithelium, and neurocan mRNA is present in both the ependymal and mantle layers of the spinal cord but not in the roof plate. The presence of neurocan mRNA in areas where the proteoglycan is not expressed suggests that the short open reading frame in the 5'- leader of neurocan may function as a cis-acting regulatory signal for the modulation of neurocan expression in the developing central nervou s system. (C) 1996 Wiley-Liss, Inc.