CHONDROITIN SULFATE PROTEOGLYCANS IN THE DEVELOPING CENTRAL-NERVOUS-SYSTEM .2. IMMUNOCYTOCHEMICAL LOCALIZATION OF NEUROCAN AND PHOSPHACAN

Using immunocytochemistry, we have compared the distribution of neuroc an and phosphacan in the developing central nervous system. At embryon ic day 13 (E13), phosphacan surrounds the radially oriented neuroepith elial cells of the telencephalon, whereas neurocan staining of brain p arenchyma is very weak. By E16-19, strong staining of both neurocan an d phosphacan is seen in the marginal zone and subplate of the neocorte x, and phosphacan is present in the ventricular zone and also has a di ffuse distribution in other brain areas. Phosphacan is also widely dis tributed in embryonic spinal cord, where it is strongly expressed thro ughout the gray and white matter, in the dorsal and ventral nerve root s, and in the roof plate at E13, when neurocan immunoreactivity is see n only in the mesenchyme of the future spinal canal. Neurocan first be gins to appear in the spinal cord at E16-19, in the region of ventral motor neurons. In early postnatal and adult cerebellum, neurocan immun oreactivity is seen in the prospective white matter and in the granule cell, Purkinje cell, and molecular layers, whereas phosphacan immunor eactivity is associated with Bergmann glial fibers in the molecular la yer and their cell bodies (the Golgi epithelial cells) below the Purki nje cells. These immunocytochemical results demonstrate that the expre ssion of neurocan and phosphacan follow different developmental. time courses not only in postnatal brain (as previously demonstrated by rad ioimmunoassay) but also in the embryonic central nervous system. The s pecific localization and different temporal expression patterns of the se two proteoglycans are consistent with other evidence indicating tha t they have overlapping or complementary roles in axon guidance, cell interactions, and neurite outgrowth during nervous tissue histogenesis . (C) 1996 Wiley-Liss, Inc.