Localization of chondroitin sulfate proteoglycan versican in adult brain with special reference to large projection neurons

Abstract

Versican is a chondroitin sulfate proteoglycan belonging to the lectican family. Versican has two glycosaminoglycan attachment regions, named the GAG alpha and GAG beta domains, which are both regulated by alternative splicing and yield four protein isoforms. We have investigated the expression and localization of versican in the developing and adult brain by using anti-versican GAG alpha and GAG beta antibodies. Western analysis revealed that GAG alpha-reactive isoform was dominant in the adult brain. Immunohistochemical study demonstrated that GAG alpha immunoreactivity was detectable from neonatal periods to adulthood, whereas GAG beta immunoreactivity completely disappeared within 3 weeks of birth. In the adult brain, GAG alpha immunoreactivity was seen in the white matter regions and was also localized in the gray matter including somata and dendrites of cortical and hippocampal pyramidal neurons and cerebellar Purkinje cells. In contrast, GAG alpha immunoreactivity was not localized on parvalbumin-positive interneurons and cerebellar stellate cells. Furthermore, GAG alpha immunoreactivity was not co-localized with perineuronal net markers such as Wisteria floribunda agglutinin lectin and phosphacan. Thus, versican was localized on large projection neurons rather than small interneurons. To confirm the binding mechanism of versican to neurons, hyaluronan and chondroitin sulfates were enzymatically removed from brain sections before the immunolabeling of versican. These treatments had no effect on the labeling pattern of versican, suggesting that other versican-interactive molecules are involved in the binding of versican to neurons.