Glycosaminoglycans in the olfactory epithelium and nerve of chick embryos: An immunocytochemical study

Immunoreactivity specific to keratan sulfate (KS), heparan sulfate (HS), and chondroitin sulfate (CS) in the nasal region of chick embryos on embryonic day (ED) 3.5-7, was investigated with six antibodies and three glycosidases. Immunoreactivity specific to HS, KS, and CS, and their localized distribution was seen in the olfactory epithelium, olfactory nerve, and cells located along the bundles of the olfactory nerve on ED 3.5-7. The immunoreactivity to HS was seen in the cells and their neurites located in the olfactory nerve bundles and in cells in the ventral forebrain on ED 3.5-5. The cells, i.e., gonadotropin-releasing hormone (GnRH)- or somatostatin-containing cells, are reported to originate in the olfactory epithelium, migrate along the olfactory nerve, and then invade the forebrain in chick embryos. These findings taken together, indicated that a subset of cells migrating along the nerve to the forebrain contained HS. Limited immunoreactivity to KS in the olfactory epithelium and in the underlying mesenchyme, but not in the olfactory nerve, ruled out the involvement of this glycosaminoglycan (GAG) in the migration of cells along the olfactory nerve. The immunoreactivity to CS and to its derivatives suggested the presence of CS in proteoglycan form in the olfactory structures and migrating cells.