Expression of sulfoglucuronyl (HNK-1) carbohydrate and its binding protein(SBP-1) in developing rat cerebellum

Sulfoglucuronyl carbohydrate (SGC) is expressed on several glycoproteins of the immunoglobulin superfamily of cell-adhesion molecules. Developmental e xpression of SGC and its binding protein, SBP-1, was studied in the rat cer ebellum by immunocytochemistry to understand the function of SEP-1 and the significance of its interaction with SGC. During early postnatal developmen t (postnatal day (PD) 3-10) SEP-1 was strongly expressed in the granule neu rons of the external and internal granule cell layers (EGCL and IGCL). This expression declined by PD 15, and disappeared in the adult. Between PD 3 a nd 15, SGC was expressed in cellular processes surrounding the granule neur ons in the IGCL, and it also declined and disappeared with development. SGC expression, however, continued in Purkinje cells and their dendrites in th e molecular layer in adults. The expressions of SBP-1 and SGC were developm entally regulated and appeared to be chronologically co-ordinated with gran ule neuron migration from EGCL to IGCL. High magnification confocal microsc opy showed that SBP-1 was primarily localized in nuclei and plasma membrane s of granule neurons, whereas SGC in the IGCL was localized on neuronal pla sma membranes, dendrites and glial processes, but not in cell soma. The rel ative localization of SEP and SGC was confirmed by cellular and subcellular markers in vivo and with dissociated cerebellar cells in culture. It is pr oposed that SBP-1 on plasma membranes of granule neurons interacts with SGC on the surrounding processes and membranes and this interaction could prov ide a potential mechanism for guidance and cell signaling, in the processes of granule neuron migration and differentiation. (C) 2000 Elsevier Science B.V. All rights reserved.