The Carbohydrate Epitope 3-Fucosyl-N-Acetyllactosamine Is Region-Specifically Expressed in Astrocytes of the Rat Brain

Abstract

The carbohydrate epitope 3-fucosyl-N-acetyllactosamine (CD 15) is involved in cell-to-cell recognition processes in various tissues. In the CNS of the adult rat, immunoreactivity for CD 15 reveals a region-specific distribution pattern by light microscopy. In the present study we investigated the ultrastructural localization of CD 15 in the rat brain using preembedding immunocytochemical methods. In addition we studied CD 15 expression in cultured astrocytes from optic nerves of 11-day-old rats. In optic nerve sections, immunostaining was found on the surface of astrocytes at various contact sites, i.e. astrocyte-astrocyte, astrocyte-oligodendrocyte, astrocyteaxon myelin, and astrocyte-blood vessel contacts. Oligodendrocyte-oligodendrocyte contacts, however, were always negative. In the telencephalic cortex, CD 15 immunoreactivity was found in glial cell processes around synapses and in the cerebellar cortex in Bergmann glial cells. In astrocytes grown in serum-containing medium, CD 15 was expressed on the surface of fibroblast-like glial fibrillary acidic protein-positive astrocytes, which were identified as type 1 astrocytes as well as on process-bearing A2B5-positive cells, representing type 2 astrocytes. The present data support the assumption that in the adult rodent brain, CD 15 is exclusively expressed by astrocytes. The in vivo distribution of this carbohydrate molecule on distinct astroglial contact sites supports the notion that CD 15 could act in cell-to-cell recognition processes.

Restriction of high CD15 expression to a subset of rat cerebellar astroglial cells can be overcome by transduction with adenoviral vectors expressing the rat ?1,3-fucosyltransferase IV gene

“…Results obtained for P5 and P9 were essentially the same (data not shown). Results obtained for P9 and P32 are shown in Figure 2 and support those of previous studies on CD15 and HNK-1 on rat postnatal cerebellum (reviewed by Gocht, 1994;Jungalwala, 1994). At P9, it is apparent that CD15 and HNK-1 are present on different cell populations.…”

“…The CD15 staining is clustered around the developing Purkinje cells and their dendrites, resulting in a particulate, densely stained molecular layer. Gocht et al (1994) have previously demonstrated by electron microscopy studies that the CD15 in the molecular layer is localized to the glial cell surface. As the Bergmann glial fibers emerge into the external granule cell layer, where no dendrite ensheathing is occurring, the CD15 staining is visualized more clearly as straight, stained fibers.…”

“…Glycoconjugates with CD15 epitopes (also known as Le x , SSEA-1, FAL, and FORSE-1 epitopes) are temporally and spatially regulated in the central nervous system (Marani and Mai, 1992;Gocht, 1994;Gocht et al, 1996). In postnatal cerebellum, CD15 expression is restricted predominantly to Bergmann glial cells (Lagenaur et al, 1982;Gocht et al, 1994), whose cell bodies are located between those of the Purkinje cells and whose processes ascend in almost parallel lines through the molecular and external granular cell layers to the pial surface.…”

“…In postnatal cerebellum, CD15 expression is restricted predominantly to Bergmann glial cells (Lagenaur et al, 1982;Gocht et al, 1994), whose cell bodies are located between those of the Purkinje cells and whose processes ascend in almost parallel lines through the molecular and external granular cell layers to the pial surface. The surfaces of the Bergmann glial cell bodies and fibers exhibit multiple expansions that scroll around the cell body and dendrites of the Purkinje cell, almost completely isolating it, except for synapses with other nerve cells (Palay and Chan-Palay, 1974).…”

“…Bergmann glial cells have been proposed to play important roles in both the insulation and maturation of Purkinje cells, as well as in guiding granule neurons in their migration along the glial fibers from the external granule cell layer to the internal granule cell layer (Rakic, 1971;Palay and Chan-Palay, 1974). CD15 is found clustered on the Bergmann glial cell surface at sites of cell-cell interaction (Gocht et al, 1994), suggesting it may play a role in adhesion and signaling between the Bergmann glial cell and the Purkinje cell and/or the migrating granule neuron.…”