Cell surface beta 1,4 galactosyltransferase on primary spermatocytes facilitates their initial adhesion to Sertoli cells in vitro.

Abstract

The Sertoli cell maintains the cytoarchitecture of the seminiferous epithelium and provides support for the developing germ cells through specialized adhesive junctions. Despite the importance of this adhesive interaction, our understanding of germ cell-Sertoli cell interactions is limited. Previous studies have shown that beta 1,4 galactosyltransferase (GalTase) is present on the surface of mature sperm, where it mediates sperm binding to the egg zona pellucida. Since GalTase is present on the surface of early spermatogenic cells long before it is required for sperm-egg recognition, we determined in this study whether GalTase on developing germ cells functions during adhesion to Sertoli cells. Consistent with such a function, GalTase was localized by indirect immunofluorescence to areas of putative germ cell-Sertoli cell contact. More directly, anti-GalTase IgG and Fab fragments inhibited the initial adhesion of spermatocytes to Sertoli cell monolayers; however, anti-GalTase antibodies were less able to inhibit spermatocyte-Sertoli cell adhesions after prolonged co-culture, presumably due to stabilization of the intercellular adhesion. After meiosis, surface GalTase begins to acquire its final distribution overlying the intact acrosome; there it was no longer able to facilitate germ cell adhesion to Sertoli cells. Indirect immunofluorescence and direct enzyme assays showed that Sertoli cells also expressed surface GalTase; however, most GalTase was confined to the basal cell surface where it was inaccessible to germ cells, but where it may function in adhesion to the underlying basal lamina. Preblocking studies confirmed that surface GalTase on the spermatocyte surface, rather than on the exposed apical Sertoli surface, mediated germ cell-Sertoli cell adhesion, presumably by binding to glycoside ligands on the Sertoli cell.