A New Histochemical Approach for Studying Sperm Cell Surfaces

This study describes a novel rapid histochemical method to survey surface properties of sperm in a model system, the sea urchin. Surface properties of live and fixed sea urchin sperm of 2 species (Strongylocentrotus purpuratus and Lytechinus pictus) in seawater (live and fixed) and distilled water (fixed) were surveyed by assessing the ability of the sperm to bind to agarose beads derivatized with over 100 lectins and other proteins, carbohydrates, amino acids, nucleotides and other molecules. The results indicate that very little cell-bead binding occurs in seawater, whereas a great deal of binding occurs in distilled water, suggesting that ions inhibit cell-bead interaction. Whereas sperm of both species bound to many of the same beads, there were substantial differences in binding of sperm of each species to some beads, and there were differences in sperm-bead binding at different times of the year. The results suggest that the bead-binding assay enables the identification of species-specific and seasonally variable cell- surface properties. The large number of probes (bead types) available in the bead assay increases the likelihood of identifying new cell surface markers whose functional significance can then be the subject of further investigation. This assay offers an entirely new approach to examine surfaces of mammalian sperm in studies that could lead to identification of receptors involved in sperm-egg interaction, that may be candidates for the development of new contraceptive strategies.