(1) Species-Specific Sperm Binding: The Role of Oviduct Glycans in Reproductive Compatibility

Species-Specific Sperm Binding: The Role of Oviduct Glycans in Reproductive Compatibility

Anurupa Moitra¹_,Leonardo Molina¹, Kevin Lam² , Kankanit Doungkamchan¹, Carlo Unverzagt² & David Miller¹

 ¹Department of Animal Sciences and Institute of Genomic Biology, University of Illinois at Urbana-Champaign, 1207 West Gregory Drive, Urbana, IL, 61801, USA.

²Bioorganic Chemistry, Gebäude NWI, University of Bayreuth, 95440 Bayreuth, Germany.

Abstract Text:

In mammals, sperm must pass through the lower oviduct after mating before reaching the fertilization site, the ampulla. Females retain and store sperm in the lower oviduct, forming a sperm reservoir that extends sperm lifespan and reduces the risk of polyspermy. Carbohydrates (glycans) on oviduct epithelial cells bind sperm to hold them in the reservoir. To identify the important glycan motifs that bind sperm, we used an array containing 377 mammalian glycans printed on a slide and found that porcine sperm exhibit a specific affinity for two glycan motifs: branched 6-sialylated N-linked glycans and Lewis X trisaccharides (Galβ 1-4[Fucα 1-3]GlcNAcβ). These glycan motifs were abundant in the isthmus and necessary for normal sperm-oviduct binding. Our goal in the current experiments was to further delineate specific structural characteristics of glycans that bind sperm from multiple mammalian species. A specialized array with more complex N-linked glycans was used. Our results indicate that sperm from mice, horses, pigs, and dogs bound to multi antennary glycan motifs, including those with bisecting GlcNAc (a central branch of the N-glycan) and a second motif, Gal(β1-4)GlcNAc at the termini. Furthermore, there were some glycans that bound sperm from a limited number of species. For example, murine sperm bound strongly to the glycan motif Fuc(α1-3)GlcNAc, whereas equine, porcine, and canine sperm show lower affinity to glycans with this disaccharide at their termini. Similarly, although both are negatively charged, the Neu5Ac(α2-3)Gal glycan motif bound abundant sperm from dogs and horses, while the structural isomer, Neu5Ac(α2-6)Gal, bound more exclusively to porcine sperm. In addition to their ability to bind porcine sperm, motifs containing the Lewis X trisaccharide bound abundant murine sperm but not equine or canine sperm. Finally, although glycans terminating in LacNAc (N-acetyllactosamine) did not bind to porcine sperm, they did bind to mouse, stallion, and dog sperm. Post-mating pre-zygotic reproductive isolation is poorly understood and the differences in glycan-binding preferences between species may offer clues about how species develop reproductive isolation mechanisms. These results also have implications for the ability of sperm to bind to the zona pellucida during fertilization because some of these glycans are components of both the oviduct and the zona pellucida.

 This research was supported by the USDA.