The glycobiology of gametes and fertilisation

There now exists overwhelming evidence that carbohydrate recognition plays a crucial role in gamete binding from lower species to man. Simple oligosaccharides with defined sequences have been shown to inhibit sperm-egg binding in the mouse. These studies indicate that fucose could play a role in murine sperm-egg binding. Solid data have now been collected indicating that sialic acid and fucose residues participate in human sperm-ZP binding. However, in mammals as a whole, there remains a great deal of controversy about the carbohydrate ligands and lectin-like molecules that mediate sperm-egg binding. Evidence obtained in the human system suggests the intriguing possibility that the same oligosaccharide sequences that are being recognised during immune or inflammatory cell interactions overlap with those that mediate initial gamete adhesion. These observations pose significant challenges for glycobiological investigation in the future.