Gamete adhesion molecules.

Despite the importance of fertilization for animal production, species preservation and controlling reproduction, the molecular basis underlying fertilization is not well understood. More progress has been made in mice than in other mammals, but targeted deletion of specific genes in the mouse has often yielded unexpected results. The pig is also a useful animal to study, as large numbers of pig gametes can be acquired easily. However, it appears that the pig zona pellucida proteins that bind to spermatozoa may not be homologues of ZP3, the mouse zona pellucida protein that spermatozoa bind to. Therefore, a zona pellucida receptor on spermatozoa that is important for mouse fertilization may be redundant, along with other receptors, in pig fertilization. In this review, the important steps of fertilization in pigs are discussed and the binding of pig gametes is compared with that of mouse gametes. In addition, the molecules that may be important for gamete adhesion are considered. New technical advances and creative ideas offer the opportunity to make important advances in this crucial area.