Acrosome-intact mouse sperm bind to the zona pellucida through specific receptor-ligand interactions and subsequently undergo an acrosome reaction. This step appears to have been impaired with sperm of nectin-2-defi-cient mice. Sperm binding to the oolemma is also mediated by a family of gamete receptors and their ligands. In mouse, both acrosome-intact and acrosome-reacted sperm are capable of binding to the oolemma of zona-free hamster eggs. Interestingly, this binding to the oolemma was not impaired in the nectin-2-deficient mice, although subsequent sperm penetration of the oocytes was abnormal. This observation suggests that the ability of knockout sperm to undergo an acrosome reaction may be altered. asthma rescue inhalers
Are mutations in the nectin-2 gene a reason for male infertility in men presenting with abnormal spermatozoan head/midpiece morphology? Numerous genetic causes are known for male infertility, deciphered mainly from experiments in animal models. For example, targeted gene disruption of HsP70-2 in mice leads to failed meiosis, germ cell apoptosis, and male infertility, a phenotype that may relate to infertility in men. Cause and effect in this genetic trait, of course, is totally different from the nectin-2 knockout described here. As yet, no link is known between a defective nectin-2 gene and human male infertility, but a correlation between these phenotypes may be discovered in the future. If so, fertilization of eggs could possibly be achieved by intracytoplasmic sperm injection with nectin-2-null spermatozoa.