From the epididymis to the egg

CUASNICÚ P.S.

Shangai

Conferencia; 6th International Conference on the Epididymis (Epididymis VI); 2014

Fertilization is a key process to the development of a new individual. However, the molecular mechanisms underlying sperm-egg interaction still remain to be elucidated. Our laboratory has been dedicated to underpin the molecular mechanisms involved in mammalian sperm-egg interaction using CRISP proteins as model molecules. Epididymal protein CRISP1 (Cystein-Rich Secretory Protein 1), the first described member of the evolutionarily conserved CRISP family, associates with the sperm surface during maturation giving origin to two populations of the protein on sperm: one loosely bound that is released during capacitation, and one strongly bound that remains on capacitated sperm. Whereas the weakly bound population has been proposed to act as a decapacitating factor, substantial evidence obtained using in vitro assays and knockout models shows that CRISP1 present in capacitated sperm participates in both sperm-zona pellucida interaction and gamete fusion through its binding to complementary sites in the egg. This conclusion can be extended to human as judged by our findings showing that the human homologue of CRISP1 is also involved in both stages of fertilization. Interestingly, recent observations show that CRISP1 is also expressed by the cumulus cells that surround the egg being involved in the stage of cumulus penetration by sperm. Moreover, our findings revealed the ability of CRISP1 to regulate sperm calcium channels and to modulate the motility of capacitated sperm, providing novel information on the molecular mechanisms underlying CRISP1 functions. Together, these observations support the idea that CRISP1 escorts both the male and female gametes and it is a multifunctional protein playing key roles during the fertilization process. We believe these results not only contribute to a better mechanistic understanding of mammalian fertilization but also to future research on infertility and contraception.