Presence of Epithelial and Neural cadherin in human gametes and their involvement in adhesion events during fertilization

VEIGA F; MARÍN BRIGGILER CI; GONZALEZ ECHEVERRÍA MF; LAPYCKYJ L; VAZQUEZ-LEVIN MH

Barcelona, España

Congreso; 9th International Congress of Andrology; 2009

International Society of Andrology

Cadherins are calcium-dependent cell-cell adhesion molecules that have an essential role in embryonic development, maintenance of tissue structure and tumorigenesis; however, their participation in fertilization remains unknown. Objectives: To characterize the presence and localization of Epithelial (E-cad) and Neural (N-cad) cadherin proteins and members of the adhesion complex (b-catenin and actin) in human gametes and to assess their involvement in sperm-oocyte interaction. Methods: Protein expression in gametes was evaluated by Western immunoblotting and immunocytochemistry; their participation in fertilization was determined by assessing the ability of specific antibodies to interfere gamete interaction in in vitro assays. Results: E-cad, N-cad, b-catenin and actin were detected in sperm protein extracts; these proteins were localized to the acrosomal region of ejaculated and capacitated spermatozoa. In cells that had undergone acrosomal exocytosis, a weak signal for E-cad was detected on the whole head and a strong N-cad labelling was found over the equatorial segment. Moreover, both adhesion proteins were immunodetected on the surface of the human oocyte, and E-cad signal was also observed in the zona pellucida (ZP). Sperm preincubation with specific anti E-cad antibodies significantly inhibited binding to homologous ZP (p<0.05); contrasting, no inhibitory effect was observed when spermatozoa were treated with anti N-cad antibodies. Presence of both anti E-cad and N-cad antibodies significantly affected penetration of human spermatozoa to ZP-free hamster eggs (p<0.05). Comments/conclusions: E-cad, N-cad and members of the cadherin adhesion complex are present in human gametes. While E-cad would participate in sperm-ZP binding, both molecules would have a role during sperm-oolemma adhesion/fusion events.