CONICET | Buscador de Institutos y Recursos Humanos

Fertilization is a calcium-dependent process that involves sequential cell-cell adhesion events of spermatozoa with oviduct epithelial cells (OEC) and with Cumulus Oocyte Complexes (COC). Epithelial cadherin (E-cadherin) participates in calcium-dependent somatic cell adhesion; the adaptor protein B-catenin binds to the Ecadherin cytoplasmic domain and links the adhesion protein to the cytoskeleton. The study was conducted to immunodetect E-cadherin and B-catenin in bovine gametes and oviduct (tissue sections and OEC monolayers) and to assess E-cadherin participation in fertilization related events. E-cadherin was found in spermatozoa, oocytes, cumulus cells and OEC. In acrosome-intact non-capacitated spermatozoa, E-cadherin was mainly localized in the apical ridge and acrosomal cap (E1-pattern; 84 +/- 9%; mean +/-SDM; SDM: standard deviation of the mean). After sperm treatment with heparin to promote capacitation, the percentage of cells with E1-pattern (56 +/- 12%) significantly decreased; concomitantly, the percentage of spermatozoa depicting a E-cadherin staining pattern similar to E1-pattern but showing a signal loss in the acrosomal cap (E2-pattern: 40 +/- 11%) increased. After LPC induced-acrosome reaction, E-cadherin signal was mainly localized in the inner acrosomal membrane (E3-pattern; 67 +/- 22%). In in vitro matured COC, E-cadherin was immunodetected in the plasma membrane of cumulus cells and oocytes, but was absent in the polar body. The 120 KDa mature protein form was found in protein extracts from spermatozoa, oocytes, cumulus cells and OEC. B-catenin distribution followed E-cadherin in all cells evaluated. E-cadherin participation in cell-cell interaction was evaluated using specific blocking monoclonal antibody DECMA-1. Sperm incubation with DECMA-1 impaired sperm-OEC binding (number sperm bound to OEC: DECMA-1=6.7 +/- 6.1 versus control=29.6 +/- 20.1; P