Immunolocalization of epithelial cadherin in mouse sperm

VEIGA F; CHOREN V; VINCENTI A; FORNÉS M; CAMEO M; MARÍN BRIGGILER CI; VAZQUEZ-LEVIN M

Buenos Aires

Congreso; VII Jornadas Multidisciplinarias de la Sociedad Argentina de Biología; 2005

Sociedad Argentina de Biología

Epithelial cadherin (E-cad) is a membrane glycoprotein involved in cell-to-cell adhesion and signaling events. Studies from our group described its expression in human sperm and suggested its involvement in sperm-egg interaction (Marin-Briggiler et al, 2004). In the murine model, sperm preincubation with anti E-cad antibodies inhibited in vitro fertilization (Veiga et al, 2005). The aim of this study was to evaluate E-cad localization in mouse sperm recovered from the testis and different regions of the epididymis, and in cells incubated under conditions that resemble changes associated with fertilization. Methods: Expression of E-cad was evaluated by immunocytochemistry in testicular and epididymal sperm, as well as in capacitated and calcium ionophore acrosome reacted-cells. Studies were carried out with an anti E-cad antibody (Santa Cruz Biotech.) that proved to inhibit mouse blastocyst development (embryonic arrest at 4-8 cell embryo stage; n=2). The sperm acrosomal status was assessed by staining with FITC-Pisum sativum agglutinin (FITC-PSA). Subcellular localization analysis of E-cad was done by immuno-electron microscopy (IEM). Results: E-cad was immunodetected in the acrosomal cap of testicular (13-57%) and epididymal sperm (caput=88-97%, corpus=81-96%, cauda=85-95%; n=3). IEM studies revealed E-cad localization in the plasma membrane of live sperm from cauda epididymis. All intact sperm (FITC-PSA acrosome positive) incubated under capacitating conditions were reactive for E-cad in the acrosomal cap; contrasting, cells that had undergone acrosomal exocytosis showed no signal in this region. In addition, a staining for E-cad was observed in the postacrosomal region in a high proportion of epididymal sperm (>60%), which remained after acrosomal exocytosis (n=4).  Conclusion: These results show E-cad presence in testicular and epididymal sperm, and suggest its unmasking/addition during maturation. E-cad localization in the acrosomal and postacrosomal regions supports its participation in gamete interaction.