Roles of mouse sperm‐associated alpha‐ L ‐fucosidases in fertilization

Sperm‐associated α‐ L ‐fucosidases have been implicated in fertilization in many species. Previously, we documented the existence of α‐ L ‐fucosidase in mouse cauda epididymal contents, and showed that sperm‐associated α‐ L ‐fucosidase is cryptically stored within the acrosome and reappears within the sperm equatorial segment after the acrosome reaction. The enrichment of sperm membrane‐associated α‐ L ‐fucosidase within the equatorial segment of acrosome‐reacted cells implicates its roles during fertilization. Here, we document the absence of α‐ L ‐fucosidase in mouse oocytes and early embryos, and define roles of sperm associated α‐ L ‐fucosidase in fertilization using specific inhibitors and competitors. Mouse sperm were pretreated with deoxyfuconojirimycin (DFJ, an inhibitor of α‐ L ‐fucosidase) or with anti‐fucosidase antibody; alternatively, mouse oocytes were pretreated with purified human liver α‐ L ‐fucosidase. Five‐millimolar DFJ did not inhibit sperm–zona pellucida (ZP) binding, membrane binding, or fusion and penetration, but anti‐fucosidase antibody and purified human liver α‐ L ‐fucosidase significantly decreased the frequency of these events. To evaluate sperm‐associated α‐ L ‐fucosidase enzyme activity in post‐fusion events, DFJ‐pretreated sperm were microinjected into oocytes, and 2‐pronuclear (2‐PN) embryos were treated with 5 mM DFJ with no significant effects, suggesting that α‐ L ‐fucosidase enzyme activity does not play a role in post‐fusion events and/or early embryo development in mice. The recognition and binding of mouse sperm to the ZP and oolemma involves the glycoprotein structure of α‐ L ‐fucosidase, but not its catalytic action. These observations suggest that deficits in fucosidase protein and/or the presence of anti‐fucosidase antibody may be responsible for some types of infertility. Mol. Reprod. Dev. 80: 273–285, 2013. © 2013 Wiley Periodicals, Inc.