Embryo

Zona pellucida

Gamete

Acrosome

Sperm

Zygote

Hamster

Anatomy

Biology

Endocrinology

Oocyte

Acrosin

Embryogenesis

Cell biology

Oviduct

Polyspermy

Human fertilization

Andrology

Genetics

Medicine

Proceedings of the National Academy of Sciences

Significance Mammalian oocytes are surrounded by the zona pellucida, a glycoprotein coat that protects the oocyte and embryo from mechanical damage during their preimplantation development within the oviduct. Fertilizing spermatozoa must penetrate the zona, but we do not know the exact mechanisms underlying this process. Sperm proteases were thought to work as zona lysins, but gene-knockout studies in mice did not support this assumption. In this study, we generated hamsters without acrosin, the major acrosomal protease, to examine its role in both in vivo and in vitro fertilization. Surprisingly, mutant male hamsters were completely infertile because their spermatozoa were unable to penetrate the zona. We thus demonstrated that, at least in hamsters, acrosin is essential for sperm penetration through the zona.

Acrosin is essential for sperm penetration through the zona pellucida in hamsters