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Volume 2012, Article ID 607427, 12 pages
Review Article

Biological Processes that Prepare Mammalian Spermatozoa to Interact with an Egg and Fertilize It

1Department of Obstetrics and Gynecology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
2UFR Biomédicale, Université Paris Descartes, 75270 Paris Cedex 06, France

Received 17 April 2012; Accepted 10 May 2012

Academic Editors: J. L. Badano, K.-J. Dietz, E.-S. Oh, H. Schatten, and C. F. Sier

Copyright © 2012 Daulat R. P. Tulsiani and Aïda Abou-Haila. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


In the mouse and other mammals studied, including man, ejaculated spermatozoa cannot immediately fertilize an egg. They require a certain period of residence in the female genital tract to become functionally competent cells. As spermatozoa traverse through the female genital tract, they undergo multiple biochemical and physiological changes collectively referred to as capacitation. Only capacitated spermatozoa interact with the extracellular egg coat, the zona pellucida. The tight irreversible binding of the opposite gametes triggers a Ca2+-dependent signal transduction cascade. The net result is the fusion of the sperm plasma membrane and the underlying outer acrosomal membrane at multiple sites that causes the release of acrosomal contents at the site of sperm-egg adhesion. The hydrolytic action of the acrosomal enzymes released, along with the hyperactivated beat pattern of the bound spermatozoon, is important factor that directs the sperm to penetrate the egg coat and fertilize the egg. The sperm capacitation and the induction of the acrosomal reaction are Ca2+-dependent signaling events that have been of wide interest to reproductive biologists for over half a century. In this paper, we intend to discuss data from this and other laboratories that highlight the biological processes which prepare spermatozoa to interact with an egg and fertilize it.