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

Abstract

<jats:p>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 Ca<jats:sup>2+</jats:sup>-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 Ca<jats:sup>2+</jats:sup>-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.</jats:p>

Epididymal contribution to male infertility: An overlooked problem

“…Spermatozoa are produced in the seminiferous tubules of the testes via a complex, highly regulated differentiation process called spermatogenesis. Testicular spermatozoa are nonfunctional and lack the ability to naturally fertilise an oocyte (Jones, 1999;Tulsiani & Abou-Haila, 2012;Xu, Washington, & Hinton, 2014;Zhou, De Iuliis, Dun, & Nixon, 2018). After being released from the germinal epithelium in the process called spermiation, spermatozoa pass through tiny channels, the rete testis and the efferent ducts into the epididymis, where they undergo a complicated maturation process leading to biochemical, physiological and functional changes.…”

Siglec expression on the surface of human, bull and ram sperm

“…Siglecs 1, 2, 6 and 10 were expressed on the plasma membrane in the acrosomal cap region. The acrosomal cap is central to several sperm functions including capacitation, binding to the zona pellucida, acrosomal exocytosis, and it is also a calcium store within the sperm (Wassarman 1987, Tulsiani et al 1998, Herrick et al 2005, Berruti & Paiardi 2011, Tulsiani & Abou-Haila 2012, Buffone et al 2014. Sialylated ligands in several species are central to sperm binding to the oviductal epithelium during the formation of the sperm-oviductal reservoir as well as their subsequent release and capacitation (Hung & Suarez 2010, Talevi & Gualtiere 2010, Miller 2015, and sperm surface Siglecs may play a role in these processes.…”

CD15 and CD15s expression is associated with G1 phase of the cell cycle in glioma cell lines

“…Sialyl CD15 (CD15s) (α-Neup5Ac-(2, 3)-β-Galp- (1,4)[α-Fucp-(1,3)]-GlcpNAc-R) is a tetrasaccharide epitope that was first detected in a ganglioside fraction from human kidney [6] and in human milk [7]. CD15s has been shown to play a key role in cell-cell recognition in sperm-egg fertilisation [8] and in extravasation of leukocytes [9]. Both CD15 and CD15s are expressed in a variety of non-neoplastic cells such as granulocytes, monocytes [10], epithelial cells [11] and neurons [12,13].…”