Electrical events during gamete maturation and fertilization in animals and humans

Abstract

Gamete cells are electrogenic, i.e. capable of responding to electrical stimuli and modifying their electrical properties during the crucial periods of maturation and fertilization. Ion channels have been widely demonstrated on the plasma membrane of the oocyte and spermatozoon in all animals studied, and electrical modifications in gametes are due to ion currents that are modulated via these ion channels. The modification of intracellular calcium levels in gametes has been extensively studied, and these modifications are recognized to be a second messenger system for gamete maturation and fertilization. Other ions also move through the plasma membrane, either in association with or independent of calcium, and these generate typical features such as fertilization currents and oscillation of resting potential. These modifications were first studied in marine invertebrates, and the observations subsequently compared with mammalian systems, including human. The precise role played by these currents in the processes of maturation and fertilization is still poorly understood; however, recent research opens new frontiers for their clinical and technological application.

Involvement of l(–)-rhamnose in sea urchin gastrulation: a live embryo assay

“…During the process of fertilization, the sperm's contact with the outer layer of the oocyte causes the acrosome reaction, in which the sperm releases enzymes that allow the sperm to get through the ovum's outermost layers: the jelly coat and the vitelline layer (Osman et al, 1989, Tosti andBoni, 2004).This reaction allows for the plasma membrane of the sperm to fuse and become continuous with the plasma membrane of the ovum (Osman et al, 1989). This contact triggers a series of cellular events.…”

“…First is the cortical reaction, where the cortical granules (located just beneath the egg plasma membrane surface) release enzymes that alter sperm receptors present on the surface of the vitelline layer (Gardner et al, 2007), a process vital in preventing polyspermy (Gardner et al, 2007). Another mechanism to prevent polyspermy occurs one second post-sperm/egg contact; an influx of sodium ions causes the membrane of the ovum to depolarize (Tosti and Boni, 2004).…”

“…The vitelline layer is disconnected from the plasma membrane and the newly visible membrane is important in blocking polyspermy as well (Tosti and Boni, 2004). The hyaline layer is derived from the vitelline layer and is important in keeping the embryo together during cell cleavage throughout the early phases of development (Tosti and Boni, 2004).…”

“…The hyaline layer is derived from the vitelline layer and is important in keeping the embryo together during cell cleavage throughout the early phases of development (Tosti and Boni, 2004).…”

Maturation of pig oocytes in vitro in a medium with pyruvate

“…Gamete metabolism is modified during the process of maturation, fertilization and development (13). Developing murine embryos prefer pyruvate as their main energy source until they reach the blastocyst stage (14).…”