Calcium oscillations, oocyte activation, and phospholipase C zeta

In mammals, gamete fusion initiates a succession of oscillations in the intracellular concentration of calcium within the oocyte, prompting a series of events to occur that are collectively known as "oocyte activation". Such events are a fundamental necessity for the initiation of cell division and subsequent embryogenesis. Compelling evidence now indicates that these calcium oscillations are caused by a testis-specific phospholipase C (PLC) termed PLCzeta (PLCζ), released into the oocyte following gamete fusion. A series of recent studies indicate that abnormal expression or aberrant activity of PLCζ is linked to certain types of human male infertility, where oocyte activation ability is impaired or absent altogether. In this chapter, we discuss the critical role of calcium oscillations in the process of oocyte activation, review the role of PLCs in this fundamental biological reaction, describe how PLCζ has been formally linked to male infertility, and postulate the potential roles for PLCζ in terms of clinical diagnosis and therapy.