Activation of the mammalian egg at fertilization: PLCζ and Ca2+ oscillations Event

At fertilization in all mammals the sperm causes egg activation by triggering a series of intracellular Ca2+ oscillations. We have shown that these Ca2+ oscillations can be triggered by a sperm specific protein called phospholipase C zeta (PLCzeta). It is proposed that PLCzeta enters the egg after gamete fusion and causes production of Inositol 1,4,5 trisphosphate (InsP3) that leads to cycles of intracellular Ca2+ release.  PLCzeta is special amongst PLCs because it causes Ca2+ oscillations in eggs at very low concentrations. PLCzeta is certainly unusual in having a very high sensitivity to Ca2+, and in that it appears to bind to PIP2 present on intracellular vesicles rather than the plasma membrane. The role of PLCzeta may also explain some cases of male factor infertility. The use of recombinant PLCzeta may also provide a solution for some cases of failed fertilization after sperm injection (ISCI).

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