It has been known for some time that mammalian eggs are activated by a series of intracellular calcium oscillations that occur shortly after sperm egg membrane fusion. Recent work has identified a novel sperm specific phospholipase C zeta as the likely agent that stimulates the calcium oscillations in eggs after sperm-egg membrane fusion. PLCzeta is stimulated by low intracellular calcium levels in a manner which suggests that there is a regenerative feedback of calcium release and PLCzeta

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... ed inositol 1,4,5-trisphophate (InsP 3 ) production in eggs. This implies calcium oscillations in fertilizing mammalian eggs are driven by underlying oscillations of InsP 3 . This model of oscillations is supported by the response of mouse eggs to sudden increases in InsP 3 . The cellular targets of calcium oscillations include calmodulin-dependent protein kinases, protein kinase C and mitochondria. There is evidence that eggs might be best activated by multiple calcium increases rather than a single calcium rise. As yet we do not fully understand how the target of calcium in a mammalian egg might decode the patterns of calcium changes that can occur during egg activation.