[Mini-review: oocyte activation mechanisms. Different models, comparison: marine invertebrate and mammal]

In most deuterostome eggs, a transient increase in the intracellular free calcium concentration (Cai) occurs after fertilization and is essential for egg activation. How one spermatozoo triggers this calcium signal remains an enigma. In the light of our own results, we suggest a model, leading to the calcium signal and common to invertebrate and mammalian systems, where phosphorylation on tyrosine and phospholipase C gamma (PLC gamma) are interconnected pathways stimulated by a multimolecular complex involving integrins.