Signalling mechanisms of mammalian oocyte activation.

Intensive study over the past 10 years has resulted in major advances in our understanding of the signalling mechanisms required for the transformation of the oocyte into an embryo capable of developing into a new individual. This review focuses on the signal transduction events that occur subsequent to the initial sperm-oocyte plasma membrane interaction, with particular emphasis on the mechanism(s) by which sperm initiate these signalling pathways. Downstream signalling/effector molecules that respond to sperm-induced calcium oscillations and appear to have important roles in oocyte activation are then discussed. Finally, the mechanisms of physiological oocyte activation are compared with events of oocyte activation that occur after ICSI.