Fig. 1.

Fertilization from fusion to activation. The signaling phenomena necessary for oocyte activation and embryonic development encompasses the hydrolysis of the phosphatidylinositol 4,5-bisphosphate (PIP₂) phospholipid anchored in the plasma membrane of the oocyte triggering the subsequent release of cleaved inositol trisphosphate (IP₃) and diacylglycerol (DAG). The released IP₃ is then able to bind IP₃ receptors (IP₃Rs) embedded within the endoplasmic reticulum (ER) and stimulate the release of stored Ca²⁺ to initiate the cellular responses required for oocyte activation. Among the putative sperm-specific factor(s) (SSF) that link sperm fusion to PIP₂ hydrolysis, phospholipase C zeta (PLCζ) and/or post-acrosomal WW-domain binding protein (PAWP) have emerged as key contenders (Adapted from [13])