Egg activation is a crucial step that initiates embryo development upon breaking the meiotic arrest. In mammalian, egg activation is accomplished by fusion with sperm, which induces the repeated intracellular - increases ( oscillation). Researches in mammals support the view of the oscillation and egg activation is triggered by a protein factor from sperm that causes release from endoplasmic reticulum, intracellular store, by persistently activation of phosphoinositide pathway. It represents that the sperm factor generates production of inositol trisphosphate (). Recently a sperm specific form of phospholipase C zeta, referred to as PLCZ was identified. In this paper, we confer the evidence that PLCZ represent the sperm factor that induces oscillation and egg activation and discuss the correlation of PLCZ and infertility.

Change in intracellular -concentration () is an essential event for egg activation and further development. ion is originated from intracellular -store via inositol 1,4,5-triphosphate receptor and/or influx via channel. This study was performed to investigate whether changes in /calmodulin dependent protein kinase II (CaM KII) activity affect influx during artificial egg activation with ethanol using monitoring system and whole-cell patch clamp technique. Under ion-omitted condition, -oscillation was stopped within 30 min post microinjection of porcine sperm factor, and ethanol-induced increase was reduced. To investigate the role of CaM KII known as an integrator of - oscillation during mammalian egg fertilization, CaM KII activity was tested with a specific inhibitor KN-93. In the eggs treated with KN-93, ethanol failed to induce egg activation. In addition, KN-93 inhibited inward current () in a time-dependent manner in whole-cell configuration. Immunostaining data showed that the voltage-dependent channels were distributed along the plasma membrane of mouse egg and 2-cell embryo. From these results, we suggest that influx during fertilization might be controlled by CaM KII activity.