Fertilization of a mouse oocyte triggers oscillations of the concentration of free calcium ions in ooplasm ([Ca2+] i ). Calcium oscillations are generated in a process involving inositol 1,4,5-triphosphate (IP 3 ) produced by phospholipase C zeta (PLC zeta), a sperm specific isoform of phospholipase C. Calcium transients last for several hours until the time of pronuclei formation. The ability to generate and sustain long-lasting oscillations of [Ca2+] i is developed in oocytes during meiotic maturation, i.e. in a period between the completion of prophase of the first meiotic division and metaphase of the second meiotic division. This work focuses on the role of sperm-induced oscillations of [Ca2+] i in the activation of the embryo development. The mechanisms of MPF inactivation and block to polyspermy are presen- ted. Moreover, the link between calcium oscillations and ATP synthesis, translation of maternal mRNAs and postimplantation embryo development is described.
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