Parthenogenetic Activation of Porcine Oocytes After Nuclear Transfer

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Abstract
Mature porcine oocytes are arrested at metaphase II of meiosis. At fertilization, like all mammalian oocytes they exhibit a low frequency Ca2+ oscillation lasting several hours. This oscillation is thought to be the signal that triggers resumption of meiosis and activates the developmental program of the oocyte. The signal transduction mechanism of the sperm-induced Ca2+ signal is not known in detail, and attempts to generate the oscillation artificially have met with little success. Nevertheless, artificial activation of the oocyte is a crucial step during nuclear transfer. Methods are available to induce a transient elevation in the intracellular free Ca2+ concentration to surpass the meiotic arrest and induce development of the constructed embryo. Further studies concentrating on the mechanism of Ca2+ signaling during fertilization will help to improve the efficiency of the procedures used for parthenogenetic activation of the oocyte.