The calcium signaling pathway that initiates embryonic development in fertilize amphibian eggs.

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At fertilization, a transient increase of cytoplasmic calcium ions(Ca^<2+>) triggers various activation responses in animal eggs. In amphibian, these responses include exit from meiotic arrest and cortical remodeling observed as activation contraction. We have investigated substrates for calcineurin in inducing the meiotic exit and regulatory mechanisms for the activation contraction, using cell-free extracts and cell cortices isolated from Xenopus eggs. The results indicated that Erp1 and Cdc20, both of which are essential for cyclin B destruction which leads to the meiotic exit, are dephosphorylated upon activation. The phosphatase(s) responsible for their dephosphorylation remains to be identified. We have also established the method to isolate the cell cortex from oocytes and eggs and to elute their cortical proteins. Using these materials, we found that anillin, an actin cytoskeletal regulator protein, increases during oocytes maturation and is dephosphorylated upon activation. Thus, the cortical isolation method developed in this study has enabled the biochemical analyses of cell cortex.