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Biol Reprod April 1, 2008; 78 (4): 726-35.

Ca2+ homeostasis regulates Xenopus oocyte maturation.

Sun L , Hodeify R , Haun S , Charlesworth A , MacNicol AM , Ponnappan S , Ponnappan U , Prigent C , Machaca K .

In contrast to the well-defined role of Ca2+ signals during mitosis, the contribution of Ca2+ signaling to meiosis progression is controversial, despite several decades of investigating the role of Ca2+ and its effectors in vertebrate oocyte maturation. We have previously shown that during Xenopus oocyte maturation, Ca2+ signals are dispensable for entry into meiosis and for germinal vesicle breakdown. However, normal Ca2+ homeostasis is essential for completion of meiosis I and extrusion of the first polar body. In this study, we test the contribution of several downstream effectors in mediating the Ca2+ effects during oocyte maturation. We show that calmodulin and calcium-calmodulin-dependent protein kinase II (CAMK2) are not critical downstream Ca2+ effectors during meiotic maturation. In contrast, accumulation of Aurora kinase A (AURKA) protein is disrupted in cells deprived of Ca2+ signals. Since AURKA is required for bipolar spindle formation, failure to accumulate AURKA may contribute to the defective spindle phenotype following Ca2+ deprivation. These findings argue that Ca2+ homeostasis is important in establishing the oocyte''s competence to undergo maturation in preparation for fertilization and embryonic development.

PubMed ID: 18094360
PMC ID: PMC2587222
Article link: Biol Reprod
Grant support: [+]
Genes referenced: aurka camk2a

References [+] :
Aizawa, Activation of the proteasome during Xenopus egg activation implies a link between proteasome activation and intracellular calcium release. 1996, Pubmed, Xenbase

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