Submitted June 26, 2007
Returned for revision August 7, 2007
Accepted November 30, 2007
Gamete Biology
Ca2+ Homeostasis Regulates Xenopus Oocyte Maturation
Lu Sun ,
Rawad Hodeify ,
Shirley Haun ,
Amanda Charlesworth ,
Angus M MacNicol ,
Subramaniam Ponnappan ,
Usha Ponnappan ,
Claude Prigent ,
and
Khaled Machaca *
* To whom correspondence should be addressed. E-mail: kamachaca{at}uams.edu.
Abstract
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 argues that Ca2+ homeostasis is important in establishing the oocyte's competence to undergo maturation in preparation for fertilization and embryonic development.
Key words:
Gamete Biology •
Calcium •
Meiosis •
Oocyte development •
Aurora Kinase A
