Gamete Biology

Aurora-A Is a Critical Regulator of Microtubule Assembly and Nuclear Activity in Mouse Oocytes, Fertilized Eggs, and Early Embryos

Abstract
Aurora-A is a serine/threonine protein kinase that plays a role in cell cycle regulation. The activity of this kinase has been shown to be required for regulating multiple stages of mitotic progression in somatic cells. In this study, the changes in Aurora-A expression were revealed in mouse oocytes using Western blotting. The subcellular localization of Aurora-A during oocyte meiotic maturation, fertilization and early cleavages as well as after antibody microinjection or microtubule assembly perturbance was studied with confocal microscopy. The quantity of Aurora-A protein was high in the germinal vesicle (GV) and metaphase II (MII) oocytes and remained stable during other meiotic maturation stages. Aurora-A concentrated in the GV before meiosis resumption, in the pronuclei of fertilized eggs, and in the nuclei of early embryo blastomeres. Aurora-A was localized to the spindle poles of the meiotic spindle from the metaphase I (MI) stage to metaphase II stage. During early embryo development, Aurora-A was found in association with the mitotic spindle poles. Aurora-A was not found in the spindle region when colchicine or staurosporine was used to inhibit microtubule organization, while it accumulated as several dots in the cytoplasm after taxol treatment. Aurora-A antibody microinjection decreased the rate of germinal vesicle breakdown (GVBD) and distorted MI spindle organization. Our results indicate that Aurora-A is a critical regulator of cell cycle progression and microtubule organization during mouse oocyte meiotic maturation, fertilization and early embryo cleavage.

Key words: Gamete Biology • Early development • Fertilization • Meiosis • Ovum

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