Submitted February 20, 2007
Returned for revision March 17, 2007
Accepted July 27, 2007
Gamete Biology
Spatio-Temporal Expression Patterns of Aurora Kinases A, B, and C and Cytoplasmic Polyadenylation-Element-Binding Protein in Bovine Oocytes During Meiotic Maturation
Svetlana Uzbekova *,
Yannick Arlot-Bonnemains ,
Joëlle Dupont ,
Rozenn Dalbiès-Tran ,
Pascal Papillier ,
Sophie Pennetier ,
Aurore Thélie ,
Christine Perreau ,
Pascal Mermillod ,
Claude Prigent ,
and
Rustem Uzbekov
* To whom correspondence should be addressed. E-mail: uzbekova{at}tours.inra.fr.
Abstract
Maturation of bovine immature oocyte requires cytoplasmic polyadenylation and synthesis of a number of proteins involved in meiotic progression and metaphase-II arrest. Aurora serine-threonine kinases - localized in centrosomes, chromosomes and midbody - regulate chromosome segregation and cytokinesis in somatic cells. In frog and mice oocytes, Aurora A regulates polyadenylation-dependent translation of several mRNAs like MOS and CCNB1, presumably by phosphorylating CPEB, and Aurora B phosphorylates histone H3 during meiosis. We analyzed the expression of three Aurora kinases genes AURKA, AURKB, and AURKC in bovine oocytes during meiosis by RT-qPCR and immunodetection. Aurora A was the most abundant form in oocytes both at mRNA and protein levels. AURKA protein progressively accumulated in the oocyte cytoplasm during antral follicle growth and in vitro maturation. AURKB associated with metaphase chromosomes. AURKB, AURKC and Thr-phosphorylated AURKA were detected at a contractile ring/midbody during the first polar body extrusion. CPEB, localized in oocyte cytoplasm, was hyper-phosphorylated during prophase/metaphase-I transition. Most of CPEB degraded in metaphase-II oocytes and remnants remained localized in a contractile ring. Roscovitine, U0126 and metformin inhibited meiotic divisions; they all induced a decrease of CCNB1 and phospho-MAPK3/1 levels and prevented CPEB degradation. However, only metformin depleted AURKA. The Aurora kinases inhibitor VX680 at 100 nM did not inhibit meiosis but led to multi-nuclear oocytes due to the failure of the polar body extrusion. Thus, in bovine oocyte meiosis, massive destruction of CPEB accompanies metaphase-I/II transition and Aurora kinases participate in regulating the segregation of the chromosomes, metaphase-II maintenance and the first polar body formation.
Key words:
Gamete Biology •
Kinases •
Meiosis •
Oocyte development
