Aurora kinase-A regulates microtubule organizing center (MTOC) localization, chromosome dynamics, and histone-H3 phosphorylation in mouse oocytes

Abstract

Aurora kinases (AURKs) are conserved serine/threonine kinases, crucial in regulating cell cycle events. Mammalian oocytes express all three Aurk isoforms throughout meiosis, with AurkA being the predominant isoform. Inhibition of all AURK isoforms by pharmacological means disrupts oocyte meiosis. Therefore, AurkA short interfering RNA (siRNA) was performed to silence AurkA gene expression in mouse oocytes and to further assess the function of AurkA during meiosis by analyzing subsequent loss-of-function oocyte phenotypes. Results indicated that AurkA siRNA applied in our experiments specifically knocked down both AurkA gene and protein expression without influencing transcript levels of AurkB / AurkC and other endogenous protein expression, such as GAPDH and ERK-2. AURKA was not essential for resumption of meiosis, but it potentiated oocyte meiotic progression. Knockdown of AurkA led to a significant reduction in the number of oocytes proceeding to metaphase II (MII). AurkA siRNA resulted in abnormal spindle assembly, improper localization of microtubule organizing centers (MTOCs) and misalignment of chromosomes in metaphase I (MI) oocytes. Co-immunoprecipitations demonstrated that AURKA was physically associated with phospho-Histone H3 ser10 in meiotic oocytes. AurkA siRNA dramatically reduced Histone H3 ser10 phosphorylation, but not ser28, and resulted in a significant increase of abnormal chromosome segregation in MII oocytes. In conclusion, as a predominant isoform among Aurks in oocytes, AurkA plays critical roles in mouse oocyte meiosis by regulating spindle and chromosome dynamics. Mol. Reprod. Dev. 78:80–90, 2011. © 2010 Wiley-Liss, Inc.