MAPK-Activated Protein Kinase 2 Is Required for Mouse Meiotic Spindle Assembly and Kinetochore-Microtubule Attachment Ju Yuan1., Bao-Zeng Xu1., Shu-Tao Qi1, Jing-Shan Tong1, Liang Wei1, Mo Li1, Ying-Chun Ouyang 1 , Yi Hou 1 , Heide Schatten2, Qing-Yuan Sun 1 * 1 State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China, 2 Department of Veterinary Pathobiology, University of Missouri-Columbia, Columbia, Missouri, United States of America Abstract MAPK-activated protein kinase 2 (MK2), a direct substrate of p38 MAPK, plays key roles in multiple physiological functions in mitosis. Here, we show for the first time the unique distribution pattern of MK2 in meiosis. Phospho-MK2 was localized on bipolar spindle minus ends and along the interstitial axes of homologous chromosomes extending over centromere regions and arm regions at metaphase of first meiosis (MI stage) in mouse oocytes. At metaphase of second meiosis (MII stage), p- MK2 was localized on the bipolar spindle minus ends and at the inner centromere region of sister chromatids as dots. Knockdown or inhibition of MK2 resulted in spindle defects. Spindles were surrounded by irregular nondisjunction chromosomes, which were arranged in an amphitelic or syntelic/monotelic manner, or chromosomes detached from the spindles. Kinetochore–microtubule attachments were impaired in MK2-deficient oocytes because spindle microtubules became unstable in response to cold treatment. In addition, homologous chromosome segregation and meiosis progression were inhibited in these oocytes. Our data suggest that MK2 may be essential for functional meiotic bipolar spindle formation, chromosome segregation and proper kinetochore–microtubule attachments. Citation: Yuan J, Xu B-Z, Qi S-T, Tong J-S, Wei L, et al. (2010) MAPK-Activated Protein Kinase 2 Is Required for Mouse Meiotic Spindle Assembly and Kinetochore- Microtubule Attachment. PLoS ONE 5(6): e11247. doi:10.1371/journal.pone.0011247 Editor: Mikhail V. Blagosklonny, Roswell Park Cancer Institute, United States of America Received April 13, 2010; Accepted May 28, 2010; Published June 28, 2010 This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. Funding: This work was sponsored by the National Natural Science Foundation of China (30570944), National Basic Research Program of China (2006CB504004, 2006CB944001), and Knowledge Innovation Program of the Chinese Academy of Sciences (CAS) (KSCX2-YW-R-52) to QYS. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: sunqy@ioz.ac.cn . These authors contributed equally to this work. Introduction A fundamental property of life is the ability to reproduce. Mitosis and meiosis are essential for development and utilized by organisms to pass on their genetic information. The basic factors and mechanisms governing progression through mitosis and meiosis are the same [1,2]. However, the first meiotic division (meiosis I) is unique in that homologous chromosome segregation occurs. The second meiotic division (meiosis II) resembles mitosis in that the sister chromatids segregate. Cell division is a multi-stage precisely orchestrated and orderly process regulated by many factors. First, the assembly of a functional spindle is critical for accurate chromosome segregation. The number and stability of microtubules nucleated from MTOCs change throughout the cell cycle, which is correlated with the assembly of the mitotic spindle [3,4]. Spindle assembly involves coordinated activities of multiple proteins resulting in localized microtubule nucleation, dynamics, and organization, including Plk1 [5], Aurora A [6], and Astrin [7]. Second, for accurate segregation at the onset of anaphase, chromosomes need to attach, through their kinetochores, to microtubules and align at the metaphase plate [8]. The spindle assembly checkpoint (SAC) is the surveillance mechanism to ensure that anaphase onset is delayed until all chromosomes are correctly bound to microtubules [9,10]. Third, the cohesin protein complex is essential for cohesion in both mitosis and meiosis, and cleavage of one of the subunits is sufficient for chromosome segregation at anaphase [11]. In meiosis, it is generally assumed that the normal mitotic cohesin cohort of RAD21/SCC1, SMC1a, SMC3, STAG1/SA1 and STAG2/SA2 are complemented by the meiosis-specific components REC8, SMC1b and STAG3 [12]. Meiotic sister chromatids lose cohesin from their arms until the anaphase I onset, and this is mediated solely by REC8 degradation through separase activity rather than dissociation [13,14]. The anaphase-promoting complex/cyclosome (APC/C)[15], phosphorylation of REC8 by Polo-like kinase 1 [16] and mediated by Aurora kinase B [17,18] are required for the cleavage-independent dissociation of cohesion from chromosomes. In mouse oocytes, SGO2 appears to be the key protector of centromeric REC8 [19,20]. Mitogen-activated protein kinase (MAPK) signal transduction pathways are among the most widespread mechanisms of eukaryotic cell regulation that play a crucial role in many vital biological processes such as cell proliferation, cell differentiation, and cell cycle regulation. Studies in the last decade revealed that MAPK cascade also plays pivotal roles in regulating the meiotic cell cycle progression of oocytes [21,22], specifically microtubule organization and spindle assembly during mammalian oocyte meiosis [23,24,25]. A subfamily PLoS ONE | www.plosone.org 1 June 2010 | Volume 5 | Issue 6 | e11247