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Distinct roles of Cep192 and Cep152 in acentriolar MTOCs and spindle formation during mouse oocyte maturation. Lee IW et al. (2017) Mammalian oocytes lack a centriole that acts as a microtubule organization center (MTOC) in most somatic cells. During oocyte maturation, MTOCs undergo remodeling processes, including decondensation, fragmentation, and self-organization. However, the underlying mechanisms of MTOC remodeling in mouse oocytes are not well understood. We showed that two pericentriolar proteins, Cep192 and Cep152, play crucial roles during MTOC remodeling in mouse oocytes. Cep192 is present in MTOCs at all stages of oocyte maturation, and its depletion induces ablation of MTOCs, delay in spindle formation, and abnormal chromosomal alignment in spindles. In the case of Cep152, its localization on MTOCs is limited at the germinal vesicle stage and then disappears from the MTOCs after the germinal vesicle breakdown stage. Cep152 exclusion from MTOCs is involved in the fragmentation of MTOCs, and it is regulated by cyclin-dependent kinase 1 activity. Our results demonstrate the different roles of Cep192 and Cep152 in MTOC remodeling and a novel regulatory mechanism during meiotic spindle formation in mouse oocytes.-Lee, I.-W., Jo, Y.-J., Jung, S.-M., Wang, H.-Y., Kim, N.-H., Namgoong, S. Distinct roles of Cep192 and Cep152 in acentriolar MTOCs and spindle formation during mouse oocyte maturation.//////////////////
CIP2A acts as a scaffold for CEP192-mediated MTOC assembly by recruiting Plk1 and Aurora A during meiotic maturation. Wang H et al. (2017) In contrast to somatic cells where spindle microtubules are nucleated from centrosomes acting as major microtubule organizing centers (MTOCs), oocytes form meiotic spindles by assembling multiple acentriolar MTOCs without canonical centrosomes. Although Aurora A and Plk1 are required for these events, the underlying mechanisms remain largely unknown. Here we show that cancerous inhibitor of protein phosphatase 2A (CIP2A) regulates MTOC organization by recruiting Aurora A and Plk1 at spindle poles during meiotic maturation. CIP2A colocalized with pericentrin at spindle poles with a few specific cytoplasmic foci. Although CIP2A has been identified as an endogenous inhibitor of protein phosphatase 2A (PP2A), overexpression of CIP2A had no effect on meiotic maturation. Depletion of CIP2A perturbed normal spindle organization and chromosome alignment by impairing MTOC organization. Importantly, CIP2A was reciprocally associated with CEP192, promoting the recruitment of Aurora A and Plk1 at MTOCs. Moreover, CIP2A was phosphorylated by Plk1 at S904, which targets CIP2A to MTOCs and facilitates MTOC organization with CEP192. Collectively, our results suggest that CIP2A acts as a scaffold for CEP192-mediated MTOC assembly by recruiting Plk1 and Aurora A during meiotic maturation in mouse oocytes.//////////////////
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