Asymmetries and Symmetries in the Mouse Oocyte and Zygote
Mammalian oocytes grow periodically after puberty thanks to the dialogue with their niche in the follicle. This communication between somatic and germ cells promotes the accumulation, inside the oocyte, of maternal RNAs, proteins and other molecules that will sustain the two gamete divisions and early embryo development up to its implantation. In order to preserve their stock of maternal products, oocytes from all species divide twice minimizing the volume of their daughter cells to their own benefit. For this, they undergo asymmetric divisions in size where one main objective is to locate the division spindle with its chromosomes off-centred. In this chapter, we will review how this main objective is reached with an emphasis on the role of actin microfilaments in this process in mouse oocytes, the most studied example in mammals. This chapter is subdivided into three parts: I—General features of asymmetric divisions in mouse oocytes, II—Mechanism of chromosome positioning by actin in mouse oocytes and III—Switch from asymmetric to symmetric division at the oocyte-to-embryo transition.
KeywordsActin Filament Meiotic Division Mouse Oocyte Asymmetric Division Meiotic Spindle
This work was supported by the Fondation pour la Recherche Médicale (Equipe FRM to MHV), the ANR (ANR-14-CE11-0002 to MHV) and the Fondation ARC (PJA20131200412 to MET). This work has received support from the Fondation Bettencourt Schueller, support under the programme “Investissements d’Avenir” launched by the French Government and implemented by the ANR, with the references: ANR-10-LABX-54 MEMO LIFE, ANR-11-IDEX-0001-02 PSL* Research University.
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