title: Meiotic regulation of TPX2 protein levels governs cell cycle progression in mouse oocytes.
abstract: Formation of female gametes requires acentriolar spindle assembly during meiosis. Mitotic spindles organize from centrosomes and via local activation of the RanGTPase on chromosomes. Vertebrate oocytes present a RanGTP gradient centred on chromatin at all stages of meiotic maturation. However, this gradient is dispensable for assembly of the first meiotic spindle. To understand this meiosis I peculiarity, we studied TPX2, a Ran target, in mouse oocytes. Strikingly, TPX2 activity is controlled at the protein level through its accumulation from meiosis I to II. By RNAi depletion and live imaging, we show that TPX2 is required for spindle assembly via two distinct functions. It controls microtubule assembly and spindle pole integrity via the phosphorylation of TACC3, a regulator of MTOCs activity. We show that meiotic spindle formation in vivo depends on the regulation of at least a target of Ran, TPX2, rather than on the regulation of the RanGTP gradient itself.
authors.affiliation: UMR7622, Université Pierre et Marie Curie/CNRS, Bat. C, 5e, 9 quai Saint Bernard, Paris, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Brunet
authors.forename: Julien
authors.initials: J
authors.lastname: Dumont
authors.forename: Karen W
authors.initials: KW
authors.lastname: Lee
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Kinoshita
authors.forename: Pascale
authors.initials: P
authors.lastname: Hikal
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Gruss
authors.forename: Bernard
authors.initials: B
authors.lastname: Maro
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Verlhac
mesh_terms: D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle; D005260:Female; D005455:Fluorescent Antibody Technique; D008540:Meiosis; D051379:Mice; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering; D008941:Spindle Apparatus
chemical_list: D034741:RNA, Small Interfering