title: Polar body emission requires a RhoA contractile ring and Cdc42-mediated membrane protrusion.
abstract: Vertebrate oocyte maturation is an extreme form of asymmetric cell division, producing a mature egg alongside a diminutive polar body. Critical to this process is the attachment of one spindle pole to the oocyte cortex prior to anaphase. We report here that asymmetric spindle pole attachment and anaphase initiation are required for localized cortical activation of Cdc42, which in turn defines the surface of the impending polar body. The Cdc42 activity zone overlaps with dynamic F-actin and is circumscribed by a RhoA-based actomyosin contractile ring. During cytokinesis, constriction of the RhoA contractile ring is accompanied by Cdc42-mediated membrane outpocketing such that one spindle pole and one set of chromosomes are pulled into the Cdc42 enclosure. Unexpectedly, the guanine nucleotide exchange factor Ect2, which is necessary for contractile ring formation, does not colocalize with active RhoA. Polar body emission thus requires a classical RhoA contractile ring and Cdc42-mediated membrane protrusion.
authors.affiliation: Ottawa Health Research Institute, Ottawa Hospital, 725 Parkdale Avenue, Ottawa, ON K1Y 4E9, Canada.
authors.forename: Xuan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Ottawa Health Research Institute, Ottawa Hospital, 725 Parkdale Avenue, Ottawa, ON K1Y 4E9, Canada.
authors.forename: Chunqi
authors.initials: C
authors.lastname: Ma
authors.affiliation: Department of Zoology, University of Wisconsin-Madison, 1117 West Johnson Street, Madison, WI 53706, USA.
authors.forename: Ann L
authors.initials: AL
authors.lastname: Miller
authors.affiliation: Ottawa Health Research Institute, Ottawa Hospital, 725 Parkdale Avenue, Ottawa, ON K1Y 4E9, Canada; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
authors.forename: Hadia Arabi
authors.initials: HA
authors.lastname: Katbi
authors.affiliation: Department of Zoology, University of Wisconsin-Madison, 1117 West Johnson Street, Madison, WI 53706, USA.
authors.forename: William M
authors.initials: WM
authors.lastname: Bement
authors.affiliation: Ottawa Health Research Institute, Ottawa Hospital, 725 Parkdale Avenue, Ottawa, ON K1Y 4E9, Canada; Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON K1N 6N5, Canada; Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, ON K1N 6N5, Canada. Electronic address: jliu@ohri.ca.
authors.forename: X Johné
authors.initials: XJ
authors.lastname: Liu
mesh_terms: D000199:Actins / Q000378:metabolism; D000705:Anaphase / Q000502:physiology; D000818:Animals; D022081:Cell Surface Extensions / Q000378:metabolism*; D019926:Cyclin B / Q000378:metabolism; D048749:Cytokinesis / Q000502:physiology*; D004789:Enzyme Activation; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D008941:Spindle Apparatus / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000502:physiology; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D019926:Cyclin B; D029867:Xenopus Proteins; D020764:cdc42 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein