Actin cytoskeleton in cell polarity and asymmetric division during mouse oocyte maturation

Abstract

Mammalian oocyte maturation involves two successive rounds of extremely asymmetric cell divisions (known as polar body extrusion) to generate a functional haploid egg. Successful polar body extrusion relies on establishment of an asymmetric spindle position and cortical polarity. Decades of studies using mouse oocytes as a model have revealed critical roles for a dynamic actin cytoskeleton in this process. Here, we review the contribution of actin to the critical events during oocyte meiotic cell divisions with an emphasis on recent advances in understanding the underlying molecular and physical mechanisms. V C 2012 Wiley Periodicals, Inc

Non-muscle tropomyosin (Tpm3) is crucial for asymmetric cell division and maintenance of cortical integrity in mouse oocytes

“…This provides the force to maintain cytoplasmic streaming, which is suggested to directly drive asymmetric spindle migration. 3,32,46 ADF/cofilin is negatively regulated by phosphorylation at serine-3 by LIM kinase 47 and is positively regulated by dephosphorylation of this residue by the phosphatase Slingshot. 48 The activities of LIM kinases are regulated by Rho-associated kinase (ROCK), 49 which was recently reported to be involved in murine and porcine oocyte maturation.…”

“…During the first meiosis of mammalian oocytes, the meiotic spindle migrates from the center of the oocyte toward the cortex. 3 A thick F-actin cap forms in the cortex within the vicinity of the approaching meiotic spindle, and this cap marks the position of the first polar body extrusion. 4 Various actin-binding proteins play essential roles in regulating actin filament formation and thereby help to remodel cortical actin.…”

The Mos-MAPK pathway regulates Diaphanous-related formin activity to drive cleavage furrow closure during polar body emission in starfish oocytes

“…GVBD is a hallmark of the resumption of meiosis I and the first PBE is the hallmark of the completion of meiosis I. After GVBD, the spindle forms, moves and attaches to the cortex, and the cleavage furrow forms around the spindle, resulting in PBE (Kishimoto, 2003;Li and Albertini, 2013;Yi and Li, 2012). Movement of the spindle to the cortex has been well studied in mouse oocytes (Cowan, 2007;Dumont et al, 2007;Pfender et al, 2011;Verlhac and Dumont, 2008;Li and Albertini, 2013;Chaigne et al, 2013).…”

RhoA-mediated MLC2 regulates actin dynamics for cytokinesis in meiosis

“…27 During mouse oocyte meiotic maturation, actin was required for the chromosome migration, 9,28 cortical spindle anchorage, 29,30 cortex development and polarity establishment 2,31 and first polar body extrusion. 6,27 Additionally, some actin nucleation factors such as Arp2/3 complex, 6 Formin2 7,29 and Spire1/2 32 were involved in the actin organization during mouse oocyte maturation.…”

“…1 This process involves in several events which are essential for asymmetric division during oocyte maturation, including spindle organization and positioning, the establishment of cortical polarity. 2 After germinal vesicle breakdown (GVBD), a meiotic spindle assembles in the central cytoplasm and then moves to the subcortical area in an actin filament dependent process; meanwhile, a thickened F-actin cap forms which is surrounded by a myosin II ring above the metaphase I (MI) spindle. 3 Therefore, oocyte develops to a specialized cortical domain overlying the subcortical positioned meiotic spindle that is characterized by the actin enrichment, the cortical granules and microvilli free domain, which play key roles in the polar body extrusion.…”