Rho-kinase Controls Cell Shape Changes during Cytokinesis

Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California 94143-2200, USA.
Current Biology (Impact Factor: 9.57). 03/2006; 16(4):359-70. DOI: 10.1016/j.cub.2005.12.043
Source: PubMed


Animal cell cytokinesis is characterized by a sequence of dramatic cortical rearrangements. How these are coordinated and coupled with mitosis is largely unknown. To explore the initiation of cytokinesis, we focused on the earliest cell shape change, cell elongation, which occurs during anaphase B and prior to cytokinetic furrowing.
Using RNAi and live video microscopy in Drosophila S2 cells, we implicate Rho-kinase (Rok) and myosin II in anaphase cell elongation. rok RNAi decreased equatorial myosin II recruitment, prevented cell elongation, and caused a remarkable spindle defect where the spindle poles collided with an unyielding cell cortex and the interpolar microtubules buckled outward as they continued to extend. Disruption of the actin cytoskeleton with Latrunculin A, which abolishes cortical rigidity, suppressed the spindle defect. rok RNAi also affected furrowing, which was delayed and slowed, sometimes distorted, and in severe cases blocked altogether. Codepletion of the myosin binding subunit (Mbs) of myosin phosphatase, an antagonist of myosin II activation, only partially suppressed the cell-elongation defect and the furrowing delay, but prevented cytokinesis failures induced by prolonged rok RNAi. The marked sensitivity of cell elongation to Rok depletion was highlighted by RNAi to other genes in the Rho pathway, such as pebble, racGAP50C, and diaphanous, which had profound effects on furrowing but lesser effects on elongation.
We show that cortical changes underlying cell elongation are more sensitive to depletion of Rok and myosin II, in comparison to other regulators of cytokinesis, and suggest that a distinct regulatory pathway promotes cell elongation.

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Available from: Patrick H O'Farrell, Oct 04, 2015
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    • "Direct determination of the effect of fixation on cell blebbing Vesiculation or blebbing occurs during cell spreading (Bereiterhahn et al. 1990; Erickson and Trinkaus 1976), cell migration (Charras and Paluch 2008), cytokinesis (Fishkind et al. 1991; Hickson et al. 2006), virus uptake (Mercer and Helenius 2008), apoptosis (Coleman et al. 2001), drug metabolism (Jewell et al. 1982; Van Gorp et al. 1999), and cell fixation with various fixatives (Fox et al. 1985). Thus, we sought to determine the lowest concentration of an aldehyde fixative that leads to cell blebbing by dynamically imaging the process of fixation. "
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    Histochemie 05/2013; 139(5). DOI:10.1007/s00418-012-1058-5 · 3.05 Impact Factor
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    • "The authors reported that the polar body protrusion from the cortex requires the formation of an actomyosin tube. Furthermore , in Drosophila S2 cells, the elongation of the cell during anaphase, before cytokinesis, is attributed to the relaxation of the polar cortex and the broad equatorial contraction via myosin activity (Hickson et al., 2006). Therefore, we reason that the additional myosin rings formed during the segregation of long chromatids partially constrict the cortex, promoting the "
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    ABSTRACT: Chromosome segregation must be coordinated with cell cleavage to ensure correct transmission of the genome to daughter cells. Here we identify a novel mechanism by which Drosophila melanogaster neuronal stem cells coordinate sister chromatid segregation with cleavage furrow ingression. Cells adapted to a dramatic increase in chromatid arm length by transiently elongating during anaphase/telophase. The degree of cell elongation correlated with the length of the trailing chromatid arms and was concomitant with a slight increase in spindle length and an enlargement of the zone of cortical myosin distribution. Rho guanine-nucleotide exchange factor (Pebble)-depleted cells failed to elongate during segregation of long chromatids. As a result, Pebble-depleted adult flies exhibited morphological defects likely caused by cell death during development. These studies reveal a novel pathway linking trailing chromatid arms and cortical myosin that ensures the clearance of chromatids from the cleavage plane at the appropriate time during cytokinesis, thus preserving genome integrity.
    The Journal of Cell Biology 11/2012; 199(5):745-53. DOI:10.1083/jcb.201208041 · 9.83 Impact Factor
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    • "At mitosis onset, and persisting through prophase and metaphase , cell cortical stiffness increases, resulting in the cell rounding up [Sanger et al., 1984; Cramer and Mitchison, 1997; Maddox and Burridge, 2003]. At the onset of anaphase , through cytokinesis, the rounded cell begins to elongate and separate into two cells through a series of shape changes [Hickson et al., 2006] induced by the formation of a polar and an equatorial cortex of distinct mechanical properties. However, the relative contribution of equatorial contraction or polar relaxation to cell elongation and cytokinesis remains an open question. "
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    ABSTRACT: Single cell morphogenesis results from a balance of forces involving internal pressure (also called turgor pressure in plants and fungi) and the plastic and dynamic outer shell of the cell. Dominated by the cell wall in plants and fungi, mechanical properties of the outer shell of animal cells arise from the cell cortex, which is mostly composed of the plasma membrane (and membrane proteins) and the underlying meshwork of actin filaments and myosin motors (and associated proteins). In this review, following Bray and White [1988; Science 239:883-889], we draw a parallel between the regulation of the cell cortex during cell division and cell migration in animal cells. Starting from the similarities in shape changes and underlying mechanical properties, we further propose that the analogy between cell division and cell migration might run deeper, down to the basic molecular mechanisms driving cell cortex remodeling. We focus our attention on how an heterogeneous and dynamic cortex can be generated to allow cell shape changes while preserving cell integrity. © 2012 Wiley Periodicals, Inc.
    Cytoskeleton 11/2012; 69(11). DOI:10.1002/cm.21086 · 3.12 Impact Factor
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