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    Compression regulates mitotic spindle length by a mechanochemical switch at the poles

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    Author's draft (2.154Mb)
    Supplemental Experimental Procedures (135.6Kb)
    Movie S1. A Compressed Mitotic Spindle Expands Asynchronously (4.037Mb)
    Movie S2. A Compressed Mitotic Spindle Expands Asynchronously and Reversibly (8.775Mb)
    Movie S3. A Compressed Mitotic Spindle Is Rescaled to Twice Its Original Size by Increasing the Length of K-Fibers (7.362Mb)
    Movie S4. A Compressed Mitotic Spindle Is Rescaled to Twice Its Original Size by Increasing the Length of K-Fibers (5.621Mb)
    Movie S5. A Compressed Mitotic Spindle Is Rescaled to Twice Its Original Size by Increasing the Length of K-Fibers (3.531Mb)
    Movie S6. A Mitotic Spindle Compressed in 10 μM Taxol Widens but Does Not Lengthen (2.487Mb)
    Movie S7. Microtubule Depolymerization at the Poles Transiently Turns Off during Elongation and Resumes when the New Steady State Is Reached (9.179Mb)
    Date
    2009-05
    Author
    Dumont, Sophie  Concept link
    Mitchison, Timothy J.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/2862
    As published
    https://doi.org/10.1016/j.cub.2009.05.056
    Abstract
    Although the molecules involved in mitosis are becoming better characterized, we still lack an understanding of the emergent mechanical properties of the mitotic spindle. For example, we cannot explain how spindle length is determined. To gain insight into how forces are generated and responded to in the spindle, we developed a method to apply controlled mechanical compression to metaphase mitotic spindles in living mammalian cells, while monitoring microtubules and kinetochores by fluorescence microscopy. Compression caused reversible spindle widening and lengthening to a new steadystate. Widening was a passive mechanical response, and lengthening an active mechanochemical process requiring microtubule polymerization but not kinesin-5 activity. Spindle morphology during lengthening and drug perturbations suggested that kinetochore fibers are pushed outwards by pole-directed forces generated within the spindle. Lengthening of kinetochore fibers occurred by inhibition of microtubule depolymerization at poles, with no change in sliding velocity, interkinetochore stretching, or kinetochore dynamics. We propose that spindle length is controlled by a mechanochemical switch at the poles that regulates the depolymerization rate of kinetochore-fibers in response to compression, and discuss models for how this switch is controlled. Poleward force appears to be exerted along kinetochore fibers by some mechanism other than kinesin-5 activity, and we speculate that it may arise from polymerization pressure from growing plus-ends of interpolar microtubules whose minus-ends are anchored in the fiber. These insights provide a framework for conceptualizing mechanical integration within the spindle.
    Description
    Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Current Biology 19 (2009): 1086-1095, doi:10.1016/j.cub.2009.05.056.
    Collections
    • Cellular Dynamics Program
    Suggested Citation
    Preprint: Dumont, Sophie, Mitchison, Timothy J., "Compression regulates mitotic spindle length by a mechanochemical switch at the poles", 2009-05, https://doi.org/10.1016/j.cub.2009.05.056, https://hdl.handle.net/1912/2862
     
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