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    Bipolarization and poleward flux correlate during xenopus extract spindle assembly

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    Article (874.7Kb)
    CSF monopole labeled with X-rhodamine tubulin at speckle levels, before computational alignment (4.541Mb)
    As M1_1 after computational alignment of sequential frames (4.034Mb)
    Second example of an aligned CSF monopoles (2.245Mb)
    CSF monopole labeled with X-rhodamine tubulin at speckle levels undergoing spontaneous bipolarization (4.099Mb)
    Second example of a CSF monopole labeled with X-rhodamine tubulin at speckle levels undergoing spontaneous bipolarization (6.156Mb)
    Control spindle labeled with Alexa488-IgG to TPX2 (C terminal peptide) (upper panel) and X-rhodamine tubulin at speckle levels (lower panel) (7.104Mb)
    Spindle treated with 2mM AMPPNP using the same labels as M3_1 (8.472Mb)
    Spindle treated with 0.9 mg/ml p50 dynamitin using the same labels as M3_1 (8.416Mb)
    Example of bipolarization by new pole assembly near chromatin (5.390Mb)
    Example of bipolarization by pole splitting (9.218Mb)
    Example of bipolarization by both new pole assembly near chromatin and pole splitting (6.668Mb)
    Spindle treated with importin-alpha (1mg/ml) (5.116Mb)
    Second example of a spindle treated with importin-alpha (1mg/ml) (2.910Mb)
    Control spindle using probes as M5_1 (4.174Mb)
    Date
    2004-09-22
    Author
    Mitchison, Timothy J.  Concept link
    Maddox, P.  Concept link
    Groen, Aaron C.  Concept link
    Cameron, Lisa  Concept link
    Perlman, Z.  Concept link
    Ohi, Ryoma  Concept link
    Desai, Ankur R.  Concept link
    Salmon, Edward D.  Concept link
    Kapoor, Tarun M.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/1844
    As published
    https://doi.org/10.1091/mbc.E04-05-0440
    DOI
    10.1091/mbc.E04-05-0440
    Abstract
    We investigated the mechanism by which meiotic spindles become bipolar and the correlation between bipolarity and poleward flux, using Xenopus egg extracts. By speckle microscopy and computational alignment, we find that monopolar sperm asters do not show evidence for flux, partially contradicting previous work. We account for the discrepancy by describing spontaneous bipolarization of sperm asters that was missed previously. During spontaneous bipolarization, onset of flux correlated with onset of bipolarity, implying that antiparallel microtubule organization may be required for flux. Using a probe for TPX2 in addition to tubulin, we describe two pathways that lead to spontaneous bipolarization, new pole assembly near chromatin, and pole splitting. By inhibiting the Ran pathway with excess importin-alpha, we establish a role for chromatin-derived, antiparallel overlap bundles in generating the sliding force for flux, and we examine these bundles by electron microscopy. Our results highlight the importance of two processes, chromatin-initiated microtubule nucleation, and sliding forces generated between antiparallel microtubules, in self-organization of spindle bipolarity and poleward flux.
    Description
    Author Posting. © American Society for Cell Biology, 2004. This article is posted here by permission of American Society for Cell Biology for personal use, not for redistribution. The definitive version was published in Molecular Biology of the Cell 15 (2004): 5603-5615, doi:10.1091/mbc.E04-05-0440.
    Collections
    • Cellular Dynamics Program
    Suggested Citation
    Molecular Biology of the Cell 15 (2004): 5603-5615
     
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