Directly probing the mechanical properties of the spindle and its matrix
Video 2: Time-lapse fluorescence imaging of two spindles in the same frame escaping their needles in different directions. (31.48Mb)
Video 3: Time-lapse fluorescence imaging of a skewering needle moving through a spindle pole. (8.078Mb)
Video 4: Time-lapse fluorescence imaging of spindle escape after treatment with concentrated anti-DIC antibodies. (17.03Mb)
Video 5: Time-lapse fluorescence imaging of two-needle separation along the interpolar spindle axis (longitudinal stretching). (34.59Mb)
Video 6: Time-lapse fluorescence imaging of two-needle separation orthogonal to the interpolar spindle axis (transverse stretching). (6.233Mb)
Gatlin, Jesse C.
Mitchison, Timothy J.
Salmon, Edward D.
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Several recent models for spindle length regulation propose an elastic pole to pole spindle matrix that is sufficiently strong to bear or antagonize forces generated by microtubules and microtubule motors. We tested this hypothesis using microneedles to skewer metaphase spindles in Xenopus laevis egg extracts. Microneedle tips inserted into a spindle just outside the metaphase plate resulted in spindle movement along the interpolar axis at a velocity slightly slower than microtubule poleward flux, bringing the nearest pole toward the needle. Spindle velocity decreased near the pole, which often split apart slowly, eventually letting the spindle move completely off the needle. When two needles were inserted on either side of the metaphase plate and rapidly moved apart, there was minimal spindle deformation until they reached the poles. In contrast, needle separation in the equatorial direction rapidly increased spindle width as constant length spindle fibers pulled the poles together. These observations indicate that an isotropic spindle matrix does not make a significant mechanical contribution to metaphase spindle length determination.
© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License. The definitive version was published in Journal of Cell Biology 188 (2010): 481-489, doi:10.1083/jcb.200907110.
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