Nucleation and transport organize microtubules in metaphase spindles.

Jan Brugués, Valeria Nuzzo, Eric Mazur, Daniel J Needleman

Department of Molecular and Cellular Biology and Center for Systems Biology, Harvard University, 52 Oxford Street, Cambridge, MA 02138, USA.

Cell 2012 Apr 27

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Spindles are arrays of microtubules that segregate chromosomes during cell division. It has been difficult to validate models of spindle assembly due to a lack of information on the organization of microtubules in these structures. Here we present a method, based on femtosecond laser ablation, capable of measuring the detailed architecture of spindles. We used this method to study the metaphase spindle in Xenopus laevis egg extracts and found that microtubules are shortest near poles and become progressively longer toward the center of the spindle. These data, in combination with mathematical modeling, imaging, and biochemical perturbations, are sufficient to reject previously proposed mechanisms of spindle assembly. Our results support a model of spindle assembly in which microtubule polymerization dynamics are not spatially regulated, and the proper organization of microtubules in the spindle is determined by nonuniform microtubule nucleation and the local sorting of microtubules by transport. Copyright © 2012 Elsevier Inc. All rights reserved.

Citation

Jan Brugués, Valeria Nuzzo, Eric Mazur, Daniel J Needleman. Nucleation and transport organize microtubules in metaphase spindles. Cell. 2012 Apr 27;149(3):554-64