title: Forces positioning the mitotic spindle: Theories, and now experiments.
abstract: The position of the spindle determines the position of the cleavage plane, and is thus crucial for cell division. Although spindle positioning has been extensively studied, the underlying forces ultimately responsible for moving the spindle remain poorly understood. A recent pioneering study by Garzon-Coral et al. uses magnetic tweezers to perform the first direct measurements of the forces involved in positioning the mitotic spindle. Combining this with molecular perturbations and geometrical effects, they use their data to argue that the forces that keep the spindle in its proper position for cell division arise from astral microtubules growing and pushing against the cell's cortex. Here, we review these ground-breaking experiments, the various biomechanical models for spindle positioning that they seek to differentiate, and discuss new questions raised by these measurements.
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA, USA.|Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA, USA.
authors.forename: Hai-Yin
authors.initials: HY
authors.lastname: Wu
authors.affiliation: Center for Computational Biology, Simons Foundation, New York, NY, USA.
authors.forename: Ehssan
authors.initials: E
authors.lastname: Nazockdast
authors.affiliation: Center for Computational Biology, Simons Foundation, New York, NY, USA.|Courant Institute of Mathematical Sciences, New York University, New York, NY, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Shelley
authors.affiliation: Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA, USA.|John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA.|Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Needleman
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D017173:Caenorhabditis elegans / Q000378:metabolism / Q000502:physiology*; D002455:Cell Division; D008954:Models, Biological; D009068:Movement; D008941:Spindle Apparatus / Q000378:metabolism / Q000502:physiology*
keywords: force measurement; magnetic tweezers; microtubule; pronuclear migration and rotation; spindle; spindle positioning