title: Shape-motion relationships of centering microtubule asters.
abstract: Although mechanisms that contribute to microtubule (MT) aster positioning have been extensively studied, still little is known on how asters move inside cells to faithfully target a cellular location. Here, we study sperm aster centration in sea urchin eggs, as a stereotypical large-scale aster movement with extreme constraints on centering speed and precision. By tracking three-dimensional aster centration dynamics in eggs with manipulated shapes, we show that aster geometry resulting from MT growth and interaction with cell boundaries dictates aster instantaneous directionality, yielding cell shape-dependent centering trajectories. Aster laser surgery and modeling suggest that dynein-dependent MT cytoplasmic pulling forces that scale to MT length function to convert aster geometry into directionality. In contrast, aster speed remains largely independent of aster size, shape, or absolute dynein activity, which suggests it may be predominantly determined by aster growth rate rather than MT force amplitude. These studies begin to define the geometrical principles that control aster movements.
authors.affiliation: Institut Jacques Monod, 75205 Paris, France.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Tanimoto
authors.affiliation: Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Mishima 411-8540, Japan National Institute of Genetics, Mishima 411-8540, Japan Institut Curie, Centre National de la Recherche Scientifique UMR 144, 75248 Paris, France akkimura@nig.ac.jp nicolas.minc@ijm.fr.
authors.forename: Akatsuki
authors.initials: A
authors.lastname: Kimura
authors.affiliation: Institut Jacques Monod, 75205 Paris, France akkimura@nig.ac.jp nicolas.minc@ijm.fr.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Minc
mesh_terms: D000818:Animals; D002465:Cell Movement; D048430:Cell Shape; D004398:Dyneins / Q000378:metabolism; D005260:Female; D021621:Imaging, Three-Dimensional; D053685:Laser Therapy; D008297:Male; D040542:Mechanotransduction, Cellular; D018613:Microscopy, Confocal; D018715:Microscopy, Video; D008870:Microtubules / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D012617:Sea Urchins; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000378:metabolism / Q000502:physiology*; D013314:Stress, Mechanical; D013997:Time Factors; D059008:Time-Lapse Imaging
chemical_list: D004398:Dyneins