title: Dynamic ordering of nuclei in syncytial embryos: a quantitative analysis of the role of cytoskeletal networks.
abstract: In syncytial embryos nuclei undergo cycles of division and rearrangement within a common cytoplasm. It is presently unclear to what degree and how the nuclear array maintains positional order in the face of rapid cell divisions. Here we establish a quantitative assay, based on image processing, for analysing the dynamics of the nuclear array. By tracking nuclear trajectories in Drosophila melanogaster embryos, we are able to define and evaluate local and time-dependent measures for the level of geometrical order in the array. We find that after division, order is re-established in a biphasic manner, indicating the competition of different ordering processes. Using mutants and drug injections, we show that the order of the nuclear array depends on cytoskeletal networks organised by centrosomes. While both f-actin and microtubules are required for re-establishing order after mitosis, only f-actin is required to maintain the stability of this arrangement. Furthermore, f-actin function relies on myosin-independent non-contractile filaments that suppress individual nuclear mobility, whereas microtubules promote mobility and attract adjacent nuclei. Actin caps are shown to act to prevent nuclear incorporation into adjacent microtubule baskets. Our data demonstrate that two principal ordering mechanisms thus simultaneously contribute: (1) a passive crowding mechanism in which nuclei and actin caps act as spacers and (2) an active self-organisation mechanism based on a microtubule network.
authors: Institute for Biochemistry, Medical School, University of Göttingen, 37077 Göttingen, Germany.
authors: Takuma
authors: T
authors: Kanesaki
authors: Carina M
authors: CM
authors: Edwards
authors: Ulrich S
authors: US
authors: Schwarz
authors: Jörg
authors: J
authors: Grosshans
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology; D000199:Actins / Q000037:antagonists & inhibitors / Q000378:metabolism; D000577:Amides / Q000494:pharmacology; D000818:Animals; D016590:Aphidicolin / Q000494:pharmacology; D001756:Blastoderm / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000502:physiology*; D048750:Cell Nucleus Division / Q000187:drug effects / Q000502:physiology*; D018385:Centrosome / Q000502:physiology; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D003703:Demecolcine / Q000494:pharmacology; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D015726:Giant Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000235:genetics; D008870:Microtubules / Q000187:drug effects / Q000502:physiology; D008938:Mitosis / Q000187:drug effects / Q000502:physiology; D024462:Myosin Type II / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics; D011725:Pyridines / Q000494:pharmacology; D016196:S Phase / Q000187:drug effects; D053778:Thiazolidines / Q000494:pharmacology; D059008:Time-Lapse Imaging; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000199:Actins; D000577:Amides; D019086:Bridged Bicyclo Compounds, Heterocyclic; D018797:Cell Cycle Proteins; D029721:Drosophila Proteins; C098388:Map60 protein, Drosophila; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D011725:Pyridines; C495593:Sqh protein, Drosophila; D053778:Thiazolidines; C108830:Y 27632; D016590:Aphidicolin; D054460:rho-Associated Kinases; D024462:Myosin Type II; C037067:latrunculin A; D003703:Demecolcine