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Microtubules play a central role in centering the nucleus or mitotic spindle in eukaryotic cells. However, despite common use of microtubules for centering, physical mechanisms can vary greatly, and depend on cell size and cell type. In the small fission yeast cells, the nucleus can be centered by pushing forces that are generated when growing microtubules hit the cell boundary. This mechanism may not be possible in larger cells, because the compressive force that microtubules can sustain are limited by buckling, so maximal force decreases with microtubule length. In a well-studied intermediate sized cell, the C. elegans fertilized egg, centrosomes are centered by cortex-attached motors that pull on microtubules. This mechanism is widely assumed to be general for larger cells. However, re-evaluation of classic experiments in a very large cell, the fertilized amphibian egg, argues against such generality. In these large eggs, movement of asters away from a part of the cell boundary that they are touching cannot be mediated by cortical pulling, because the astral microtubules are too short to reach the opposite cell boundary. Additionally, Herlant and Brachet discovered a century ago that multiple asters within a single egg center relative to the cell boundary, but also relative to each other. Here, we summarize current understanding of microtubule organization during the first cell cycle in a fertilized Xenopus egg, discuss how microtubule asters move towards the center of this very large cell, and how multiple asters shape and position themselves relative to each other.
Adames,
Microtubule interactions with the cell cortex causing nuclear movements in Saccharomyces cerevisiae.
2000, Pubmed
Adames,
Microtubule interactions with the cell cortex causing nuclear movements in Saccharomyces cerevisiae.
2000,
Pubmed
Andreassen,
Telophase disc: a new mammalian mitotic organelle that bisects telophase cells with a possible function in cytokinesis.
1991,
Pubmed
Bjerknes,
Physical theory of the orientation of astral mitotic spindles.
1986,
Pubmed
Brangwynne,
Microtubules can bear enhanced compressive loads in living cells because of lateral reinforcement.
2006,
Pubmed
Burakov,
Centrosome positioning in interphase cells.
2003,
Pubmed
Burbank,
A new method reveals microtubule minus ends throughout the meiotic spindle.
2006,
Pubmed
,
Xenbase
Cha,
XMAP230 is required for normal spindle assembly in vivo and in vitro.
1999,
Pubmed
,
Xenbase
Dogterom,
Force generation by dynamic microtubules.
2005,
Pubmed
Elinson,
Development in frogs with large eggs and the origin of amniotes.
2002,
Pubmed
,
Xenbase
Félix,
Centrosome assembly in vitro: role of gamma-tubulin recruitment in Xenopus sperm aster formation.
1994,
Pubmed
,
Xenbase
Gard,
Confocal immunofluorescence microscopy of microtubules, microtubule-associated proteins, and microtubule-organizing centers during amphibian oogenesis and early development.
1995,
Pubmed
,
Xenbase
Glotzer,
The 3Ms of central spindle assembly: microtubules, motors and MAPs.
2009,
Pubmed
Gönczy,
Cytoplasmic dynein is required for distinct aspects of MTOC positioning, including centrosome separation, in the one cell stage Caenorhabditis elegans embryo.
1999,
Pubmed
Grill,
The distribution of active force generators controls mitotic spindle position.
2003,
Pubmed
Grill,
Spindle positioning by cortical pulling forces.
2005,
Pubmed
Grill,
Polarity controls forces governing asymmetric spindle positioning in the Caenorhabditis elegans embryo.
2001,
Pubmed
Hamaguchi,
Analysis of the Role of Astral Rays in Pronuclear Migration in Sand Dollar Eggs by the Colcemid-UV Method: (sperm aster/pronuclear migration/sand dollar/colcemid-UV method).
1986,
Pubmed
Hays,
Traction force on a kinetochore at metaphase acts as a linear function of kinetochore fiber length.
1982,
Pubmed
Houliston,
Microtubules and cytoplasmic reorganization in the frog egg.
1992,
Pubmed
,
Xenbase
Houliston,
Patterns of microtubule polymerization relating to cortical rotation in Xenopus laevis eggs.
1991,
Pubmed
,
Xenbase
Howard,
Microtubule polymerases and depolymerases.
2007,
Pubmed
,
Xenbase
Hu,
Cell polarization during monopolar cytokinesis.
2008,
Pubmed
Mitchison,
Properties of the kinetochore in vitro. II. Microtubule capture and ATP-dependent translocation.
1985,
Pubmed
Montorzi,
Xenopus laevis embryo development: arrest of epidermal cell differentiation by the chelating agent 1,10-phenanthroline.
2000,
Pubmed
,
Xenbase
O'Connell,
Mammalian spindle orientation and position respond to changes in cell shape in a dynein-dependent fashion.
2000,
Pubmed
Pecreaux,
Spindle oscillations during asymmetric cell division require a threshold number of active cortical force generators.
2006,
Pubmed
RAPPAPORT,
Experiments concerning the cleavage stimulus in sand dollar eggs.
1961,
Pubmed
Reinsch,
Movement of nuclei along microtubules in Xenopus egg extracts.
1997,
Pubmed
,
Xenbase
Reinsch,
Mechanisms of nuclear positioning.
1998,
Pubmed
Selman,
Determination of the First Two Cleavage Furrows in Developing Eggs of Triturus Alpestris Compared with Other Forms: (cell cleavage=cytokinesis/furrow determination/Dettlaff units/newt eggs).
1982,
Pubmed
Stewart-Savage,
The temporal and spatial relationships between cortical contraction, sperm trail formation, and pronuclear migration in fertilizedXenopus eggs.
1982,
Pubmed
,
Xenbase
Tournebize,
Control of microtubule dynamics by the antagonistic activities of XMAP215 and XKCM1 in Xenopus egg extracts.
2000,
Pubmed
,
Xenbase
Tran,
A mechanism for nuclear positioning in fission yeast based on microtubule pushing.
2001,
Pubmed
Ubbels,
Evidence for a functional role of the cytoskeleton in determination of the dorsoventral axis in Xenopus laevis eggs.
1983,
Pubmed
,
Xenbase
Vallee,
How dynein helps the cell find its center: a servomechanical model.
2005,
Pubmed
Weaver,
Move it or lose it: axis specification in Xenopus.
2004,
Pubmed
,
Xenbase
Weber,
A microtubule-binding myosin required for nuclear anchoring and spindle assembly.
2004,
Pubmed
,
Xenbase
Wong,
Defending the zygote: search for the ancestral animal block to polyspermy.
2006,
Pubmed
Wühr,
Evidence for an upper limit to mitotic spindle length.
2008,
Pubmed
,
Xenbase
ZOTIN,
THE MECHANISM OF CLEAVAGE IN AMPHIBIAN AND STURGEON EGGS.
1964,
Pubmed
