Cytokinesis is a very hot research area. The following paper presents a very nice model addressing the different function of spindle microtubules vs. astral microtubules.
"We find that a functional cytokinetic apparatus forms and closes in the proper position in the complete absence of contact or even approach of astral microtubules with the cortex in very large, round cells. We also find that pairs of asters without an intervening spindle can specify a functional cytokinetic apparatus only when they are separated sufficiently from each other. We show that the centrosomes or asters confine the signal or its effect. Based on these and other results, we propose that distinct subsets of the mitotic apparatus collaborate to make specification of the cytokinetic apparatus both accurate and precise."
DOI: 10.1083/jcb.200907090
The Journal of Cell Biology, Vol. 187, No. 6, 831-845Action at a distance during cytokinesis
George von Dassow 1,2, Koen J.C. Verbrugghe 3, Ann L. Miller 3, Jenny R. Sider 1,5, and William M. Bement 1,3,4
1 Center for Cell Dynamics, Friday Harbor Laboratories, University of Washington, Seattle, WA 98250
2 Oregon Institute of Marine Biology, University of Oregon, Eugene, OR 97420
3 Department of Zoology and 4 Laboratory of Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
5 Amundsen High School, Chicago, IL 60625Correspondence to George von Dassow: dassow@uoregon.edu
Animal cells decide where to build the cytokinetic apparatus by sensing the position of the mitotic spindle. Reflecting a long-standing presumption that a furrow-inducing stimulus travels from spindle to cortex via microtubules, debate continues about which microtubules, and in what geometry, are essential for accurate cytokinesis. We used live imaging in urchin and frog embryos to evaluate the relationship between microtubule organization and cytokinetic furrow position. In normal cells, the cytokinetic apparatus forms in a region of lower cortical microtubule density. Remarkably, cells depleted of astral microtubules conduct accurate, complete cytokinesis. Conversely, in anucleate cells, asters alone can support furrow induction without a spindle, but only when sufficiently separated. Ablation of a single centrosome displaces furrows away from the remaining centrosome; ablation of both centrosomes causes broad, inefficient furrowing. We conclude that the asters confer accuracy and precision to a primary furrow-inducing signal that can reach the cell surface from the spindle without transport on microtubules.
"We used three tandem GFPs fused to the ensconsin microtubule-binding domain (EMTB-3G; Faire et al., 1999). This probe, unlike fluorophore-conjugated or GFP-tubulin,enabled high-contrast, high-resolution microtubule visualization throughout the cell cycle, from the eight-cell stage on in purple urchin or sand dollar embryos (Fig. 1 and Video 1) and X. laevis blastomeres (Fig. S1 D and Video 2), which revealed apparently single microtubules extending to the cortex, even in large cells."
>gi|414114:101-2350 H.sapiens E-MAP-115 mRNA
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CCGACAGCTACAAAGTGCAAGATAAGAAAAATGCCTCCAGCCGCCCTGCCTCTGCAATTTCAGGACAAAA
TAACAACCACTCAGGAAATAAACCAGACCCTCCGCCTGTGTTACGTGTTGATGACCGGCAGCGGCTGGCC
CGGGAGCGACGTGAGGAACGGGAGAAACAGCTAGCTGCAAGAGAAATAGTGTGGTTAGAAAGAGAAGAGC
GAGCCAGGCAGCACTACGAGAAGCACCTGGAAGAGCGGAAGAAGAGGTTGGAGGAGCAGAGGCAGAAGGA
GGAGCGGAGGAGGGCTGCTGTGGAGGAGAAGCGGAGGCAGAGACTTGAGGAGGACAAAGAACGCCACGAA
GCTGTTGTACGGCGCACAATGGAAAGGAGCCAGAAGCCAAAACAGAAGCATAACCGTTGGTCGTGGGGAG
GCTCTCTCCATGGGAGCCCTAGCATCCACAGTGCAGATCCAGACAGGCGGTCAGTTTCCACCATGAATCT
TTCGAAATATGTTGATCCCGTCATTAGCAAGCGGCTCTCCTCTTCATCTGCAACTTTACTAAATTCTCCA
GATAGAGCTCGCCGCCTGCAGCTCAGCCCATGGGAGAGCAGCGTTGTTAACAGACTCCTGACGCCCACAC
ATTCGTTCCTGGCCAGAAGTAAAAGCACAGCTGCCTTGTCTGGAGAAGCAGCATCTTGCAGCCCCATCAT
CATGCCCTACAAAGCTGCACACTCTAGAAATTCGATGGATCGACCAAAACTCTTTGTAACACCACCTGAG
GGCTCTTCTCGCAGGAGGATCATTCATGGCACAGCGAGCTATAAAAAAGAAAGAGAGAGAGAAAATGTAC
TCTTCCTCACATCTGGCACCCGAAGGGCTGTATCTCCATCTAATCCCAAAGCAAGACAACCAGCTCGCTC
CCGACTTTGGCTTCCGTCCAAGTCTCTTCCTCATTTGCCTGGCACACCCAGACCGACATCCTCCTTGCCA
CCCGGCTCAGTCAAAGCTGCTCCTGCTCAGGTCCGGCCCCCATCCCCCGGCAACATCCGCCCTGTCAAGA
GGGAAGTCAAAGTGGAGCCTGAGAAGAAAGATCCTGAGAAGGAACCTCAGAAAGTTGCCAATGAGCCCTC
ACTAAAGGGCAGAGCACCTTTAGTGAAGGTAGAAGAAGCCACAGTTGAAGAGCGGACACCTGCTGAACCA
GAAGTTGGCCCTGCTGCTCCAGCCATGGCCCCAGCTCCAGCCTCGGCCCCAGCTCCAGCCTCGGCCCCAG
CTCCAGCCCCGGTCCCCACCCCAGCCATGGTCTCAGCCCCGTCATCCACTGTGAATGCCAGTGCTTCTGT
TAAGACTTCTGCAGGCACCACCGACCCAGAGGAGGCCACAAGGCTTCTAGCTGAGAAGAGGCGGCTGGCC
CGAGAGCAGAGAGAAAAGGAAGAAAGGGAGAGGAGGGAGCAGGAAGAGCTTGAAAGACAAAAGAGAGAGG
AATTGGCTCAACGTGTGGCTGAAGAGAGGACGACTCGCCGTGAGGAGGAGTCGCGCAGGCTGGAAGCCGA
GCAGGCCCGGGAGAAGGAGGAGCAGCTGCAGCGGCAGGCGGAGGAGCGGGCGCTGCGCGAGCGGGAGGAG
GCAGAGCGCGCCCAGAGGCAGAAAGAAGAAGAAGCTCGCGTTCGTGAAGAAGCAGAGAGGGTCCGGCAGG
AACGAGAGAAGCATTTCCAGAGAGAAGAGCAAGAGCGCCTGGAGAGAAAGAAGCGACTTGAGGAGATTAT
GAAAAGAACCAGGAGAACAGAAGCTACAGATAAGAAAACCAGTGATCAGAGAAACGGTGATATAGCCAAG
GGAGCTCTCACTGGAGGAACAGAGGTGTCTGCACTTCCATGTACAACAAACGCTCCGGGAAATGGAAAGC
CAGTTGGCAGCCCACATGTGGTTACCTCACACCAGTCAAAAGTGACAGTGGAGAGCACTCCCGATTTGGA
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GGATCTAAACCATCCAGATTAGATGTCACCAACAGTGAGAGCCCAGAAATTCCTTTGAATCCAATTTTGG
CCTTTGATGATGAAGGGACACTTGGGCCCCTGCCTCAGGTAGATGGTGTTCAGACACAGCAGACTGCAGA
AGTTATATGA
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