In my thesis I aimed to contribute to the understanding of the mechanism of cytokinesis in C. elegans embryos. I wanted to analyze the relative contributions of different spindle parts – microtubule asters and the midzone - to cytokinesis furrow positioning. I developed a UV laser-based severing assay that allows the spatial separation of the region midway between the asters and the spindle midzone. The spindle is severed asymmetrically between one aster and the midzone. I found that the spindle provides two consecutive signals that can each position a cytokinesis furrow: microtubule asters provide a first signal, and the spindle midzone provides a second signal. The use of mutants that do not form a midzone suggested that the aster-positioned furrow is able to divide the cell alone without a spindle midzone. Analysis of cytokinesis in hypercontracile mutants suggests that the aster-positioned cytokinesis furrow and the midzone positioned furrow inhibit each other by competing for cortical contractile elements. I then wanted to identify the molecular pathway responsible for cytokinesis furrow positioning in response to the microtubule asters. To this end, I performed an RNAi screen, which identified a role for LET-99 in cytokinesis: LET-99 appeared to be required for aster-positioned cytokinesis but not midzone-positioned cytokinesis. LET-99 localizes as a cortical band that overlaps with the cytokinesis furrow. Mechanical displacement of the spindle demonstrated that the spindle positions cortical LET-99 at the site of furrow formation. The furrow localization of LET-99 depended on G proteins, and consistent with this finding, G proteins are also required for aster-positioned cytokinesis. (Anlage: Quick time movies, 466, 67 MB)
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa.de:swb:14-1170257008922-66010 |
| Date | 31 January 2007 |
| Creators | Bringmann, Henrik Philipp |
| Contributors | Technische Universität Dresden, Biologie, Dr. Tony Hyman, Dr. Joe Howard, Dr. Thomas Surrey, Dr. Tony Hyman |
| Publisher | Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/pdf, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, video/quicktime, application/msword, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, video/x-flv, application/zip |
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