Mitotic segregation defects such as multipolar spindles, anaphase bridges, and micronuclei have long been observed in cancer cells, but it is not known whether these defects lead to aneuploidy or even contribute to tumorigenesis. We visualize living oral squamous carcinoma cells with stable expression of GFP-histone H2B fusion. Expression of this fusion protein labels chromosomes clearly and does not disrupt the cell cycle, alter the doubling time or produce any defects previously unseen in fixed cells. These carcinoma cells survive the formation of anaphase bridges and micronuclei and complete a second cell division in the same amount of time as unaffected cells. Micronuclei were formed after every division that contained an anaphase bridge in cells we examined. Most often, each daughter cell contained a micronucleus. These results suggest that the chromosome breaks at multiple points along its length and breaking may not be due to a "tug of war" between spindle poles. The movement of micronuclei was very dynamic compared to the nuclei during interphase and micronuclei do not appear to be transcriptionally active. Using long-term live cell imaging we were also able to observe the fate of these cells through two divisions and have determined the length of each phase of mitosis. Anaphase bridges and lagging metaphase chromosomes both lengthen mitosis, suggesting that the mitotic spindle checkpoints are at least partially active in cells. The mitotic delays occurred during metaphase in these defective cells. We have also analyzed centrosomal components including the mitotic apparatus protein, NUMA. No correlations were found between protein expression of NuMA and gene amplification or segregation defects. In summary, we have shown that cells continue to proliferate after the occurrence of mitotic defects and these defects contribute to chromosomal instability.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-05072002-121540 |
| Date | 16 July 2002 |
| Creators | Hoffelder, Diane R. |
| Contributors | Jeffrey Brodsky, Deborah L. Chapman, Jeffrey Hildebrand, William S. Saunders |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf, video/quicktime |
| Source | http://etd.library.pitt.edu:80/ETD/available/etd-05072002-121540/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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