Nuclear divison of Sarcocystis neurona
Morrison, David Patrick
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The phylum Apicomplexa contains unicellular parasites that cause numerous important diseases in humans and domestic animals. We study fundamental biological processes in these pathogens to identify new targets for disease intervention. This thesis focuses on the unique cell division mechanisms employed by these organisms. Using light and electron microscopy we demonstrate that in the model organism Sarcocystis neurona the mitotic spindle persists throughout the entire cell cycle. The interphase mini-spindles in this study could provide a scaffold to organize the many chromosomes in the polyploid nucleus of S. neurona by constant kinetochore interaction. Fluoresence in situ hybridization (FISH) analysis demonstrates that chromosomes are distributed through the nucleus in a regular pattern. We also characterized two kinetochore proteins in Toxoplasma gondii, CenH3 and Bub3, which will be used in the future to establishing kinetochore markers to further test this model. Lastly we have analyzed the modification status of nuclear histone proteins using a battery of diagnostic antibodies throughout the cell cycle. We found an abundance of euchromatic histone modifications (mH3K4 or aH3K9) and little or no histone modifications associated with condensation (mH3K9 or pH3S10). This data suggests that apicomplexan chromosomes remain in an uncondensed state throughout.