In all animal cells, the rise and fall of cyclin controls the entry into and exit out of mitosis. The objective of this investigation is to link gene products that regulate the cell cycle in the nucleus with the dynamic regulation of the cytoskeleton in the cytoplasm. Changes in the cytoskeleton cause chromatids to segregate and cells to cleave. But the cytoskeleton is also responsible for movements of the nuclei within the cell and for cell shape changes. To study the role of cyclin in shaping the cytoskeleton, the PI will use the early Drosophila embryo because the first divisions are nuclear and take place within a single cell, the cycle is synchronous, and the regulation of the divisions depends entirely on maternal contributions. By increasing and decreasing cyclin gene dose in the mother, the PI can define the role that cyclin has in microtubule and microfilament dynamics. The PI has found that increased cyclin results in faster and more complete microtubule breakdown. To identify other genes, which collaborate with cyclin and affect the microtubule dynamics, the PI has proposed a genetic screen. During the early stages of embryogenesis in Drosophila, nuclei move in a specific phase of the cell cycle. This movement depends on the specific breakdown of the microfilament network. The dynamics of the microfilaments depend on several specific, known proteins, and we will characterize their role by changing their gene dose in the mother. Several characterized proteins are known to regulate microfilament dynamics. The PI will define their role by changing their gene dose in the mother.
