Spatial and temporal control of meiosis

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Egg activation is the process by which a mature egg is triggered to complete meiosis and at the same time to undergo critical developmental changes that prepare the egg for subsequent embryonic development. The cort gene, which encodes a meiosis-specific activator of the Anaphase Promoting Complex (APC/C), is involved in almost all aspects of egg activation. A small number of other genes have also been implicated in egg activation, including the CanB2 phosphatase and CycB3-Cdk1. A major goal of our research is to determine how these genes interact to promote the completion of meiosis. We are also interested in discovering how these cell cycle regulators also control critical developmental processes that are linked to egg activation. ******Aim 1. Regulation of the APC/C in Drosophila meiosis. In Aim 1 we use mass-spectrometry (MS) to identify subunits of Cort and Fzy APC/C complexes and identify post-translational modifications that change with egg activation. We will determine how CanB2 and CycB3 regulate the APC/C in meiosis by comparing MS profiles of Cort and Fzy in wild type versus mutants for these genes. To complement this biochemical approach, we employ a deficiency screen to probe the entire genome for genes that enhance or suppress cycB3 gain or loss-of-function alleles. Also in Aim 1 we will follow up on our surprising finding that Rca1, an inhibitor of APC/CFzr, has an APC/C activating role in meiosis. ******Aim 2. Determine how chromosomes segregate in meiosis. We found that chromosome segregation in Drosophila meiosis requires the protease, Separase, and the APC/C-mediated degradation of its inhibitor Securin. A major goal in this Aim is to identify the Separase target. Also in Aim 2 we evaluate the role of Cort, CanB2, CycB3 and Rca1 in the release of arm cohesion, and we follow up on our finding that CycB-Cdk1 plays a role in chromosome segregation in meiosis. We also determine if Separase is controlled locally in meiosis, possibly by Securin or CycB. ******Aim 3. Determine role of APC/CCort in sex determination. We uncovered a novel role for the APC/C in sex determination. We will test our model that APC/CCort targets a key regulator of sex determination, Tra for destruction. We propose that Cort acts in female germline to prevent maternal Tra from committing the embryo to a female fate. We propose that this role for Cort is particularly important in insect species in which Tra is the master regulator of sex determination. We will directly test this using the medfly as a model.******This research program will directly train 3 PhD and 20 undergraduate students. All will receive a high level of training in a broad range of molecular, genetics, biochemistry, and biological imaging techniques. All students will be trained in scientific method, they will develop their ability to design and interpret experiments and they will learn to write and present their work. Students will be highly qualified for jobs in research, teaching and industry.