Oocyte development in Drosophila

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DESCRIPTION (provided by applicant): The long-term goal of this project is to elucidate mechanisms of gamete development using Drosophila oogenesis as a model system, and the powerful tools available for genetic and cell biological approaches in Drosophila. A significant health concern is the survival of germline cells in adults exposed to environmental stresses such as poor nutrition and exposure to aggressive pharmaceuticals. Research carried out in this project will impact understanding of protective mechanisms used by immature gametes to ensure their survival through harsh conditions. This project will also investigate a fundamental and conserved aspect of gamete development - some or all of animal gametogenesis occurs in syncytial clusters of cells connected by intercellular bridges called ring canals. Mechanisms modulating intercellular movement of cytoplasm through germline ring canals in response to nutrient availability will be examined. Ring canals are also present between somatic follicle cells of the Drosophila egg chamber, although their function is not known. This project will investigate movement of cytoplasmic components through somatic ring canals, and use novel approaches for disrupting somatic ring canals to determine their function. This information will impact understanding of intercellular movement through small ring canals similar to those connecting developing spermatocytes. In addition, tools developed in this research will be useful for examining somatic ring canals in other Drosophila tissues. Aim 1 will use genetic approaches to determine the mechanism of the starvation response in oocyte development, by manipulating components of the Drosophila Insulin/insulin-like (IIS)/Tor pathway. Previtellogenic egg chambers mount a response to poor nutrition that includes enlarged P bodies and reorganization of the microtubules. Multiple components of the IIS/Tor pathway will be expressed or knocked down, individually or in combinations, in either the germline or the follicle cell tissues to characterize the consequences in starved egg chambers. New approaches will allow tracking of egg chambers that have been starved to examine their recovery in detail, and mutants affecting P body assembly will be used determine the consequences of crippling the starvation response. Aim 2 will use new cell marking techniques and fluorescent proteins to illuminate the function of ring canals in the follicle cell epithelium that surrounds the egg chamber. Experiments will determine whether ring canals serve to equilibrate protein levels between transcriptionally uncoordinated cells. New methods for targeted disruption of somatic ring canals will allow phenotypic analysis of disrupted syncytia, which have been elusive. The importance of the role that follicle cell syncytia play during egg chamber development will be better defined following these studies, and these new methods can then be applied to other somatic syncytia involved in development in Drosophila.