| The somatic follicle cells of the Drosophila ovary play essential roles in the development of the egg and embryo. I have taken two approaches to the identification of genes required in the follicle cells for patterning. First, through an analysis of enhancer trap lines expressed in subsets of follicle cells, I have identified tandem Drosophila genes homologous to CTP: phosphocholine cytidylyltransferase (CCT), the second of three enzymes in the phosphatidylcholine biosynthesis pathway. Drosophila Cct1 is expressed at high levels in three specific subsets of follicle cells, and this expression is regulated, at least in part, by the TGF-β and Egfr signaling pathways. Mutations in Cct1 result in a number of defects, including a loss of germline stem cell maintenance, mispositioning of the oocyte, and a shortened operculum, suggesting that Cct1 plays multiple roles during oogenesis. In addition, Cct1 mutants display a novel branched ovariole phenotype, demonstrating a requirement for this gene during ovarian morphogenesis. These data provide the first evidence for a specific role for CCT, and thus for phosphatidylcholine, in patterning during development.; As a second approach to the identification of genes required in the follicle cells, I have performed a directed mosaic screen on the right arm of the third chromosome. 2197 chromosomes were screened, and 51 mutations were identified that affect patterning of the egg and embryo. These mutations result in novel phenotypes as well as defects in well characterized processes such as dorsal-ventral patterning.; In the preliminary characterization of mutations isolated in the mosaic follicle cell screen, one mutation was identified that appears to be required in the germline rather than the follicle cells. Eggs laid by females mutant for AB11 are extremely small in size and often dorsalized. The mutation has been mapped and an initial characterization of the mutation has been conducted. |
