9306159 Mahowald The ovarian follicle in most animal species becomes surrounded by a follicular epithelium soon after the inception of meiosis. A class of genes in Drosophila melanogaster have been identified that are required both for the establishment of individual follicles and for the embryonic segregation of neuroblasts. Developmental analysis of brainiac (brn), an example of this class, suggests that it provides an essential germline signal, required for normal migration of the prefollicular cells to surround individual egg chambers. Weak mutations in the torpedo gene (the homologue for the epidermal growth factor receptor in Drosophila) display a strong enhancement of the mutant phenotype, indicating that this follicle cell function may be the mediator of the germline brn signal. The brn gene has been mapped molecularly; it will be cloned, sequenced, antibodies prepared and its expression analyzed in both wild type and mutant ovaries (mutant for genes required for ovarian structure or neurogenesis). Interactions between brn and other neurogenic genes will be tested in transfected tissue culture cells. Finally, mutation screens to identify interacting genes and other genes in the neurogenic class will be conducted. These studies should provide a first analysis of the molecular control of ovarian follicle formation. ***
