The goal of the proposed research is to determine the mechanisms by which the FOXO boxO transcription factors, FSH and ovarian---derived growth factors (activin and BMP2) regulate ovarian follicular growth and apoptosis and hence fertility. By disrupting the Foxo1 and Foxo3 genes selectively in granulosa cells, we have generated mice that are infertile with a novel phenotype that is distinct from all other known mutations in granulosa cells. The infertile phenotype can be traced to: 1) Reduced follicle growth and apoptosis leading us to discover a new paradigm: that FOXO1/3 act in granulosa cells to mediate both follicle maturation and apoptosis, and that these distinct functions of FOXO1/3 are tightly linked to specific interactions with either the activin or BMP2 signaling pathways, respectively. 2) Defective oocyte development that appears to be mediated primarily by changes in metabolic/endocrine factors emanating from the mutant cumulus cells. Analyses of cumulus and oocyte functions in the mutant mice should lead us to discover specific FOXO1/3 targets that regulate of oocyte maturation and 3) Alterations in ovarian feedback to the pituitary leading to suppressed FSH that appears to be mediated by a novel ovarian---derived factor that is not inhibin. Characterizing a new Fshb suppressor(s) has far---ranging implications for developing alternative contraceptive targets. Thus, the Foxo1/3 conditional KO mice provide a unique model in which to determine the physiological, molecular and biochemical mechanisms by which these transcriptional regulators impact apoptosis, oocyte maturation and ovarian production of a novel factor(s) that suppresses pituitary Fshb expression. To analyze these functions of Foxo1/3 that control reproductive success, we propose the following Specific Aims: I) Determine how interactions between FSH, activin, BMP2 and FOXO1/3 impact granulosa cell apoptosis in intact follicles. II) Determine the changes in cumulus cell and oocyte functions in the Foxo1/3 mutant mice that impact fertility. III) Characterize the novel Fshb inhibitory factor(s that emanate from the Foxo1/3 mutant ovaries.
Depleting Foxo1/3 in granulosa cells exerts a profound effect on follicle growth, apoptosis, oocyte maturation and pituitary functions underscoring the central role of these transcriptional regulators in ovarian biology and reproductive success. Thus, endocrine and paracrine pathways that regulate FOXO1/3 can profoundly impact fertility and likely contribute to follicular dysfunction in women with PCOS and premature ovarian failure. Results should lead to new strategies for improved IVF procedures and contraceptives.
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