The WNT family of signaling molecules has been identified as potential key regulators of normal ovarian function in the adult female. It is known that WNT proteins are required for early ovarian development and that mice lacking Wnt4 have sex-reversed ovaries, express genes associated with testes development and exhibit a reduced number of oocytes at birth. Additionally, misregulated [unreadable]-catenin signaling in mice with granulosa cell-specific alleles encoding constitutively active [unreadable]-catenin results in subfertility and the development of late onset granulosa cell tumors. Expression and hormonal regulation of several members of the WNT and Frizzled families have been reported in the adult rodent ovary and the downstream regulator of the WNT signaling pathway, [unreadable]-catenin, has been shown to play a role in ovarian steroidogenesis. Moreover, reduction of [unreadable]-catenin in granulosa cells compromises FSH stimulation of aromatase mRNA and resultant estradiol production. Despite emerging evidence as to the importance of the WNT signaling pathway in regulating ovarian development and steroid production, very little is known about the regulation of WNTs in the adult ovary. Identification of additional factors and mechanisms, such as WNT, that contribute to ovarian steroid production will provide insight to how these signals may impact estrogen levels in health and disease. Our long-term goal is to describe the mechanisms regulating WNT signaling in the adult ovary. The immediate goal of this application is to determine granulosa cell specific targets of the WNT signaling pathway and delineate how these targets are hormonally regulated. To accomplish the overall objective of this application the following specific aims will be pursued: 1. Determine the mechanisms by which FSH and WNT work together to regulate aromatase gene expression which is ultimately responsible for induction of ovarian estradiol production. 2. Investigate the common network of genes regulated by WNT and FSH in granulosa cells using microarray analysis to map the gene expression profiles in primary cultures of rat granulosa cells. This research will provide new targets and strategies to expand our knowledge about hormonal regulation of folliculogenesis and could improve treatments for female factor infertility and ovarian pathologies. PUBLIC HEALTH RELEVANCE: In humans, local and circulating estrogen levels influence numerous physiological and pathological processes including fertility and sexual behavior, bone remodeling and the development of various endocrine cancers. WNTs comprise a family of secreted glycoproteins that are key extracellular signaling proteins necessary for early ovarian development and steroidogenesis;aberrant regulation of the downstream co-activator of WNT signaling, [unreadable]-catenin has been shown to cause cancer in a number of tissues including granulosa cells. Understanding the role of WNT/ [unreadable]-catenin in the ovary and how this pathway converges with other extracellular signals will allow greater perspective on how these signals impact follicular maturation and estrogen levels in health and disease.