From our data showing that neonatal treatment with the classic endocrine-disrupting agent diethylstilbestrol (DES) acts to alter estrogen responsiveness in the adult hamster uterus by a direct mechanism, we propose two related working hypotheses are: 1) The altered estrogen responsiveness that occurs in the adult hamster uterus is the result of neonatal DES-induced imbalances in the expression of key regulatory genes during early development; and 2) Stromal-epithelial interactions make it likely that DES- altered patterns of early gene expression will differ between the two tissue compartments. Based on these hypotheses, we will pursue the Specific Aim to: Identify the immediate cellular and molecular targets of the neonatal DES insult that cause inappropriate estrogen responses in the adult hamster uterus. Fortunately, improved versions of powerful new genetic screening and cloning strategies are now available in kit form and require very little total cellular RNA as starting material. Also, determining the cellular site of the immediate DES-induced alterations will be facilitated by our ability to cleanly separate the simple luminal epithelium from the relatively undifferentiated stromal compartment that is present in neonatal uteri. This screening effort should 1) generate a succession of newly identified genetic elements, several of which must be involved in important biological functions (estrogen-responsive proliferation/apoptosis/neoplasia), and 2) be followed by an ordered determination of each element s molecular structure and functional dynamics at the genomic, RNA, and protein level. The spectrum of research opportunities defined by each such process would encompass efforts at many levels including those appropriate for several of our independent faculty members, for post-doctoral research associates, or for our students at either the graduate or undergraduate level. Thus this project is particularly relevant to the stated purpose of the AREA Award Program. In addition to providing important mechanistic information about the controversial topic of perinatal endocrine disruption, this project will surely benefit our larger long-term objectives to: 1) Delineate the basic mechanisms whereby estrogen regulates normal uterine growth and morphogenesis, and 2) Identify mechanistic alterations that cause degeneration of the normal growth process and thereby leads to the unregulated neoplastic state. These are biomedically important because: 1) Successful conception and gestation demands normal uterine form and function, and 2) Estrogen-dependent uterine neoplasms are responsible for considerable morbidity and mortality in contemporary American society.