Regulation of IGFBP-1 by FKHR and HOXA10 in pregnancy

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DESCRIPTION (provided by applicant): The long-term objective of this application is to better understand the dynamic interaction that occurs between the conceptus and the mother that allow for the establishment and maintenance of pregnancy. The major focus of our research is on the molecular events that occur in the endometrium in response to early embryonic signals and the invading trophoblast. Aberrant expression of genes in the endometrium during this time is detrimental to the maintenance of pregnancy and could lead to miscarriages, spontaneous abortions and infertility. In response to pregnancy hormones and conceptus factors, the endometrium undergoes a major transformation, termed decidualization. During this process, the stromal cells of the endometrium express important genes. This study focuses on the regulation of a major secretory product of the decidualizing stromal cells, insulin-like growth factor binding protein-1 (IGFBP-1). IGFBP-1 modulates the actions of insulin-like growth factors (IGFs) which are critical during early pregnancy and can act independently of IGFs to regulate trophoblast invasion. Recently, we demonstrated that two transcription factors, FKHR and HOXA10, which have been demonstrated to be important in reproductive processes, interact with one another and up regulate the IGFBP-1 promoter in a cooperative manner in endometrial stromal cells. Based on this novel data, studies have been designed to further delineate the mechanisms involved in the cooperative up regulation of the IGFBP-1 promoter by FKHR and HOXA10. In aim 1 the binding sites of FKHR and HOXA10 on the IGFBP-1 promoter are identified. With the use of a powerful new technique, chromatin immunoprecipitation (CHIP), the binding sites for endogenous FKHR and HOXA10 proteins on the endogenous IGFBP-1 gene within the chromatin in the decidualized stromal cells are determined. This technique allows one to study interaction of transcription factors with the chromatin as they occur in situ. In aim 2, characterization of FKHR and HOXA10 and determination of binding sequences on the IGFBP-1 gene in cells originating from non-pregnant and pregnant baboon endometrium will be performed by taking "snapshots" of the cells and tissue using formaldehyde cross linking. These studies will demonstrate the influence of the conceptus on FKHR and HOXA10 expression and their activation of the IGFBP-1 gene. In aim 3, FKHR and HOXA10 expression and activity in the endometrium of baboons with endometriosis will be studied. The objective of aim 3 is to determine why FKHR and HOXA10 do not significantly activate the IGFBP-1 promoter. The stromal cells from baboons with endometriosis are obviously different from that of a normal animal. These studies will give a better understanding of the molecular events that may be associated with increased implantation failure in women with endometriosis. The three aims in this application will provide valuable insights into the molecular dynamics of the endometrium in response to pregnancy.