Abstract 4847: COUP-TFII Inhibits Expression of Transcription Factor Hey2 in Human Arterial Endothelial Cells
Normal development of an organism requires formation, differentiation and stabilization of blood vessels. Furthermore, many diseases have their origin in disturbed arterial and venous function, e.g. coronary artery disease, peripheral arterial occlusive disease or deep-vein thrombosis. Arteries and veins differ not only in their physiology, but also in their structure. We identified two transcription factors specifically expressed in venous (COUP-TFII) or in arterial endothelial cells (Hey2). In this study, we analyzed a potential direct molecular interaction of these two determinants of an arterial and venous phenotype. Using lentiviral gene transfer, we overexpressed venous marker gene COUP-TFII in human primary arterial endothelial cells. Using this approach, we reached high transduction efficiency of HUAEC. We were able to show, that the overexpressed transcription factor COUP-TFII was correctly processed and transported into the nucleus. More importantly, COUP-TFII overexpression caused downregulation of arterial marker gene Hey2. These data suggested that COUP-TFII could be a direct repressor of Hey2. Using two independent methods, chromatin immunoprecipitation and electrophoretic mobility shift assay, we can show that COUP-TFII binds to the Hey2 promoter thus repressing its activity. This was confirmed by COUP-TFII supershift strongly supporting a direct interaction of COUP-TFII with the Hey2 promoter. In conclusion, using lentiviral gene transfer allowing efficient and stabile transduction of primary endothelial cells, we were able to show that the venous marker gene COUP-TFII downregulates the expression of the arterial marker gene Hey2 in primary arterial endothelial cells. Additional analysis confirmed that the transcription factor COUP-TFII directly binds to specific sites of the Hey2 promoter, thus leading to the downregulation of its expression. This is a novel molecular mechanism defining an arterial or venous phenotype in human endothelial cells.