Yamazaki Tomoko, Yoshimatsu Yasuhiro, Morishita Yasuyuki, Miyazono Kohei, Watabe Tetsuro
Department of Molecular Pathology, Graduate School of Medicine,Global Center of Excellence Program for Integrative Life Science Based on the Study of Biosignaling Mechanisms, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
Genes Cells. 2009 Mar;14(3):425-34. doi: 10.1111/j.1365-2443.2008.01279.x. Epub 2009 Feb 4.
During embryonic lymphatic development, Prox1 homeobox transcription factor is expressed in a subset of venous blood vascular endothelial cells (BECs) in which COUP-TFII orphan nuclear receptor is highly expressed. Prox1 induces differentiation of BECs into lymphatic endothelial cells (LECs) by inducing the expression of various LEC markers including vascular endothelial growth factor receptor 3 (VEGFR3). However, the molecular mechanisms of how transcriptional activities of Prox1 are regulated are largely unknown. In the present study, we show that COUP-TFII plays important roles in the regulation of the function of Prox1. In BECs and LECs, Prox1 promotes the proliferation and migration toward VEGF-C by inducing the expression of cyclin E1 and VEGFR3, respectively. Gain-of-function studies showed that COUP-TFII negatively regulates the effects of Prox1 in BECs and LECs whereas loss-of-function studies showed that COUP-TFII negatively and positively regulates Prox1 in BECs and LECs, respectively. We also show that endogenous Prox1 and COUP-TFII physically interact in LECs and that both Prox1 and COUP-TFII bind to the endogenous cyclin E1 promoter. These results suggest that COUP-TFII physically and functionally interact during differentiation and maintenance of lymphatic vessels.
在胚胎淋巴管发育过程中，Prox1同源框转录因子在静脉血管内皮细胞（BECs）的一个亚群中表达，其中COUP-TFII孤儿核受体高度表达。Prox1通过诱导包括血管内皮生长因子受体3（VEGFR3）在内的各种淋巴管内皮细胞（LECs）标志物的表达，诱导BECs分化为LECs。然而，Prox1转录活性如何被调控的分子机制在很大程度上尚不清楚。在本研究中，我们表明COUP-TFII在Prox1功能的调控中起重要作用。在BECs和LECs中，Prox1分别通过诱导细胞周期蛋白E1和VEGFR3的表达，促进细胞增殖并向VEGF-C迁移。功能获得性研究表明，COUP-TFII在BECs和LECs中负向调节Prox1的作用，而功能缺失性研究表明，COUP-TFII在BECs中负向调节Prox1，在LECs中正向调节Prox1。我们还表明，内源性Prox1和COUP-TFII在LECs中发生物理相互作用，并且Prox1和COUP-TFII都与内源性细胞周期蛋白E1启动子结合。这些结果表明，COUP-TFII在淋巴管的分化和维持过程中发生物理和功能相互作用。
