A Nuclear Receptor COUP-TFII in Cardiovascular Function

描述(申请人提供)：COUP-TFII是一种孤儿核受体，属于类固醇受体超家族。由于血管生成和心脏发育的缺陷，在小鼠体内消融COUP-TFII会导致早期胚胎死亡。为了进一步了解COUP-TFII在血管和心脏发育中的生物学功能，我们产生了LacZ敲入和FLOXD COUP-TFII小鼠。LacZ基因敲除小鼠的X-Gal染色显示，Coup-TFII在静脉内皮细胞中高表达，而在动脉中不表达。此外，嵌合体分析表明，Coup-TFII在静脉内皮细胞中发挥细胞自主功能，但在动脉中不起作用。这些研究首次表明COUP-TFII是静脉识别所必需的转录因子。在COUP-TFII基因座插入loxP位点，降低了COUP-TFII的表达，使COUP-TFII FLOX/-突变体发生了基因亚型变异。这些亚型突变表现为房室间隔缺陷(AVSD)，常见于先天性心脏病患者。COUP-TFII缺失型突变体与低态突变型AVSD结合后所表现出的心房畸形提示COUP-TFII在心脏发生中起重要作用。心脏缺陷是固有的还是继发于血管缺陷目前尚不清楚。心脏的正常发育需要心内膜和心肌之间的协调相互作用。心内膜内皮细胞还是心肌内的心肌细胞是COUP-TFII调控的靶点也不清楚。为了阐明COUP-TFII在维持静脉特性和心脏发育中的作用，提出了两个特定的目标。在目标1中，我们将利用内皮细胞中COUP-TFII的功能获得和功能丧失来研究COUP-TFII在维持动静脉特性中的作用。此外，我们将使用DMA芯片微阵列分析来确定在动静脉决策中受COUP-TFII调控的新的下游靶点和信号通路。在目标2中，我们将使用亚形态突变和内皮和心肌条件性COUP-TFII基因敲除来研究COUP-TFII在心脏发育中的作用。这项研究将使我们能够确定内皮COUP-TFII和心肌COUP-TFII如何影响心脏发生，以及COUP-TFII如何调节心肌和心内膜之间的相互作用。我们提出的研究将及时为COUP-TFII如何影响心血管发育提供新的见解，并促进先天性心脏病的诊断和治疗。

DESCRIPTION (provided by applicant): COUP-TFII is an orphan nuclear receptor that belongs to the steroid receptor superfamily. Ablation of COUP-TFII in mice results in early embryonic lethality due to defects in angiogenesis and heart development. To further understand the biological functions of COUP-TFII in vascular and heart development, LacZ knock-in and floxed COUP-TFII mice were generated. X-Gal staining of the LacZ knock-in mice shows high COUP-TFII expression in the endothelium of the vein but not in the artery. Further, chimera analysis showed that COUP-TFII plays a cell autonomous function in the endothelial cells of the vein but not the artery. These studies show for the first time that COUP-TFII is an essential transcription factor for vein identify. The insertion of loxP site into the COUP-TFII locus reduced the expression of COUP-TFII, rendering the COUP-TFII flox/- mutants genetically hypomorphic. The hypomorphic mutants exhibit atrioventricular septal defects (AVSD) commonly observed in congenital heart disease patients. The atrium malformation displayed by the COUP-TFII null mutant coupled with AVSD elicited by the hypomorphic mutant together suggest that COUP-TFII plays a critical role in cardiogenesis. Whether the heart defects are intrinsic or secondary to the vascular defects is currently unknown. Proper heart development requires the coordinated interactions between the endocardium and myocardium. Whether the endothelial cells in the endocardium or the myocardial cells in the myocardium are the targets of COUP-TFII regulation is also unclear. To elucidate the role of COUP-TFII in the maintenance of vein identity and in heart development, two Specific Aims are proposed. In Aim 1, we will employ gain-of-function and loss-of-function of COUP-TFII in the endothelial cells to examine the role of COUP-TFII in the maintenance of arteriovenous identity. In addition, we will use DMA chip microarray analysis to identify novel downstream targets and signaling pathways that are regulated by COUP-TFII in the arteriovenous decision. In Aim 2, we will use the hypomorphic mutant and the endothelial and myocardial conditional COUP-TFII knockouts to investigate the role of COUP-TFII in heart development. This study will enable us to determine how endothelial COUP-TFII versus myocardial COUP-TFII affects cardiogenesis and how COUP-TFII modulates the interaction between the myocardium and endocardium. Our proposed studies should provide timely new insights into how COUP-TFII impacts cardiovascular development and facilitate the diagnosis and treatment of congenital heart disease.