Cell type specificity and heterogeneity of endothelial specific gene regulation

多细胞生物中的特定细胞类型如何获得其独特的特征，使其区别于其他细胞类型，仍然是一个悬而未决的生物学问题。例如，排列在血管内侧的细胞，被称为内皮细胞，是如何获得其独特的特征，使其不同于神经细胞或皮肤上皮细胞的。关于内皮细胞（启动血管网络形成的细胞类型）如何获得其特定特征的理解，这个谜团仍然没有得到明确的解决。此外，各器官血管床的内皮细胞并不相同，在结构和功能上也存在差异。这种“内皮细胞异质性”是为了满足不同器官的特殊需要而进化的。内皮细胞异质性的分子基础仍不清楚。关于内皮细胞如何建立其独特的细胞身份，以及它们如何获得器官特异性特征，这是我们研究计划的长期目标，目前我们的知识存在重大差距。我们研究计划的具体短期目标是通过探索内皮细胞表型被撤销和重新建立时哪些转录和表观遗传调节因子被改变，以及这些改变如何与内皮特定基因的调节相关，来解决这一差距。我们建立了一个由人脐静脉内皮细胞生成诱导多能干细胞（iPS），然后分化为非内皮细胞，再分化回内皮细胞的系统。该系统提供了一个独特的机会，作为一个体外模拟发育过程，探索内皮特异性基因，包括血管性血液病因子（VWF）的抑制（当内皮细胞转变为iPS时）和激活（当iPS转变为内皮细胞时）的分子基础。由于我们之前的研究，我们已经产生了一套独特的工具，包括内皮特异性启动子与器官特异性激活模式；以及有关参与VWF转录调控的交易因子的知识。我们现在建议使用这些工具、生成的信息和内皮- ips -内皮分化系统来确定限制VWF的机制，以及其他内皮特异性基因在内皮细胞中的表达。我们还建议探索不同血管床内皮细胞中靶内皮特异性基因（如VWF）的表达如何受到差异调节。所获得的信息将有助于理解内皮细胞表型及其异质性是如何通过理解内皮细胞特异性基因的细胞类型和器官特异性调节的分子机制来完成的。

How a specific cell type in a multicellular organism acquire its unique characteristics, which distinguishes it from other cell types, remains an unanswered biological question. For example how do cells that line inner side of blood vessels, known as endothelial cells, acquire their unique characteristics that makes them different from, for instance neuronal cells, or skin epithelial cells. This mystery has remained specifically unresolved with regard to understanding how endothelial cells- the cell type that initiate vascular network formation - acquire their specific characteristics. Furthermore, endothelial cells of vascular beds in various organs are not identical and exhibit differences in structure and function from each other. This "endothelial cell heterogeneity" is evolved to meet the specialized needs of different organs. The molecular basis of endothelial cell heterogeneity also remains unknown. There is a major gap in our current knowledge regarding how endothelial cells establish their unique cellular identity, and how they acquire organ-specific characteristics, which is the long-term objective of our research program. The specific short-term objective of our research program is designed to address this gap through exploring which transcriptional and epigenetic regulators are altered when endothelial cell phenotype is revoked and re-established and how do these alterations correlate with regulation of endothelial specific genes. We have established a system in which induced pluripotent stem cells (iPS) are generated from human umbilical vein endothelial cells, and then differentiated into non-endothelial, as well as back into endothelial cells. This system has provided a unique opportunity, as an in vitro mimicry of developmental process, to explore the molecular basis of repression (when changing endothelial cells to iPS) and activation (when changing iPS back to endothelial cells) of endothelial specific genes, including von Willebrand factor (VWF). As a result of our previous studies, we have generated a set of unique tools, including endothelial specific promoters with organ-specific activation patterns; as well as knowledge regarding transacting factors that participate in regulation of VWF transcription. We now propose to use these tools, generated information, and endothelial-iPS-endothelial differentiation system to determine the mechanisms that restrict VWF, as well as other endothelial specific genes' expression to endothelial cells in general. We also propose to explore how the expression of target endothelial specific genes, such as VWF is differentially regulated in endothelial cells of distinct vascular beds. The information obtained will provide insights towards understanding how endothelial cells phenotype and it's heterogeneity is accomplished through understanding the molecular mechanisms that contribute to cell type and organ-specific regulation of endothelial specific genes.