The Role of ARNT in Endothelial Cells

描述(申请人提供)：缺氧诱导因子(HIF)是组织O2水平的关键感应器，并在胚胎发育过程中以及在伤口愈合和缺血等出生后病理中调控血管生成基因表达程序。原则上，HIF参与了重要的遗传程序，负责减缓和控制血管生长。由于多种心血管异常，缺乏HIF的小鼠表现出发育停滞。然而，HIF-规范通路在血管内皮细胞(ECs)中的特定作用缺乏意义。这一应用的长期研究目标是确定HIF如何响应低氧(低氧)环境，调节维持组织内稳所必需的血管生长。已有研究表明，HIF的比活性依赖于细胞和上下文。这一建议解决了一个普遍的假设，即EC-HIF激活不同的基因，在血管发育的不同阶段和出生后血管生成中调节特定类型的血管生长。我们将进一步确定HIF是否在低氧条件下调节血管内皮生长因子受体的瞬时表达，而血管内皮生长因子受体在介导内皮细胞的特定信号，包括其生存、增殖和行为方面非常重要。实验设计利用ARNT条件(血管中HIF-2强制性亚单位)小鼠遗传系统，该系统在胚胎发育的不同阶段以及成人血管中完全灭活内皮细胞中的低氧诱导因子转录活性，从而能够研究低氧诱导因子在血管建立、成熟和维持以及血管损伤反应中在内皮细胞中的需求(S)和角色(S)。具体目标1将研究在胚胎发育的关键阶段ECs中的HIF失活如何导致特定的血管生成缺陷。目的2探讨成人血管动态平衡和各种血管反应(新生血管生成、血管生成和动脉生成)对缺氧诱导因子的要求(S)。最后，目标3将检查内皮细胞内HIF的内在要求，并验证HIF在促进EC存活方面的重要假设，部分是通过调节VEGF受体的表达来实现的。本文提出的研究旨在扩大我们对缺氧在正常和病理环境下调节血管生成和动态平衡的机制的理解。 公共卫生相关性：血管发育和/或维护缺陷是多种人类病理性血管疾病的特征，包括肿瘤发生和组织缺血。通过体内遗传学方法，我们可以有条不紊地研究由内皮HIF转录反应驱动的生物学和分子血管过程。这项工作将提供一个分子框架，旨在了解在胚胎和成年观察到的生理和病理血管反应过程中，内皮细胞中HIF活性的生物学意义。这种研究具有重要的临床意义，因为它可以为针对血管生长过程的治疗药物的开发提供新的方向。

DESCRIPTION (provided by applicant): Hypoxia Inducible Factor (HIF) is a critical sensor of tissue O2 levels and governs angiogenic gene expression programs operating during embryogenesis as well as in post-natal pathologies including wound healing and ischemia. In principle, HIF contributes to important genetic programs responsible for moderating and controlling vascular growth. Mice deficient in HIF display developmental arrest due to multiple cardiovascular anomalies. However, the significance of a specific role for the HIF-canonical pathway in vascular endothelial cells (ECs) is lacking. The long-term research objective of this application is to determine how HIF, in response to the hypoxic (low oxygen) environment, regulates vascular growth necessary for maintaining tissue homeostasis. It has been demonstrated the specific activity of HIF is cell- and context- dependent. This proposal addresses the general hypothesis that EC- HIF activates distinct genes regulating specific types of vessel growth at various stages of vascular development and in post-natal angiogenesis. We will further determine whether HIF, in response to hypoxia, moderates the temporal expression of VEGF receptors that are important in mediating specific signals in ECs including their survival, proliferation, and behavior. The experimental design utilizes an Arnt-conditional (HIF-2 obligatory subunit in vessels) mouse genetic system that completely inactivates HIF-transcriptional activity in ECs at various stages of embryonic development as well as in the adult vasculature enabling the investigations of HIF's requirement(s) and role(s) within ECs during the establishment, maturation, and maintenance of blood vessels as well as in response to vascular injury. Specific Aim 1 will examine how HIF inactivation in ECs at critical stages of embryonic development lead to specific angiogenic defects. Aim 2 addresses the requirement(s) for HIF in adult vessel homeostasis and various types of vascular responses (neoangiogenesis, angiogenesis, and arteriogenesis). Finally, Aim 3 will examine the intrinsic requirements of HIF within ECs and test the hypothesis that HIF is important in promoting EC survival in part by regulating the expression of VEGF receptors. The studies proposed herein intend to expand our understanding of the mechanisms by which hypoxia regulates vessel generation and homeostasis in both normal and pathological settings. PUBLIC HEALTH RELEVANCE: Defective vessel development and/or maintenance is a feature of multiple human pathological vascular diseases including tumorigenesis and tissue ischemia. By using in vivo genetic approaches, we can methodically investigate the biological and molecular vascular processes driven by endothelial HIF transcriptional responses. This work will provide a molecular framework aimed at understanding the biological significance of HIF activity in endothelial cells during physiological and pathological vascular responses observed in embryos and adults. Such investigation is of clinical importance since it can provide new directions for the development of therapeutic agents targeting vascular growth processes.