The Role of ARNT in Endothelial Cells

描述（由申请人提供）：缺氧诱导因子（HIF）是组织O2水平的关键传感器，并控制胚胎发生期间以及出生后病理学（包括伤口愈合和缺血）中的血管生成基因表达程序。原则上，HIF有助于调节和控制血管生长的重要遗传程序。缺乏HIF的小鼠由于多种心血管异常而显示发育停滞。然而，HIF-经典途径在血管内皮细胞（EC）中的特定作用的意义是缺乏的。本申请的长期研究目标是确定HIF如何响应于缺氧（低氧）环境来调节维持组织稳态所必需的血管生长。研究表明，HIF的特异性活性是细胞和环境依赖性的.该建议解决了一般假设，即EC-HIF激活不同的基因，在血管发育的各个阶段和出生后血管生成中调节特定类型的血管生长。我们将进一步确定是否HIF，在响应缺氧，调节VEGF受体的时间表达，这是重要的介导特定的信号在内皮细胞，包括他们的生存，增殖和行为。实验设计利用Arnt条件（血管中的HIF-2强制性亚基）小鼠遗传系统，其完全灭活胚胎发育的各个阶段的EC中以及成年脉管系统中的HIF转录活性，使得能够研究在血管的建立、成熟和维持期间以及响应于血管损伤的EC内HIF的需求和作用。具体目标1将研究如何HIF失活在胚胎发育的关键阶段的内皮细胞导致特定的血管生成缺陷。目的2解决了成人血管稳态和各种类型的血管反应（新血管生成，血管生成和动脉生成）对HIF的需求。最后，目标3将检查内皮细胞内HIF的内在要求，并检验HIF通过调节VEGF受体的表达在部分促进内皮细胞存活方面很重要的假设。本文提出的研究旨在扩大我们对缺氧在正常和病理环境中调节血管生成和稳态的机制的理解。 公共卫生相关性：缺陷性血管发育和/或维持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。通过使用体内遗传学方法，我们可以系统地研究由内皮HIF转录反应驱动的生物和分子血管过程。这项工作将提供一个分子框架，旨在了解在胚胎和成人中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。这种研究具有临床重要性，因为它可以为靶向血管生长过程的治疗剂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.