Dynamic Regulation of Erythropoietin Gene Expression in Mammals

哺乳动物促红细胞生成素基因表达的动态调控

• 批准号: 7691086
• 负责人: Joseph Anthony Garcia
• 金额: --
• 依托单位: VA NORTH TEXAS HEALTH CARE SYSTEM
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-04-01 至 2012-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7691086
• 关键词: Ablation; Anemia; Attenuated; Binding; Biochemical; Biological; Biological Assay; Bolus Infusion; Brain; Cell Culture Techniques; Cell Line; Cells; Cessation of life; Chronic; Co-Immunoprecipitations; Complex; DNA; Enhancers; Erythrocytes; Erythropoietin; Gene Expression; Genes; Genetic Enhancer Element; Goals; Growth; HIF1A gene; Healthcare; Homeostasis; Hour; Hypertension; Hypoxia; Hypoxia-Responsive Elements; Individual; Kidney; Kidney Diseases; Knockout Mice; Liver; Mammals; Mediating; Messenger RNA; Modeling; Molecular; Molecular Target; Mus; NuRD complex; Oxygen; Pathway interactions; Patients; Pharmacotherapy; Plant Roots; Production; Proteins; Regulation; Repression; Research Personnel; Retina; Reverse Transcriptase Polymerase Chain Reaction; Role; Signal Transduction; Site; Stress; Time; Tissues; Transfection; Veterans; abstracting; bHLH-PAS factor HLF; chromatin immunoprecipitation; cytokine; hepatoma cell; hybrid protein; hypoxia inducible factor 1; in vivo; insight; member; mouse model; novel; overexpression; public health relevance; response; small hairpin RNA; transcription factor

DESCRIPTION (provided by applicant): PROJECT SUMMARY/ABSTRACT Impaired erythropoietin (epo) production is the root cause of anemia in a majority of chronic anemia patients. Over the past century, investigators discovered that the potent inducer of red blood cell mass in response to anemia or systemic hypoxia is circulating epo, a pro-erythrogenic cytokine produced by the kidney. Approximately one-third of chronic anemia patients have normal kidneys, but inappropriately low epo levels. Why is epo expression blunted in these patients? The answer to this question requires first understanding how epo gene expression is regulated in normal individuals. Studies of epo regulation over the past decade have focused on hypoxia signaling. Using hepatoma cell lines producing epo in an oxygen-dependent manner, investigators defined the hypoxia- responsive enhancer region of the epo gene. This in turn led to identification of a cis-acting DNA enhancer element, the Hypoxia Responsive Element (HRE), in the epo enhancer region followed by purification of an HRE-binding oxygen-sensitive transcription factor, Hypoxia Inducible Factor 1 alpha (HIF-11). Investigators initially assumed that HIF-11 regulates endogenous epo gene expression. However, mouse model studies reveal that the second and related HIF member, HIF-21, is critical for in vivo epo gene expression. Our long-term goal is to define the molecular mechanisms regulating mammalian epo expression. Epo synthesis normally increases rapidly with tissue hypoxia, and then returns to baseline within hours. While an essential role of HIF-21 in epo regulation is now recognized, the factors responsible for temporal epo gene expression in vivo, or for abnormal repression of epo gene expression in anemia patients, remain poorly understood. In unpublished Preliminary Studies, we demonstrate novel regulation of epo enhancer function by Early Growth Response (Egr) members, stress-responsive transcription factors whose activity is also altered by hypoxia. We further demonstrate that factors known to repress Egr signaling also repress epo enhancer activity in a HIF-21 dependent manner. We hypothesize that hypoxia initially triggers Egr and HIF-2 activation, leading to synergistic activation of epo gene expression. With continued hypoxia exposure, we propose Egr repressive factors are induced that attenuate epo gene expression. In this proposal, we will define molecular and biochemical mechanisms whereby Egr/HIF-2 signaling regulates epo enhancer activity, and we will define the biological role of Egr/HIF-2 signaling in epo regulation using cell culture and mouse knockout models. Deciphering how Egr/HIF-2 signaling regulates epo enhancer activity will provide mechanistic insights into normal epo regulation and will identify novel molecular targets for modulation of endogenous epo gene expression in chronic anemia patients. PUBLIC HEALTH RELEVANCE: PROJECT NARRATIVE The Potential Impact on Veterans Health Care is identifying specific molecular pathways that can be targeted by novel drug therapies, thereby restoring normal erythropoietin production in a large segment of our veteran patients with chronic anemia.

描述（由申请人提供）： 项目摘要/抽象性促红细胞生成素（EPO）的产生是大多数慢性贫血患者贫血的根本原因。在过去的一个世纪中，调查人员发现，对贫血或全身性缺氧的有效诱导剂是循环的EPO，这是肾脏产生的促胸细胞因子。大约三分之一的慢性贫血患者患有正常的肾脏，但EPO水平不当。为什么这些患者的EPO表达钝了？这个问题的答案需要首先了解正常个体如何调节EPO基因表达。 过去十年中，EPO调节的研究集中在缺氧信号传导上。研究人员使用肝癌的肝癌细胞系以氧气依赖性方式定义了EPO基因的缺氧反应性增强子区域。这反过来又导致了在EPO增强子区域中鉴定出顺式作用DNA增强子元件，缺氧反应元件（HRE），然后纯化HRE结合氧敏感的转录因子，缺氧诱导因子1αα（HIF-11）。研究人员最初假设HIF-11调节内源性EPO基因表达。 然而，小鼠模型研究表明，第二和相关的HIF成员HIF-21对于体内EPO基因表达至关重要。 我们的长期目标是定义调节哺乳动物EPO表达的分子机制。 EPO合成通常会随组织缺氧而迅速增加，然后在数小时内返回基线。尽管现在已经确认了HIF-21在EPO调控中的重要作用，但导致体内时间EPO基因表达的因素或贫血患者中EPO基因表达异常的抑制作用仍然很少了解。在未发表的初步研究中，我们通过早期生长反应（EGR）成员，应力反应性转录因子对EPO增强子功能进行了新的调节，其活性也会因缺氧而改变。我们进一步证明，已知以抑制EGR信号传导的因素也以HIF-21依赖性方式抑制EPO增强子活性。 我们假设缺氧最初会触发EGR和HIF-2激活，从而导致EPO基因表达的协同激活。随着缺氧的持续暴露，我们提出诱导EGR抑制因素，以减轻EPO基因的表达。在此提案中，我们将定义分子和生化机制，通过该机制EGR/HIF-2信号传导调节EPO增强剂的活性，我们将使用细胞培养和小鼠敲除模型来定义EGR/HIF-2信号在EPO调控中的生物学作用。解释EGR/HIF-2信号传导如何调节EPO增强子活性将为正常的EPO调控提供机理见解，并将确定新型分子靶标，以调节慢性贫血患者内源性EPO基因表达。 公共卫生相关性： 项目叙述对退伍军人医疗保健的潜在影响是确定可以通过新型药物疗法靶向的特定分子途径，从而在我们的大部分慢性贫血患者中恢复正常的红细胞生成素的产生。