Transcriptional Regulation of Angiotensinogen Gene

血管紧张素原基因的转录调控

• 批准号: 7905982
• 负责人: ASHOK KUMAR
• 金额: $ 39.75万
• 依托单位: NEW YORK MEDICAL COLLEGE
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7905982
• 关键词: Acute; Acute-Phase Proteins; Adult; Affect; African American; Aging; Alleles; American; Angiotensin II; Angiotensinogen; Binding; Blood Pressure; CCAAT-Enhancer-Binding Proteins; Caucasians; Caucasoid Race; Development; Dexamethasone; Essential Hypertension; Family; Figs - dietary; Frequencies; Gene Expression; Gene Frequency; Genes; Genetic Polymorphism; Genetic Transcription; Genetic Translation; Glucocorticoids; Haplotypes; Heart failure; Hepatocyte; Human; Hypertension; Incidence; Inflammation; Interleukin-6; Japanese Population; Kidney Failure; Knock-in Mouse; Left; Liver; Messenger RNA; Molecular; Myocardial Infarction; Nucleosides; Patients; Phase; Plasma; Play; Population; Prevalence; Promoter Regions; Proteins; Recombinants; Renin; Renin-Angiotensin System; Reporter; Risk Factors; Role; Site; Stroke; Tissues; Transcriptional Regulation; Transfection; Transgenic Mice; Variant; Vascular Diseases; blood pressure regulation; in vivo; male; promoter; public health relevance; transcription factor; vasoconstriction

DESCRIPTION (provided by applicant): Hypertension is a serious risk factor for myocardial infarction, heart failure, vascular disease, stroke, and renal failure. The renin-angiotensin system plays an important role in the regulation of blood pressure. Previous studies have suggested that: (a) angiotensinogen (AGT) gene locus is associated with human essential hypertension, (b) variant -6A of the AGT gene is associated with hypertension in Caucasian and Japanese subjects and (c) over-expression of the AGT gene increases blood pressure in transgenic mice. We have found an A/G polymorphism at -217 in the human AGT gene promoter and have shown that frequency of allele A at -217 is significantly increased in African-American hypertensive patients. AGT gene is primarily expressed in the liver and we have shown that reporter constructs containing AGT gene promoter with nucleoside A at -217 have increased basal and IL-6 induced promoter activity on transient transfection in human liver cells. Although hAGT gene has seven polymorphic sites in 1.2Kb region of its promoter, variants -217A almost always occurs with -532T, -793A, and -1074T and variants -217G, -532C, -793G, and -1074G always occur together forming two haplotypes. Since allele - 6A is the predominant allele (frequency 0.85) in African-Americans, AGT gene can be subdivided into four haplotypes -6A:-217A (AA); -6A:-217G (AG); -6G:-217A (GA) and -6G:-217G (GG). However, haplotypes GA and GG are very rare leaving AA and AG as two prominent haplotypes. We have shown that: (a) frequency of AA haplotype is increased in hypertensive patients as compared to the AG haplotype and (b) reporter constructs containing AA haplotype have increased basal as well as IL-6 induced promoter activity as compared to AG haplotype. Since inflammation plays an important role in hypertension, our hypothesis is that increased transcription of AA haplotype of the AGT gene plays an important role in the development of hypertension. In order to prove this hypothesis, we have generated transgenic mice containing human renin gene and either AA or AG haplotype of the hAGT gene using knock-in strategy at the HPRT locus. We have shown that AGT mRNA and protein level is increased in double transgenic mice containing AA haplotype of the AGT gene as compared to the AG haplotype. We have also shown that double transgenic mice containing AA haplotype of the hAGT gene and hRen gene have increased blood pressure as compared to transgenic mice containing AG haplotype of the hAGT gene and hRen gene. We will now study the role of these haplotypes on blood pressure regulation in an in vivo situation in transgenic mice containing either AA or AG haplotype of the hAGT gene and hRen gene but devoid of mAGT gene. PUBLIC HEALTH RELEVANCE: Hypertension is a serious risk factor for myocardial infarction, heart failure, vascular disease, stroke, and renal failure. It is estimated that hypertension affects 50 million Americans with a prevalence rate of 25-30% in the adult Caucasian population. The incidence of hypertension and complications due to hypertension are even greater in the African American population. Our studies will help us understand molecular mechanism involved in hypertension.

描述（由申请人提供）：高血压是心肌梗塞，心力衰竭，血管疾病，中风和肾衰竭的严重危险因素。肾素 - 血管紧张素系统在血压调节中起重要作用。先前的研究表明：（a）血管紧张素原（AGT）基因座与人类本质高血压有关，（b）AGT基因的变异-6a与高加索和日本受试者的高血压有关，并且（c）AGT基因的过表达会增加转基因小鼠的血压。我们在人类AGT基因启动子中发现了-217的A/G多态性，并且表明非裔美国人高血压患者的AT -217等位基因A的频率显着增加。 AGT基因主要在肝脏中表达，我们已经表明，含有核苷A AT -217的含有AGT基因启动子的报告基因构建体具有增加的基础和IL -6诱导启动子在人肝细胞中瞬时转染中的启动子活性。尽管HAGT基因在其启动子的1.2kb区域中具有七个多态性位点，但变体-217a几乎总是以-532T，-793A和-793A和-1074T和-1074T和变体-217G，-532C，-532C，-793G，-793G和-1074G始终出现 - 始终出现两种效果。由于等位基因-6a是非裔美国人的主要等位基因（频率为0.85），因此可以将AGT基因细分为四个单倍型-6a：-217a（-217a（AA））; -6A：-217G（AG）; -6G：-217A（GA）和-6G：-217G（GG）。但是，单倍型GA和GG非常罕见，将AA和AG作为两种突出的单倍型。我们已经表明：（a）与AG单倍型相比，高血压患者的AA单倍型的频率增加，并且（b）含有AA单倍型的报告基因构建体的基础增加，而IL-6诱导的启动子与AG单倍型相比。由于炎症在高血压中起着重要作用，因此我们的假设是，AGT基因的AA单倍型的转录在高血压发展中起着重要作用。为了证明这一假设，我们使用HPRT基因座的敲入策略生成了含有人肾脏基因的转基因小鼠以及AA或Ag单倍型。我们已经表明，与Ag单倍型相比，在含有AGT基因的AA单倍型的双转基因小鼠中，AGT mRNA和蛋白质水平升高。我们还表明，与含有HAGT基因和HREN基因的Ag单倍型相比，HAGT基因和HREN基因的双型单倍型的双转基因小鼠具有升高。现在，我们将研究这些单倍型对血压调节的作用在含有hagt基因和HREN基因的AA或Ag单倍型但没有MAGT基因的转基因小鼠中的体内情况中的作用。公共卫生相关性：高血压是心肌梗塞，心力衰竭，血管疾病，中风和肾衰竭的严重危险因素。据估计，成年高加索人口的高血压影响5000万美国人，患病率为25-30％。在非洲裔美国人口中，高血压和并发症的发生率更大。我们的研究将帮助我们了解与高血压有关的分子机制。