Transcriptional Regulation of Angiotensinogen Gene

血管紧张素原基因的转录调控

• 批准号: 8476249
• 负责人: ASHOK KUMAR
• 金额: $ 35.3万
• 依托单位: UNIVERSITY OF TOLEDO HEALTH SCI CAMPUS
• 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 2015-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8476249
• 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; Frequencies; Gene Expression; Gene Frequency; Genes; Genetic Polymorphism; Genetic Transcription; Genetic Translation; Glucocorticoids; Haplotypes; Health; 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; 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.

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发挥着重要作用。先前的研究表明：(a) 血管紧张素原 (AGT) 基因位点与人类原发性高血压相关，(b) AGT 基因的变体 -6A 与白种人和日本受试者的高血压相关，以及 (c) 血管紧张素原基因的过度表达AGT 基因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 处的 A/G 多态性，并表明 -217 处等位基因 A 的频率在非洲裔美国高血压患者中显着增加。 AGT 基因主要在肝脏中表达，我们已经表明，含有核苷 A 在 -217 的 AGT 基因启动子的报告构建体在人肝细胞中瞬时转染时增加了基础和 IL-6 诱导的启动子活性。虽然hAGT基因在其启动子的1.2Kb区域有7个多态性位点，但变体-217A几乎总是与-532T、-793A和-1074T一起出现，变体-217G、-532C、-793G和-1074G总是一起出现，形成两个单倍型。由于等位基因-6A是非裔美国人中的优势等位基因（频率0.85），AGT基因可细分为四种单倍型-6A：-217A（AA）； -6A：-217G（AG）； -6G：-217A（GA）和-6G：-217G（GG）。然而，单倍型 GA 和 GG 非常罕见，因此 AA 和 AG 成为两个突出的单倍型。我们已经表明：（a）与 AG 单倍型相比，高血压患者中 AA 单倍型的频率增加；（b）与 AG 单倍型相比，含有 AA 单倍型的报告构建体具有增加的基础以及 IL-6 诱导的启动子活性。由于炎症在高血压中起着重要作用，我们的假设是 AGT 基因 AA 单倍型转录的增加在高血压的发展中起着重要作用。为了证明这一假设，我们利用 HPRT 基因座的敲入策略，产生了含有人肾素基因和 hAGT 基因 AA 或 AG 单倍型的转基因小鼠。我们已经表明，与AG单倍型相比，含有AGT基因的AA单倍型的双转基因小鼠中AGT mRNA和蛋白质水平增加。我们还表明，与含有hAGT基因和hRen基因的AG单倍型的转基因小鼠相比，含有hAGT基因和hRen基因的AA单倍型的双转基因小鼠血压升高。我们现在将在含有 hAGT 基因和 hRen 基因的 AA 或 AG 单倍型但不含 mAGT 基因的转基因小鼠体内研究这些单倍型对血压调节的作用。