Jain Sudhir, Vinukonda Govindaiah, Fiering Steven N, Kumar Ashok
Department of Pathology, New York Medical College, Rm 455, Basic Science Bldg., Valhalla, NY 10595, USA.
Am J Physiol Regul Integr Comp Physiol. 2008 Dec;295(6):R1849-57. doi: 10.1152/ajpregu.90637.2008. Epub 2008 Oct 22.
The human angiotensinogen (hAGT) gene contains an A/G polymorphism at -217, and frequency of -217A allele is increased in African-American hypertensive patients. The hAGT gene has seven polymorphic sites in the 1.2-kb region of its promoter, and variant -217A almost always occurs with -532T, -793A, and -1074T, whereas variant -217G almost always occurs with -532C, -793G, and -1074G. Since allele -6A is the predominant allele in African-Americans, the AGT gene can be subdivided into two main haplotypes, -6A:-217A (AA) and -6A:-217G (AG). To understand the role of these haplotypes on hAGT gene expression and on blood pressure regulation in an in vivo situation, we have generated double transgenic mice containing human renin gene and either AA or AG haplotype of the hAGT gene using knock-in strategy at the hypoxanthine phosphoribosyltransferase locus. We show here that 1) hAGT mRNA level is increased in the liver by 60% and in the kidney by 40%; and 2) plasma AGT level is increased by approximately 40%, and plasma angiotensin II level is increased by approximately 50% in male double transgenic mice containing AA haplotype of the hAGT gene compared with the AG haplotype. In addition, systolic blood pressure is increased by 8 mmHg in transgenic mice containing the AA haplotype compared with the AG haplotype. This is the first report to show the effect of polymorphisms in the promoter of a human gene on its transcription in an in vivo situation that ultimately leads to an increase in blood pressure.
人类血管紧张素原（hAGT）基因在 -217 位点存在 A/G 多态性，在非裔美国高血压患者中，-217A 等位基因的频率增加。hAGT 基因在其启动子的 1.2 kb 区域有七个多态性位点，-217A 变体几乎总是与 -532T、-793A 和 -1074T 同时出现，而 -217G 变体几乎总是与 -532C、-793G 和 -1074G 同时出现。由于 -6A 等位基因是非裔美国人中的主要等位基因，AGT 基因可分为两种主要单倍型，即 -6A:-217A（AA）和 -6A:-217G（AG）。为了了解这些单倍型在体内情况下对 hAGT 基因表达和血压调节的作用，我们利用次黄嘌呤磷酸核糖基转移酶位点的敲入策略，构建了包含人类肾素基因以及 hAGT 基因的 AA 或 AG 单倍型的双转基因小鼠。我们在此表明：1）hAGT mRNA 水平在肝脏中增加了 60%，在肾脏中增加了 40%；2）与 AG 单倍型相比，含有 hAGT 基因 AA 单倍型的雄性双转基因小鼠的血浆 AGT 水平增加了约 40%，血浆血管紧张素 II 水平增加了约 50%。此外，与 AG 单倍型相比，含有 AA 单倍型的转基因小鼠的收缩压升高了 8 mmHg。这是第一份显示人类基因启动子多态性在体内情况下对其转录产生影响并最终导致血压升高的报告。
