A polymorphism in intron I of the human angiotensinogen gene (hAGT) affects binding by HNF3 and hAGT expression and increases blood pressure in mice

Abstract

Angiotensinogen (AGT) is the precursor of one of the most potent vasoconstrictors, peptide angiotensin II. Genome-wide association studies have shown that two A/G polymorphisms (rs2493134 and rs2004776), located at 507 and 1164 in intron I of the human AGT (hAGT) gene, are associated with hypertension. Polymorphisms of the AGT gene result in two main haplotypes. Hap-I contains the variants 217A, 6A, 507G, and 1164A and is pro-hypertensive, whereas Hap-II contains the variants 217G, 6G, 507A, and 1164G and does not affect blood pressure. The nucleotide sequence of intron I of the hAGT gene containing the 1164A variant has a stronger homology with the hepatocyte nuclear factor 3 (HNF3)– binding site than 1164G. Here we found that an oligonucleotide containing 1164A binds HNF3 more strongly than 1164G and that Hap-I–containing reporter gene constructs have increased basal and HNF3- and glucocorticoid-induced promoter activity in transiently transfected liver and kidney cells. Using a knock-in approach at the hypoxan-thine-guanine phosphoribosyltransferase locus, we generated a transgenic mouse model containing the human renin (hREN) gene and either Hap-I or Hap-II. We show that transgenic animals containing Hap-I have increased blood pressure compared with those containing Hap-II. Moreover, the transcription factors glucocorticoid receptor, CCAAT enhancer– binding protein , and HNF3 bound more strongly to chromatin obtained from the liver of transgenic animals containing Hap-I than to liver chromatin from Hap-II–containing animals. These findings suggest that, unlike Hap-II variants, Hap-I variants of the hAGT gene have increased transcription rates, resulting in elevated blood pressure.