Effect of Dietary Salt Excess on DNA Methylation and Transcriptional Regulation of Human Angiotensinogen Gene Expression.

BACKGROUND

Hypertension is caused by a combination of genetic and environmental factors. Angiotensinogen (AGT) is a component of renin-angiotensin-aldosterone system, which regulates blood pressure. 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 linked to hypertension. AGT polymorphisms result in two haplotypes, Hap-I a pro-hypertensive, whereas Hap-II is normotensive. Previous studies support the role of epigenetics in blood pressure regulation. In this study, we generated transgenic mice (TG) with hAGT containing Hap-I and Hap-II variants to investigate the effect of high salt diet (HSD) on epigenetics and transcriptional regulation.

METHODS

We treated Hap-I and Hap-II TG mice with 4% HSD and identified DNA methylation patterns. We measured hAGT mRNA and protein by qPCR and immunoblot, respectively. Chromatin immunoprecipitation assay and RNA sequencing were performed.

RESULTS

hAGT gene expression is increased by HSD in both Hap-I and Hap-II TG mice. In the liver and kidney, we observed significantly higher DNA demethylation (less CpG's) and stronger binding of transcription factors in the promoter of Hap-I TG mice as compared to Hap-II post HSD. RNA-Seq identified differentially expressed genes, novel target genes, canonical pathways, and upstream regulators associated with hypertension.

CONCLUSIONS

Our findings identified a novel high salt-sensitive risk haplotype, novel CpG sites and DNA methylation patterns, potential gene targets, and pathways implicated in hypertension. Combining epigenetic and transcriptional analysis allows for a more holistic understanding of the regulatory mechanisms that govern the hAGT gene.