Hypertension remains the most important risk factor for a wide variety of cardiovascular diseases accounting for approximately 54 percent of all strokes and 47 percent of all ischemic heart disease events globally. Despite the fact that we know there is a significant genetic component that determines the level of blood pressure (BP; estimates of heritability of BP range from 30-70%) we are far from understanding the myriad of genetic factors that account for BP variation in humans. One of the most significant challenges for understanding genetic control of BP is that the vast majority of BP-associated single nucleotide polymorphisms (SNPs) that have been identified in human genome wide association studies (GWAS) are located in noncoding regions of DNA. Many of the noncoding SNPs (ncSNPs) are in haplotype regions located thousands of base pairs away from any protein-coding gene making it nearly impossible to link the SNPs to a protein-coding gene or a physiological pathway that regulates BP based on sequence and our current knowledge of the mechanism of action for the SNPs. In this project we will focus on testing the specific hypothesis that many ncSNPs identified in GWAS impact the expression of BP relevant genes through epigenetic mechanisms. Epigenetics refers to stable changes in DNA function that are not directly due to changes in the sequence of DNA. Epigenomics refers to such changes when they occur across the entire genome. Therefore, we will use state- of-the-art epigenomic and epigenetic approaches to probe the epigenetic mechanisms by which individual ncSNPs impact the expression of genes associated with BP in human GWAS. Using nephron segments that we will micro-dissect from fresh human kidney and human resistance arterioles isolated from gluteal biopsies as well as related cell types that will be derived from human inducible pluripotent stem cells (iPSCs), we will create an epigenomic map of human BP related cells and tissues at an unprecedented tissue resolution. Using that map combined with our bioinformatic analysis of human GWAS SNP data and data from Project 1 in this PPG (effects of BP ncSNPs on gene expression) we will then test specific epigenetic mechanisms for individual SNPs. Finally, we will perform validation studies in which precision genome editing and targeted epigenetic analysis are utilized to determine if the hypothesized mechanisms are responsible for changes in gene expression in BP-relevant cell types. This project is highly collaborative with the other projects and cores in this Program Project Grant through the sharing of reagents (cells and tissues), transfer of data, and the intellectual environment of the investigators and their laboratories.
