Genetic Dissection of Blood Pressure in the Dahl SS Rat Using Sequence Data.

摘要

Hypertension is a complex disease with contributions from many genes, environmental factors as well as gene-gene and gene-environment interactions. Many mechanisms are known to play a role in blood pressure regulation including renal water and sodium handling, inflammation, vascular reactivity, sympathetic activity, and immune response. Despite this, the cause of hypertension is unknown in the majority of patients. The polygenic nature of hypertension makes the identification of genetic factors in humans difficult. The use of inbred animal models eliminates environmental variables and reduces genetic complexity aiding in the identification of causal variants and genes.;The Dahl salt-sensitive (SS) rat strain is a commonly used genetic model of elevated blood pressure, salt-sensitivity and renal injury. The SS strain was selectively bred for increased blood pressure when fed a high salt diet from outbred Sprague Dawley rats. Concurrently the Dahl salt-resistant (SR) strain was selectively bred for extreme resistance to salt induced elevation of blood pressure. The Brown Norway (BN) strain is also resistant to increases in blood pressure when fed a high salt diet. The BN strain was derived through the inbreeding of wild rats and is therefore phylogenetically distant from the SS and SR strains. The differences in phenotype and genotype make the inbred SS, SR and BN strains ideal models for the identification of sequence variants and genes contributing to salt-sensitive hypertension.;This thesis examines the hypothesis that the analysis of genome-wide sequence data can identify genetic variants affecting the function or abundance of genes in similar pathways that contribute to the elevated blood pressure in the SS rat.;To identify genes contributing to increased blood pressure in the SS rat, whole genome sequencing and RNA-Sequencing experiments were performed in the SS, SR and BN strains. Genomic DNA from each strain was sequenced to identify genetic variation. The sequence variants most likely to contribute to blood pressure regulation in the SS strain were prioritized based on predicted consequence to protein function, comparison between hypertensive and normotensive strains and known gene function related to blood pressure. Additionally, we sequenced the mRNA from five tissues known to play a role in blood pressure regulation; adrenal gland, brain, heart, kidney and mesenteric vessels. Differences in gene expression between strains were identified and prioritized to identify differentially expressed genes with the potential to regulate blood pressure in the SS strain.;We found compelling evidence for multiple candidate genes involved in several pathways having the potential to contribute to blood pressure regulation in the SS strain and possibly human patients. Two genes known to play a role in increased blood pressure and renal injury in the rat, Nox4 and C6, were nominated in our analysis. Additionally, genes known to affect salt response (Sik1, Guca2a and Guca2b) and formation of the proximal tubule, Notch2, were identified. Several genes with known roles in oxidative stress and immune response (Nlrp6, Ccl24, Nox4, Prcp, and Cfh) and the potential to mediate renal and vascular functions were also nominated by our analysis pipeline.;This thesis has identified known and novel candidate genes for the regulation of blood pressure in the SS rat. Future work is needed to validate and characterize candidate genes and investigate a potential role in human salt-sensitive hypertension. Identification of known mediators of blood pressure suggests that our prioritization schemes for variant containing and differentially expressed genes could be adapted for the genetic dissection of regions of interest of any size to nominate candidate genes and variants for a variety of phenotypes.