Over 400,000 Americans have end-stage renal disease (ESRD) requiring dialysis or kidney transplant for survival. ESRD in the US population doubled in the last decade and this increase is driven by diabetes and hypertension. ESRD is associated with very high rates of mortality, most frequently from cardiovascular disease (CVD), and the heightened risk of CVD in individuals with chronic renal injury means that they are much more likely to die of CVD than to progress to ESRD. There is great variation in risk for ESRD among individuals who have hypertension and/or diabetes. The major determinant of this variation in risk is genetic susceptibility that serves to enhance the capacity of hypertension and diabetes to generate renal injury. The proposed studies focus on an animal model of renal injury with concurrent hypertension, insulin resistance and dyslipidemia, the spontaneously hypertensive rat (SHR). This model recapitulates the role of genetic susceptibility to renal injury in hypertensive and diabetic patients: the SHR-A3 line acquires hypertensive renal injury, while other hypertensive SHR lines resist it. These contrasting SHR lines offer a valuable means to identify the mechanism of and the genes contributing to susceptibility to renal injury. The proposed studies are made possible by our recent progress in defining a set of high density, single nucleotide polymorphism (SNP) markers in our injury-prone (SHR-A3) and resistant (SHRB2) lines that allow high resolution genetic mapping of loci controlling susceptibility to renal injury. We propose here to use these markers to map an intercross of these parental lines that will identify injury susceptibility loci. The conclusions of our mapping study will be tested and verified by breeding reciprocal congenic strains that fix injury resistance and susceptibility alleles in the injury-prone SHR-A3 and the injury-resistant SHR-B2 lines. Finally, we have uncovered the role of renal redox stress in the generation of renal injury in SHR-A3 and identified a transcriptional program that leads to this redox stress. This provides an opportunity to refine our genetic mapping studies down to the level of specific genes within the mapped loci. Genes that are functionally correlated to the transcriptional pathway of renal redox stress that we have elucidated in SHR-A3 will be targeted for selective resequencing to identify specific gene variants that drive the renal injury pathway.
Kidney injury caused by diabetes and high blood pressure requires that more than 400,000 Americans be treated by kidney dialysis in order to survive. Heredity plays a major role in risk of kidney injury. Among diabetic and high blood pressure patients, the largest risk of progressive kidney disease is the occurrence of this disease in a relative. In the proposed studies we will use a rat model of this syndrome to genetically map chromosomal regions harboring genes that create risk of kidney injury. By uncovering the genes that cause this injury in rats and how this injury is created by these genes we will open up valuable new opportunities to understand the disease in people and to envision and test new treatments.
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