Mapping of End Stage Renal Disease Genetic Susceptibility in African Americans by Admixture Linkage Disequilibrium

This study will identify which regions on the genes, and genes themselves, may account for an increased risk of end stage renal disease (ESRD), that is, near-total loss of kidney function, for people of African American descent. Researchers will use a technique called admixture linkage disequilibrium (MALD) to study genomes, genetic material, in about 2,500 participants from two existing studies and participants who will serve as controls. ESRD disproportionately affects African Americans, who constitute 29% of all ESRD patients in the Medicare ESRD program. The disease can result from a variety of diseases, with diabetes as the leading underlying cause (44% of cases) and hypertension as the second leading cause (26%). The proportion of ESRD cases caused by diabetes has increased dramatically.

Patients age 18 and older who are African American, who have ESRD, and who are participants of the FIND and CHOICE studies may be eligible for this study. FIND, or Family Investigation of Diabetes and Nephropathy, involves a multicenter study to identify susceptibility genes, that is, those with a risk, for diabetic and other forms of kidney disease. CHOICE, or Choices for Healthy Outcomes in Caring for ESRD patients is an ongoing study that identifies risk factors for cardiovascular outcomes in ESRD patients. The principle of mapping by MALD involves genetic variations that exist across populations. When mixing occurs between populations having different (heterogeneous) genes, the admixed offspring inherits chromosomes of distinct ancestry. However, over generations of mating, and recombination over several generations, originally large blocks of DNA from African ancestry have become part of smaller segments throughout the chromosome. The study will focus on risk alleles, that is, alternative forms of genes that carry a disease risk. Risk alleles are closely related to nearby ancestral gene markers found in a person.

Patients will undergo a collection of blood and urine for genetic testing. Researchers are conducting separate analyses in this study. Case-control analysis of ESRD will consist of 1,150 participants from FIND and 250 from CHOICE. There will also be 750 control participants from FIND. For the case-control analysis of diabetic ESRD, there will be about 750 participants from FIND, 125 from CHOICE, and 750 controls from FIND. Finally, there is the quantitative trait analysis, which looks at the phenotype-meaning visible characteristics produced by the interaction of a person's genetic makeup with the environment. That analysis will involve 350 patients with diabetic nephropathy but not ESRD and 750 controls from FIND.