Genetic Markers for Focal Segmental Glomerulosclerosis

Focal Segmental Glomerulosclerosis, HIV-Associated Focal Segmental Glomerulosclerosis

Collapsing Glomerulopathy, Renal Diseases, HIV-associated nephropathy, Natural History

Glomerulonephritis is a disease which affect the kidneys. Occasionally these diseases can progress to a loss of kidney function in some patients. Glomerulosclerosis or focal segmental glomerulosclerosis (FSGS) is one form of glomerulonephritis. The cause of FSGS is unknown and often occurs on its own (idiopathic), or it can be associated with HIV (Human Immunodeficiency Virus). FSGS occurs more commonly among black patients than Caucasian or Hispanic patients. Researchers believe that environmental factors may interact with genetic mutations to cause FSGS, at least in some patients. This study will attempt to identify genetic factors associated with the development of FSGS. The study population will be made up of 600 total subjects divided into 3 groups. Group one will be 200 African-Americans with FSGS. Group two will be 200 African-Americans with HIV but without FSGS. Group three will be 200 non-African-Americans with FSGS. Study participation requires that researchers obtain 20 ml (2 tubes of blood). The genetic material (DNA) will be prepared from the white blood cells and analyzed. The results of each group will be compared with the results from the other groups to determine if one or more genes predisposes to FSGS. In the long run, studies that demonstrate a genetic basis for FSGS may help us identify patients earlier and may lead to improved therapies.

Focal segmental glomerulosclerosis (FSGS) and a related condition, collapsing glomerulopathy, are chronic renal diseases affecting the glomerular podocytes. Currently, over thirteen genetic mutations are associated with FSGS. We are interested in expanding our understanding of these and other genes that may cause FSGS and collapsing glomerulopathy. We will study individuals with affected family members. We will also study sporadic cases; the rationale for studying this population is that FSGS and collapsing glomerulopathy are significantly more common among individuals of African descent. The latter observation suggests that particular FSGS-susceptibility alleles may be more common among African Americans. In the present study, we are addressing the hypothesis that genetic variation contributes to the pathogenesis of idiopathic FSGS and collapsing glomerulopathy, both idiopathic and HIV-associated variants. We are studying the following groups: 1) African-Americans with idiopathic or HIV-associated collapsing glomerulopathy. We will exclude post-adaptive FSGS, associated with glomerular hyperfiltration, and medication associated FSGS. 2) Other patients with idiopathic FSGS. 3) African Americans with HIV and without kidney disease (hyper-normal controls). 4) African descent controls (controls). 5) Healthy European and Asian descent controls (controls). 6) Relatives of patients with familial FSGS. 7) Kidney donors. 8) Tamils. We are taking four methodologic approaches. First, we are examining known FSGS risk genes or candidate genes, looking for disease-causing mutations and for disease-susceptibility haplotypes. Second, we have undertaken a genome scan, in the African descent population. We may also undertake a whole genome scan in European and Asian descent. Evidence of linkage disequilibrium among these markers will be sought between patients with and without FSGS. Third, when we identify families with multiple affected individuals and which lack known genetic mutations affecting FSGS genes, we will pursue positional cloning. Fourth, we will generate iPSC from peripheral blood from individuals with kidney disease (with a particular focus on those with particular genetic variants associated with glomerular disease) and from healthy volunteers. We will generate podocytes, to understand mechanisms of FSGS, and possibly macrophages, to understand reverse cholesterol transport (with relevance to nephrotic syndrome and more broadly cardiovascular disease).

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