Study of The Association of Mutations in The NPHS2 Gene and Nephrotic Syndrome in Children and Adults in Middle East

Overview

Nephrotic syndrome (NS) represents one of the most common diagnoses in pediatric and adult nephrology, with a prevalence of 16 per 100,000 children and 3 per 100,000 adults in Western countries. In most cases, the pathogenesis of NS remains elusive, and the clinical phenotype of patients does not allow discrimination among different causes. Thus, children with NS are usually treated with corticosteroids before a biopsy is taken, and approximately 80% of them respond to such a treatment. According to this observation, pediatric NS has been separated into two broad categories; Steroid-Sensitive Nephrotic Syndrome (SSNS) and Steroid-Resistant Nephrotic Syndrome (SRNS). In both these categories the biopsy result is usually Minimal Change Disease (MCD) while a few may show Focal and Segmental Glomerulosclerosis (FSGS). Although children affected by SSNS have good long-term prognosis, most patients with SRNS progress to End Stage Renal Disease (ESRD) within 2-10 years of diagnosis . In adults a biopsy diagnosis of FSGS is more common than in children and more patients will not respond to corticosteroids alone and will need additional immunosuppressant medication. About 40% will progress to ESRD within 10 years . Currently, at least 19 genes have been clearly identified with association to SRNS harboring \~300 independent mutations, conferring a considerable genetic heterogeneity to the disorder. Genetic testing is emerging as a useful diagnostic tool in SRNS as it has implications for clinical course, treatment response, risk for posttransplant proteinuria and prenatal diagnosis. An approach for genetic testing based on the current evidence seems cost-effective and may help in the best possible management of SRNS . The NPHS2 gene, is located on chromosome 1 and is also known as the Podocin gene. It encodes the podocin protein. Podocin is a 383-amino acid lipid-raft-associated protein localized at the slit diaphragm, where it is required for the structural organization and regulation of the glomerular filtration barrier. Its interaction with other slit diaphragm proteins eg. nephrin, NEPH1, CD2AP and TRPC6 is important in mechanosensation signaling, podocyte survival, cell polarity, and cytoskeletal organization . . It has been reported that variants in the NPHS2 gene are associated with NS . The commonly studied rs61747728 NPHS2 gene polymorphism also known as p.R229Q has been reported to be associated with NS and SRNS . However others have failed to report an association , which might be due to population differences. The rs61747728 is a non-synonymous variant found on exon 5 which is suggested to be involved in in altering the functional properties of podocin in vitro and possibly in vivo . The investigators will therefore investigate the frequency of the p.R229Q variant in Middle East patients with NS. Genetic analysis will have important implications in several aspects:- 1. Understanding the biology of the disease in this part of the world. 2. Counselling patients about their clinical course and what medication they will respond to. 3. Counselling patients about the possibility of a kidney transplant sooner in their disease course