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      R229Q Polymorphism of NPHS2 Gene in Group of Iraqi Children with Steroid-Resistant Nephrotic Syndrome

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          Abstract

          Background. The polymorphism R229Q is one of the most commonly reported podocin sequence variations among steroid-resistant nephrotic syndromes (SRNS). Aim of the Study. We investigated the frequency and risk of this polymorphism among a group of Iraqi children with SRNS and steroid-sensitive nephrotic syndrome (SSNS). Patients and Methods. A prospective case control study which was conducted in Al-Imamein Al-Kadhimein Medical City, spanning the period from the 1st of April 2015 to 30th of November 2015. Study sample consisted of 54 children having NS, divided into 2 groups: patients group consisted of 27 children with SRNS, and control group involved 27 children with SSNS. Both were screened by real time polymerase chain reaction for R229Q in exon 5 of NPHS2 gene. Results. Molecular study showed R229Q polymorphism in 96.3% of SRNS and 100% of SSNS. There were no phenotypic or histologic characteristics of patients bearing homozygous R229Q polymorphism and the patients with heterozygous R229Q polymorphism. Conclusion. Polymorphism R229Q of NPHS2 gene is prevalent in Iraqi children with SRNS and SSNS. Further study needs to be done, for other exons and polymorphism of NPHS2 gene in those patients.

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          Most cited references 26

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          Patients with mutations in NPHS2 (podocin) do not respond to standard steroid treatment of nephrotic syndrome.

          Nephrotic syndrome (NS) represents the association of proteinuria, hypoalbuminemia, edema, and hyperlipidemia. Steroid-resistant NS (SRNS) is defined by primary resistance to standard steroid therapy. It remains one of the most intractable causes of ESRD in the first two decades of life. Mutations in the NPHS2 gene represent a frequent cause of SRNS, occurring in approximately 20 to 30% of sporadic cases of SRNS. On the basis of a very small number of patients, it was suspected that children with homozygous or compound heterozygous mutations in NPHS2 might exhibit primary steroid resistance and a decreased risk of FSGS recurrence after kidney transplantation. To test this hypothesis, NPHS2 mutational analysis was performed with direct sequencing for 190 patients with SRNS from 165 different families and, as a control sample, 124 patients with steroid-sensitive NS from 120 families. Homozygous or compound heterozygous mutations in NPHS2 were detected for 43 of 165 SRNS families (26%). Conversely, no homozygous or compound heterozygous mutations in NPHS2 were observed for the 120 steroid-sensitive NS families. Recurrence of FSGS in a renal transplant was noted for seven of 20 patients with SRNS (35%) without NPHS2 mutations, whereas it occurred for only two of 24 patients with SRNS (8%) with homozygous or compound heterozygous mutations in NPHS2. None of 29 patients with homozygous or compound heterozygous mutations in NPHS2 who were treated with cyclosporine A or cyclophosphamide demonstrated complete remission of NS. It was concluded that patients with SRNS with homozygous or compound heterozygous mutations in NPHS2 do not respond to standard steroid treatment and have a reduced risk for recurrence of FSGS in a renal transplant. Because these findings might affect the treatment plan for childhood SRNS, it might be advisable to perform mutational analysis of NPHS2, if the patient consents, in parallel with the start of the first course of standard steroid therapy.
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            Clinical and epidemiological assessment of steroid-resistant nephrotic syndrome associated with the NPHS2 R229Q variant.

            Mutations of NPHS2, encoding podocin, are the main cause of autosomal recessive steroid-resistant nephrotic syndrome (NS) presenting in childhood. Adult-onset steroid-resistant NS has been described in patients heterozygous for a pathogenic NPHS2 mutation together with the p.R229Q variant. To determine the frequency and the phenotype of patients carrying the p.R229Q variant, we sequenced the complete coding region of NPHS2 in 455 families (546 patients) non-responsive to immunosuppressive therapy or without relapse after transplantation. Among affected Europeans, the p.R229Q allele was significantly more frequent compared to control individuals. Thirty-six patients from 27 families (11 families from Europe and 14 from South America) were compound heterozygotes for the p.R229Q variant and one pathogenic mutation. These patients had significantly later onset of NS and end stage renal disease than patients with two pathogenic mutations. Among 119 patients diagnosed with NS presenting after 18 years of age, 18 patients were found to have one pathogenic mutation and p.R229Q, but none had two pathogenic mutations. Our study shows that compound heterozygosity for p.R229Q is associated with adult-onset steroid-resistant NS, mostly among patients of European and South American origin. Screening for the p.R229Q variant is recommended in these patients along with further NPHS2 mutation analysis in those carrying the variant.
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              NPHS2 R229Q functional variant is associated with microalbuminuria in the general population.

              Microalbuminuria is a risk factor for developing end-stage renal disease and cardiovascular events. Mutations in NPHS2 have been shown to cause autosomal-recessive nephrotic syndrome. Recently, a functional polymorphism of this gene (R229Q) was described and associated with a maturity-onset form of nephrotic syndrome. We have investigated whether the carrier status of this novel genetic variant is associated with microalbuminuria in individuals from the general population. Demographic, cardiovascular risk factors, and renal phenotypes in 1577 individuals from a cross-sectional-based study were collected following the general guidelines of the WHO-MONICA project (monitoring trends and determinants in cardiovascular diseases). Blood and urine samples were obtained. Microalbuminuria was determined using a semiquantitative protocol, and DNA was extracted from peripheral lymphocytes. A strong association was found between the 229Q allele and microalbuminuria (P= 0.008). The presence of the 229Q allele was still associated with a 2.77-fold increased risk of presenting microalbuminuria even after adjustment for age, ethnicity, hypertension, obesity, and diabetes in a multiple logistic regression model. In addition, a statistically significant interaction was identified between the presence of the 229Q allele and body mass index (BMI) (P= 0.01), suggesting an additive effect between the 229Q allele and other risk factors for microalbuminuria. These data have important implications for the understanding of microalbuminuria in the general population and may contribute to better ways of disease prediction and prevention.
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                Author and article information

                Journal
                Int J Nephrol
                Int J Nephrol
                IJN
                International Journal of Nephrology
                Hindawi
                2090-214X
                2090-2158
                2017
                26 April 2017
                : 2017
                Affiliations
                1College of Medicine, Al-Nahrain University, Baghdad, Iraq
                2Al-Imamein Al-Kadhimein Medical City, Baghdad, Iraq
                3College of Pharmacy, University of Al Qadisiyah, Diwaniyah, Iraq
                Author notes
                *Shatha Hussain Ali: shatha6ali@ 123456yahoo.com

                Academic Editor: Alessandro Amore

                Article
                10.1155/2017/1407506
                5424166
                Copyright © 2017 Shatha Hussain Ali et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Categories
                Research Article

                Nephrology

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