Characterization of NPHS2 gene polymorphisms associated to steroid resistance nephrotic syndrome in Indian children

Nephrotic syndrome (NS) is the common glomerular disease in children. These children are treated with steroids, depending upon their behavior. They are either steroid sensitive (SSNS) or steroid resistant (SRNS). NPHS2 gene mutants are linked to the risk of autosomal recessive SRNS and in some cases to SSNS. The present study has been performed to screen single nucleotide polymorphisms (SNPs) of the NPHS2 gene in a group of 90 Indian children suffering with NS (30 SSNS, 30 SRNS and 30 Controls) by PCR method followed by direct exon sequencing. Effect of SNPs on fold expression changes at transcript level of podocin was checked using quantitative real time PCR (qRT-PCR). SNPs identified through sequencing helps to carry out in-silico analysis. Overall 17 SNPs were identified in NPHS2 gene where 6 were found novel. Three missense SNPs p.R299Q, p.P20L and p.G35D were also identified in this population where SNP, p.G35D was found novel. In addition to sequencing analysis, results of in silico analysis shows that a mutant with these three missense SNPs has least ligand binding efficiency compared to native model. Moreover the significant observation of this study included two intronic SNPs c.451 + 23C > T and c.451 + 58A > T present in SRNS group of patients. These SNPs has shown high level of clinical significance within genomic and allelic frequency along with haplotypes and linkage disequilibrium count. The qRT-PCR analysis shows, down expression of podocin protein at transcript level in SRNS patients compared to SSNS patients. All these results support the fact that SNPs present in this population could affect the protein structural stability. Thus it is concluded that the polymorphisms predicted in this study might be disease causing in the NPHS2 gene and may have influence on the therapeutic response of NS patients.