Mutational landscape of TRPC6, WT1, LMX1B, APOL1, PTPRO, PMM2, LAMB2 and WT1 genes associated with Steroid resistant nephrotic syndrome.

BACKGROUND: Nephrotic syndrome appears as a group of symptoms like proteinuria, edema and hyperlipidemia. Identification of monogenic forms revealed the physiology and pathogenesis of the SRNS. METHODS AND RESULTS: We performed Illumina panel sequencing of seven genes in 90 Indian patients to determine the role of these genetic mutations in nephrotic syndrome prognosis. Samtool was used for variants calling, and SnpEff and Snpsift did variants annotation. Clinical significance and variant classification were performed by the ClinVar database. In SSNS and SRNS patients, we found 0.78% pathogenic and 3.41% likely pathogenic mutations. Pathogenic mutations were found in LAMB2, LMX1B and WT1 genes, while likely pathogenic mutations were found in (6/13) LAMB2, (2/13) LMX1B, (2/13) TRPC6, (2/13) PTPRO and (1/13) PMM2 genes. Approximately 46% likely pathogenic mutations were contributed to the LAMB2 gene in SSNS and SRNS patients. We also detect 30 VUS (variants of uncertain significance), which were found (17/30) pathogenic and (13/30) likely pathogenic by different prediction tools. CONCLUSIONS: Multigene panels were used for genetic screening of heterogeneous disorders like nephrotic syndrome in the Indian population. We found pathogenic, likely pathogenic and certain VUS, which were responsible for the pathogenesis of the disease. Therefore, mutational analysis of SSNS and SRNS is necessary to avoid adverse effects of corticosteroids, modify the intensity of immunosuppressing agents, and prevent the disease's progression.

Exploring the deleterious SNPs in XRCC4 gene using computational approach and studying their association with breast cancer in the population of West India.

Non-homologous end joining (NHEJ) pathway has pivotal role in repair of double-strand DNA breaks that may lead to carcinogenesis. XRCC4 is one of the essential proteins of this pathway and single-nucleotide polymorphisms (SNPs) of this gene are reported to be associated with cancer risks. In our study, we first used computational approaches to predict the damaging variants of XRCC4 gene. Tools predicted rs79561451 (S110P) nsSNP as the most deleterious SNP. Along with this SNP, we analysed other two SNPs (rs3734091 and rs6869366) to study their association with breast cancer in population of West India. Variant rs3734091 was found to be significantly associated with breast cancer while rs6869366 variant did not show any association. These SNPs may influence the susceptibility of individuals to breast cancer in this population.

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.

A computational approach to determine susceptibility to cancer by evaluating the deleterious effect of nsSNP in XRCC1 gene on binding interaction of XRCC1 protein with ligase III.

Several reports suggest that non-synonymous single nucleotide polymorphisms affect the function of XRCC1 which impairs DNA repair capacity and thus increases risk to diseases like cancer. In our study, we predicted the most damaging nsSNPs using a computational approach and analysed its functional impact on the XRCC1 and LIG3 interaction. SNP rs2307166 was predicted to be deleterious using eight software programs: SIFT, PolyPhen, PANTHER, PhD-SNP, nsSNPAnalyzer, SNPS&GO, SNAP and I-Mutant. Protein structural analysis was performed using Swiss PDB viewer, and PyMOL. Xenoview was used for molecular dynamic simulation and energy minimisation. Finally, PatchDock and FireDock were used to analyse the interactions of XRCC1 and LIG3. By comparing the results we found that the mutant protein has less binding energy and the interacting amino acids than native protein. In silico analysis predicted rs2307166 to be more damaging than three other extensively studied SNPs. Identification of this SNP will help in determining the susceptibility of the individual to cancer, their prognosis and further treatment.

In silico analysis of functional nsSNPs in human TRPC6 gene associated with steroid resistant nephrotic syndrome.

The aim of the present study is to identify functional non-synonymous SNPs of TRPC6 gene using various in silico approaches. These SNPs are believed to have a direct impact on protein stability through conformation changes. Transient receptor potential cation channel-6 (TRPC6) is one of the proteins that plays a key role causing focal segmental glomerulosclerosis (FSGS) associated with the steroid-resistant nephritic syndrome (SRNS). Data of TRPC6 was collected from dbSNP and further used to investigate a damaging effect using SIFT, PolyPhen, PROVEAN, and PANTHER. The comparative analysis predicted that two functional SNPs "rs35857503 at position N157T and rs36111323 at position A404V" showed a damaging effect (score of 0.096-1.00).We modeled the 3D structure of TRPC6 using a SWISS-MODEL workspace and validated it via PROCHECK to get a Ramachandran plot (83.0% residues in the most favored region, 12.7% in additionally allowed regions, 2.3% in a generously allowed region and 2.0% were in a disallowed region). QMEAN (0.311) and MUSTER (10.06) scores were under acceptable limits. Putative functional SNPs that may possibly undergo post-translation modifications were also identified in TRPC6 protein. It was found that mutation at N157T can lead to alteration in glycation whereas mutation at A404V was present at a ligand binding site. Additionally, I-Mutant showed a decrease in stability for these nsSNPs upon mutation, thus suggesting that the N157T and A404V variants of TRPC6 could directly or indirectly destabilize the amino acid interactions causing functional deviations of protein to some extent.

Vascular endothelial growth factor insertion/deletion gene polymorphism in West Indian patients of type 2 diabetes and diabetic nephropathy.

Diabetic nephropathy (DN) is a major cause of morbidity and mortality in diabetes. Vascular endothelial growth factor (VEGF) is a potent multi-functional cytokine which plays a key role in the pathogenesis of DN. In this study, we evaluated the possible association of the VEGF gene (I/D) polymorphisms with DN in type 2 diabetes patients in West Indian population. Genotyping (I/D) of the VEGF gene polymorphism was done by the polymerase chain reaction. A total of 103 patients with type 2 diabetes, 102 patients with DN, 108 patients with non-diabetic nephropathy and 143 healthy controls were genotyped. The frequency of VEGF genotype distribution and biochemical parameters like creatinine and HbA1c were compared in diabetic, diabetic nephropathy, non diabetic nephropathy and control groups. We found significant difference in creatinine level in DN and NDN groups on comparison with control group. Our study suggests that I/D polymorphism in the promoter region of the VEGF gene is not associated with DN in type 2 diabetes patients, but might have a role in development of non-diabetic nephropathy.

Oxidative stress and its association with TNF-α-308 G/C and IL-1α-889 C/T gene polymorphisms in patients with diabetes and diabetic nephropathy.

Diabetic nephropathy is one of the major complications of type 2 diabetes and it is currently the leading cause of end-stage renal disease. The stimulus for the increase in inflammation in diabetes is still under investigation; however, reactive oxygen species might be a primary source. This study was conducted in four groups in West Indian population: control (235), type 2 diabetes (DM) (214), nephropathy with diabetes (DN) (188) and nephropathy without diabetes (NDN) (196). Oxidative stress markers such as malondialdehyde (MDA), glutathione (GSH), superoxide dismutase and catalase were measured in all the groups. TNF-α-308 G/C and IL-1α-889 C/T polymorphisms were analyzed using PCR-RFLP method. Correlations between genotype frequency and the level of oxidative stress markers were examined. MDA was significantly increased in the patient group in comparison to control group. GSH and SOD were significantly decreased in the patient group in comparison to control group. There was no significant difference observed in genotype frequency of TNF-α in the patient group compared with control group. IL-1α-889 C/T polymorphism may be associated with diabetic nephropathy. Moreover there was no association of TNF-α-308 G/C polymorphism with diabetic nephropathy in West Indian population. The higher serum levels of oxidative stress markers in diabetic patients with nephropathy suggest the possible role of oxidative stress.

In silico analysis of single nucleotide polymorphism (SNP) in human TNF-α gene.

The TNF-α gene mutations are seen in many diseases especially inflammatory diseases. Hence, before planning a larger population study, it is advisable to sort out the possible functional SNPs. To accomplish this goal, data available in the dbSNP database and different computer programs can be used. Therefore, this study was undertaken to find the functional nsSNPs (non-synonymous single nucleotide polymorphisms) in TNF-α. Out of the total 169 SNPs, 48 were nsSNPs (non-synonymous single nucleotide polymorphisms), 23 occurred in the mRNA 3' UTR, 10 occurred in 5' UTR region, 41 occurred in intronic regions and the rest were other types of SNPs. SIFT and PolyPhen predicted 2 out of 48 nsSNPs as damaging. Among the predicted nsSNPs, rs4645843 and rs1800620 were identified as deleterious and damaging by the SIFT (Sorting Intolerant from Tolerant) and PolyPhen programs. Additionally, I-Mutant and nsSNPAnalyzer showed a decrease in stability for these nsSNPs upon mutation. Protein structural analysis with these amino acid variants was performed by using I-Mutant, Swiss PDB viewer, ANOLEA (Atomic Non-Local Environment Assessment), MUSTER (MUlti-Sources ThreadER) and NOMAD-Ref servers to check their molecular dynamics and energy minimization calculations. This study suggested that P84L and A94T variants of TNF-α could directly or indirectly destabilize the amino acid interactions and hydrogen bond networks thus explaining the functional deviations of protein to some extent.