Causal and Putative Pathogenic Mutations Identified in 38.6% of Children with Primary SRNS in South Africa

The aim was to identify causal mutations in genes implicated in steroid resistant nephrotic syndrome (SRNS) within a South African population. We enrolled 119 children with primary NS; 71 SRNS and 48 steroid-sensitive NS. All children with SRNS underwent kidney biopsy. We first genotyped the NPHS2 gene for the p.V260E variant in all NS cases (n= 119) and controls (n= 219). To further identify additional variants, we performed whole-exome sequencing and interrogated ten genes (NPHS1, NPHS2, WT1, LAMB2, ACTN4, TRPC6, INF2, CD2AP, PLCE1, MYO1E) implicated in SRNS/FSGS in 56 SRNS cases and 29 controls; we also performed exome sequencing on two patients carrying the NPHS2 p.V260E mutation as positive controls. The overall detection rate of pathogenic mutations in children with SRNS was 27/70(38.57%): 15(21.43%) carried the NPHS2 p.V260E mutation and 12(17.14%) carried a pathogenic mutation in the heterozygous state in INF2 (n=8), CD2AP (n=3) or TRPC6 (n=1) genes. NPHS2 p.V260E homozygosity was specifically associated with biopsy-proven FSGS, accounting for 23.81% of Black children (15 of 63) with SR-FSGS. No causal mutations were identified in NPHS1, WT1, LAMB2, PLCE1, MYO1E and ACTN4. We report four novel variants in INF2, PLCE1, ACTN4 and TRPC6.Conclusion: The NPHS2 p.V260E mutation is a prevalent cause of SR-FSGS among Black South African children occurring in 23.81% of children with SRNS. Screening all Black African children presenting with NS for NPHS2 p.V260E will provide a precision diagnosis of SR-FSGS and inform clinical management.

An updated view of the pathogenesis of steroid-sensitive nephrotic syndrome

Idiopathic nephrotic syndrome is the most common childhood glomerular disease. Most forms of this syndrome respond to corticosteroids at standard doses and are, therefore, defined as steroid-sensitive nephrotic syndrome (SSNS). Immunological mechanisms and subsequent podocyte disorders play a pivotal role in SSNS and have been studied for years; however, the precise pathogenesis remains unclear. With recent advances in genetic techniques, an exhaustive hypothesis-free approach called a genome-wide association study (GWAS) has been conducted in various populations. GWASs in pediatric SSNS peaked in the human leukocyte antigen class II region in various populations. Additionally, an association of immune-related CALHM6/FAM26F, PARM1, BTNL2, and TNFSF15 genes, as well as NPHS1, which encodes nephrin expressed in podocytes, has been identified as a locus that achieves genome-wide significance in pediatric SSNS. However, the specific mechanism of SSNS development requires elucidation. This review describes an updated view of SSNS pathogenesis from immunological and genetic aspects, including interactions with infections or allergies, production of circulating factors, and an autoantibody hypothesis.

Association between HLA alleles and sub-phenotype of childhood steroid-sensitive nephrotic syndrome

Background Few studies have addressed the effects of human leukocyte antigen (HLA) alleles on different clinical sub-phenotypes in childhood steroid-sensitive nephrotic syndrome (SSNS), including SSNS without recurrence (SSNSWR) and steroid-dependent nephrotic syndrome/frequently relapse nephrotic syndrome (SDNS/FRNS). In this study, we investigated the relationship between HLA system and children with SSNSWR and SDNS/FRNS and clarified the value of HLA allele detection for precise typing of childhood SSNS. Methods A total of 241 Chinese Han individuals with SSNS were genotyped using GenCap-WES Capture Kit, and four-digit resolution HLA alleles were imputed from available Genome Wide Association data. The distribution and carrying frequency of HLA alleles in SSNSWR and SDNS/FRNS were investigated. Additionally, logistic regression and mediating effects were used to examine the relationship between risk factors for disease process and HLA system. Results Compared with SSNSWR, significantly decreased serum levels of complement 3 (C3) and complement 4 (C4) at onset were detected in SDNS/FRNS (C3, P < 0.001; C4, P = 0.018). The average time to remission after sufficient initial steroid treatment in SDNS/FRNS was significantly longer than that in SSNSWR (P = 0.0001). Low level of C4 was further identified as an independent risk factor for SDNS/FRNS (P = 0.008, odds ratio = 0.174, 95% confidence interval 0.048–0.630). The HLA-A*11:01 allele was independently associated with SSNSWR and SDNS/FRNS (P = 0.0012 and P = 0.0006, respectively). No significant HLA alleles were detected between SSNSWR and SDNS/FRNS. In addition, a mediating effect among HLA-I alleles (HLA-B*15:11, HLA-B*44:03 and HLA-C*07:06), C4 level and SDNS/FRNS was identified. Conclusions HLA-I alleles provide novel genetic markers for SSNSWR and SDNS/FRNS. HLA-I antigens may be involved in steroid dependent or frequent relapse in children with SSNS as mediators of immunoregulation.

Biomarkers Predicting Treatment-Response in Nephrotic Syndrome of Children: A Systematic Review

Purpose: Nephrotic syndrome (NS) is the most common form of glomerulopathy in children. Most pediatric patients respond to glucocorticosteroid treatment (steroid-sensitive NS, SSNS), while approximately 10–15% will remain unresponsive or later become steroid-resistant. There has been a long-standing effort to find biomarkers that may predict steroid responsiveness.Methods: We systematically reviewed current studies which investigated clinically relevant biomarkers for predicting steroid responsiveness in pediatric NS. We performed a PubMed and EMBASE search to identify eligible articles. We collected data on urinary markers, blood/serum markers (including cellular phenotypes and mRNA expression), genotypes and HLA allele frequency.Results: A total of 659 articles were identified following electronic and manual searches. After reviewing the titles, abstracts, and full texts, 72 eligible articles were finally included. Vitamin D-binding protein (VDBP) seemed to be significantly elevated in SRNS than in SSNS, in both serum and urine specimen, although further validation is required.Conclusions: The present paper narratively illustrates current understandings of potential biomarkers that may help predict steroid responsiveness. Further investigation and collaboration involving a larger number of patients are necessary.

Urinary MicroRNA Expression Analysis of miR-1, miR-215, miR-335, Let-7ain Childhood Nephrotic Syndrome

Background Recently, urinary exosomal miRNAs are gaining increasing attention as their expression profiles are often associated with specific diseases and they exhibit great potential as noninvasive biomarkers for the diagnosis of various diseases. The present study was aimed to evaluate the expression status of selected miRNAs (miR-1, miR-215-5p, miR-335-5p and let-7a-5p) in urine samples from children with NS [steroid sensitive (SSNS)] and [steroid resistant (SRNS)] along with healthy control group.Methods MicroRNA isolation was carried out in urine samples collected from SSNS (100 nos), SRNS (100 nos), and healthy controls (50 nos) using MiRNeasy Mini Kit, followed by cDNA conversion for all the four selected miRNAs using Taqman advanced miRNA cDNA synthesis kit and their expression was quantified by Taqman Advanced miRNA assay kits using Real Time PCR Machine and Rotogen-Q in SSNS and SRNS patients and healthy control subjects.ResultsQuantification of all the four miRNAs (miR-1, mir-215, miR-335, let 7a) were found to be upregulated in both SSNS and SRNS as compared to control group. Further, the comparison of microRNAs within the case groups revealed significant downregulation of three microRNAs - miR-1, miR-215, miR- 335 and upregulation of let-7a in SRNS group as compared to SSNS. The t-test performed for all the four miRNAs was found to be statistically significant. ConclusionsThe aberrant expression of all the four microRNAs in both SSNS and SRNS as compared to healthy subjects may serve as novel biomarkers to distinguish between NS and healthy controls. The differential expression of microRNA let-7a is useful to discriminate SSNS and SRNS.

Role of Zinc Supplementation in Reducing Relapses in Steroid Sensitive Nephrotic Syndrome

Objective: To evaluate and compare the effectiveness of zinc and B-Complex supplementation to prevent the recurrence of nephrotic syndrome in the cases priory responsive to corticosteroid therapy. Methodology It is a randomized controlled trial conducted at OPD Pediatric medicine, Shaheed Zulfiqar Ali Bhutto University, PIMS Children Hospital Islamabad from October 3, 2016 to April 2, 2017. 192 patients (96 in each group) were included in the study after obtaining informed consent from parents or guardians taken before determining the population. Patients were randomly assigned to two groups (Group 1: Zinc and Group 2: B-Complex) to receive oral zinc sulphate (10 mg / day) or B-Complex using a random number table. The patients were followed up after 4 months. All data were collected by the researchers themselves in a structured form. Results: The age of 192 participants of the trial averaged 6.38±3.42 years of age ranging from 1-12 years. There were 88 (45.8%) men and 104 (54.2%) women cases. In group 1, there were 22 (22.9%) and in group 2, there were 47 (49%) cases that had been pardoned. The recurrence of nephrotic syndrome was significantly higher in group 1 than group 2 (p = <0.001). Conclusion: The findings of this study suggest that Zinc supplementation is more preferrable to B-Complex supplementation as the rate of continuous remission was higher in the zinc group, so in the future may be added to the treatment regimen to treat steroid-sensitive nephrotic syndrome.

Novel TBC1D8B Variant in a 6-Month-Old Boy With Steroid-Sensitive Nephrotic Syndrome: A Case Report

A structural abnormality or dysfunction of podocytes is the major cause of nephrotic syndrome (NS). The TBC1D8B protein interacts with nephrin, a podocyte slit diaphragm protein, regulates vesicle transport, and functions in the pathogenesis of NS. We report a novel potentially pathogenic variant in the TBC1D8B gene in a 6-month-old boy with NS. A 6-month-old boy was admitted to the hospital because of edema and fever. Our systematic examination led to a diagnosis of NS. Because of the early age of onset, we performed trio whole-exome sequencing of him and his parents. The results showed a new potentially pathogenic variant in the TBC1D8B gene on the X chromosome, c.2717A&gt;G (p.His906Arg). After routine glucocorticoid therapy, his urine protein turned negative, indicating steroid-sensitive NS. The new TBC1D8B variant identified here, c.2717A&gt;G (p.His906Arg), may be associated with early-onset NS in children. Although NS due to pathogenic variants in this gene is more commonly steroid-resistant, our patient had steroid-sensitive NS.