Novel mutation patterns in children with steroid-resistant nephrotic syndrome.

Background: Idiopathic nephrotic syndrome (NS) in children poses treatment challenges, with a subset developing steroid-resistant nephrotic syndrome (SRNS). Genetic factors play a role, yet data on paediatric SRNS genetics in India are scarce. We conducted a prospective study using whole-exome sequencing to explore genetic variants and their clinical correlations. Methods: A single-centre prospective study (October 2018-April 2023) enrolled children with SRNS, undergoing renal biopsy and genetic testing per institutional protocol. Clinical, histological, and genetic data were recorded. DNA isolation and next-generation sequencing were conducted for genetic analysis. Data collection included demographics, clinical parameters, and kidney biopsy findings. Syndromic features were evaluated, with second-line immunosuppressive therapy administered. Patient and renal outcomes are presented for patients with and without genetic variants. Results: A total of 680 paediatric NS patients were analysed, with 121 (17.8%) having SRNS and 96 consent to genetic analysis. 69 (71.9%) had early SRNS, 27 (28.1%) late. Among participants, 62 (64.58%) had reportable genetic variants. The most common were in COL4A genes, with 20 (31.7%) positive. Renal biopsy showed focal segmental glomerulosclerosis in 31/42 (74%) with variants, 16/28 (57.1%) without variants. Second-line immunosuppressions varied, with CNIs the most common. Outcomes varied, with partial or complete remission achieved in some while others progressed to ESRD. Conclusion: The study underscores the importance of genetic analysis in paediatric SRNS, revealing variants in 65.7% of cases. COL4A variants were predominant. Variants correlated with varied renal outcomes, highlighting potential prognostic implications. These findings emphasize the value of personalized approaches and further research in managing paediatric SRNS.

Association of PLCE1 (rs7922612) and COL4A3 (rs375290088) Genetic Variants with the Risk of Nephrotic Syndrome in Egyptian Pediatric Patients.

Nephrotic syndrome is one of the most prevalent pediatric kidney illnesses seen in pediatric nephrology clinics. Steroid resistance in children with nephrotic syndrome is a primary cause of renal failure and is characterized by nephrotic range proteinuria that does not respond to conventional steroid therapy. The current work was intended to investigate the possible role of the Phospholipase C epsilon 1 (rs7922612) and collagen4 alpha 3 (rs375290088) single nucleotide polymorphisms as risk factors for developing nephrotic syndrome among Egyptian children. The study was conducted on 100 children with nephrotic syndrome and 100 age- and sex-matched healthy individuals. Geno typing was performed by two methods of polymerase chain reaction for the analysis of PLCE1 (rs7922612) and COL4A3 (rs375290088) variants. We observed a higher percentage of the heterozygous and homozygous variant genotypes of PLCE1 (rs7922612) SNP in NS patients in comparison with the controls (P < 0.001 for both). The frequencies of the PLCE1 (rs7922612) variant showed a statistically significant elevated risk of NS using several genetic models, including the dominant (OR = 9.12), recessive (OR = 2.31), and allelic (OR = 1.62) models (P < 0.001 for each). In addition, the PLCE1 (rs7922612) genotypes and alleles frequencies did not differ significantly between SRNS compared to SSNS cases. Furthermore, there was no significant difference regarding COL4A3 (rs375290088) polymorphism, neither between the NS and control groups nor between SDNS and SRNS. PLCE1 (rs7922612) is considered an independent risk factor for nephrotic syndrome in Egyptian pediatrics.COL4A3 (rs375290088) polymorphism is not correlated to Egyptian NS patients.

Ocular manifestations of the genetic causes of focal and segmental glomerulosclerosis.

Genetic forms of focal and segmental glomerulosclerosis (FSGS) often have extra-renal manifestations. This study examined FSGS-associated genes from the Genomics England Renal proteinuria panel for reported and likely ocular features. Thirty-two of the 55 genes (58%) were associated with ocular abnormalities in human disease, and a further 12 (22%) were expressed in the retina or had an eye phenotype in mouse models. The commonest genes affected in congenital nephrotic syndrome (NPHS1, NPHS2, WT1, LAMB2, PAX2 but not PLCE1) may have ocular manifestations . Many genes affected in childhood-adolescent onset FSGS (NPHS1, NPHS2, WT1, LAMB2, SMARCAL1, NUP107 but not TRPC6 or PLCE1) have ocular features. The commonest genes affected in adult-onset FSGS (COL4A3-COL4A5, GLA ) have ocular abnormalities but not the other frequently affected genes (ACTN4, CD2AP, INF2, TRPC6). Common ocular associations of genetic FSGS include cataract, myopia, strabismus, ptosis and retinal atrophy. Mitochondrial forms of FSGS (MELAS, MIDD, Kearn's Sayre disease) are associated with retinal atrophy and inherited retinal degeneration. Some genetic kidney diseases (CAKUT, ciliopathies, tubulopathies) that result in secondary forms of FSGS also have ocular features. Ocular manifestations suggest a genetic basis for FSGS, often help identify the affected gene, and prompt genetic testing. In general, ocular abnormalities require early evaluation by an ophthalmologist, and sometimes, monitoring or treatment to improve vision or prevent visual loss from complications. In addition, the patient should be examined for other syndromic features and first degree family members assessed.

Copy number variation analysis in 138 families with steroid-resistant nephrotic syndrome identifies causal homozygous deletions in PLCE1 and NPHS2 in two families.

BACKGROUND: Steroid-resistant nephrotic syndrome (SRNS) is the second most common cause of kidney failure in children and adults under the age of 20 years. Previously, we were able to detect by exome sequencing (ES) a known monogenic cause of SRNS in 25-30% of affected families. However, ES falls short of detecting copy number variants (CNV). Therefore, we hypothesized that causal CNVs could be detected in a large SRNS cohort. METHODS: We performed genome-wide single nucleotide polymorphism (SNP)-based CNV analysis on a cohort of 138 SRNS families, in whom we previously did not identify a genetic cause through ES. We evaluated ES and CNV data for variants in 60 known SRNS genes and in 13 genes in which variants are known to cause a phenocopy of SRNS. We applied previously published, predefined criteria for CNV evaluation. RESULTS: We detected a novel CNV in two genes in 2 out of 138 families (1.5%). The 9,673 bp homozygous deletion in PLCE1 and the 6,790 bp homozygous deletion in NPHS2 were confirmed across the breakpoints by PCR and Sanger sequencing. CONCLUSIONS: We confirmed that CNV analysis can identify the genetic cause in SRNS families that remained unsolved after ES. Though the rate of detected CNVs is minor, CNV analysis can be used when there are no other genetic causes identified. Causative CNVs are less common in SRNS than in other monogenic kidney diseases, such as congenital anomalies of the kidneys and urinary tract, where the detection rate was 5.3%. A higher resolution version of the Graphical abstract is available as Supplementary information.

Intravenous cyclophosphamide therapy in children with calcineurin inhibitor-resistant steroid-resistant nephrotic syndrome in a resource-limited setting.

BACKGROUND: In pediatric steroid-resistant nephrotic syndrome (SRNS), calcineurin inhibitors (CNIs) are recommended as first-line therapy, with efficacy ranging between 60 and 80%, implying a substantial proportion will exhibit CNI resistance. Which alternate immunosuppressive therapy should be used in non-genetic pediatric SRNS exhibiting CNI resistance is especially relevant in low- to middle-income countries (LMIC), where the prohibitive costs of certain drugs such as monoclonal antibodies often determine therapy choice. METHODS: The primary objective was to assess the efficacy of intravenous cyclophosphamide in a proportion of children aged 1-18 years with CNI-resistant SRNS with a complete response (CR) or partial response (PR) at 6 months from commencement of pulse therapy. The secondary objectives were to assess the proportion and profile of infections and adverse effects. RESULTS: Of 90 children with idiopathic SRNS presenting between January 2013 and December 2022, 29 (32.2%) had CNI resistance and were enrolled. They were administered monthly intravenous cyclophosphamide pulses (6 pulses). Median (IQR) duration of follow-up was 48 (29.5, 63.5) months. At the end of 6 months of cyclophosphamide therapy, 13 (44.8%) attained CR and 4 (13.8%) attained PR, with an overall cyclophosphamide success rate of 58.6%. The efficacy of intravenous cyclophosphamide was higher in secondary (9/10; 90%) versus primary CNI resistance (8/19; 42.1%) (p = 0.029). Three children (3/29; 10.3%) developed systemic infections within 12 months of initiation of cyclophosphamide therapy, similar to the rate of systemic infections among children receiving CNI for SRNS management (6/41; 14.6%) (p = 0.85). CONCLUSIONS: It is prudent to try intravenous cyclophosphamide in CNI-resistant SRNS in LMIC, given the reasonable cost and good efficacy rates (58.6%).

Rituximab in combination with cyclosporine and steroid pulse therapy for childhood-onset multidrug-resistant nephrotic syndrome: a multicenter single-arm clinical trial (JSKDC11 trial).

BACKGROUND: Only 80% of children with idiopathic nephrotic syndrome respond well to glucocorticoid therapy. Multidrug-resistant nephrotic syndrome (MRNS) is associated with a poor kidney prognosis. Several retrospective studies have identified rituximab as an effective treatment for MRNS; however, prospective studies are required to assess its efficacy and safety. METHODS: We conducted a multicenter, non-blinded, single-arm trial to investigate the efficacy and safety of rituximab in patients with childhood-onset MRNS who were resistant to cyclosporine and more than three courses of steroid pulse therapy. The enrolled patients received four 375 mg/m2 doses of rituximab in combination with baseline cyclosporine and steroid pulse therapy. The primary endpoint was a > 50% reduction in the urinary protein/creatinine ratio from baseline on day 169. Complete and partial remissions were also evaluated. RESULTS: Six patients with childhood-onset MRNS were enrolled. All patients were negative for pathogenic variants of podocyte-related genes. On day 169, five patients (83.3%) showed a > 50% reduction in the urinary protein/creatinine ratio, two patients showed partial remission, and two patients showed complete remission. No deaths occurred and severe adverse events occurred in two patients (infection in one patient and acute kidney injury in one patient). Three patients needed treatment for moderate-to-severe infection. CONCLUSIONS: The study treatment effectively reduced the urinary protein/creatinine ratio in patients with childhood-onset MRNS. The adverse events in this study were within the expected range; however, attention should be paid to the occurrence of infections.

Effects of a novel ANLN E841K mutation associated with SRNS on podocytes and its mechanism.

BACKGROUND: Steroid-resistant nephrotic syndrome (SRNS) is characterized by unrelieved proteinuria after an initial 4-8 weeks of glucocorticoid therapy. Genes in podocytes play an important role in causing SRNS. OBJECTIVE: This study aimed to report a pathogenic mutation in SRNS patients and investigate its effects on podocytes, as well as the pathogenic mechanism. METHODS: We screened out a novel mutation by using whole-exon sequencing in the SRNS cohort and verified it via Sanger sequencing. Conservative analysis and bioinformatic analysis were used to predict the pathogenicity of the mutation. In vitro, stable podocyte cell lines were constructed to detect the effect of the mutation on the function of the podocyte. Moreover, an in vivo mouse model of podocyte ANLN gene knockout (ANLNpodKO) was used to confirm clinical manifestations. Transcriptome analysis was performed to identify differential gene expression and related signaling pathways. RESULTS: ANLN E841K was screened from three unrelated families. ANLN E841K occurred in the functional domain and was predicted to be harmful. The pathological type of A-II-1 renal biopsy was minimal change disease, and the expression of ANLN was decreased. Cells in the mutation group showed disordered cytoskeleton, faster cell migration, decreased adhesion, increased endocytosis, slower proliferation, increased apoptosis, and weakened interaction with CD2 association protein. ANLNpodKO mice exhibited more obvious proteinuria, more severe mesangial proliferation, glomerular atrophy, foot process fusion, and increased tissue apoptosis levels than ANLNflox/flox mice after tail vein injection of adriamycin. Upregulated differentially expressed genes in cells of the mutation group were mainly enriched in the PI3K-AKT pathway. CONCLUSION: The novel mutation known as ANLN E841K affected the function of the ANLN protein by activating the PI3K/AKT/mTOR/apoptosis pathway, thus resulting in structural and functional changes in podocytes. Our study indicated that ANLN played a vital role in maintaining the normal function of podocytes. Video Abstract.

Genetic risk variants for childhood nephrotic syndrome and corticosteroid response.

Introduction: The etiology of most cases of nephrotic syndrome (NS) remains unknown, therefore patients are phenotypically categorized based on response to corticosteroid therapy as steroid sensitive NS (SSNS), or steroid resistant NS (SRNS). Genetic risk factors have been identified for SSNS from unbiased genome-wide association studies (GWAS), however it is unclear if these loci are disease risk loci in other forms of NS such as SRNS. Additionally, it remains unknown if these risk loci are associated with response to therapy. Thus, we investigated the association between SSNS risk loci and therapy response in a large, multi-race cohort of children along the entire spectrum of childhood-onset NS. Methods: We enrolled 1,000 patients with childhood-onset NS comprised of SSNS and SRNS. Genotyping was done using TaqMan and Direct Sanger Sequencing for 9 previously reported childhood SSNS risk loci. We compared the allele frequencies (AF) and variant burden between NS vs. controls and SRNS vs. SSNS. Results: All 9 risk loci were associated with NS compared with healthy controls (p = 3.5 × 10-3-<2.2 × 10-16). Variant burden greater than 7 was associated with risk of SRNS (OR 7.4, 95% CI 4.6-12.0, p = 8.2 × 10-16). Conclusion: Our study showed that genetic risk loci for childhood SSNS are associated with pattern of therapy response, may help predict disease outcome, and set the stage for individualized treatment of NS.

Steroid-Resistant Nephrotic Syndrome Caused by NUP93 Pathogenic Variants.

BACKGROUND: Although steroid therapy is a standard of care for nephrotic syndrome treatment, 15-20% of patients do not respond to it. Finding the genetic background is possible in >10% of steroid-resistant nephrotic syndrome (SRNS) cases. Variants in genes encoding nuclear pore complex proteins are a novel cause of paediatric steroid-resistant nephrotic syndrome (SRNS). Recent studies suggest NUP93 variants to be a significant cause of paediatric onset SRNS. The clinical data on certain variants and disease history are still very limited. METHODS AND RESULTS: We report the SRNS case of a 12-year-old boy with two detected NUP93 variants, which are pathogenic and possibly pathogenic. The onset of the disease was early and severe. The patient was admitted to the paediatric nephrology department due to nephrotic-range proteinuria and hypoalbuminemia with a long medical history of steroid and non-steroid immunosuppressive treatment. The genetic panel targeting 50 genes, clinically relevant for nephrotic syndrome, was performed. The only gene which was found to be affected by mutations, namely c.2326C>T and c.1162C>T, respectively, was NUP93. Conclusions: NUP93 variants are rarely identified as causes of SRNS. Clinical data are of utmost importance to establish the standard of care for SRNS patients suffering from this genetic disfunction. This is the first case of a heterozygous patient with the c.2326C>T and c.1162C>T variants and confirmed clinical history of the SRNS described so far. Our data suggest the clinical relevance of the c.1162C>T variant.

Factors predicting the occurrence of disease-causing variants on next-generation sequencing in children with steroid-resistant nephrotic syndrome - implications for resource-constrained settings.

BACKGROUND: Enhanced availability of high-throughput sequencing (at progressively reducing costs) has revolutionized the identification of monogenic SRNS. However, in resource-poor settings, it may not be possible to perform next-generation sequencing (NGS) in all children wherein monogenic SRNS is suspected. Besides, the optimal strategy of genetic evaluation (in patients with SRNS) in routine clinical practice in resource-limited settings is unknown. METHODS: Patients with newly diagnosed SRNS were recruited from our center and followed up prospectively. We analyzed the factor(s) independently predicting the occurrence of disease-causing variants in these patients. RESULTS: In our study, 36 children/adolescents with SRNS were included (initial steroid resistance in 53%). On targeted NGS, pathogenic/likely pathogenic variants were identified in 31% (n = 11). These included homozygous or compound heterozygous variants in the following genes: ALOX12B, COL4A3, CRB2, NPHS1, NPHS2, PLCE1, and heterozygous variant in WT1 gene. Overall, 14 variants were identified of which 5 (36%) were novel. Age of < 1 or < 2 years and presence of family history of nephrotic syndrome independently predicted the occurrence of monogenic SRNS on multivariate analysis. CONCLUSIONS: While NGS-based genetic testing in SRNS is increasingly being incorporated in routine clinical practice the world over, the scenario is far from optimal in resource-limited settings. Our study highlights that resources for genetic testing in SRNS should be prioritized for patients with early age at disease onset and presence of family history. Larger studies composed of diverse multi-ethnic cohorts of patients with SRNS are required to further delineate the optimal strategy of genetic evaluation in resource-poor settings. A higher resolution version of the Graphical abstract is available as Supplementary information.

Combined novel homozygous variants in both SGPL1 and STAT1 presenting with severe combined immune deficiency: case report and literature review.

Background: Sphingosine phosphate lyase insufficiency syndrome (SPLIS) is associated with biallelic variants in SGPL1, comprising a multisystemic disease characterized by steroid resistant nephrotic syndrome, primary adrenal insufficiency, neurological problems, skin abnormalities and immunodeficiency in described cases. Signal transducer and activator of transcription 1 (STAT1) plays an important role in orchestrating an appropriate immune response through JAK-STAT pathway. Biallelic STAT1 loss of function (LOF) variants lead to STAT1 deficiency with a severe phenotype of immunodeficiency with increased frequency of infections and poor outcome if untreated. Case presentation: We report novel homozygous SGPL1 and STAT1 variants in a newborn of Gambian ethnicity with clinical features of SPLIS and severe combined immunodeficiency. The patient presented early in life with nephrotic syndrome, severe respiratory infection requiring ventilation, ichthyosis, and hearing loss, with T-cell lymphopenia. The combination of these two conditions led to severe combined immunodeficiency with inability to clear respiratory tract infections of viral, fungal, and bacterial nature, as well as severe nephrotic syndrome. The child sadly died at 6 weeks of age despite targeted treatments. Conclusion: We report the finding of two novel, homozygous variants in SGPL1 and STAT1 in a patient with a severe clinical phenotype and fatal outcome early in life. This case highlights the importance of completing the primary immunodeficiency genetic panel in full to avoid missing a second diagnosis in other patients presenting with similar severe clinical phenotype early in life. For SPLIS no curative treatment is available and more research is needed to investigate different treatment modalities. Hematopoietic stem cell transplantation (HSCT) shows promising results in patients with autosomal recessive STAT1 deficiency. For this patient's family, identification of the dual diagnosis has important implications for future family planning. In addition, future siblings with the familial STAT1 variant can be offered curative treatment with HSCT.

Epigenetic Mechanisms and Nephrotic Syndrome: A Systematic Review.

A small subset of people with nephrotic syndrome (NS) have genetically driven disease. However, the disease mechanisms for the remaining majority are unknown. Epigenetic marks are reversible but stable regulators of gene expression with utility as biomarkers and therapeutic targets. We aimed to identify and assess all published human studies of epigenetic mechanisms in NS. PubMed (MEDLINE) and Embase were searched for original research articles examining any epigenetic mechanism in samples collected from people with steroid resistant NS, steroid sensitive NS, focal segmental glomerulosclerosis or minimal change disease. Study quality was assessed by using the Joanna Briggs Institute critical appraisal tools. Forty-nine studies met our inclusion criteria. The majority of these examined micro-RNAs (n = 35, 71%). Study quality was low, with only 23 deemed higher quality, and most of these included fewer than 100 patients and failed to validate findings in a second cohort. However, there were some promising concordant results between the studies; higher levels of serum miR-191 and miR-30c, and urinary miR-23b-3p and miR-30a-5p were observed in NS compared to controls. We have identified that the epigenome, particularly DNA methylation and histone modifications, has been understudied in NS. Large clinical studies, which utilise the latest high-throughput technologies and analytical pipelines, should focus on addressing this critical gap in the literature.

A Systematic Review and Meta-Analysis of the Rate and Risk Factors for Post-transplant Disease Recurrence in Children With Steroid Resistant Nephrotic Syndrome.

Introduction: Posttransplant disease recurrence is a feared and severe complication in children with steroid resistant nephrotic syndrome (SRNS), but little is known about its incidence. Recent data suggest relapse is exceptional in patients with genetic SRNS, and initial steroid sensitivity may represent a risk factor for recurrence. Methods: Systematic review and meta-analysis were performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to describe the post-transplant relapse rate among children with SRNS; as well as the association between recurrence and all potential risk factors, including the presence of causative genetic mutations, initial steroid sensitivity, underlying histology, and gender. The inclusion criteria were as follows: (i) children with SRNS who are undergoing kidney transplant, (ii) available data on post-transplant recurrence, (iii) no patient selection according to the underlying histology, (iv) available data on genetic testing, and (v) prospective or retrospective cohort design. Results: Of the 5818 records identified, 8 studies including 581 children with SRNS met the inclusion criteria. Overall posttransplant recurrence rate was 39% (95% confidence interval [CI] 34%-44%). No genetic patient relapsed, whereas the recurrence rate in patients with no causative genetic mutation identified was 61% (95% CI 53%-69%). Children with initial steroid sensitivity were at a higher risk for recurrence with a 1.91 relative risk (RR) (95% CI 1.48-2.46) compared with those with primary SRNS (PSRNS). Gender and histology did not significantly affect relapse rate. Conclusion: Post-transplant recurrence is a common event in children with idiopathic non-genetic SRNS, complicating the clinical course in over 60% of patients. The presence of a causative genetic mutation virtually excludes a recurrence. Initial steroid sensitivity is the only other significant risk factor, doubling the risk of relapse.

Hiding in plain sight: genetics of childhood steroid-resistant nephrotic syndrome in Sub-Saharan Africa.

Steroid-resistant nephrotic syndrome (SRNS) is the most severe form of childhood nephrotic syndrome with an increased risk of progression to chronic kidney disease stage 5. Research endeavors to date have identified more than 80 genes that are associated with SRNS. Most of these genes regulate the structure and function of the podocyte, the visceral epithelial cells of the glomerulus. Although individuals of African ancestry have the highest prevalence of SRNS, especially those from Sub-Saharan Africa (SSA), with rates as high as 30-40% of all cases of nephrotic syndrome, studies focusing on the characterization and understanding of the genetic basis of SRNS in the region are negligible compared with Europe and North America. Therefore, it remains unclear if some of the variants in SRNS genes that are deemed pathogenic for SRNS are truly disease causing, and if the leading causes of monogenic nephrotic syndrome in other populations are the same for children in SSA with SRNS. Other implications of this lack of genetic data for SRNS in the region include the exclusion of children from the region from clinical trials aimed at identifying potential novel therapeutic agents for this severe form of nephrotic syndrome. This review underlines a need for concerted efforts to advance the genetic basis of SRNS in children in SSA. Such endeavors will complement global efforts at understanding the genetic basis of nephrotic syndrome.

Outcomes of steroid-resistant nephrotic syndrome in children not treated with intensified immunosuppression.

BACKGROUND: The aim of the current PodoNet registry analysis was to evaluate the outcome of steroid-resistant nephrotic syndrome (SRNS) in children who were not treated with intensified immunosuppression (IIS), focusing on the potential for spontaneous remission and the role of angiotensin blockade on proteinuria reduction. METHODS: Ninety-five pediatric patients who did not receive any IIS were identified in the PodoNet Registry. Competing risk analyses were performed on 67 patients with nephrotic-range proteinuria at disease onset to explore the cumulative rates of complete or partial remission or progression to kidney failure, stratified by underlying etiology (genetic vs. non-genetic SRNS). In addition, Cox proportional hazard analysis was performed to identify factors predicting proteinuria remission. RESULTS: Eighteen of 31 (58.1%) patients with non-genetic SRNS achieved complete remission without IIS, with a cumulative likelihood of 46.2% at 1 year and 57.7% at 2 years. Remission was sustained in 11 children, and only two progressed to kidney failure. In the genetic subgroup (n = 27), complete resolution of proteinuria occurred very rarely and was never sustained; 6 (21.7%) children progressed to kidney failure at 3 years. Almost all children (96.8%) received proteinuria-lowering renin-angiotensin-aldosterone system (RAAS) antagonist treatment. On antiproteinuric treatment, partial remission was achieved in 7 of 31 (22.6%) children with non-genetic SRNS and 9 of 27 children (33.3%) with genetic SRNS. CONCLUSION: Our results demonstrate that spontaneous complete remission can occur in a substantial fraction of children with non-genetic SRNS and milder clinical phenotype. RAAS blockade increases the likelihood of partial remission of proteinuria in all forms of SRNS. A higher resolution version of the Graphical abstract is available as Supplementary information.

High detection rate for disease-causing variants in a cohort of 30 Iranian pediatric steroid resistant nephrotic syndrome cases.

Background: Steroid resistant nephrotic syndrome (SRNS) represents a significant renal disease burden in childhood and adolescence. In contrast to steroid sensitive nephrotic syndrome (SSNS), renal outcomes are significantly poorer in SRNS. Over the past decade, extensive genetic heterogeneity has become evident while disease-causing variants are still only identified in 30% of cases in previously reported studies with proportion and type of variants identified differing depending on the age of onset and ethnical background of probands. A genetic diagnosis however can have implications regarding clinical management, including kidney transplantation, extrarenal disease manifestations, and, in some cases, even causal therapy. Genetic diagnostics therefore play an important role for the clinical care of SRNS affected individuals. Methodology and results: Here, we performed NPHS2 Sanger sequencing and subsequent exome sequencing in 30 consanguineous Iranian families with a child affected by SRNS with a mean age of onset of 16 months. We identified disease-causing variants and one variant of uncertain significance in 22 families (73%), including variants in NPHS1 (30%), followed by NPHS2 (20%), WT1 (7%) as well as in NUP205, COQ6, ARHGDIA, SGPL1, and NPHP1 in single cases. Eight of these variants have not previously been reported as disease-causing, including four NPHS1 variants and one variant in NPHS2, ARHGDIA, SGPL1, and NPHP1 each. Conclusion: In line with previous studies in non-Iranian subjects, we most frequently identified disease-causing variants in NPHS1 and NPHS2. While Sanger sequencing of NPHS2 can be considered as first diagnostic step in non-congenital cases, the genetic heterogeneity underlying SRNS renders next-generation sequencing based diagnostics as the most efficient genetic screening method. In accordance with the mainly autosomal recessive inheritance pattern, diagnostic yield can be significantly higher in consanguineous than in outbred populations.

Childhood Steroid-resistant Nephrotic Syndrome: Long-term Outcomes from a Tertiary Care Center.

Introduction: Steroid-resistant nephrotic syndrome (SRNS) is a rare condition that accounts for about 10% to 20% of all nephrotic syndromes in children. While calcineurin inhibitors induce remission in the majority, the data on long-term outcomes are limited. This retrospective study aimed to look at the clinical profile, biopsy findings, and long-term treatment outcomes in children with SRNS. Methods: The records of all children (1-18 years) with SRNS with biopsy findings of minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), or mesangioproliferative glomerulonephritis, who received treatment for a minimum period of 12 months and were in follow-up during the years 2007-2018 at a tertiary care teaching hospital were retrieved. The clinical, histopathological, and biochemical factors and treatment outcomes were recorded and analyzed. Results: Ninety-one (72 boys) children with a median (interquartile range [IQR]) age of onset of nephrotic syndrome as 48 (24-87) months were included. MCD and FSGS were the most common histopathological types (57.1% and 36.3%, respectively) and 62 (68.1%) patients had late steroid resistance. Calcineurin inhibitors (CNIs) were used in 86.8% of the children, and response rates with cyclosporine and tacrolimus for complete remission (CR) were 80% and 73.7%, respectively, with median (IQR) time to response being 3 (2-4) months. The presence of MCD on histology and the use of CNIs were significantly associated with CR (P < 0.01). At a median (IQR) follow-up of 5 (3-7) years, 76 (83.5%) children had either CR or partial remission, four (4.4%) developed chronic kidney disease and five (5.5%) died (three due to end-stage renal disease and two of infective complications). Conclusion: SRNS children with MCD on biopsy, late resistance, and response to CNIs have better long-term outcomes. Most patients respond to CNIs within the first 6 months of use and need therapy for at least 24 to 36 months.

Causal and putative pathogenic mutations identified in 39% of children with primary steroid-resistant nephrotic syndrome in South Africa.

There is a paucity of data identifying genetic mutations that account for the high rate of steroid-resistant nephrotic syndrome (SRNS) in a South African paediatric population. The aim was to identify causal mutations in genes implicated in SRNS within a South African paediatric population. We enrolled 118 children with primary nephrotic syndrome (NS), 70 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 = 118) 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 with histopathological features of focal segmental glomerulosclerosis (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 causal and putative pathogenic mutations in children with SRNS was 27/70 (39%): 15 (21%) carried the NPHS2 p.V260E causal mutation in the homozygous state, and 12 (17%) SRNS cases carried a putative pathogenic mutation in the heterozygous state in genes (INF2 (n = 8), CD2AP (n = 3) and TRPC6 (n = 1)) known to have autosomal dominant inheritance mode. NPHS2 p.V260E homozygosity was specifically associated with biopsy-proven FSGS, accounting for 24% of children of Black ethnicity (15 of 63) with steroid-resistant FSGS. No causal or putative pathogenic mutations were identified in NPHS1, WT1, LAMB2, PLCE1, MYO1E and ACTN4. We report four novel variants in INF2, PLCE1, ACTN4 and TRPC6.   Conclusion: We report putative missense variants predicted to be pathogenic in INF2, CD2AP and TRPC6 among steroid-resistant-FSGS children. However, the NPHS2 p.V260E mutation is a prevalent cause of steroid-resistant FSGS among Black South African children occurring in 24% of children with SRNS. Screening all Black African children presenting with NS for NPHS2 p.V260E will provide a precision diagnosis of steroid-resistant FSGS and inform clinical management. What is Known: • Limited data is available on the genetic disparity of SNRS in a South African paediatric setting. • The high rate of steroid resistance in Black South African children with FSGS compared to other racial groups is partially explained by the founder variant NPHS2 p.V260E. What is New: • We report putative missense variants predicted to be pathogenic in INF2, CD2AP and TRPC6 among steroid-resistant FSGS children. • NPHS2 p.V260E mutation remains a prevalent cause of steroid-resistant FSGS among Black South African children, demonstrating precision diagnostic utility.

NUP133 Controls Nuclear Pore Assembly, Transcriptome Composition, and Cytoskeleton Regulation in Podocytes.

Steroid-resistant nephrotic syndrome (SRNS) frequently leads to end-stage renal disease, ultimately requiring kidney replacement therapies. SRNS is often caused by hereditary monogenic mutations, specifically affecting specialized epithelial cells (podocytes) of the glomerular filtration barrier. Mutations in several components of the nuclear pore complex, including NUP133 and NUP107, have been recently identified to cause hereditary SRNS. However, underlying pathomechanisms, eliciting podocyte-specific manifestations of these nucleoporopathies, remained largely elusive. Here, we generated an in vitro model of NUP133-linked nucleoporopathies using CRISPR/Cas9-mediated genome editing in human podocytes. Transcriptome, nuclear pore assembly, and cytoskeleton regulation of NUP133 loss-of-function, mutant, and wild-type podocytes were analyzed. Loss of NUP133 translated into a disruption of the nuclear pore, alterations of the podocyte-specific transcriptome, and impaired cellular protrusion generation. Surprisingly, comparative analysis of the described SRNS-related NUP133 mutations revealed only mild defects. Am impaired protein interaction in the Y-complex and decrease of NUP133 protein levels might be the primary and unifying consequence of mutant variants, leading to a partial loss-of-function phenotype and disease manifestation in susceptible cell types, such as podocytes.

Spectrum of NPHS1 and NPHS2 variants in egyptian children with focal segmental glomerular sclerosis: identification of six novel variants and founder effect.

The aim of this study is to screen for variants in NPHS1 and NPHS2, in a cohort of Egyptian children with steroid-resistant nephrotic syndrome (SRNS)/focal segmental glomerulosclerosis (FSGS) and compare the prevalence of such variants among other ethnic groups. The study included 25 patients: 21 children diagnosed clinically as steroid-resistant nephrotic syndrome and confirmed as FSGS by renal biopsy and four patients diagnosed as congenital nephrotic syndrome with FSGS. Mutational analysis revealed nine NPHS2 and NPHS1 variants in 13/25 patients with a pathogenic variant detection rate of 52%. NPHS2 variants were found in 8 patients (32%) while five patients from four unrelated families (20%) harbored variants in NPHS1 gene. Six variants were not described before including a likely founder NPHS2 variant in our population, c.596dupA (p.Asn199LysfsTer14). In conclusion, we reported the largest series of patients with SRNS/FSGS from Egypt and identified many novel NPHS1 and NPHS2 variants expanding their mutational spectrum. Further studies on a larger number of patients could provide new insights into the pathogenic mechanisms of SRNS/FSGS which might help in patient's management and prognosis.