A zebrafish model of congenital nephrotic syndrome of the Finnish type.

Nephrotic syndrome (NS) is a disease characterized by proteinuria and subsequent hypoalbuminemia, hyperlipidemia and edema due to the defective renal glomerular filtration barrier (GFB). Mutations of NPHS1, encoding NEPHRIN, a podocyte protein essential for normal GFB, cause congenital nephrotic syndrome (CNS) of the Finnish type (CNF), which accounts for about 50% of CNS cases. We generated zebrafish nphs1 mutants by using CRISPR/Cas9. These mutants completely lack nephrin proteins in podocytes and develop progressive peri-orbital and whole-body edema after 5 days post fertilization. Ultra-structurally, loss of nephrin results in absence of slit-diaphragms and progressive foot process effacement in zebrafish pronephric glomeruli, similar to the pathological changes in human CNF patients. Interestingly, some nphs1 mutants are viable to adulthood despite ultra-structural defects in renal glomeruli. Using a reporter line Tg (l-fabp:VDBP-GFP) expressing GFP-tagged vitamin-D-binding protein in the blood plasma, we observed a reduction of intravascular GFP fluorescence in the nphs1 mutants, a hypoalbuminemia-like phenotype. In addition, we detected excretion of GFP by the nphs1 mutants, reminiscent of proteinuria. Therefore, we have demonstrated that the nphs1 mutant zebrafish recapitulate the human NS phenotypes and provide a novel and relevant animal model useful for screening therapeutical agents for this disease.

Nephrin and Podocin mRNA Detection in Urine Sediment of Dogs with Chronic Kidney Disease: Preliminary Observations.

Introduction: Dogs with chronic kidney disease (CKD) may have alterations in the glomerular filtration barrier, including podocyte loss. Detection of podocyte mRNA in urine could be useful for assessing podocyturia in dogs with kidney disease. The objective of this study was to evaluate the presence of nephrin mRNA (NPHS1) and podocin mRNA (NPHS2) in urine sediments of dogs with naturally occurring CKD and healthy dogs. Material and Methods: Twenty-four dogs, 14 with CKD and 10 as healthy controls, underwent clinical evaluation. The dogs with CKD were divided into two groups, according to the International Renal Interest Society criteria: stage 1 or 2 CKD (n = 5) and stage 3 or 4 CKD (n = 9). Urine was collected by catheterisation or free catch and RNA isolation from the urine sediments was optimised using glycogen as a co-precipitant. Detection of NPHS1 and NPHS2 in the sediment samples was performed using quantitative real-time PCR. Results: Both types of mRNA were detected in samples from all groups, but the percentages of detection were higher in the group of dogs with stage 1 or 2 CKD and lower in the group of dogs with stage 3 or 4 disease. Conclusion: Physiological podocyturia was observed in healthy dogs, and the results suggest differential podocyturia in dogs with CKD, according to the stage of the disease, i.e. an increase in podocyturia in dogs at stage 1 or 2 and a reduction in podocyturia in dogs at stage 3 or 4.

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.

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.

Unilateral nephrectomy for young infants with congenital nephrotic syndrome of the Finnish type.

BACKGROUND: The management of congenital nephrotic syndrome of the Finnish type (CNF) is challenging. It is difficult to withdraw intravenous albumin infusions, resulting in long-term hospitalization. In addition, fatal hypotension after bilateral nephrectomy has been reported. In our center, we have performed unilateral nephrectomy during early infancy. METHODS: Infants diagnosed with CNF between 2011 and 2020 in our institution were enrolled. We examined the clinical course before and after unilateral nephrectomy and evaluated the effectiveness of this strategy. RESULTS: Seven patients (all showing NPHS1 mutations) were enrolled. All required daily intravenous albumin infusion via central venous catheter (CVC). Unilateral nephrectomy was performed at a median of 76 days of age (59-208 days). Surgical complications did not occur in any of patients. The mean albumin dose was decreased after unilateral nephrectomy (2.0 vs 0.4 g/kg/day; p = 0.02). Intravenous albumin infusion could be withdrawn at a median of 17 days, the CVC removed at a median of 21 days, and they discharged at a median of 82 days after unilateral nephrectomy. Although bacterial infections were noted seven times before unilateral nephrectomy, only one episode occurred after surgery. Four patients initiated peritoneal dialysis at two to three years of age and all of them underwent kidney transplantation thereafter. CONCLUSIONS: Unilateral nephrectomy during early infancy may be an effective treatment allowing for withdrawal from albumin infusion, prevention of complications, withdrawal from CVCs and shortening hospital stay for patients with CNF.

Genetic Variations and Clinical Features of NPHS1-Related Nephrotic Syndrome in Chinese Children: A Multicenter, Retrospective Study.

Introduction: Few studies have addressed the genetic spectrum of NPHS1 variants in Chinese children with nephrotic syndrome. In this multicenter study, the clinical manifestations and features of NPHS1 variants in Chinese children with nephrotic syndrome were researched. Method: Genotypical and phenotypical data from 30 children affected by NPHS1 variants were collected from a multicenter registration system in China and analyzed retrospectively. Results: The patients were divided into two groups: congenital nephrotic syndrome (CNS [n = 24]) and non-CNS (early onset nephrotic syndrome [n = 6]). Renal biopsy was performed on four patients in the non-CNS group, revealing minimal change disease in three and focal segmental glomerulosclerosis in one. A total of 61 NPHS1 variants were detected, involving 25 novel variants. The "recurrent variants" included c.928G>A(p.Asp310Asn) in eight patients with CNS, followed by c.616C>A(p.Pro206Thr) in four, and c.2207T>C (p.Val736Ala) in three. Steroid treatment was applied in 29.2% (7/24)of the patients in the CNS group and 50% (3/6) of the patients in the non-CNS group. One patient in each group experienced complete remission but relapsed subsequently. Immunosuppressants were administered to three patients in the non-CNS group, eliciting an effective response. In the CNS group, three patients underwent renal transplantation and six died mainly from infection. Conclusion: Variants of NPHS1 cause CNS and early childhood-onset nephrotic syndrome. NPHS1 variants in Chinese individuals with nephrotic syndrome (NS) were mainly compound heterozygous variants, and c.928G>A(p.Asp310Asn) in exon 8 may act as a recurrent variant in the Chinese population, followed by c.616C>A(p.Pro206Thr) in exon 6. Steroids and immunosuppressants may be effective in selected patients.

The association of NPHS1 and ACNT4 gene polymorphisms with pre-eclampsia.

OBJECTIVE: The main objective of this study is to investigate the association of the NPHS1 gene polymorphisms (rs437168) and ACTN4 (rs3745895) in the pathogenesis of PE in women of African Ancestry. MATERIALS AND METHODS: 637 blood samples, normotensive pregnant (n = 280) and pre-eclampsia (n = 357) were included. The PE group was sub-divided into early onset pre-eclampsia (n = 187) and late onset pre-eclampsia (n = 170). rs74315346, rs869025495, rs121908415, rs3745895, and rs437168 were genotyped from isolated DNA using real time PCR. RESULTS: The C allele of rs437168 (NPHS1) was significantly higher in PE compared to controls. [C vs T; p = 0.0323*] and [CC vs CT/TT; p = 0.0464*]. A comparison between the subtypes of PE and controls showed that the C allele was significantly higher in EOPE compared to controls [p = 0.0027**], [CC vs CT/TT; p = 0.0111*], [CC/CT vs TT p = 0.0198*] and LOPE. [p = 0.0259*]. The other SNPs genotyped showed no signification associations with PE. CONCLUSION: This study found that the C allele of rs437168 is significantly associated with the pathogenesis of early onset PE and may be accountable for renal injury, which is a risk factor for the development of EOPE in women of African Ancestry.

A case report of congenital nephrotic syndrome caused by new mutations of NPHS1.

Congenital nephrotic syndrome (CNS) is a rare autosomal recessive disorder that occurs in the first 0 to 3 months of life. The course of CNS is progressive, often leading to end-stage renal disease within 2 to 3 years. Most patients with CNS are resistant to glucocorticoids and immunosuppressive drugs. We report a girl aged 1 month and 20 days who was admitted to hospital with a history of abdominal distension and palpebral edema. She was diagnosed with CNS and administered a glucocorticoid (methylprednisolone) for 2 years. Targeted high-throughput next-generation sequencing showed mutations in the NPHS1 gene. She had a favorable outcome after 2 years of treatment. She has remained in complete remission for the last 6 months. From a clinical point of view, the outcome of CNS may be associated with end-stage renal disease or even death. Appropriate pharmacotherapy is beneficial to maintain a normal function and integrity of the glomerular barrier. An aggressive treatment plan is required to save the life of patients with CNS, even if a heterozygous mutation is detected by genetic analysis.

Prenatal diagnosis of congenital nephrotic syndrome of the Finnish type in a Chinese family.

OBJECTIVE: To explore the genetic bias in a Chinese family suspected of having congenital nephrotic syndrome of the Finnish type (CNF). CASE REPORT: We developed a prenatal genetic diagnosis in a Chinese family with CNF. A single heterozygous mutation (c.3213delG) was found in the foetus IId and we presumed that it was an asymptomatic carrier of the normal phenotype. Additionally, two compound heterozygous variants (c.3213delG and c.3478C > T) were discovered in the foetus IIe, which were inherited from the mother and father, respectively. We performed further pathological examinations after medical abortion. Kidney histopathology and immunofluorescence results were similar to those reported in previous studies. CONCLUSION: Prenatal genetic diagnosis of CNF still requires further research to explore the pathogenicity of suspected mutations.

Case Report: A Pathogenic Missense Variant of WT1 Cosegregates With Proteinuria in a Six-Generation Chinese Family With IgA Nephropathy.

Immunoglobulin A (IgA) nephropathy (IgAN) is the most common type of primary glomerulonephritis worldwide. In addition to hematuria, proteinuria is observed in a considerable proportion of patients with IgAN and has proven to be a strong risk factor for disease progression. Although the exact pathogenesis of IgAN is still unclear, genetic factors are widely considered to play a role in its occurrence and development. Here, we investigated a large IgAN-associated pedigree of 47 members belonging to six generations. Two members of the family who presented with proteinuria and hematuria were diagnosed with IgAN through renal biopsy. Four other members also exhibited proteinuria or hematuria but without renal biopsy. Using whole-exome sequencing, we identified a likely pathogenic variant in WT1 (c.1397C>T; p.Ser466Phe) that cosegregated with proteinuria in the affected family members. In addition, another pathogenic variant in NPHS1 (c.3478C>T; p.Arg1160Ter) was identified; however, it did not cosegregate with abnormal proteinuria. Compared to individuals in the pedigree with only one heterozygous WT1 variant (c.1397C>T; p.Ser466Phe), the proband and her younger brother carried an additional WT1 variant (c.1433-10G>A) and presented with a more severe phenotype and rapid progression to end-stage kidney disease. Our findings suggest the WT1 missense variant (c.1397C>T; p.Ser466Phe)-induced primary podocyte injury might contribute to the proteinuria phenotype and IgAN progression in this pedigree.

Case Report: CMV-Associated Congenital Nephrotic Syndrome.

Background: Congenital nephrotic syndrome, historically defined by the onset of large proteinuria during the first 3 months of life, is a rare clinical disorder, generally with poor outcome. It is caused by pathogenic variants in genes associated with this syndrome or by fetal infections disrupting podocyte and/or glomerular basement membrane integrity. Here we describe an infant with congenital CMV infection and nephrotic syndrome that failed to respond to targeted antiviral therapy. Case and literature survey highlight the importance of the "tetrad" of clinical, virologic, histologic, and genetic workup to better understand the pathogenesis of CMV-associated congenital and infantile nephrotic syndromes. Case Presentation: A male infant was referred at 9 weeks of life with progressive abdominal distention, scrotal edema, and vomiting. Pregnancy was complicated by oligohydramnios and pre-maturity (34 weeks). He was found to have nephrotic syndrome and anemia, normal platelet and white blood cell count, no splenomegaly, and no syndromic features. Diagnostic workup revealed active CMV infection (positive CMV IgM/PCR in plasma) and decreased C3 and C4. Maternal anti-CMV IgG was positive, IgM negative. Kidney biopsy demonstrated focal mesangial proliferative and sclerosing glomerulonephritis with few fibrocellular crescents, interstitial T- and B-lymphocyte infiltrates, and fibrosis/tubular atrophy. Immunofluorescence was negative. Electron microscopy showed diffuse podocyte effacement, but no cytomegalic inclusions or endothelial tubuloreticular arrays. After 4 weeks of treatment with valganciclovir, plasma and urine CMV PCR were negative, without improvement of the proteinuria. Unfortunately, the patient succumbed to fulminant pneumococcal infection at 7 months of age. Whole exome sequencing and targeted gene analysis identified a novel homozygous, pathogenic variant (2071+1G>T) in NPHS1. Literature Review and Discussion: The role of CMV infection in isolated congenital nephrotic syndrome and the corresponding pathological changes are still debated. A search of the literature identified only three previous reports of infants with congenital nephrotic syndrome and evidence of CMV infection, who also underwent kidney biopsy and genetic studies. Conclusion: Complete workup of congenital infections associated with nephrotic syndrome is warranted for a better understanding of their pathogenesis ("diagnostic triad" of viral, biopsy, and genetic studies). Molecular testing is essential for acute and long-term prognosis and treatment plan.

[A case of severe congenital nephrotic syndrome secondary to NPHS1 mutation]. / Syndrome néphrotique congénital sévère avec mutation NPH S1.

The congenital nephrotic syndrome is a rare and severe pathology, and its management represents a real challenge for pediatric nephrologists. We report the case of a congenital nephrotic syndrome secondary to a homozygous mutation of the NPHS1. The young patient has a severe clinical course, and benefits of a management by anti-proteinuric treatment and a unilateral nephrectomy. This clinical case illustrates the difficulties of the management of a severe congenital nephrotic syndrome. To date, it is difficult to identify these patients beforehand because there is a poor correlation between the genotype and the phenotype of the NPHS1 mutation. There are two managements described in the literature: an early bilateral nephrectomy at 7 kg of weight with a renal transplant around 10 kg, versus a conservative management via an anti-proteinuric treatment and/or an unilateral nephrectomy. Current evidence is based on retrospective studies and the choice of a conservative approach versus early bilateral nephrectomy should take into account the severity of protein loss and its complications.

Le syndrome néphrotique congénital est une pathologie rare et sévère, dont la prise en charge représente un défi pour les néphrologues pédiatriques. Nous rapportons le cas d'un jeune patient présentant cette pathologie secondaire à une mutation homozygote du gène NPHS1. Il présente un tableau clinique sévère et bénéficie d'un traitement anti-protéinurique et d'une néphrectomie unilatérale. Ce cas clinique illustre les difficultés de la prise en charge des cas sévères, dont l'identification préalable est difficile à ce jour car la corrélation entre le génotype et le phénotype de la mutation NPHS1 est pauvre. Il existe deux prises en charges décrites dans la littérature : une néphrectomie bilatérale précoce vers 7 kg de poids et une greffe rénale vers 10 kg, ou bien une prise en charge conservative via un traitement anti-protéinurique et/ou une néphrectomie unilatérale permettant de postposer la greffe. Les données actuelles n'étant basées que sur des études rétrospectives, le choix entre une approche conservative et une néphrectomie bilatérale précoce doit prendre en compte la sévérité de la déperdition protéique et ses complications.

Structural features and oligomeric nature of human podocin domain.

Podocytes are crucial cells of the glomerular filtration unit and plays a vital role at the interface of the blood-urine barrier. Podocyte slit-diaphragm is a modified tight junction that facilitates size and charge-dependent permselectivity. Several proteins including podocin, nephrin, CD2AP, and TRPC6 form a macromolecular assembly and constitute the slit-diaphragm. Podocin is an integral membrane protein attached to the inner membrane of the podocyte via a short transmembrane region (101-125). The cytosolic N- and C-terminus help podocin to attain a hook-like structure. Podocin shares 44% homology with stomatin family proteins and similar to the stomatin proteins, podocin was shown to associate into higher-order oligomers at the site of slit-diaphragm. However, the stoichiometry of the homo-oligomers and how it partakes in the macromolecular assemblies with other slit-diaphragm proteins remains elusive. Here we investigated the oligomeric propensity of a truncated podocin construct (residues:126-350). We show that the podocin domain majorly homo-oligomerizes into a 16-mer. Circular dichroism and fluorescence spectroscopy suggest that the 16-mer oligomer has considerable secondary structure and moderate tertiary packing.

Congenital nephrotic syndrome: is early aggressive treatment needed? Yes.

Congenital nephrotic syndrome (CNS) was primarily considered one disease entity. Hence, one treatment protocol was proposed in the beginning to all CNS patients. Today, with the help of gene diagnostics, we know that CNS is a heterogeneous group of disorders and therefore, different treatment protocols are needed. The most important gene defects causing CNS are NPHS1, NPHS2, WT1, LAMB2, and PLCE1. Before active treatment, all infants with CNS died. It was stated already in the mid-1980s that intensive medical therapy followed by kidney transplantation (KTx) should be the choice of treatment for infants with severe CNS. In Finland, early aggressive treatment protocol was adopted from the USA and further developed for treatment of children with the Finnish type of CNS. The aim of this review is to state reasons for "early aggressive treatment" including daily albumin infusions, intensified nutrition, and timely bilateral nephrectomy followed by KTx at the age of 1-2 years.

Home Albumin Infusion Therapy, Another Alternative Treatment in Patients With Congenital Nephrotic Syndrome of the Finnish Type.

Background: Congenital nephrotic syndrome of the Finnish type (CNF) is a rare, severe glomerular disease caused by mutations in the NPHS1 gene, which codes for nephrin. It is characterised by massive proteinuria and severe edoema. Progression to end-stage kidney failure occurs during early childhood and the only curative treatment is kidney transplantation. Nowadays, patients need aggressive medical treatment, which includes daily albumin infusions (for months) until they get clinical stability to receive transplant. Objective: In our paediatric hospital, we implemented a multidisciplinary program for the home infusion of albumin with outpatient follow-up. The aim of the study was to assess the safety and efficacy of this program for the first four years of its implementation. Material and Methods: Retrospective observational study of CNF paediatric patients treated with home albumin infusion therapy from March 2014 to July 2018 at a tertiary care paediatric hospital. Information on albumin administration was obtained from the electronic prescription assistance program and details on clinical and care-related variables from the hospital's electronic information systems. Results: Four patients with CNF received albumin infusions for 18, 21, 22 months, and 3 years. The treatment was safe, and the complication rates were to be expected considering the severity of disease. Patients required a median of two hospital admissions a year (19 in total); 47% due to catheter-related complications, but there were just three catheter infections. Conclusions: In our experience, home albumin infusion therapy is safe and effective and helps to improve children health and quality of life.

Genetics and ESKD Disparities in African Americans.

African Americans have a 2- to 4-fold greater incidence of end-stage kidney disease (ESKD) than whites, which has long raised the possibility of a genetic cause for this disparity. Recent advances in genetic studies have shown a causal association of polymorphisms at the apolipoprotein L1 gene (APOL1) with the markedly increased risk for the nondiabetic component of the overall disparity in ESKD in African Americans. Although APOL1-associated kidney disease is thought to account for a substantial proportion of ESKD in African Americans, not all the increased risk for ESKD is accounted for, and a complete cataloging of disparities in genetic causes of ESKD eludes our current understanding of genetic-associated kidney disease. Genetic testing aids the screening, diagnosis, prognosis, and treatment of diseases with a genetic basis. Widespread use of genetic testing in clinical practice is limited by the small number of actionable genetic variants, limited health literacy of providers and patients, and underlying complex ethical, legal, and social issues. This perspective reviews racial and ethnic differences associated with genetic diseases and the development of ESKD in African Americans and discusses potential uncertainties associated with our current understanding of penetrance of genetically linked kidney disease and population-attributable risk percent.

Congenital nephrotic syndrome associated with 22q11.2 duplication syndrome in a Chinese family and functional analysis of the intronic NPHS1 c. 3286 + 5G > A mutation.

BACKGROUND: Congenital nephrotic syndrome (CNS), which is defined as heavy proteinuria, hypoalbuminemia, hyperlipidemia and edema, is most caused by monogenic defects in structural proteins of the glomerular filtration barrier in the kidneys. 22q11.2 duplication syndrome was a chromosomal disease with variable clinical featuresranging from normal to mental retardation and with congenital defects. Co-occurrence of two genetic disorders in a single patient is rare. CASE PRESENTATION: The proband was born at 36 weeks of gestational age spontaneously and weighed 2350 g at birth. Six days after birth, the proband was admitted to our hospital due to fever of 38.5 °C lasting for 6 h. Physical examination at admission time showed dysmorphic features of hypertelorism, palpebral edema, broad nose bridge, upturned nose, dysmorphic auricle, long philtrum, and a thin upper lip. Additionally, we found left wrist drop and bilateral strephexopodia, bilateral knee joint flexion contracture in this patient. A series of indicators were detected and showed abnormalities. Albumin was used to remit the hypoproteinemia and edema. However, the parents refused to accept further therapy and the boy died at age 3 months due to cachexy. To confirm the pathogenesis, genetic analysis were performed and revealed two mutations of NPHS1 gene: Exon18: c.2386G > C; p. (Gly796Arg) inherited from mother, and intron24: c.3286 + 5G > A; p.? inherited from father. And he also had a 22q11.2 duplication which was inherited from his mild affected mother. The pathogenesis of the intronic mutation has been further identified that it can defect alternative splicing of NPHS1. CONCLUSIONS: We present a patient who was caught in congenital nephrotic syndrome and 22q11.2 duplication syndrome simultaneously, emphasizing the importance of new sequencing technology on diagnosis of different genetic disorders.

A Systematic Analysis of Major Susceptible Genes in Childhood-onset Steroid-resistant Nephrotic Syndrome.

AIM: Nephrotic syndrome is a urinary disease, causing high morbidity and mortality. However, the mutation prevalence of major susceptible genes in childhood-onset steroid-resistant nephrotic syndrome (SRNS) in China is limited. In this study, we performed a systematic analysis of the mutations in 18 major SRNS-susceptible genes in Chinese SRNS children. METHODS: Mutation analysis was performed to sequence 18 major SRNS-susceptible genes (NPHS1, NPHS2, CD2AP, PLCE1, ACTN4, TRPC6, INF2, WT1, LMX1B, LAMB2, LAMB3, GLA, ITGB4, SCARB2, COQ2, PDSS2, MTTL1, and SMARCAL1) using a PCR-based MassArray technology in 38 childhood-onset SRNS patients in China. This cohort included 10 sporadic cases and 28 familial cases from 7 SRNS families with disease onset between the ages of 1-13 years. RESULTS: Our analysis detected a heterozygous missense mutation (p.E447K, pathogenic) in NPHS1 in 3/28 familial patients (10.7%) and 1/10 (10.0%) patient without a family history. In addition, two NPHS2 mutations (p.R138X and p.R291W, pathogenic) were identified in 2 patients from another family (7.1% familial cases, 0% sporadic cases, 5.2% overall). Pathogenic mutations of remaining 16 SRNS-susceptible genes were not detected. CONCLUSION: Our results have verified the significant prevalence of pathogenic NPHS1 and NPHS2 mutations in childhood-onset SRNS in China, while the other 16 SRNS-susceptible genes seem to have lesser contribution to child-onset SRNS. Therefore, our study indicates that it is very necessary to make more efforts to target NPHS1 and NPHS2 for childhood-onset SRNS treatment, especially in China.

A comprehensive analysis of NPHS1 gene mutations in patients with sporadic focal segmental glomerulosclerosis.

BACKGROUND: Focal segmental glomerulosclerosis (FSGS) is still one of the common causes of refractory nephrotic syndrome. Nephrin, encoded by podocyte-specific NPHS1 gene, participated in the pathogenesis of FSGS. The sites of NPHS1 mutations in FSGS is not clarified very well. In this study, we investigated the specific mutations of NPHS1 gene in Chinese patients with sporadic FSGS. METHODS: A total of 309 patients with sporadic FSGS were collected and screened for NPHS1 mutations by second-generation sequencing. The variants were compared with those extracted from 2504 healthy controls in the 1000 Genomes Project. The possible pathogenic roles of missense variants were predicted by three different software. We also compared these candidate causal mutations with those summarized from the previous studies. RESULTS: Thirty-two genetic mutations of NPHS1 gene were identified in FSGS patients, including 12 synonymous mutations, 17 missense mutations, 1 splicing mutation, and 2 intron mutations, of which c.G3315A (p.S1105S) was the most common variant (261/309). A novel missense mutation c.G2638 T (p.V880F) and a novel splicing mutation 35830957 C > T were identified in FSGS patients. The frequencies of the four synonymous mutations (c.C294T [p.I98I], c.C2223T [p.T741 T], c.C2289T [p.V763 V], c.G3315A [p.S1105S]) were much higher in FSGS patients than in controls. The frequencies of the four missense mutations (c.G349A [p.E117K], c.G1339A [p.E447K], c.G1802C [p.G601A], c.C2398T [p.R800C]) were much higher and one (c.A3230G [p.N1077S]) was lower in FSGS patients than in controls. Five missense mutations, c.C616A (p.P206T), c.G1802C (p.G601A), c.C2309T (p.P770L), c.G2869C (p.V957 L), and c.C3274T (p.R1092C), were predicted to be pathogenic mutations by software analysis. CONCLUSIONS: NPHS1 gene mutations were quite common in sporadic FSGS patients. We strongly recommend mutation analysis of the NPHS1 gene in the clinical management of FSGS patients.