NPHS2 Mutations Research Articles

A molecular genetic analysis of childhood nephrotic syndrome in a cohort of Saudi Arabian families

Nephrotic syndrome (NS) is a renal disease characterized by heavy proteinuria, hypoalbuminemia, edema and hyperlipidemia. Its presentation within the first 3 months of life or in multiple family members suggests an underlying inherited cause. To determine the frequency of inherited NS, 62 cases (representing 49 families with NS) from Saudi Arabia were screened for mutations in NPHS1, NPHS2, LAMB2, PLCE1, CD2AP, MYO1E, WT1, PTPRO and Nei endonuclease VIII-like 1 (NEIL1). We detected likely causative mutations in 25 out of 49 families studied (51%). We found that the most common genetic cause of NS in our cohort was a homozygous mutation in the NPHS2 gene, found in 11 of the 49 families (22%). Mutations in the NPHS1 and PLCE1 genes allowed a molecular genetic diagnosis in 12% and 8% of families, respectively. We detected novel MYO1E mutations in three families (6%). No mutations were found in WT1, PTPRO or NEIL1. The pathogenicity of novel variants was analyzed by in silico tests and by genetic screening of ethnically matched control populations. This is the first report describing the molecular genetics of NS in the Arabian Peninsula.

NPHS2 and CD2AP gene mutation in children with primary steroid-resistant nephrotic syndrome in Guangdong province

Objective To study NPHS2 and CD2AP gene mutation with primary steroid-resistant nephrotic syndrome (SRNS) children in Guangdong province, and to investigate the relationship between NPHS2, CD2AP gene mutation and SRNS, so as to provide a theoretical basis for the diagnosis and treatment of SRNS in children. Methods Twenty-six SRNS children and 20 cases of the healthy children as controls were chosen randomly in Guangdong pro-vince.Genomic DNA was isolated from peripheral blood leucocytes of these patients and the healthy children.Mutational analysis was performed in 8 exons of NPHS2 gene and 18 exons of CD2AP gene after sequencing directly.The results were compared with United States National Center for Biotechnology Information(NCBI) gene database, the detected gene mutation. Results The variation analysis revealed 3 polymorphisms (288C>T, 954T>C, 1038A>G) in 14 cases out of 26 patients and 4 cases of the healthy children studied, which had been reported before, but there was no significant difference in the genotypic and allelic frequencies of these polymorphisms between the patients and the controls(all P>0.05). One CD2AP heterozygous mutation(1917+ 20 C>G) was detected in intron in 2 cases of SRNS children. Conclusions NPHS2 gene variation may not be the main mechanism of SRNS in Guangdong province.CD2AP gene mutation may increase the possibility of SRNS and focal segmental glomerulosclerosis in children.CD2AP mutation in intron may involve in the pathogenesis of SRNS. Key words: Steroid-resistant nephrotic syndrome; NPHS2 gene; CD2AP gene

A Novel Domain Regulating Degradation of the Glomerular Slit Diaphragm Protein Podocin in Cell Culture Systems

Mutations in the gene NPHS2 are the most common cause of hereditary steroid-resistant nephrotic syndrome. Its gene product, the stomatin family member protein podocin represents a core component of the slit diaphragm, a unique structure that bridges the space between adjacent podocyte foot processes in the kidney glomerulus. Dislocation and misexpression of slit diaphragm components have been described in the pathogenesis of acquired and hereditary nephrotic syndrome. However, little is known about mechanisms regulating cellular trafficking and turnover of podocin. Here, we discover a three amino acids-comprising motif regulating intracellular localization of podocin in cell culture systems. Mutations of this motif led to markedly reduced degradation of podocin. These findings give novel insight into the molecular biology of the slit diaphragm protein podocin, enabling future research to establish the biological relevance of podocin turnover and localization.

Simultaneous Sequencing of 24 Genes Associated with Steroid-Resistant Nephrotic Syndrome

Up to 95% of children presenting with steroid-resistant nephrotic syndrome in early life will have a pathogenic single-gene mutation in 1 of 24 genes currently associated with this disease. Others may be affected by polymorphic variants. There is currently no accepted diagnostic algorithm for clinical genetic testing. The hypothesis was that the increasing reliability of next generation sequencing allows comprehensive one-step genetic investigation of this group and similar patient groups. This study used next generation sequencing to screen 446 genes, including the 24 genes known to be associated with hereditary steroid-resistant nephrotic syndrome. The first 36 pediatric patients collected through a national United Kingdom Renal Registry were chosen with comprehensive phenotypic detail. Significant variants detected by next generation sequencing were confirmed by conventional Sanger sequencing. Analysis revealed known and novel disease-associated variations in expected genes such as NPHS1, NPHS2, and PLCe1 in 19% of patients. Phenotypically unexpected mutations were also detected in COQ2 and COL4A4 in two patients with isolated nephropathy and associated sensorineural deafness, respectively. The presence of an additional heterozygous polymorphism in WT1 in a patient with NPHS1 mutation was associated with earlier-onset disease, supporting modification of phenotype through genetic epistasis. This study shows that next generation sequencing analysis of pediatric steroid-resistant nephrotic syndrome patients is accurate and revealing. This analysis should be considered part of the routine genetic workup of diseases such as childhood steroid-resistant nephrotic syndrome, where the chance of genetic mutation is high but requires sequencing of multiple genes.

Glomerulopathy and mutations in NPHS1 and KIRREL2 in soft-coated Wheaten Terrier dogs

Dogs of the soft-coated wheaten terrier breed (SCWT) are predisposed to adult-onset, genetically complex, protein-losing nephropathy (average onset age = 6.3 ± 2.0 years). A genome-wide association study using 62 dogs revealed a chromosomal region containing three statistically significant SNPs (p(raw) ≤ 4.13 × 10(-8); p(genome) ≤ 0.005) when comparing DNA samples from affected and geriatric (≥14 years) unaffected SCWTs. Sequencing of candidate genes in the region revealed single nucleotide changes in each of two closely linked genes, NPHS1 and KIRREL2, which encode the slit diaphragm proteins nephrin and Neph3/filtrin, respectively. In humans, mutations in nephrin and decreased expression of Neph3 are associated with podocytopathy and protein-losing nephropathy. The base substitutions change a glycine to arginine in the fibronectin type 3 domain of nephrin and a proline to arginine in a conserved proline-rich region in Neph3. These novel mutations are not described in other species, nor were they found in 550 dogs of 105 other breeds, except in 3 dogs, including an affected Airedale terrier, homozygous for both substitutions. Risk for nephropathy is highest in dogs homozygous for the mutations (OR = 9.06; 95 % CI = 4.24-19.35). This is the first molecular characterization of an inherited podocytopathy in dogs and may serve as a model for continued studies of complex genetic and environmental interactions in glomerular disease.

Short Communication Mutations in NPHS2 (podocin) in Mexican children with nephrotic syndrome who respond to standard steroid treatment

Human nephrotic syndrome has been related to mutations in glomerular proteins. Mutations in the NPHS2 gene that encodes podocin have been described as responsible for steroid-resistant nephrotic syndrome. It has been advised to test for NPHS2 mutations in parallel or before giving steroid treatment in nephrotic syndrome patients in order to avoid unnecessary therapy. We identified NPHS2 mutations in Mexican children with nephrotic syndrome. The study included 13 children with nephrotic syndrome and 2 healthy control individuals; 8 patients were steroid-resistant and 5 were steroid-sensitive. We analyzed the 3rd exon of NPHS2 by DNA sequencing. Podocin heterozygous missense mutations L139R and L142P were found; the former was found in both steroid-sensitive and steroid-resistant children, while the latter was found in a steroid-resistant child. We conclude that NPHS2 mutations should be investigated to help decide the course of treatment in nephrotic syndrome patients.

CD80, suPAR and nephrotic syndrome in a case of NPHS2 mutation.

Podocin mutations are characterized by progression to end stage renal disease and histologic findings of Focal Segmental Glomerulosclerosis (FSGS). CD80 is a podocytes protein that may play a role in proteinuria, particularly in Minimal Change Disease whereas the soluble urokinase receptor (suPAR) is characteristically elevated in the serum of FSGS patients. In a patient with nephrotic syndrome and podocin mutation, urinary and serum CD80 as well as suPAR were measured using commercially available kits. Urinary CD80 molecular size was determined by western blot analysis. Glomerular staining for CD80 and podocin was performed. Patient displayed marked elevated CD80 and mildly increased suPAR urinary levels compared to controls. Serum CD80 level was within the range observed in normal controls. Serum suPAR level was elevated, albeit in the lower range reported for patients with primary FSGS. Immunofluorescence examination of kidney biopsy revealed glomerular CD80 expression. The combination of serum and urinary biomarkers can help differentiate various forms of FSGS. High urinary CD80 and elevated serum and urinary suPAR might represent a profile to differentiate this genetic form of FSGS from primary FSGS.

NPHS2 p.V290M mutation in late-onset steroid-resistant nephrotic syndrome

The most frequently mutated gene of steroid-resistant nephrotic syndrome (SRNS) is NPHS2. Current guidelines propose the sequencing of all NPHS2 exons only in childhood-onset SRNS. A cohort of 38 Hungarian patients with childhood-onset nephrotic-range proteinuria was screened for NPHS2 mutations. The frequency of the p.V290M mutation in late-onset SRNS was examined in the French and PodoNet cohorts. Of the 38 Hungarian patients screened, seven carried NPHS2 mutations on both alleles, of whom two-diagnosed with proteinuria through school screening programs at the age of 9.7 and 14years, respectively-did not develop nephrotic syndrome in childhood. The first, an 18-year-old boy, homozygous for p.V290M, has never developed edema. The second, a 31-year-old woman-compound heterozygous for p.V290M and p.R138Q-was first detected with hypoalbuminemia (<30g/l) and edema at the age of 24.3 and 27.5years, respectively. Both patients currently have a normal glomerular filtration rate. The mutation p.V290M was carried by three of the 38 patients in the Hungarian cohort, by two of the 95 patients with late-onset SRNS in the PodoNet cohort and by none of the 83 patients in the French cohort. We propose that not only the p.R229Q variant, but also the p.V290M mutation should be screened in Central and Eastern European patients with late-onset SRNS.

Circulating suPAR in Two Cohorts of Primary FSGS

Overexpression of soluble urokinase receptor (suPAR) causes pathology in animal models similar to primary FSGS, and one recent study demonstrated elevated levels of serum suPAR in patients with the disease. Here, we analyzed circulating suPAR levels in two cohorts of children and adults with biopsy-proven primary FSGS: 70 patients from the North America-based FSGS clinical trial (CT) and 94 patients from PodoNet, the Europe-based consortium studying steroid-resistant nephrotic syndrome. Circulating suPAR levels were elevated in 84.3% and 55.3% of patients with FSGS patients in the CT and PodoNet cohorts, respectively, compared with 6% of controls (P<0.0001); inflammation did not account for this difference. Multiple regression analysis suggested that lower suPAR levels associated with higher estimated GFR, male sex, and treatment with mycophenolate mofetil. In the CT cohort, there was a positive association between the relative reduction of suPAR after 26 weeks of treatment and reduction of proteinuria, with higher odds for complete remission (P=0.04). In the PodoNet cohort, patients with an NPHS2 mutation had higher suPAR levels than those without a mutation. In conclusion, suPAR levels are elevated in geographically and ethnically diverse patients with FSGS and do not reflect a nonspecific proinflammatory milieu. The associations between a change in circulating suPAR with different therapeutic regimens and with remission support the role of suPAR in the pathogenesis of FSGS.

SIRPα interacts with nephrin at the podocyte slit diaphragm

The slit diaphragm (SD) is an intercellular junction between renal glomerular epithelial cells (podocytes) that is essential for permselectivity in glomerular ultrafiltration. The SD components, nephrin and Neph1, assemble a signaling complex in a tyrosine phosphorylation dependent manner, and regulate the unique actin cytoskeleton of podocytes. Mutations in the NPHS1 gene that encodes nephrin cause congenital nephrotic syndrome (CNS), which is characterized by the loss of the SD and massive proteinuria. Recently, we have identified the expression of the transmembrane glycoprotein signal regulatory protein α (SIRPα) at the SD. In the present study, we analyzed the expression of SIRPα in developing kidneys, in kidneys from CNS patients and in proteinuric rat models. The possibility that SIRPα interacts with known SD proteins was also investigated. SIRPα was concentrated at the SD junction during the maturation of intercellular junctions. In the glomeruli of CNS patients carrying mutations in NPHS1, where SD formation is disrupted, the expression of SIRPα as well as Neph1 and nephrin was significantly decreased, indicating that SIRPα is closely associated with the nephrin complex. Indeed, SIRPα formed hetero-oligomers with nephrin in cultured cells and in glomeruli. Furthermore, the cytoplasmic domain of SIRPα was highly phosphorylated in normal glomeruli, and its phosphorylation was dramatically decreased upon podocyte injury in vivo. Thus, SIRPα interacts with nephrin at the SD, and its phosphorylation is dynamically regulated in proteinuric states. Our data provide new molecular insights into the phosphorylation events triggered by podocyte injury.

Mutations in podocyte genes are a rare cause of primary FSGS associated with ESRD in adult patients

Several genes have been identified to be causative for the disease in a subset of patients with focal segmental glomerulosclerosis (FSGS) and nephrotic syndrome (NS). Mutations in genes with autosomal dominant inheritance mostly affect adolescent or adult patients. In rare cases recessive mutations in NPHS2 are associated with late-onset FSGS. Hereditary FSGS is associated with poor renal survival and low rates of disease recurrence after renal transplantation. Aim of the study was to evaluate the incidence of gene mutations within a cohort of adult patients with primary FSGS and/or NS and progression to end-stage renal disease (ESRD). Genotyping for TRPC6, ACTN4, CD2AP, WT1, INF2, NPHS2 and NPHS1 was performed in all patients with primary FSGS and ESRD registered on the waiting list for kidney transplantation of a large German transplant center (n = 26 out of 478 registered patients). Mean age at onset was 31.7 years; a positive family history for renal disease was documented in 11 (42%) patients, of these one with familiar history of FSGS. A missense mutation (p.R360H) was identified in TRPC6, 2 missense mutations in compound heterozygous state in NPHS1 (p.P368L; p.G412C), a sequence variation of unknown significance (p.R310Q) in ACTN4 and the non-neutral NPHS2 polymorphism p.R229Q in two additional patients. No mutations were detected in INF2, CD2AP and WT1. The observed mutation rate was 8% in this single-center cohort of adult patients with primary FSGS. Mutations in podocyte genes seem to be a rare cause of FSGS and renal failure in adult patients. However, they should be considered as the underlying cause in a subset of patient as the impact on family counseling and patients' life perspectives are significant.

Mutation Analysis of NPHS1 in a Worldwide Cohort of Congenital Nephrotic Syndrome Patients

Background: Congenital nephrotic syndrome (CNS) is defined as nephrotic syndrome that manifests within the first 3 months of life. Mutations in the NPHS1 gene encoding nephrin, are a major cause for CNS. Currently, more than 173 different mutations of NPHS1 have been published as causing CNS, affecting most exons. Methods: We performed mutation analysis of NPHS1 in a worldwide cohort of 20 families (23 children) with CNS. All 29 exons of the NPHS1 gene were examined using direct sequencing. New mutations were confirmed by demonstrating their absence in 96 healthy control individuals. Results: We detected disease-causing mutations in 9 of 20 families (45%). Seven of the families showed a homozygous mutation, while two were compound heterozygous. In another 2 families, single heterozygous NPHS1 mutations were detected. Out of 10 different mutations discovered, 3 were novel, consisting of 1 splice site mutation and 2 missense mutations. Conclusion: Our data demonstrate that the spectrum of NPHS1 mutations is still expanding, involving new exons, in patients from a diverse ethnic background.

A spectrum of novel NPHS1 and NPHS2 gene mutations in pediatric nephrotic syndrome patients from Pakistan

BackgroundMutations in the NPHS1 and NPHS2 genes are among the main causes of early-onset and familial steroid resistant nephrotic syndrome respectively. This study was carried out to assess the frequencies of mutations in these two genes in a cohort of Pakistani pediatric NS patients. MethodsMutation analysis was carried out by direct sequencing of the NPHS1 and NPHS2 genes in 145 nephrotic syndrome (NS) patients. This cohort included 36 samples of congenital or infantile onset NS cases and 39 samples of familial cases obtained from 30 families. ResultsA total of 7 homozygous (6 novel) mutations were found in the NPHS1 gene and 4 homozygous mutations in the NPHS2 gene. All mutations in the NPHS1 gene were found in the early onset cases. Of these, one patient has a family history of NS. Homozygous p.R229Q mutation in the NPHS2 gene was found in two children with childhood-onset NS. ConclusionsOur results show a low prevalence of disease causing mutations in the NPHS1 (22% early onset, 5.5% overall) and NPHS2 (3.3% early onset and 3.4% overall) genes in the Pakistani NS children as compared to the European populations. In contrast to the high frequency of the NPHS2 gene mutations reported for familial SRNS in Europe, no mutation was found in the familial Pakistani cases. To our knowledge, this is the first comprehensive screening of the NPHS1 and NPHS2 gene mutations in sporadic and familial NS cases from South Asia.

Mutations in NPHS1 in a Chinese child with congenital nephrotic syndrome

Since the identification of the NPHS1 gene, which encodes nephrin, various investigators have demonstrated that the NPHS1 mutation is a frequent cause of congenital nephrotic syndrome (CNS); it is found in 98% of Finnish children with this syndrome and in 39-80% of non-Finnish cases. In China, compound heterozygous mutations in the NPHS1 gene have been identified in two Chinese families with CNS. To our knowledge, however, whether or not NPHS1 is the causative gene in sporadic Chinese CNS cases has not been established. We identified a homozygous mutation of NPHS1, 3250insG (V1084fsX1095), in a Chinese child with sporadic CNS. This finding leads us to suggest that NPHS1 mutations are also present in sporadic Chinese CNS cases. This gives additional support for the necessity for genetic examination of mutations in the NPHS1 gene in Chinese children with sporadic CNS.

NPHS2 mutations in Indian children with sporadic early steroid resistant nephrotic syndrome

We examined the frequency and spectrum of podocin NPHS2 mutations in Indian children with sporadic steroid resistant nephrotic syndrome (SRNS). Of 25 children screened, only one (4%) had a pathogenic mutation resulting in a stop codon. The allele and genotype frequencies of the four known single nucleotide polymorphisms detected in the cohort were similar to that of controls. This finding emphasizes the need to screen for mutations in other genes involved in the pathogenesis of SRNS.

Infant with gross hematuria and nephrotic syndrome: answers

Our differential diagnosis was acute glomerulonephritis due to infections known to cause nephrotic syndrome (NS) in the first year of life, including syphilis, toxoplasmosis, cytomegalovirus (CMV), rubella, hepatitis B, hepatitis C, human immunodeficiency virus (HIV), parvovirus, Epstein-Barr virus (EBV), herpes simplex virus (HSV), hemolytic–uremic syndrome (HUS), autoimmune disease [systemic lupus erythematosus (SLE), vasculitis], malignancy, and primary (genetic) NS with later presentation at 9 months of age (Table 1). Due to severe gross hematuria, NS and decreased renal function on admission, percutaneous renal biopsy was performed on hospital day 1 without complications. Renal ultrasonography with Doppler flow showed no evidence of renal vein thrombosis. Histologic laboratory tests showed complement levels C3 and C4 were within normal limits [120 (85–157) and 27 (15–38) mg/dl respectively], as well as total complement CH50 46 (40–70). All tests for infectious causes were negative, including antibodies to HSV, Rubella, toxoplasmosis, EBV, hepatitis C, HIV, parvovirus; polymerase chain reaction (PCR) for EBV and parvovirus; hepatitis B antigen; rapid plasma reagin test for syphilis; and nasopharyngeal viral culture including adenovirus, influenza A and B, parainfluenza, meta-pneumovirus, and respiratory syncytial virus. Stool culture for Escherichia coli O157 was negative. Serologic tests to look for SLE (antinuclear antibodies, antibodies to double-stranded DNA) and vasculitis (antineutrophil cytoplasmic antibodies) were also negative. A peripheral blood smear was done to evaluate for HUS and malignancy. The smear showed normocytic anemia without red blood cell morphologic abnormalities and no evidence of microangiopathic hemolysis. For possibility of Denys-Drash syndrome (DDS) in an infant with female phenotype, karyotype was tested and showed normal 46 XX female. Genetic testing for gene mutations in PLCE1, LAMB2, WT1, NPHS1, and NPHS2 genes for early-onset NS showed DNA sequence variants in NPHS1 (heterozygous transition G>A, nucleotide position IVS9+8) and WT1 (heterozygous, transition T>C, nucleotide position 844, codon position 282, amino acid change cysteine>arginine), which were of unknown clinical significance and have not been associated with NS (Athena Diagnostics Inc., Worchester, MA, USA). This refers to the article that can be found at http://dx.doi.org/10.1007/ s00467-011-1965-z

Rituximab treatment for recurrence of nephrotic syndrome in a pediatric patient after renal transplantation for congenital nephrotic syndrome of Finnish type

Congenital nephrotic syndrome (CNS) of the Finnish type due to mutation in the NPHS-1 gene results in massive proteinuria due to structural abnormality in the glomerular slit diaphragm, and is usually refractory to immunosuppressive therapy. Patients eventually require bilateral nephrectomy and renal replacement therapy, with transplantation being the ultimate goal. Post-transplant recurrence of nephrotic syndrome occurs in about 25% of children and is thought to be immune-mediated secondary to antibodies formed against the nephrin protein in renal allograft. Conventional therapy with calcineurin inhibitors (CNI), cyclophosphamide and corticosteroids with or without plasmapheresis often fails to achieve remission resulting in graft loss in 12-16%. There is limited experience with use of rituximab (RTX) in pediatric organ transplant recipients. We report the first case of post-transplant recurrence of nephrotic syndrome in a 4-yr-old child with CNS due to NPHS-1 mutation in whom CNI, corticosteroid and cyclophosphamide therapy was unsuccessful, but who achieved remission after depletion of B cells with RTX, associated with a decrease in the level of anti-nephrin antibodies. The child remains in remission 5 yr following treatment. Our experience suggests that activated B cells may play a pivotal role in the recurrence of nephrosis after renal transplantation in children with CNS.

Clinical Utility of Genetic Testing in Children and Adults with Steroid-Resistant Nephrotic Syndrome

The increasing number of podocyte-expressed genes implicated in steroid-resistant nephrotic syndrome (SRNS), the phenotypic variability, and the uncharacterized relative frequency of mutations in these genes in pediatric and adult patients with SRNS complicate their routine genetic analysis. Our aim was to compile the clinical and genetic data of eight podocyte genes analyzed in 110 cases (125 patients) with SRNS (ranging from congenital to adult onset) to provide a genetic testing approach. Mutation analysis was performed by sequencing the NPHS1, NPHS2, TRPC6, CD2AP, PLCE1, INF2, WT1 (exons 8 and 9), and ACTN4 (exons 1 to 10) genes. We identified causing mutations in 34% (37/110) of SRNS patients, representing 67% (16/24) familial and 25% (21/86) sporadic cases. Mutations were detected in 100% of congenital-onset, 57% of infantile-onset, 24 and 36% of early and late childhood-onset, 25% of adolescent-onset, and 14% of adult-onset patients. The most frequently mutated gene was NPHS1 in congenital onset and NPHS2 in the other groups. A partial remission was observed in 7 of 26 mutation carriers treated with immunosuppressive agents and/or angiotensin-converting enzyme inhibitors. Patients with NPHS1 mutations showed a faster progression to ESRD than patients with NPHS2 mutations. None of these mutation carriers relapsed after kidney transplantation. We propose a genetic testing algorithm for SRNS based on the age at onset and the familial/sporadic status. Mutation analysis of specific podocyte-genes has a clinical value in all age groups, especially in children.

Screening for NPHS2 Mutations May Help Predict FSGS Recurrence after Transplantation

Steroid-resistant focal segmental glomerulosclerosis (FSGS) often recurs after renal transplantation. In this international survey, we sought to identify genotype-phenotype correlations of recurrent FSGS. We surveyed 83 patients with childhood-onset primary FSGS who received at least one renal allograft and analyzed 53 of these patients for NPHS2 mutations. The mean age at diagnosis was 6.7 years, and the mean age at first renal transplantation was 13 years. FSGS recurred in 30 patients (36%) after a median of 13 days (range, 1.5 to 152 days). Twenty-three patients received a second kidney transplant, and FSGS recurred in 11 (48%) after a median of 16 days (range, 2.7 to 66 days). None of the 11 patients with homozygous or compound heterozygous NPHS2 mutations developed recurrent FSGS compared with 45% of patients without mutations. These data suggest that genetic testing for pathogenic mutations may be important for prognosis and treatment of FSGS both before and after transplantation.

Two novel NPHS1 mutations in a Chinese family with congenital nephrotic syndrome

Congenital nephrotic syndrome of the Finnish type (CNF) is a lethal, autosomal recessive disorder mainly caused by mutations in the NPHS1 gene; it is found at a relatively high frequency in Finns. We investigated the disease-causing mutations in a Chinese family with CNF and developed a prenatal genetic diagnosis for their latest pregnancy. Mutation analysis was made of all exons and exon/intron boundaries of NPHS1 in the fetus, parents and 50 unrelated controls using PCR and direct sequencing. A heterozygous nonsense mutation within exon 20 (c.2783C>A) and a missense mutation within exon 17 (c.2225T>C) in NPHS1 were detected in the proband's father and mother, respectively, but were not found in the fetus or in 50 unrelated controls. Two novel mutations of c.2783C>A and c.2225T>C in NPHS1 were found to be causative in this Chinese CNF family with no known Finnish ancestry. The most recent sibling did not inherit these two mutations and hence was unaffected with CNF. Determining the cumulative number and ethnic distribution of known mutations can help expedite further study of the pathogenesis of CNF.