Three Novel Mutations in the NPHS1 Gene in Vietnamese Patients with Congenital Nephrotic Syndrome

A novel heterozygous mutation of the NPHS1 gene in a Chinese child with congenital nephrotic syndrome: A case report

RATIONALE

Congenital nephrotic syndrome (CNS) is a heterogeneous disorder in which massive proteinuria, hypoproteinemia, and hyperlipidemia and marked edema are the main manifestations before 3 months-of-age. Here, we present a case involving the genetic diagnosis of a child with CNS.

PATIENT CONCERNS

A 31-day-old male infant with diarrhea for 25 days and generalized edema for more than 10 days. There was no family history of kidney disease. On proband whole exome sequencing, a compound heterozygous mutation of the NPHS1 gene was identified, including a novel in-frame mutation in exon 14 (c.1864_1866dupACC p. T622dup) and a missense mutation in exon 8 (c.928G>A p. D310N).

DIAGNOSES

Based on the clinical and genetic findings, this patient was finally diagnosed with CNS.

INTERVENTIONS

The main treatment options for the patient were 2-fold: anti-infective treatment and symptomatic treatment.

OUTCOMES

The patient died in follow-up 2 months later; the specific reason for death was unclear.

LESSONS

Whole exome sequencing and Sanger sequencing confirmed that the infant had CNS. Our study identified a novel mutation in an infant, thus expanding the gene-mutation spectrum of the NPHS1 gene, thus providing an efficient prenatal screening strategy and early genetic counseling.

Identification of NPHS1 Genetic Variations in Cohort of Egyptian Patients with Congenital Nephrotic Syndrome

Introduction: Autosomal recessive variations in NPHS1 gene represent common cause of congenital nephrotic syndrome (CNS). The disease is characterized by considerable proteinuria presenting in the first 90days of life. CNS has a poor outcome and usually leads to end stage renal disease by 2-3 years of life.   NPHS1 encodes the protein nephrin, expressed in inter-podocyte slit diaphragm. Aim of work: The main objective of this cross-sectional study was to perform the analysis of the NPHS1 gene in 24 Egyptian patients with CNS aiming to determine the molecular cause of the disease and to detect their phenotype/genotype correlations. Methods: Polymerase chain reaction followed by direct sequencing of exons (3,4,6,7,18,19) of NPHS1 gene was performed in 24 neonates with CNS with median age 25 days (1-90 day). Results:  three pathogenic variants were detected in five patients. They were one frame shift variant in exon 19, one missense de novo variant in exon 6 and one In-frame deletion variant in exon 4. Three benign variants were seen in seven patients in exon and intron 3. Conclusion: although the number of patient included in the study is small, but the results of the study presented de novo likely pathogenic mutation in exon 6 not reported before in 2 patients and 2 reported pathogenic variants. Molecular diagnosis is advised to be performed early in the diagnosis of CNS to avoid unnecessary immunesupp-ression and start early suitable treatment.

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.