Two cases of isolated diffuse mesangial sclerosis with WT1 mutations

Detailed clinical manifestations at onset and prognosis of neonatal-onset Denys-Drash syndrome and congenital nephrotic syndrome of the Finnish type

BACKGROUND

Neonatal-onset Denys-Drash syndrome (NODDS) is a distinctive clinical entity and has a poor renal and life outcome. Early diagnosis of NODDS is important for managing disorders of sexual development and determining assigned gender. Although patients with NODDS and congenital nephrotic syndrome of the Finnish type (CNF) present with nephrotic syndrome in neonatal life or infancy, the clinical course of NODDS and factors distinguishing these diseases at onset is unknown.

METHODS

We performed a retrospective cohort study of patients with NODDS and CNF between 1997 and 2017. Patients with nephrotic syndrome and WT1 or NPHS1 mutations with neonatal onset (within 30 days) were eligible.

RESULTS

We studied eight patients with NODDS and 15 with CNF. The median serum creatinine level at onset in the NODDS group was significantly higher (1.85 mg/dL) than that in the CNF group (0.15 mg/dL; P = 0.002). The median placental/fetal weight ratio in the NODDS and CNF group was 41.8% and 21.0%, respectively (P = 0.001). Kaplan-Meier analysis showed that the median number of days for progression to ESRD from onset in the NODDS and CNF groups was 6 and 910 days, respectively (P < 0.001). All patients in the NODDS group were alive at follow-up. Only one patient in the CNF group died of cardiac complications during follow-up.

CONCLUSION

CNS, renal dysfunction at onset, and a relatively large placenta are prominent signs of NODDS. Prognosis for patients with NODDS is satisfactory if appropriate and active management is performed.

Clinical Aspects of WT1 and the Kidney

For more than 30 years, WT1 mutations have been associated with complex developmental syndromes involving the kidney. Acting as a transcription factor, WT1 is expressed throughout the nephron and controls the reciprocal interactions and phenotypic changes required for normal renal development. In the adult, WT1 expression remains extremely high in the renal podocyte, and at a lower level in the parietal epithelial cells. Wt1-null mice are unable to form kidneys [1]. Unsurprisingly, WT1 mutations lead to significant abnormalities of the renal and genitourinary tract, causing a number of human diseases including syndromes such as Denys-Drash syndrome, Frasier syndrome, and WAGR syndrome. Recent methodological advances have improved the identification of WT1 mutations, highlighting its importance even in nonsyndromic renal disease, particularly in steroid-resistant nephrotic syndrome. This vast spectrum of WT1-related disease typifies the varied and complex activity of WT1 in development, disease, and tissue maintenance.

Genotype-phenotype analysis of pediatric patients with WT1 glomerulopathy

BACKGROUND

WT1 is one of the genes commonly reported as mutated in children with steroid-resistant nephrotic syndrome (SRNS). We analyzed genotype-phenotype correlations in pediatric SRNS patients with WT1 mutations.

METHODS

From 2001 to 2015, WT1 mutations were detected in 21 out of 354 children with SRNS by genetic screening (5.9 %). The patients were grouped into missense (n = 11) and KTS splicing (n = 10) mutation groups.

RESULTS

Nine (82 %) patients with missense mutations presented with congenital/infantile nephrotic syndrome, while 8 (80 %) with KTS splicing mutations presented with childhood-onset SRNS. Progression to end-stage renal disease (ESRD) was noted in all patients with missense mutations (median age, 2.6 months; interquartile range [IQR], 0.8 months to 1.7 years) and in 5 patients with KTS splicing mutations (median, 9.3 years; IQR, 3.3-16.5 years). Disorders of sexual development (DSDs) were noted in all 12 patients with a 46, XY karyotype and in only 1 of the 8 patients with a 46, XX karyotype. One patient developed a Wilms tumor and another developed gonadoblastoma. Three patients had a diaphragmatic defect or hernia.

CONCLUSIONS

WT1 mutations manifest as a wide spectrum of renal and extra-renal phenotypes. Genetic diagnosis is essential for overall management and to predict the genotype-specific risk of DSDs and the development of malignancies.

Recent findings on the genetics of disorders of sex development

PURPOSE OF REVIEW

Disorders of sex development (DSD) are a diverse group of conditions affecting gonadal development, sexual differentiation, or chromosomal sex. In this review, we will discuss recent literature on the genetic causes of DSD, with a focus on novel genetic sequencing technologies, new phenotypes associated with known DSD genes, and increasing recognition of the role of genetic regulatory elements in DSD.

RECENT FINDINGS

We performed a comprehensive search of PubMed through August 2016 to identify important peer-reviewed publications from 2015 to 2016 on the topic of DSD genetics.

SUMMARY

Whole-exome sequencing was used to successfully identify genetic causes of DSD in 35% of a cohort of 46,XY patients who had not previously received a genetic diagnosis. A novel mutation in NR5A1 has been identified as a cause of 46,XX testicular and ovotesticular DSD, demonstrating a previously unappreciated role of NR5A1 in preventing testicular differentiation in 46,XX individuals. Genetic regulatory elements of SOX9 have been identified as causes of 46,XX and 46,XY DSD.

Refining the Diagnosis of Congenital Nephrotic Syndrome on Long-term Stored Tissue: c.1097G>A (p.(Arg366His)) WT1 Mutation Causing Denys Drash Syndrome

Congenital nephrotic syndrome (CNS) caused by a mutation in the Wilms tumor 1 suppressor gene (WT1) is part of Denys Drash Syndrome or Frasier syndrome. In the framework of genetic counseling, the diagnosis of CNS can be refined with gene mutation studies on long-term stored formalin-fixed paraffin-embedded tissue from postmortem examination. We report a case of diffuse mesangial sclerosis with perinatal death caused by a de novo mutation in the WT1 gene in a girl with an XY-genotype. This is the first case of Denys Drash Syndrome with the uncommon missense c.1097G>A [p.(Arg366His)] mutation in the WT1 gene which has been diagnosed on long-term stored formalin-fixed paraffin-embedded tissue in 1993. This emphasizes the importance of retained and adequately stored tissue as a resource in the ongoing medical care and counseling.

Atypical clinical presentation of a WT1-related syndrome associated with a novel exon 6 gene mutation

Wilms' tumour suppressor gene-1 (WT1) plays a critical role in kidney development and function. Several WT1 mutations can occur in exons 7, 8 and 9 and they have been associated with Denys-Drash syndrome. WT1 mutations of intron 9 have been reported too and associated with Frasier syndrome. However, overlapping and incomplete forms of both the syndromes have been described. We report a novel sequence variant (c.1012A>T) of the WT1 gene in exon 6 (p.R338X) in a 18-year-old girl with a history of Wilms' tumour, minor gonadal changes and relatively late-onset nephropathy. WT1-related nephropathies should be suspected in every patient with proteinuria not associated to immunological changes when a congenital neoplasia or minor gonadal anomalies are present.

A novel WT1 gene mutation in a patient with Wilms' tumor and 46, XY gonadal dysgenesis

Denys-Drash syndrome (DDS) is a rare genetic disorder featuring the triad of Wilms' tumor, early-onset renal failure, and 46, XY disorder of sex development. DDS is usually caused by heterozygous missense mutations in the zinc-finger region of the WT1 gene. The most frequent constitutional WT1 mutations in DDS patients are missense mutations in exons 8 and 9. We present a new case of variable DDS in a child who was found to have a novel heterozygous missense mutation in exon 7 (c.905G>T) and a splicing mutation in exon 6 (IVS6-1G>T).

Hereditary nephrotic syndrome: a systematic approach for genetic testing and a review of associated podocyte gene mutations

Several genes have been implicated in genetic forms of nephrotic syndrome occurring in children. It is now known that the phenotypes associated with mutations in these genes display significant variability, rendering genetic testing and counselling a more complex task. This review will focus on the recent clinical findings associated with those genes known to be involved in isolated steroid-resistant nephrotic syndrome in children and, thereby, propose an approach for appropriate mutational screening. The recurrence of proteinuria after transplantation in patients with hereditary forms of nephrotic syndrome will also be discussed.

Genetics of kidney development: pathogenesis of renal anomalies

Congenital anomalies of the kidney and urinary tract (CAKUT) account for more than 50% of abdominal masses found in neonates and involve about 0.5% of all pregnancies. CAKUT has a major role in renal failure, and increasing evidence suggests that certain abnormalities predispose to the development of hypertension and cardiovascular disease in adulthood. To understand the pathogenesis of human renal anomalies, understanding the development of kidney is important. Diverse anomalies of the kidney corresponding to defects at a particular stage of development have been documented recently; however, more research is required to understand the molecular networks underlying kidney development, and such an investigation will provide a clue to the therapeutic intervention for CAKUT.

A novel WT1 gene mutation in a three-generation family with progressive isolated focal segmental glomerulosclerosis

BACKGROUND AND OBJECTIVES

Wilms tumor-suppressor gene-1 (WT1) plays a key role in kidney development and function. WT1 mutations usually occur in exons 8 and 9 and are associated with Denys-Drash, or in intron 9 and are associated with Frasier syndrome. However, overlapping clinical and molecular features have been reported. Few familial cases have been described, with intrafamilial variability. Sporadic cases of WT1 mutations in isolated diffuse mesangial sclerosis or focal segmental glomerulosclerosis have also been reported.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Molecular analysis of WT1 exons 8 and 9 was carried out in five members on three generations of a family with late-onset isolated proteinuria. The effect of the detected amino acid substitution on WT1 protein's structure was studied by bioinformatics tools.

RESULTS

Three family members reached end-stage renal disease in full adulthood. None had genital abnormalities or Wilms tumor. Histologic analysis in two subjects revealed focal segmental glomerulosclerosis. The novel sequence variant c.1208G>A in WT1 exon 9 was identified in all of the affected members of the family.

CONCLUSIONS

The lack of Wilms tumor or other related phenotypes suggests the expansion of WT1 gene analysis in patients with focal segmental glomerulosclerosis, regardless of age or presence of typical Denys-Drash or Frasier syndrome clinical features. Structural analysis of the mutated protein revealed that the mutation hampers zinc finger-DNA interactions, impairing target gene transcription. This finding opens up new issues about WT1 function in the maintenance of the complex gene network that regulates normal podocyte function.

Evolutive study of children with diffuse mesangial sclerosis

Diffuse mesangial sclerosis (DMS) is a renal disease that usually presents as a nephrotic syndrome. It is characterized by early onset and rapid progression to end-stage renal disease, and can occur as an isolated finding or as part of the Denys-Drash syndrome. The aim of this study was to characterize clinical features and outcomes of DMS in a cohort of children. We retrospectively analyzed all cases of DMS diagnosed in our hospital between 1973 and 2008 and evaluated the progression of the disease in relation to different variables. We studied 14 patients, four with incomplete Denys-Drash syndrome and one with Frasier syndrome. All patients developed renal failure. Eight patients received a renal transplant with no relapse of the disease. Bilateral nephrectomy was performed in nine patients with end-stage renal disease. Seven patients died, with sepsis being the main cause of death. Diffuse mesangial sclerosis must be suspected in a child that presents with early onset proteinuria and/or rapidly progressive renal failure. Karyotype and WT1 gene analysis should be performed because of the predisposition of patients to develop different types of tumors. This nephropathy has a poor prognosis, but the survival rate has improved in the last decade.

WT1 and NPHS2 mutations in Korean children with steroid-resistant nephrotic syndrome

Although several genetic causes of steroid-resistant nephrotic syndrome (SRNS) have been identified, occurrence of these genetic abnormalities appears to be influenced by race. Seventy Korean children (39 girls, 31 boys) with SRNS underwent analysis for mutations of WT1 and NPHS2. Although NPHS2 mutations were not present in any of the patients, two different intronic mutations of WT1, IVS9+4 C>T and IVS9+5 G>A, were detected in four patients (three girls, one boy). Among the four patients with mutation, two girls with a karyotype of 46,XY had complete XY gonadal dysgenesis, one girl with a karyotype of 46,XX had normal genitalia, and one boy with a karyotype of 46,XY had hypospadia. A kidney biopsy conducted in three of the four patients revealed focal segmental glomerulosclerosis. The incidence of WT1 mutations observed in this study was similar to that of previous reports. However, the incidence of NPHS2 mutations seems to be very rare in Korean children. Genetic diagnosis of WT1 mutations should be recommended for children with SRNS, especially in cases involving a female phenotype or males with genital anomalies.

WT1 and glomerular diseases

The WT1 gene encodes a zinc finger transcription factor involved in kidney and gonadal development and, when mutated, in the occurrence of kidney tumor and glomerular diseases. Patients with Denys-Drash syndrome present with early nephrotic syndrome with diffuse mesangial sclerosis progressing rapidly to end-stage renal failure, male pseudohermaphroditism, and Wilms' tumor. Incomplete forms of the syndrome have been described. Germline WT1 missense mutations located in exons 8 or 9 coding for zinc fingers 2 or 3 have been detected in nearly all patients with Denys-Drash syndrome and in some patients with isolated diffuse mesangial sclerosis. Patients with Frasier syndrome present with normal female external genitalia, streak gonads, XY karyotype and progressive nephropathy with proteinuria and nephrotic syndrome with focal and segmental glomerular sclerosis progressing to end-stage renal disease in adolescence or young adulthood. They frequently develop gonadoblastoma. Germline intronic mutations leading to the loss of the +KTS isoforms have been observed in all patients with Frasier syndrome. The same mutations have been observed in genetically female patients with isolated FSGS. Transmission of the mutation is possible. Frasier mutations have also been reported in children with Denys-Drash syndrome.