A Newly Identified Mutation in the WT1 Gene in Denys-Drash Syndrome

Wilms Tumor

Denys-Drash syndrome (DDS) is characterized by genital anomaly, early onset nephropathy and high risk for developing Wilms' tumor (WT). Recently, mutations in exon 8 or 9 of the Wilms' tumor suppressor gene (WT1) have been found in the majority of DDS patients studied. We analyzed these two exons of the WT1 gene in genomic DNA from two female patients with DDS by using polymerase-chain reaction (PCR) and direct sequencing. The patients were accompanied with normal external genitalia, early onset renal failure between 6 and 12 months of age, and unilateral Wilms' tumor. Genomic DNA was isolated from peripheral blood leucocytes of the patients. Amplification of exons 8 and 9 of the WT1 gene by PCR was performed, and direct sequencing of the PCR product was performed using an automatic DNA sequencer. Two heterozygous missense mutations were found in these patients, including a missense mutation in exon 9 at codon 388 replacing the wild-type Cys with Phe, and a previously described mutation in exon 9 at codon 398 replacing the wild-type Leu with Pro. Cys388Phe is a novel mutation in the WT1 gene in the DDS. These cases are considered to be "incomplete DDS" with nephropathy and Wilms' tumor and without genital anomaly, the validity of which has been confirmed by mutation analysis.

Mutations in the WT1 gene causing Wilms tumors were first reported in WAGR syndrome (Wilms tumor, Aniridia, Genitourinary malformation, mental Retardation) and Denys Drash syndrome (pseudohermaphroditism, Wilms tumor, nephropathy), but only in a few patients with hypospadias and cryptorchidism without other signs of Denys Drash (DDS) or WAGR syndrome WT1 mutations were identified. We report a boy, who was born in 1989 with hypospadias and bilateral cryptorchidism. Previous karyotyping and endocrine studies had ruled out any known cause of male pseudohermaphroditism. Subsequently, he developed a bilateral Wilms tumor, which was detected by palpation at the age of 15 months during a routine visit by the general pediatrician. Because of its extensive size, surgery and chemotherapy were needed for treatment. Analysis of the WT1 gene was performed 5 y after diagnosis and revealed a C to T transition in one allele generating a stop codon at codon 362 and subsequently leading to a truncated protein with loss of its ability to bind to DNA. No signs of DDS or WAGR syndrome are present in the boy. The work up of this patient and the so far known few comparable cases from the literature lead to the conclusion that in newborns with severe urogenital malformations not due to known chromosomal or endocrine disorders mutational screening of the WT1 gene should be performed, to evaluate the high risk of developing a Wilms tumor. We favor mutational screening in these patients as an easy tool for investigation, because in the future it will probably decrease the necessity of frequent control visits in patients without a WT1 mutation.

Background and Aims The Wilms tumor suppressor gene 1 (WT1) (MIM 607102) has an important role in renal and gonadal development. WT1 mutations was found to be associated with a large spectrum of phenotypes with autosomal-dominant inheritance, including Wilms tumor, Denys-Drash syndrome (DDS), Frasier syndrome (FS), and isolated steroid-resistant nephrotic syndrome (SRNS). The aim of the study was to investigate clinical and molecular characteristics in children with WT1-associated SRNS. Method Retrospective analysis of phenotype and genotype of six children (3M/3F) with SRNS and heterozygous WT1 mutations was performed. Karyotypes were available in all patients. Data on renal histology had three subjects with FS. The median follow-up period was 35.5 (IQR: 20.0; 57.5) months. WT1 mutations identified by direct Sanger sequencing (n=3) and next generation sequencing (n=3). Results The median age at onset of WT1-associated SRNS was 10.0 (IQR: 5.5; 22.5) months. 4/6 (66.7%) patients presented with infantile nephrotic syndrome and 2/6 (33.3%) with SRNS. Arterial hypertension was determined in 4/6 (66.7%) of individuals. Among children with WT1-associated SRNS 3/6 (50%) patients had DDS (2M/1F) and 3/6 (50%) subjects had FS (1M/2F). Children with DDS had Wilms tumor in 2/3 (66.7%) of cases and gonadal dysgenesis with hypospadias in 1/3 (33.3%) of children. Causative mutations were identified in all three patients with DDS, including 2 earlier described c.1384C>T in exon 9 and c.1098 + 1G>A in intron 6 in WT1 gene, and one novel mutation с.1378Т>G in exon 9. All DDS children had decreased eGFR to CKD stage 2-3 in two patients aged 7 and 11 years and ESKD in one child at the age of 2 years. All 3 patients with FS had focal segmental glomerulosclerosis on biopsy. Two phenotypic girls with FS had karyotype 46, XY and presented with pseudohermaphroditism. The same earlier described splice site mutation c.1432 + 5G>A in intron 9 in WT1 gene was identified in both cases. One boy with FS had typical male chromosome pattern (46, XY) and gonadal dysgenesis. Splice site mutation c.1432 + 4C>T in intron 9 in WT1 gene was found in the child. Nobody of patients with FS developed gonadoblastoma. Progression to CKD was found in all three cases with FS, including CKD stage 2-3 in two subjects aged 5 and 15 years and ESKD in one phenotypically girl with sex reversal developed at the age of 8 years. Conclusion We found that children with WT1-associated SRNS had a wide spectrum of renal and extrarenal phenotypes concerning the development of urogenital system and Wilms tumor with high risk of progression to CKD during childhood. Their phenotypes are clearly associated with the type and location of WT1 mutations led to DDS or FS. Genetic WT1 diagnostics is important in all children with SRNS for early detection, optimal treatment, tumor prevention and prognosis.

Wilms Tumor

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).

ObjectiveDenys‐Drash syndrome (DDS) is defined by the triad of Wilms tumor, nephrotic syndrome, and/or ambiguous genitalia. Genetic testing may help identify new gene mutation sites and play an important role in clinical decision‐making.MethodsWe present a patient with an XY karyotype and female appearance, nephropathy, and Wilms tumor in the right kidney. Genomic DNA was extracted from peripheral blood cells according to standard protocols. “Next‐generation” sequencing (NGS) was performed to identify novel variants. The variant was analyzed with Mutation Taster, and its function was explored by a cell growth inhibition assay.ResultsWe found the first case of Denys‐Drash syndrome with the uncommon missense mutation (c.1420C>T, p.His474 Tyr) in the WT1 gene. In silico analysis, the variant was predicted “disease‐causing” by Mutation Taster. The mutated variant showed a weaker effect in inhibiting tumor cells than wild‐type WT1.ConclusionsThe uncommon missense mutation (c.1420C>T, p.His474 Tyr) in the WT1 gene may be a crucial marker in DDS.

Denys-Drash syndrome is a rare genetic disorder featuring the triad of congenital nephropathy, Wilms tumor, and intersex disorders (XY under-virilization or XY female). Denys-Drash syndrome is associated with constitutional mutations in the Wilms tumor suppressor gene WT1. Unlike WAGR (Wilms tumor, aniridia, genitourinary anomalies, and mental retardation) syndrome, with its complete deletion of one copy of WT1, Denys-Drash syndrome is generally caused by a dominant-negative mutation. We present a new case of Denys-Drash syndrome in a patient initially diagnosed with XY ambiguous genitalia/partial androgen insensitivity syndrome, who was found to have a novel nonsense mutation in exon 6 leading to a stop codon and hence a truncated protein. Based on lessons learned from this patient, the diagnosis of Denys-Drash syndrome should be considered in the presence of ambiguous genitalia and partial androgen insensitivity.

Denys-Drash syndrome (DDS) is a rare disorder characterized by nephropathy, male pseudohermaphroditism, and wilms tumor. Cases are thought to arise sporadically through a de novo mutation in the wilms tumor suppressor gene (WT1), which encodes a zinc finger protein that not only acts as a tumor suppressor but is essential for normal gonadogenesis, nephrogenesis, and development of the urogenital tract. In this report, we describe a family with the well-known missense mutation in exon 9 of the WT1 gene, 1180C>T (R394W), causing incomplete DDS and no symptoms in their father. The proband, a boy with 46, XY karyotype, was born with ambiguous genitalia, penoscrotal hypospadias, and bilateral inguinal hernias. At 2 years of age, he has proteinuria and diffuse mesangial sclerosis, but no wilms tumor has been detected. The elder sister of the proband, at 3 years of age, has normal genitalia, proteinuria, focal mesangial sclerosis but no wilms tumor. The WT1 mutation was detected in both patients, who have suspected DDS, and their father, who is phenotypically normal. This case is unusual in that the 1180C>T mutation, which has been found in approximately 50 % of patients with complete DDS, has been inherited and is causing mild or no symptoms of DDS.

WT1 mutations have been described in a variety of syndromes, including Denys-Drash syndrome (DDS), which is characterized by predisposition to Wilms' tumor, genital abnormalities and development of early nephropathy. The most frequent WT1 defects in DDS are missense mutations located in exons 8-9. Our aim is to report a novel WT1 mutation in a 46,XY patient with a DDS variant, who presented a mild nephropathy with a late onset diagnosed during adolescence. He had ambiguous genitalia at birth. At 4 months of age he underwent nephrectomy (Wilms' tumor) followed by chemotherapy. Ambiguous genitalia were corrected and bilateral gonadectomy was performed. Sequencing of WT1 identified a novel heterozygous mutation (c.742A>T) in exon 4 that generates a premature stop codon (p.K248X). Interestingly, this patient has an unusual DDS nephropathy progression, which reinforces that patients carrying WT1 mutations should have the renal function carefully monitored due to the possibility of late-onset nephropathy.

Rationale:Pediatric patients with WTl-associated syndromes (including Wilms’ tumor-aniridia syndrome and Denys-Drash syndrome), Perlman syndrome, mosaic aneuploidy, and Fanconi anemia with a biallelic breast cancer type 2 susceptibility protein mutation have the highest risk of developing Wilms’ tumor.Patient concerns and diagnosis:We describe a patient with bilateral metachronous Wilms’ tumor, ambiguous genitalia characterized by 46, XY disorder of sexual development (DSD) with scrotal hypospadias and bilateral abdominal cryptorchidism, but without nephropathy. At the age of 7 months, the child underwent left nephrectomy with left orchiopexy. At follow-up after 8 months, a second tumor with a diameter of 10 mm was detected in abdominal CT scans at the lower pole of the right kidney.Intervention:Intra-operative macroscopic inspection of the right kidney revealed a tight attachment of the right proximal ureter to the tumor. Thus, retroperitoneoscopic resection of the lower pole of the right kidney had to be changed to an open surgical procedure with partial resection of the proximal ureter and high uretero-ureterostomy. We subsequently performed orchiopexy and two-stage correction of hypospadias using a free skin graft.Outcomes:At the last follow-up at the age of 8 years, no pathology requiring treatment was noted. A pair-end-reading (2 × 125) DNA analysis with an average coverage of at least 70 to 100 × revealed a previously unknown heterozygous mutation in exon 7 of the Wilms’ tumor suppressor gene 1 (WT1) gene (chr11:32417947G>A), leading to the appearance of a site of premature translation termination in codon 369 (p.Arg369Ter, NM_024426.4). This mutation had not been registered previously in the control samples “1000 genomes,” Exome Sequencing Project 6500, and the Exome Aggregation Consortium. Thus, to the best of our knowledge this represents a newly identified mutation causing incomplete Denys-Drash syndrome.

Denys-Drash syndrome (DDS) is characterized by early onset nephropathy, pseudohermaphroditism in males and a high risk for developing Wilm's tumour (WT). The exact cause of DDS is unknown but germline mutations in the Wilm's tumour suppressor gene (WT1) have recently been described in the majority of DDS patients studied. These mutations occur de novo and are clustered around the zinc finger (ZF) coding exons of the WT1 gene. Analysis of exons 2-10 of the WT1 gene in constitutional DNA from five patients with DDS was carried out using the polymerase chain reaction (PCR) and direct DNA sequencing. In four out of the five patients, heterozygous germline mutations were found: a novel point mutation in exon 8 (ZF2) at codon 377 altering the wild-type histidine to arginine, and three previously described point mutations in exon 9 (ZF3) in the codons corresponding to amino acids 394Arg and 396Asp. In one patient, no mutations could be demonstrated. In three patients where parental DNA was available, the mutations were shown to have occurred de novo. Furthermore, since tumour DNA in two of these cases had lost the wild-type allele, polymorphic markers from the short arm of chromosome 11 were used to determine the parental origin of the mutant chromosome. In both cases, the mutant chromosome was shown to be of paternal origin. Since the majority of published WT1 mutations in DDS patients alter a RsrII restriction site in exon 9, we were able to perform PCR-based diagnosis in a female patient with early renal insufficiency and normal external genitalia.

Background: Denys-Drash syndrome (DDS) is a very rare genetic disease. Wilms' tumor, genital abnormalities, and congenital glomerulopathy are the main features of DDS which resulted from a heterozygous mutation in the WT1 gene. Case Presentation: First case of DDS has been diagnosed in Saudi Arabia in four months newborn who admitted to nephrology department with ambiguous bilateral undescended testis, and nephropathy. On admission, he had normal vital signs except high blood pressure. His kidney function tests showed abnormal kidney function. Ultrasonography and MRI were done to figure out his nephropathy and undescended testis, respectively. Both Abdominal ultrasonography and kidney histopathology confirmed diffuse mesangial sclerosis (DMS). MRI graph located the un-identical ectopic testis. The autosomal dominant inherited pathogenic missense mutation in exon 9 of WT1 gene (c.1181G>A (p.Arg394GLu)) was confirmed by DNA direct sequencing analysis. At his 4th year of age, his nephropathy developed to End Stage Renal Disease (ESRD). Conclusion: DDS should be considered in new born baby with nephrotic syndrome and ambiguous gonads. DNA direct sequencing analysis for WT1 gene is very helpful for confirmation of DDS.

Several lines of evidence suggest that the Wilms's tumour susceptibility gene, WT1, has an important role in genital as well as kidney development. WT1 is expressed in developing kidney and genital tissues. Furthermore, mutations in WT1 have been detected in patients with the Denys-Drash syndrome (DDS), which is characterised by nephropathy, genital abnormalities, and Wilms's tumour. It is possible that WT1 mutations may cause genital abnormalities in the absence of kidney dysfunction. We tested this hypothesis by screening the WT1 gene for mutation in 12 46,XY patients with various forms of genital abnormality. Using single strand conformation polymorphism (SSCP) we did not detect any WT1 mutations in these patients. However, in addition to the 12 patients, three DDS patients were also analysed using SSCP, and in all three cases heterozygous WT1 mutations were found which would be predicted to disrupt the DNA binding activity of WT1 protein. These results support the notion that DDS results from a dominant WT1 mutation. However, WT1 mutations are unlikely to be a common cause of male genital abnormalities when these are not associated with kidney abnormalities.

While a genetic basis for the association of developmental lung and kidney defects has been suspected, the involvement of specific genes in this process is under active investigation. We report such a possible genetic linkage present in identical twins with a mutant Wilms tumor (WT1) gene. Twin girls, born at 35 weeks gestation, manifested symptoms of congenital nephrotic syndrome, renal failure, and severe respiratory abnormalities refractory to assisted ventilation. Both died at 1 month of age. Renal biopsies and autopsy kidney tissue from both the girls revealed diffuse mesangial sclerosis (DMS). Autopsy lung tissue revealed pulmonary dysplasia and hypoplasia in both twins. The WT1 gene from renal tissue in both twins was analyzed for mutations using polymerase chain reaction (PCR) amplification and the single-strand conformation polymorphism (SSCP) technique. Both twins possessed an identical missense mutation in exon 8 of the WT1 gene, resulting in replacement of arginine by histidine at amino acid 366 (arg366his) in the WTI protein. This mutation has previously been described in Denys-Drash syndrome. The WT1 gene plays a role in mesenchymal epithelial (ME) interactions in the developing urogenital system, and possibly has a similar role during lung morphogenesis. We propose that this WT1 gene mutation contributes to both DMS and developmental pulmonary abnormalities by altering ME interactions in both organs.