Wilms' tumor suppressor gene mutations in girls with sporadic isolated steroid-resistant nephrotic syndrome

Spectrum of Clinical Manifestations in Children With WT1 Mutation: Case Series and Literature Review

BACKGROUND

Mutations of the Wilms tumor suppressor-1 gene (WT1) are associated with life-threatening glomerulopathy, disorders of sexual development, Wilm's tumor, and gonadal malignancies. Our objectives were to describe the clinical presentations, age of progression, and onset of complications of WT1 mutation through a case series and literature review.

METHODS

A retrospective study included all patients followed at the University of Miami/Holtz Children's Hospital from January 2000 to December 2020 with a diagnosis of WT1 mutation. A literature review of WT1 mutation cases was analyzed for clinical manifestations, karyotype, and long-term outcomes.

RESULTS

The WT1 mutation was identified in 9 children, median age at presentation of 0.9 years (range 1 week to 7 years). A total of four had female phenotypes, and 5 had abnormalities of male external genitalia, while all had XY karyotypes. All progressed to end-stage kidney disease (ESKD) and received a kidney transplant at a median age of 5 years (1.5-15 years). During a median time of follow-up of 9 years (range 2-28 years), there were 2 allograft losses after 7 and 10 years and no evidence of post-transplant malignancy. From 333 cases identified from the literature review, the majority had female phenotype 66% (219/333), but the predominant karyotype was XY (55%, 183/333). Of the female phenotypes, 32% (69/219) had XY sex reversal. Wilm's tumor occurred in 24%, predominantly in males with gonadal anomalies.

CONCLUSIONS

Early recognition of WT1 mutation is essential for comprehensive surveillance of potential malignancy, avoidance of immunosuppressants for glomerulopathy, and establishing long-term multidisciplinary management.

Systematic Review of Genotype-Phenotype Correlations in Frasier Syndrome

Introduction

Frasier syndrome (FS) is a rare inherited kidney disease caused by intron 9 splicing variants of WT1. For wild-type WT1, 2 active splice donor sites in intron 9 cause a mixture of 2 essential transcripts (with or without lysine-threonine-serine [+/KTS or −KTS]), and imbalance of the +KTS/−KTS ratio results in the development of FS. To date, 6 causative intron 9 variants have been identified; however, detailed transcript analysis has not yet been conducted and the genotype-phenotype correlation also remains to be elucidated.

Methods

We conducted an in vitro minigene splicing assay for 6 reported causative variants and in vivo RNA sequencing to determine the +KTS/−KTS ratio using patients’ samples. We also performed a systematic review of reported FS cases with a description of the renal phenotype.

Results

The in vitro assay revealed that although all mutant alleles produced −KTS transcripts only, the wild-type allele produced both +KTS and −KTS transcripts at a 1:1 ratio. In vivo RNA sequencing showed that patients’ samples with all heterozygous variants produced similar ratios of +KTS to −KTS (1:3.2−1:3.5) and wild-type kidney showed almost a 1:1 ratio (1:0.85). A systematic review of 126 cases clarified that the median age of developing ESKD was 16 years in all FS patients, and there were no statistically significant differences between the genotypes or sex chromosome karyotypes in terms of the renal survival period.

Conclusion

Our study suggested no differences in splicing pattern or renal survival period among reported intron 9 variants causative of FS.

Suspicion of Frasier's Syndrome in the Nephrology Unit of the State University Hospital of Haiti: Case Study and Review of Literature

Objective

Frasier syndrome is a rare genetic nephropathy characterized by the presence of progressive glomerulopathy with proteinuria associated with male pseudo hermaphroditism. This case study described a picture of a young boy where the clinical suspicion context reminded the Frasier syndrome. To our knowledge, this case is the first described in Haiti.

Case Study

This is a 19-year-old young phenotypically male, born with a genital anomaly, was seen on referral at the nephrology/dialysis unit of the internal medicine department of the State University Hospital of Haiti for evaluation and follow-up. Insidious progression of symptoms had occurred over 3 years. Over three months of outpatient follow-up, he had four sets of renal labs drawn, and all showed impaired renal function. At the ultrasound, a bilateral cryptorchidism is described in the inguinal, and presence of functional ovaries with follicles of variable size scattered in the parenchyma. So, in the light of these anamnestic, clinical and paraclinical findings, we concluded to the diagnosis of end-stage renal failure by progressive glomerulopathy in a context of Frasier's syndrome.

Conclusion

With any clinical picture consisting of genital anomalies at birth, renal symptomatology during childhood and the diagnosis of renal failure during adolescence, rare genetic nephropathies, such as Frasier syndrome must be considered.

Clinical utility of ultra-rapid whole-genome sequencing in an infant with atypical presentation of WT1-associated nephrotic syndrome type 4

Relatively little is known about phenotypic variability in nonsyndromic nephropathy associated with the gene encoding the WT1 transcription factor. We report a 12-mo-old female who presented with vomiting, diarrhea, and fatigue in the setting of renal failure and malignant hypertension. Trio ultra-rapid whole-genome sequencing identified a novel, likely pathogenic, de novo missense variant (c.485T > A, p.Val162Asp) in WT1 in 46 h, consistent with a diagnosis of nephrotic syndrome type 4 (NPHS4; OMIM 256370). This disorder typically presents with nephrotic syndrome (gross proteinuria, hypoalbuminemia, and edema). Rapid diagnosis had an immediate impact on her clinical management in the pediatric intensive care unit. Diagnostic renal biopsy was avoided, and placement of permanent dialysis access, a gastrostomy tube, and bilateral nephrectomy were accelerated. This report expands the presenting phenotype of nonsyndromic nephrotic syndrome and/or renal failure due to heterozygous variants in WT1 (NPHS4). It also highlights the relationship between time to genomic diagnosis and clinical utility in critically ill infants.

Wilms' tumour 1 gene mutations in south Indian children with steroid-resistant nephrotic syndrome

Background & objectives:

Clinically, nephrotic syndrome (NS) is a diverse group of symptoms; about 20 per cent of NS cases are resistant to steroid treatment, and within ten years they progress to end-stage renal disease. The present study was undertaken to identify the mutations of Wilms’ tumour 1 (WT1) gene in steroid-resistant NS (SRNS) children.

Methods:

A total of 173 children with SRNS and 100 children in the control group were enrolled in the study. DNA extraction was done, screened for WT1 (exons 8 and 9) gene amplified by polymerase chain reaction and direct sequencing. Karyotype analyses were done for WT1 mutation cases.

Results:

WT1 mutations were found in three of 173 SRNS cases (2 girls, 1 boy). All of them had intron 9 (IVS 9 + 4 C>T, 2; IVS + 5 G>A, 1) mutation. Of these three cases, one had familial and another two had sporadic history. Renal histology analysis showed two cases with focal segmental glomerulosclerosis (FSGS) and they had external female genitalia but 46, XY karyotype. Both of them had streak gonads. Of the three cases, one expired.

Interpretation & conclusions:

The findings of the present study indicate that all females with SRNS-FSGS should be screened for WT1 gene mutation to diagnose whether they have FS for possible gonadectomy.

Cytoplasmic Localization of WT1 and Decrease of miRNA-16-1 in Nephrotic Syndrome

Nephrotic syndrome (NS) is a glomerular disease that is defined by the leakage of protein into the urine and is associated with hypoalbuminemia, hyperlipidemia, and edema. Steroid-resistant NS (SRNS) patients do not respond to treatment with corticosteroids and show decreased Wilms tumor 1 (WT1) expression in podocytes. Downregulation of WT1 has been shown to be affected by certain microRNAs (miRNAs). Twenty-one patients with idiopathic NS (68.75% were SSNS and 31.25% SRNS) and 10 healthy controls were enrolled in the study. Podocyte number and WT1 location were determined by immunofluorescence, and the serum levels of miR-15a, miR-16-1, and miR-193a were quantified by RT-qPCR. Low expression and delocalization of WT1 protein from the nucleus to the cytoplasm were found in kidney biopsies of patients with SRNS and both nuclear and cytoplasmic localization were found in steroid-sensitive NS (SSNS) patients. In sera from NS patients, low expression levels of miR-15a and miR-16-1 were found compared with healthy controls, but only the miR-16-1 expression levels showed statistically significant decrease (p = 0.019). The miR-193a expression levels only slightly increased in NS patients. We concluded that low expression and delocalization from the WT1 protein in NS patients contribute to loss of podocytes while modulation from WT1 protein is not associated with the miRNAs analyzed in sera from the patients.

Gonadal tumor in Frasier syndrome: a review and classification

Frasier syndrome is a rare inherited disease characterized by steroid-resistant nephrotic syndrome, gonadal tumor, and male pseudohermaphroditism (female external genitalia with sex chromosomes XY), which is based on a splice site mutation of Wilms tumor-suppressor gene 1 (WT1). Several unusual Frasier syndrome cases have been reported in which male pseudohermaphroditism was absent. We reviewed 88 Frasier syndrome cases in the literature and classified them into three types (type 1-3) according to external genitalia and sex chromosomes, and described their clinical phenotypes. Type 1 Frasier syndrome is characterized by female external genitalia with 46,XY (n = 72); type 2 by male external genitalia with 46,XY (n = 8); and type 3 by female external genitalia with 46,XX (n = 8). Clinical course differs markedly among the types. Although type 1 is noticed at the mean age of 16 due to mainly primary amenorrhea, type 2 and 3 do not present delayed secondary sex characteristics, making diagnosis difficult. The prevalence of gonadal tumor is high in type 1 (67%) and also found in 3 of the 8 type 2 cases, but not in any type 3 cases, which emphasize that preventive gonadectomy is unnecessary in type 3. On the basis of our findings, we propose a new diagnostic algorithm for Frasier syndrome.