Bilateral Gonadoblastoma in a 6-Year-old Girl With Frasier Syndrome: Need for Early Preventive Gonadectomy

Frasier syndrome (FS) is a rare condition, caused by splice-site mutations of intron 9 in the Wilms' tumor suppressor gene 1 (WT1 gene). The WT1 protein is essential for urogenital development and patients with 46XY karyotype present with female (FS type 1) or male phenotype, gonadal dysgenesis, progressive glomerulopathy, and high risk of gonadoblastoma. We describe a female patient with an IVS9+4C>T donor splice-site mutation, who underwent a preventive gonadectomy at the age of 6 years due to imaging findings of dysplastic gonads. The biopsy revealed bilateral gonadoblastoma, emphasizing the need for early gonadectomy in 46XY FS patients.

Malformation syndromes associated with disorders of sex development

When embryological development of the internal and/or external genitalia is disrupted, the patient presents with a disorder of sex development (DSD) in the neonatal period or sometime later in life. Some of these patients have other, nongenital malformations, which makes their overall management more complex than if they just had a DSD. This Review summarises these malformation syndromes and discusses the recent research into their aetiology. The genetic causes of these malformation syndromes, when they are known, will also be described. Many specific genetic mutations are now known in malformation syndromes with a defect in hormonal function. By contrast, the genetic causes remain unknown in many nonhormonal morphological anomalies that affect the genitalia.

A 46,XY female DSD patient with bilateral gonadoblastoma, a novel SRY missense mutation combined with a WT1 KTS splice-site mutation

Patients with Disorders of Sex Development (DSD), especially those with gonadal dysgenesis and hypovirilization are at risk of developing malignant type II germ cell tumors/cancer (GCC) (seminoma/dysgerminoma and nonseminoma), with either carcinoma in situ (CIS) or gonadoblastoma (GB) as precursor lesion. In 10–15% of 46,XY gonadal dysgenesis cases (i.e., Swyer syndrome), SRY mutations, residing in the HMG (High Mobility Group) domain, are found to affect nuclear transport or binding to and bending of DNA. Frasier syndrome (FS) is characterized by gonadal dysgenesis with a high risk for development of GB as well as chronic renal failure in early adulthood, and is known to arise from a splice site mutation in intron 9 of the Wilms’ tumor 1 gene (WT1). Mutations in SRY as well as WT1 can lead to diminished expression and function of SRY, resulting in sub-optimal SOX9 expression, Sertoli cell formation and subsequent lack of proper testicular development. Embryonic germ cells residing in this unfavourable micro-environment have an increased risk for malignant transformation. Here a unique case of a phenotypically normal female (age 22 years) is reported, presenting with primary amenorrhoea, later diagnosed as hypergonadotropic hypogonadism on the basis of 46,XY gonadal dygenesis with a novel missense mutation in SRY. Functional in vitro studies showed no convincing protein malfunctioning. Laparoscopic examination revealed streak ovaries and a normal, but small, uterus. Pathological examination demonstrated bilateral GB and dysgerminoma, confirmed by immunohistochemistry. Occurrence of a delayed progressive kidney failure (focal segmental glomerular sclerosis) triggered analysis of WT1, revealing a pathogenic splice–site mutation in intron 9. Analysis of the SRY gene in an additional five FS cases did not reveal any mutations. The case presented shows the importance of multi-gene based diagnosis of DSD patients, allowing early diagnosis and treatment, thus preventing putative development of an invasive cancer.

Sertoli cell tumor and gonadoblastoma in an untreated 29-year-old 46,XY phenotypic male with Frasier syndrome carrying a WT1 IVS9+4C>T mutation

OBJECTIVE

Frasier syndrome (FS) phenotype in 46,XY patients usually consists of female external genitalia, gonadal dysgenesis, high risk of gonadoblastoma and the development of end stage renal failure usually in the second decade of life. FS is caused by heterozygous de novo intronic splice site mutations of the Wilms' tumor suppressor gene 1 (WT1), although a few cases with typical exonic WT1 Denys-Drash mutations that resemble an FS phenotype have been described. The aim of this study was to present further data on the spectrum of FS phenotypes through the evaluation of a 29-year-old patient with a predominantly male phenotype and coexistence of Sertoli cell tumor and gonadoblastoma.

RESULTS

Genetic analysis using standard methods for DNA sequencing confirmed FS due to a WT1 gene mutation, IVS9+4C>T.

CONCLUSIONS

This very rare case illustrates the natural course of FS over many years due to the neglect by the patient to address his need for follow-up, while adding further data on the spectrum of FS phenotypes associated with IVS9+4 C>T mutations. The coexistence of the rare Sertoli cell tumor and gonadoblastoma emphasizes that early clinical recognition and molecular identification facilitates appropriate patient management, especially with respect to the high risk of gonadal malignancy.

Alternative splicing and its role in pathologies of the endocrine system

Alternative splicing of pre-mRNA is a process in which noncoding regions of primary transcript are removed and coding regions are joined in different manners to produce mRNA molecules of different sequences. Alternative splicing affects nearly all human genes and is a key source of diversity of proteins coded by a relatively small number of genes. Since alternative splicing is of crucial importance for the proper functioning of cells, including those involved in hormonal signalling, aberrations of alternative splicing can lead to disruption of cellular mechanisms and in consequence result in serious endocrine pathologies. Disturbances of alternative splicing include mutations of consensus splice regulatory sites and improprieties in the action of splicing factors, the proteins involved in regulating the process. In consequence of disturbed alternative splicing, improperly spliced mRNA and protein isoforms can be produced which can lead to disruption of function of their wild type counterparts. This review aims to discuss the role of alternative splicing in pathologies of the endocrine system and gives examples that highlight the importance of this process in the proper functioning of hormones, hormone receptors and other factors involved in hormonal regulation. The examples given include endocrine-related tumours (pituitary tumours, cancers of the thyroid, prostate, ovary and breast, and insulinoma), isolated growth hormone deficiency, and Frasier syndrome. Non-endocrine pathologies in which aberrant alternative splicing of transcripts of genes involved in hormonal signalling have been detected are also described. Finally, we discuss future perspectives on the possible usage of alternative splicing in diagnostics and therapy.

Genetic analysis of fin development in zebrafish identifies furin and hemicentin1 as potential novel fraser syndrome disease genes

Using forward genetics, we have identified the genes mutated in two classes of zebrafish fin mutants. The mutants of the first class are characterized by defects in embryonic fin morphogenesis, which are due to mutations in a Laminin subunit or an Integrin alpha receptor, respectively. The mutants of the second class display characteristic blistering underneath the basement membrane of the fin epidermis. Three of them are due to mutations in zebrafish orthologues of FRAS1, FREM1, or FREM2, large basement membrane protein encoding genes that are mutated in mouse bleb mutants and in human patients suffering from Fraser Syndrome, a rare congenital condition characterized by syndactyly and cryptophthalmos. Fin blistering in a fourth group of zebrafish mutants is caused by mutations in Hemicentin1 (Hmcn1), another large extracellular matrix protein the function of which in vertebrates was hitherto unknown. Our mutant and dose-dependent interaction data suggest a potential involvement of Hmcn1 in Fraser complex-dependent basement membrane anchorage. Furthermore, we present biochemical and genetic data suggesting a role for the proprotein convertase FurinA in zebrafish fin development and cell surface shedding of Fras1 and Frem2, thereby allowing proper localization of the proteins within the basement membrane of forming fins. Finally, we identify the extracellular matrix protein Fibrillin2 as an indispensable interaction partner of Hmcn1. Thus we have defined a series of zebrafish mutants modelling Fraser Syndrome and have identified several implicated novel genes that might help to further elucidate the mechanisms of basement membrane anchorage and of the disease's aetiology. In addition, the novel genes might prove helpful to unravel the molecular nature of thus far unresolved cases of the human disease.

There are a large number of human genetic syndromes with limb and digit deformities. It has been shown that the genes underlying these syndromes are well conserved in evolution, and most perform the same role even in the fins of fish. One such human syndrome is Fraser Syndrome, characterized by a number of defects including fusion of the fingers (syndactyly). Data obtained with corresponding mouse mutants suggest that all of these defects are due to transient basement membrane disruptions and epithelial blistering during development. Whilst some of the Fraser Syndrome genes have been identified, others are unknown. We show that mutation of the known Fraser Syndrome genes in zebrafish generate comparable blistering defects in the fins. Importantly, we have also identified additional genes and mechanisms required for the same processes. Included in this are hemicentin1, a gene whose function had thus far only been studied in nematodes, and furinA, encoding a proprotein convertase, for which we reveal a novel role in ectodomain shedding of Fras/Frem proteins. This work thus expands our understanding, not only of Fraser Syndrome, but also of the common processes of basement membrane formation and function during fin and limb development.

Ambiguous genitalia in neonates: a 4-year prospective study in a localized area

This study aimed to determine the possible etiology ot ambiguous genitalia in 41 newborn intants at a referral hospital in Hofuf city, Saudi Arabia. In 46,XX karyotype patients (n 14), congenital adrenal hyperplasia and general malformation disorder were the most common causes of genital ambiguity, while in 46,XY karyotype patients (n=18), testosterone pathway biosynthetic defect was the most common cause even in conjunction with a generalized malformation disorder. In patients with abnormal karyotype (n=3), 1 had trisomy 18 (47,XX) and died after 3 months and 2 had different types of mosaic Turner syndrome. The karyotype was undetermined in 6 natients. Positive family history of ambiguous genitalia was noted in 4 patients.

[WT1 mutation as a cause of progressive nephropathy in Frasier syndrome--case report]

Frasier syndrome is an uncommon genetic disorder featuring progressive glomerulopathy, male pseudohermaphroditism and gonadal dysgenesis. It is caused by mutations in intron 9 of the WT1 gene. Because of its rarity there is limited literature available on the diagnosis and treatment of this syndrome. The aim of the study was to present the clinicopathological findings and molecular analysis of phenotypically female adolescent presenting with severe proteinuria and primary amenorrhea. The significance of early recognition of Frasier syndrome and its differentiation from Denys-Drash syndrome was discussed. WT1 mutation analysis should be routinely done in females with steroid-resistant nephritic syndrome.

Expanding the clinical spectrum of Frasier syndrome

Frasier syndrome is an uncommon genetic disorder featuring progressive glomerulopathy, male pseudohermaphroditism, and gonadal dysgenesis with increased risk of gonadoblastoma and malignant germ cell tumors. It is caused by mutations in the donor splice site in intron 9 of the WT1 gene. However, because of its rarity there is limited literature available on the precise spectrum and recommended treatment modalities of this syndrome. We present the clinicopathological findings in 4 patients: 3 phenotypically female adolescents presenting with proteinuria and primary amenorrhea and a 6-month-old baby girl presenting with nephrotic syndrome in whom this very unusual case of early onset was confirmed by molecular studies. The significance of early recognition of Frasier syndrome and its differentiation from Denys-Drash syndrome is reviewed and discussed. Our observation of a case presenting with early clinical manifestations, in contrast with the classical presentation in adolescence, justifies the expansion of the clinical spectrum of Frasier syndrome and contributes to the understanding and appropriate clinical management of these patients.

WT1 mutation and podocyte molecular expression in a Chinese Frasier syndrome patient

We report on a Chinese girl with Frasier syndrome (FS). She presented with steroid-resistant focal segmental glomerulosclerosis (FSGS) and male pseudohermaphroditism. The WT1 IVS 9 + 5 G>A mutation was detected in one allele in the proband. The ratio of +KTS/-KTS was 0.67 in the proband's cDNA. The expression of podocyte molecules (WT1, nephrin, podocin, alpha-actinin 4 and CD2AP) were also investigated in a renal specimen of this FS patient. WT1 expression showed diffuse nuclear staining, with less obvious speckles in the patient's glomeruli than in those of controls. The distribution and intensity of podocyte molecules were altered both in normal- and abnormal-appearing glomeruli. In conclusion, the study presented a case of FS by clinical manifestation, renal pathology, karyotype analysis and genetic testing. A lower ratio of +KTS/-KTS and an abnormal distribution of WT1, as well as abnormal expressions of other podocyte molecules, were also revealed. The mechanisms of WT1 mutation causing FS still need to be investigated.

WT1 intron 9 splice acceptor site mutation in a 46,XY male with focal segmental glomerulosclerosis

The Wilms' tumor suppressor gene (WT1) plays crucial roles in urogenital and gonadal development. Germline mutations of WT1 have been reported in patients with Denys-Drash syndrome (DDS) and Frasier syndrome (FS). Based on clinical overlaps reported to date, it has been suggested that these two syndromes should be considered as part of a spectrum of diseases caused by WT1 gene mutations, rather than as separate diseases. We report a new mutation in an intron 9 splice acceptor site (IVS -1G-->) in a Japanese 46,XY male patient with focal segmental glomerulosclerosis (FSGS) and bilateral cryptorchism. The clinical phenotype of this patient resembled FS without male pseudohermaphroditism. Interestingly, although the patient's right kidney was diagnosed with FSGS, his left kidney showed severe hypoplasia. There are no previous case reports of FSGS and renal hypoplasia in the same individual with a WT1 mutation. The findings for this case further suggest that the renal phenotype has various manifestations and is not always decided by the type of WT1 mutation. The possibility that the position of the WT1 mutation may influence the course of the nephropathy should be evaluated in a larger patient cohort.

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.

WT1 mutations in nephrotic syndrome revisited. High prevalence in young girls, associations and renal phenotypes

WT1 mutations have been considered a rare cause of nephrotic syndrome but recent reports challenge this assumption. Exclusion of inherited forms is a basic point in any therapeutic strategy to nephrotic syndrome since they do not respond to drugs. We screened for WT1 mutations in 200 patients with nephrotic syndrome: 114 with steroid resistance (SRNS) and 86 with steroid dependence (SDNS) for whom other inherited forms of nephrotic syndrome (NPHS2, CD2AP) had been previously excluded. Three girls out of 32 of the group with steroid resistance under 18 years presented classical WT1 splice mutations (IVS9+5G>A, IVS9+4C>T) of Frasier syndrome. Another one presented a mutation coding for an amino acid change (D396N) at exon 9 that is typical of Denys-Drash syndrome. All presented resistance to drugs and developed end stage renal failure within 15 years. Two girls of the Frasier group presented a 46 XY karyotype with streak gonads while one was XX and had normal gonad morphology. In the two cases with IVS9+5G>A renal pathology was characterized by capillary wall thickening with deposition of IgG and C3 in one that was interpreted as a membrane pathology. Foam cells were diffuse in tubule-interstitial areas. In conclusion, WT1 splice mutations are not rare in females under 18 years with SRNS. This occurs in absence of a clear renal pathology picture and frequently in absence of phenotype change typical of Frasier syndrome. In adults and children with SDNS, screening analysis is of no clinical value. WT1 hot spot mutation analysis should be routinely done in children with SRNS; if the molecular screening anticipates any further therapeutic approach it may modify the long term therapeutic strategy.

Lack of puberty despite elevated estradiol in a 46,XY phenotypic female with Frasier syndrome

Frasier syndrome is characterized by slowly progressive nephropathy, male pseudohermaphroditism, streak gonad, and high risk of gonadoblastoma development. Here we report a case of a 46,XY phenotypic female with Frasier syndrome, who was under hemodialysis. While her serum estradiol level was gradually increasing annually, gonadotropin level was constantly extremely high, and her appearance was still prepubertal. She was heterozygous for a novel guanine>adenine point mutation at position +1 of the splice donor site within intron 9 (IVS 9 + 1G>A) of the Wilms' tumor 1 gene. The possibility of this disease should be taken into consideration whenever we encounter a patient with steroid-resistant nephrotic syndrome and delayed puberty.

Frasier syndrome: a rare cause of delayed puberty

We report on a post-renal transplant patient who presented with delayed pubertal development at the age of 15 years. She had a normal female phenotype. Blood analysis showed hypergonadotropic hypogonadism. Her karyotype was 46,XY. DNA analysis showed a heterozygous mutation in the WT1 gene (C to T mutation at position +4 of the splice donor site within intron 9). A diagnosis of Frasier syndrome was made and she underwent laparoscopic gonadectomy. This case illustrates that, while delayed puberty is common in children with chronic illness, clinicians should be particularly aware of the possibility of Frasier syndrome in those with progressive glomerulopathy and delayed puberty. DNA analysis is a useful means of confirming the diagnosis.

[Frasier syndrome: a rare syndrome with WT1 gene mutation in pediatric urology]

INTRODUCTION

Frasier syndrom is an autosomal dominant, hereditary disease characterized by nephropathy, gonadal dysgenesis and risk of gonadal blastoma in early childhood. To date, in many patients with Frasier syndrome WT1 mutations have been found, occurring exclusively as germ-line mutations of the alternative splicing donor site in intron 9. A Wilms tumor is seen only rarely in this clinical entity. In the present paper we describe the clinical course of a patient with Frasier syndrome confirmed by molecular genetic analysis.

CASE REPORT

Our patient with Frasier syndrome as confirmed by molecular genetic analysis is now 19 years old. The patient became dependent on dialysis due to nethropathy in the form of focal sclerosing glomerulonephritis and terminal renal insufficiency. A kidney transplantation in the left iliac fossa together with new implantation of the ureter according to Dodson. For prophylactic reasons on account of the high risk of gonadal blastoma associated with the disease and sonographically detected microlithiasis in both testicles we performed one year later an inguinal castration. Histology revealed the picture of a severe tubular testicular atrophy with arrested spermatogenesis and focal intratubular germ-line neoplasia.

CONCLUSIONS

This case report shows that, besides our already published series with Denys-Drash syndrome, WT1 mutations may also be associated with the so-called Frasier syndrome. For children with Frasier syndrome confirmed by molecular genetic analysis and loss of function of the testicles, we recommend performance of a prophylactic castration. We also suggest that phenotypical female patients with focal sclerosing glomerulonephritis be examined for WT1 mutations.

Variants in the Wilms' tumor gene are associated with focal segmental glomerulosclerosis in the African American population

Wilms' tumor gene (WT1) is important for nephrogenesis and gonadal growth. WT1 mutations cause Denys-Drash and Frasier syndromes, which are characterized by glomerular scarring. To test whether genetic variations in WT1 and WIT1 (gene immediately 5' to WT1) associate with focal segmental glomerulosclerosis (FSGS), patients with biopsy-proven idiopathic and HIV-1-associated FSGS were enrolled in a multicenter study. We genotyped SNP rs6508 located in WIT1 exon 1, three SNPs (rs2301250, rs2301252, rs2301254) in the promoter shared by WT1 and WIT1, rs2234590 in exon 6, rs2234591 in intron 6, rs16754 in exon 7, and rs1799937 in intron 9 of WT1. Cases (n = 218) and controls (n = 281) were compared in the African American population. Stratification by HIV-1 infection status showed that SNPs rs6508, rs2301254, and rs1799937 were significantly associated with FSGS [rs6508 odds ratio (OR) 1.82, P = 0.006; rs2301254 OR 1.65, P = 0.049; rs1799937 OR 1.91, P = 0.005] in the non-HIV-1 group and rs2234591 (OR 0.234, P = 0.011) in the HIV-1 group. Haplotype analyses in the population revealed that seven SNPs were associated with FSGS; five SNPs had the highest contingency score [-log10(P value) = 13.57] in the HIV-1 group. This association could not be explained by population substructure. We conclude that SNPs in WT1 and WIT1 genes are significantly associated with FSGS, suggesting that variants in these genes may mediate pathogenesis by altering WT1 function. Furthermore, HIV-1 infection status interacts with genetic variations in both genes to influence this phenotype. We speculate that nephropathy liability alleles in WT1 pathway genes cause podocyte dysfunction and glomerular scarring.

[The genetic basis of childhood nephrotic syndrome]

Great progress has been made of late in understanding the mechanisms of proteinuria, the structure and function of the slit diaphragm, and the genetic background of congenital nephrotic syndromes in new borns and infants. This paper presents recent achievements of molecular genetics in unraveling the causes of inherited disorders, e.g. Finnish-type nephrotic, Denys-Drash and Frasier's syndromes, as well as sporadic focal-segmental glomerulosclerosis. A change in the routine policy used in evaluating the causes of childhood nephrotic syndrome is discussed.