Absence of mutations in the WT1 gene in patients with XY gonadal dysgenesis

Denys-Drash syndrome, septated vagina and low level of anti-Mullerian hormone in male neonate

There is a wide variety of genital abnormalities observed in patients with Denys-Drash syndrome (DDS). WT1 is thought to influence the genes related to genital development and mutations in this gene have been associated with DDS. DDS should be considered in the differential diagnosis of newborns with genital anomalies. In contrast to other conditions with 46,XY disorders of sex development, individuals with DDS often have duplicated genital organs (a double vagina, cervix or uterus). A double uterus has not yet been reported with 1390G>A (Arg464 Asn) mutation. However, duplicated genitals have been reported with other genetic mutations in patients with DDS. The duplicated genitals in DDS may be associated with low anti-Mullerian hormone (AMH) secretion. Measurement of the AMH levels may add to our understanding of variations in genital development and their abnormalities in disorders such as DDS. In conclusion, this is first case of low level of AMH and double uterus in 1390G>A (Arg464 Asn) mutations of DDS male.

Analysis of the Wilms' tumor suppressor gene (WT1) in patients 46,XY disorders of sex development

CONTEXT

The Wilms' tumor suppressor gene (WT1) is one of the major regulators of early gonadal and kidney development. WT1 mutations have been identified in 46,XY disorders of sex development (DSD) with associated kidney disease and in few isolated forms of 46,XY DSD.

OBJECTIVE

The objective of the study was the evaluation of WT1 mutations in different phenotypes of isolated 46,XY DSD and clinical consequences.

DESIGN

The design of the study was: 1) sequencing of the WT1 gene in 210 patients with 46,XY DSD from the German DSD network, consisting of 150 males with severe hypospadias (70 without cryptorchidism, 80 with at least one cryptorchid testis), 10 males with vanishing testes syndrome, and 50 raised females with partial to complete 46,XY gonadal dysgenesis; and 2) genotype-phenotype correlation of our and all published patients with 46,XY DSD and WT1 mutations.

RESULTS

We have detected WT1 mutations in six of 80 patients with severe hypospadias (7.5%) and at least one cryptorchid testis and in one of 10 patients with vanishing testes syndrome (10%). All patients except one developed Wilms' tumor and/or nephropathy in childhood or adolescence.

CONCLUSION

WT1 analysis should be performed in newborns with complex hypospadias with at least one cryptorchid testis and in isolated 46,XY partial to complete gonadal dysgenesis. Kidney disease might not develop until later life in these cases. WT1 analysis is mandatory in all 46,XY DSD with associated kidney disease. WT1 analysis is not indicated in newborns with isolated hypospadias without cryptorchidism. Patients with WT1 mutations should be followed up closely because the risk of developing a Wilms' tumor, nephropathy, and/or gonadal tumor is very high.

A novel WT1 mutation in a 46,XY boy with congenital bilateral cryptorchidism, nystagmus and Wilms tumor

The WT1 gene plays a crucial role in urogenital and gonadal development. Germline WT1 alterations have been described in a wide spectrum of pathological conditions, including kidney diseases, genital abnormalities and Wilms tumor (WT), frequently occurring in combination. We report on a novel WT1 nonsense mutation (c.1105C>T), introducing a premature stop codon in exon 8 (p.Q369X), in a young XY male patient who presented with bilateral cryptorchidism, nystagmus, mild proteinuria and WT, but no sign of severe nephropathy. Although the majority of congenital urogenital abnormalities are not due to constitutional defects of the WT1 gene, our findings provide a rational for considering WT1 mutational analysis as one of the screening options in newborns with congenital defects of the urogenital tract due to the associated high risk of WT.

Apolipoprotein A-I/C-III/A-IV SstI and apolipoprotein B XbaI polymorphisms do not affect early functional and structural changes in atherosclerosis: the Cardiovascular Risk in Young Finns study

BACKGROUND

The present study was designed to investigate the effects of apoB XbaI and apoA-I/C-III/A-IV SstI polymorphisms to carotid artery intima-media thickness (IMT), carotid artery compliance (CAC) and brachial artery flow-mediated vasodilatation (FMD).

METHODS AND RESULTS

As part of the Cardiovascular Risk in Young Finns Study, the carotid IMT, CAC and brachial FMD of 2,265 subjects (mean age +/- SD 32 +/-5 years) were measured with ultrasonography, and genotyping of the apolipoprotein polymorphisms was performed. The frequencies of the genotypes did not differ between the groups with high (above median 0.57 mm) and low (below median) IMT, CAC or FMD. The average carotid IMT differed between the 3 apoB XbaI genotypes (ANOVA, p=0.04), but not between the apoA-I/C-III/A-IV SstI genotypes (ANOVA, p=0.53). The relationship between the polymorphisms and carotid IMT was not significant in any of the covariate-adjusted logistic and linear regression analyses. CAC and FMD were not influenced by either of the polymorphisms in ANOVA and regression analyses.

CONCLUSIONS

The polymorphisms apoA-I/C-III/A-IV SstI and apoB XbaI do not seem to affect carotid artery characteristics or brachial artery FMD in young adulthood.

Polymorphisms in Four Genes Related to Triglyceride and HDL-cholesterol Levels in the General Japanese Population in 2000

We studied the association of six common polymorphisms of four genes related to lipid metabolism with serum lipid levels. We selected single-nucleotide polymorphisms (SNPs) in the genes for cholesteryl ester transfer protein (CETP), lipoprotein lipase (LPL), hepatic lipase (LIPC), and apolipoprotein CIII (APOC3), and studied 2267 individuals randomly selected from the participants of Serum Lipid Survey 2000. There was a significant association of CETP polymorphism (D442G, Int14 +1 G --> A, and TaqIB), LPL polymorphism (S447X), and LIPC polymorphism (-514 --> CT) with HDL-cholesterol levels. We also found a significant association of LPL polymorphism (S447X) and APOC3 polymorphism (SstI) with triglyceride levels. This is the largest database showing the association of common genetic variants in lipid metabolism with serum lipid levels in the general Japanese population. Further study is necessary to elucidate the role of these gene polymorphisms in cardiovascular events.

Early prenatal diagnosis of recurrent 46,XY partial gonadal dysgenesis

OBJECTIVES

We present a case of early prenatal diagnosis of recurrent 46,XY partial gonadal dysgenesis, by combining early genetic and sonographic evaluations.

METHODS

The conceptus of a mother with a first child affected by 46,XY gonadal dysgenesis was sonographically evaluated at 21- and 23-mm BPD (12(+2) and 12(+6) LMP-based age) and the female genitalia were observed. Karyotype analyses was performed on amniotic fluid and it revealed a 46,XY complement without mosaicism. SRY was amplified by PCR for molecular analyses.

RESULTS

We observed a discordance between female phenotype detected at 21 and 23 mm of biparietal diameter (12(+2) and 12(+6) LMP-based age) and male karyotype. In the child and the fetus, seminiferous cords were not recognisable, whereas rare Leydig cells and no germ cells could be identified. Internal and external genitalia were sexually ambiguous in the child and feminized in the fetus.

CONCLUSION

This is the first case of early prenatal diagnosis of recurrent 46,XY partial gonadal dysgenesis and it points to the importance of combining early analyses of genetic sex with sonography in the management of anomalies of sexual development, with particular regard to syndromes for which the risk of recurrence is little understood.

Surgical management and genotype/phenotype correlations in WT1 gene-related diseases (Drash, Frasier syndromes)

BACKGROUND/PURPOSE

The WT1 gene plays a role in urogenital and gonadal development. Germline mutations of this gene have been observed in patients with Drash or Frasier syndrome (Sd). The purpose of this report is to compare phenotype and genotype of these patients.

METHODS

Retrospective study of 12 patients treated since 1980 for WT1 gene-related disorders was conducted.

RESULTS

End-stage renal disease (ESRD) occurred in 9 patients, mostly because of diffuse mesangial sclerosis (DMS) or focal and segmental glomerular sclerosis (FSGS). Seven patients underwent kidney transplantation, and 2 died. Eleven tumors occurred: 8 Wilms' tumors, one soft tissue tumor, one bladder papilloma, and one gonadoblastoma. Wilms' tumors occurred at a younger age than expected. Eight patients had a 46,XY karyotype. One of these XY patients had female phenotype (Frasier syndrome); she was raised as a girl with bilateral gonadectomy. Seven XY patients had ambiguous phenotype; 4 have been raised as boys and 3 as girls. Four patients had a 46,XX karyotype; they had female genitalia and were raised as girls. WT1 gene analysis was performed in 10 patients and showed heterozygous germline mutations in exon 9 (n = 6), intron 9 (n = 1), exon 3 (n = 1), exon 4 (n = 1), or exon 7 (n = 1).

CONCLUSIONS

ESRD was secondary to DMS when exon 9 was mutated, and secondary to FSGS when intron 9 was mutated. When exon 3, 4, and 7 were mutated, no nephropathy has been observed. Wilms' tumors occurred with any kind of WT1 mutation except intron 9. Abnormal sexual differentiation has been observed in all XY patients with WT1 mutation, and the most profound inversion of phenotype was observed with mutation in intron 9. Correlation between phenotype and genotype provides better understanding of the role of WT1, and can help the surgeon in the management of these patients.

46,XY gonadal dysgenesis: evidence for autosomal dominant transmission in a large kindred

46,XY gonadal dysgenesis is characterized by abnormal testicular determination. We describe a large kindred in which various disorders of sexual development were observed, ranging from completely female phenotype without ambiguities of the external genitalia (five cases) to men with isolated penile or perineal hypospadias (four cases), including two cases with moderate virilization and one case with ambiguity of the external genitalia. Histologic examination of gonadal tissue was performed on seven subjects. These findings were suggestive of complete gonadal dysgenesis in one patient, partial gonadal dysgenesis in three patients, and mixed gonadal dysgenesis in three patients. Four patients developed gonadal tumors (two gonadoblastoma, two dysgerminoma, and one immature teratoma, i.e., one patient had a dysgerminoma with some areas of gonadoblastoma). All affected subjects had no other congenital anomalies or dysmorphic features. Analysis of families with several affected individuals with 46,XY gonadal dysgenesis implied an X-linked mode of inheritance because of the apparent absence of male-to-male transmission. However, a sex-limited autosomal dominant mode of inheritance affecting only XY individuals could not be ruled out. Analysis of the pedigree we report indicated an autosomal dominant mode of inheritance because of male-to-male transmission. This kindred supports the involvement of at least one autosomal gene in non-syndromic 46,XY gonadal dysgenesis.

A clinical overview of WT1 gene mutations

Mutations in the WT1 gene were anticipated to explain the genetic basis of the childhood kidney cancer, Wilms tumour (WT). Six years on, we review 100 reports of intragenic WT1 mutations and examine the accompanying clinical phenotypes. While only 5% of sporadic Wilms' tumours have intragenic WT1 mutations, > 90% of patients with the Denys-Drash syndrome (renal nephropathy, gonadal anomaly, predisposition to WT) carry constitutional intragenic WT1 mutations. WT1 mutations have also been reported in juvenile granulosa cell tumour, non-asbestos related mesothelioma, desmoplastic small round cell tumour and, most recently, acute myeloid leukemia.

The human doublesex-related gene, DMRT2, is homologous to a gene involved in somitogenesis and encodes a potential bicistronic transcript

Intense efforts are currently being pursued to identify autosomal genes associated with 46,XY male-to-female sex reversal. The genes DMRT1 and 2 are located on distal 9p, a region deleted in 46,XY sex-reversed patients. They are considered excellent candidates because of their homology to regulators of sex development in invertebrates. We present the genomic structure of DMRT2, showing that it generates several transcripts with distinct coding potential. In addition to the previously reported 226-amino-acid protein-encoding transcript, we describe other mRNA isoforms that are potentially bicistronic and are predicted to encode an additional 328-amino-acid polypeptide. Finally, a stop codon-containing exon (exon 4) can be skipped by alternative splicing and can generate a transcript that is predicted to encode a fusion protein. The latter shares 58% amino acid identity with a gene recently described in fish, termed terra. Differences in expression pattern exist for DMRT2 mRNA isoforms among the human adult tissues tested, between adult tissues and human embryos, and between DMRT2 and DMRT1 during embryonic development. We failed to detect mutations by sequencing of DMRT2 in a sample of 46,XY female patients. The interesting structure of DMRT2 coupled to preliminary functional studies in fish showing that terra is involved in somitogenesis suggests that validation or exclusion of this gene as a cause of sex reversal will require more in-depth investigations.

Disorders of sexual differentiation

An infant born with ambiguous genitalia requires an accurate and prompt diagnosis so that a management plan can be formulated. This article discusses the signaling cascade of genes that controls sexual differentiation. Clinical disorders involving sex reversal or ambiguous genitalia are discussed in relation to the genes regulating sexual development. An approach to the treatment of these disorders is outlined.

Identification of constitutional WT1 mutations, in patients with isolated diffuse mesangial sclerosis, and analysis of genotype/phenotype correlations by use of a computerized mutation database

Constitutional mutations of the WT1 gene, encoding a zinc-finger transcription factor involved in renal and gonadal development, are found in most patients with Denys-Drash syndrome (DDS), or diffuse mesangial sclerosis (DMS) associated with pseudohermaphroditism and/or Wilms tumor (WT). Most mutations in DDS patients lie in exon 8 or exon 9, encoding zinc finger 2 or zinc finger 3, respectively, with a hot spot (R394W) in exon 9. We analyzed a series of 24 patients, 10 with isolated DMS (IDMS), 10 with DDS, and 4 with urogenital abnormalities and/or WT. We report WT1 heterozygous mutations in 16 patients, 4 of whom presented with IDMS. One male and two female IDMS patients with WT1 mutations underwent normal puberty. Two mutations associated with IDMS are different from those described in DDS patients. No WT1 mutations were detected in the six other IDMS patients, suggesting genetic heterogeneity of this disease. We analyzed genotype/phenotype correlations, on the basis of the constitution of a WT1 mutation database of 84 germ-line mutations, to compare the distribution and type of mutations, according to the different symptoms. This demonstrated (1) the association between mutations in exons 8 and 9 and DMS; (2) among patients with DMS, a higher frequency of exon 8 mutations among 46, XY patients with female phenotype than among 46,XY patients with sexual ambiguity or male phenotype; and (3) statistically significant evidence that mutations in exons 8 and 9 preferentially affect amino acids with different functions.

Genetic control of gonadal differentiation

The study of naturally occurring mutations in humans and induced mutations in mice that cause sex reversal has been instrumental in the cloning and functional analysis of genes involved in gonadal differentiation. Several genes required for this complex developmental process have now been identified. The genes LIM1, WT1 and FTZ-F1 have been demonstrated to be involved in the formation of the gonads prior to their differentiation as testes or ovaries. Subsequent sex-specific gonadal differentiation appears to be mediated by the SRY and SOX9 genes in the testis, and the DAX-1 gene in the ovary.

Software and database for the analysis of mutations in the human WT1 gene

The WT1 gene, located at 11p13, encodes a zinc finger transcription factor involved in renal and gonadal development and in Wilms' tumor. Constitutional mutations of this gene have been described in most patients with Denys Drash syndrome (mesangial sclerosis associated with male pseudohermaphrodism and/or Wilms' tumor), but also in patients with genitourinary abnormalities and Wilms' tumor (WT) or presenting with only unilateral or bilateral WT. Moreover, approximately 10% of Wilms' tumors carry WT1 mutations at the somatic level. To facilitate the genotype-phenotype correlation analyses, we have created a software package along with a computerized database of germline (70 entries) and somatic (28 entries) mutations reported in the literature.

Sex determination in humans

In mammals, the Y chromosome induces testis formation and thus male sexual development; in the absence of a Y chromosome, gonads differentiate into ovaries and female development ensues. Molecular genetic studies have identified the Y-located testis determining gene SRY as well as autosomal and X-linked genes necessary for gonadal development. The phenotypes resulting from mutation of these genes, together with their patterns of expression, provide the basis for establishing a hierarchy of genes and their interactions in the mammalian sex determination pathway.

The role of SRY in mammalian sex determination

The gene SRY (sex determining region of the Y), located at the distal region of the short arm of the Y chromosome, is necessary for male sex determination in mammals. SRY initiates the cascade of steps necessary to form a testis from an undifferentiated gonad. The SRY gene encodes an HMG (High Mobility Group) protein which may act as a transcription factor by binding to double stranded DNA and then bending the DNA. Mutations in SRY have been identified in some subjects with 46,XY pure gonadal dysgenesis. However the role for other autosomal and X-linked genes in testis determination is evident by the presence of a normal SRY gene in the majority of females with 46,XY pure gonadal dysgenesis and the lack of SRY in a minority of males with 46,XY maleness.

No evidence of WT1 gene mutations in children with congenital diaphragmatic hernia

Children with congenital diaphragmatic hernia are born with a defect of the diaphragm that usually leads to a herniation of abdominal organs up into the thoracic cavity on the same side. The condition is often fatal, usually because of concomitant lung hypoplasia. The cause of this condition is unknown. The majority of cases are sporadic, but familial aggregation has been observed, indicating a genetic background. The tumor suppressor gene WT1 is involved in normal early urogenital development, and it is expressed in the mesothelium in the early human fetus. Recently, knockout mice homozygous for WT1 gene mutations were constructed. The embryos died between days 13 and 15 of gestation. Besides serious urogenital and thoracic malformations, the mice had defects in the diaphragm that caused herniation of lung tissue into the abdomen. These findings prompted the authors to screen for WT1 gene mutations in 27 children who had congenital diaphragmatic hernia. Using exon-per-exon polymerase chain reaction (PCR) amplifications and denaturing gradient gel electrophoresis, no WT1 mutations were detected. Southern blot analysis did not show any large rearrangements in the WT1 gene. These results exclude WT1 gene mutations as a major etiological factor for the isolated diaphragmatic defect. However, it is possible that other genes in the WT1 pathway are involved in this defect.

Constitutional and somatic mutations in the WT1 gene in Wilms' tumor patients

Wilms' tumor development, like most tumors, involves multiple genetic alterations affecting diverse genes. Only one of these has thus far been identified, the Wilms' tumor 1 (WT1) gene on 11p13, which functions as a tumor suppressor gene. We assessed the involvement of the WT1 gene constitutionally and somatically in 26 Wilms' tumor patients. Of these, the clinical data suggest a constitutional pre-disposition in 12 bilateral cases and 7 cases with early onset. We employed Southern blot analysis and PCR-based markers for analyses of somatic allelic losses in chromosome bands 11p13, 11p15 and 16q and screened for point mutations in exons 2-10 of the WT1 gene with denaturing gradient gel electrophoresis (DGGE). Of the 12 cases with multiple tumors, 1 exhibited a constitutional 11p13 deletion and a somatic stop mutation in exon 4 of the WT1 gene and 2 harbored constitutional mutations in the WT1 gene: a pre-mature stop codon in exon 6 in a boy with bilateral cryptorchidism and bilateral Wilms' tumors and an intragenic deletion in a girl with bilateral WT. Three additional bilateral tumors displayed WT1 rearrangements or allelic losses with 11p13 markers. Four of 7 patients with an early onset of unilateral tumor had losses of 11p13, though no WT1 mutations were detected. Two of the remaining cases that did not show any somatic or constitutional 11p13 alterations had Beckwith-Wiedemann syndrome, known to involve the 11p15 region.