Ciliopathies with skeletal anomalies and renal insufficiency due to mutations in the IFT-A gene WDR19

A subset of ciliopathies, including Sensenbrenner, Jeune, and short-rib polydactyly syndromes are characterized by skeletal anomalies accompanied by multiorgan defects such as chronic renal failure and retinitis pigmentosa. Through exome sequencing we identified compound heterozygous mutations in WDR19 in a Norwegian family with Sensenbrenner syndrome. In a Dutch family with the clinically overlapping Jeune syndrome, a homozygous missense mutation in the same gene was found. Both families displayed a nephronophthisis-like nephropathy. Independently, we also identified compound heterozygous WDR19 mutations by exome sequencing in a Moroccan family with isolated nephronophthisis. WDR19 encodes IFT144, a member of the intraflagellar transport (IFT) complex A that drives retrograde ciliary transport. We show that IFT144 is absent from the cilia of fibroblasts from one of the Sensenbrenner patients and that ciliary abundance and morphology is perturbed, demonstrating the ciliary pathogenesis. Our results suggest that isolated nephronophthisis, Jeune, and Sensenbrenner syndromes are clinically overlapping disorders that can result from a similar molecular cause.

Control of the Wnt pathways by nephrocystin-4 is required for morphogenesis of the zebrafish pronephros

Nephronophthisis is a hereditary nephropathy characterized by interstitial fibrosis and cyst formation. It is caused by mutations in NPHP genes encoding the ciliary proteins, nephrocystins. In this paper, we investigate the function of nephrocystin-4, the product of the nphp4 gene, in vivo by morpholino-mediated knockdown in zebrafish and in vitro in mammalian kidney cells. Depletion of nephrocystin-4 results in convergence and extension defects, impaired laterality, retinal anomalies and pronephric cysts associated with alterations in early cloacal morphogenesis. These defects are accompanied by abnormal ciliogenesis in the cloaca and in the laterality organ. We show that nephrocystin-4 is required for the elongation of the caudal pronephric primordium and for the regulation of cell rearrangements during cloaca morphogenesis. Moreover, depletion of either inversin, the product of the nphp2 gene, or of the Wnt-planar cell polarity (PCP) pathway component prickle2 increases the proportion of cyst formation in nphp4-depleted embryos. Nephrocystin-4 represses the Wnt-β-catenin pathway in the zebrafish cloaca and in mammalian kidney cells in culture. In these cells, nephrocystin-4 interacts with inversin and dishevelled, and regulates dishevelled stability and subcellular localization. Our data point to a function of nephrocystin-4 in a tight regulation of the Wnt-β-catenin and Wnt-PCP pathways, in particular during morphogenesis of the zebrafish pronephros. Moreover, they highlight common signalling functions for inversin and nephrocystin-4, suggesting that these two nephrocystins are involved in common physiopathological mechanisms.

RET and GDNF mutations are rare in fetuses with renal agenesis or other severe kidney development defects

BACKGROUND

The RET/GDNF signalling pathway plays a crucial role during development of the kidneys and the enteric nervous system. In humans, RET activating mutations cause multiple endocrine neoplasia, whereas inactivating mutations are responsible for Hirschsprung disease. RET mutations have also been reported in fetuses with renal agenesis, based on analysis of a small series of samples.

OBJECTIVE AND METHODS

To characterise better the involvement of RET and GDNF in kidney development defects, a series of 105 fetuses with bilateral defects, including renal agenesis, severe hypodysplasia or multicystic dysplastic kidney, was studied. RET and GDNF coding sequences, evolutionary conserved non-coding regions (ECRs) in promoters, 3'UTRs, and RET intron 1 were analysed. Copy number variations at these loci were also investigated.

RESULTS

The study identified: (1) a low frequency (<7%) of potential mutations in the RET coding sequence, with inheritance from the healthy father for four of them; (2) no GDNF mutation; (3) similar allele frequencies in patients and controls for most single nucleotide polymorphism variants, except for RET intron 1 variant rs2506012 that was significantly more frequent in affected fetuses than in controls (6% vs 2%, p=0.01); (4) distribution of the few rare RET variants unidentified in controls into the various 5'-ECRs; (5) absence of copy number variations.

CONCLUSION

These results suggest that genomic alteration of RET or GDNF is not a major mechanism leading to renal agenesis and other severe kidney development defects. Analysis of a larger series of patients will be necessary to validate the association of the RET intron 1 variant rs2506012 with renal development defects.

Colorectal and anal neoplasms following liver transplantation

OBJECTIVE

Liver transplantation (LT) is the treatment of choice for end-stage liver disease. The required immunosuppression increases the risk for developing malignancies. Some viruses play a crucial role. Data on neoplasms of the colon, rectum and anus in LT are limited.

METHOD

A retrospective evaluation of the incidence and clinical course of colorectal and anal malignancies and colonic polyps in a series of 467 consecutive LTs in 402 individuals between 1998 and 2001 was performed. Standard immunosuppression included Tacrolimus, Mycophenolic acid and steroids.

RESULTS

During a median follow up of 5.2 years, three colon adenocarcinomas, one EBV associated cecal posttransplant lymphoproliferative tumour and two HPV associated anal tumours were identified. Pre-LT colonoscopy was performed in 161 patients (40%), and of 153 evaluable individuals, 53 (34.9%) had polyps. Colonoscopy was performed in 186 patients (46.3%) median 14.8 (range 0.2-77.8) months post-LT and 55 (29.3%) had polyps. Post-LT adenomatous polyps were detected in 47.3% of patients with pre-LT polyps vs 6.7% of patients without pre-LT polyps (P < 0.001). Patients with alcoholic liver disease had a significantly higher rate of adenoma formation (50.0% vs 11.1%, P < 0.001). No patient died from colorectal/anal malignancy.

CONCLUSION

The incidence of metachronous and new polyp formation in our study is similar to people who are not immunocompromised, but subgroups are at increased risk. Viral-associated malignancies, including post-transplant lymphoproliferative disorders and anal cancer, are important entities in the LT population suggesting that complete screening of the colon, rectum and anus including pre-LT and post-LT colonoscopy should be utilized.

Management of Wilms tumors in Drash and Frasier syndromes

BACKGROUND

Children with WT1 gene-related disorders such as Denys-Drash syndrome (DDS) and Frasier syndrome (FS) are at increased risk of Wilms tumor and end-stage renal disease. We investigated whether Wilms tumors in these patients displayed a specific phenotype or behavior and whether nephron-sparing surgery was beneficial.

PROCEDURE

We retrospectively studied all patients with DDS, FS, or other WT1 mutations treated at our institutions between 1980 and 2007.

RESULTS

We identified 20 patients, of whom 18 had benign or malignant tumors. Wilms tumors occurred in 15 patients, being unilateral in 10 and bilateral in 5 (20 tumors). Median age at Wilms tumor diagnosis was 9 months. No patients had metastases. According to the International Society of Pediatric Oncology Working Classification, there were 19 intermediate-risk tumors and one high-risk tumor; no tumor was anaplastic. In patients with nephropathy who underwent unilateral nephrectomy for Wilms tumor or nephron-sparing surgery for bilateral Wilms tumor, mean time to dialysis was 11 or 9 months, respectively. Other tumors included three gonadoblastomas (in two patients), one retroperitoneal soft-tissue tumor, and one transitional cell papilloma of the bladder. Two patients, both with stage I Wilms tumor, died from end-stage renal disease-related complications. The median follow-up time for the 18 survivors was 136 months (range, 17-224 months).

CONCLUSION

Most Wilms tumors in children with WT1-related disorders were early-stage and intermediate-risk tumors, with a young age at diagnosis. In patients without end-stage renal disease, nephron-sparing surgery should be considered for delaying the onset of renal failure.

High cyclin E staining index in blastemal, stromal or epithelial cells is correlated with tumor aggressiveness in patients with nephroblastoma

Purpose

Identifying among nephroblastoma those with a high propensity for distant metastases using cell cycle markers: cyclin E as a regulator of progression through the cell cycle and Ki-67 as a tumor proliferation marker, since both are often deregulated in many human malignancies.

Methodology/Principal Findings

A staining index (SI) was obtained by immunohistochemistry using anti-cyclin E and anti-Ki-67 antibodies in paraffin sections of 54 postchemotherapy nephroblastoma including 42 nephroblastoma without metastasis and 12 with metastases. Median cyclin E and Ki-67 SI were 46% and 33% in blastemal cells, 30% and 10% in stromal cells, 37% and 29.5% in epithelial cells. The highest values were found for anaplastic nephroblastoma. A correlation between cyclin E and Ki-67 SI was found for the blastemal component and for the epithelial component. Univariate analysis showed prognostic significance for metastases with cyclin E SI in stromal cells, epithelial cells and blastemal cells (p = 0.03, p = 0.01 and p = 0.002, respectively) as well as with Ki-67 SI in blastema (p<10⁻⁴). The most striking data were that both cyclin E SI and blastemal Ki-67 SI discriminated between patients with metastases and patients without metastasis among intermediate-risk nephroblastoma.

Conclusions

Our findings show that a high cyclin E SI in all components of nephroblastoma is correlated with tumor aggressiveness and metastases, and that assessment of its expression may have prognostic value in the categorization of nephroblastoma.

Small Glomeruli in WAGR (Wilms Tumor, Aniridia, Genitourinary Anomalies and Mental Retardation) Syndrome

BACKGROUND

Wilms tumor, aniridia, genitourinary anomalies, and mental retardation (WAGR) syndrome is a genetic disorder caused by a deletion of band 11p13, which results in the loss of 1 allele of the Wilms tumor suppressor gene (WT1). It is not classically associated with nephropathies, but increased rates of renal failure are reported. Denys-Drash syndrome (DDS), caused by mutations in the WT1 gene affecting the third or second zinc finger, is characterized by a triad of glomerulopathy progressing rapidly to end-stage renal disease, male hermaphroditism, and Wilms tumor. In patients with DDS, small glomeruli were observed.

METHODS

We reviewed histological findings of nontumoral kidney samples of 7 patients with WAGR syndrome at the time of tumor surgery.

RESULTS

Median glomerular diameter was 110 +/- 37 microm in patients with WAGR syndrome versus 125 +/- 18.5 microm in controls (P < 0.0001).

CONCLUSION

The presence of small glomeruli in patients with WAGR syndrome, as in those with DDS, suggests a specific defect of WT1 function in development and a specific role of WT1 allele loss in the development of renal failure in these patients.

Frequent overexpression of cyclin D2/cyclin-dependent kinase 4 in Wilms' tumor

The expression status of the three cyclin D genes (CCND1, CCND2 and CCND3), the two cyclin D-dependent kinase genes (CDK4 and CDK6) and the p16(INK4a) gene was studied in a series of 47 Wilms' tumors, 16 normal mature kidneys and two fetal kidneys. We showed predominant overexpression of CCND2 and CDK4 compared to CCND1/D3 and CDK6 respectively. We found a specific correlation between relapse and CDK4 overexpression, but not CDK6 overexpression. We did not identify any methylation of the p16(INK4a) promoter. This suggests that dysregulation of CCND2 and CDK4 plays a specific role in WT tumorigenesis.

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.

Cadherins in Wilms' tumor: E-cadherin expression despite absence of WT1

Loss of heterozygosity of chromosome 16q occurs in 17-25% of Wilms' tumors. Two cadherin genes mapping to 16q22 were chosen as candidate gens: E-CAD, encoding epithelial cadherin, because it is involved in kidney development and it was recently reported to be a WT1 target; and KSP-CAD because it encodes a kidney-specific cadherin. By RT-PCR analysis in a series of 39 Wilms' tumors, we identified a very low expression of E-CAD and KSP-CAD in 72% and 95% of the tumors, respectively. To ascertain whether down-expression of these genes could be related to WT1 alterations in tumors, we looked for a relationship between WT1 and CAD expression. Our data suggest (i) the existence of alternative mechanisms for regulating E-CAD expression, and (ii) that E-CAD does not belong to the WT1 pathway that is altered in Wilms' tumorigenesis.

Changes in WT1 splicing are associated with a specific gene expression profile in Wilms' tumour

Wilms' tumour (WT) or nephroblastoma is the most frequent kidney cancer in children. In a previous study, we reported alterations to WT1 transcription in 90% of WT tested, with decreased exon 5 +/- isoform ratio being the most frequent alteration (56% of WT). We now report an approach based on cDNA profiling of tumour pools to identify genes likely to be dysregulated in association with a decreased WT1 exon 5 +/- ratio. We compared the expression profiles of pools of tumours classified according to whether this isoform imbalance was present (five tumours) or not (four tumours), using Atlas Cancer cDNA expression arrays. Fourteen of 588 genes tested displayed specific up-regulation (CCND2, PCNA, N-MYC, E2F3, TOP2A, PAK1, DCC and PCDH2) or down-regulation (VEGF, IGFBP5, TIMP3, ARHB, C-FOS and CD9) in the pool of tumours with decreased exon 5 +/- ratio. These results were validated by RT-PCR analysis of four genes (CCND2, PCNA, VEGF and IGFBP5). We extended the analysis of VEGF expression to 51 tumours by real-time RT-PCR and ascertained differential expression of this gene associated with WT1 expression pattern. Moreover, our results suggest that the VEGF expression level may be of prognosis relevance for relapsed patients.

Profiling of differential gene expression in Wilms tumor by cDNA expression array

In order to identify genes or pathways involved in Wilms tumor etiology, we used the Atlas Cancer cDNA expression array to compare the gene expression profiles of five tumors, one Wilms tumor cell line (SK-NEP1), and normal mature and fetal kidneys. Of 588 genes tested, 153 had a different expression pattern in tumors compared with mature kidney. Ninety-six genes were differentially expressed in tumors compared with both normal mature and fetal kidney, and 57 genes had expression profiles similar to that of fetal kidney, which may reflect the developmental stage of the tumor cells. Comparison of the expression patterns of tumors shows that only 13% of the differentially expressed genes are constantly up- or downregulated in the five tumors tested, and this provides molecular evidence of tumor heterogeneity. We then confirmed the differential expression by an independent method, using quantitative reverse transcriptase polymerase chain reaction for two of the differentially expressed genes, MMP-14 and cyclin D2. Analysis of expression levels in a panel of 40 tumors showed that 30% overexpressed MMP-14 and 80% overexpressed cyclin D2. Profiling of gene expression using cDNA arrays in a large tumor panel will ultimately lead to the molecular classification of tumors, the identification of prognosis markers, and the design of targeted therapy.

WT1 splicing alterations in Wilms' tumors

Hereditary and sporadic forms of tumors are generally related to germ-line and somatic mutations of the same tumor suppressor gene. Unexpectedly, in Wilms' tumor, somatic mutations of the WT1 gene were found only occasionally in sporadic cases, although constitutional mutations of this gene are clearly associated with predisposition. It has been suggested that abnormal splicing may be another mode of somatic WT1 alteration. However, this idea was based on the analysis of a small series of tumors, precluding accurate evaluation of the frequency of such changes. To investigate WT1 changes at the somatic level in more detail, we analyzed the levels of the four isoform transcripts produced by alternative splicing events in a large series of 50 tumors, normal mature kidneys, and fetal kidneys. We characterized splicing alterations in 63% of sporadic Wilms' tumors. Moreover, taking into account the decreased and increased overall levels of WT1 mRNA, the percentage of sporadic tumors with changes in WT1 expression reached 90%. Whether and how these alterations of expression play a role in the tumorigenic process remain to be evaluated.

Spectrum of hSNF5/INI1 somatic mutations in human cancer and genotype-phenotype correlations

The hSNF5/INI1 gene which encodes a member of the SWI/SNF chromatin ATP-dependent remodeling complex, is a new tumor suppressor gene localized on chromosome 22q11.2 and recently shown to be mutated in malignant rhabdoid tumors. We have searched for hSNF5/INI1 mutations in 229 tumors of various origins using a screening method based on denaturing high-performance liquid chromatography. A total of 31 homozygous deletions and 36 point alterations were identified. Point mutations were scattered along the coding sequence and included 15 nonsense, 15 frameshift, three splice site, two missense and one editing mutations. Mutations were retrieved in most rhabdoid tumors, whatever their sites of occurrence, indicating the common pathogenetic origin of these tumors. Recurrent hSNF5/INI1 alterations were also observed in choroid plexus carcinomas and in a subset of central primitive neuroectodermal tumors (cPNETs) and medulloblastomas. In contrast, hSNF5/INI1 point mutations were not detected in breast cancers, Wilms' tumors, gliomas, ependymomas, sarcomas and other tumor types, even though most analyzed cases harbored loss of heterozygosity at 22q11.2 loci. These results suggest that rhabdoid tumors, choroid plexus carcinomas and a subset of medulloblastomas and cPNETs share common pathways of oncogenesis related to hSNF5/INI1 alteration and that hSNF5/INI1 mutations define a genetically homogeneous family of highly aggressive cancers mainly occurring in young children and frequently, but not always, exhibiting a rhabdoid phenotype.

WT1 and PAX-2 podocyte expression in Denys-Drash syndrome and isolated diffuse mesangial sclerosis

Denys-Drash syndrome is a rare disorder of urogenital development characterized by the association of early onset glomerulopathy caused by diffuse mesangial sclerosis, gonadal dysgenesis leading to pseudohermaphroditism in males, and a high risk of developing Wilms' tumor. The syndrome is caused by dominant negative point mutations in the WT1 gene that encodes a tumor suppressor transcription factor normally expressed in podocytes. Mutations usually affect the zinc fingers of the WT1 protein. The basic defect is unknown in most cases of isolated diffuse mesangial sclerosis, a disease characterized by the same glomerular changes as in Denys-Drash syndrome but possibly transmitted as an autosomal recessive trait. Here we show that the distribution of WT1 is abnormal in most patients with Denys-Drash syndrome : WT1 nuclear staining of podocytes is decreased or absent. This finding is consistent with the decreased DNA binding capacity of the mutated protein. One target gene of WT1 is PAX2, the expression of which is down-regulated in podocytes during early stages of nephrogenesis. We demonstrate that WT1 mislocalization is associated with abnormal podocyte expression of PAX2 protein and RNA. We suggest that persistent expression of PAX2 is likely to result from the loss of WT1 dependent transcriptional repression and may participate in the pathological mechanisms leading to glomerular dysfunction. Abnormal distribution of WT1 and PAX2 was also observed in isolated diffuse mesangial sclerosis suggesting that a defect in WT1 could also be operative in isolated diffuse mesangial sclerosis. Primary involvement of PAX2 is an alternative hypothesis because persistent expression of PAX2 in transgenic mice is associated with the occurrence of early and severe glomerulopathy.

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.

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.