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Expression of WT1 protein in fetal kidneys and Wilms tumors
G R Grubb1, K Yun, B R Williams
1Department of Pathology, University of Otago Medical School, Dunedin, New Zealand.
Background:
Wilms' tumors are embryonic kidney neoplasms believed to result from a perturbation in the development of the metanephric blastema. A candidate gene (WT1) has been cloned that has been found to be mutated in a number of Wilms' tumors, consistent with its suggested role as a tumor suppressor gene. This gene has been shown to be essential to the normal development of the embryonic kidney.
Experimental Design:
The aim of the present study was to provide information on the level at which the WT1 gene is regulated. Immunohistochemistry, immunofluorescence, and in situ hybridization was used to examine the localization of WT1 protein and mRNA, respectively. We further used immunofluorescence to examine the WT1 expression in seven Wilms' tumors.
Results:
In fetal kidneys, WT1 transcripts were detected with increasing levels of hybridization signal in induced blastemal cells, renal vesicles, pre-podocytes of comma- and S-shaped bodies, and podocytes of glomeruli. WT1 protein, detected by an antibody raised against recombinant WT1 fusion protein, was seen in the nuclei of the same cell types mentioned above, and the staining intensity was comparable to the levels of WT1 transcripts. Immunostaining of seven Wilms tumors demonstrated that WT1 protein was expressed only in neoplastic structures whose normal counterparts also expressed WT1 protein. Neither stromal cells nor rhabdomyoblasts contained WT1 protein.
Conclusions:
The results show that in fetal kidney, WT1 transcripts and protein are coordinately expressed, and strongly associated with differentiation of metanephric blastemal cells into epithelial cells. Furthermore, the finding that WT1 transcripts and protein are coordinately expressed, suggests that WT1 gene expression is primarily regulated at the level of transcription.
Insights
The WT1 gene is crucial for embryonic kidney development and cell differentiation. Its expression in Wilms tumors suggests a role in regulating cell growth and development.
Area of Science:
- Developmental biology
- Molecular oncology
Background:
- Wilms tumors are embryonic kidney cancers linked to metanephric blastema development.
- The WT1 gene is a candidate tumor suppressor, essential for normal embryonic kidney development.
Purpose of the Study:
- To investigate the regulatory mechanisms of the WT1 gene.
- To examine WT1 gene and protein expression in developing kidneys and Wilms tumors.
Main Methods:
- Immunohistochemistry, immunofluorescence, and in situ hybridization were employed.
- WT1 protein and mRNA localization and expression levels were analyzed.
Main Results:
- WT1 expression increased with differentiation in fetal kidney cells, from blastema to podocytes.
- WT1 protein and mRNA levels were coordinately expressed in fetal kidneys.
- WT1 protein was detected in Wilms tumors within cell types mirroring normal WT1 expression patterns.
Conclusions:
- WT1 gene expression is tightly linked to the differentiation of metanephric blastemal cells into epithelial cells.
- WT1 gene regulation appears to occur primarily at the transcriptional level.