The von Hippel-Lindau gene is required to maintain renal proximal tubule and glomerulus integrity in zebrafish larvae

Background: von Hippel-Lindau (VHL) disease is characterized by the development of benign and malignant tumours in many organ systems, including renal cysts and clear cell renal cell carcinoma. It is not completely understood what underlies the development of renal pathology, and the use of murine Vhl models has been challenging due to limitations in disease conservation. We previously described a zebrafish model bearing inactivating mutations in the orthologue of the human VHL gene. Methods: We used histopathological and functional assays to investigate the pronephric and glomerular developmental defects in vhl mutant zebrafish, supported by human cell culture assays. Results: Here, we report that vhl is required to maintain pronephric tubule and glomerulus integrity in zebrafish embryos. vhl mutant glomeruli are enlarged, cxcr4a+ capillary loops are dilated and the Bowman space is widened. While we did not observe pronephric cysts, the cells of the proximal convoluted and anterior proximal straight tubule are enlarged, periodic acid schiff (PAS) and Oil Red O positive, and display a clear cytoplasm after hematoxylin and eosine staining. Ultrastructural analysis showed the vhl–/– tubule to accumulate large numbers of vesicles of variable size and electron density. Microinjection of the endocytic fluorescent marker AM1–43 in zebrafish embryos revealed an accumulation of endocytic vesicles in the vhl mutant pronephric tubule, which we can recapitulate in human cells lacking VHL. Conclusions: Our data indicates that vhl is required to maintain pronephric tubule and glomerulus integrity during zebrafish development, and suggests a role for VHL in endocytic vesicle trafficking

Mutations in LRRC50 Predispose Zebrafish and Humans to Seminomas

Seminoma is a subclass of human testicular germ cell tumors (TGCT), the most frequently observed cancer in young men with a rising incidence. Here we describe the identification of a novel gene predisposing specifically to seminoma formation in a vertebrate model organism. Zebrafish carrying a heterozygous nonsense mutation in Leucine-Rich Repeat Containing protein 50 (lrrc50 also called dnaaf1), associated previously with ciliary function, are found to be highly susceptible to the formation of seminomas. Genotyping of these zebrafish tumors shows loss of heterozygosity (LOH) of the wild-type lrrc50 allele in 44.4% of tumor samples, correlating with tumor progression. In humans we identified heterozygous germline LRRC50 mutations in two different pedigrees with a family history of seminomas, resulting in a nonsense Arg488* change and a missense Thr590Met change, which show reduced expression of the wild-type allele in seminomas. Zebrafish in vivo complementation studies indicate the Thr590Met to be a loss-of-function mutation. Moreover, we show that a pathogenic Gln307Glu change is significantly enriched in individuals with seminoma tumors (13% of our cohort). Together, our study introduces an animal model for seminoma and suggests LRRC50 to be a novel tumor suppressor implicated in human seminoma pathogenesis

TCF21 hypermethylation regulates renal tumor cell clonogenic proliferation and migration

We recently identified hypermethylation at the gene promoter of transcription factor 21 (TCF21) in clear cell sarcoma of the kidney (CCSK), a rare pediatric renal tumor. TCF21 is a transcription factor involved in tubular epithelial development of the kidney and is a candidate tumor suppressor. As there are no in vitro models of CCSK, we employed a well-established clear cell renal cell carcinoma (ccRCC) cell line, 786-O, which also manifests high methylation at the TCF21 promoter, with consequent low TCF21 expression. The tumor suppressor function of TCF21 has not been functionally addressed in ccRCC cells; we aimed to explore the functional potential of TCF21 expression in ccRCC cells in vitro. 786-O clones stably transfected with either pBABE-TCF21-HA construct or pBABE vector alone were functionally analyzed. We found that ectopic expression of TCF21 in 786-O cells results in a trend toward decreased cell proliferation (not significant) and significantly decreased migration compared with mock-transfected 786-O cells. Although the number of colonies established in colony formation assays was not different between 786-O clones, colony size was significantly reduced in 786-O cells expressing TCF21. To investigate whether the changes in migration were due to epithelial-to-mesenchymal transition changes, we interrogated the expression of selected epithelial and mesenchymal markers. Although we observed upregulation of mRNA and protein levels of epithelial marker E-cadherin in clones overexpressing TCF21, this did not result in surface expression of E-cadherin as measured by fluorescence-activated cell sorting and immunofluorescence. Furthermore, mRNA expression of the mesenchymal markers vimentin (VIM) and SNAI1 was not significantly decreased in TCF21-expressing 786-O cells, while protein levels of VIM were markedly decreased. We conclude that re-expression of TCF21 in renal cancer cells that have silenced their endogenous TCF21 locus through hypermethylation results in reduced clonogenic proliferation, reduced migration, and reduced mesenchymal-like characteristics, suggesting a tumor suppressor function for transcription factor 21

Een beschrijvend onderzoek: Patiënten met een armamputatie vergeleken met patiënten met armletsel(s), waarbij gebruik gemaakt is van de Disability of the Arm, Shoulder and Hand (DASH) Outcome Measure.

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