The <b><i>von Hippel-Lindau</i></b> Gene Is Required to Maintain Renal Proximal Tubule and Glomerulus Integrity in Zebrafish Larvae

Abstract

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.

Inhibition of oxygen-sensing prolyl hydroxylases increases lipid accumulation in human primary tubular epithelial cells without inducing ER stress

“…However, beyond tumor models, the effects of HIF on lipid metabolism in the kidney are largely unknown. Recently, lipid accumulation was observed in proximal tubules of embryonic vhl-deficient zebrafish larvae (van Rooijen et al 2018). In our in vivo experiments, we found larger lipid deposits in proximal renal tubules of Phd2 ΔKsp mice than in wild-type littermates.…”

Tuberous sclerosis complex exhibits a new renal cystogenic mechanism

“…Such extracellular vesicles have been demonstrated to affect renal tubular changes in a von Hippel Lindau zebrafish model (van Rooijen et al. ). This extracellular vesicle initiating event has appeal because as the cyst develops, the tubular lumen increases in diameter and exponentially reduces the flow, thus increases the time for the extracellular vesicles to interact with intercalated cells.…”

Tsc Gene Locus Disruption and Differences in Renal Epithelial Extracellular Vesicles

“…Compared to EVs from control mIMCD3 cells, EVs from Tsc1 knockout cells facilitated a >80-fold increase in the expression of miRNA-99a-5p, whereas EVs from Tsc2 knockout cells completely silenced the expression of miRNA-99a-5p. miRNA-99a-5p plays an important role in the pathogenesis of various types of cancer such as ovarian cancer (Yoshimura et al, 2018), oral cancer (Shi et al, 2017), and bladder cancer (Tsai et al, 2018). Downregulation of miRNA-99a-5p may contribute to the more severe disease phenotype in TSC2associated disease than in TSC1-associated disease.…”

“…These miRNAs were most frequently identified by greater than three prediction tools. We also included a previously validated miRNA, miR-99a-5p, that reduces RPS6KB1 gene expression (Tsai et al, 2018). miR-99a-5p and miR-212-3p expression levels were lower (p < 0.01) in EVs shed by T2J cells, but T1G-EVs induced a significantly higher expression of both miRNAs (Figure 4C).…”