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Zebrafish pronephros tubulogenesis and epithelial identity maintenance are reliant on the polarity proteins Prkc iota and zeta.

ABSTRACT: The zebrafish pronephros provides an excellent in vivo system to study the mechanisms of vertebrate nephron development. When and how renal progenitors in the zebrafish embryo undergo tubulogenesis to form nephrons is poorly understood, but is known to involve a mesenchymal to epithelial transition (MET) and the acquisition of polarity. Here, we determined the precise timing of these events in pronephros tubulogenesis. As the ternary polarity complex is an essential regulator of epithelial cell polarity across tissues, we performed gene knockdown studies to assess the roles of the related factors atypical protein kinase C iota and zeta (prkc?, prkc?). We found that prkc? and prkc? serve partially redundant functions to establish pronephros tubule epithelium polarity. Further, the loss of prkc? or the combined knockdown of prkc?/? disrupted proximal tubule morphogenesis and podocyte migration due to cardiac defects that prevented normal fluid flow to the kidney. Surprisingly, tubule cells in prkc?/? morphants displayed ectopic expression of the transcription factor pax2a and the podocyte-associated genes wt1a, wt1b, and podxl, suggesting that prkc?/? are needed to maintain renal epithelial identity. Knockdown of genes essential for cardiac contractility and vascular flow to the kidney, such as tnnt2a, or elimination of pronephros fluid output through knockdown of the intraflagellar transport gene ift88, was not associated with ectopic pronephros gene expression, thus suggesting a unique role for prkc?/? in maintaining tubule epithelial identity separate from the consequence of disruptions to renal fluid flow. Interestingly, knockdown of pax2a, but not wt1a, was sufficient to rescue ectopic tubule gene expression in prkc?/? morphants. These data suggest a model in which the redundant activities of prkc? and prkc? are essential to establish tubule epithelial polarity and also serve to maintain proper epithelial cell type identity in the tubule by inhibiting pax2a expression. These studies provide a valuable foundation for further analysis of MET during nephrogenesis, and have implications for understanding the pathways that affect nephron epithelial cells during kidney disease and regeneration.

SUBMITTER: Gerlach GF

PROVIDER: S-EPMC4261075 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Zebrafish pronephros tubulogenesis and epithelial identity maintenance are reliant on the polarity proteins Prkc iota and zeta.

Gerlach Gary F GF Wingert Rebecca A RA

Developmental biology 20141014 2

The zebrafish pronephros provides an excellent in vivo system to study the mechanisms of vertebrate nephron development. When and how renal progenitors in the zebrafish embryo undergo tubulogenesis to form nephrons is poorly understood, but is known to involve a mesenchymal to epithelial transition (MET) and the acquisition of polarity. Here, we determined the precise timing of these events in pronephros tubulogenesis. As the ternary polarity complex is an essential regulator of epithelial cell ...[more]

PMID: 25446529

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Project description:Key Points During glomerular capillary formation, endothelial cells sprout from the dorsal aorta and surround the bilateral glomerular primordia. Blood flow maintains tubular structures of the capillaries surrounding the glomerular primordia. Blood flow also promotes glomerular incorporation of blood vessels by inducing glomerular remodeling. Visual Abstract Background The renal glomerulus is a tuft of capillaries in Bowman’s capsule and functions as a blood-filtration unit in the kidney. The unique glomerular capillary tuft structure is relatively conserved through vertebrate species. However, the morphogenetic mechanism governing glomerular capillary tuft formation remains elusive. Methods To clarify how glomerular capillaries develop, we analyzed glomerular capillary formation in the zebrafish pronephros by exploiting fluorescence-based bio-imaging technology. Results During glomerular capillary formation in the zebrafish pronephros, endothelial cells initially sprouted from the dorsal aorta and formed the capillaries surrounding the bilateral glomerular primordia in response to podocyte progenitor-derived vascular endothelial growth factor-A. After formation, blood flow immediately occurred in the glomerular primordia-associated capillaries, while in the absence of blood flow, they were transformed into sheet-like structures enveloping the glomerular primordia. Subsequently, blood flow induced formation of Bowman’s space at the lateral sides of the bilateral glomerular primordia. Concomitantly, podocyte progenitors enveloped their surrounding capillaries while moving toward and coalescing at the midline. These capillaries then underwent extensive expansion and remodeling to establish a functional glomerular capillary tuft. However, stopping blood flow inhibited the remodeling of bilateral glomerular primordia, which therefore remained unvascularized but covered by the vascular sheets. Conclusions We delineated the morphogenetic processes governing glomerular capillary tuft formation in the zebrafish pronephros and demonstrated crucial roles of blood flow in its formation. Blood flow maintains tubular structures of the capillaries surrounding the glomerular primordia and promotes glomerular incorporation of these vessels by inducing the remodeling of glomerular primordia.

Dataset Information

Zebrafish pronephros tubulogenesis and epithelial identity maintenance are reliant on the polarity proteins Prkc iota and zeta.

Publications

Zebrafish pronephros tubulogenesis and epithelial identity maintenance are reliant on the polarity proteins Prkc iota and zeta.

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