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Notch signaling, wt1 and foxc2 are key regulators of the podocyte gene regulatory network in Xenopus.

ABSTRACT: Podocytes are highly specialized cells in the vertebrate kidney. They participate in the formation of the size-exclusion barrier of the glomerulus/glomus and recruit mesangial and endothelial cells to form a mature glomerulus. At least six transcription factors (wt1, foxc2, hey1, tcf21, lmx1b and mafb) are known to be involved in podocyte specification, but how they interact to drive the differentiation program is unknown. The Xenopus pronephros was used as a paradigm to address this question. All six podocyte transcription factors were systematically eliminated by antisense morpholino oligomers. Changes in the expression of the podocyte transcription factors and of four selected markers of terminal differentiation (nphs1, kirrel, ptpru and nphs2) were analyzed by in situ hybridization. The data were assembled into a transcriptional regulatory network for podocyte development. Although eliminating the six transcription factors individually interfered with aspects of podocyte development, no single gene regulated the entire differentiation program. Only the combined knockdown of wt1 and foxc2 resulted in a loss of all podocyte marker gene expression. Gain-of-function studies showed that wt1 and foxc2 were sufficient to increase podocyte gene expression within the glomus proper. However, the combination of wt1, foxc2 and Notch signaling was required for ectopic expression in ventral marginal zone explants. Together, this approach demonstrates how complex interactions are required for the correct spatiotemporal execution of the podocyte gene expression program.

SUBMITTER: White JT

PROVIDER: S-EPMC2867321 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Notch signaling, wt1 and foxc2 are key regulators of the podocyte gene regulatory network in Xenopus.

White Jeffrey T JT White Jeffrey T JT Zhang Bo B Cerqueira Débora M DM Tran Uyen U Wessely Oliver O

Development (Cambridge, England) 20100428 11

Podocytes are highly specialized cells in the vertebrate kidney. They participate in the formation of the size-exclusion barrier of the glomerulus/glomus and recruit mesangial and endothelial cells to form a mature glomerulus. At least six transcription factors (wt1, foxc2, hey1, tcf21, lmx1b and mafb) are known to be involved in podocyte specification, but how they interact to drive the differentiation program is unknown. The Xenopus pronephros was used as a paradigm to address this question. A ...[more]

PMID: 20431116

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Project description:Analysis of epithelial explants injected with the intracellular domain of Notch (ICD) to block the formation of multi-ciliate and proton secreting cells or with dominant negative human Mastermind (HMM) to induce the formation of ectopic multi-ciliate and proton secreting cells. Results show which genes are up or down-regulated when HMM is compared to ICD. Specialized epithelial cells in the amphibian skin play important roles in ion transport, but how they arise developmentally is largely unknown. Here we show that proton-secreting cells (PSCs) differentiate in the X. laevis larval skin soon after gastrulation, based on the expression of “kidney” specific form of the H+v-ATPase that localizes to the plasma membrane, orthologs of the Cl-/HCO3- antiporters ae1 and pendrin, and two isoforms of carbonic anhydrase. Like PSCs in other species, we show that the expression of these genes is likely to be driven by an ortholog of foxi1, which is also sufficient to promote the formation of PSC precursors. Strikingly, the PSCs form in the skin as two distinct subtypes that resemble the alpha- and beta-intercalated cells of the kidney. The alpha-subtype expresses ae1 and localizes H+v-ATPases to the apical plasma membrane, whereas the beta-subtype expresses pendrin and localizes the H+v-ATPase cytosolically or basolaterally. These two subtypes are specified during early differentiation, and can be distinguished based on the expression of ubp1, a transcription factor in the grainyhead family. Finally, we show that ectopic expression ubp1 is sufficient to promote the differentiation of beta-subtypes while repressing alpha-subtypes. These results have implications for how PSCs are specified in vertebrates and become functionally heterogeneous. 2-cell stage Xenopus embryos were injected with synthetic mRNA encoding ICD or HMM. At stage 9/10 the presumptive ectoderm was cut off the embryo and cultured on a fibronectin coated coverslip. At stage 22 RNA was harvested from explants and used as the starting material for arrays.

Dataset Information

Notch signaling, wt1 and foxc2 are key regulators of the podocyte gene regulatory network in Xenopus.

Publications

Notch signaling, wt1 and foxc2 are key regulators of the podocyte gene regulatory network in Xenopus.

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