p53 limits the self-renewing ability of a variety of stem cells. Here, contrary to its classical role in restraining cell proliferation, we demonstrate a divergent function of p53 in maintenance of self-renewal of the nephron progenitor population in the embryonic mouse kidney. p53-null nephron progenitor cells (NPC) exhibit progressive loss of the self-renewing progenitor niche in the cap mesenchyme, identified by Cited1 and Six2 expression, and loss of cap integrity. Nephron endowment is regulated by NPC availability and their differentiation to nephrons. Quantitatively, the Six2p53-/- cap has 30% fewer Six2GFP+ cells. While the apoptotic index is unchanged the proliferation index is significantly lower, in accordance with cell cycle analysis data showing less mutant Six2p53-/-;GFP+ cells in S and G2/M phases in comparison to Six2p53+/+;GFP+ cells. The mutant kidneys also show nephron deficit and decreased Fgf8 expression. To investigate the underlying changes in gene expression in the cap mesenchyme that contribute to the Six2p53-/- phenotype, we utilized RNA-Seq for transcriptome comparison. Top biological processes affected by p53 loss are development and morphogenesis, cell adhesion/migration, cell survival and metabolism. Cells from the mutant CM showed increased cellular ROS levels as well as deregulated expression of energy metabolism and mitochondrial genes suggesting metabolic dysfunction. Adhesion defects are visualized by decreased immunostaining of adhesion marker NCAM, and may possibly contribute to the differentiation defect as well. Altogether our data suggest a novel role for p53 in enabling self-renewal of the NPC and preservation of the progenitor niche, and thus regulating nephron endowment. Overall design: mRNA profiles of wild-type (WT) and conditional p53 knockout (KO) of Six2+ mouse nephron progenitor cells (NPC) at embryonic day 15.5
p53 Enables metabolic fitness and self-renewal of nephron progenitor cells.
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View SamplesForkhead transcription factors are essential for diverse processes in early embryonic development and organogenesis. Foxd1 is required during kidney development and its inactivation results in failure of nephron progenitor cell differentiation. Foxd1 is expressed in interstitial cells adjacent to nephron progenitor cells, suggesting an essential role for the progenitor cell niche in nephrogenesis. To better understand how cortical interstitial cells in general, and FOXD1 in particular, influence the progenitor cell niche, we examined the differentiation states of two progenitor cell subtypes in Foxd1-/- tissue. We found that while nephron progenitor cells are retained in a primitive CITED1-expressing compartment, cortical interstitial cells prematurely differentiate. To identify pathways regulated by FOXD1, we used microarray analysis and screened for target genes by comparison of Foxd1 null and wild type tissues.
FOXD1 promotes nephron progenitor differentiation by repressing decorin in the embryonic kidney.
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