title: Stromally expressed β-catenin modulates Wnt9b signaling in the ureteric epithelium.
abstract: The mammalian kidney undergoes cell interactions between the epithelium and mesenchyme to form the essential filtration unit of the kidney, termed the nephron. A third cell type, the kidney stroma, is a population of fibroblasts located in the kidney capsule, cortex and medulla and is ideally located to affect kidney formation. We found β-catenin, a transcriptional co-activator, is strongly expressed in distinctive intracellular patterns in the capsular, cortical, and medullary renal stroma. We investigated β-catenin function in the renal stroma using a conditional knockout strategy that genetically deleted β-catenin specifically in the renal stroma cell lineage (β-cats-/-). β-cats-/- mutant mice demonstrate marked kidney abnormalities, and surprisingly we show β-catenin in the renal stroma is essential for regulating the condensing mesenchyme cell population. We show that the population of induced mesenchyme cells is significantly reduced in β-cats-/- mutants and exhibited decreased cell proliferation and a specific loss of Cited 1, while maintaining the expression of other essential nephron progenitor proteins. Wnt9b, the key signal for the induction of nephron progenitors, was markedly reduced in adjacent ureteric epithelial cells in β-cats-/-. Analysis of Wnt9b-dependent genes in the neighboring nephron progenitors was significantly reduced while Wnt9b-independent genes remained unchanged. In contrast mice overexpressing β-catenin exclusively in the renal stroma demonstrated massive increases in the condensing mesenchyme population and Wnt9b was markedly elevated. We propose that β-catenin in the renal stroma modulates a genetic program in ureteric epithelium that is required for the induction of nephron progenitors.
authors: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
authors: Felix J
authors: FJ
authors: Boivin
authors: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
authors: Sanjay
authors: S
authors: Sarin
authors: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
authors: Janice
authors: J
authors: Lim
authors: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
authors: Ashkan
authors: A
authors: Javidan
authors: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
authors: Bruno
authors: B
authors: Svajger
authors: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
authors: Hadiseh
authors: H
authors: Khalili
authors: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada.
authors: Darren
authors: D
authors: Bridgewater
mesh_terms: D000818:Animals; D005260:Female; D017353:Gene Deletion; D005786:Gene Expression Regulation; D055786:Gene Knockout Techniques; D007668:Kidney / Q000002:abnormalities / Q000166:cytology / Q000196:embryology; D008297:Male; D051379:Mice; D015398:Signal Transduction; D017154:Stromal Cells / Q000378:metabolism; D014513:Ureter / Q000378:metabolism*; D019459:Urothelium / Q000378:metabolism*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics* / Q000378:metabolism
chemical_list: D051153:Wnt Proteins; C515303:Wnt9b protein, mouse; D051176:beta Catenin