title: A Wnt7b-dependent pathway regulates the orientation of epithelial cell division and establishes the cortico-medullary axis of the mammalian kidney.
abstract: The mammalian kidney is organized into a cortex where primary filtration occurs, and a medullary region composed of elongated tubular epithelia where urine is concentrated. We show that the cortico-medullary axis of kidney organization and function is regulated by Wnt7b signaling. The future collecting duct network specifically expresses Wnt7b. In the absence of Wnt7b, cortical epithelial development is normal but the medullary zone fails to form and urine fails to be concentrated normally. The analysis of cell division planes in the collecting duct epithelium of the emerging medullary zone indicates a bias along the longitudinal axis of the epithelium. By contrast, in Wnt7b mutants, cell division planes in this population are biased along the radial axis, suggesting that Wnt7b-mediated regulation of the cell cleavage plane contributes to the establishment of a cortico-medullary axis. The removal of beta-catenin from the underlying Wnt-responsive interstitium phenocopies the medullary deficiency of Wnt7b mutants, suggesting a paracrine role for Wnt7b action through the canonical Wnt pathway. Wnt7b signaling is also essential for the coordinated growth of the loop of Henle, a medullary extension of the nephron that elongates in parallel to the collecting duct epithelium. These findings demonstrate that Wnt7b is a key regulator of the tissue architecture that establishes a functional physiologically active mammalian kidney.
authors.affiliation: Department of Molecular and Cellular Biology and Harvard Stem Cell Institute, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Yu
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Carroll
authors.forename: Jay
authors.initials: J
authors.lastname: Rajagopal
authors.forename: Akio
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Qun
authors.initials: Q
authors.lastname: Ren
authors.forename: Andrew P
authors.initials: AP
authors.lastname: McMahon
mesh_terms: D000818:Animals; D019521:Body Patterning; D002455:Cell Division; D050761:Cyclin-Dependent Kinase Inhibitor p57 / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology* / Q000378:metabolism; D005260:Female; D007672:Kidney Cortex / Q000196:embryology*; D007679:Kidney Medulla / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D008138:Loop of Henle / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D008322:Mammals / Q000196:embryology*; D051379:Mice; D009154:Mutation / Q000235:genetics; D009399:Nephrons / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D015398:Signal Transduction; D014513:Ureter / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism*
chemical_list: C493965:Cdkn1c protein, mouse; D050761:Cyclin-Dependent Kinase Inhibitor p57; D011518:Proto-Oncogene Proteins; D051153:Wnt Proteins; C095937:Wnt7b protein, mouse