title: Wnt/beta-catenin signaling directs multiple stages of tooth morphogenesis.
abstract: Wnt/beta-catenin signaling plays key roles in tooth development, but how this pathway intersects with the complex interplay of signaling factors regulating dental morphogenesis has been unclear. We demonstrate that Wnt/beta-catenin signaling is active at multiple stages of tooth development. Mutation of beta-catenin to a constitutively active form in oral epithelium causes formation of large, misshapen tooth buds and ectopic teeth, and expanded expression of signaling molecules important for tooth development. Conversely, expression of key morphogenetic regulators including Bmp4, Msx1, and Msx2 is downregulated in embryos expressing the secreted Wnt inhibitor Dkk1 which blocks signaling in epithelial and underlying mesenchymal cells. Similar phenotypes are observed in embryos lacking epithelial beta-catenin, demonstrating a requirement for Wnt signaling within the epithelium. Inducible Dkk1 expression after the bud stage causes formation of blunted molar cusps, downregulation of the enamel knot marker p21, and loss of restricted ectodin expression, revealing requirements for Wnt activity in maintaining secondary enamel knots. These data place Wnt/beta-catenin signaling upstream of key morphogenetic signaling pathways at multiple stages of tooth development and indicate that tight regulation of this pathway is essential both for patterning tooth development in the dental lamina, and for controlling the shape of individual teeth.
authors.affiliation: Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.forename: Emily Y
authors.initials: EY
authors.lastname: Chu
authors.forename: Brenda
authors.initials: B
authors.lastname: Watt
authors.forename: Yuhang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Gallant
authors.forename: Thomas
authors.initials: T
authors.lastname: Andl
authors.forename: Steven H
authors.initials: SH
authors.lastname: Yang
authors.forename: Min-Min
authors.initials: MM
authors.lastname: Lu
authors.forename: Stefano
authors.initials: S
authors.lastname: Piccolo
authors.forename: Ruth
authors.initials: R
authors.lastname: Schmidt-Ullrich
authors.forename: Makoto M
authors.initials: MM
authors.lastname: Taketo
authors.forename: Edward E
authors.initials: EE
authors.lastname: Morrisey
authors.forename: Radhika
authors.initials: R
authors.lastname: Atit
authors.forename: Andrzej A
authors.initials: AA
authors.lastname: Dlugosz
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Millar
mesh_terms: D000818:Animals; D051379:Mice; D009024:Morphogenesis; D009805:Odontogenesis; D015398:Signal Transduction; D014070:Tooth / Q000196:embryology* / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D051153:Wnt Proteins; C102068:Wnt10b protein, mouse; D051176:beta Catenin