title: Wnt/β-catenin signaling in the dental mesenchyme regulates incisor development by regulating Bmp4.
abstract: Loss- and gain-of function approaches modulating canonical Wnt/β-catenin activity have established a role for the Wnt/β-catenin pathway during tooth development. Here we show that Wnt/β-catenin signaling is required in the dental mesenchyme for normal incisor development, as locally restricted genetic inactivation of β-catenin results in a splitting of the incisor placode, giving rise to two incisors. Molecularly this is first associated with down-regulation of Bmp4 and subsequent splitting of the Shh domain at a subsequent stage. The latter phenotype can be mimicked by ectopic application of the BMP antagonist Noggin. Conditional genetic inactivation of Bmp4 in the mesenchyme reveals that mesenchymal BMP4 activity is required for maintenance of Shh expression in the dental ectoderm. Taken together our results indicate that β-catenin together with Lef1 and Tcf1 are required to activate Bmp4 expression in order to maintain Shh expression in the dental ectoderm. This provides a mechanism whereby the number of incisors arising from one placode can be varied through local alterations of a mesenchymal signaling circuit involving β-catenin, Lef1, Tcf1 and Bmp4.
authors.affiliation: Research Institute of Molecular Pathology, Dr. Bohrgasse 7, Vienna, Austria.
authors.forename: Sayumi
authors.initials: S
authors.lastname: Fujimori
authors.forename: Hermann
authors.initials: H
authors.lastname: Novak
authors.forename: Martina
authors.initials: M
authors.lastname: Weissenböck
authors.forename: Maria
authors.initials: M
authors.lastname: Jussila
authors.forename: Alexandre
authors.initials: A
authors.lastname: Gonçalves
authors.forename: Rolf
authors.initials: R
authors.lastname: Zeller
authors.forename: Jenna
authors.initials: J
authors.lastname: Galloway
authors.forename: Irma
authors.initials: I
authors.lastname: Thesleff
authors.forename: Christine
authors.initials: C
authors.lastname: Hartmann
mesh_terms: D000818:Animals; D055415:Bone Morphogenetic Protein 4 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002352:Carrier Proteins / Q000494:pharmacology; D004343:Drug Implants; D004847:Epithelial Cells / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D053823:Hedgehog Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000502:physiology*; D007180:Incisor / Q000196:embryology / Q000254:growth & development*; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000502:physiology*; D008334:Mandible; D008648:Mesoderm / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D010641:Phenotype; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology*; D016042:Transplantation, Heterotopic; D051153:Wnt Proteins / Q000502:physiology*; D051176:beta Catenin / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D000099176:Noggin Protein
chemical_list: D055415:Bone Morphogenetic Protein 4; D002352:Carrier Proteins; D004343:Drug Implants; D053823:Hedgehog Proteins; D051538:Hepatocyte Nuclear Factor 1-alpha; D051821:Lymphoid Enhancer-Binding Factor 1; D051153:Wnt Proteins; D051176:beta Catenin; D000099176:Noggin Protein; C525810:Bmp4 protein, mouse; C495267:CTNNB1 protein, mouse; C496488:Hnf1a protein, mouse; C497574:Lef1 protein, mouse; C465570:Shh protein, mouse