title: Dact1-3 mRNAs exhibit distinct expression domains during tooth development.
abstract: Wnt signaling is essential for tooth formation and Dact proteins modulate Wnt signaling by binding to the intracellular protein Dishevelled (Dvl). Comparison of the three known mouse Dact genes, Dact1-3, from the morphological initiation of mandibular first molar development through the onset of root formation using section in situ hybridization showed distinct, complementary and overlapping expression patterns for these genes. Whereas Dact2 expression was restricted to the dental epithelium, including the enamel knot signaling centers and pre-ameloblasts, Dact1 and Dact3 showed developmentally regulated expression in the dental mesenchyme. Both Dact1 and Dact3 mRNAs were first detected in the presumptive dental mesenchyme. After being downregulated from the condensing dental mesenchyme of the bud stage tooth germ, Dact1 was upregulated in the dental follicle mesenchyme at the cap stage and subsequently also in the dental papilla at the bell stage, where the expression persisted to the postnatal stages. In contrast, Dact3 transcripts persisted throughout the dental mesenchyme, including the preodontoblasts, during embryogenesis before transcripts were largely downregulated from the tooth germ postnatally. Collectively, these results suggest that Dact1 and -3 may contribute to early tooth formation by modulation of Wnt signaling pathways in the mesenchyme, including preodontoblasts, whereas Dact2 may play important signal-modulating roles in the adjacent epithelial cells including the enamel knot signaling centers and pre-ameloblasts. Future loss-of-function studies will help elucidate whether any of these functions are redundant, particularly for Dact1 and Dact3.
authors.affiliation: Section of Anatomy and Cell Biology, Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009 Bergen, Norway. Paivi.Kettunen@biomed.uib.no
authors.forename: Päivi
authors.initials: P
authors.lastname: Kettunen
authors.forename: Saul
authors.initials: S
authors.lastname: Kivimäe
authors.forename: Pankaj
authors.initials: P
authors.lastname: Keshari
authors.forename: Ophir D
authors.initials: OD
authors.lastname: Klein
authors.forename: Benjamin N R
authors.initials: BN
authors.lastname: Cheyette
authors.forename: Keijo
authors.initials: K
authors.lastname: Luukko
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D004848:Epithelium / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D008648:Mesoderm / Q000378:metabolism*; D051379:Mice; D008963:Molar / Q000378:metabolism; D009805:Odontogenesis / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins; D014083:Tooth Germ / Q000378:metabolism; D051153:Wnt Proteins / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C514734:Dact2 protein, mouse; C514671:Dact3 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D051153:Wnt Proteins; C508545:frodo protein, mouse