title: Transgenically ectopic expression of Bmp4 to the Msx1 mutant dental mesenchyme restores downstream gene expression but represses Shh and Bmp2 in the enamel knot of wild type tooth germ.
abstract: Bmp4 is a downstream gene of Msx1 in early mouse tooth development. In this study, we introduced the Msx1-Bmp4 transgenic allele to the Msx1 mutants in which tooth development is arrested at the bud stage in an effort of rescuing Msx1 mutant tooth phenotype in vivo. Ectopic expression of a Bmp4 transgene driven by the mouse Msx1promoter in the dental mesenchyme restored the expression of Lef-1 and Dlx2 but neither Fgf3 nor syndecan-1 in the Msx1 mutant molar tooth germ. The mutant phenotype of molar but not incisor could be partially rescued to progress to the cap stage. The Msx1-Bmp4 transgene was also able to rescue the alveolar processes and the neonatal lethality of the Msx1 mutants. In contrast, overexpression of Bmp4 in the wild type molar mesenchyme down-regulated Shh and Bmp2 expression in the enamel knot, the putative signaling center for tooth patterning, but did not produce a tooth phenotype. These results indicate that Bmp4 can bypass Msx1 function to partially rescue molar tooth development in vivo, and to support alveolar process formation. Expression of Shh and Bmp2 in the enamel knot may not represent critical signals for tooth patterning.
authors.affiliation: Department of Cell and Molecular Biology and Center for Bioenvironmental Research, Tulane University, New Orleans, LA 70118, USA.
authors.forename: X
authors.initials: X
authors.lastname: Zhao
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: Y
authors.initials: Y
authors.lastname: Song
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: Y
authors.initials: Y
authors.lastname: Hu
authors.forename: S H
authors.initials: SH
authors.lastname: Fromm
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000483:Alleles; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism; D001973:Bromodeoxyuridine / Q000378:metabolism; D002455:Cell Division; D003743:Dental Enamel / Q000196:embryology*; D015536:Down-Regulation; D018507:Gene Expression Regulation, Developmental; D005838:Genotype; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins / Q000235:genetics*; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D051957:MSX1 Transcription Factor; D008648:Mesoderm / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014070:Tooth / Q000196:embryology* / Q000378:metabolism* / Q000502:physiology; D015534:Trans-Activators; D014157:Transcription Factors; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta; D019076:Transgenes
chemical_list: C525719:Bmp2 protein, mouse; C525810:Bmp4 protein, mouse; D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; D011506:Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D001973:Bromodeoxyuridine