title: Wnt signaling in Xenopus embryos inhibits bmp4 expression and activates neural development.
abstract: We report a new role for Wnt signaling in the vertebrate embryo: the induction of neural tissue from ectoderm. Early expression of mouse wnt8, Xwnt8, beta-catenin, or dominant-negative GSK3 induces the expression of neural-specific markers and inhibits the expression of Bmp4 in Xenopus ectoderm. We show that Wnt8, but not the BMP antagonist Noggin, can inhibit Bmp4 expression at early gastrula stages. Furthermore, inhibition of beta-catenin activity in the neural ectoderm of whole embryos by a truncated TCF results in a decrease in neural development. Therefore, we suggest that a cleavage-stage Wnt signal normally contributes to an early repression of Bmp4 on the dorsal side of the embryo and sensitizes the ectoderm to respond to neural inducing signals from the organizer. The Wnt targets Xnr3 and siamois have been shown previously to have neuralizing activity when overexpressed. However, antagonists of Wnt signaling, dnXwnt8 and Nxfrz8, inhibit Wnt-mediated Xnr3 and siamois induction, but not neural induction, suggesting an alternative mechanism for Bmp repression and neuralization. Conversely, dnTCF blocks both Wnt-mediated Xnr3 and neural induction, suggesting that both pathways require this transcription factor.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Baker
authors.forename: R S
authors.initials: RS
authors.lastname: Beddington
authors.forename: R M
authors.initials: RM
authors.lastname: Harland
mesh_terms: D000818:Animals; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000096:biosynthesis* / Q000235:genetics; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins / Q000502:physiology; D004475:Ectoderm / Q000502:physiology; D004625:Embryo, Nonmammalian; D004627:Embryonic Induction / Q000502:physiology*; D005314:Embryonic and Fetal Development / Q000235:genetics; D005326:Fetal Proteins / Q000235:genetics / Q000502:physiology; D005775:Gastrula / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology; D017403:In Situ Hybridization; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology; D009420:Nervous System / Q000196:embryology*; D011506:Proteins / Q000235:genetics / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology; D012261:Ribonucleoproteins / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology; D029961:Zebrafish Proteins; D051176:beta Catenin; D000099176:Noggin Protein
chemical_list: D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D005326:Fetal Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D018125:Receptors, Transforming Growth Factor beta; D012261:Ribonucleoproteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D051176:beta Catenin; D000099176:Noggin Protein; C525810:Bmp4 protein, mouse; C495266:CTNNB1 protein, Xenopus; C495267:CTNNB1 protein, mouse; C093133:SIA1 protein, Xenopus; C525812:bmp4 protein, Xenopus; C525813:bmp4 protein, zebrafish; C094620:nodal3.1 protein, Xenopus; C495248:wnt8a protein, Xenopus; C068598:Msi1 protein, Xenopus