title: Beta-catenin/Tcf-regulated transcription prior to the midblastula transition.
abstract: Following fertilization, the zygotic genome in many organisms is quiescent until the midblastula transition (MBT), when large-scale transcription begins. In Xenopus embryos, for example, transcription is believed to be repressed until the twelfth cell division. Thus, although dorsal-ventral patterning begins during the first cell cycle, little attention has been given to transcriptional regulation in pre-MBT development. We present evidence that regulated transcription begins during early cleavage stages and that the beta-catenin-Tcf complex is required for the transcription of the Xenopus nodal genes Xnr5 and Xnr6 as early as the 256-cell stage. Moreover, inhibition of beta-catenin/Tcf function can block dorsal development, but only if the inhibition begins early and is maintained throughout pre-MBT stages. Dorsal development can be rescued in ventralized embryos if Tcf-dependent transcription is activated prior to MBT, but activation of Tcf after MBT cannot rescue ventralized embryos, suggesting that beta-catenin/Tcf-dependent transcription is required prior to MBT for dorsal-ventral patterning in Xenopus.
authors.affiliation: Department of Medicine (Hematology-Oncology) and Howard Hughes Medical Institute, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Change
authors.initials: C
authors.lastname: Tan
authors.forename: Rachel S
authors.initials: RS
authors.lastname: Darken
authors.forename: Paul A
authors.initials: PA
authors.lastname: Wilson
authors.forename: Peter S
authors.initials: PS
authors.lastname: Klein
mesh_terms: D000818:Animals; D036703:Blastula / Q000378:metabolism; D002455:Cell Division; D003598:Cytoskeletal Proteins / Q000378:metabolism / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D005799:Genes, Dominant; D024002:HMGB Proteins / Q000378:metabolism / Q000502:physiology*; D008094:Lithium / Q000494:pharmacology; D008156:Luciferases / Q000378:metabolism; D055456:Nodal Signaling Ligands; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D014176:Protein Biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051820:TCF Transcription Factors; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology*; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014981:Xenopus / Q000196:embryology*; D029867:Xenopus Proteins; D051176:beta Catenin
chemical_list: C495266:CTNNB1 protein, Xenopus; D003598:Cytoskeletal Proteins; D024002:HMGB Proteins; D055456:Nodal Signaling Ligands; D051820:TCF Transcription Factors; D015534:Trans-Activators; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors; D029867:Xenopus Proteins; D051176:beta Catenin; C418882:nodal5 protein, Xenopus; C418883:nodal6 protein, Xenopus; D008094:Lithium; D008156:Luciferases