title: A combinatorial code of maternal GATA, Ets and beta-catenin-TCF transcription factors specifies and patterns the early ascidian ectoderm.
abstract: Our understanding of the maternal factors that initiate early chordate development, and of their direct zygotic targets, is still fragmentary. A molecular cascade is emerging for the mesendoderm, but less is known about the ectoderm, giving rise to epidermis and nervous tissue. Our cis-regulatory analysis surprisingly places the maternal transcription factor Ci-GATAa (GATA4/5/6) at the top of the ectodermal regulatory network in ascidians. Initially distributed throughout the embryo, Ci-GATAa activity is progressively repressed in vegetal territories by accumulating maternal beta-catenin. Once restricted to the animal hemisphere, Ci-GATAa directly activates two types of zygotic ectodermal genes. First, Ci-fog is activated from the 8-cell stage throughout the ectoderm, then Ci-otx is turned on from the 32-cell stage in neural precursors only. Whereas the enhancers of both genes contain critical and interchangeable GATA sites, their distinct patterns of activation stem from the additional presence of two Ets sites in the Ci-otx enhancer. Initially characterized as activating elements in the neural lineages, these Ets sites additionally act as repressors in non-neural lineages, and restrict GATA-mediated activation of Ci-otx. We thus identify a precise combinatorial code of maternal factors responsible for zygotic onset of a chordate ectodermal genetic program.
authors.affiliation: Institut de Biologie du Développement de Marseille Luminy (IBDML), CNRS-UMR6216/Université de la Méditerranée Aix-Marseille, F-13288 Marseille Cedex 9, France. rothbach@ibdml.univ-mrs.fr
authors.forename: Ute
authors.initials: U
authors.lastname: Rothbächer
authors.forename: Vincent
authors.initials: V
authors.lastname: Bertrand
authors.forename: Clement
authors.initials: C
authors.lastname: Lamy
authors.forename: Patrick
authors.initials: P
authors.lastname: Lemaire
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D002938:Ciona intestinalis / Q000196:embryology* / Q000235:genetics; D004475:Ectoderm / Q000196:embryology* / Q000378:metabolism; D004625:Embryo, Nonmammalian; D050980:GATA Transcription Factors / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D008954:Models, Biological; D009035:Mothers; D050783:Proto-Oncogene Proteins c-ets / Q000235:genetics / Q000502:physiology*; D023121:RNA, Messenger, Stored / Q000502:physiology; D051820:TCF Transcription Factors / Q000235:genetics / Q000502:physiology*; D014561:Urochordata / Q000196:embryology / Q000235:genetics; D051176:beta Catenin / Q000235:genetics / Q000502:physiology*
chemical_list: D050980:GATA Transcription Factors; D050783:Proto-Oncogene Proteins c-ets; D023121:RNA, Messenger, Stored; D051820:TCF Transcription Factors; D051176:beta Catenin