title: Co-expression of Foxa.a, Foxd and Fgf9/16/20 defines a transient mesendoderm regulatory state in ascidian embryos.
abstract: In many bilaterian embryos, nuclear β-catenin (nβ-catenin) promotes mesendoderm over ectoderm lineages. Although this is likely to represent an evolutionary ancient developmental process, the regulatory architecture of nβ-catenin-induced mesendoderm remains elusive in the majority of animals. Here, we show that, in ascidian embryos, three nβ-catenin transcriptional targets, Foxa.a, Foxd and Fgf9/16/20, are each required for the correct initiation of both the mesoderm and endoderm gene regulatory networks. Conversely, these three factors are sufficient, in combination, to produce a mesendoderm ground state that can be further programmed into mesoderm or endoderm lineages. Importantly, we show that the combinatorial activity of these three factors is sufficient to reprogramme developing ectoderm cells to mesendoderm. We conclude that in ascidian embryos, the transient mesendoderm regulatory state is defined by co-expression of Foxa.a, Foxd and Fgf9/16/20.
authors.affiliation: Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Villefranche-sur-Mer, France.
authors.forename: Clare
authors.identifier: 0000-0003-1585-8328
authors.initials: C
authors.lastname: Hudson
authors.affiliation: Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Villefranche-sur-Mer, France.
authors.forename: Cathy
authors.identifier: 0000-0002-0114-8985
authors.initials: C
authors.lastname: Sirour
authors.affiliation: Laboratoire de Biologie du Développement de Villefranche-sur-mer, Observatoire Océanologique, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Villefranche-sur-Mer, France.
authors.forename: Hitoyoshi
authors.identifier: 0000-0002-0817-3796
authors.initials: H
authors.lastname: Yasuo
mesh_terms: D000818:Animals; D004707:Endoderm / Q000196:embryology; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D008648:Mesoderm / Q000196:embryology; D014561:Urochordata / Q000196:embryology*
keywords: C. intestinalis; ascidian; beta-catenin; binary fate switch; developmental biology; germ layer; mesendoderm; stem cells