TY - JOUR
T1 - β-catenin-driven binary fate specification segregates germ layers in ascidian embryos
AU - Hudson, Clare
AU - Kawai, Narudo
AU - Negishi, Takefumi
AU - Yasuo, Hitoyoshi
N1 - Funding Information:
This research was supported by the Centre National de la Recherche Scientifique (CNRS), the Université Pierre et Marie Curie, the Fondation ARC pour la Recherche sur le Cancer (1144), and the Agence Nationale de la Recherche (ANR-05-BLAN-0342-01 and ANR-09-BLAN-0013-01). We thank U. Röthbacher and P. Lemaire (12xTCF::lacZ and Unigene Collection Plates), M. Gilchrist (Unigene Collection Plates), H. Nishida (β-catenin antibody and H2B-mCherry), N. Satoh (Gene Collection Plates), and R. Dumollard (β-catenin (R459A:H460A)-venus). Thanks also to V. Bertrand, E. Houliston, and C. Sirour and the anonymous reviewers for helpful criticisms of the manuscript.
PY - 2013/3/18
Y1 - 2013/3/18
N2 - β-catenin is a transcriptional cofactor mediating the "canonical" Wnt signaling pathway, which activates target genes in a complex with TCF (LEF) transcription factors [1]. In many metazoans, embryos are first subdivided during early cleavage stages into nuclear β-catenin- positive and -negative domains, with β-catenin specifying endoderm or mesendoderm fate. This process has been demonstrated in a wide range of phyla including cnidarians, nemerteans, and invertebrate deuterostomes (echinoderms, hemichordates, and ascidians), implying that β-catenin-dependent (mes)endoderm specification is evolutionarily ancient [2-10]. However, the mechanisms leading to the segregation of mesoderm and endoderm fates from a transient mesendodermal state are less well defined. We show that subdivision of the ascidian embryo into the three germ layers involves differential nuclear β-catenin activity coupled with the first two animal-vegetal (A-V)-oriented cell divisions. We reveal that each of these A-V divisions operates as a binary fate choice: the first between ectoderm and mesendoderm and the second between margin (notochord and neural) and endoderm, such that a β-catenin activation sequence of ON-to-ON specifies endoderm, OFF-to-OFF ectoderm, and ON-to-OFF margin.
AB - β-catenin is a transcriptional cofactor mediating the "canonical" Wnt signaling pathway, which activates target genes in a complex with TCF (LEF) transcription factors [1]. In many metazoans, embryos are first subdivided during early cleavage stages into nuclear β-catenin- positive and -negative domains, with β-catenin specifying endoderm or mesendoderm fate. This process has been demonstrated in a wide range of phyla including cnidarians, nemerteans, and invertebrate deuterostomes (echinoderms, hemichordates, and ascidians), implying that β-catenin-dependent (mes)endoderm specification is evolutionarily ancient [2-10]. However, the mechanisms leading to the segregation of mesoderm and endoderm fates from a transient mesendodermal state are less well defined. We show that subdivision of the ascidian embryo into the three germ layers involves differential nuclear β-catenin activity coupled with the first two animal-vegetal (A-V)-oriented cell divisions. We reveal that each of these A-V divisions operates as a binary fate choice: the first between ectoderm and mesendoderm and the second between margin (notochord and neural) and endoderm, such that a β-catenin activation sequence of ON-to-ON specifies endoderm, OFF-to-OFF ectoderm, and ON-to-OFF margin.
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U2 - 10.1016/j.cub.2013.02.005
DO - 10.1016/j.cub.2013.02.005
M3 - Article
C2 - 23453950
AN - SCOPUS:84875244412
VL - 23
SP - 491
EP - 495
JO - Current Biology
JF - Current Biology
SN - 0960-9822
IS - 6
ER -