Neural Tissue in Ascidian Embryos Is Induced by FGF9/16/20, Acting via a Combination of Maternal GATA and Ets Transcription Factors

In chordates, formation of neural tissue from ectodermal cells requires an induction. The molecular nature of the inducer remains controversial in vertebrates. Here, using the early neural marker Otx as an entry point, we dissected the neural induction pathway in the simple embryos of Ciona intestinalis. We first isolated the regulatory element driving Otx expression in the prospective neural tissue, showed that this element directly responds to FGF signaling and that FGF9/16/20 acts as an endogenous neural inducer. Binding site analysis and gene loss of function established that FGF9/16/20 induces neural tissue in the ectoderm via a synergy between two maternal response factors. Ets1/2 mediates general FGF responsiveness, while the restricted activity of GATAa targets the neural program to the ectoderm. Thus, our study identifies an endogenous FGF neural inducer and its early downstream gene cascade. It also reveals a role for GATA factors in FGF signaling.

[1]  B. Wasylyk,et al.  The Ets family of transcription factors. , 1993, European journal of biochemistry.

[2]  P. Lemaire,et al.  A conserved role for the MEK signalling pathway in neural tissue specification and posteriorisation in the invertebrate chordate, the ascidian Ciona intestinalis , 2003, Development.

[3]  N. Satoh,et al.  Early embryonic expression of FGF4/6/9 gene and its role in the induction of mesenchyme and notochord in Ciona savignyi embryos. , 2002, Development.

[4]  A. Spagnuolo,et al.  Expression and functional analysis of Cititf1, an ascidian NK-2 class gene, suggest its role in endoderm development. , 1999, Development.

[5]  J. Molkentin,et al.  The Transcription Factor GATA4 Is Activated by Extracellular Signal-Regulated Kinase 1- and 2-Mediated Phosphorylation of Serine 105 in Cardiomyocytes , 2001, Molecular and Cellular Biology.

[6]  E. Nishida,et al.  Essential Role of the Transcription Factor Ets-2 inXenopus Early Development* , 2003, The Journal of Biological Chemistry.

[7]  M. Levine,et al.  Characterization of a notochord-specific enhancer from the Brachyury promoter region of the ascidian, Ciona intestinalis. , 1997, Development.

[8]  R. Patient,et al.  GATA-2 is a maternal transcription factor present in Xenopus oocytes as a nuclear complex which is maintained throughout early development. , 1997, Developmental biology.

[9]  Takeshi Kawashima,et al.  A cDNA resource from the basal chordate Ciona intestinalis , 2002, Genesis.

[10]  Paul Richardson,et al.  The Draft Genome of Ciona intestinalis: Insights into Chordate and Vertebrate Origins , 2002, Science.

[11]  P. Lemaire,et al.  Animal and vegetal pole cells of early Xenopus embryos respond differently to maternal dorsal determinants: implications for the patterning of the organiser. , 1997, Development.

[12]  J. Whittaker.  Segregation during ascidian embryogenesis of egg cytoplasmic information for tissue-specific enzyme development. , 1973, Proceedings of the National Academy of Sciences of the United States of America.

[13]  H. Saiga,et al.  Ascidian otx gene Hroth activates transcription of the brain‐specific gene HrTRP , 2002, Developmental dynamics : an official publication of the American Association of Anatomists.

[14]  H. Saiga,et al.  Vegetal cell fate specification and anterior neuroectoderm formation by Hroth, the ascidian homologue of orthodenticle/otx , 1999, Mechanisms of Development.

[15]  R. Muise-Helmericks,et al.  Signal transduction and the Ets family of transcription factors , 2000, Oncogene.

[16]  Y. Jiang,et al.  The Xenopus GATA-4/5/6 genes are associated with cardiac specification and can regulate cardiac-specific transcription during embryogenesis. , 1996, Developmental biology.

[17]  飯倉 洋治,et al.  ヒト好塩基球のシグナル伝達機構(Extracellular Signal-Regulated Kinase の役割の解明) , 2000 .

[18]  A. Streit,et al.  Initiation of neural induction by FGF signalling before gastrulation , 2000, Nature.

[19]  Jun-yong Noh,et al.  Expression cloning , 2001, SIGGRAPH.

[20]  H. Nishida,et al.  An Ets transcription factor, HrEts, is target of FGF signaling and involved in induction of notochord, mesenchyme, and brain in ascidian embryos. , 2003, Developmental biology.

[21]  T. Edlund,et al.  Neural induction: toward a unifying mechanism , 2001, Nature Neuroscience.

[22]  P. Lemaire,et al.  Expression cloning of Siamois, a xenopus homeobox gene expressed in dorsal-vegetal cells of blastulae and able to induce a complete secondary axis , 1995, Cell.

[23]  L. Zon,et al.  Ventral expression of GATA-1 and GATA-2 in the Xenopus embryo defines induction of hematopoietic mesoderm. , 1994, Developmental biology.

[24]  A. Mccarthy.  Development , 1996, Current Opinion in Neurobiology.

[25]  Short upstream sequences associated with the muscle-specific expression of an actin gene in ascidian embryos. , 1994, Developmental biology.

[26]  H. Nishida,et al.  Notch signaling is involved in nervous system formation in ascidian embryos , 2002, Development, Genes and Evolution.

[27]  D. Shi,et al.  A truncated FGF receptor blocks neural induction by endogenous Xenopus inducers. , 1996, Development.

[28]  D. Melton,et al.  Vertebrate Embryonic Cells Will Become Nerve Cells Unless Told Otherwise , 1997, Cell.

[29]  J. Saint-Jeannet,et al.  Neural induction. , 1986, Archives d'anatomie microscopique et de morphologie experimentale.

[30]  H. Spemann,et al.  über Induktion von Embryonalanlagen durch Implantation artfremder Organisatoren , 1924, Archiv für mikroskopische Anatomie und Entwicklungsmechanik.

[31]  Stephen W. Wilson,et al.  Expression of zebrafish GATA 3 (gta3) during gastrulation and neurulation suggests a role in the specification of cell fate , 1995, Mechanisms of Development.

[32]  H. Nishida,et al.  The BMP/CHORDIN antagonism controls sensory pigment cell specification and differentiation in the ascidian embryo. , 2001, Developmental biology.

[33]  A. Streit,et al.  Neural induction : a bird's eye view , 1999 .

[34]  Ali H. Brivanlou,et al.  Neural induction, the default model and embryonic stem cells , 2002, Nature Reviews Neuroscience.

[35]  M. Levine,et al.  Suppressor of hairless activates brachyury expression in the Ciona embryo. , 1998, Developmental biology.

[36]  H. Nishida,et al.  Cell lineage analysis in ascidian embryos by intracellular injection of a tracer enzyme. III. Up to the tissue restricted stage. , 1987, Developmental biology.

[37]  J. Slack,et al.  XFGF‐9: A new fibroblast growth factor from Xenopus embryos , 1996, Developmental dynamics : an official publication of the American Association of Anatomists.

[38]  K. Shibata,et al.  GATA-1 inhibits the formation of notochord and neural tissue in Xenopus embryo. , 1998, Biochemical and biophysical research communications.

[39]  N. Satoh,et al.  Cell lineage analysis in ascidian embryos by intracellular injection of a tracer enzyme. II. The 16- and 32-cell stages. , 1985, Developmental biology.

[40]  Y. Okamura,et al.  Basic fibroblast growth factor induction of neuronal ion channel expression in ascidian ectodermal blastomeres , 1998, The Journal of physiology.

[41]  N. Satoh,et al.  Action of morpholinos in Ciona embryos , 2001, Genesis.

[42]  A. Spagnuolo,et al.  Ci‐GATAa, a GATA‐class gene from the ascidian Ciona intestinalis: Isolation and developmental expression , 2003, Developmental dynamics : an official publication of the American Association of Anatomists.

[43]  N. Satoh,et al.  Fgf genes in the basal chordate Ciona intestinalis , 2002, Development Genes and Evolution.

[44]  D. Sredni,et al.  Differential regulation of neurogenesis by the two Xenopus GATA-1 genes , 1997, Molecular and cellular biology.

[45]  Y. Sakaki,et al.  Characterization of a novel member of the FGF family, XFGF-20, in Xenopus laevis. , 1999, Biochemical and biophysical research communications.

[46]  B. Neel,et al.  The SH2-containing protein-tyrosine phosphatase SH-PTP2 is required upstream of MAP kinase for early xenopus development , 1995, Cell.

[47]  H. Okamoto,et al.  FGF signaling and the anterior neural induction in Xenopus. , 1999, Developmental biology.

[48]  N. Papalopulu,et al.  FGF-8 stimulates neuronal differentiation through FGFR-4a and interferes with mesoderm induction in Xenopus embryos , 2000, Current Biology.

[49]  H. Nishida.  Patterning the marginal zone of early ascidian embryos: localized maternal mRNA and inductive interactions. , 2002, BioEssays : news and reviews in molecular, cellular and developmental biology.

[50]  R. Krumlauf,et al.  Patterning the ascidian nervous system: structure, expression and transgenic analysis of the CiHox3 gene. , 1999, Development.

[51]  M. Levine,et al.  Lineage-specific regulation of the Ciona snail gene in the embryonic mesoderm and neuroectoderm. , 1998, Developmental biology.

[52]  L. Zon,et al.  Expression of GATA-binding proteins during embryonic development in Xenopus laevis. , 1991, Proceedings of the National Academy of Sciences of the United States of America.

[53]  J. Modolell,et al.  Different contributions of pannier and wingless to the patterning of the dorsal mesothorax of Drosophila. , 1999, Development.

[54]  S. Akira,et al.  Spatio‐temporally regulated expression of receptor tyrosine kinases, mRor1, mRor2, during mouse development: implications in development and function of the nervous system , 1999, Genes to cells : devoted to molecular & cellular mechanisms.

[55]  H. Saiga,et al.  Hroth, an orthodenticle-related homeobox gene of the ascidian, Halocynthia roretzi: its expression and putative roles in the axis formation during embryogenesis , 1996, Mechanisms of Development.

[56]  P. Lemaire,et al.  Early steps in the formation of neural tissue in ascidian embryos. , 2002, Developmental biology.