title: Neural ectoderm-secreted FGF initiates the expression of Nkx2.5 in cardiac progenitors via a p38 MAPK/CREB pathway.
abstract: Vertebrate heart development is derived from paired primordia of anterior dorsolateral mesoderm expressing Nkx2.5 and GATA4 transcription factors. Yet growth factors and intracellular pathways specifying heart precursor gene expression are poorly understood. In the present work, we investigated the signaling events initiating Nkx2.5 expression in Xenopus laevis. We describe here that fibroblast growth factor (FGF) initiates the expression of Nkx2.5 without affecting GATA4. At gastrula, FGF3 is expressed in anterior neural ectoderm, and results presented here indicate that this tissue is involved in the induction of Nkx2.5 expression in neighboring lateral tissues. Further studies indicate that the intracellular p38 MAPK and the CREB transcription factor function downstream of FGF to initiate Nkx2.5 expression. Activation of the p38 MAPK pathway and of the CREB protein is both necessary and sufficient for the initial expression of Nkx2.5. Therefore, we would like to suggest that FGF expressed in anterior neural ectoderm is a major inducer of Nkx2.5 expression in neighboring cells. In these cells, FGF activates an intracellular p38 MAPK signaling pathway and its downstream target, the CREB transcription factor, all participating in the expression of Nkx2.5 in cardiac progenitors.
authors.affiliation: Department of Biochemistry, Rappaport Institute for Research in the Medical Sciences, Haifa, Israel.
authors.forename: Anat
authors.initials: A
authors.lastname: Keren-Politansky
authors.forename: Aviad
authors.initials: A
authors.lastname: Keren
authors.forename: Eyal
authors.initials: E
authors.lastname: Bengal
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017931:DNA Primers; D004475:Ectoderm / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000378:metabolism / Q000502:physiology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008845:Microinjections; D009206:Myocardium / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D009420:Nervous System / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013234:Stem Cells / Q000201:enzymology / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D017931:DNA Primers; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C092720:NKX2-5 protein, Xenopus; D014157:Transcription Factors; D029867:Xenopus Proteins; D005346:Fibroblast Growth Factors; D048051:p38 Mitogen-Activated Protein Kinases