title: Fibroblast growth factor 10 gene regulation in the second heart field by Tbx1, Nkx2-5, and Islet1 reveals a genetic switch for down-regulation in the myocardium.
abstract: During cardiogenesis, Fibroblast Growth Factor (Fgf10) is expressed in the anterior second heart field. Together with Fibroblast growth factor 8 (Fgf8), Fgf10 promotes the proliferation of these cardiac progenitor cells that form the arterial pole of the heart. We have identified a 1.7-kb region in the first intron of Fgf10 that is necessary and sufficient to direct transgene expression in this cardiac context. The 1.7-kb sequence is directly controlled by T-box transcription factor 1 (Tbx1) in anterior second heart field cells that contribute to the outflow tract. It also responds to both NK2 transcription factor related, locus 5 (Nkx2-5) and ISL1 transcription factor, LIM/homeodomain (Islet1), acting through overlapping sites. Mutation of these sites reduces transgene expression in the anterior second heart field where the Fgf10 regulatory element is activated by Islet1 via direct binding in vivo. Analysis of the response to Nkx2-5 loss- and Isl1 gain-of-function genetic backgrounds indicates that the observed up-regulation of its activity in Nkx2-5 mutant hearts, reflecting that of Fgf10, is due to the absence of Nkx2-5 repression and to up-regulation of Isl1, normally repressed in the myocardium by Nkx2-5. ChIP experiments show strong binding of Nkx2-5 in differentiated myocardium. Molecular and genetic analysis of the Fgf10 cardiac element therefore reveals how key cardiac transcription factors orchestrate gene expression in the anterior second heart field and how genes, such as Fgf10, normally expressed in the progenitor cell population, are repressed when these cells enter the heart and differentiate into myocardium. Our findings provide a paradigm for transcriptional mechanisms that underlie the changes in regulatory networks during the transition from progenitor state to that of the differentiated tissue.
authors.affiliation: Department of Developmental Biology, Centre National de la Recherche Scientifique (CNRS) Unité de Recherche Associée 2578, Institut Pasteur, 75015 Paris, France.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Stéphane
authors.initials: S
authors.lastname: Zaffran
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kuroiwa
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Higuchi
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ogura
authors.forename: Richard P
authors.initials: RP
authors.lastname: Harvey
authors.forename: Robert G
authors.initials: RG
authors.lastname: Kelly
authors.forename: Margaret
authors.initials: M
authors.lastname: Buckingham
mesh_terms: D000818:Animals; D020029:Base Pairing / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics; D051526:Fibroblast Growth Factor 10 / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005812:Genes, Switch / Q000235:genetics*; D006321:Heart / Q000196:embryology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D060850:LIM-Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D019076:Transgenes / Q000235:genetics
chemical_list: C496464:Fgf10 protein, mouse; D051526:Fibroblast Growth Factor 10; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; C484469:Nkx2-5 protein, mouse; D020825:T-Box Domain Proteins; C491573:Tbx1 protein, mouse; D014157:Transcription Factors; C063843:insulin gene enhancer binding protein Isl-1