title: The NK homeodomain transcription factor Tinman is a direct activator of seven-up in the Drosophila dorsal vessel.
abstract: A complex regulatory cascade is required for normal cardiac development, and many aspects of this network are conserved from Drosophila to mammals. In Drosophila, the seven-up (svp) gene, an ortholog of the vertebrate chick ovalbumin upstream promoter transcription factors (COUP-TFI and II), is initially activated in the cardiac mesoderm and is subsequently restricted to cells forming the cardiac inflow tracts. Here, we investigate svp regulation in the developing cardiac tube. Using bioinformatics, we identify a 1007-bp enhancer of svp which recapitulates its entire expression in the embryonic heart and other mesodermal derivatives, and we show that this enhancer is initially activated by the NK homeodomain factor Tinman (Tin) via two conserved Tin binding sites. Mutation of the Tin binding sites significantly reduces enhancer activity both during normal development and in response to ectopic Tin. This is the first identification of an enhancer for the complex svp gene, demonstrating the effectiveness of bioinformatics tools in assisting in unraveling transcriptional regulatory networks. Our studies define a critical component of the svp regulatory cascade and place gene regulatory events in direct apposition to the formation of critical cardiac structures.
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Ryan
authors.forename: Jill D
authors.initials: JD
authors.lastname: Hendren
authors.forename: Lynda A
authors.initials: LA
authors.lastname: Helander
authors.forename: Richard M
authors.initials: RM
authors.lastname: Cripps
mesh_terms: D000818:Animals; D001483:Base Sequence; D002319:Cardiovascular System / Q000196:embryology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D004330:Drosophila / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D008648:Mesoderm / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011987:Receptors, Steroid / Q000235:genetics / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D011987:Receptors, Steroid; D012097:Repressor Proteins; D015534:Trans-Activators; C094295:svp protein, Drosophila; C102933:tin protein, Drosophila