title: Nkx-2.5 gene induction in mice is mediated by a Smad consensus regulatory region.
abstract: In the forming vertebrate heart, bone morphogenetic protein signaling induces expression of the early cardiac regulatory gene nkx-2.5. A similar regulatory interaction has been defined in Drosophila embryos where Dpp signaling mediated by the Smad homologues Mad and Medea directly regulates early cardiac expression of tinman. A conserved cluster of Smad consensus binding sequences was identified in early cardiac regulatory sequences of the mouse nkx-2.5 gene. The importance of the nkx-2.5 Smad consensus region in early cardiac gene expression was examined in transgenic mice and in cultured mouse embryos. In transgenic mice, deletion of the Smad consensus region delays induction of embryonic DeltaSmadnkx-2.5/lacZ gene expression during early heart formation. Induction of DeltaSmadnkx-2.5/lacZ expression is also delayed in the outflow tract myocardium and visceral mesoderm. Targeted mutation of the three Smad consensus sequences inhibited nkx-2.5/lacZ expression in the cardiac crescent, demonstrating a specific requirement for the Smad consensus sites in early cardiac gene induction. Cultured DeltaSmadnkx-2.5/lacZ transgenic mouse embryos also exhibit delayed induction of transgene expression. In the four-chambered heart, deletion of the Smad consensus region resulted in expanded DeltaSmadnkx-2.5/lacZ transgene expression. Thus, the nkx-2.5 Smad consensus region can have positive or negative regulatory function, depending on the developmental context and cellular environment.
authors.affiliation: Division of Molecular Cardiovascular Biology, The Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, Ohio 45229, USA.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Liberatore
authors.forename: Robin D
authors.initials: RD
authors.lastname: Searcy-Schrick
authors.forename: Eric B
authors.initials: EB
authors.lastname: Vincent
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Yutzey
mesh_terms: D000818:Animals; D001483:Base Sequence; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000502:physiology; D016384:Consensus Sequence; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D005775:Gastrula / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics*; D017403:In Situ Hybridization; D051379:Mice; D008822:Mice, Transgenic; D009924:Organ Culture Techniques; D012045:Regulatory Sequences, Nucleic Acid; D017384:Sequence Deletion; D051785:Smad Proteins; D015534:Trans-Activators / Q000235:genetics*; D014157:Transcription Factors; D015533:Transcriptional Activation; D016212:Transforming Growth Factor beta; D029867:Xenopus Proteins
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; C484469:Nkx2-5 protein, mouse; D051785:Smad Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D029867:Xenopus Proteins