title: Nkx2-5 activity is essential for cardiomyogenesis.
abstract: The homeobox transcription factor tinman is essential for heart vessel formation in Drosophila. In contrast, mice lacking the murine homologue Nkx2-5 are defective in cardiac looping but not in cardiac myocyte development. The lack of an essential role for Nkx2-5 in cardiomyogenesis in mammalian systems is most likely the result of genetic redundancy with family members. In this study, we used a dominant negative mutant of Nkx2-5, created by fusing the repressor domain of engrailed 2 to the Nkx2-5 homeodomain, termed Nkx/EnR. Expression of Nkx/EnR inhibited Me(2)SO-induced cardiomyogenesis in P19 cells but not skeletal myogenesis. Nkx/EnR inhibited expression of cardiomyoblast markers, such as GATA-4 and MEF2C, but not of mesoderm markers, such as Brachyury T and Wnt5b, or of skeletal lineage markers, such as MyoD and Mox1. To identify the minimal region of Nkx2-5 that can trigger cardiomyogenesis, we analyzed the activity of various Nkx2-5 deletion mutants. The C-terminal domain was not necessary for the ability of Nkx2-5 to induce cardiomyogenesis and loss of this domain did not enhance myogenesis. Therefore, Nkx2-5 function is essential for commitment of mesoderm into the cardiac muscle lineage, and the N-terminal region, together with the homeodomain, is sufficient for cardiomyogenesis in P19 cells.
authors.affiliation: Department of Biochemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Jamali
authors.forename: P J
authors.initials: PJ
authors.lastname: Rogerson
authors.forename: S
authors.initials: S
authors.lastname: Wilton
authors.forename: I S
authors.initials: IS
authors.lastname: Skerjanc
mesh_terms: D000199:Actins / Q000235:genetics; D000818:Animals; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000032:analysis; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics; D050991:GATA4 Transcription Factor; D006321:Heart / Q000196:embryology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000737:chemistry / Q000502:physiology*; D064326:MEF2 Transcription Factors; D018482:Muscle, Skeletal / Q000196:embryology; D018006:Myogenic Regulatory Factors / Q000235:genetics; D014411:Neoplastic Stem Cells; D012333:RNA, Messenger / Q000032:analysis; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics; D029867:Xenopus Proteins
chemical_list: D000199:Actins; C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; C095552:NKX2-5 protein, human; D012333:RNA, Messenger; D014157:Transcription Factors; D029867:Xenopus Proteins; C525812:bmp4 protein, Xenopus