title: Cardiac T-box factor Tbx20 directly interacts with Nkx2-5, GATA4, and GATA5 in regulation of gene expression in the developing heart.
abstract: Tbx20 is a member of the T-box transcription factor family expressed in the forming hearts of vertebrate and invertebrate embryos. We report here analysis of Tbx20 expression during murine cardiac development and assessment of DNA-binding and transcriptional properties of Tbx20 isoforms. Tbx20 was expressed in myocardium and endocardium, including high levels in endocardial cushions. cDNAs generated by alternative splicing encode at least four Tbx20 isoforms, and Tbx20a uniquely carried strong transactivation and transrepression domains in its C terminus. Isoforms with an intact T-box bound specifically to DNA sites resembling the consensus brachyury half site, although with less avidity compared with the related factor, Tbx5. Tbx20 physically interacted with cardiac transcription factors Nkx2-5, GATA4, and GATA5, collaborating to synergistically activate cardiac gene expression. Among cardiac GATA factors, there was preferential synergy with GATA5, implicated in endocardial differentiation. In Xenopus embryos, enforced expression of Tbx20a, but not Tbx20b, led to induction of mesodermal and endodermal lineage markers as well as cell migration, indicating that the long Tbx20a isoform uniquely bears functional domains that can alter gene expression and developmental behaviour in an in vivo context. We propose that Tbx20 plays an integrated role in the ancient myogenic program of the heart, and has been additionally coopted during evolution of vertebrates for endocardial cushion development.
authors.affiliation: Victor Chang Cardiac Research Institute, 384 Victoria Street, Darlinghurst, 2010, Sydney, Australia.
authors.forename: Fiona A
authors.initials: FA
authors.lastname: Stennard
authors.forename: Mauro W
authors.initials: MW
authors.lastname: Costa
authors.forename: David A
authors.initials: DA
authors.lastname: Elliott
authors.forename: Scott
authors.initials: S
authors.lastname: Rankin
authors.forename: Saskia J P
authors.initials: SJ
authors.lastname: Haast
authors.forename: Donna
authors.initials: D
authors.lastname: Lai
authors.forename: Lachlan P A
authors.initials: LP
authors.lastname: McDonald
authors.forename: Karen
authors.initials: K
authors.lastname: Niederreither
authors.forename: Pascal
authors.initials: P
authors.lastname: Dolle
authors.forename: Benoit G
authors.initials: BG
authors.lastname: Bruneau
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Zorn
authors.forename: Richard P
authors.initials: RP
authors.lastname: Harvey
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D050991:GATA4 Transcription Factor; D050992:GATA5 Transcription Factor; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006321:Heart / Q000196:embryology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000378:metabolism; D051379:Mice; D009154:Mutation; D020033:Protein Isoforms; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C494752:GATA-5a protein, Xenopus; C494753:GATA-5b protein, Xenopus; D050991:GATA4 Transcription Factor; C494751:GATA4 protein, Xenopus; D050992:GATA5 Transcription Factor; C494756:Gata5 protein, mouse; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C092720:NKX2-5 protein, Xenopus; C095552:NKX2-5 protein, human; C484469:Nkx2-5 protein, mouse; D020033:Protein Isoforms; D020825:T-Box Domain Proteins; C103172:T-box transcription factor 5; C486013:Tbx20 protein, mouse; D014157:Transcription Factors; D029867:Xenopus Proteins; D004247:DNA