title: Tbx20 regulation of endocardial cushion cell proliferation and extracellular matrix gene expression.
abstract: While recent work has implicated Tbx20 in myocardial maturation and proliferation, the role of Tbx20 in heart valve development remains relatively unknown. Tbx20 expression was manipulated in primary avian endocardial cells in order to elucidate its function in developing endocardial cushions. Tbx20 gain of function was achieved with a Tbx20-adenovirus, and endogenous Tbx20 expression was inhibited with Tbx20-specific siRNA in cultured endocardial cushion cells. With Tbx20 gain of function, the expression of chondroitin sulfate proteoglycans (CSPG), including aggrecan and versican, was decreased, while the expression of the matrix metalloproteinases (MMP) mmp9 and mmp13 was increased. Consistent results were observed with Tbx20 loss of function, where the expression of CSPG genes increased and MMP genes decreased. In addition, cushion mesenchyme proliferation increased with infection of a Tbx20-adenovirus and decreased with transfection of Tbx20-specfic siRNA. Furthermore, BMP2 treatment resulted in increased Tbx20 expression in endocardial cushion cells, and loss of Tbx20 led to increased Tbx2 and decreased N-myc gene expression. Taken together, these data support a role for Tbx20 in repressing extracellular matrix remodeling and promoting cell proliferation in mesenchymal valve precursor populations in endocardial cushions during embryonic development.
authors.affiliation: Division of Molecular Cardiovascular Biology, Cincinnati Children's Medical Center ML 7020, 3333 Burnet Avenue, Cincinnati, OH 45229, USA.
authors.forename: Elaine L
authors.initials: EL
authors.lastname: Shelton
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Yutzey
mesh_terms: D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002352:Carrier Proteins / Q000494:pharmacology; D049109:Cell Proliferation; D002478:Cells, Cultured; D002642:Chick Embryo; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis*; D018507:Gene Expression Regulation, Developmental; D016259:Genes, myc; D006346:Heart Septum / Q000196:embryology* / Q000378:metabolism; D006351:Heart Valves / Q000196:embryology* / Q000378:metabolism; D006801:Humans; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D020825:T-Box Domain Proteins / Q000378:metabolism / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D053675:Versicans / Q000378:metabolism; D000099176:Noggin Protein
chemical_list: D053674:Aggrecans; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D016326:Extracellular Matrix Proteins; D053509:Matrix Metalloproteinase 13; D020780:Matrix Metalloproteinase 9; D011994:Recombinant Proteins; D020825:T-Box Domain Proteins; D016212:Transforming Growth Factor beta; D053675:Versicans; D000099176:Noggin Protein; C525718:BMP2 protein, human; C097348:T-Box Domain Protein 2