Tbx20 regulation of cardiac cell proliferation and lineage specialization during embryonic and fetal development in vivo.
TBX20 gain-of-function mutations in humans are associated with congenital heart malformations and myocardial defects. However the effects of increased Tbx20 function during cardiac chamber development and maturation have not been reported previously. CAG-CAT-Tbx20 transgenic mice were generated for Cre-dependent induction of Tbx20 in myocardial lineages in the developing heart. βMHCCre-mediated overexpression of Tbx20 in fetal ventricular cardiomyocytes results in increased thickness of compact myocardium, induction of cardiomyocyte proliferation, and increased expression of Bmp10 and pSmad1/5/8 at embryonic day (E) 14.5. βMHCCre-mediated Tbx20 overexpression also leads to increased expression of cardiac conduction system (CCS) genes Tbx5, Cx40, and Cx43 throughout the ventricular myocardium. In contrast, Nkx2.5Cre mediated overexpression of Tbx20 in the embryonic heart results in reduced cardiomyocyte proliferation, increased expression of a cell cycle inhibitor, p21(CIP1), and decreased expression of Tbx2, Tbx5, and N-myc1 at E9.5, concomitant with decreased phospho-ERK1/2 expression. Together, these analyses demonstrate that Tbx20 differentially regulates cell proliferation and cardiac lineage specification in embryonic versus fetal cardiomyocytes. Induction of pSmad1/5/8 at E14.5 and inhibition of dpERK expression at E9.5 are consistent with selective Tbx20 regulation of these pathways in association with stage-specific effects on cardiomyocyte proliferation. Together, these in vivo data support distinct functions for Tbx20 in regulation of cardiomyocyte lineage maturation and cell proliferation at embryonic and fetal stages of heart development.
The Heart Institute, Cincinnati Children's Medical Center, Cincinnati, OH 45229, USA.
Santanu
S
Chakraborty
Katherine E
KE
Yutzey
D000818:Animals; D015153:Blotting, Western; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism; D019070:Cell Lineage / Q000235:genetics; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian / Q000196:embryology / Q000378:metabolism*; D004789:Enzyme Activation; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000196:embryology / Q000254:growth & development; D017403:In Situ Hybridization; D051379:Mice; D008822:Mice, Transgenic; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051785:Smad Proteins / Q000378:metabolism; D020825:T-Box Domain Proteins / Q000235:genetics* / Q000378:metabolism; D013997:Time Factors
C119152:Bmp10 protein, mouse; D019485:Bone Morphogenetic Proteins; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016271:Proto-Oncogene Proteins c-myc; D051785:Smad Proteins; D020825:T-Box Domain Proteins; C103172:T-box transcription factor 5; C486013:Tbx20 protein, mouse; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3