201
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Kirk EP, Sunde M, Costa MW, Rankin SA, Wolstein O, Castro ML, Butler TL, Hyun C, Guo G, Otway R, Mackay JP, Waddell LB, Cole AD, Hayward C, Keogh A, Macdonald P, Griffiths L, Fatkin D, Sholler GF, Zorn AM, Feneley MP, Winlaw DS, Harvey RP. Mutations in cardiac T-box factor gene TBX20 are associated with diverse cardiac pathologies, including defects of septation and valvulogenesis and cardiomyopathy. Am J Hum Genet 2007; 81:280-91. [PMID: 17668378 PMCID: PMC1950799 DOI: 10.1086/519530] [Citation(s) in RCA: 255] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Accepted: 05/01/2007] [Indexed: 12/12/2022] Open
Abstract
The T-box family transcription factor gene TBX20 acts in a conserved regulatory network, guiding heart formation and patterning in diverse species. Mouse Tbx20 is expressed in cardiac progenitor cells, differentiating cardiomyocytes, and developing valvular tissue, and its deletion or RNA interference-mediated knockdown is catastrophic for heart development. TBX20 interacts physically, functionally, and genetically with other cardiac transcription factors, including NKX2-5, GATA4, and TBX5, mutations of which cause congenital heart disease (CHD). Here, we report nonsense (Q195X) and missense (I152M) germline mutations within the T-box DNA-binding domain of human TBX20 that were associated with a family history of CHD and a complex spectrum of developmental anomalies, including defects in septation, chamber growth, and valvulogenesis. Biophysical characterization of wild-type and mutant proteins indicated how the missense mutation disrupts the structure and function of the TBX20 T-box. Dilated cardiomyopathy was a feature of the TBX20 mutant phenotype in humans and mice, suggesting that mutations in developmental transcription factors can provide a sensitized template for adult-onset heart disease. Our findings are the first to link TBX20 mutations to human pathology. They provide insights into how mutation of different genes in an interactive regulatory circuit lead to diverse clinical phenotypes, with implications for diagnosis, genetic screening, and patient follow-up.
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Affiliation(s)
- Edwin P Kirk
- Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales, 2010, Australia
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202
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Farin HF, Bussen M, Schmidt MK, Singh MK, Schuster-Gossler K, Kispert A. Transcriptional Repression by the T-box Proteins Tbx18 and Tbx15 Depends on Groucho Corepressors. J Biol Chem 2007; 282:25748-59. [PMID: 17584735 DOI: 10.1074/jbc.m703724200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Tbox18 (Tbx18) and Tbox15 (Tbx15) encode a closely related pair of vertebrate-specific T-box (Tbx) transcription factors. Functional analyses in the mouse have proven the requirement of Tbx15 in skin and skeletal development and of Tbx18 in the formation of the vertebral column, the ureter, and the posterior pole of the heart. Despite the accumulation of genetic data concerning the embryological roles of these genes, it is currently unclear how Tbx18 and Tbx15 exert their function on the molecular level. Here, we have initiated a molecular analysis of Tbx18 and Tbx15 proteins and have characterized functional domains for nuclear localization, DNA binding, and transcriptional modulation. We show that both proteins homo- and heterodimerize, bind to various combinations of T half-sites, and repress transcription in a Groucho-dependent manner. Competition with activating T-box proteins may constitute one mode of action as we show that Tbx18 interacts with Gata4 and Nkx2-5 and competes Tbx5-mediated activation of the cardiac Natriuretic peptide precursor type a-promoter and that ectopic expression of Tbx18 down-regulates Tbx6-activated Delta-like 1 expression in the somitic mesoderm in vivo.
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Affiliation(s)
- Henner F Farin
- Institute for Molecular Biology, Medizinische Hochschule Hannover, 30625 Hannover, Germany
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203
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Snarr BS, Wirrig EE, Phelps AL, Trusk TC, Wessels A. A spatiotemporal evaluation of the contribution of the dorsal mesenchymal protrusion to cardiac development. Dev Dyn 2007; 236:1287-94. [PMID: 17265457 PMCID: PMC4003411 DOI: 10.1002/dvdy.21074] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The mesenchymal tissues involved in cardiac septation are derived from different sources. In addition to endocardial-derived mesenchyme, the heart also receives contributions from the neural crest, the proepicardium, and the dorsal mesenchymal protrusion (DMP). Whereas the contributions of the neural crest and proepicardium have been thoroughly studied, the DMP has received little attention. Here, we present the results of a comprehensive spatiotemporal study of the DMP in cardiac development. Using the Tie2-Cre mouse, immunohistochemistry, and AMIRA reconstructions, we show that the DMP, in combination with the mesenchymal cap on the primary atrial septum, fuse with the major atrioventricular cushions to close the primary atrial foramen and to form the atrioventricular mesenchymal complex. In this complex, the DMP constitutes a discrete prominent mesenchymal component, wedged in between the major cushions. This new model for atrioventricular septation may provide novel insights into understanding the etiology of congenital cardiac malformations.
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Affiliation(s)
- Brian S. Snarr
- Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Medical University of South Carolina, Charleston, South Carolina
| | - Elaine E. Wirrig
- Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Medical University of South Carolina, Charleston, South Carolina
| | - Aimee L. Phelps
- Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Medical University of South Carolina, Charleston, South Carolina
| | - Thomas C. Trusk
- Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Medical University of South Carolina, Charleston, South Carolina
| | - Andy Wessels
- Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Medical University of South Carolina, Charleston, South Carolina
- Department of Pediatrics, Division of Pediatric Cardiology, Medical University of South Carolina, Charleston, South Carolina
- Correspondence to: Andy Wessels, Ph.D., Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Medical University of South Carolina, 173 Ashley Avenue, Basic Science Building, Room 648B, P.O. Box 250508, Charleston, SC 29425.
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204
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Alaynick WA, Kondo RP, Xie W, He W, Dufour CR, Downes M, Jonker JW, Giles W, Naviaux RK, Giguère V, Evans RM. ERRgamma directs and maintains the transition to oxidative metabolism in the postnatal heart. Cell Metab 2007; 6:13-24. [PMID: 17618853 DOI: 10.1016/j.cmet.2007.06.007] [Citation(s) in RCA: 241] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Revised: 05/15/2007] [Accepted: 06/19/2007] [Indexed: 10/23/2022]
Abstract
At birth, the heart undergoes a critical metabolic switch from a predominant dependence on carbohydrates during fetal life to a greater dependence on postnatal oxidative metabolism. This remains the principle metabolic state throughout life, although pathologic conditions such as heart failure and cardiac hypertrophy reactivate components of the fetal genetic program to increase carbohydrate utilization. Disruption of the ERRgamma gene (Esrrg), which is expressed at high levels in the fetal and postnatal mouse heart, blocks this switch, resulting in lactatemia, electrocardiographic abnormalities, and death during the first week of life. Genomic ChIP-on-chip and expression analysis identifies ERRgamma as both a direct and an indirect regulator of a nuclear-encoded mitochondrial genetic network that coordinates the postnatal metabolic transition. These findings reveal an unexpected and essential molecular genetic component of the oxidative metabolic gene program in the heart and highlight ERRgamma in the study of cardiac hypertrophy and failure.
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Affiliation(s)
- William A Alaynick
- Howard Hughes Medical Institute and Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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205
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Blaschke RJ, Hahurij ND, Kuijper S, Just S, Wisse LJ, Deissler K, Maxelon T, Anastassiadis K, Spitzer J, Hardt SE, Schöler H, Feitsma H, Rottbauer W, Blum M, Meijlink F, Rappold G, Gittenberger-de Groot AC. Targeted mutation reveals essential functions of the homeodomain transcription factor Shox2 in sinoatrial and pacemaking development. Circulation 2007; 115:1830-8. [PMID: 17372176 DOI: 10.1161/circulationaha.106.637819] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND Identifying molecular pathways regulating the development of pacemaking and coordinated heartbeat is crucial for a comprehensive mechanistic understanding of arrhythmia-related diseases. Elucidation of these pathways has been complicated mainly by an insufficient definition of the developmental structures involved in these processes and the unavailability of animal models specifically targeting the relevant tissues. Here, we report on a highly restricted expression pattern of the homeodomain transcription factor Shox2 in the sinus venosus myocardium, including the sinoatrial nodal region and the venous valves. METHODS AND RESULTS To investigate its function in vivo, we have generated mouse lines carrying a targeted mutation of the Shox2 gene. Although heterozygous animals did not exhibit obvious defects, homozygosity of the targeted allele led to embryonic lethality at 11.5 to 13.5 dpc. Shox2-/- embryos exhibited severe hypoplasia of the sinus venosus myocardium in the posterior heart field, including the sinoatrial nodal region and venous valves. We furthermore demonstrate aberrant expression of connexin 40 and connexin 43 and the transcription factor Nkx2.5 in vivo specifically within the sinoatrial nodal region and show that Shox2 deficiency interferes with pacemaking function in zebrafish embryos. CONCLUSIONS From these results, we postulate a critical function of Shox2 in the recruitment of sinus venosus myocardium comprising the sinoatrial nodal region.
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206
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Soufan AT, van den Berg G, Moerland PD, Massink MMG, van den Hoff MJB, Moorman AFM, Ruijter JM. Three-dimensional measurement and visualization of morphogenesis applied to cardiac embryology. J Microsc 2007; 225:269-74. [PMID: 17371450 DOI: 10.1111/j.1365-2818.2007.01742.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Volume growth and proliferation are key processes in heart morphogenesis, yet their regionalization during development of the heart has been described only anecdotally. To study the contribution of cardiomyocyte proliferation to heart development, a quantitative reconstruction method was designed, allowing the local mapping of this morphogenetic process. First, a morphological surface reconstruction is made of the heart, using sections stained specifically for cardiomyocytes. Then, by a comprehensive series of image processing steps, local three-dimensional (3D) information of proliferation is obtained. These local quantitative data are then mapped onto the morphological surface reconstruction, resulting in a reconstruction that not only provides morphological information (qualitative), but also displays local information on proliferation rate (quantitative). The resulting 3D quantitative reconstructions revealed novel observations regarding the morphogenesis of the heart.
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Affiliation(s)
- A T Soufan
- Heart Failure Research Center, Department of Anatomy and Embryology, Academic Research Center, 1105 AZ, Amsterdam, The Netherlands
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207
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Viswanathan S, Burch JBE, Fishman GI, Moskowitz IP, Benson DW. Characterization of sinoatrial node in four conduction system marker mice. J Mol Cell Cardiol 2007; 42:946-53. [PMID: 17459410 PMCID: PMC1936434 DOI: 10.1016/j.yjmcc.2007.02.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Revised: 01/22/2007] [Accepted: 02/14/2007] [Indexed: 11/30/2022]
Abstract
The specialized cardiac conduction system (CCS) consists of the sinoatrial node (SAN) and the atrioventricular (AV) conduction system (AVCS), which includes proximal (AV node, bundle of His and bundle branches) and distal (Purkinje fibers) components. In four CCS marker mice [two transgenic (cGATA6|lacZ, CCS|lacZ) and two targeted gene knock-in (minK|lacZ, Hop|lacZ)] the expression of the lacZ gene (beta-gal) has been reported to mark portions of the proximal and distal AVCS; the expression of this marker in the adult SAN is unknown. The primary objective of this study was to analyze the utility of these marker mice in the identification of the SAN. Intercaval and interventricular septal regions, containing all the components of the CCS, were freshly dissected from adult mice based on the anatomical landmarks and sectioned. Immunohistochemical characterization was performed with SAN markers (Cx45, HCN4), compared to the reporter expression (beta-gal) and markers of the working myocardium (Cx40 and Cx43). In all four of the CCS marker mice, we found that beta-gal expression is consistently observed in the proximal and distal AVCS. However, the presence of lacZ gene expression in the working myocardium outside the CCS and/or the absence of this reporter expression in the SAN prevent the effective use of these mice to identify the SAN, leading us to conclude that none of the four CCS marker mice we studied specifically mark the SAN.
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Affiliation(s)
- S Viswanathan
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, USA
| | - JBE Burch
- Department of Cell and Developmental Biology, Fox Chase Cancer Center, Philadelphia, USA
| | - GI Fishman
- Leon H. Charney Division of Cardiology, New York University School of Medicine, New York, USA
| | - IP Moskowitz
- Departments of Pediatrics, Institute for Molecular Pediatric Sciences, and Pathology, Pritzker School of Medicine, University of Chicago, Chicago, USA
| | - DW Benson
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, USA
- Corresponding Author D. Woodrow Benson, MD, PhD Cardiology Division MLC 7042 Cincinnati Children's Hospital Medical Center 3333 Burnet Avenue Cincinnati, Ohio 45229 Phone: 513-636-7716, Fax: 513-636-5958 E-mail:
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208
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Mommersteeg MTM, Hoogaars WMH, Prall OWJ, de Gier-de Vries C, Wiese C, Clout DEW, Papaioannou VE, Brown NA, Harvey RP, Moorman AFM, Christoffels VM. Molecular pathway for the localized formation of the sinoatrial node. Circ Res 2007; 100:354-62. [PMID: 17234970 DOI: 10.1161/01.res.0000258019.74591.b3] [Citation(s) in RCA: 254] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The sinoatrial node, which resides at the junction of the right atrium and the superior caval vein, contains specialized myocardial cells that initiate the heart beat. Despite this fundamental role in heart function, the embryonic origin and mechanisms of localized formation of the sinoatrial node have not been defined. Here we show that subsequent to the formation of the Nkx2-5-positive heart tube, cells bordering the inflow tract of the heart tube give rise to the Nkx2-5-negative myocardial cells of the sinoatrial node and the sinus horns. Using genetic models, we show that as the myocardium of the heart tube matures, Nkx2-5 suppresses pacemaker channel gene Hcn4 and T-box transcription factor gene Tbx3, thereby enforcing a progressive confinement of their expression to the forming Nkx2-5-negative sinoatrial node and sinus horns. Thus, Nkx2-5 is essential for establishing a gene expression border between the atrium and sinoatrial node. Tbx3 was found to suppress chamber differentiation, providing an additional mechanism by which the Tbx3-positive sinoatrial node is shielded from differentiating into atrial myocardium. Pitx2c-deficient fetuses form sinoatrial nodes with indistinguishable molecular signatures at both the right and left sinuatrial junction, indicating that Pitx2c functions within the left/right pathway to suppress a default program for sinuatrial node formation on the left. Our molecular pathway provides a mechanism for how pacemaker activity becomes progressively relegated to the most recently added components of the venous pole of the heart and, ultimately, to the junction of the right atrium and superior caval vein.
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Affiliation(s)
- Mathilda T M Mommersteeg
- Center for Heart Failure Research, Academic Medical Centre, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands
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209
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Dunwoodie SL. Combinatorial signaling in the heart orchestrates cardiac induction, lineage specification and chamber formation. Semin Cell Dev Biol 2007; 18:54-66. [PMID: 17236794 DOI: 10.1016/j.semcdb.2006.12.003] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The complexity of mammalian cardiogenesis is compounded, as the heart must function in the embryo whilst it is still being formed. Great advances have been made recently as additional cardiac progenitor cell populations have been identified. The induction and maintenance of these progenitors, and their deployment to the developing heart relies on combinatorial molecular signalling, a feature also of cardiac chamber formation. Many forms of congenital heart disease in humans are likely to arise from defects in the early stages of heart development; therefore it is important to understand the molecular pathways that underlie some of the key events that shape the heart during the early stages of it development.
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Affiliation(s)
- Sally L Dunwoodie
- Developmental Biology Program, Victor Chang Cardiac Research Institute, 384 Victoria Street, Darlinghurst, NSW, Australia.
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210
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Gittenberger-de Groot AC, Mahtab EAF, Hahurij ND, Wisse LJ, Deruiter MC, Wijffels MCEF, Poelmann RE. Nkx2.5-negative myocardium of the posterior heart field and its correlation with podoplanin expression in cells from the developing cardiac pacemaking and conduction system. Anat Rec (Hoboken) 2007; 290:115-22. [PMID: 17441204 DOI: 10.1002/ar.20406] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Recent advances in the study of cardiac development have shown the relevance of addition of myocardium to the primary myocardial heart tube. In wild-type mouse embryos (E9.5-15.5), we have studied the myocardium at the venous pole of the heart using immunohistochemistry and 3D reconstructions of expression patterns of MLC-2a, Nkx2.5, and podoplanin, a novel coelomic and myocardial marker. Podoplanin-positive coelomic epithelium was continuous with adjacent podoplanin- and MLC-2a-positive myocardium that formed a conspicuous band along the left cardinal vein extending through the base of the atrial septum to the posterior myocardium of the atrioventricular canal, the atrioventricular nodal region, and the His-Purkinje system. Later on, podoplanin expression was also found in the myocardium surrounding the pulmonary vein. On the right side, podoplanin-positive cells were seen along the right cardinal vein, which during development persisted in the sinoatrial node and part of the venous valves. In the MLC-2a- and podoplanin-positive myocardium, Nkx2.5 expression was absent in the sinoatrial node and the wall of the cardinal veins. There was a mosaic positivity in the wall of the common pulmonary vein and the atrioventricular conduction system as opposed to the overall Nkx2.5 expression seen in the chamber myocardium. We conclude that we have found podoplanin as a marker that links a novel Nkx2.5-negative sinus venosus myocardial area, which we refer to as the posterior heart field, with the cardiac conduction system.
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211
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