151
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Liu Q, Chen Y, Auger-Messier M, Molkentin JD. Interaction between NFκB and NFAT coordinates cardiac hypertrophy and pathological remodeling. Circ Res 2012; 110:1077-86. [PMID: 22403241 DOI: 10.1161/circresaha.111.260729] [Citation(s) in RCA: 142] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
RATIONALE Both nuclear factors of activated T cells (NFAT) and nuclear factor-κB (NFκB) are Rel homology domain (RHD)-containing transcription factors whose independent activities are critically involved in regulating cardiac hypertrophy and failure. OBJECTIVE To determine the potential functional interaction between NFAT and NFκB signaling pathways in cardiomyocytes and its role in cardiac hypertrophy and remodeling. METHODS AND RESULTS We identified a novel transcriptional regulatory mechanism whereby NFκB and NFAT directly interact and synergistically promote transcriptional activation in cardiomyocytes. We show that the p65 subunit of NFκB coimmunoprecipitates with NFAT in cardiomyocytes, and this interaction maps to the RHD within p65. Overexpression of the p65-RHD disrupts the association between endogenous p65 and NFATc1, leading to reduced transcriptional activity. Overexpression of IκB kinase β (IKKβ) or p65-RHD causes nuclear translocation of NFATc1, and expression of a constitutively nuclear NFATc1-SA mutant similarly facilitated p65 nuclear translocation. Combined overexpression of p65 and NFATc1 promotes synergistic activation of NFAT transcriptional activity in cardiomyocytes, whereas inhibition of NFκB with IκBαM or dominant negative IKKβ reduces NFAT activity. Importantly, agonist-induced NFAT activation is reduced in p65 null mouse embryonic fibroblasts (MEFs) compared with wild-type MEFs. In vivo, cardiac-specific deletion of p65 using a Cre-loxP system causes a ≈50% reduction in NFAT activity in luciferase reporter mice. Moreover, ablation of p65 in the mouse heart decreases the hypertrophic response after pressure overload stimulation, reduces the degree of pathological remodeling, and preserves contractile function. CONCLUSIONS Our results suggest a direct interaction between NFAT and NFκB that effectively integrates 2 disparate signaling pathways in promoting cardiac hypertrophy and ventricular remodeling.
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Affiliation(s)
- Qinghang Liu
- Department of Physiology and Biophysics, University of Washington, Seattle, USA
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152
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Hashimoto S, Chen H, Que J, Brockway BL, Drake JA, Snyder JC, Randell SH, Stripp BR. β-Catenin-SOX2 signaling regulates the fate of developing airway epithelium. J Cell Sci 2012; 125:932-42. [PMID: 22421361 PMCID: PMC3311930 DOI: 10.1242/jcs.092734] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Wnt-β-catenin signaling regulates cell fate during organ development and postnatal tissue maintenance, but its contribution to specification of distinct lung epithelial lineages is still unclear. To address this question, we used a Cre recombinase (Cre)-LoxP approach to activate canonical Wnt signaling ectopically in developing lung endoderm. We found that persistent activation of canonical Wnt signaling within distal lung endoderm was permissive for normal development of alveolar epithelium, yet led to the loss of developing bronchiolar epithelium and ectasis of distal conducting airways. Activation of canonical Wnt led to ectopic expression of a lymphoid-enhancing factor and a T-cell factor (LEF and TCF, respectively) and absence of SRY (sex-determining region Y)-box 2 (SOX2) and tumor protein p63 (p63) expression in proximal derivatives. Conditional loss of SOX2 in airways phenocopied epithelial differentiation defects observed with ectopic activation of canonical Wnt. Our data suggest that Wnt negatively regulates a SOX2-dependent signaling program required for developmental progression of the bronchiolar lineage.
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Affiliation(s)
- Shuichi Hashimoto
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, 106 Research Drive, 2075 MSRBII, DUMC Box 103000, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University Medical Center, Box 3709, Durham, NC, 27710, USA
| | - Huaiyong Chen
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, 106 Research Drive, 2075 MSRBII, DUMC Box 103000, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University Medical Center, Box 3709, Durham, NC, 27710, USA
| | - Jianwen Que
- Department of Cell Biology, Duke University Medical Center, Box 3709, Durham, NC, 27710, USA
| | - Brian L. Brockway
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, 106 Research Drive, 2075 MSRBII, DUMC Box 103000, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University Medical Center, Box 3709, Durham, NC, 27710, USA
| | - Jeffrey A. Drake
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, 106 Research Drive, 2075 MSRBII, DUMC Box 103000, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University Medical Center, Box 3709, Durham, NC, 27710, USA
| | - Joshua C. Snyder
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, 106 Research Drive, 2075 MSRBII, DUMC Box 103000, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University Medical Center, Box 3709, Durham, NC, 27710, USA
| | - Scott H. Randell
- Departments of Cell and Molecular Physiology and Medicine, The University of North Carolina at Chapel Hill, 111 Mason Farm Road, 5200 Medical Biomolecular Research Building, CB 7545 Chapel Hill, NC, 27599-7545, USA
| | - Barry R. Stripp
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care Medicine, Duke University Medical Center, 106 Research Drive, 2075 MSRBII, DUMC Box 103000, Durham, NC, 27710, USA
- Department of Cell Biology, Duke University Medical Center, Box 3709, Durham, NC, 27710, USA
- Author for correspondence ()
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153
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He A, Shen X, Ma Q, Cao J, von Gise A, Zhou P, Wang G, Marquez VE, Orkin SH, Pu WT. PRC2 directly methylates GATA4 and represses its transcriptional activity. Genes Dev 2012; 26:37-42. [PMID: 22215809 DOI: 10.1101/gad.173930.111] [Citation(s) in RCA: 205] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Polycomb-repressive complex 2 (PRC2) promotes tissue-specific differentiation by depositing trimethylated histone H3 Lys 27 (H3K27me3) epigenetic marks to silence ectopic gene expression programs. Here, we show that EZH2, the catalytic subunit of PRC2, is required for cardiac morphogenesis. Both in vitro and in fetal hearts, EZH2 interacted with cardiac transcription factor GATA4 and directly methylated it at Lys 299. PRC2 methylation of GATA4 attenuated its transcriptional activity by reducing its interaction with and acetylation by p300. Our results reveal a new mechanism of PRC2-mediated transcriptional repression in which PRC2 methylates a transcription factor to inhibit its transcriptional activity.
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Affiliation(s)
- Aibin He
- Department of Cardiology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts 02115, USA
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154
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Chen L, Ma Y, Kim EY, Yu W, Schwartz RJ, Qian L, Wang J. Conditional ablation of Ezh2 in murine hearts reveals its essential roles in endocardial cushion formation, cardiomyocyte proliferation and survival. PLoS One 2012; 7:e31005. [PMID: 22312437 PMCID: PMC3270034 DOI: 10.1371/journal.pone.0031005] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 12/30/2011] [Indexed: 01/01/2023] Open
Abstract
Ezh2 is a histone trimethyltransferase that silences genes mainly via catalyzing trimethylation of histone 3 lysine 27 (H3K27Me3). The role of Ezh2 as a regulator of gene silencing and cell proliferation in cancer development has been extensively investigated; however, its function in heart development during embryonic cardiogenesis has not been well studied. In the present study, we used a genetically modified mouse system in which Ezh2 was specifically ablated in the mouse heart. We identified a wide spectrum of cardiovascular malformations in the Ezh2 mutant mice, which collectively led to perinatal death. In the Ezh2 mutant heart, the endocardial cushions (ECs) were hypoplastic and the endothelial-to-mesenchymal transition (EMT) process was impaired. The hearts of Ezh2 mutant mice also exhibited decreased cardiomyocyte proliferation and increased apoptosis. We further identified that the Hey2 gene, which is important for cardiomyocyte proliferation and cardiac morphogenesis, is a downstream target of Ezh2. The regulation of Hey2 expression by Ezh2 may be independent of Notch signaling activity. Our work defines an indispensible role of the chromatin remodeling factor Ezh2 in normal cardiovascular development.
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Affiliation(s)
- Li Chen
- Department of Stem Cell Engineering, Basic Research Laboratories, Texas Heart Institute, Houston, Texas, United States of America
| | - Yanlin Ma
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas, United States of America
| | - Eun Young Kim
- Department of Stem Cell Engineering, Basic Research Laboratories, Texas Heart Institute, Houston, Texas, United States of America
- Program in Genes and Development, The University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - Wei Yu
- Department of Biochemistry and Molecular Biology, University of Houston, Houston, Texas, United States of America
| | - Robert J. Schwartz
- Department of Biochemistry and Molecular Biology, University of Houston, Houston, Texas, United States of America
| | - Ling Qian
- Department of Stem Cell Engineering, Basic Research Laboratories, Texas Heart Institute, Houston, Texas, United States of America
| | - Jun Wang
- Department of Stem Cell Engineering, Basic Research Laboratories, Texas Heart Institute, Houston, Texas, United States of America
- * E-mail:
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155
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Zhang Y, Ruest LB. Analysis of neural crest cell fate during cardiovascular development using Cre-activated lacZ/β-galactosidase staining. Methods Mol Biol 2012; 843:125-138. [PMID: 22222527 DOI: 10.1007/978-1-61779-523-7_12] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
It is important to identify the mechanisms regulating cardiovascular development. However, complex genetic tools are often required, including transgenic animals that express the lacZ transgene encoding the β-galactosidase enzyme under the control of a specific promoter or following recombination with the Cre recombinase. The latter can be useful for identifying specific cell populations of the developing cardiovascular system, including neural crest cells. The tracking of these cells can help clarify their fate in mutant embryos and elucidate the etiology of some congenital cardiovascular birth defects. This chapter highlights the methods used to stain embryonic tissues in whole mount or sections to detect the expression of the lacZ transgene with a focus on tracking cardiac neural crest cells using the Wnt1-Cre and R26R mouse lines. We also provide a protocol using fluorescence-activated cell sorting for collecting neural crest cells for further analysis. These protocols can be used with any embryos expressing Cre and lacZ.
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Affiliation(s)
- Yanping Zhang
- Department of Biomedical Sciences, Texas A&M Healthy Science Center-Baylor College of Dentistry, Dallas, TX, USA
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156
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Taubenschmid J, Weitzer G. Mechanisms of cardiogenesis in cardiovascular progenitor cells. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 293:195-267. [PMID: 22251563 PMCID: PMC7615846 DOI: 10.1016/b978-0-12-394304-0.00012-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Self-renewing cells of the vertebrate heart have become a major subject of interest in the past decade. However, many researchers had a hard time to argue against the orthodox textbook view that defines the heart as a postmitotic organ. Once the scientific community agreed on the existence of self-renewing cells in the vertebrate heart, their origin was again put on trial when transdifferentiation, dedifferentiation, and reprogramming could no longer be excluded as potential sources of self-renewal in the adult organ. Additionally, the presence of self-renewing pluripotent cells in the peripheral blood challenges the concept of tissue-specific stem and progenitor cells. Leaving these unsolved problems aside, it seems very desirable to learn about the basic biology of this unique cell type. Thus, we shall here paint a picture of cardiovascular progenitor cells including the current knowledge about their origin, basic nature, and the molecular mechanisms guiding proliferation and differentiation into somatic cells of the heart.
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Affiliation(s)
- Jasmin Taubenschmid
- Max F. Perutz Laboratories, Department of Medical Biochemistry, Medical University of Vienna, Vienna, Austria
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157
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Zhang J, Liu J, Huang Y, Chang JYF, Liu L, McKeehan WL, Martin JF, Wang F. FRS2α-mediated FGF signals suppress premature differentiation of cardiac stem cells through regulating autophagy activity. Circ Res 2011; 110:e29-39. [PMID: 22207710 DOI: 10.1161/circresaha.111.255950] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
RATIONALE Although the fibroblast growth factor (FGF) signaling axis plays important roles in heart development, the molecular mechanism by which the FGF regulates cardiogenesis is not fully understood. OBJECTIVE To investigate the mechanism by which FGF signaling regulates cardiac progenitor cell differentiation. METHODS AND RESULTS Using mice with tissue-specific ablation of FGF receptors and FGF receptor substrate 2α (Frs2α) in heart progenitor cells, we demonstrate that disruption of FGF signaling leads to premature differentiation of cardiac progenitor cells in mice. Using embryoid body cultures of mouse embryonic stem cells, we reveal that FGF signaling promotes mesoderm differentiation in embryonic stem cells but inhibits cardiomyocyte differentiation of the mesoderm cells at later stages. Furthermore, we also report that inhibiting FRS2α-mediated signals increases autophagy and that activating autophagy promotes myocardial differentiation and vice versa. CONCLUSIONS The results indicate that the FGF/FRS2α-mediated signals prevent premature differentiation of heart progenitor cells through suppressing autophagy. The findings provide the first evidence that autophagy plays a role in heart progenitor differentiation.
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Affiliation(s)
- Jue Zhang
- Center for Cancer and Stem Cell Biology, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX 77030-3303, USA
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158
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Tbx20 regulation of cardiac cell proliferation and lineage specialization during embryonic and fetal development in vivo. Dev Biol 2011; 363:234-46. [PMID: 22226977 DOI: 10.1016/j.ydbio.2011.12.034] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 11/29/2011] [Accepted: 12/20/2011] [Indexed: 11/21/2022]
Abstract
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.
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159
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Rawlins EL, Perl AK. The a"MAZE"ing world of lung-specific transgenic mice. Am J Respir Cell Mol Biol 2011; 46:269-82. [PMID: 22180870 DOI: 10.1165/rcmb.2011-0372ps] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The purpose of this review is to give a comprehensive overview of transgenic mouse lines suitable for studying gene function and cellular lineage relationships in lung development, homeostasis, injury, and repair. Many of the mouse strains reviewed in this Perspective have been widely shared within the lung research community, and new strains are continuously being developed. There are many transgenic lines that target subsets of lung cells, but it remains a challenge for investigators to select the correct transgenic modules for their experiment. This review covers the tetracycline- and tamoxifen-inducible systems and focuses on conditional lines that target the epithelial cells. We point out the limitations of each strain so investigators can choose the system that will work best for their scientific question. Current mesenchymal and endothelial lines are limited by the fact that they are not lung specific. These lines are summarized in a brief overview. In addition, useful transgenic reporter mice for studying lineage relationships, promoter activity, and signaling pathways will complete our lung-specific conditional transgenic mouse shopping list.
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Affiliation(s)
- Emma L Rawlins
- Children's Hospital Medical Center, Divisions of Neonatology and Pulmonary Biology, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA
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160
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He A, Ma Q, Cao J, von Gise A, Zhou P, Xie H, Zhang B, Hsing M, Christodoulou DC, Cahan P, Daley GQ, Kong SW, Orkin SH, Seidman CE, Seidman JG, Pu WT. Polycomb repressive complex 2 regulates normal development of the mouse heart. Circ Res 2011; 110:406-15. [PMID: 22158708 DOI: 10.1161/circresaha.111.252205] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
RATIONALE Epigenetic marks are crucial for organogenesis, but their role in heart development is poorly understood. Polycomb repressive complex 2 (PRC2) trimethylates histone H3 at lysine 27, which establishes H3K27me3 repressive epigenetic marks that promote tissue-specific differentiation by silencing ectopic gene programs. OBJECTIVE We studied the function of PRC2 in murine heart development using a tissue-restricted conditional inactivation strategy. METHODS AND RESULTS Inactivation of the PRC2 subunit Ezh2 by Nkx2-5(Cre) (Ezh2(NK)) caused lethal congenital heart malformations, namely, compact myocardial hypoplasia, hypertrabeculation, and ventricular septal defect. Candidate and genome-wide RNA expression profiling and chromatin immunoprecipitation analyses of Ezh2(NK) heart identified genes directly repressed by EZH2. Among these were the potent cell cycle inhibitors Ink4a/b (inhibitors of cyclin-dependent kinase 4 A and B), the upregulation of which was associated with decreased cardiomyocyte proliferation in Ezh2(NK). EZH2-repressed genes were enriched for transcriptional regulators of noncardiomyocyte expression programs such as Pax6, Isl1, and Six1. EZH2 was also required for proper spatiotemporal regulation of cardiac gene expression, because Hcn4, Mlc2a, and Bmp10 were inappropriately upregulated in ventricular RNA. PRC2 was also required later in heart development, as indicated by cardiomyocyte-restricted TNT-Cre inactivation of the PRC2 subunit Eed. However, Ezh2 inactivation by TNT-Cre did not cause an overt phenotype, likely because of functional redundancy with Ezh1. Thus, early Ezh2 inactivation by Nk2-5(Cre) caused later disruption of cardiomyocyte gene expression and heart development. CONCLUSIONS Our study reveals a previously undescribed role of EZH2 in regulating heart formation and shows that perturbation of the epigenetic landscape early in cardiogenesis has sustained disruptive effects at later developmental stages.
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Affiliation(s)
- Aibin He
- Department of Cardiology, Children's Hospital Boston, MA, USA
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161
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Enhanced desumoylation in murine hearts by overexpressed SENP2 leads to congenital heart defects and cardiac dysfunction. J Mol Cell Cardiol 2011; 52:638-49. [PMID: 22155005 DOI: 10.1016/j.yjmcc.2011.11.011] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 11/16/2011] [Accepted: 11/18/2011] [Indexed: 12/29/2022]
Abstract
Sumoylation is a posttranslational modification implicated in a variety of cellular activities, and its role in a number of human pathogeneses such as cleft lip/palate has been well documented. However, the importance of the SUMO conjugation pathway in cardiac development and functional disorders is newly emerging. We previously reported that knockout of SUMO-1 in mice led to congenital heart diseases (CHDs). To further investigate the effects of imbalanced SUMO conjugation on heart development and function and its underlying mechanisms, we generated transgenic (Tg) mice with cardiac-specific expression of SENP2, a SUMO-specific protease that deconjugates sumoylated proteins, to evaluate the impact of desumoylation on heart development and function. Overexpression of SENP2 resulted in premature death of mice with CHDs-atrial septal defects (ASDs) and/or ventricular septal defects (VSDs). Immunobiochemistry revealed diminished cardiomyocyte proliferation in SENP2-Tg mouse hearts compared with that in wild type (WT) hearts. Surviving SENP2-Tg mice showed growth retardation, and developed cardiomyopathy with impaired cardiac function with aging. Cardiac-specific overexpression of the SUMO-1 transgene reduced the incidence of cardiac structural phenotypes in the sumoylation defective mice. Moreover, cardiac overexpression of SENP2 in the mice with Nkx2.5 haploinsufficiency promoted embryonic lethality and severity of CHDs, indicating the functional interaction between SENP2 and Nkx2.5 in vivo. Our findings indicate the indispensability of a balanced SUMO pathway for proper cardiac development and function. This article is part of a Special Issue entitled 'Post-translational Modification SI'.
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162
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Chen Y, Liu Y, Dorn GW. Mitochondrial fusion is essential for organelle function and cardiac homeostasis. Circ Res 2011; 109:1327-31. [PMID: 22052916 DOI: 10.1161/circresaha.111.258723] [Citation(s) in RCA: 394] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
RATIONALE Mitochondria constitute 30% of myocardial mass. Mitochondrial fusion and fission appear essential for health of most tissues. Mitochondrial fission occurs in neonatal cardiomycyte and is implicated in cardiomyocyte death. Mitochondrial fusion has not been observed in postmitotic myocytes of adult hearts, and its occurrence and function in this context are controversial. OBJECTIVE Determine the consequences on organelle and organ function of disrupting cardiomyocyte mitochondrial fusion in vivo. METHODS AND RESULTS The murine mfn1 and mfn2 genes, encoding mitofusins (Mfn) 1 and 2 that mediate mitochondrial tethering and outer mitochondrial membrane fusion, were interrupted by Cre-mediated excision of essential exons in neonatal (Nkx2.5-Cre) and adult (MYH6 modified estrogen receptor-Cre-modified estrogen receptor plus tamoxifen or Raloxifene) hearts. Embryonic combined Mfn1/Mfn2 ablation was lethal after e9.5. Conditional combined Mfn1/Mfn2 ablation in adult hearts induced mitochondrial fragmentation, cardiomyocyte and mitochondrial respiratory dysfunction, and rapidly progressive and lethal dilated cardiomyopathy. Before heart failure developed, cardiomyocyte shortening and calcium cycling were unaffected by absence of Mfn1 and Mfn2. Based on the time course over which fusion-defective mitochondrial size decreases, a mitochondrial fusion/fission cycle in adult mouse hearts occurs approximately every 16 days. CONCLUSIONS Mitochondrial fusion in adult cardiac myocytes is necessary to maintain normal mitochondrial morphology and is essential for normal cardiac respiratory and contractile function. Interruption of mitochondrial fusion causes lethal cardiac failure at a time corresponding to 3 or 4 cycles of unopposed mitochondrial fission.
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Affiliation(s)
- Yun Chen
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
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163
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Xin M, Kim Y, Sutherland LB, Qi X, McAnally J, Schwartz RJ, Richardson JA, Bassel-Duby R, Olson EN. Regulation of insulin-like growth factor signaling by Yap governs cardiomyocyte proliferation and embryonic heart size. Sci Signal 2011; 4:ra70. [PMID: 22028467 DOI: 10.1126/scisignal.2002278] [Citation(s) in RCA: 397] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The Hippo signaling pathway regulates growth of the heart and other tissues. Hippo pathway kinases influence the activity of various targets, including the transcriptional coactivator Yap, but the specific role of Yap in heart growth has not been investigated. We show that Yap is necessary and sufficient for embryonic cardiac growth in mice. Deletion of Yap in the embryonic mouse heart impeded cardiomyocyte proliferation, causing myocardial hypoplasia and lethality at embryonic stage 10.5. Conversely, forced expression of a constitutively active form of Yap in the embryonic heart increased cardiomyocyte number and heart size. Yap activated the insulin-like growth factor (IGF) signaling pathway in cardiomyocytes, resulting in inactivation of glycogen synthase kinase 3β, which led to increased abundance of β-catenin, a positive regulator of cardiac growth. Our results point to Yap as a critical downstream effector of the Hippo pathway in the control of cardiomyocyte proliferation and a nexus for coupling the IGF, Wnt, and Hippo signaling pathways with the developmental program for heart growth.
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Affiliation(s)
- Mei Xin
- Department of Molecular Biology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9148, USA
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164
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Bolte C, Zhang Y, Wang IC, Kalin TV, Molkentin JD, Kalinichenko VV. Expression of Foxm1 transcription factor in cardiomyocytes is required for myocardial development. PLoS One 2011; 6:e22217. [PMID: 21779394 PMCID: PMC3136509 DOI: 10.1371/journal.pone.0022217] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 06/17/2011] [Indexed: 12/23/2022] Open
Abstract
Forkhead Box M1 (Foxm1) is a transcription factor essential for organ morphogenesis and development of various cancers. Although complete deletion of Foxm1 in Foxm1(-/-) mice caused embryonic lethality due to severe abnormalities in multiple organ systems, requirements for Foxm1 in cardiomyocytes remain to be determined. This study was designed to elucidate the cardiomyocyte-autonomous role of Foxm1 signaling in heart development. We generated a new mouse model in which Foxm1 was specifically deleted from cardiomyocytes (Nkx2.5-Cre/Foxm1(fl/f) mice). Deletion of Foxm1 from cardiomyocytes was sufficient to disrupt heart morphogenesis and induce embryonic lethality in late gestation. Nkx2.5-Cre/Foxm1(fl/fl) hearts were dilated with thinning of the ventricular walls and interventricular septum, as well as disorganization of the myocardium which culminated in cardiac fibrosis and decreased capillary density. Cardiomyocyte proliferation was diminished in Nkx2.5-Cre/Foxm1(fl/fl) hearts owing to altered expression of multiple cell cycle regulatory genes, such as Cdc25B, Cyclin B(1), Plk-1, nMyc and p21(cip1). In addition, Foxm1 deficient hearts displayed reduced expression of CaMKIIδ, Hey2 and myocardin, which are critical mediators of cardiac function and myocardial growth. Our results indicate that Foxm1 expression in cardiomyocytes is critical for proper heart development and required for cardiomyocyte proliferation and myocardial growth.
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Affiliation(s)
- Craig Bolte
- Division of Pulmonary Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America
| | - Yufang Zhang
- Division of Pulmonary Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America
| | - I-Ching Wang
- Division of Pulmonary Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America
| | - Tanya V. Kalin
- Division of Pulmonary Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America
| | - Jeffrey D. Molkentin
- Division Molecular Cardiovascular Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, USA
| | - Vladimir V. Kalinichenko
- Division of Pulmonary Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America
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165
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Cheng Z, Sundberg-Smith LJ, Mangiante LE, Sayers RL, Hakim ZS, Musunuri S, Maguire CT, Majesky MW, Zhou Z, Mack CP, Taylor JM. Focal adhesion kinase regulates smooth muscle cell recruitment to the developing vasculature. Arterioscler Thromb Vasc Biol 2011; 31:2193-202. [PMID: 21757658 DOI: 10.1161/atvbaha.111.232231] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
OBJECTIVE The investment of newly formed endothelial cell tubes with differentiated smooth muscle cells (SMC) is critical for appropriate vessel formation, but the underlying mechanisms remain unknown. We previously showed that depletion of focal adhesion kinase (FAK) in the nkx2.5 expression domain led to aberrant outflow tract (OFT) morphogenesis and strove herein to determine the cell types and mechanisms involved. METHODS AND RESULTS We crossed fak(loxp) targeted mice with available Cre drivers to deplete FAK in OFT SMC (FAK(wnt) and FAK(nk)) or coronary SMC (FAK(cSMC)). In each case, depletion of FAK led to defective vasculogenesis that was incompatible with postnatal life. Immunohistochemical analysis of the mutant vascular structures revealed that FAK was not required for progenitor cell proliferation, survival, or differentiation into SMC but was necessary for subsequent SMC recruitment to developing vasculature. Using a novel FAK-null SMC culture model, we found that depletion of FAK did not influence SMC growth or survival, but blocked directional SMC motility and invasion toward the potent endothelial-derived chemokine, platelet-derived growth factor PDGFBB. FAK depletion resulted in unstable lamellipodial protrusions due to defective spatial-temporal activation of the small GTPase, Rac-1, and lack of Rac1-dependent recruitment of cortactin (an actin stabilizing protein) to the leading edge. Moreover, FAK null SMC exhibited a significant reduction in stimulated extracellular matrix degradation. CONCLUSIONS FAK drives PDGFBB-stimulated SMC chemotaxis/invasion and is essential for SMC to appropriately populate the aorticopulmonary septum and the coronary vascular plexus.
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Affiliation(s)
- Zhaokang Cheng
- Department of Pathology, University of North Carolina, Chapel Hill, 27599-7525, USA
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166
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Kim EY, Chen L, Ma Y, Yu W, Chang J, Moskowitz IP, Wang J. Expression of sumoylation deficient Nkx2.5 mutant in Nkx2.5 haploinsufficient mice leads to congenital heart defects. PLoS One 2011; 6:e20803. [PMID: 21677783 PMCID: PMC3108998 DOI: 10.1371/journal.pone.0020803] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 05/12/2011] [Indexed: 12/16/2022] Open
Abstract
Nkx2.5 is a cardiac specific homeobox gene critical for normal heart development. We previously identified Nkx2.5 as a target of sumoylation, a posttranslational modification implicated in a variety of cellular activities. Sumoylation enhanced Nkx2.5 activity via covalent attachment to the lysine residue 51, the primary SUMO acceptor site. However, how sumoylation regulates the activity of Nkx2.5 in vivo remains unknown. We generated transgenic mice overexpressing sumoylation deficient mutant K51R (conversion of lysine 51 to arginine) specifically in mouse hearts under the control of cardiac α-myosin heavy chain (α-MHC) promoter (K51R-Tg). Expression of the Nkx2.5 mutant transgene in the wild type murine hearts did not result in any overt cardiac phenotype. However, in the presence of Nkx2.5 haploinsufficiency, cardiomyocyte-specific expression of the Nkx2.5 K51R mutant led to congenital heart diseases (CHDs), accompanied with decreased cardiomyocyte proliferation. Also, a number of human CHDs-associated Nkx2.5 mutants exhibited aberrant sumoylation. Our work demonstrates that altered sumoylation status may underlie the development of human CHDs associated with Nkx2.5 mutants.
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Affiliation(s)
- Eun Young Kim
- Program in Genes and Development, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
| | - Li Chen
- Department of Basic Research Laboratories, Texas Heart Institute, Houston, Texas, United States of America
| | - Yanlin Ma
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas, United States of America
| | - Wei Yu
- Department of Biochemistry and Molecular Biology, University of Houston, Houston, Texas, United States of America
| | - Jiang Chang
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas, United States of America
| | - Ivan P. Moskowitz
- Departments of Pediatrics and Pathology, The University of Chicago, Chicago, Illinois, United States of America
| | - Jun Wang
- Department of Basic Research Laboratories, Texas Heart Institute, Houston, Texas, United States of America
- * E-mail:
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167
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Espinoza-Lewis RA, Liu H, Sun C, Chen C, Jiao K, Chen Y. Ectopic expression of Nkx2.5 suppresses the formation of the sinoatrial node in mice. Dev Biol 2011; 356:359-69. [PMID: 21640717 DOI: 10.1016/j.ydbio.2011.05.663] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2010] [Revised: 04/18/2011] [Accepted: 05/18/2011] [Indexed: 10/18/2022]
Abstract
The sinoatrial node (SAN), functionally known as the pacemaker, regulates the cardiac rhythm or heartbeat. Several genes are expressed in the developing SAN and form a genetic network regulating the fate of the SAN cells. The short stature homeobox gene Shox2 is an important player in the SAN genetic network by regulating the expression of different cardiac conduction molecular markers including the early cardiac differentiation marker Nkx2.5. Here we report that the expression patterns of Shox2 and Nkx2.5 are mutually exclusive from the earliest stages of the venous pole and the SAN formation. We show that tissue specific ectopic expression of Shox2 in the developing mouse heart downregulates the expression of Nkx2.5 and causes cardiac malformations; however, it is not sufficient to induce a SAN cell fate switch in the working myocardium. On the other hand, tissue specific overexpression of Nkx2.5 in the heart leads to severe hypoplasia of the SAN and the venous valves, dis-regulation of the SAN genetic network, and change of the SAN cell fate into working myocardium, and causes embryonic lethality, recapitulating the phenotypes including bradycardia observed in Shox2(-/-) mutants. These results indicate that Nkx2.5 activity is detrimental to the normal formation of the SAN. Taken together, our results demonstrate that Shox2 downregulation of Nkx2.5 is essential for the proper development of the SAN and that Shox2 functions to shield the SAN from becoming working myocardium by acting upstream of Nkx2.5.
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168
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Olaopa M, Zhou HM, Snider P, Wang J, Schwartz RJ, Moon AM, Conway SJ. Pax3 is essential for normal cardiac neural crest morphogenesis but is not required during migration nor outflow tract septation. Dev Biol 2011; 356:308-22. [PMID: 21600894 DOI: 10.1016/j.ydbio.2011.05.583] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 05/03/2011] [Accepted: 05/04/2011] [Indexed: 11/17/2022]
Abstract
Systemic loss-of-function studies have demonstrated that Pax3 transcription factor expression is essential for dorsal neural tube, early neural crest and muscle cell lineage morphogenesis. Cardiac neural crest cells participate in both remodeling of the pharyngeal arch arteries and outflow tract septation during heart development, but the lineage specific role of Pax3 in neural crest function has not yet been determined. To gain insight into the requirement of Pax3 within the neural crest, we conditionally deleted Pax3 in both the premigratory and migratory neural crest populations via Wnt1-Cre and Ap2α-Cre and via P0-Cre in only the migratory neural crest, and compared these phenotypes to the pulmonary atresia phenotype observed following the systemic loss of Pax3. Surprisingly, using Wnt1-Cre deletion there are no resultant heart defects despite the loss of Pax3 from the premigratory and migratory neural crest. In contrast, earlier premigratory and migratory Ap2α-Cre mediated deletion resulted in double outlet right ventricle alignment heart defects. In order to assess the tissue-specific contribution of neural crest to heart development, genetic ablation of neural crest lineage using a Wnt1-Cre-activated diphtheria toxin fragment-A cell-killing system was employed. Significantly, ablation of Wnt1-Cre-expressing neural crest cells resulted in fully penetrant persistent truncus arteriosus malformations. Combined, the data show that Pax3 is essential for early neural crest progenitor formation, but is not required for subsequent cardiac neural crest progeny morphogenesis involving their migration to the heart or septation of the outflow tract.
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Affiliation(s)
- Michael Olaopa
- Developmental Biology and Neonatal Medicine Program, HB Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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169
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Wang J, Chen L, Wen S, Zhu H, Yu W, Moskowitz IP, Shaw GM, Finnell RH, Schwartz RJ. Defective sumoylation pathway directs congenital heart disease. ACTA ACUST UNITED AC 2011; 91:468-76. [PMID: 21563299 DOI: 10.1002/bdra.20816] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 02/17/2011] [Accepted: 02/25/2011] [Indexed: 12/17/2022]
Abstract
Congenital heart defects (CHDs) are the most common of all birth defects, yet molecular mechanism(s) underlying highly prevalent atrial septal defects (ASDs) and ventricular septal defects (VSDs) have remained elusive. We demonstrate the indispensability of "balanced" posttranslational small ubiquitin-like modifier (SUMO) conjugation-deconjugation pathway for normal cardiac development. Both hetero- and homozygous SUMO-1 knockout mice exhibited ASDs and VSDs with high mortality rates, which were rescued by cardiac reexpression of the SUMO-1 transgene. Because SUMO-1 was also involved in cleft lip/palate in human patients, the previous findings provided a powerful rationale to question whether SUMO-1 was mutated in infants born with cleft palates and ASDs. Sequence analysis of DNA from newborn screening blood spots revealed a single 16 bp substitution in the SUMO-1 regulatory promoter of a patient displaying both oral-facial clefts and ASDs. Diminished sumoylation activity whether by genetics, environmental toxins, and/or pharmaceuticals may significantly contribute to susceptibility to the induction of congenital heart disease worldwide. Birth Defects Research (Part A) 2011. © 2011 Wiley-Liss, Inc.
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Affiliation(s)
- Jun Wang
- Center for Stem Cell Engineering, Texas Heart Institute, Houston, TX 77030, USA.
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170
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Heallen T, Zhang M, Wang J, Bonilla-Claudio M, Klysik E, Johnson RL, Martin JF. Hippo pathway inhibits Wnt signaling to restrain cardiomyocyte proliferation and heart size. Science 2011; 332:458-61. [PMID: 21512031 PMCID: PMC3133743 DOI: 10.1126/science.1199010] [Citation(s) in RCA: 833] [Impact Index Per Article: 64.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Genetic regulation of mammalian heart size is poorly understood. Hippo signaling represents an organ-size control pathway in Drosophila, where it also inhibits cell proliferation and promotes apoptosis in imaginal discs. To determine whether Hippo signaling controls mammalian heart size, we inactivated Hippo pathway components in the developing mouse heart. Hippo-deficient embryos had overgrown hearts with elevated cardiomyocyte proliferation. Gene expression profiling and chromatin immunoprecipitation revealed that Hippo signaling negatively regulates a subset of Wnt target genes. Genetic interaction studies indicated that β-catenin heterozygosity suppressed the Hippo cardiomyocyte overgrowth phenotype. Furthermore, the Hippo effector Yap interacts with β-catenin on Sox2 and Snai2 genes. These data uncover a nuclear interaction between Hippo and Wnt signaling that restricts cardiomyocyte proliferation and controls heart size.
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Affiliation(s)
- Todd Heallen
- Institute of Biosciences and Technology, Texas A&M System Health Science Center, 2121 West Holcombe Boulevard, Houston, TX 77030, USA
| | - Min Zhang
- Institute of Biosciences and Technology, Texas A&M System Health Science Center, 2121 West Holcombe Boulevard, Houston, TX 77030, USA
| | - Jun Wang
- Institute of Biosciences and Technology, Texas A&M System Health Science Center, 2121 West Holcombe Boulevard, Houston, TX 77030, USA
| | - Margarita Bonilla-Claudio
- Institute of Biosciences and Technology, Texas A&M System Health Science Center, 2121 West Holcombe Boulevard, Houston, TX 77030, USA
| | - Ela Klysik
- Institute of Biosciences and Technology, Texas A&M System Health Science Center, 2121 West Holcombe Boulevard, Houston, TX 77030, USA
| | - Randy L. Johnson
- Department of Biochemistry and Molecular Biology, M. D. Anderson Cancer Center, Houston, TX 77030, USA
| | - James F. Martin
- Institute of Biosciences and Technology, Texas A&M System Health Science Center, 2121 West Holcombe Boulevard, Houston, TX 77030, USA
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171
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Li P, Cavallero S, Gu Y, Chen THP, Hughes J, Hassan AB, Brüning JC, Pashmforoush M, Sucov HM. IGF signaling directs ventricular cardiomyocyte proliferation during embryonic heart development. Development 2011; 138:1795-805. [PMID: 21429986 DOI: 10.1242/dev.054338] [Citation(s) in RCA: 152] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Secreted factors from the epicardium are believed to be important in directing heart ventricular cardiomyocyte proliferation and morphogenesis, although the specific factors involved have not been identified or characterized adequately. We found that IGF2 is the most prominent mitogen made by primary mouse embryonic epicardial cells and by a newly derived immortalized mouse embryonic epicardial cell line called MEC1. In vivo, Igf2 is expressed in the embryonic mouse epicardium during midgestation heart development. Using a whole embryo culture assay in the presence of inhibitors, we confirmed that IGF signaling is required to activate the ERK proliferation pathway in the developing heart, and that the epicardium is required for this response. Global disruption of the Igf2 gene, or conditional disruption of the two IGF receptor genes Igf1r and Insr together in the myocardium, each resulted in a significant decrease in ventricular wall proliferation and in ventricular wall hypoplasia. Ventricular cardiomyocyte proliferation in mutant embryos was restored to normal at E14.5, concurrent with the establishment of coronary circulation. Our results define IGF2 as a previously unexplored epicardial mitogen that is required for normal ventricular chamber development.
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Affiliation(s)
- Peng Li
- Broad Center for Regenerative Medicine and Stem Cell Research, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
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172
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Li D, Hallett MA, Zhu W, Rubart M, Liu Y, Yang Z, Chen H, Haneline LS, Chan RJ, Schwartz RJ, Field LJ, Atkinson SJ, Shou W. Dishevelled-associated activator of morphogenesis 1 (Daam1) is required for heart morphogenesis. Development 2011; 138:303-15. [PMID: 21177343 DOI: 10.1242/dev.055566] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Dishevelled-associated activator of morphogenesis 1 (Daam1), a member of the formin protein family, plays an important role in regulating the actin cytoskeleton via mediation of linear actin assembly. Previous functional studies of Daam1 in lower species suggest its essential role in Drosophila trachea formation and Xenopus gastrulation. However, its in vivo physiological function in mammalian systems is largely unknown. We have generated Daam1-deficient mice via gene-trap technology and found that Daam1 is highly expressed in developing murine organs, including the heart. Daam1-deficient mice exhibit embryonic and neonatal lethality and suffer multiple cardiac defects, including ventricular noncompaction, double outlet right ventricles and ventricular septal defects. In vivo genetic rescue experiments further confirm that the lethality of Daam1-deficient mice results from the inherent cardiac abnormalities. In-depth analyses have revealed that Daam1 is important for regulating filamentous actin assembly and organization, and consequently for cytoskeletal function in cardiomyocytes, which contributes to proper heart morphogenesis. Daam1 is also found to be important for proper cytoskeletal architecture and functionalities in embryonic fibroblasts. Biochemical analyses indicate that Daam1 does not regulate cytoskeletal organization through RhoA, Rac1 or Cdc42. Our study highlights a crucial role for Daam1 in regulating the actin cytoskeleton and tissue morphogenesis.
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Affiliation(s)
- Deqiang Li
- Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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173
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Young DA, DeQuach JA, Christman KL. Human cardiomyogenesis and the need for systems biology analysis. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2010; 3:666-80. [PMID: 21197666 DOI: 10.1002/wsbm.141] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cardiovascular disease remains the leading cause of death in the Western world and myocardial infarction is one of the primary facets of this disease. The limited natural self-renewal of cardiac muscle following injury and restricted supply of heart transplants has encouraged researchers to investigate other means to stimulate regeneration of damaged myocardium. The plasticity of stem cells toward multiple lineages offers the potential to repair the heart following injury. Embryonic stem cells have been extensively studied for their ability to differentiate into early cardiomyocytes, however, the pathway has only been partially defined and inadequate efficiency limits their clinical applicability. Some studies have shown cardiomyogenesis from adult mesenchymal stem cells, from both bone marrow and adipose tissue, but their differentiation pathway remains poorly detailed and these results remain controversial. Despite promising results using stem cells in animal models of cardiac injury, the driving mechanisms behind their differentiation down a cardiomyogenic pathway have yet to be determined. Currently, there is a paucity of information regarding cardiomyogenesis on the systemic level. Stem cell differentiation results from multiple signaling parameters operating in a tightly regulated spatiotemporal pattern. Investigating this phenomenon from a systems biology perspective could unveil the abstruse mechanisms controlling cardiomyogenesis that would otherwise require extensive in vitro testing.
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Affiliation(s)
- D Adam Young
- Department of Bioengineering, University of California, San Diego, CA, USA
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174
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Abstract
Cardiac fibroblasts play a critical role in maintenance of normal cardiac function. They are indispensable for damage control and tissue remodeling on myocardial injury and principal mediators of pathological cardiac remodeling and fibrosis. Despite their manyfold functions, cardiac fibroblasts remain poorly characterized in molecular terms. Evidence is evolving that cardiac fibroblasts are a heterogeneous population and likely derive from various distinct tissue niches in health and disease. Here, we review our emerging understanding of where cardiac fibroblasts come from, as well as how we can possibly use this knowledge to develop novel therapies for cardiac fibrosis.
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Affiliation(s)
- Elisabeth M Zeisberg
- Division of Matrix Biology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
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175
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Kehat I, Davis J, Tiburcy M, Accornero F, Saba-El-Leil MK, Maillet M, York AJ, Lorenz JN, Zimmermann WH, Meloche S, Molkentin JD. Extracellular signal-regulated kinases 1 and 2 regulate the balance between eccentric and concentric cardiac growth. Circ Res 2010; 108:176-83. [PMID: 21127295 DOI: 10.1161/circresaha.110.231514] [Citation(s) in RCA: 192] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
RATIONALE An increase in cardiac afterload typically produces concentric hypertrophy characterized by an increase in cardiomyocyte width, whereas volume overload or exercise results in eccentric growth characterized by cellular elongation and addition of sarcomeres in series. The signaling pathways that control eccentric versus concentric heart growth are not well understood. OBJECTIVE To determine the role of extracellular signal-regulated kinase 1 and 2 (ERK1/2) in regulating the cardiac hypertrophic response. METHODS AND RESULTS Here, we used mice lacking all ERK1/2 protein in the heart (Erk1(-/-) Erk2(fl/fl-Cre)) and mice expressing activated mitogen-activated protein kinase kinase (Mek)1 in the heart to induce ERK1/2 signaling, as well as mechanistic experiments in cultured myocytes to assess cellular growth characteristics associated with this signaling pathway. Although genetic deletion of all ERK1/2 from the mouse heart did not block the cardiac hypertrophic response per se, meaning that the heart still increased in weight with both aging and pathological stress stimulation, it did dramatically alter how the heart grew. For example, adult myocytes from hearts of Erk1(-/-) Erk2(fl/fl-Cre) mice showed preferential eccentric growth (lengthening), whereas myocytes from Mek1 transgenic hearts showed concentric growth (width increase). Isolated adult myocytes acutely inhibited for ERK1/2 signaling by adenoviral gene transfer showed spontaneous lengthening, whereas infection with an activated Mek1 adenovirus promoted constitutive ERK1/2 signaling and increased myocyte thickness. A similar effect was observed in engineered heart tissue under cyclic stretching, where ERK1/2 inhibition led to preferential lengthening. CONCLUSIONS Taken together, these data demonstrate that the ERK1/2 signaling pathway uniquely regulates the balance between eccentric and concentric growth of the heart.
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Affiliation(s)
- Izhak Kehat
- Department of Pediatrics, Division of Molecular Cardiovascular Biology, and Howard Hughes Medical Institute, Cincinnati Children's Hospital Medical Center, 240 Albert Sabin Way, Cincinnati, OH 45229-3039, USA
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176
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Hidaka K, Nitta T, Sugawa R, Shirai M, Schwartz RJ, Amagai T, Nitta S, Takahama Y, Morisaki T. Differentiation of Pharyngeal Endoderm from Mouse Embryonic Stem Cell. Stem Cells Dev 2010; 19:1735-43. [DOI: 10.1089/scd.2009.0466] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- Kyoko Hidaka
- Department of Bioscience, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Takeshi Nitta
- Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
| | - Ryo Sugawa
- Department of Molecular Pathophysiology, Osaka University Graduate School of Pharmaceutical Sciences, Suita, Osaka, Japan
| | - Manabu Shirai
- Department of Bioscience, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
| | - Robert J. Schwartz
- Section of Cardiovascular Sciences, Center for Cardiovascular Development, Baylor College of Medicine, Houston, Texas
| | - Takashi Amagai
- Department of Immunology and Microbiology, Meiji University of Integrative Medicine, Kyoto, Japan
| | - Sachiko Nitta
- Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
| | - Yousuke Takahama
- Division of Experimental Immunology, Institute for Genome Research, University of Tokushima, Tokushima, Japan
| | - Takayuki Morisaki
- Department of Bioscience, National Cardiovascular Center Research Institute, Suita, Osaka, Japan
- Department of Molecular Pathophysiology, Osaka University Graduate School of Pharmaceutical Sciences, Suita, Osaka, Japan
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177
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Zhang Y, Li S, Yuan L, Tian Y, Weidenfeld J, Yang J, Liu F, Chokas AL, Morrisey EE. Foxp1 coordinates cardiomyocyte proliferation through both cell-autonomous and nonautonomous mechanisms. Genes Dev 2010; 24:1746-57. [PMID: 20713518 DOI: 10.1101/gad.1929210] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cardiomyocyte proliferation is high in early development and decreases progressively with gestation, resulting in the lack of a robust cardiomyocyte proliferative response in the adult heart after injury. Little is understood about how both cell-autonomous and nonautonomous signals are integrated to regulate the balance of cardiomyocyte proliferation during development. In this study, we show that a single transcription factor, Foxp1, can control the balance of cardiomyocyte proliferation during development by targeting different pathways in the endocardium and myocardium. Endocardial loss of Foxp1 results in decreased Fgf3/Fgf16/Fgf17/Fgf20 expression in the heart, leading to reduced cardiomyocyte proliferation. This loss of myocardial proliferation can be rescued by exogenous Fgf20, and is mediated, in part, by Foxp1 repression of Sox17. In contrast, myocardial-specific loss of Foxp1 results in increased cardiomyocyte proliferation and decreased differentiation, leading to increased myocardial mass and neonatal demise. We show that Nkx2.5 is a direct target of Foxp1 repression, and Nkx2.5 expression is increased in Foxp1-deficient myocardium. Moreover, transgenic overexpression of Nkx2.5 leads to increased cardiomyocyte proliferation and increased ventricular mass, similar to the myocardial-specific loss of Foxp1. These data show that Foxp1 coordinates the balance of cardiomyocyte proliferation and differentiation through cell lineage-specific regulation of Fgf ligand and Nkx2.5 expression.
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Affiliation(s)
- Yuzhen Zhang
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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178
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González-Rosa JM, Padrón-Barthe L, Torres M, Mercader N. [Lineage tracing of epicardial cells during development and regeneration]. Rev Esp Cardiol 2010; 63 Suppl 2:36-48. [PMID: 20540899 DOI: 10.1016/s0300-8932(10)70151-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Tracing the history of individual cells during embryonic morphogenesis in a structure as complex as the cardiovascular system is one of the major challenges of developmental biology. It involves determining the relationships between the various lineages of cells forming an organ at different stages, describing the topological rearrangements tissues undergo during morphogenesis, and characterizing the interactions between cells in different structures. However, despite the great expectations raised in the field of regenerative medicine, only limited progress has been made in using regenerative therapy to repair the cardiovascular system. Recent research has highlighted the role of the epicardium during cardiac regeneration, but it is still unclear whether it is important for molecular signaling or acts as a source of progenitor cells during this process. Consequently, increasing knowledge about the origin, diversification and potential of epicardial cells during development and homeostasis and under pathological conditions is of fundamental importance both for basic research and for the development of effective cellular therapies. The aims of this article were to provide a general overview of the classical techniques used for tracing cell lineages, including their potential and limitations, and to describe novel techniques for studying the origin and differentiation of the epicardium and its role in cardiac regeneration.
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Affiliation(s)
- Juan Manuel González-Rosa
- Departamento de Biología del Desarrollo Cardiovascular, Centro Nacional de Investigaciones Cardiovasculares, Instituto de Salud Carlos III, Madrid, España
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179
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Wu B, Zhou B, Wang Y, Cheng HL, Hang CT, Pu WT, Chang CP, Zhou B. Inducible cardiomyocyte-specific gene disruption directed by the rat Tnnt2 promoter in the mouse. Genesis 2010; 48:63-72. [PMID: 20014345 DOI: 10.1002/dvg.20573] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We developed a conditional and inducible gene knockout methodology that allows effective gene deletion in mouse cardiomyocytes. This transgenic mouse line was generated by coinjection of two transgenes, a "reverse" tetracycline-controlled transactivator (rtTA) directed by a rat cardiac troponin T (Tnnt2) promoter and a Cre recombinase driven by a tetracycline-responsive promoter (TetO). Here, Tnnt2-rtTA activated TetO-Cre expression takes place in cardiomyocytes following doxycycline treatment. Using two different mouse Cre reporter lines, we demonstrated that expression of Cre recombinase was specifically and robustly induced in the cardiomyocytes of embryonic or adult hearts following doxycycline induction, thus, allowing cardiomyocyte-specific gene disruption and lineage tracing. We also showed that rtTA expression and doxycycline treatment did not compromise cardiac function. These features make the Tnnt2-rtTA;TetO-Cre transgenic line a valuable genetic tool for analysis of spatiotemporal gene function and cardiomyocyte lineage tracing during developmental and postnatal periods.
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Affiliation(s)
- Bingruo Wu
- Department of Genetics, Albert Einstein College of Medicine of Yeshiva University, Price Center 420, 1301 Morris Park Avenue, Bronx, NY 10461, USA
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180
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Tian Y, Yuan L, Goss AM, Wang T, Yang J, Lepore JJ, Zhou D, Schwartz RJ, Patel V, Cohen ED, Morrisey EE. Characterization and in vivo pharmacological rescue of a Wnt2-Gata6 pathway required for cardiac inflow tract development. Dev Cell 2010; 18:275-87. [PMID: 20159597 DOI: 10.1016/j.devcel.2010.01.008] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 12/10/2009] [Accepted: 01/11/2010] [Indexed: 12/17/2022]
Abstract
Little is understood about the molecular mechanisms underlying the morphogenesis of the posterior pole of the heart. Here we show that Wnt2 is expressed specifically in the developing inflow tract mesoderm, which generates portions of the atria and atrio-ventricular canal. Loss of Wnt2 results in defective development of the posterior pole of the heart, resulting in a phenotype resembling the human congenital heart syndrome complete common atrio-ventricular canal. The number and proliferation of posterior second heart field progenitors is reduced in Wnt2(-/-) mutants. Moreover, these defects can be rescued in a temporally restricted manner through pharmacological inhibition of Gsk-3beta. We also show that Wnt2 works in a feedforward transcriptional loop with Gata6 to regulate posterior cardiac development. These data reveal a molecular pathway regulating the posterior cardiac mesoderm and demonstrate that cardiovascular defects caused by loss of Wnt signaling can be rescued pharmacologically in vivo.
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Affiliation(s)
- Ying Tian
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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181
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Heineke J, Auger-Messier M, Xu J, Sargent M, York A, Welle S, Molkentin JD. Genetic deletion of myostatin from the heart prevents skeletal muscle atrophy in heart failure. Circulation 2010; 121:419-25. [PMID: 20065166 DOI: 10.1161/circulationaha.109.882068] [Citation(s) in RCA: 184] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Cardiac cachexia is characterized by an exaggerated loss of skeletal muscle, weakness, and exercise intolerance, although the cause of these effects remains unknown. Here, we hypothesized that the heart functions as an endocrine organ in promoting systemic cachexia by secreting peptide factors such as myostatin. Myostatin is a cytokine of the transforming growth factor-beta superfamily that is known to control muscle wasting. METHODS AND RESULTS We used a Cre/loxP system to ablate myostatin (Mstn gene) expression in a cell type-specific manner. As expected, elimination of Mstn selectively in skeletal muscle with a myosin light chain 1f (MLC1f)-cre allele induced robust hypertrophy in all skeletal muscle. However, heart-specific deletion of Mstn with an Nkx2.5-cre allele did not alter baseline heart size or secondarily affect skeletal muscle size, but the characteristic wasting and atrophy of skeletal muscle that typify heart failure were not observed in these heart-specific null mice, indicating that myocardial myostatin expression controls muscle atrophy in heart failure. Indeed, myostatin levels in the plasma were significantly increased in wild-type mice subjected to pressure overload-induced cardiac hypertrophy but not in Mstn heart-specific deleted mice. Moreover, cardiac-specific overexpression of myostatin, which increased circulating levels of myostatin by 3- to 4-fold, caused a reduction in weight of the quadriceps, gastrocnemius, soleus, and even the heart itself. Finally, to investigate myostatin as a potential therapeutic target for the treatment of muscle wasting in heart failure, we infused a myostatin blocking antibody (JA-16), which promoted greater maintenance of muscle mass in heart failure. CONCLUSIONS Myostatin released from cardiomyocytes induces skeletal muscle wasting in heart failure. Targeted inhibition of myostatin in cardiac cachexia might be a therapeutic option in the future.
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Affiliation(s)
- Joerg Heineke
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, USA
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182
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Chintalgattu V, Ai D, Langley RR, Zhang J, Bankson JA, Shih TL, Reddy AK, Coombes KR, Daher IN, Pati S, Patel SS, Pocius JS, Taffet GE, Buja LM, Entman ML, Khakoo AY. Cardiomyocyte PDGFR-beta signaling is an essential component of the mouse cardiac response to load-induced stress. J Clin Invest 2010; 120:472-84. [PMID: 20071776 DOI: 10.1172/jci39434] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Accepted: 11/18/2009] [Indexed: 01/07/2023] Open
Abstract
PDGFR is an important target for novel anticancer therapeutics because it is overexpressed in a wide variety of malignancies. Recently, however, several anticancer drugs that inhibit PDGFR signaling have been associated with clinical heart failure. Understanding this effect of PDGFR inhibitors has been difficult because the role of PDGFR signaling in the heart remains largely unexplored. As described herein, we have found that PDGFR-beta expression and activation increase dramatically in the hearts of mice exposed to load-induced cardiac stress. In mice in which Pdgfrb was knocked out in the heart in development or in adulthood, exposure to load-induced stress resulted in cardiac dysfunction and heart failure. Mechanistically, we showed that cardiomyocyte PDGFR-beta signaling plays a vital role in stress-induced cardiac angiogenesis. Specifically, we demonstrated that cardiomyocyte PDGFR-beta was an essential upstream regulator of the stress-induced paracrine angiogenic capacity (the angiogenic potential) of cardiomyocytes. These results demonstrate that cardiomyocyte PDGFR-beta is a regulator of the compensatory cardiac response to pressure overload-induced stress. Furthermore, our findings may provide insights into the mechanism of cardiotoxicity due to anticancer PDGFR inhibitors.
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Affiliation(s)
- Vishnu Chintalgattu
- Department of Cardiology, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA
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183
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Saxena A, Tabin CJ. miRNA-processing enzyme Dicer is necessary for cardiac outflow tract alignment and chamber septation. Proc Natl Acad Sci U S A 2010; 107:87-91. [PMID: 20018673 PMCID: PMC2806718 DOI: 10.1073/pnas.0912870107] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
MicroRNAs (miRNAs) have previously been implicated in a number of developmental processes, including development of the ventricular myocardium of the heart. To determine what, if any, additional roles miRNAs play in cardiogenesis, we deleted the miRNA-processing enzyme Dicer specifically in the developing murine heart. Embryos lacking cardiac Dicer lived longer than reported in previous studies using different alleles to remove cardiac Dicer activity and displayed a highly penetrant phenotype of double outlet right ventricle with a concurrent ventricular septal defect. Before the defect's onset, Pitx2c and Sema3c, both required for outflow tract morphogenesis, were up-regulated in Dicer-deficient hearts. Interestingly, mesenchymal apoptosis in the outflow tract normally required for outflow tract alignment was greatly decreased in the mutants, likely contributing directly to the observed phenotype. In sum, we demonstrate here a specific developmental process, that of outflow tract morphogenesis, being hindered by the deletion of miRNAs during cardiogenesis.
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Affiliation(s)
- Ankur Saxena
- Department of Genetics, Harvard Medical School, Boston, MA 02115; and
- Division of Biology, California Institute of Technology, Pasadena, CA 91125
| | - Clifford J. Tabin
- Department of Genetics, Harvard Medical School, Boston, MA 02115; and
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184
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Abstract
The endocardium, the endothelial lining of the heart, plays complex and critical roles in heart development, particularly in the formation of the cardiac valves and septa, the division of the truncus arteriosus into the aortic and pulmonary trunks, the development of Purkinje fibers that form the cardiac conduction system, and the formation of trabecular myocardium. Current data suggest that the endocardium is a regionally specialized endothelium that arises through a process of de novo vasculogenesis from a distinct population of mesodermal cardiogenic precursors in the cardiac crescent. In this article, we review recent developments in the understanding of the embryonic origins of the endocardium. Specifically, we summarize vasculogenesis and specification of endothelial cells from mesodermal precursors, and we review the transcriptional pathways involved in these processes. We discuss the lineage relationships between the endocardium and other endothelial populations and between the endocardium and the myocardium. Finally, we explore unresolved questions about the lineage relationships between the endocardium and the myocardium. One of the central questions involves the timing with which mesodermal cells, which arise in the primitive streak and migrate to the cardiac crescent, become committed to an endocardial fate. Two competing conceptual models of endocardial specification have been proposed. In the first, mesodermal precursor cells in the cardiac crescent are prespecified to become either endocardial or myocardial cells, while in the second, fate plasticity is retained by bipotential cardiogenic cells in the cardiac crescent. We propose a third model that reconciles these two views and suggest future experiments that might resolve this question.
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Affiliation(s)
- Ian S. Harris
- Cardiovascular Research Institute, University of California, San Francisco, 600 16th Street, Mail Code 2240, San Francisco, CA 94158-2517 USA
| | - Brian L. Black
- Cardiovascular Research Institute, University of California, San Francisco, 600 16th Street, Mail Code 2240, San Francisco, CA 94158-2517 USA
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185
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Abstract
The transcriptional regulation of cardiovascular development requires precise spatiotemporal control of gene expression, and heterozygous mutations of transcription factors have frequently been implicated in human cardiovascular malformations. A novel mechanism involving post-transcriptional regulation by small, noncoding microRNAs (miRNAs) has emerged as a central regulator of many cardiogenic processes. We are beginning to understand the functions that miRNAs play during essential biologic processes, such as cell proliferation, differentiation, apoptosis, stress response, and tumorigenesis. The identification of miRNAs expressed in specific cardiac and vascular cell types has led to the discovery of important regulatory roles for these small RNAs during cardiomyocyte differentiation, cell cycle, conduction, and vessel formation. Here, we overview the recent findings on miRNA regulation in cardiovascular development. Further analysis of miRNA function during cardiovascular development will allow us to determine the potential for novel miRNA-based therapeutic strategies.
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Affiliation(s)
- Kimberly R. Cordes
- Gladstone Institute of Cardiovascular Disease and Departments of Pediatrics and Biochemistry and Biophysics, University of California, San Francisco, CA 94158 USA
| | - Deepak Srivastava
- Gladstone Institute of Cardiovascular Disease and Departments of Pediatrics and Biochemistry and Biophysics, University of California, San Francisco, CA 94158 USA
| | - Kathryn N. Ivey
- Gladstone Institute of Cardiovascular Disease and Departments of Pediatrics and Biochemistry and Biophysics, University of California, San Francisco, CA 94158 USA
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186
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Kokubo N, Matsuura M, Onimaru K, Tiecke E, Kuraku S, Kuratani S, Tanaka M. Mechanisms of heart development in the Japanese lamprey,Lethenteron japonicum. Evol Dev 2010; 12:34-44. [DOI: 10.1111/j.1525-142x.2009.00389.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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187
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Maillet M, Davis J, Auger-Messier M, York A, Osinska H, Piquereau J, Lorenz JN, Robbins J, Ventura-Clapier R, Molkentin JD. Heart-specific deletion of CnB1 reveals multiple mechanisms whereby calcineurin regulates cardiac growth and function. J Biol Chem 2009; 285:6716-24. [PMID: 20037164 PMCID: PMC2825466 DOI: 10.1074/jbc.m109.056143] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Calcineurin is a protein phosphatase that is uniquely regulated by sustained increases in intracellular Ca2+ following signal transduction events. Calcineurin controls cellular proliferation, differentiation, apoptosis, and inducible gene expression following stress and neuroendocrine stimulation. In the adult heart, calcineurin regulates hypertrophic growth of cardiomyocytes in response to pathologic insults that are associated with altered Ca2+ handling. Here we determined that calcineurin signaling is directly linked to the proper control of cardiac contractility, rhythm, and the expression of Ca2+-handling genes in the heart. Our approach involved a cardiomyocyte-specific deletion using a CnB1-LoxP-targeted allele in mice and three different cardiac-expressing Cre alleles/transgenes. Deletion of calcineurin with the Nkx2.5-Cre knock-in allele resulted in lethality at 1 day after birth due to altered right ventricular morphogenesis, reduced ventricular trabeculation, septal defects, and valvular overgrowth. Slightly later deletion of calcineurin with the α-myosin heavy chain Cre transgene resulted in lethality in early mid adulthood that was characterized by substantial reductions in cardiac contractility, severe arrhythmia, and reduced myocyte content in the heart. Young calcineurin heart-deleted mice died suddenly after pressure overload stimulation or neuroendocrine agonist infusion, and telemetric monitoring of older mice showed arrhythmia leading to sudden death. Mechanistically, loss of calcineurin reduced expression of key Ca2+-handling genes that likely lead to arrhythmia and reduced contractility. Loss of calcineurin also directly impacted cellular proliferation in the postnatal developing heart. These results reveal multiple mechanisms whereby calcineurin regulates cardiac development and myocyte contractility.
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Affiliation(s)
- Marjorie Maillet
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, Ohio 45229-3039, USA
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188
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Kratsios P, Catela C, Salimova E, Huth M, Berno V, Rosenthal N, Mourkioti F. Distinct roles for cell-autonomous Notch signaling in cardiomyocytes of the embryonic and adult heart. Circ Res 2009; 106:559-72. [PMID: 20007915 DOI: 10.1161/circresaha.109.203034] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE The Notch signaling pathway is important for cell-cell communication that controls tissue formation and homeostasis during embryonic and adult life, but the precise cell targets of Notch signaling in the mammalian heart remain poorly defined. OBJECTIVE To investigate the functional role of Notch signaling in the cardiomyocyte compartment of the embryonic and adult heart. METHODS AND RESULTS Here, we report that either conditional overexpression of Notch1 intracellular domain (NICD1) or selective silencing of Notch signaling in the embryonic cardiomyocyte compartment results in developmental defects and perinatal lethality. In contrast, augmentation of endogenous Notch reactivation after myocardial infarction in the adult, either by inducing cardiomyocyte-specific Notch1 transgene expression or by intramyocardial delivery of a Notch1 pseudoligand, increases survival rate, improves cardiac functional performance, and minimizes fibrosis, promoting antiapoptotic and angiogenic mechanisms. CONCLUSIONS These results reveal a strict requirement for cell-autonomous modulation of Notch signaling during heart morphogenesis, and illustrate how the same signaling pathway that promotes congenital heart defects when perturbed in the embryo can be therapeutically redeployed for the treatment of adult myocardial damage.
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Affiliation(s)
- Paschalis Kratsios
- Mouse Biology Unit, European Molecular Biology Laboratory, Campus A. Buzzati-Traverso, Rome, Italy
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189
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Muñoz-Chápuli R, Pérez-Pomares JM. Cardiogenesis: an embryological perspective. J Cardiovasc Transl Res 2009; 3:37-48. [PMID: 20560033 DOI: 10.1007/s12265-009-9146-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Accepted: 10/19/2009] [Indexed: 12/12/2022]
Abstract
Cardiogenesis, considered as the formation of new heart tissue from embryonic, postnatal, or adult cardiac progenitors, is a pivotal concept to understand the rationale of advanced therapies to repair the damaged heart. In this review, we focus on the cellular and molecular regulation of cardiogenesis in the developing embryo, and we dissect the complex interactions that control the diversification and maturation of a variety of cardiac cell lineages. Our aim is to show how the sophisticated anatomical structure of the adult four-chambered heart strongly depends on the fine regulation of the differentiation of cardiac progenitor cells. These events are shown to be progressive and dynamic as well as plastic, so that the patterned differentiation of distinct heart domains is highly dependent on signals provided by nonmyocardial heart components and extracardiac tissues. Finally, we present the core of our knowledge on cardiac embryogenesis in a biomedical context to provide a critical analysis on the logic of cell therapies designed to treat the failing heart.
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Affiliation(s)
- Ramón Muñoz-Chápuli
- Department of Animal Biology, Faculty of Science, University of Málaga, 29071 Málaga, Spain
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190
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Nagel S, Venturini L, Przybylski GK, Grabarczyk P, Meyer C, Kaufmann M, Battmer K, Schmidt CA, Drexler HG, Scherr M, Macleod RA. NK-like homeodomain proteins activate NOTCH3-signaling in leukemic T-cells. BMC Cancer 2009; 9:371. [PMID: 19835636 PMCID: PMC2770077 DOI: 10.1186/1471-2407-9-371] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Accepted: 10/19/2009] [Indexed: 11/16/2022] Open
Abstract
Background Homeodomain proteins control fundamental cellular processes in development and in cancer if deregulated. Three members of the NK-like subfamily of homeobox genes (NKLs), TLX1, TLX3 and NKX2-5, are implicated in T-cell acute lymphoblastic leukemia (T-ALL). They are activated by particular chromosomal aberrations. However, their precise function in leukemogenesis is still unclear. Here we screened further NKLs in 24 T-ALL cell lines and identified the common expression of MSX2. The subsequent aim of this study was to analyze the role of MSX2 in T-cell differentiation which may be disturbed by oncogenic NKLs. Methods Specific gene activity was examined by quantitative real-time PCR, and globally by expression profiling. Proteins were analyzed by western blot, immuno-cytology and immuno-precipitation. For overexpression studies cell lines were transduced by lentiviruses. Results Quantification of MSX2 mRNA in primary hematopoietic cells demonstrated higher levels in CD34+ stem cells as compared to peripheral blood cells and mature CD3+ T-cells. Furthermore, analysis of MSX2 expression levels in T-cell lines after treatment with core thymic factors confirmed their involvement in regulation. These results indicated that MSX2 represents an hematopoietic NKL family member which is downregulated during T-cell development and may functionally substituted by oncogenic NKLs. For functional analysis JURKAT cells were lentivirally transduced, overexpressing either MSX2 or oncogenic TLX1 and NKX2-5, respectively. These cells displayed transcriptional activation of NOTCH3-signaling, including NOTCH3 and HEY1 as analyzed by gene expression profiling and quantitative RT-PCR, and consistently attenuated sensitivity to gamma-secretase inhibitor as analyzed by MTT-assays. Furthermore, in addition to MSX2, both TLX1 and NKX2-5 proteins interacted with NOTCH-pathway repressors, SPEN/MINT/SHARP and TLE1/GRG1, representing a potential mechanism for (de)regulation. Finally, elevated expression of NOTCH3 and HEY1 was detected in primary TLX1/3 positive T-ALL cells corresponding to the cell line data. Conclusion Identification and analysis of MSX2 in hematopoietic cells implicates a modulatory role via NOTCH3-signaling in early T-cell differentiation. Our data suggest that reduction of NOTCH3-signaling by physiological downregulation of MSX2 expression during T-cell development is abrogated by ectopic expression of oncogenic NKLs, substituting MSX2 function.
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Affiliation(s)
- Stefan Nagel
- Dept. of Human and Animal Cell Lines, DSMZ - German Collection of Microorganisms and Cell Cultures, Inhoffenstr, 7B, 38124 Braunschweig, Germany.
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191
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Zhou B, Ma Q, Kong SW, Hu Y, Campbell PH, McGowan FX, Ackerman KG, Wu B, Zhou B, Tevosian SG, Pu WT. Fog2 is critical for cardiac function and maintenance of coronary vasculature in the adult mouse heart. J Clin Invest 2009; 119:1462-76. [PMID: 19411759 DOI: 10.1172/jci38723] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Accepted: 03/11/2009] [Indexed: 12/27/2022] Open
Abstract
Aberrant transcriptional regulation contributes to the pathogenesis of both congenital and adult forms of heart disease. While the transcriptional regulator friend of Gata 2 (FOG2) is known to be essential for heart morphogenesis and coronary development, its tissue-specific function has not been previously investigated. Additionally, little is known about the role of FOG2 in the adult heart. Here we used spatiotemporally regulated inactivation of Fog2 to delineate its function in both the embryonic and adult mouse heart. Early cardiomyocyte- restricted loss of Fog2 recapitulated the cardiac and coronary defects of the Fog2 germline murine knockouts. Later cardiomyocyte-restricted loss of Fog2 (Fog2MC) did not result in defects in cardiac structure or coronary vessel formation. However, Fog2MC adult mice had severely depressed ventricular function and died at 8-14 weeks. Fog2MC adult hearts displayed a paucity of coronary vessels, associated with myocardial hypoxia, increased cardiomyocyte apoptosis, and cardiac fibrosis. Induced inactivation of Fog2 in the adult mouse heart resulted in similar phenotypes, as did ablation of the FOG2 interaction with the transcription factor GATA4. Loss of the FOG2 or FOG2-GATA4 interaction altered the expression of a panel of angiogenesis-related genes. Collectively, our data indicate that FOG2 regulates adult heart function and coronary angiogenesis.
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Affiliation(s)
- Bin Zhou
- Department of Cardiology, Children's Hospital Boston and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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192
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Harel I, Nathan E, Tirosh-Finkel L, Zigdon H, Guimarães-Camboa N, Evans SM, Tzahor E. Distinct origins and genetic programs of head muscle satellite cells. Dev Cell 2009; 16:822-32. [PMID: 19531353 DOI: 10.1016/j.devcel.2009.05.007] [Citation(s) in RCA: 175] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2008] [Revised: 04/07/2009] [Accepted: 05/11/2009] [Indexed: 11/28/2022]
Abstract
Adult skeletal muscle possesses a remarkable regenerative capacity, due to the presence of satellite cells, adult muscle stem cells. We used fate-mapping techniques in avian and mouse models to show that trunk (Pax3(+)) and cranial (MesP1(+)) skeletal muscle and satellite cells derive from separate genetic lineages. Similar lineage heterogeneity is seen within the head musculature and satellite cells, due to their shared, heterogenic embryonic origins. Lineage tracing experiments with Isl1Cre mice demonstrated the robust contribution of Isl1(+) cells to distinct jaw muscle-derived satellite cells. Transplantation of myofiber-associated, Isl1-derived satellite cells into damaged limb muscle contributed to muscle regeneration. In vitro experiments demonstrated the cardiogenic nature of cranial- but not trunk-derived satellite cells. Finally, overexpression of Isl1 in the branchiomeric muscles of chick embryos inhibited skeletal muscle differentiation in vitro and in vivo, suggesting that this gene plays a role in the specification of cardiovascular and skeletal muscle stem cell progenitors.
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Affiliation(s)
- Itamar Harel
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel
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193
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Nimura K, Ura K, Shiratori H, Ikawa M, Okabe M, Schwartz RJ, Kaneda Y. A histone H3 lysine 36 trimethyltransferase links Nkx2-5 to Wolf-Hirschhorn syndrome. Nature 2009; 460:287-91. [PMID: 19483677 DOI: 10.1038/nature08086] [Citation(s) in RCA: 294] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2008] [Accepted: 04/23/2009] [Indexed: 01/15/2023]
Abstract
Diverse histone modifications are catalysed and recognized by various specific proteins, establishing unique modification patterns that act as transcription signals. In particular, histone H3 trimethylation at lysine 36 (H3K36me3) is associated with actively transcribed regions and has been proposed to provide landmarks for continuing transcription; however, the control mechanisms and functions of H3K36me3 in higher eukaryotes are unknown. Here we show that the H3K36me3-specific histone methyltransferase (HMTase) Wolf-Hirschhorn syndrome candidate 1 (WHSC1, also known as NSD2 or MMSET) functions in transcriptional regulation together with developmental transcription factors whose defects overlap with the human disease Wolf-Hirschhorn syndrome (WHS). We found that mouse Whsc1, one of five putative Set2 homologues, governed H3K36me3 along euchromatin by associating with the cell-type-specific transcription factors Sall1, Sall4 and Nanog in embryonic stem cells, and Nkx2-5 in embryonic hearts, regulating the expression of their target genes. Whsc1-deficient mice showed growth retardation and various WHS-like midline defects, including congenital cardiovascular anomalies. The effects of Whsc1 haploinsufficiency were increased in Nkx2-5 heterozygous mutant hearts, indicating their functional link. We propose that WHSC1 functions together with developmental transcription factors to prevent the inappropriate transcription that can lead to various pathophysiologies.
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Affiliation(s)
- Keisuke Nimura
- Division of Gene Therapy Science, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan
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194
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Que J, Luo X, Schwartz RJ, Hogan BLM. Multiple roles for Sox2 in the developing and adult mouse trachea. Development 2009; 136:1899-907. [PMID: 19403656 DOI: 10.1242/dev.034629] [Citation(s) in RCA: 228] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The esophagus, trachea and lung develop from the embryonic foregut, yet acquire and maintain distinct tissue phenotypes. Previously, we demonstrated that the transcription factor Sox2 is necessary for foregut morphogenesis and esophagus development. We show that Sox2 is also required for the normal development of the trachea and lung. In both the embryo and adult, Sox2 is exclusively expressed in the epithelium of the trachea and airways. We use an Nkx2.5-Cre transgene and a Sox2 floxed allele to conditionally delete Sox2 in the ventral epithelial domain of the early anterior foregut, which gives rise to the future trachea and lung buds. All conditional mutants die of respiratory distress at birth, probably due to abnormal differentiation of the laryngeal and tracheal cartilage as a result of defective epithelial-mesenchymal interaction. About 60% of the mutants have a short trachea, suggesting that the primary budding site of the lung shifts anteriorly. In the tracheal epithelium of all conditional mutants there are significantly more mucus-producing cells compared with wild type, and fewer basal stem cells, ciliated and Clara cells. Differentiation of the epithelium lining the conducting airways in the lung is abnormal, suggesting that Sox2 also plays a role in the differentiation of embryonic airway progenitors into specific lineages. Conditional deletion of Sox2 was then used to test its role in adult epithelium maintenance. We found that epithelial cells, including basal stem cells, lacking Sox2 show a reduced capacity to proliferate in culture and to repair after injury in vivo. Taken together, these results define multiple roles for Sox2 in the developing and adult trachea.
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Affiliation(s)
- Jianwen Que
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
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195
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DiMichele LA, Hakim ZS, Sayers RL, Rojas M, Schwartz RJ, Mack CP, Taylor JM. Transient expression of FRNK reveals stage-specific requirement for focal adhesion kinase activity in cardiac growth. Circ Res 2009; 104:1201-8. [PMID: 19372463 DOI: 10.1161/circresaha.109.195941] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Focal adhesion kinase (FAK) is strongly activated by integrins and growth factors and is essential for embryonic development. We previously showed that the C terminus of FAK is expressed as a separate protein termed FAK-related nonkinase (FRNK) in a smooth muscle cell-selective fashion and that FRNK functions to buffer FAK-dependent signals. We now show that FRNK is also transiently expressed in the neonatal myocardium, with peak levels occurring 5 to 7 days postnatal, just before cell cycle withdrawal. Using novel mouse models, we demonstrate that cardiac-selective expression of FRNK (leading to inhibition of FAK) starting at embryonic day 10.5 leads to a severe ventricular noncompaction defect associated with reduced cardiomyocyte proliferation. Remarkably, postnatal expression of nearly identical levels of FRNK is well tolerated and does not affect viability or anabolic cardiac growth. Nonetheless, FRNK expression in the adult heart does attenuate pathological cardiac hypertrophy following aortic banding, confirming and extending our previous data that this compensatory response is blunted in FAK null hearts. Our mechanistic studies in cultured neonatal cardiomyocytes reveal that FRNK expression induces p38/p27(kip)-dependent cell cycle withdrawal and attenuates extracellular signal-regulated kinase-dependent hypertrophic growth. These findings indicate that dynamic expression of FRNK in the neonatal heart may function to promote cardiomyocyte quiescence in an environment that is particularly rich in growth factors and growth promoting extracellular matrices.
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Affiliation(s)
- Laura A DiMichele
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
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196
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Hoffmann AD, Peterson MA, Friedland-Little JM, Anderson SA, Moskowitz IP. sonic hedgehog is required in pulmonary endoderm for atrial septation. Development 2009; 136:1761-70. [PMID: 19369393 DOI: 10.1242/dev.034157] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The genesis of the septal structures of the mammalian heart is central to understanding the ontogeny of congenital heart disease and the evolution of cardiac organogenesis. We found that Hedgehog (Hh) signaling marked a subset of cardiac progenitors specific to the atrial septum and the pulmonary trunk in the mouse. Using genetic inducible fate mapping with Gli1(CreERT2), we marked Hh-receiving progenitors in anterior and posterior second heart field splanchnic mesoderm between E8 and E10. In the inflow tract, Hh-receiving progenitors migrated from the posterior second heart field through the dorsal mesocardium to form the atrial septum, including both the primary atrial septum and dorsal mesenchymal protrusion (DMP). In the outflow tract, Hh-receiving progenitors migrated from the anterior second heart field to populate the pulmonary trunk. Abrogation of Hh signaling during atrial septal progenitor specification resulted in atrial and atrioventricular septal defects and hypoplasia of the developing DMP. Hedgehog signaling appeared necessary and sufficient for atrial septal progenitor fate: Hh-receiving cells rendered unresponsive to the Hh ligand migrated into the atrium in normal numbers but populated the atrial free wall rather than the atrial septum. Conversely, constitutive activation of Hh signaling caused inappropriate enlargement of the atrial septum. The close proximity of posterior second heart field cardiac progenitors to pulmonary endoderm suggested a pulmonary source for the Hh ligand. We found that Shh is required in the pulmonary endoderm for atrial septation. Therefore, Hh signaling from distinct pulmonary and pharyngeal endoderm is required for inflow and outflow septation, respectively. These data suggest a model in which respiratory endoderm patterns the morphogenesis of cardiac structural components required for efficient cardiopulmonary circulation.
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Affiliation(s)
- Andrew D Hoffmann
- Departments of Pediatrics and Pathology, University of Chicago, Chicago, IL 60637, USA
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197
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Abstract
The transcriptional regulation of cardiovascular development requires precise spatiotemporal control of gene expression, and heterozygous mutations of transcription factors have frequently been implicated in human cardiovascular malformations. A novel mechanism involving posttranscriptional regulation by small, noncoding microRNAs (miRNAs) has emerged as a central regulator of many cardiogenic processes. We are beginning to understand the functions that miRNAs play during essential biological processes, such as cell proliferation, differentiation, apoptosis, stress response, and tumorigenesis. The identification of miRNAs expressed in specific cardiac and vascular cell types has led to the discovery of important regulatory roles for these small RNAs during cardiomyocyte differentiation, cell cycle, conduction, vessel formation, and during stages of cardiac hypertrophy in the adult. Here, we overview the recent findings on miRNA regulation in cardiovascular development and report the latest advances in understanding their function by unveiling their mRNA targets. Further analysis of miRNA function during cardiovascular development will allow us to determine the potential for novel miRNA-based therapeutic strategies.
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Affiliation(s)
- Kimberly R Cordes
- Gladstone Institute of Cardiovascular Disease, 1650 Owens St, San Francisco, CA 94158, USA
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198
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Lombardi R, Dong J, Rodriguez G, Bell A, Leung TK, Schwartz RJ, Willerson JT, Brugada R, Marian AJ. Genetic fate mapping identifies second heart field progenitor cells as a source of adipocytes in arrhythmogenic right ventricular cardiomyopathy. Circ Res 2009; 104:1076-84. [PMID: 19359597 DOI: 10.1161/circresaha.109.196899] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The phenotypic hallmark of arrhythmogenic right ventricular cardiomyopathy, a genetic disease of desmosomal proteins, is fibroadipocytic replacement of the right ventricle. Cellular origin of excess adipocytes, the responsible mechanism(s) and the basis for predominant involvement of the right ventricle are unknown. We generated 3 sets of lineage tracer mice regulated by cardiac lineage promoters alpha-myosin heavy chain (alphaMyHC), Nkx2.5, or Mef2C. We conditionally expressed the reporter enhanced yellow fluorescent protein while concomitantly deleting the desmosomal protein desmoplakin in cardiac myocyte lineages using the Cre-LoxP technique. Lineage tracer mice showed excess fibroadiposis and increased numbers of adipocytes in the hearts. Few adipocytes in the hearts of alphaMyHC-regulated lineage tracer mice, but the majority of adipocytes in the hearts of Nkx2.5- and Mef2C-regulated lineage tracer mice, expressed enhanced yellow fluorescent protein. In addition, rare cells coexpressed adipogenic transcription factors and the second heart field markers Isl1 and Mef2C in the lineage tracer mouse hearts and in human myocardium from patients with arrhythmogenic right ventricular cardiomyopathy. To delineate the responsible mechanism, we generated transgenic mice expressing desmosomal protein plakoglobin in myocyte lineages. Transgene plakoglobin translocated to nucleus, detected by immunoblotting and immunofluorescence staining and coimmunoprecipitated with Tcf7l2, a canonical Wnt signaling transcription factor. Expression levels of canonical Wnt/Tcf7l2 targets bone morphogenetic protein 7 and Wnt5b, which promote adipogenesis, were increased and expression level of connective tissue growth factor, an inhibitor of adipogenesis, was decreased. We conclude adipocytes in arrhythmogenic right ventricular cardiomyopathy originate from the second heart field cardiac progenitors, which switch to an adipogenic fate because of suppressed canonical Wnt signaling by nuclear plakoglobin.
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Affiliation(s)
- Raffaella Lombardi
- Center for Cardiovascular Genetics, Brown Foundation Institute of Molecular Medicine, The University of Texas Health Sciences Center, 6770 Bertner Street, Houston, TX 77030, USA
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199
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Espinoza-Lewis RA, Yu L, He F, Liu H, Tang R, Shi J, Sun X, Martin JF, Wang D, Yang J, Chen Y. Shox2 is essential for the differentiation of cardiac pacemaker cells by repressing Nkx2-5. Dev Biol 2009; 327:376-85. [PMID: 19166829 DOI: 10.1016/j.ydbio.2008.12.028] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Revised: 12/12/2008] [Accepted: 12/16/2008] [Indexed: 10/21/2022]
Abstract
The pacemaker is composed of specialized cardiomyocytes located within the sinoatrial node (SAN), and is responsible for originating and regulating the heart beat. Recent advances towards understanding the SAN development have been made on the genetic control and gene interaction within this structure. Here we report that the Shox2 homeodomain transcription factor is restrictedly expressed in the sinus venosus region including the SAN and the sinus valves during embryonic heart development. Shox2 null mutation results in embryonic lethality due to cardiovascular defects, including an abnormal low heart beat rate (bradycardia) and severely hypoplastic SAN and sinus valves attributed to a significantly decreased level of cell proliferation. Genetically, the lack of Tbx3 and Hcn4 expression, along with ectopic activation of Nppa, Cx40, and Nkx2-5 in the Shox2(-/-) SAN region, indicates a failure in SAN differentiation. Furthermore, Shox2 overexpression in Xenopus embryos results in extensive repression of Nkx2-5 in the developing heart, leading to a reduced cardiac field and aberrant heart formation. Reporter gene expression assays provide additional evidence for the repression of Nkx2-5 promoter activity by Shox2. Taken together our results demonstrate that Shox2 plays an essential role in the SAN and pacemaker development by controlling a genetic cascade through the repression of Nkx2-5.
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200
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Risebro CA, Searles RG, Melville AAD, Ehler E, Jina N, Shah S, Pallas J, Hubank M, Dillard M, Harvey NL, Schwartz RJ, Chien KR, Oliver G, Riley PR. Prox1 maintains muscle structure and growth in the developing heart. Development 2008; 136:495-505. [PMID: 19091769 DOI: 10.1242/dev.030007] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Impaired cardiac muscle growth and aberrant myocyte arrangement underlie congenital heart disease and cardiomyopathy. We show that cardiac-specific inactivation of the murine homeobox transcription factor Prox1 results in the disruption of expression and localisation of sarcomeric proteins, gross myofibril disarray and growth-retarded hearts. Furthermore, we demonstrate that Prox1 is required for direct transcriptional regulation of the genes encoding the structural proteins alpha-actinin, N-RAP and zyxin, which collectively function to maintain an actin-alpha-actinin interaction as the fundamental association of the sarcomere. Aspects of abnormal heart development and the manifestation of a subset of muscular-based disease have previously been attributed to mutations in key structural proteins. Our study reveals an essential requirement for direct transcriptional regulation of sarcomere integrity, in the context of enabling foetal cardiomyocyte hypertrophy, maintenance of contractile function and progression towards inherited or acquired myopathic disease.
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