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Ossola D, Amarouch MY, Behr P, Vörös J, Abriel H, Zambelli T. Force-controlled patch clamp of beating cardiac cells. NANO LETTERS 2015; 15:1743-50. [PMID: 25639960 DOI: 10.1021/nl504438z] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
From its invention in the 1970s, the patch clamp technique is the gold standard in electrophysiology research and drug screening because it is the only tool enabling accurate investigation of voltage-gated ion channels, which are responsible for action potentials. Because of its key role in drug screening, innovation efforts are being made to reduce its complexity toward more automated systems. While some of these new approaches are being adopted in pharmaceutical companies, conventional patch-clamp remains unmatched in fundamental research due to its versatility. Here, we merged the patch clamp and atomic force microscope (AFM) techniques, thus equipping the patch-clamp with the sensitive AFM force control. This was possible using the FluidFM, a force-controlled nanopipette based on microchanneled AFM cantilevers. First, the compatibility of the system with patch-clamp electronics and its ability to record the activity of voltage-gated ion channels in whole-cell configuration was demonstrated with sodium (NaV1.5) channels. Second, we showed the feasibility of simultaneous recording of membrane current and force development during contraction of isolated cardiomyocytes. Force feedback allowed for a gentle and stable contact between AFM tip and cell membrane enabling serial patch clamping and injection without apparent cell damage.
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Affiliation(s)
- Dario Ossola
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich , Zurich, Switzerland
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2
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Davis J, Westfall MV, Townsend D, Blankinship M, Herron TJ, Guerrero-Serna G, Wang W, Devaney E, Metzger JM. Designing heart performance by gene transfer. Physiol Rev 2008; 88:1567-651. [PMID: 18923190 DOI: 10.1152/physrev.00039.2007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The birth of molecular cardiology can be traced to the development and implementation of high-fidelity genetic approaches for manipulating the heart. Recombinant viral vector-based technology offers a highly effective approach to genetically engineer cardiac muscle in vitro and in vivo. This review highlights discoveries made in cardiac muscle physiology through the use of targeted viral-mediated genetic modification. Here the history of cardiac gene transfer technology and the strengths and limitations of viral and nonviral vectors for gene delivery are reviewed. A comprehensive account is given of the application of gene transfer technology for studying key cardiac muscle targets including Ca(2+) handling, the sarcomere, the cytoskeleton, and signaling molecules and their posttranslational modifications. The primary objective of this review is to provide a thorough analysis of gene transfer studies for understanding cardiac physiology in health and disease. By comparing results obtained from gene transfer with those obtained from transgenesis and biophysical and biochemical methodologies, this review provides a global view of cardiac structure-function with an eye towards future areas of research. The data presented here serve as a basis for discovery of new therapeutic targets for remediation of acquired and inherited cardiac diseases.
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Affiliation(s)
- Jennifer Davis
- Department of Integrative Biology and Physiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
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3
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Hakim ZS, DiMichele LA, Doherty JT, Homeister JW, Beggs HE, Reichardt LF, Schwartz RJ, Brackhan J, Smithies O, Mack CP, Taylor JM. Conditional deletion of focal adhesion kinase leads to defects in ventricular septation and outflow tract alignment. Mol Cell Biol 2007; 27:5352-64. [PMID: 17526730 PMCID: PMC1952084 DOI: 10.1128/mcb.00068-07] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To examine a role for focal adhesion kinase (FAK) in cardiac morphogenesis, we generated a line of mice with a conditional deletion of FAK in nkx2-5-expressing cells (herein termed FAKnk mice). FAKnk mice died shortly after birth, likely resulting from a profound subaortic ventricular septal defect and associated malalignment of the outflow tract. Additional less penetrant phenotypes included persistent truncus arteriosus and thickened valve leaflets. Thus, conditional inactivation of FAK in nkx2-5-expressing cells leads to the most common congenital heart defect that is also a subset of abnormalities associated with tetralogy of Fallot and the DiGeorge syndrome. No significant differences in proliferation or apoptosis between control and FAKnk hearts were observed. However, decreased myocardialization was observed for the conal ridges of the proximal outflow tract in FAKnk hearts. Interestingly, chemotaxis was significantly attenuated in isolated FAK-null cardiomyocytes in comparison to genetic controls, and these effects were concomitant with reduced tyrosine phosphorylation of Crk-associated substrate (CAS). Thus, it is possible that ventricular septation and appropriate outflow tract alignment is dependent, at least in part, upon FAK-dependent CAS activation and subsequent induction of polarized myocyte movement into the conal ridges. Future studies will be necessary to determine the precise contributions of the additional nkx2-5-derived lineages to the phenotypes observed.
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Affiliation(s)
- Zeenat S Hakim
- Department of Pathology and Carolina Cardiovascular Biology Center, 501 Brinkhous-Bullitt Bldg. CB 7525, University of North Carolina, Chapel Hill, NC 27599, USA
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4
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Nelson PR, Kent KC. Microinjection of DNA into the nuclei of human vascular smooth muscle cells. J Surg Res 2002; 106:202-8. [PMID: 12127827 DOI: 10.1006/jsre.2002.6453] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND It is challenging to successfully transfect human vascular cells by conventional techniques. We evaluated the efficiency of transfection of human smooth muscle cells (SMC) using a method of direct nuclear microinjection of DNA constructs. MATERIALS AND METHODS The nuclei of explanted human saphenous vein SMC were microinjected with the plasmid pCMVbeta, containing the lacZ gene for beta-galactosidase (beta-gal). Efficiency of injection and expression were assessed by histochemical staining for beta-gal. Injected SMC were subjected to standard assays of viability and migration. RESULTS Parameters affecting the conditions of injection were systematically analyzed to achieve optimal transfection efficiency. A vertical injection resulted in a twofold increase in expression of beta-gal compared to a horizontal approach. A DNA concentration of 100 ng/microl (390 copies/injection) provided a maximal rate of expression. No further increase in expression was evident at higher concentrations. Maximal expression was achieved with a time of injection of 200-500 ms, an injection pressure of 5-10 psi, and a pipette tip size of 0.6 microm, resulting in an injection volume of 0.03 pl. Cytoplasmic injection did not result in gene expression. The ability of SMC to migrate under videomicroscopy was not altered by the injection process. Optimizing all injection parameters resulted in cell viability >95% and efficiency of injection of 59%. CONCLUSION DNA encoding a variety of intracellular proteins can be efficiently microinjected into human vascular SMC. Coupled with the use of videomicroscopy, this technique can allow for the evaluation of genes that might modulate important cellular processes such as proliferation and migration.
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Affiliation(s)
- Peter R Nelson
- Division of Vascular Surgery, University of Massachusetts Medical School, Worchester, MA 01655, USA
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Mohammad-Panah R, Gyomorey K, Rommens J, Choudhury M, Li C, Wang Y, Bear CE. ClC-2 contributes to native chloride secretion by a human intestinal cell line, Caco-2. J Biol Chem 2001; 276:8306-13. [PMID: 11096079 DOI: 10.1074/jbc.m006764200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It has been previously determined that ClC-2, a member of the ClC chloride channel superfamily, is expressed in certain epithelial tissues. These findings fueled speculation that ClC-2 can compensate for impaired chloride transport in epithelial tissues affected by cystic fibrosis and lacking the cystic fibrosis transmembrane conductance regulator. However, direct evidence linking ClC-2 channel expression to epithelial chloride secretion was lacking. In the present studies, we show that ClC-2 transcripts and protein are present endogenously in the Caco-2 cell line, a cell line that models the human small intestine. Using an antisense strategy we show that ClC-2 contributes to native chloride currents in Caco-2 cells measured by patch clamp electrophysiology. Antisense ClC-2-transfected monolayers of Caco-2 cells exhibited less chloride secretion (monitored as iodide efflux) than did mock transfected monolayers, providing the first direct molecular evidence that ClC-2 can contribute to chloride secretion by the human intestinal epithelium. Further, examination of ClC-2 localization by confocal microscopy revealed that ClC-2 contributes to secretion from a unique location in this epithelium, from the apical aspect of the tight junction complex. Hence, these studies provide the necessary rationale for considering ClC-2 as a possible therapeutic target for diseases affecting intestinal chloride secretion such as cystic fibrosis.
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Affiliation(s)
- R Mohammad-Panah
- Programme in Cell Biology and Genetics at the Hospital for Sick Children and the Departments of Physiology and Molecular Genetics at the University of Toronto, Toronto, M5G 1X8 Ontario, Canada
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6
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Bony C, Roche S, Shuichi U, Sasaki T, Crackower MA, Penninger J, Mano H, Pucéat M. A specific role of phosphatidylinositol 3-kinase gamma. A regulation of autonomic Ca(2)+ oscillations in cardiac cells. J Cell Biol 2001; 152:717-28. [PMID: 11266463 PMCID: PMC2195768 DOI: 10.1083/jcb.152.4.717] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Purinergic stimulation of cardiomyocytes turns on a Src family tyrosine kinase-dependent pathway that stimulates PLCgamma and generates IP(3), a breakdown product of phosphatidylinositol 4,5-bisphosphate (PIP2). This signaling pathway closely regulates cardiac cell autonomic activity (i.e., spontaneous cell Ca(2+) spiking). PIP2 is phosphorylated on 3' by phosphoinositide 3-kinases (PI3Ks) that belong to a broad family of kinase isoforms. The product of PI3K, phosphatidylinositol 3,4,5-trisphosphate, regulates activity of PLCgamma. PI3Ks have emerged as crucial regulators of many cell functions including cell division, cell migration, cell secretion, and, via PLCgamma, Ca(2+) homeostasis. However, although PI3Kalpha and -beta have been shown to mediate specific cell functions in nonhematopoietic cells, such a role has not been found yet for PI3Kgamma. We report that neonatal rat cardiac cells in culture express PI3Kalpha, -beta, and -gamma. The purinergic agonist predominantly activates PI3Kgamma. Both wortmannin and LY294002 prevent tyrosine phosphorylation, and membrane translocation of PLCgamma as well as IP(3) generation in ATP-stimulated cells. Furthermore, an anti-PI3Kgamma, but not an anti-PI3Kbeta, injected in the cells prevents the effect of ATP on cell Ca(2+) spiking. A dominant negative mutant of PI3Kgamma transfected in the cells also exerts the same action. The effect of ATP was observed on spontaneous Ca(2+) spiking of wild-type but not of PI3Kgamma(2/2) embryonic stem cell-derived cardiomyocytes. ATP activates the Btk tyrosine kinase, Tec, and induces its association with PLCgamma. A dominant negative mutant of Tec blocks the purinergic effect on cell Ca(2+) spiking. Tec is translocated to the T-tubes upon ATP stimulation of cardiac cells. Both an anti-PI3Kgamma antibody and a dominant negative mutant of PI3Kgamma injected or transfected into cells prevent the latter event. We conclude that PI3Kgamma activation is a crucial step in the purinergic regulation of cardiac cell spontaneous Ca(2+) spiking. Our data further suggest that Tec works in concert with a Src family kinase and PI3Kgamma to fully activate PLCgamma in ATP-stimulated cardiac cells. This cluster of kinases provides the cardiomyocyte with a tight regulation of IP(3) generation and thus cardiac autonomic activity.
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Affiliation(s)
- Claire Bony
- The French Institute of Health and Medical Research, CNRS UPR1086 Montpellier 34293, France
| | - Serge Roche
- the Center for Research of Macromolecular Biochemistry, CNRS UPR1086 Montpellier 34293, France
| | - Ueno Shuichi
- Division of Functional Genomics, Jichi Medical School, Tochigi, 329-04 Japan
| | - Takehiko Sasaki
- Amgen Institute, Ontario Cancer Institute, Department of Medical Biophysics and Immunology, Toronto, Ontario, MSG 2C1 Canada
| | - Michael A. Crackower
- Amgen Institute, Ontario Cancer Institute, Department of Medical Biophysics and Immunology, Toronto, Ontario, MSG 2C1 Canada
| | - Josef Penninger
- Amgen Institute, Ontario Cancer Institute, Department of Medical Biophysics and Immunology, Toronto, Ontario, MSG 2C1 Canada
| | - Hiroyuki Mano
- Division of Functional Genomics, Jichi Medical School, Tochigi, 329-04 Japan
| | - Michel Pucéat
- the Center for Research of Macromolecular Biochemistry, CNRS UPR1086 Montpellier 34293, France
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Richards SM, Jaconi ME, Vassort G, Pucéat M. A spliced variant of AE1 gene encodes a truncated form of Band 3 in heart: the predominant anion exchanger in ventricular myocytes. J Cell Sci 1999; 112 ( Pt 10):1519-28. [PMID: 10212146 DOI: 10.1242/jcs.112.10.1519] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The anion exchangers (AE) are encoded by a multigenic family that comprises at least three genes, AE1, AE2 and AE3, and numerous splicoforms. Besides regulating intracellular pH (pHi) via the Cl-/HCO3- exchange, the AEs exert various cellular functions including generation of a senescent antigen, anchorage of the cytoskeleton to the membrane and regulation of metabolism. Most cells express several AE isoforms. Despite the key role of this family of proteins, little is known about the function of specific AE isoforms in any tissue, including the heart. We therefore chose isolated cardiac cells, in which a tight control of pHi is mandatory for the excitation-contraction coupling process, to thoroughly investigate the expression of the AE genes at both the mRNA and protein levels. RT-PCR revealed the presence of AE1, AE2 and AE3 mRNAs in both neonatal and adult rat cardiomyocytes. AE1 is expressed both as the erythroid form (Band 3 or eAE1) and a novel alternate transcript (nAE1), which was more specifically characterized using a PCR mapping strategy. Two variants of AE2 (AE2a and AE2c) were found at the mRNA level. Cardiac as well as brain AE3 mRNAs were expressed in both neonatal and adult rat cardiomyocytes. Several AE protein isoforms were found, including a truncated form of AE1 and two AE3s, but there was no evidence of AE2 protein in adult rat cardiomyocytes. In cardiomyocytes transfected with an AE3 oligodeoxynucleotide antisense, AE3 immunoreactivity was dramatically decreased but the activity of the Cl-/HCO3- exchange was unchanged. In contrast, intracellular microinjection of blocking anti-AE1 antibodies inhibited the AE activity. Altogether, our findings suggest that a specific and novel AE1 splicoform (nAE1) mediates the cardiac Cl-/HCO3- exchange. The multiple gene and protein expression within the same cell type suggest numerous functions for this protein family.
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Affiliation(s)
- S M Richards
- INSERM U-390, Laboratoire de Physiopathologie Cardiovasculaire, CHU Arnaud de Villeneuve, Montpellier, France
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8
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Mohammad-Panah R, Demolombe S, Riochet D, Leblais V, Loussouarn G, Pollard H, Baró I, Escande D. Hyperexpression of recombinant CFTR in heterologous cells alters its physiological properties. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C310-8. [PMID: 9486119 DOI: 10.1152/ajpcell.1998.274.2.c310] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We investigated whether high levels of expression of the cystic fibrosis transmembrane conductance regulator (CFTR) would alter the functional properties of newly synthesized recombinant proteins. COS-7, CFPAC-1, and A549 cells were intranuclearly injected with a Simian virus 40-driven pECE-CFTR plasmid and assayed for halide permeability using the 6-methoxy-N-(3-sulfopropyl)quinolinium fluorescent probe. With increasing numbers of microinjected pECE-CFTR copies, the baseline permeability to halide dose dependently increased, and the response to adenosine 3',5'-cyclic monophosphate (cAMP) stimulation decreased. In cells hyperexpressing CFTR, the high level of halide permeability was reduced when a cell metabolism poisoning cocktail was applied to decrease intracellular ATP and, inversely, was increased by orthovanadate. In CFPAC-1 cells investigated with the patch-clamp technique, CFTR hyperexpression led to a time-independent nonrectifying chloride current that was not sensitive to cAMP stimulation. CFPAC-1 cells hyperexpressing CFTR exhibited no outward rectifying chloride current nor inward rectifying potassium current either spontaneously or under cAMP stimulation. We conclude that hyperexpression of recombinant CFTR proteins modifies their properties inasmuch as 1) CFTR channels are permanently activated and not susceptible to cAMP regulation and 2) they lose their capacity to regulate heterologous ionic channels.
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Affiliation(s)
- R Mohammad-Panah
- Laboratoire de Physiopathologie et de Pharmacologie Cellulaires et Moléculaires, Institut National de la Santé et de la Recherche Médicale CJF96-01, Hôpital Hotel-Dieu, Nantes, France
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9
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Nagy JI, Li WE, Roy C, Doble BW, Gilchrist JS, Kardami E, Hertzberg EL. Selective monoclonal antibody recognition and cellular localization of an unphosphorylated form of connexin43. Exp Cell Res 1997; 236:127-36. [PMID: 9344592 DOI: 10.1006/excr.1997.3716] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A sequence-specific monoclonal antibody directed against the gap junction protein connexin43 (Cx43) is shown here to be specific for the unphosphorylated form of this protein. In tissues and cultured cells containing different phosphorylated and unphosphorylated forms of Cx43, the antibody detected only the latter as shown by Western blotting of native and alkaline phosphatase-treated samples. Immunohistochemically, this monoclonal antibody did not recognize gap junctions in the vast majority of cultured cardiac myocytes, where nearly all detectable Cx43 is phosphorylated. In contrast, it was able to detect some intracellular Cx43 in tracheal smooth muscle cells and an epithelial cell line (Cl-9 cells), producing patterns of labeling consistent with those seen using a polyclonal antibody that recognizes both phosphorylated and unphosphorylated forms of Cx43. Immunostaining of gap junctions in the cultured cells indicates that both phosphorylated and unphosphorylated Cx43 are present in some assembled gap junctions, suggesting that assembled junctions do not contain exclusively the phosphorylated form of the protein. Annular gap junctions, believed to form as part of the pathway for internalization and degradation of gap junctions, were only occasionally and sparsely labeled by the monoclonal antibody, indicating that complete protein dephosphorylation is not required for uptake and degradation of gap junctions. Furthermore, the ability of this antibody to recognize only unphosphorylated Cx43, and not any of the phosphorylated forms present in the tissues and cell types examined, suggests that a unique phosphorylation site, perhaps present in the epitope recognized by this antibody, must be phosphorylated prior to phosphorylation of Cx43 at other sites.
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Affiliation(s)
- J I Nagy
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
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10
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Ross RS, Navankasattusas S, Harvey RP, Chien KR. An HF-1a/HF-1b/MEF-2 combinatorial element confers cardiac ventricular specificity and established an anterior-posterior gradient of expression. Development 1996; 122:1799-809. [PMID: 8674419 DOI: 10.1242/dev.122.6.1799] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The molecular determinants that direct gene expression to the ventricles of the heart are for the most part unknown. Additionally, little data is available on how the anterior/posterior axis of the heart tube is determined and whether the left and right atrial and ventricular chambers are assigned as part of this process. Utilizing myosin light chain-2 ventricular promoter/beta-galactosidase reporter transgenes, we have determined the minimal cis-acting sequences required for ventricular-specific gene expression. In multiple independent transgenic mouse lines, we found that both a 250 base pair myosin light chain-2 ventricular promoter fragment, as well as a dimerized 28 bp sub-element (HF-1) containing binding sites for HF1a and HF1b/MEF2 factors, directed ventricular-specific reporter expression from as early as the endogenous gene, at day 7.5-8.0 post coitum. While the endogenous gene is expressed uniformly throughout both ventricles, the transgenes were expressed in a right ventricular/conotruncal dominant fashion, suggesting that they contain only a subset of the elements which respond to positional information in the developing heart tube. Expression of the transgene was cell autonomous and its temporospatial characteristics not affected by mouse strain/methylation state of the genome. To determine whether ventricular-specific expression of the transgene was dependent upon regulatory genes required for correct ventricular differentiation, the 250 base pair transgene was bred into both retinoid X receptoralpha and Nkx2-5 null backgrounds. The transgene was expressed in both mutant backgrounds, despite the absence of endogenous myosin light chain-2 ventricular transcript in Nkx2-5 null embryos. Ventricular specification, as judged by transgene expression, appeared to occur normally in both mutants. Thus, the HF-1 element, directs chamber-specific transcription of a transgene reporter independently of retinoid X receptoralpha and Nkx2-5, and defines a minimal combinatorial pathway for ventricular chamber gene expression. The patterned expression of this transgene may provide a model system in which to investigate the cues that dictate anterior-posterior (right ventricle/left ventricle) gradients during mammalian heart development.
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Affiliation(s)
- R S Ross
- Department of Medicine, Center for Molecular Genetics, University of California, San Diego, School of Medicine, La Jolla 92093, USA
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11
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[26]Molecular analysis of cardiac muscle diseases based on mouse genetics. Hum Mol Genet 1996. [DOI: 10.1016/s1067-2389(96)80059-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] Open
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12
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Gregorio CC, Weber A, Bondad M, Pennise CR, Fowler VM. Requirement of pointed-end capping by tropomodulin to maintain actin filament length in embryonic chick cardiac myocytes. Nature 1995; 377:83-6. [PMID: 7544875 DOI: 10.1038/377083a0] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Control of actin filament length and dynamics is important for cell motility and architecture and is regulated in part by capping proteins that block elongation and depolymerization at both the fast-growing (barbed) and slow-growing (pointed) ends. Tropomodulin is a capping protein for the pointed end of the actin filament; it is associated with the free, pointed ends of the thin filaments in striated muscle, where it is thought to bind to both tropomyosin and actin. In embryonic chick cardiac myocytes, tropomodulin assembles after the thin, as well as the thick, filaments have become organized into periodic I and A bands, suggesting that tropomodulin might be involved in maintaining actin filament length. Here we show that microinjection of an antibody that inhibits tropomodulin's pointed-end-capping activity in vitro results in a marked elongation of actin filaments from their pointed ends and a > 80% reduction in the percentage of beating cells. This demonstrates that pointed-end capping by tropomodulin is required to maintain actin filament length in vivo and that this is essential for contractile function in embryonic chick cardiac myocytes.
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Affiliation(s)
- C C Gregorio
- Department of Cell Biology, Scripps Research Institute, La Jolla, California 92037, USA
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13
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Hansen CA, Joseph SK, Robishaw JD. Ins 1,4,5-P3 and Ca2+ signaling in quiescent neonatal cardiac myocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1224:517-26. [PMID: 7803511 DOI: 10.1016/0167-4889(94)90289-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Activation of alpha 1-adrenergic receptors in neonatal cardiac myocytes results in changes in contractile activity and the induction of hypertrophic growth. The biochemical mechanisms responsible for these diverse effects are not yet established, but presumably involve the associated alpha 1-adrenergic stimulation of phosphatidylinositol (PI) hydrolysis, with concomitant generation of Ins 1,4,5-P3 and diacylglycerol. This study examined whether alpha 1-adrenergic generation of Ins 1,4,5-P3 in intact, quiescent, neonatal cardiac myocytes resulted in a Ca2+ signal. Stimulation of myocytes with norepinephrine in the presence of propranolol caused accumulation of inositol mono-, bis and trisphosphates. However, alpha 1-adrenergic stimulation did not alter cytosolic free Ca2+ levels in 85% of the myocytes examined. Direct generation of Ins 1,4,5-P3, by photolysis of microinjected caged Ins 1,4,5-P3, was also unable to alter cytosolic free Ca2+ levels, despite the presence of Ins 1,4,5-P3 receptors. Taken together, these data indicated that alpha 1-adrenergic stimulation did not initiate Ca2+ signaling because Ins 1,4,5-P3-induced Ca2+ mobilization was not operative in quiescent neonatal cardiac myocytes. Normal excitation-contraction Ca2+ handling mechanisms were present in these cells, as illustrated by depolarization- and caffeine-induced Ca2+ transients. Analysis of these same myocytes following 48 h in the presence of norepinephrine and propranolol showed a 40% increase in the ratio of protein to DNA and a 350% increase in release of atrial naturietic factor, compared to control cells, indicating the normal operation of alpha 1-adrenergic-induced hypertrophic growth. Therefore, the assumption that Ca(2+)-dependent processes will be activated by receptor signaling pathways coupled to enhanced phosphatidylinositol turnover in cardiac cells must be avoided. In addition, the data presented in this study clearly indicated that an increase in cytosolic free Ca2+ was not necessary for the induction of alpha 1-adrenergic-mediated cardiac hypertrophy.
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Affiliation(s)
- C A Hansen
- Geisinger Clinic, Weis Center For Research, Danville, PA 17822-2619
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14
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Gq- and ras-dependent pathways mediate hypertrophy of neonatal rat ventricular myocytes following alpha 1-adrenergic stimulation. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)36858-8] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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16
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O'Brien TX, Lee KJ, Chien KR. Positional specification of ventricular myosin light chain 2 expression in the primitive murine heart tube. Proc Natl Acad Sci U S A 1993; 90:5157-61. [PMID: 8506363 PMCID: PMC46674 DOI: 10.1073/pnas.90.11.5157] [Citation(s) in RCA: 169] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
To study the process of ventricular specification during cardiogenesis, we examined the in situ expression of cardiac ventricular myosin light chain 2 (MLC-2v) mRNA during murine embryogenesis. As assessed by hybridization with a specific MLC-2v riboprobe, mRNA expression can be found in the ventricular region at day 8.0 postcoitum (pc). MLC-2v expression is high in the ventricular portion of the heart tube, with no detectable expression in the atrial or sinus venosus regions. The proximal outflow tract of the heart tube also expresses MLC-2v mRNA at minimally detectable levels at this time but then displays a temporally and spatially distinct pattern with expression well established in the proximal out-flow tract region adjacent to the ventricular segment by days 9-10 pc, eventually reaching levels comparable to the trabeculated ventricular myocardium. By day 11 pc, prior to the completion of septation, expression then becomes restricted to the ventricular region at and below the level of the atrioventricular cushion. Transgenic mice harboring a 250-base-pair MLC-2v promoter fragment fused to a luciferase reporter gene demonstrate reporter gene activity from at least day 9 pc. Ventricular region-restricted expression of the luciferase reporter in the embryonic heart, as assessed by immunofluorescence and direct assay of reporter activity in microdissected atrial and ventricular muscle specimens, was confirmed from at least day 15 pc on. Taken together, this provides evidence for early positional specification of MLC-2v gene expression in the primitive heart tube and indicates regional specification of part of the ventricular muscle gene program can precede ventricular septation during mammalian cardiogenesis. Since the 250-base-pair promoter fragment is active developmentally in transgenic mice, this establishes it as a molecular target for the process of ventricular specification in the developing heart tube.
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Affiliation(s)
- T X O'Brien
- Department of Medicine, Veterans Administration Medical Center, La Jolla, CA
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Thorburn A, Thorburn J, Chen S, Powers S, Shubeita H, Feramisco J, Chien K. HRas-dependent pathways can activate morphological and genetic markers of cardiac muscle cell hypertrophy. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53988-0] [Citation(s) in RCA: 150] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Myosin light chain-2 luciferase transgenic mice reveal distinct regulatory programs for cardiac and skeletal muscle-specific expression of a single contractile protein gene. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)49616-6] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Chien R. Signaling mechanisms for the activation of an embryonic gene program during the hypertrophy of cardiac ventricular muscle. Basic Res Cardiol 1992; 87 Suppl 2:49-58. [PMID: 1299210 DOI: 10.1007/978-3-642-72477-0_5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
To study the signaling mechanisms which mediate ventricular hypertrophy, we utilized the induction of the ANF gene as a marker of the hypertrophic response. The induction of the atrial natriuretic factor gene (ANF) is one of the most conserved features of ventricular hypertrophy, occurring in multiple species (mouse, rat, hamster, canine, and human) in response to diverse stimuli (hormonal, mechanical, pressure/volume overload, genetic, IHSS, hypertension, etc.). The ANF gene is expressed in both the atrial and ventricular compartments during embryonic development, but shortly after birth ANF expression is down-regulated to negligible levels in the adult myocardium. Since the reactivation of ANF gene expression in the hypertrophied ventricle is a hallmark of the activation of an embryonic gene program, it has also become of interest to determine if similar mechanisms activate ANF expression during hypertrophy and the initial stages of cardiogenesis. A combination of cotransfection, microinjection, and transgenic approaches has been coupled to well characterized cultured cell systems and in vivo murine models employing normal and transgenic mice. The microinjection of oncogenic RAS proteins into living myocardial cells does not lead to the activation of cell proliferation, but activates ANF gene expression, as assessed by immunofluorescence. Co-transfection of mutant and wild-type RAS expression vectors with a ANF-luciferase fusion gene supports a direct effect of activated RAS on ANF gene transcription. Co-transfection of a dominant negative RAS vector effectively inhibits the induction of the ANF gene during alpha adrenergic mediated hypertrophy of ventricular muscle cells, thereby establishing that a RAS-mediated pathway is required for ANF induction.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R Chien
- Department of Medicine, University of California, San Diego
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