Meeting Koch's postulates for calcium signaling in cardiac hypertrophy.
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Animals↗
Biomedical subjects
K R Chien
Publications and source records attributed to K R Chien.
Myocyte survival pathways and cardiomyopathy: implications for trastuzumab cardiotoxicity.
Recent clinical studies have documented the efficacy of trastuzumab (Herceptin; Genentech, Inc, South San Francisco, CA) as a new biologically targeted therapy for erbB-2 receptor-positive forms of breast cancer. During the course of a large-scale clinical trial, a subset of patients reported the onset of symptoms and signs of cardiac failure that appeared to be aggravated by concomitant exposure to anthracyclines. The mechanisms responsible for this cardiac toxicity are unclear. However, new insights into the pathways that lead to other forms of heart failure have identified a pivotal role for myocyte survival pathways in preventing the onset of cardiomyopathy and associated heart failure in genetically engineered animal models of the disease. This mini-review highlights these recent findings and suggests the possibility that the loss of erbB-2 receptor-dependent myocyte survival pathways may create a susceptibility for the onset of heart failure in response to the cardiotoxicity of anthracycline treatment. The possibility exists that the divergent susceptibility for the onset of cardiotoxicity among patients who have received trastuzumab might ultimately reflect an inherent genetic susceptibility to the diverse mechanisms that initiate, promote, and suppress the complex pathways to heart failure.
Animals↗
Synergistic roles of neuregulin-1 and insulin-like growth factor-I in activation of the phosphatidylinositol 3-kinase pathway and cardiac chamber morphogenesis.
Cardiac chamber morphogenesis requires the coordinated growth of both cardiac muscle and endocardial cell lineages. Paracrine growth factors may modulate the coordinated cellular specification and differentiation during cardiac chamber morphogenesis, as suggested by the essential role of endothelial-derived growth factors, neuregulin-1, and insulin-like growth factor-I. Using the whole mouse embryo culture system for delivery of diffusible factors into the cardiac chamber, neuregulin-1 was shown to promote trabeculation of the ventricular wall. Another factor, insulin-like growth factor-I, had no apparent effect by itself. Combined treatment with neuregulin-1 and insulin-like growth factor-I strongly induced DNA synthesis of cardiomyocytes and expansion of both the ventricular compact zone and the atrioventricular cushions leading to chamber growth and maturation. In cultured cardiomyocytes, combined neuregulin-1 and insulin-like growth factor-I also had a synergistic effect to promote DNA synthesis and cellular growth, which were prevented by wortmannin, an inhibitor of phosphatidylinositol 3-kinase. Adenoviral delivery of dominant negative Rac1, which acts downstream of phosphatidylinositol 3-kinase, blocked the effect of combined neuregulin-1/insulin-like growth factor-I treatment. These studies support the concept that the interaction of neuregulin-1 and insulin-like growth factor-I pathways plays an important role in coordinating cardiac chamber morphogenesis and may occur through convergent activation of phosphatidylinositol 3-kinase.
Animals↗
Chronic phospholamban-sarcoplasmic reticulum calcium ATPase interaction is the critical calcium cycling defect in dilated cardiomyopathy.
Dilated cardiomyopathy and end-stage heart failure result in multiple defects in cardiac excitation-contraction coupling. Via complementation of a genetically based mouse model of dilated cardiomyopathy, we now provide evidence that progressive chamber dilation and heart failure are dependent on a Ca2+ cycling defect in the cardiac sarcoplasmic reticulum. The ablation of a muscle-specific sarcoplasmic reticulum Ca2+ ATPase (SERCA2a) inhibitor, phospholamban, rescued the spectrum of phenotypes that resemble human heart failure. Inhibition of phospholamban-SERCA2a interaction via in vivo expression of a phospholamban point mutant dominantly activated the contractility of ventricular muscle cells. Thus, interfering with phospholamban-SERCA2a interaction may provide a novel therapeutic approach for preventing the progression of dilated cardiomyopathy.
Animals↗
Signaling pathways for cardiac hypertrophy and failure.
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Animals↗
Stress pathways and heart failure.
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Animals↗
DANCE, a novel secreted RGD protein expressed in developing, atherosclerotic, and balloon-injured arteries.
We have identified and characterized mouse, rat, and human cDNAs that encode a novel secreted protein of 448 amino acids named DANCE (developmental arteries and neural crest epidermal growth factor (EGF)-like). DANCE contains six calcium-binding EGF-like domains, one of which includes an RGD motif. Overexpression studies of recombinant DANCE protein document that DANCE is a secreted 66-kDa protein. DANCE and recently described protein S1-5 comprise a new EGF-like protein family. The human DANCE gene was mapped at chromosome 14q32.1. DANCE mRNA is mainly expressed in heart, ovary, and colon in adult human tissues. Expression profile analysis by in situ hybridization revealed prominent DANCE expression in developing arteries. DANCE is also expressed in neural crest cell derivatives, endocardial cushion tissue, and several other mesenchymal tissues. In adult vessels, DANCE expression is largely diminished but is reinduced in balloon-injured vessels and atherosclerotic lesions, notably in intimal vascular smooth muscle cells and endothelial cells that lose their ability to proliferate in late stage of injury. DANCE protein was shown to promote adhesion of endothelial cells through interaction of integrins and the RGD motif of DANCE. DANCE is thus a novel vascular ligand for integrin receptors and may play a role in vascular development and remodeling.
Amino Acid Sequence↗
Situs inversus and embryonic ciliary morphogenesis defects in mouse mutants lacking the KIF3A subunit of kinesin-II.
The embryonic cellular events that set the asymmetry of the genetic control circuit controlling left-right (L-R) axis determination in mammals are poorly understood. New insight into this problem was obtained by analyzing mouse mutants lacking the KIF3A motor subunit of the kinesin-II motor complex. Embryos lacking KIF3A die at 10 days postcoitum, exhibit randomized establishment of L-R asymmetry, and display numerous structural abnormalities. The earliest detectable abnormality in KIF3A mutant embryos is found at day 7.5, where scanning electron microscopy reveals loss of cilia ordinarily present on cells of the wild-type embryonic node, which is thought to play an important role in setting the initial L-R asymmetry. This cellular phenotype is observed before the earliest reported time of asymmetric expression of markers of the L-R signaling pathway. These observations demonstrate that the kinesin-based transport pathway needed for flagellar and ciliary morphogenesis is conserved from Chlamydomonas to mammals and support the view that embryonic cilia play a role in the earliest cellular determinative events establishing L-R asymmetry.
Animals↗
Loss of a gp130 cardiac muscle cell survival pathway is a critical event in the onset of heart failure during biomechanical stress.
Biomechanical stress is a major stimulus for cardiac hypertrophy and the transition to heart failure. By generating mice that harbor a ventricular restricted knockout of the gp130 cytokine receptor via Cre-IoxP-mediated recombination, we demonstrate a critical role for a gp130-dependent myocyte survival pathway in the transition to heart failure. Such conditional mutant mice have normal cardiac structure and function, but during aortic pressure overload, these mice display rapid onset of dilated cardiomyopathy and massive induction of myocyte apoptosis versus the control mice that exhibit compensatory hypertrophy. Thus, cardiac myocyte apoptosis is a critical point in the transition between compensatory cardiac hypertrophy and heart failure. gp130-dependent cytokines may represent a novel therapeutic strategy for preventing in vivo heart failure.
Animals↗
A post-transcriptional compensatory pathway in heterozygous ventricular myosin light chain 2-deficient mice results in lack of gene dosage effect during normal cardiac growth or hypertrophy.
Our previous study of homozygous mutants of the ventricular specific isoform of myosin light chain 2 (mlc-2v) demonstrated that mlc-2v plays an essential role in murine heart development (Chen, J., Kubalak, S. W., Minamisawa, S., Price, R. L., Becker, K. D., Hickey, R., Ross, J., Jr., and Chien, K. R. (1998) J. Biol. Chem. 273, 1252-1256). As gene dosage of some myofibrillar proteins can affect muscle function, we have analyzed heterozygous mutants in depth. Ventricles of heterozygous mutants displayed a 50% reduction in mlc-2v mRNA, yet expressed normal levels of protein both under basal conditions and following induction of cardiac hypertrophy by aortic constriction. Heterozygous mutants exhibited cardiac function comparable to that of wild-type littermate controls both prior to and following aortic constriction. There were no significant differences in contractility and responses to calcium between wild-type and heterozygous unloaded cardiomyocytes. We conclude that heterozygous mutants show neither a molecular nor a physiological cardiac phenotype either at base line or following hypertrophic stimuli. These results suggest that post-transcriptional compensatory mechanisms play a major role in maintaining the level of MLC-2v protein in murine hearts. In addition, as our mlc-2v knockout mutants were created by a knock-in of Cre recombinase into the endogenous mlc-2v locus, this study demonstrates that heterozygous mlc-2v cre knock-in mice are appropriate for ventricular specific gene targeting.
Animals↗
PPAR gamma is required for placental, cardiac, and adipose tissue development.
The nuclear hormone receptor PPAR gamma promotes adipogenesis and macrophage differentiation and is a primary pharmacological target in the treatment of type II diabetes. Here, we show that PPAR gamma gene knockout results in two independent lethal phases. Initially, PPAR gamma deficiency interferes with terminal differentiation of the trophoblast and placental vascularization, leading to severe myocardial thinning and death by E10.0. Supplementing PPAR gamma null embryos with wild-type placentas via aggregation with tetraploid embryos corrects the cardiac defect, implicating a previously unrecognized dependence of the developing heart on a functional placenta. A tetraploid-rescued mutant surviving to term exhibited another lethal combination of pathologies, including lipodystrophy and multiple hemorrhages. These findings both confirm and expand the current known spectrum of physiological functions regulated by PPAR gamma.
Adipose Tissue↗
Inflammatory pathways and cardiac repair: the affliction of infarction.
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Adaptation, Biological↗
Deletion of 150 kb in the minimal DiGeorge/velocardiofacial syndrome critical region in mouse.
Deletions or rearrangements of human chromosome 22q11 lead to a variety of related clinical syndromes such as DiGeorge syndrome (DGS) and velo--cardiofacial syndrome (VCFS). In addition, patients with 22q11 deletions have an increased incidence of schizophrenia and several studies have mapped susceptibility loci for schizophrenia to this region. Human molecular genetic studies have so far failed to identify the crucial genes or disruption mechanisms that result in these disorders. We have used gene targeting in the mouse to delete a defined region within the conserved DGS critical region (DGCR) on mouse chromosome 16 to prospectively investigate the role of the mouse DGCR in 22q11 syndromes. The deletion spans a conserved portion ( approximately 150 kb) of the proximal region of the DGCR, containing at least seven genes ( Znf74l, Idd, Tsk1, Tsk2, Es2, Gscl and Ctp ). Mice heterozygous for this deletion display no findings of DGS/VCFS in either inbred or mixed backgrounds. However, heterozygous mice display an increase in prepulse inhibition of the startle response, a manifestation of sensorimotor gating that is reduced in humans with schizophrenia. Homozygous deleted mice die soon after implantation, demonstrating that the deleted region contains genes essential for early post-implantation embryonic development. These results suggest that heterozygous deletion of this portion of the DGCR is sufficient for sensorimotor gating abnormalities, but not sufficient to produce the common features of DGS/VCFS in the mouse.
Animals↗
Cardiac-specific overexpression of RhoA results in sinus and atrioventricular nodal dysfunction and contractile failure.
RhoA is a low-molecular-weight GTPase that has been implicated in the regulation of hypertrophic cardiac muscle cell growth. To study the role of RhoA in control of cardiac function in vivo, transgenic mice expressing wild-type and constitutively activated forms of RhoA under the control of the cardiac-specific alpha-myosin heavy chain promoter were generated. Transgene-positive mice expressing high levels of either wild-type or activated RhoA showed pronounced atrial enlargement and manifested a lethal phenotype, often preceded by generalized edema, with most animals dying over the course of a few weeks. Echocardiographic analysis of visibly healthy wild-type RhoA transgenic mice revealed no significant change in left ventricular function. As their condition deteriorated, significant dilation of the left ventricular chamber and associated decreases in left ventricular contractility were detected. Heart rate was grossly depressed in both wild-type and activated RhoA-expressing mice, even prior to the onset of ventricular failure. Electrocardiography showed evidence of atrial fibrillation and atrioventricular block. Interestingly, muscarinic receptor blockade with atropine did not elicit a positive chronotropic response in the transgenic mice. We suggest that RhoA regulates cardiac sinus and atrioventricular nodal function and that its overexpression results in bradycardia and development of ventricular failure.
Animals↗
Complexity in simplicity: monogenic disorders and complex cardiomyopathies.
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Actins↗
Control of segmental expression of the cardiac-restricted ankyrin repeat protein gene by distinct regulatory pathways in murine cardiogenesis.
Although accumulating evidence suggests that the heart develops in a segmental fashion, the molecular mechanisms that control regional specification of cardiomyocytes in the developing heart remain largely unknown. In this study, we have used the mouse cardiac-restricted ankyrin repeat protein (CARP) gene as a model system to study these mechanisms. The CARP gene encodes a nuclear co-regulator for cardiac gene expression, which lies downstream of the cardiac homeobox gene, Nkx 2.5, and is an early marker of the cardiac muscle cell lineage. We have demonstrated that the expression of the gene is developmentally down regulated and dramatically induced as part of the embryonic gene program during cardiac hypertrophy. Using a lacZ/knock-in mouse and three lines of transgenic mouse harboring various CARP promoter/lacZ reporters, we have identified distinct 5' cis regulatory elements of the gene that can direct heart segment-specific transgene expression, such as atrial versus ventricular and left versus right. Most interestingly, a 213 base pair sequence element of the gene was found to confer conotruncal segment-specific transgene expression. Using the transgene as a conotruncal segment-specific marker, we were able to document the developmental fate of a subset of cardiomyocytes in the conotruncus during cardiogenesis. In addition, we have identified an essential GATA-4 binding site in the proximal upstream regulatory region of the gene and cooperative transcriptional regulation mediated by Nkx2.5 and GATA-4. We have shown that this cooperative regulation is dependent on binding of GATA-4 to its cognate DNA sequence in the promoter, which suggests that Nkx2.5 controls CARP expression, at least in part, through GATA-4.
Age Factors↗
p53 is a transcriptional activator of the muscle-specific phosphoglycerate mutase gene and contributes in vivo to the control of its cardiac expression.
The role that the p53 tumor suppressor gene product plays in cellular differentiation remains controversial. However, recent evidence indicates that p53 is required for proper embryogenesis. We have studied the effect of p53 on the expression mediated by the promoter of the rat muscle-specific phosphoglycerate mutase gene (M-PGAM), a marker for cardiac and skeletal muscle differentiation. Experiments involving transient transfection, mobility shift assay, and site-directed mutagenesis demonstrated that p53 specifically binds and transactivates the M-PGAM promoter. The p53-related proteins p51A and p73L also transactivated M-PGAM. Moreover, stable expression of a p53 dominant mutant in C2C12 cells blocked the induction of M-PGAM expression during the myoblast to myotube transition and the ability of p53, p51A, and p73L to transactivate the M-PGAM promoter. In addition, impaired expression of M-PGAM was observed in a subset of p53-null animals in heart and muscle tissues of anterior-ventral location. These results demonstrate that p53 is a transcriptional activator of M-PGAM that contributes in vivo to the control of its cardiac expression. These data support previous findings indicating a role for p53 in cellular differentiation.
Animals↗
Calcineurin enhances acetylcholinesterase mRNA stability during C2-C12 muscle cell differentiation.
Treatment of C2-C12 mouse myoblasts with the immunosuppressant drug cyclosporin A (CsA) enhances the increase in acetylcholinesterase (AChE) expression observed during skeletal muscle differentiation. The enhanced AChE expression is due primarily to increased mRNA stability because CsA treatment increases the half-life of AChE mRNA, but not the apparent transcriptional rate of the gene. Neither tacrolimus (FK506), an immunosuppressive agent with a distinct structure, nor cyclosporine H, an inactive congener of CsA, alters AChE expression. The enhanced AChE expression is associated with the muscle differentiation process, but cannot be triggered by CsA exposure before differentiation. Myoblasts and myotubes of C2-C12 cells express similar amounts of cyclophilin A and FKBP12, immunophilins known to be intracellular-binding targets for CsA and tacrolimus, respectively. However, cellular levels of calcineurin, a calcium/calmodulin-dependent phosphatase known to be the cellular target of ligand-immunophilin complexes, increase 3-fold during myogenesis. Overexpression of constitutively active calcineurin in differentiating cells reduces AChE mRNA levels and CsA antagonizes such an inhibition. Conversely, overexpression of a dominant negative calcineurin construct increases AChE mRNA levels, which are further enhanced by CsA. Thus, a CsA sensitive, calcineurin mediated pathway appears linked to differentiation-induced stabilization of AChE mRNA during myogenesis.
Acetylcholinesterase↗