Myostatin, the cardiac chalone of insulin-like growth factor-1.
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Acromegaly↗
Biomedical subjects
Vinciane Gaussin
Publications and source records attributed to Vinciane Gaussin.
Alk3/Bmpr1a receptor is required for development of the atrioventricular canal into valves and annulus fibrosus.
Endocardial cushions are precursors of mature atrioventricular (AV) valves. Their formation is induced by signaling molecules originating from the AV myocardium, including bone morphogenetic proteins (BMPs). Here, we hypothesized that BMP signaling plays an important role in the AV myocardium during the maturation of AV valves from the cushions. To test our hypothesis, we used a unique Cre/lox system to target the deletion of a floxed Alk3 allele, the type IA receptor for BMPs, to cardiac myocytes of the AV canal (AVC). Lineage analysis indicated that cardiac myocytes of the AVC contributed to the tricuspid mural and posterior leaflets, the mitral septal leaflet, and the atrial border of the annulus fibrosus. When Alk3 was deleted in these cells, defects were seen in the same leaflets, ie, the tricuspid mural leaflet and mitral septal leaflet were longer, the tricuspid posterior leaflet was displaced and adherent to the ventricular wall, and the annulus fibrosus was disrupted resulting in ventricular preexcitation. The defects seen in mice with AVC-targeted deletion of Alk3 provide strong support for a role of Alk3 in human congenital heart diseases, such as Ebstein's anomaly. In conclusion, our mouse model demonstrated critical roles for Alk3 signaling in the AV myocardium during the development of AV valves and the annulus fibrosus.
Animals↗
Program of cell survival underlying human and experimental hibernating myocardium.
Hibernating myocardium refers to chronically dysfunctional myocardium in patients with coronary artery disease in which cardiac viability is maintained and whose function improves after coronary revascularization. It is our hypothesis that long-term adaptive genomic mechanisms subtend the survival capacity of this ischemic myocardium. Therefore, the goal of this study was to determine whether chronic repetitive ischemia elicits a gene program of survival protecting hibernating myocardium against cell death. Accordingly, we measured the expression of survival genes in hibernating myocardium, both in patients surgically treated for hibernation and in a chronic swine model of repetitive ischemia reproducing the features of hibernation. Human hibernating myocardium was characterized by an upregulation of genes and corresponding proteins involved in anti-apoptosis (IAP), growth (VEGF, H11 kinase), and cytoprotection (HSP70, HIF-1alpha, GLUT1). In the swine model, the same genes and proteins were upregulated after repetitive ischemia, which was accompanied by a concomitant decrease in myocyte apoptosis. These changes characterize viable tissue, because they were not found in irreversibly injured myocardium. Our report demonstrates a novel mechanism by which the activation of an endogenous gene program of cell survival underlies the sustained viability of the hibernating heart. Potentially, promoting such a program offers a novel opportunity to salvage postmitotic tissues in conditions of ischemia.
Adult↗
Offbeat mice.
This review summarizes the recent advances in understanding the development and function of the cardiac conduction system using genetically modified mice. Null mice for different cardiac connexins confirmed their suspected roles in cardiac conduction and, in addition, unraveled unexpected roles in cardiac morphogenesis. Genetically modified mice with LacZ-labeled conduction system cells are indispensable tools to the further understanding of the mechanisms governing the development of this system in the mammalian heart. Mouse models also addressed the role and contribution of specific signaling molecules, such as PRKAG2, Nkx2.5, ALK3, and Tbx5, in the development of the cardiac conduction system and the pathogenesis of cardiac dysfunction in humans.
Animals↗
Common genomic response in different mouse models of beta-adrenergic-induced cardiomyopathy.
BACKGROUND: Although beta-adrenergic receptor (AR) blockade therapy is beneficial in the treatment of heart failure, little is known regarding the transcriptional mechanisms underlying this salutary action. METHODS AND RESULTS: In the present study, we screened mice overexpressing Gsalpha, beta1AR, beta2AR, or protein kinase A to test if a common genomic pathway exists in different models with enhanced beta-adrenergic signaling. In mice overexpressing Gsalpha, differentially expressed genes were identified by mRNA profiling. In addition to well-known markers of cardiac hypertrophy (atrial natriuretic factor, CARP, and beta-myosin heavy chain), uncoupling protein 2 (UCP2), a protein involved in the control of mitochondrial membrane potential, and four-and-a-half LIM domain protein-1 (FHL1), a member of the LIM protein family, were predicted to be upregulated. Upregulation of these genes was confirmed by quantitative reverse transcriptase-polymerase chain reaction at all time points tested during the development of cardiomyopathy in mice overexpressing Gsalpha. In mice overexpressing beta1AR, beta2AR, or protein kinase A, increased UCP2 and FHL1 expression was also observed at the onset of cardiomyopathy. BetaAR blockade treatment reversed the cardiomyopathy and suppressed the increased expression of UCP2 and FHL1 in mice overexpressing Gsalpha. CONCLUSIONS: UCP2 and FHL1 are important candidate genes that correlate with the development of betaAR-induced cardiomyopathy in different mouse models with enhanced betaAR signaling. In addition to preserving cardiac function, betaAR blockade treatment also prevents the genomic regulation that correlates with the onset of heart failure.
Adrenergic beta-Antagonists↗
Cardiac progenitor cells from adult myocardium: homing, differentiation, and fusion after infarction.
Potential repair by cell grafting or mobilizing endogenous cells holds particular attraction in heart disease, where the meager capacity for cardiomyocyte proliferation likely contributes to the irreversibility of heart failure. Whether cardiac progenitors exist in adult myocardium itself is unanswered, as is the question whether undifferentiated cardiac precursor cells merely fuse with preexisting myocytes. Here we report the existence of adult heart-derived cardiac progenitor cells expressing stem cell antigen-1. Initially, the cells express neither cardiac structural genes nor Nkx2.5 but differentiate in vitro in response to 5'-azacytidine, in part depending on Bmpr1a, a receptor for bone morphogenetic proteins. Given intravenously after ischemia/reperfusion, cardiac stem cell antigen 1 cells home to injured myocardium. By using a Cre/Lox donor/recipient pair (alphaMHC-Cre/R26R), differentiation was shown to occur roughly equally, with and without fusion to host cells.
Animals↗
Characterization of pDJA1, a cardiac-specific chaperone found by genomic profiling of the post-ischemic swine heart.
BACKGROUND: Previously, we showed by subtractive hybridization in a swine model of ischemia/reperfusion that an upregulation of genes participating in mechanisms of cell survival is a potential genomic mechanism to tilt the balance from necrosis to functional reversibility. METHODS AND RESULTS: We present here the full-length sequencing and characterization of a novel gene that was found in this subtraction, encoding a cardiac-specific DnaJ-like co-chaperone that we call Pig DnaJ-like protein A1 (pDJA1). The expression of pDJA1 was found to be restricted to the heart, as opposed to skeletal muscle, liver, lung, kidney, aorta, stomach and spleen. Expression of pDJA1 is restricted to cardiac myocytes, as determined by in situ hybridization. The transcript is expressed more in the left ventricle than in the other cardiac chambers. Remarkably, expression of pDJA1 follows a transmural gradient in the left ventricle, with the highest level of expression in the subendocardium. Expression of pDJA1 slightly increased during an episode of ischemia, but increased by 4-fold during the following period of reperfusion. Adenovirus-mediated transduction of pDJA1 in isolated rat neonatal cardiac myocytes decreased by 65% the rate of apoptosis induced by staurosporine. CONCLUSION: Therefore, pDJA1 is a novel heart-specific, ventricle-enriched cardioprotective co-chaperone, which participates in the program of cell survival that limits irreversible damage in post-ischemic myocardium.
Adenoviridae↗
Tempting fate: BMP signals for cardiac morphogenesis.
Heart muscle cell specification (cardiac myogenesis) and creating the four-chambered heart (cardiac morphogenesis) are subject to regulation, in certain model organisms, by bone morphogenetic proteins and their receptors. Extrapolation to mammals from organisms that develop outside the mother (flies, fish, frogs, and avians) has been confounded by very early lethality-at gastrulation-of many null alleles needed to prove cause-effect relations in this pathway. Here, we describe the use of lineage- or compartment-restricted null alleles as well as hypomorphic alleles, which circumvent these limitations and pinpoint novel essential functions for the bone morphogenetic protein cascade in mammalian cardiac development.
Animals↗
H11 kinase is a novel mediator of myocardial hypertrophy in vivo.
By subtractive hybridization, we found a significant increase in H11 kinase transcript in large mammalian models of both ischemia/reperfusion (stunning) and chronic pressure overload with hypertrophy. Because this gene has not been characterized in the heart, the goal of the present study was to determine the function of H11 kinase in cardiac tissue, both in vitro and in vivo. In isolated neonatal rat cardiac myocytes, adenoviral-mediated overexpression of H11 kinase resulted in a 37% increase in protein/DNA ratio, reflecting hypertrophy. A cardiac-specific transgene driven by the alphaMHC-promoter was generated, which resulted in an average 7-fold increase in H11 kinase protein expression. Transgenic hearts were characterized by a 30% increase of the heart weight/body weight ratio, by the reexpression of a fetal gene program, and by concentric hypertrophy with preserved contractile function at echocardiography. This phenotype was accompanied by a dose-dependent activation of Akt/PKB and p70(S6) kinase, whereas the MAP kinase pathway was unaffected. Thus, H11 kinase represents a novel mediator of cardiac cell growth and hypertrophy.
Animals↗
Endocardial cushion and myocardial defects after cardiac myocyte-specific conditional deletion of the bone morphogenetic protein receptor ALK3.
Receptors for bone morphogenetic proteins (BMPs), members of the transforming growth factor-beta (TGFbeta) superfamily, are persistently expressed during cardiac development, yet mice lacking type II or type IA BMP receptors die at gastrulation and cannot be used to assess potential later roles in creation of the heart. Here, we used a Cre/lox system for cardiac myocyte-specific deletion of the type IA BMP receptor, ALK3. ALK3 was specifically required at mid-gestation for normal development of the trabeculae, compact myocardium, interventricular septum, and endocardial cushion. Cardiac muscle lacking ALK3 was specifically deficient in expressing TGFbeta2, an established paracrine mediator of cushion morphogenesis. Hence, ALK3 is essential, beyond just the egg cylinder stage, for myocyte-dependent functions and signals in cardiac organogenesis.
Animals↗
Quaking is essential for blood vessel development.
For nearly 40 years functional studies of the mouse quaking gene (qkI) have focused on its role in the postnatal central nervous system during myelination. However, the homozygous lethality of a number of ENU-induced alleles reveals that quaking has a critical role in embryonic development prior to the start of myelination. In this article, we show that quaking has a previously unsuspected and essential role in blood vessel development. Interestingly, we found that quaking, a nonsecreted protein, is expressed in the yolk sac endoderm, adjacent to the mesodermal site of developing blood islands, where the differentiation of blood and endothelial cells first occurs. Antibodies against PE-CAM-1, TIE-2 and SM-alpha-actin reveal that embryos homozygous for the qk(k2) allele have defective yolk sac vascular remodeling and abnormal vessels in the embryo proper at midgestation, coinciding with the timing of embryonic death. However, these mutants exhibit normal expression of Nkx2.5 and alpha-sarcomeric actin, indicating that cardiac muscle differentiation was normal. Further, they had normal embryonic heart rates in culture, suggesting that cardiac function was not compromised at this stage of embryonic development. Together, these results suggest that quaking plays an essential role in vascular development and that the blood vessel defects are the cause of embryonic death.
Animals↗