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1.  Mice carrying a conditional Serca2flox allele for the generation of Ca2+ handling-deficient mouse models 
Cell calcium  2009;46(3):219-225.
Sarco(endo)plasmic reticulum calcium ATPases (SERCA) are cellular pumps that transport Ca2+ into the sarcoplasmic reticulum (SR). Serca2 is the most widely expressed gene family member. The very early embryonic lethality of Serca2null mouse embryos has precluded further evaluation of loss of Serca2 function in the context of organ physiology. We have generated mice carrying a conditional Serca2flox allele which allows disruption of the Serca2 gene in an organ-specific and/or inducible manner. The model was tested by mating Serca2flox mice with MLC-2vwt/Cre mice and with αMHC-Cre transgenic mice. In heterozygous Serca2wt/flox MLC-2vwt/Cre mice, the expression of SERCA2a and SERCA2b proteins were reduced in the heart and slow skeletal muscle, in accordance with the expression pattern of the MLC-2v gene. In Serca2flox/flox Tg(αMHC-Cre) embryos with early homozygous cardiac Serca2 disruption, normal embryonic development and yolk sac circulation was maintained up to at least embryonic stage E10.5. The Serca2flox mouse is the first murine conditional gene disruption model for the SERCA family of Ca2+ ATPases, and should be a powerful tool for investigating specific physiological roles of SERCA2 function in a range of tissues and organs in vivo both in adult and embryonic stages.
doi:10.1016/j.ceca.2009.07.004
PMCID: PMC4313567  PMID: 19692123
Serca2; Calcium ATPase; Endoplasmic reticulum; Sarcoplasmic reticulum; Flox; Transgenic mouse
2.  Stem Cell Models of Cardiac Development and Disease 
The last few years have witnessed remarkable advances in stem cell biology and human genetics, and we have arrived at an era where patient-specific cell and tissue models are now practical. The recent identification of cardiovascular progenitor cells, as well as the identification of genetic variants underlying congenital heart disorders and adult disease, opens the door to the development of human models of human cardiovascular disease. We review the current understanding of the contribution of progenitor cells to cardiogenesis, and we outline how pluripotent stem cells can be applied for the modeling of cardiovascular disorders of genetic origin. A key challenge will be to implement these models in an efficient manner to develop a molecular understanding of how genes lead to disease and to screen for genes and drugs that modify the disease process.
doi:10.1146/annurev-cellbio-100109-103948
PMCID: PMC3955884  PMID: 20604707
cardiovascular disease; congenital heart disease; cardiac development; stem cells; genetics
3.  Modeling the mitochondrial cardiomyopathy of Barth syndrome with iPSC and heart-on-chip technologies 
Nature medicine  2014;20(6):616-623.
Studying monogenic mitochondrial cardiomyopathies may yield insights into mitochondrial roles in cardiac development and disease. Here, we combine patient-derived and genetically engineered iPSCs with tissue engineering to elucidate the pathophysiology underlying the cardiomyopathy of Barth syndrome (BTHS), a mitochondrial disorder caused by mutation of the gene Tafazzin (TAZ). Using BTHS iPSC-derived cardiomyocytes (iPSC-CMs), we defined metabolic, structural, and functional abnormalities associated with TAZ mutation. BTHS iPSC-CMs assembled sparse and irregular sarcomeres, and engineered BTHS “heart on chip” tissues contracted weakly. Gene replacement and genome editing demonstrated that TAZ mutation is necessary and sufficient for these phenotypes. Sarcomere assembly and myocardial contraction abnormalities occurred in the context of normal whole cell ATP levels. Excess levels of reactive oxygen species mechanistically linked TAZ mutation to impaired cardiomyocyte function. Our study provides new insights into the pathogenesis of Barth syndrome, suggests new treatment strategies, and advances iPSC-based in vitro modeling of cardiomyopathy.
doi:10.1038/nm.3545
PMCID: PMC4172922  PMID: 24813252
4.  N-cadherin prevents the premature differentiation of anterior heart field progenitors in the pharyngeal mesodermal microenvironment 
Cell Research  2014;24(12):1420-1432.
The cardiac progenitor cells (CPCs) in the anterior heart field (AHF) are located in the pharyngeal mesoderm (PM), where they expand, migrate and eventually differentiate into major cell types found in the heart, including cardiomyocytes. The mechanisms by which these progenitors are able to expand within the PM microenvironment without premature differentiation remain largely unknown. Through in silico data mining, genetic loss-of-function studies, and in vivo genetic rescue studies, we identified N-cadherin and interaction with canonical Wnt signals as a critical component of the microenvironment that facilitates the expansion of AHF-CPCs in the PM. CPCs in N-cadherin mutant embryos were observed to be less proliferative and undergo premature differentiation in the PM. Notably, the phenotype of N-cadherin deficiency could be partially rescued by activating Wnt signaling, suggesting a delicate functional interaction between the adhesion role of N-cadherin and Wnt signaling in the early PM microenvironment. This study suggests a new mechanism for the early renewal of AHF progenitors where N-cadherin provides additional adhesion for progenitor cells in the PM, thereby allowing Wnt paracrine signals to expand the cells without premature differentiation.
doi:10.1038/cr.2014.142
PMCID: PMC4260345  PMID: 25367124
N-cadherin; anterior heart field; cardiac progenitor cells; premature differentiation; Wnt signaling; microenvironment
5.  The Years of the Monkey 
Cell Research  2013;23(10):1161-1162.
The fact that mammals are diploid sets a barrier to rapidly understand the function of non-coding and coding genes in the genome. Recently, Yang et al. reported successful derivation of monkey haploid embryonic stem cells from parthenotes, which provide an effective platform for studying mammalian gene function and enable reverse genetic screening of genes for recessive phenotypes in monkeys.
doi:10.1038/cr.2013.111
PMCID: PMC3790233  PMID: 23958583
6.  Manipulation of a VEGF-Notch signaling circuit drives formation of functional vascular endothelial progenitors from human pluripotent stem cells 
Cell Research  2014;24(7):820-841.
Human pluripotent stem cell (hPSC)-derived endothelial lineage cells constitutes a promising source for therapeutic revascularization, but progress in this arena has been hampered by a lack of clinically-scalable differentiation protocols and inefficient formation of a functional vessel network integrating with the host circulation upon transplantation. Using a human embryonic stem cell reporter cell line, where green fluorescent protein expression is driven by an endothelial cell-specific VE-cadherin (VEC) promoter, we screened for > 60 bioactive small molecules that would promote endothelial differentiation, and found that administration of BMP4 and a GSK-3β inhibitor in an early phase and treatment with VEGF-A and inhibition of the Notch signaling pathway in a later phase led to efficient differentiation of hPSCs to the endothelial lineage within six days. This sequential approach generated > 50% conversion of hPSCs to endothelial cells (ECs), specifically VEC+CD31+CD34+CD14−KDRhigh endothelial progenitors (EPs) that exhibited higher angiogenic and clonogenic proliferation potential among endothelial lineage cells. Pharmaceutical inhibition or genetical knockdown of Notch signaling, in combination with VEGF-A treatment, resulted in efficient formation of EPs via KDR+ mesodermal precursors and blockade of the conversion of EPs to mature ECs. The generated EPs successfully formed functional capillary vessels in vivo with anastomosis to the host vessels when transplanted into immunocompromised mice. Manipulation of this VEGF-A-Notch signaling circuit in our protocol leads to rapid large-scale production of the hPSC-derived EPs by 12- to 20-fold vs current methods, which may serve as an attractive cell population for regenerative vascularization with superior vessel forming capability compared to mature ECs.
doi:10.1038/cr.2014.59
PMCID: PMC4085760  PMID: 24810299
embryonic stem cell; endothelial progenitor; Notch signaling; VEGF
7.  Modified mRNA directs the fate of heart progenitor cells and induces vascular regeneration after myocardial infarction 
Nature biotechnology  2013;31(10):898-907.
In a cell-free approach to regenerative therapeutics, transient application of paracrine factors in vivo could be used to alter the behavior and fate of progenitor cells to achieve sustained clinical benefits. Here we show that intramyocardial injection of synthetic modified RNA (modRNA) encoding human vascular endothelial growth factor-A (VEGF-A) resulted in the expansion and directed differentiation of endogenous heart progenitors in a murine myocardial infarction model. VEGF-A modRNA markedly improved heart function and enhanced long-term survival of recipients. This improvement was in part due to mobilization of epicardial progenitor cells and redirection of their differentiation toward cardiovascular cell types. Direct in vivo comparison with DNA vectors, and temporal control with VEGF inhibitors, documented the markedly increased efficacy of pulse-like delivery of VEGF-A. Our results suggest that modRNA is a versatile approach for expressing paracrine factors as cell fate switches to control progenitor cell fate and thereby enhance long term organ repair.
doi:10.1038/nbt.2682
PMCID: PMC4058317  PMID: 24013197
8.  The Muscle Ankyrin Repeat Proteins CARP, Ankrd2, and DARP Are Not Essential for Normal Cardiac Development and Function at Basal Conditions and in Response to Pressure Overload 
PLoS ONE  2014;9(4):e93638.
Ankrd1/CARP, Ankrd2/Arpp, and Ankrd23/DARP belong to a family of stress inducible ankyrin repeat proteins expressed in striated muscle (MARPs). The MARPs are homologous in structure and localized in the nucleus where they negatively regulate gene expression as well as in the sarcomeric I-band, where they are thought to be involved in mechanosensing. Together with their strong induction during cardiac disease and the identification of causative Ankrd1 gene mutations in cardiomyopathy patients, this suggests their important roles in cardiac development, function, and disease. To determine the functional role of MARPs in vivo, we studied knockout (KO) mice of each of the three family members. Single KO mice were viable and had no apparent cardiac phenotype. We therefore hypothesized that the three highly homologous MARP proteins may have redundant functions in the heart and studied double and triple MARP KO mice. Unexpectedly, MARP triple KO mice were viable and had normal cardiac function both at basal levels and in response to mechanical pressure overload induced by transverse aortic constriction as assessed by echocardiography and hemodynamic studies. Thus, CARP, Ankrd2, and DARP are not essential for normal cardiac development and function at basal conditions and in response to mechanical pressure overload.
doi:10.1371/journal.pone.0093638
PMCID: PMC3988038  PMID: 24736439
9.  Pregenerative medicine: developmental paradigms in the biology of cardiovascular regeneration 
The ability to create new functional cardiomyocytes is the holy grail of cardiac regenerative medicine. From studies using model organisms, new insights into the fundamental pathways that drive heart muscle regeneration have begun to arise as well as a growing knowledge of the distinct families of multipotent cardiovascular progenitors that generate diverse lineages during heart development. In this Review, we highlight this intersection of the “pregenerative” biology of heart progenitor cells and heart regeneration and discuss the longer term challenges and opportunities in moving toward a therapeutic goal of regenerative cardiovascular medicine.
doi:10.1172/JCI40820
PMCID: PMC2798699  PMID: 20051633
10.  Functional Differences in Engineered Myocardium from Embryonic Stem Cell-Derived versus Neonatal Cardiomyocytes 
Stem Cell Reports  2013;1(5):387-396.
Summary
Stem cell-derived cardiomyocytes represent unique tools for cell- and tissue-based regenerative therapies, drug discovery and safety, and studies of fundamental heart-failure mechanisms. However, the degree to which stem cell-derived cardiomyocytes compare to mature cardiomyocytes is often debated. We reasoned that physiological metrics of engineered cardiac tissues offer a means of comparison. We built laminar myocardium engineered from cardiomyocytes that were differentiated from mouse embryonic stem cell-derived cardiac progenitors or harvested directly from neonatal mouse ventricles, and compared their anatomy and physiology in vitro. Tissues assembled from progenitor-derived myocytes and neonate myocytes demonstrated similar cytoskeletal architectures but different gap junction organization and electromechanical properties. Progenitor-derived myocardium had significantly less contractile stress and slower longitudinal conduction velocity than neonate-derived myocardium, indicating that the developmental state of the cardiomyocytes affects the electromechanical function of the resultant engineered tissue. These data suggest a need to establish performance metrics for future stem cell applications.
Graphical Abstract
Highlights
•Engineered myocardium was compared with progenitor-derived and neonatal myocytes•Progenitor-derived and neonatal myocytes had similar sarcomere and actin structure•Progenitor-derived tissue had significantly slower conduction velocity than neonate•Progenitor-derived tissue generated significantly less contractile stress than neonate
Parker and colleagues engineered myocardium from cardiomyocytes either differentiated from mouse embryonic stem cell-derived cardiac progenitors or harvested directly from neonatal mouse ventricles, and compared their anatomy and physiology in vitro. Results show the ability to build structurally similar tissues, but the progenitor-derived myocardium had significantly lower conduction velocity and contractile stress generation than the neonatal myocardium.
doi:10.1016/j.stemcr.2013.10.004
PMCID: PMC3841251  PMID: 24286027
11.  In vivo reprogramming for heart disease 
Cell Research  2012;22(11):1521-1523.
The term “lineage reprogramming” is typically used to describe the conversion of one differentiated somatic cell type into another without transit through a pluripotent intermediate. Two recent reports in Nature demonstrate that such a conversion can be achieved in the heart in situ, and suggest a novel, regenerative approach for the development of cardiac therapeutics.
doi:10.1038/cr.2012.101
PMCID: PMC3494388  PMID: 22751090
12.  Driving vascular endothelial cell fate of human multipotent Isl1+ heart progenitors with VEGF modified mRNA 
Cell Research  2013;23(10):1172-1186.
Distinct families of multipotent heart progenitors play a central role in the generation of diverse cardiac, smooth muscle and endothelial cell lineages during mammalian cardiogenesis. The identification of precise paracrine signals that drive the cell-fate decision of these multipotent progenitors, and the development of novel approaches to deliver these signals in vivo, are critical steps towards unlocking their regenerative therapeutic potential. Herein, we have identified a family of human cardiac endothelial intermediates located in outflow tract of the early human fetal hearts (OFT-ECs), characterized by coexpression of Isl1 and CD144/vWF. By comparing angiocrine factors expressed by the human OFT-ECs and non-cardiac ECs, vascular endothelial growth factor (VEGF)-A was identified as the most abundantly expressed factor, and clonal assays documented its ability to drive endothelial specification of human embryonic stem cell (ESC)-derived Isl1+ progenitors in a VEGF receptor-dependent manner. Human Isl1-ECs (endothelial cells differentiated from hESC-derived ISL1+ progenitors) resemble OFT-ECs in terms of expression of the cardiac endothelial progenitor- and endocardial cell-specific genes, confirming their organ specificity. To determine whether VEGF-A might serve as an in vivo cell-fate switch for human ESC-derived Isl1-ECs, we established a novel approach using chemically modified mRNA as a platform for transient, yet highly efficient expression of paracrine factors in cardiovascular progenitors. Overexpression of VEGF-A promotes not only the endothelial specification but also engraftment, proliferation and survival (reduced apoptosis) of the human Isl1+ progenitors in vivo. The large-scale derivation of cardiac-specific human Isl1-ECs from human pluripotent stem cells, coupled with the ability to drive endothelial specification, engraftment, and survival following transplantation, suggest a novel strategy for vascular regeneration in the heart.
doi:10.1038/cr.2013.112
PMCID: PMC3790234  PMID: 24018375
cardiovascular progenitors; endothelial cells; Isl1; mRNA; VEGF-A
13.  Telethonin deficiency is associated with maladaptation to biomechanical stress in the mammalian heart 
Circulation research  2011;109(7):758-769.
Rationale
Telethonin (also known as titin-cap or t-cap) is a 19 kDa Z-disk protein with a unique β-sheet structure, hypothesized to assemble in a palindromic way with the N-terminal portion of titin and to constitute a signalosome participating in the process of cardio-mechanosensing. In addition, a variety of telethonin mutations are associated with the development of several different diseases; however, little is known about the underlying molecular mechanisms and telethonin’s in vivo function.
Objective
Here we aim to investigate the role of telethonin in vivo and to identify molecular mechanisms underlying disease as a result of its mutation.
Methods and Results
By using a variety of different genetically altered animal models and biophysical experiments we show that, contrary to previous views, telethonin is not an indispensable component of the titin-anchoring system, nor is deletion of the gene or cardiac specific overexpression associated with a spontaneous cardiac phenotype. Rather, additional titin-anchorage sites, such as actin-titin crosslinks via α-actinin, are sufficient to maintain Z-disk stability despite the loss of telethonin. We demonstrate that a main novel function of telethonin is to modulate the turnover of the pro-apoptotic tumor suppressor p53 after biomechanical stress in the nuclear compartment, thus linking telethonin, a protein well known to be present at the Z-disk, directly to apoptosis (“mechanoptosis”). In addition, loss of telethonin mRNA and nuclear accumulation of this protein is associated with human heart failure, an effect which may contribute to enhanced rates of apoptosis found in these hearts.
Conclusions
Telethonin knockout mice do not reveal defective heart development or heart function under basal conditions, but develop heart failure following biomechanical stress, owing at least in part to apoptosis of cardiomyocytes, an effect which may also play a role in human heart failure.
doi:10.1161/CIRCRESAHA.111.245787
PMCID: PMC3664427  PMID: 21799151
Genetics; Mechanosensation; Mechanotransduction; Cardiomyopathy; Heart failure
14.  Lost and found: cardiac stem cell therapy revisited 
Journal of Clinical Investigation  2006;116(7):1838-1840.
Several clinical trials of bone marrow stem cell therapy for myocardial infarction are ongoing, but the mechanistic basis for any potential therapeutic effect is currently unclear. A growing body of evidence suggests that the potential improvement in cardiac function is largely independent of cardiac muscle regeneration. A study by Fazel et al. in this issue of the JCI provides evidence that bone marrow–derived c-kit+ cells can lead to an improvement in cardiac function in mutant hypomorphic c-kit mice that is independent of transdifferentiation into either cardiac muscle or endothelial cells, but rather is associated with the release of angiogenic cytokines and associated neovascularization in the infarct border zone (see the related article beginning on page 1865). These findings suggest the potential therapeutic effect of specific paracrine pathways for angiogenesis in improving cardiac function in the injured heart.
doi:10.1172/JCI29050
PMCID: PMC1483159  PMID: 16823485
15.  Conduction Slowing and Sudden Arrhythmic Death in Mice With Cardiac-Restricted Inactivation of Connexin43 
Circulation research  2001;88(3):333-339.
Cardiac arrhythmia is a common and often lethal manifestation of many forms of heart disease. Gap junction remodeling has been postulated to contribute to the increased propensity for arrhythmogenesis in diseased myocardium, although a causative role in vivo remains speculative. By generating mice with cardiac-restricted knockout of connexin43 (Cx43), we have circumvented the perinatal lethal developmental defect associated with germline inactivation of this gap junction channel gene and uncovered an essential role for Cx43 in the maintenance of electrical stability. Mice with cardiac-specific loss of Cx43 have normal heart structure and contractile function, and yet they uniformly (28 of 28 conditional Cx43 knockout mice observed) develop sudden cardiac death from spontaneous ventricular arrhythmias by 2 months of age. Optical mapping of the epicardial electrical activation pattern in Cx43 conditional knockout mice revealed that ventricular conduction velocity was significantly slowed by up to 55% in the transverse direction and 42% in the longitudinal direction, resulting in an increase in anisotropic ratio compared with control littermates (2.1±0.13 versus 1.66±0.06; P<0.01). This novel genetic murine model of primary sudden cardiac death defines gap junctional abnormalities as a key molecular feature of the arrhythmogenic substrate.
PMCID: PMC3630465  PMID: 11179202
gap junction; connexin43; arrhythmia; conduction
16.  Genotype, phenotype: upstairs, downstairs in the family of cardiomyopathies 
Journal of Clinical Investigation  2003;111(2):175-178.
doi:10.1172/JCI200317612
PMCID: PMC151886  PMID: 12531871
17.  Muscle LIM protein in heart failure 
Experimental & Clinical Cardiology  2002;7(2-3):104-105.
Z-line protein have important structural functions. Recent publications point to additional, previously unexpected functions and new views are now emerging. Z-line proteins are involved in important intra- and intercellular signalling pathways. They translocate into the nucleus, they interact with a variety of signalling molecules including kinases and transcription factors, and they have the ability to form macromolecular protein complexes indicating furthermore their multifuntionality. The muscle LIM protein (MLP) is muscle specific, and is expressed and located at the z-line. MLP’s physiological role at the z-line and in the nucleus may be better understood by precise investigations of specific mutations in specific domains of this protein.
PMCID: PMC2719181  PMID: 19649232
Cardiomyopathy; Heart failure; Muscle LIM protein; Z-line proteins
18.  Mixed signals in heart failure: cancer rules 
doi:10.1172/JCI15380
PMCID: PMC150934  PMID: 11927610
19.  Highly efficient derivation of ventricular cardiomyocytes from induced pluripotent stem cells with a distinct epigenetic signature 
Cell Research  2011;22(1):142-154.
Cardiomyocytes derived from pluripotent stem cells can be applied in drug testing, disease modeling and cell-based therapy. However, without procardiogenic growth factors, the efficiency of cardiomyogenesis from pluripotent stem cells is usually low and the resulting cardiomyocyte population is heterogeneous. Here, we demonstrate that induced pluripotent stem cells (iPSCs) can be derived from murine ventricular myocytes (VMs), and consistent with other reports of iPSCs derived from various somatic cell types, VM-derived iPSCs (ViPSCs) exhibit a markedly higher propensity to spontaneously differentiate into beating cardiomyocytes as compared to genetically matched embryonic stem cells (ESCs) or iPSCs derived from tail-tip fibroblasts. Strikingly, the majority of ViPSC-derived cardiomyocytes display a ventricular phenotype. The enhanced ventricular myogenesis in ViPSCs is mediated via increased numbers of cardiovascular progenitors at early stages of differentiation. In order to investigate the mechanism of enhanced ventricular myogenesis from ViPSCs, we performed global gene expression and DNA methylation analysis, which revealed a distinct epigenetic signature that may be involved in specifying the VM fate in pluripotent stem cells.
doi:10.1038/cr.2011.171
PMCID: PMC3351933  PMID: 22064699
induced pluripotent stem cells; ventricular cardiomyocyte; regenerative medicine; epigenetic memory
20.  Suppressor of cytokine signaling-3 is a biomechanical stress–inducible gene that suppresses gp130-mediated cardiac myocyte hypertrophy and survival pathways 
Journal of Clinical Investigation  2001;108(10):1459-1467.
The gp130 cytokine receptor activates a cardiomyocyte survival pathway during the transition to heart failure following the biomechanical stress of pressure overload. Although gp130 activation is observed transiently during transverse aortic constriction (TAC), its mechanism of inactivation is largely unknown in cardiomyocytes. We show here that suppressor of cytokine signaling 3 (SOCS3), an intrinsic inhibitor of JAK, shows biphasic induction in response to TAC. The induction of SOCS3 was closely correlated with STAT3 phosphorylation, as well as the activation of an embryonic gene program, suggesting that cardiac gp130-JAK signaling is precisely controlled by this endogenous suppressor. In addition to its cytoprotective action, gp130-dependent signaling induces cardiomyocyte hypertrophy. Adenovirus-mediated gene transfer of SOCS3 to ventricular cardiomyocytes completely suppressed both hypertrophy and antiapoptotic phenotypes induced by leukemia inhibitory factor (LIF). To our knowledge, this is the first clear evidence that these two separate cardiomyocyte phenotypes induced by gp130 activation lie downstream of JAK. Three independent signaling pathways, STAT3, MEK1-ERK1/2, and AKT activation, that are coinduced by LIF stimulation were completely suppressed by SOCS3 overexpression. We conclude that SOCS3 is a mechanical stress–inducible gene in cardiac muscle cells and that it directly modulates stress-induced gp130 cytokine receptor signaling as the key molecular switch for a negative feedback circuit for both myocyte hypertrophy and survival.
PMCID: PMC209425  PMID: 11714737
22.  Ablation of Nkx2-5 at mid-embryonic stage results in premature lethality and cardiac malformation 
Cardiovascular Research  2011;91(2):289-299.
Aims
Human congenital heart disease linked to mutations in the homeobox transcription factor, NKX2-5, is characterized by cardiac anomalies, including atrial and ventricular septal defects as well as conduction and occasional defects in contractility. In the mouse, homozygous germline deletion of Nkx2-5 gene results in death around E10.5. It is, however, not established whether Nkx2-5 is necessary for cardiac development beyond this embryonic stage. Because human NKX2-5 mutations are related to septum secundum type atrial septal defects (ASD), we hypothesized that Nkx2-5 deficiency during the processes of septum secundum formation may cause cardiac anomalies; thus, we analysed mice with tamoxifen-inducible Nkx2-5 ablation beginning at E12.5 when the septum secundum starts to develop.
Methods and results
Using tamoxifen-inducible Nkx2-5 gene-targeted mice, this study demonstrates that Nkx2-5 ablation beginning at E12.5 results in embryonic death by E17.5. Analysis of mutant embryos at E16.5 shows arrhythmias, contraction defects, and cardiac malformations, including ASD. Quantitative measurements using serial section histology and three-dimensional reconstruction demonstrate growth retardation of the septum secundum and enlarged foramen ovale in Nkx2-5-ablated embryos. Functional cardiac defects may be attributed to abnormal expression of transcripts critical for conduction and contraction, including cardiac voltage-gated Na+ channel pore-forming α-subunit (Nav1.5-α), gap junction protein connexin40, cardiac myosin light chain kinase, and sarcolipin within 4 days after tamoxifen injection.
Conclusion
Nkx2-5 is necessary for survival after the mid-embryonic stage for cardiac function and formation by regulating the expression of its downstream target genes.
doi:10.1093/cvr/cvr037
PMCID: PMC3125071  PMID: 21285290
Genetics; Heart defects; Congenital; Conduction; Contractility
23.  Alchemy and the New Age of Cardiac Muscle Cell Biology 
PLoS Biology  2005;3(4):e131.
Several studies have claimed to identify cardiac stem cells. But what criteria do such cells have to fulfil before we can be confident about their true potential?
doi:10.1371/journal.pbio.0030131
PMCID: PMC1074813  PMID: 15819607
24.  Cardiac origin of smooth muscle cells in the inflow tract 
Multipotent Isl1+ heart progenitors give rise to three major cardiovascular cell types; cardiac, smooth muscle, and endothelial cells, and play a pivotal role in lineage diversification during cardiogenesis. A critical question is pinpointing when this cardiac-vascular lineage decision is made, and how this plasticity serves to coordinate cardiac chamber and vessel growth. The posterior domain of the Isl1-positive second heart field contributes to the SLN-positive atrial myocardium and myocardial sleeves in the cardiac inflow tract, where myocardial and vascular smooth muscle layers form anatomical and functional continuity. Herein, using a new atrial specific SLN-Cre knockin mouse line, we report that an Isl1+/SLN+ transient cell population contributes to cardiac as well as smooth muscle cells at the heart-vessel junction in cardiac inflow tract. The Isl1+/SLN+ cells are capable of giving rise to cardiac and smooth muscle cells until late gestational stages. These data suggest that the cardiac and smooth muscle cells in the cardiac inflow tract share a common developmental origin.
doi:10.1016/j.yjmcc.2010.10.009
PMCID: PMC3031779  PMID: 20974149
cardiogenesis; myogenic progenitor; smooth muscle; great vessel; plasticity
25.  Generation of Functional Ventricular Heart Muscle from Mouse Ventricular Progenitor Cells 
Science (New York, N.Y.)  2009;326(5951):426-429.
The mammalian heart is formed from distinct sets of first (FHF) and second (SHF) heart field progenitors. Although multipotent progenitors have been previously shown to give rise to cardiomyocytes, smooth muscle, and endothelial cells, the mechanism governing the generation of large numbers of differentiated progeny remains poorly understood. Herein, we have employed a two-colored fluorescent reporter system to isolate FHF and SHF progenitors from developing mouse embryos and embryonic stem cells. Genome wide profiling of coding and non-coding transcripts revealed distinct molecular signatures of these progenitor populations. We further identify a committed ventricular progenitor cell in the Islet 1 lineage that is capable of in vitro expansion, differentiation, and assembly into functional ventricular muscle tissue. These results represent a novel approach combining tissue-engineering with stem cell biology for the generation of functional ventricular tissue.
doi:10.1126/science.1177350
PMCID: PMC2895998  PMID: 19833966

Results 1-25 (45)