Cause Of Congenital Heart Disease Research Articles

Ethanol and Its Metabolites Induce Histone Lysine 9 Acetylation and an Alteration of the Expression of Heart Development-Related Genes in Cardiac Progenitor Cells

Alcohol exposure during pregnancy may cause congenital heart disease (CHD), but the underlying mechanisms are not clear. Recent evidence suggests that ethanol and its metabolites can selectively increase histone H3 acetylation at lysine 9 (H3AcK9) residue in rat hepatocytes. This may be a mechanism by which ethanol alters gene expression. The goal of current study is to investigate the effect of ethanol and its metabolites on H3AcK9 acetylation and the mRNA expression of heart development-related genes (GATA4, Mef2c, and Tbx5) in cardiac progenitor cells. We used mitochondrial activity (MTT) assay to assess the viability of cardiac progenitor cells. Western blotting and real-time PCR were employed to determine H3AcK9 acetylation and gene expression. Low levels of ethanol (50mM), acetaldehyde (4mM), and acetate (4mM) had no effect on cell proliferation. However, high concentrations of ethanol (200mM), acetaldehyde (12mM), and acetate (16mM) reduced cell viability by 30%, respectively (P<0.05). Low levels of ethanol and acetate increased the acetylation of H3 lysine 9 by 2.4- and 2.2-fold, respectively (P<0.05), but did not significantly change the expression of the heart development-related genes. High concentrations of ethanol and acetate increased H3 lysine 9 acetylation by 5.3- and 5.6-fold, respectively (P<0.05). Moreover, high levels of ethanol and acetate significantly augmented the expression of GATA4 and Mef2c. Conversely, acetaldehyde (4 or 12mM) had little effect on H3 lysine 9 acetylation or the expression of the heart development-related genes. Our studies demonstrate that high levels of ethanol or its metabolites induce H3AcK9 acetylation and impair cardiac progenitor cells. The altered histone H3 acetylation at lysine 9 has an important impact on the expression of the heart development-related genes, which may be one of the mechanisms underlying the alcohol-induced CHD.

PATHOGENIC MECHANISMS OF CONGENITAL HEART DISEASE

Congenital heart disease (CHD) is the most common type of birth defect. Despite the many advances in the understanding of cardiac development and the identification of many genes related to cardiac development, the fundamental etiology for the majority of cases of congenital heart disease remains unknown. This review summarizes normal cardiac development, and outlines the recent discoveries of the genetic causes of congenital heart disease and provides possible strategies for exploring genetic causes.

The Multiple Phases and Faces of Wnt Signaling During Cardiac Differentiation and Development

Understanding heart development on a molecular level is a prerequisite for uncovering the causes of congenital heart diseases. Therapeutic approaches that try to enhance cardiac regeneration or that involve the differentiation of resident cardiac progenitor cells or patient-specific induced pluripotent stem cells will also benefit tremendously from this knowledge. Wnt proteins have been shown to play multiple roles during cardiac differentiation and development. They are extracellular growth factors that activate different intracellular signaling branches. Here, we summarize our current understanding of how these factors affect different aspects of cardiogenesis, starting from early specification of cardiac progenitors and continuing on to later developmental steps, such as morphogenetic processes, valve formation, and establishment of the conduction system.

The National Heart, Lung, and Blood Institute Bench to Bassinet Program: A New Paradigm for Translational Research

Congenital heart disease (CHD) is the most common birth defect and is a significant source of morbidity and mortality in children. Despite considerable recent progress in the clinical arena, we have a lot yet to learn about the causes of CHD and the genetic modifiers of clinical outcome. It is our

Chromosomal Anomalies and Congenital Heart Disease in Mysore, South India

Congenital heart disease (CHD) is the most common form of human birth defects accounting for about 30% of the total anomalies. The prevalence of CHD worldwide is found to range between 1.0 - 150/ 1000 live births. The causes for CHD can be categorized into three major groups such as, chromosomal (0.4. - 26.8%), single gene disorders (10-15%) and multiple factors (85-90%). Here we report the association of chromosomal variations with CHD in Mysore. A total of 192 confirmed CHD cases were considered for the present study whose age ranged from 1 day to 23 years. After written consent was obtained from the family members, 136 CHD patients were subjected for conventional cytogenetic studies and some of them for FISH analysis. Of these, 18 patients were with numerical abnormalities, 3 patients with structural abnormalities, one patient with both numerical and structural abnormalities and remaining 114 patients with normal chromosomes. Thus, the present findings are the maiden report from Mysore, which have contributed richly towards the association of chromosomal anomalies with CHD and pointing out chromosome 9 a possible killer chromosome for the cause of CHD.

Hairy-related transcription factor 2 is not potentially related to congenital heart disease in Chinese patients

Congenital heart disease (CHD) is the malformation of the heart during embryonic development, contributing to the inadequate function of the heart. A recently suggested gene hairy-related transcription factor 2 (HEY2), is an important determinant of mammalian heart development and functions thereby. We had preformed a direct sequencing within 768 Chinese CHD patients in the HEY2 gene. However, we did not reveal any diagnostic alterations in the coding regions by direct sequencing in HEY2, nevertheless this work expands our knowledge of the causes of CHD in the other way.

Chondroitin sulfate expression is required for cardiac atrioventricular canal formation

Defects in cardiac valvulogenesis are a common cause of congenital heart disease, and the study of this process promises to provide mechanistic insights and lead to novel therapeutics. Normal valve development involves multiple signaling pathways, and recently roles have been identified for extracellular matrix components, including glycosaminoglycans. We, therefore, explored the role of the glycosaminoglycan chondroitin sulfate during zebrafish cardiac development. Beginning at 33 hr, there is a distinct zone of chondroitin sulfate expression in the atrioventricular (AV) boundary, in the cardiac jelly between the endocardium and myocardium. This expression is both spatially and temporally restricted, and is undetectable after 48 hr. Chemical as well as genetic inhibition of chondroitin synthesis results in AV canal (AVC) defects, including loss of the atrioventricular constriction, blood regurgitation, and failure of circulation. Lack of chondroitin disrupts a marker of cell migration, results in a loss of myocardial and endothelial markers of valvulogenesis, and misregulates bone morphogenetic protein expression, supporting an early role in AVC development. In summary, we have defined a requirement for chondroitin sulfate expression in the normal patterning of the AV boundary, suggesting that this component of the cardiac jelly provides a necessary signal in this critical transition in vertebrate cardiogenesis.

Molecular mechanisms of congenital heart disease

Congenital heart disease (CHD) is the most common type of birth defect. Despite the many advances in our understanding of cardiac development and many genes related to cardiac development identified, the fundamental etiology for the majority of cases of congenital heart disease remains unknown. This review summarizes normal cardiac development, outlines the recent discoveries of the genetic causes of CHD, and provides possible strategies for exploring them. CHD is a multifactorial complex disease, with environmental and genetic factors playing important roles. A number of causative genes of selected congenital heart defects and genetic syndromes have been found. The molecular mechanisms of CHD may include mutations in components of the cardiac gene network, altered haemodynamics, regulatory pathway of cardiac genes, micro-RNA dysfunction, epigenetics, adult congenital heart diseases, and so on. The molecular basis of CHD is an exciting and rapidly evolving field. The continuing advances in the understanding of the molecular mechanisms of CHD will hopefully result in improved genetic counseling and care of affected individuals and their families.

GATA6 mutations cause human cardiac outflow tract defects by disrupting semaphorin-plexin signaling

Congenital heart diseases (CHD) occur in nearly 1% of all live births and are the major cause of infant mortality and morbidity. Although an improved understanding of the genetic causes of CHD would provide insight into the underlying pathobiology, the genetic etiology of most CHD remains unknown. Here we show that mutations in the gene encoding the transcription factor GATA6 cause CHD characteristic of a severe form of cardiac outflow tract (OFT) defect, namely persistent truncus arteriosus (PTA). Two different GATA6 mutations were identified by systematic genetic analysis using DNA from patients with PTA. Genes encoding the neurovascular guiding molecule semaphorin 3C (SEMA3C) and its receptor plexin A2 (PLXNA2) appear to be regulated directly by GATA6, and both GATA6 mutant proteins failed to transactivate these genes. Transgenic analysis further suggests that, in the developing heart, the expression of SEMA3C in the OFT/subpulmonary myocardium and PLXNA2 in the cardiac neural crest contributing to the OFT is dependent on GATA transcription factors. Together, our data implicate mutations in GATA6 as genetic causes of CHD involving OFT development, as a result of the disruption of the direct regulation of semaphorin-plexin signaling.

S06-01 Cardiac transcription factors in development and disease

The homeodomain factor Nkx2-5 is expressed in cardiac progenitor cells of the first and second heart fields, and in differentiating cardiomyocytes and conduction cells. NKX2-5 mutations cause congenital heart disease (CHD) and conduction disease (CD) in humans. Nkx2-5 acts as both a repressor and an activator, and one of its early roles is to repress, through a negative feedback loop, the expression of the Bmp2 gene, which encodes one of the upstream inducers of cardiogenesis and is itself a repressor of cardiac progenitor cell proliferation. In this way Nkx2-5 orchestrates a transition between a period of cardiac induction and one of heart progenitor cell expansion and deployment. We have also studied the Nkx2-5 transcriptional cofactor, Tbx20, a member of the T-box transcription factor family, and shown that Tbx20 mutations also cause CHD as well as adult-onset dilated cardiomyopathy (DCM). The T-box DNA binding domain of Tbx20 has unique biophysical properties, with its tertiary hydrophobic interactions existing in a state of dynamic equilibrium akin to a molten globule, a state that may facilitate formation and/or stability of transcriptional complexes. Gain-of-function mutations can exacerbate this state. These studies address CHD at the molecular, cellular and organ level and contribute to an understanding of CHD origins and patient management.

Progress in the genetic cause of congenital heart disease

先天性心脏病(先心病)是人类最常见的出生缺陷之一,其真正的病因和发病机制目前依然不明确.由于心脏发育是一个多细胞、多基因参与调控的复杂事件,通过基因敲除技术构建动物模型,对某些先心病致病基因的突变检测,目前已发现了相当一部分先心病的相关致病基因及发病机制.某些心脏发育基因敲除动物模型可表现心脏畸形,但在相关先心病患者中却未能检测出该基因的异常.该文对目前已报道在人类先心病中明确检测到基因异常的相关致病基因作一综述,尤其集中在遗传综合征、家族性先心病,以全面理解先心病的遗传学机制。

Noonan syndrome cardiac defects are caused by PTPN11 acting in endocardium to enhance endocardial-mesenchymal transformation

Noonan syndrome (NS), the most common single-gene cause of congenital heart disease, is an autosomal dominant disorder that also features proportionate short stature, facial abnormalities, and an increased risk of myeloproliferative disease. Germline-activating mutations in PTPN11, which encodes the protein tyrosine phosphatase SHP2, cause about half of NS cases; other causative alleles include KRAS, SOS1, and RAF1 mutants. We showed previously that knock-in mice bearing the NS mutant Ptpn11(D61G) on a mixed 129S4/SvJae X C57BL6/J background exhibit all major NS features, including a variety of cardiac defects, with variable penetrance. However, the cellular and molecular mechanisms underlying NS cardiac defects and whether genetic background and/or the specific NS mutation contribute to the NS phenotype remained unclear. Here, using an inducible knock-in approach, we show that all cardiac defects in NS result from mutant Shp2 expression in the endocardium, not in the myocardium or neural crest. Furthermore, the penetrance of NS defects is affected by genetic background and the specific Ptpn11 allele. Finally, ex vivo assays and pharmacological approaches show that NS mutants cause cardiac valve defects by increasing Erk MAPK activation, probably downstream of ErbB family receptor tyrosine kinases, extending the interval during which cardiac endocardial cells undergo endocardial-mesenchymal transformation. Our data provide a mechanistic underpinning for the cardiac defects in this disorder.

Abstract 3407: The Transcriptional Mediator Complex Is Essential For Cardiac Valve Formation

The genetic causes of congenital heart diseases especially cardiac valve disorders are mostly unknown. During the last decade, the zebrafish became an excellent and established model organism (1) to uncover these genetic defects and (2) to elucidate the underlying molecular pathomechanisms. We recently isolated the zebrafish mutation ping pong ( png m683 ) in a large-scale ENU-mutagenesis screen for recessive lethal mutations that perturb cardiac function. png mutant zebrafish embryos show pathologically developed cardiac valves. Due to malformation of the cardiac AV valves, png mutant zebrafish embryos exhibit vigorous regurgitation of blood between the atrium and the ventricle. Furthermore, as a result of the cardiac valve malformation and cardiac dysfunction png mutants die at day 6 post fertilization. Expression of several factors known to be crucial for the proper development and formation of the atrio-ventricluar canal (e.g. notch1b, bmp4 or versican) is significantly altered in png mutant zebrafish hearts. By a positional cloning approach we demonstrate that the ping pong phenotype is caused by a promotor mutation in a zebrafish gene encoding for a novel component of the “transcriptional mediator complex”. This mediator complex is a multi-protein complex that acts as a transcriptional coactivator and transduces informations from transcription factors to the RNA polymerase II. png is strongly expressed in zebrafish as well as human cardiomyocytes. Furthermore, sequence alignments demonstrate the evolutionary conservation of the ping pong gene product. Gene specific knock-down studies by means of modified antisense oligonucleotides reveal a phenocopy of the png mutant phenotype whereas injection of the gene-specific mRNA in png mutant embryos restores the mutant phenotype indicating that png is indeed responsible for the observed phenotype. The zebrafish evolved as an excellent model organism to study the molecular signalling pathways involved in cardiac valve formation. By detailed characterization of the zebrafish line ping pong we will obtain new insights into these molecular mechanisms especially the transcriptional control of valve formation and therefore the pathomechanisms of human cardiac valve disorders.

Pbx/Meis Deficiencies Demonstrate Multigenetic Origins of Congenital Heart Disease

Congenital heart diseases are traditionally considered to be multifactorial in pathogenesis resulting from environmental and genetic interactions that determine penetrance and expressivity within a genetically predisposed family. Recent evidence suggests that genetic contributions have been significantly underestimated. However, single gene defects occur only in a minority of cases, and multigenetic causes of congenital heart diseases have not been fully demonstrated. Here, we show that interactions between alleles of 3 Pbx genes, which encode homeodomain transcription factors, are sufficient to determine the phenotypic presentation of congenital heart diseases in mice. A major role is served by Pbx1, whose inactivation results in persistent truncus arteriosus. Reduction or absence of Pbx2 or Pbx3 leads to Pbx1 haploinsufficiency and specific malformations that resemble tetralogy of Fallot, overriding aorta with ventricular septal defect, and bicuspid aortic valves. Disruption of Meis1, which encodes a Pbx DNA-binding partner, results in cardiac anomalies that resemble those caused by Pbx mutations. Each of the observed cardiac defects represents developmental abnormalities affecting distinct stages of cardiac outflow tract development and corresponds to specific types of human congenital heart disease. Thus, varied deficiencies in the Pbx gene family produce a full spectrum of cardiac defects involving the outflow tract, providing a framework for determining multigenetic causes of congenital heart anomalies.

Zebrafish early cardiac connexin, Cx36.7/Ecx, regulates myofibril orientation and heart morphogenesis by establishing Nkx2.5 expression

Heart development is a precisely coordinated process of cellular proliferation, migration, differentiation, and integrated morphogenetic interactions, and therefore it is highly susceptible to developmental anomalies such as the congenital heart disease (CHD). One of the major causes of CHD has been shown to be the mutations in key cardiac transcription factors, including nkx2.5. Here, we report the analysis of zebrafish mutant ftk that showed a progressive heart malformation in the later stages of heart morphogenesis. Our analyses revealed that the cardiac muscle maturation and heart morphogenesis in ftk mutants were impaired because of the disorganization of myofibrils. Notably, we found that the expression of nkx2.5 was down-regulated in the ftk heart despite the normal expression of gata4 and tbx5, suggesting a common mechanism for the occurrence of ftk phenotype and CHD. We identified ftk to be a loss-of-function mutation in a connexin gene, cx36.7/early cardiac connexin (ecx), expressed during early heart development. We further showed by a rescue experiment that Nkx2.5 is the downstream mediator of Ecx-mediated signaling. From these results, we propose that the cardiac connexin Ecx and its downstream signaling are crucial for establishing nkx2.5 expression, which in turn promotes unidirectional, parallel alignment of myofibrils and the subsequent proper heart morphogenesis.

Congenital Duodenal Obstruction: The Impact of Downs Syndrome in Neonatal Morbidity. A Two-Center Survey

Background/Purpose: Babies with congenital duodenal obstruction (CDO) have a high incidence of additional anomalies. Downs syndrome (DS) is the most common associated chromosomal defect, affecting up to 20% of these newborns. Morbidity is expected to be higher in DS patients, since it is a major cause of congenital heart disease, immunodeficiency, and other birth defects. We could find only one report concerning the morbidity in the DS newborn, when associated with CDO. The purpose of this report is to compare the postoperative outcome of two groups of newborns with CDO: group I, patients with associated DS and group II, without DS. Methods: A two-center retrospective review of charts of 46 newborns with CDO admitted to the Hospital of “UNICAMP” and the “Hospital das Clinicas da UFMG”, between 1993 and 2001, was undertaken. Results: Sixteen (34,7%) of the 46 babies had DS. The groups were homogeneous concerning gestational age, gender, birth weight and nutritional status. There was a higher incidence of cardiopathy (56% x 20%) and sepsis (37% x 16%) among patients with DS; however we could find statistic difference only for the incidence of cardiopathy. The survival rate was similar for both groups, reaching 94%. Conclusions: Despite the associated anomalies, newborns with DS individuals had a similar postoperative course, when compared with babies without DS after surgical correction of CDO. The earlier diagnosis of CDO and other birth defects, associated with intensive care, appropriate surgical procedure and postoperative support can provide an equivalent morbidity for DS patients.

A common cause of congenital heart disease

The schematic of a family tree shows the facial appearance of three women (fig 1). The woman in panel A is in her mid 50s and her two daughters (panels...

Essential role of Smad4 in maintaining cardiomyocyte proliferation during murine embryonic heart development

Transforming growth factor-β/bone morphogenetic protein (TGF-β/BMP) signaling pathway is essential for embryonic and postnatal heart development and remodeling. The intracellular factor Smad4 plays a pivotal role in mediating TGF-β/BMP signal transduction in the nucleus. To examine the function of Smad4 in embryonic cardiac development during mid-gestation, we specifically deleted the Smad4 gene in embryonic cardiomyocytes using the Cre–Lox P system. Deletion of Smad4 as early as E9.5, led to embryonic lethality between E12.5 and E15.5, and embryos exhibited severe morphological defects in the heart, including a thin compact layer, disorganized trabeculae, and ventricular septum defects (VSD). Smad4 deletion also led to a dramatic decrease in cardiomyocyte proliferation accompanied by downregulation of contractile protein-encoding genes such as α-myosin heavy chain, β-myosin heavy chain, ventricular myosin light chain 2, and α-cardiac actin. In addition, deletion of Smad4 resulted in perturbation of TGF-β/BMP ligand expression and signaling, and defects in expression of several cardiac transcription factor genes such as Nkx2.5, GATA4, and MEF2c. These results provide direct genetic evidences that Smad4 is essential for regulating cardiomyocyte proliferation and differentiation during murine cardiogenesis, and provides new insights into potential causes of congenital heart disease.

Mediating ERK1/2 signaling rescues congenital heart defects in a mouse model of Noonan syndrome

Noonan syndrome (NS) is an autosomal dominant disorder characterized by a wide spectrum of defects, which most frequently include proportionate short stature, craniofacial anomalies, and congenital heart disease (CHD). NS is the most common nonchromosomal cause of CHD, and 80%-90% of NS patients have cardiac involvement. Mutations within the protein tyrosine phosphatase Src homology region 2, phosphatase 2 (SHP2) are responsible for approximately 50% of the cases of NS with cardiac involvement. To understand the developmental stage- and cell type-specific consequences of the NS SHP2 gain-of-function mutation, Q79R, we generated transgenic mice in which the mutated protein was expressed during gestation or following birth in cardiomyocytes. Q79R SHP2 embryonic hearts showed altered cardiomyocyte cell cycling, ventricular noncompaction, and ventricular septal defects, while, in the postnatal cardiomyocyte, Q79R SHP2 expression was completely benign. Fetal expression of Q79R led to the specific activation of the ERK1/2 pathway, and breeding of the Q79R transgenics into ERK1/2-null backgrounds confirmed the pathway's necessity and sufficiency in mediating mutant SHP2's effects. Our data establish the developmental stage-specific effects of Q79R cardiac expression in NS; show that ablation of subsequent ERK1/2 activation prevents the development of cardiac abnormalities; and suggest that ERK1/2 modulation could have important implications for developing therapeutic strategies in CHD.

Mutations in Cardiac T-Box Factor Gene TBX20 Are Associated with Diverse Cardiac Pathologies, Including Defects of Septation and Valvulogenesis and Cardiomyopathy

The T-box family transcription factor gene TBX20 acts in a conserved regulatory network, guiding heart formation and patterning in diverse species. Mouse Tbx20 is expressed in cardiac progenitor cells, differentiating cardiomyocytes, and developing valvular tissue, and its deletion or RNA interference-mediated knockdown is catastrophic for heart development. TBX20 interacts physically, functionally, and genetically with other cardiac transcription factors, including NKX2-5, GATA4, and TBX5, mutations of which cause congenital heart disease (CHD). Here, we report nonsense (Q195X) and missense (I152M) germline mutations within the T-box DNA-binding domain of human TBX20 that were associated with a family history of CHD and a complex spectrum of developmental anomalies, including defects in septation, chamber growth, and valvulogenesis. Biophysical characterization of wild-type and mutant proteins indicated how the missense mutation disrupts the structure and function of the TBX20 T-box. Dilated cardiomyopathy was a feature of the TBX20 mutant phenotype in humans and mice, suggesting that mutations in developmental transcription factors can provide a sensitized template for adult-onset heart disease. Our findings are the first to link TBX20 mutations to human pathology. They provide insights into how mutation of different genes in an interactive regulatory circuit lead to diverse clinical phenotypes, with implications for diagnosis, genetic screening, and patient follow-up.