GATA4 transgenic mice as an in vivo model of congenital heart disease

Cardiac Development and Factors Influencing the Development of Congenital Heart Defects (CHDs): Part I

The traditional description of cardiac development involves progression from a cardiac crescent to a linear heart tube, which in the phase of transformation into a mature heart forms a cardiac loop and is divided with the septa into individual cavities. Cardiac morphogenesis involves numerous types of cells originating outside the initial cardiac crescent, including neural crest cells, cells of the second heart field origin, and epicardial progenitor cells. The development of the fetal heart and circulatory system is subject to regulatation by both genetic and environmental processes. The etiology for cases with congenital heart defects (CHDs) is largely unknown, but several genetic anomalies, some maternal illnesses, and prenatal exposures to specific therapeutic and non-therapeutic drugs are generally accepted as risk factors. New techniques for studying heart development have revealed many aspects of cardiac morphogenesis that are important in the development of CHDs, in particular transposition of the great arteries.

Toxic effects of bisphenol AF on the embryonic development of marine medaka (Oryzias melastigma)

Bisphenol AF (BPAF), an emerging environmental endocrine disruptor, has been detected in surface waters worldwide and has adverse effects on aquatic organisms. The accumulation of BPAF in oceans and its potential toxic effect on marine organisms are important concerns. In this study, the effects of BPAF (10, 100, 1, and 5 mg/L) on marine medaka (Oryzias melastigma) were evaluated, including effects on the survival rate, heart rate, hatchability, morphology, and gene expression in embryos. The survival rate of marine medaka embryos was significantly lower after treatment with 5 mg/L BPAF than in the solvent control group. Exposure to 1 mg/L and 5 mg/L BPAF significantly reduced hatchability. Low-dose BPAF (10 μg/L) significantly accelerated the heart rate of embryos, while high-dose BPAF (5 mg/L) significantly decreased the heart rate. BPAF exposure also resulted in notochord curvature, pericardial edema, yolk sac cysts, cardiovascular bleeding, and caudal curvature in marine medaka. At the molecular level, BPAF exposure affected the transcript levels of genes involved in the thyroid system (dio1, dio3a, trhr2, tg, and thra), cardiovascular system (gata4, atp2a1, and cacna1da), nervous system (elavl3 and gap43), and antioxidant and inflammatory systems (sod, pparβ, and il-8) in embryos. These results indicate that BPAF exposure can alter the expression of functional genes, induce abnormal development, and reduce the hatching and survival rates in marine medaka embryos. Overall, BPAF can adversely affect the survival and development of marine medaka embryos, and BPAF may not be an ideal substitute for BPA.

DIO3 protects against thyrotoxicosis-derived cranio-encephalic and cardiac congenital abnormalities

Maternal hyperthyroidism is associated with an increased incidence of congenital abnormalities at birth, but it is not clear which of these defects arise from a transient developmental excess of thyroid hormone and which depend on pregnancy stage, antithyroid drug choice, or unwanted subsequent fetal hypothyroidism. To address this issue, we studied a mouse model of comprehensive developmental thyrotoxicosis secondary to a lack of type 3 deiodinase (DIO3). Dio3-/- mice exhibited reduced neonatal viability on most genetic backgrounds and perinatal lethality on a C57BL/6 background. Dio3-/- mice exhibited severe growth retardation during the neonatal period and cartilage loss. Mice surviving after birth manifested brain and cranial dysmorphisms, severe hydrocephalus, choanal atresia, and cleft palate. These abnormalities were noticeable in C57BL/6J Dio3-/- mice at fetal stages, in addition to a thyrotoxic heart with septal defects and thin ventricular walls. Our findings stress the protecting role of DIO3 during development and support the hypothesis that human congenital abnormalities associated with hyperthyroidism during pregnancy are caused by transient thyrotoxicosis before clinical intervention. Our results also suggest thyroid hormone involvement in the etiology of idiopathic pathologies including cleft palate, choanal atresia, Chiari malformations, Kaschin-Beck disease, and Temple and other cranio-encephalic and heart syndromes.

Towards Understanding the Gene-Specific Roles of GATA Factors in Heart Development: Does GATA4 Lead the Way?

Transcription factors play crucial roles in the regulation of heart induction, formation, growth and morphogenesis. Zinc finger GATA transcription factors are among the critical regulators of these processes. GATA4, 5 and 6 genes are expressed in a partially overlapping manner in developing hearts, and GATA4 and 6 continue their expression in adult cardiac myocytes. Using different experimental models, GATA4, 5 and 6 were shown to work together not only to ensure specification of cardiac cells but also during subsequent heart development. The complex involvement of these related gene family members in those processes is demonstrated through the redundancy among them and crossregulation of each other. Our recent identification at the genome-wide level of genes specifically regulated by each of the three family members and our earlier discovery that gata4 and gata6 function upstream, while gata5 functions downstream of noncanonical Wnt signalling during cardiac differentiation, clearly demonstrate the functional differences among the cardiogenic GATA factors. Such suspected functional differences are worth exploring more widely. It appears that in the past few years, significant advances have indeed been made in providing a deeper understanding of the mechanisms by which each of these molecules function during heart development. In this review, I will therefore discuss current evidence of the role of individual cardiogenic GATA factors in the process of heart development and emphasize the emerging central role of GATA4.

Alternative strategies in cardiac preclinical research and new clinical trial formats

An efficient and safe drug development process is crucial for the establishment of new drugs on the market aiming to increase quality of life and life-span of our patients. Despite technological advances in the past decade, successful launches of drug candidates per year remain low. We here give an overview about some of these advances and suggest improvements for implementation to boost preclinical and clinical drug development with a focus on the cardiovascular field. We highlight advantages and disadvantages of animal experimentation and thoroughly review alternatives in the field of three-dimensional cell culture as well as preclinical use of spheroids and organoids. Microfluidic devices and their potential as organ-on-a-chip systems, as well as the use of living animal and human cardiac tissues are additionally introduced. In the second part, we examine recent gold standard randomized clinical trials and present possible modifications to increase lead candidate throughput: adaptive designs, master protocols, and drug repurposing. In silico and N-of-1 trials have the potential to redefine clinical drug candidate evaluation. Finally, we briefly discuss clinical trial designs during pandemic times.

Decoding Genetics of Congenital Heart Disease Using Patient-Derived Induced Pluripotent Stem Cells (iPSCs)

Congenital heart disease (CHD) is the most common cause of infant death associated with birth defects. Recent next-generation genome sequencing has uncovered novel genetic etiologies of CHD, from inherited and de novo variants to non-coding genetic variants. The next phase of understanding the genetic contributors of CHD will be the functional illustration and validation of this genome sequencing data in cellular and animal model systems. Human induced pluripotent stem cells (iPSCs) have opened up new horizons to investigate genetic mechanisms of CHD using clinically relevant and patient-specific cardiac cells such as cardiomyocytes, endothelial/endocardial cells, cardiac fibroblasts and vascular smooth muscle cells. Using cutting-edge CRISPR/Cas9 genome editing tools, a given genetic variant can be corrected in diseased iPSCs and introduced to healthy iPSCs to define the pathogenicity of the variant and molecular basis of CHD. In this review, we discuss the recent progress in genetics of CHD deciphered by large-scale genome sequencing and explore how genome-edited patient iPSCs are poised to decode the genetic etiologies of CHD by coupling with single-cell genomics and organoid technologies.

The M310T mutation in the GATA4 gene is a novel pathogenic target of the familial atrial septal defect

BACKGROUND

Although most cases of atrial septal defect (ASD) are sporadic, familial cases have been reported, which may be caused by mutation of transcription factor GATA binding protein 4 (GATA4). Herein we combined whole-exome sequencing and bioinformatics strategies to identify a novel mutation in GATA4 accounting for the etiology in a Chinese family with ASD.

METHODS

We identified kindred spanning 3 generations in which 3 of 12 (25.0%) individuals had ASD. Punctilious records for the subjects included complete physical examination, transthoracic echocardiography, electrocardiograph and surgical confirming. Whole-exome capture and high-throughput sequencing were performed on the proband III.1. Sanger sequencing was used to validate the candidate variants, and segregation analyses were performed in the family members.

RESULTS

Direct sequencing of GATA4 from the genomic DNA of family members identified a T-to-C transition at nucleotide 929 in exon 5 that predicted a methionine to threonine substitution at codon 310 (M310T) in the nuclear localization signal (NLS) region. Two affected members (II.2 and III.3) and the proband (III.1) who was recognized as a carrier exhibited this mutation, whereas the other unaffected family members or control individuals did not. More importantly, the mutation GATA4 (c.T929C: p.M310T) has not been reported previously in either familial or sporadic cases of congenital heart defects (CHD).

CONCLUSIONS

We identified for the first time a novel M310T mutation in the GATA4 gene that is located in the NLS region and leads to family ASD with arrhythmias. However, the mechanism by which this pathogenic mutation contributes to the development of heart defect and tachyarrhythmias remains to be ascertained.

Experimental Rodent Models of Cardiovascular Diseases

Cardiovascular diseases, as the most common non-communicable disease in the world, cause a high mortality rate today and bring a serious medical burden to countries worldwide, especially in low- and middle-income countries. Experimental rodent models are widely used for cardiovascular diseases researches due to the effective simulation of human cardiovascular diseases, strong reproductive ability, and easy detection. Herein, we will summarize the pathological manifestations of common cardiovascular diseases and illustrate the establishment of corresponding experimental rodent models in detail.

Connection of GLI1 variants to congenital heart disease susceptibility: A case-control study

The purpose of this study was to investigate the relationship between glioma-associated oncogene homolog 1 (GLI1) rs2228226 and rs10783826 polymorphisms and congenital heart disease (CHD) risk in a Chinese Han population.Genotyping for our interested polymorphisms was performed using polymerase chain reaction-restriction fragment length polymorphism in 106 CHD patients and 112 healthy controls. Hardy-Weinberg equilibrium status in the control group was also checked via χ test. Differences in genotype and allele frequencies between the case and control groups were analyzed adopting Chi-Squared test as well, and the relative risk of CHD resulting from GLI1 genetic variants was checked via calculating odds ratio (OR) and 95% confidence interval (95%CI).CC genotype of rs2228226 showed significantly higher frequency in CHD patients than in controls (P = .011), indicating that it increased the disease risk (OR = 3.257, 95%CI = 1.280-8.287). Similarly, C allele of the polymorphism elevated CHD incidence by 1.609 folds, compared with G allele (OR = 1.609, 95%CI = 1.089-2.376). However, rs10783826 was not correlated with the occurrence of CHD.GLI1 rs2228226 polymorphism may be a risk factor for CHD in Chinese Han population, but not rs10783826.

Congenital heart diseases: genetics, non-inherited risk factors, and signaling pathways

Background

Congenital heart diseases (CHDs) are the most common congenital anomalies with an estimated prevalence of 8 in 1000 live births. CHDs occur as a result of abnormal embryogenesis of the heart. Congenital heart diseases are associated with significant mortality and morbidity. The damage of the heart is irreversible due to a lack of regeneration potential, and usually, the patients may require surgical intervention. Studying the developmental biology of the heart is essential not only in understanding the mechanisms and pathogenesis of congenital heart diseases but also in providing us with insight towards developing new preventive and treatment methods.

Main body

The etiology of congenital heart diseases is still elusive. Both genetic and environmental factors have been implicated to play a role in the pathogenesis of the diseases. Recently, cardiac transcription factors, cardiac-specific genes, and signaling pathways, which are responsible for early cardiac morphogenesis have been extensively studied in both human and animal experiments but leave much to be desired. The discovery of novel genetic methods such as next generation sequencing and chromosomal microarrays have led to further study the genes, non-coding RNAs and subtle chromosomal changes, elucidating their implications to the etiology of congenital heart diseases. Studies have also implicated non-hereditary risk factors such as rubella infection, teratogens, maternal age, diabetes mellitus, and abnormal hemodynamics in causing CHDs.

These etiological factors raise questions on multifactorial etiology of CHDs. It is therefore important to endeavor in research based on finding the causes of CHDs. Finding causative factors will enable us to plan intervention strategies and mitigate the consequences associated with CHDs. This review, therefore, puts forward the genetic and non-genetic causes of congenital heart diseases. Besides, it discusses crucial signaling pathways which are involved in early cardiac morphogenesis. Consequently, we aim to consolidate our knowledge on multifactorial causes of CHDs so as to pave a way for further research regarding CHDs.

Conclusion

The multifactorial etiology of congenital heart diseases gives us a challenge to explicitly establishing specific causative factors and therefore plan intervention strategies. More well-designed studies and the use of novel genetic technologies could be the way through the discovery of etiological factors implicated in the pathogenesis of congenital heart diseases.

Genetic Basis for Congenital Heart Disease: Revisited: A Scientific Statement From the American Heart Association

This review provides an updated summary of the state of our knowledge of the genetic contributions to the pathogenesis of congenital heart disease. Since 2007, when the initial American Heart Association scientific statement on the genetic basis of congenital heart disease was published, new genomic techniques have become widely available that have dramatically changed our understanding of the causes of congenital heart disease and, clinically, have allowed more accurate definition of the pathogeneses of congenital heart disease in patients of all ages and even prenatally. Information is presented on new molecular testing techniques and their application to congenital heart disease, both isolated and associated with other congenital anomalies or syndromes. Recent advances in the understanding of copy number variants, syndromes, RASopathies, and heterotaxy/ciliopathies are provided. Insights into new research with congenital heart disease models, including genetically manipulated animals such as mice, chicks, and zebrafish, as well as human induced pluripotent stem cell-based approaches are provided to allow an understanding of how future research breakthroughs for congenital heart disease are likely to happen. It is anticipated that this review will provide a large range of health care-related personnel, including pediatric cardiologists, pediatricians, adult cardiologists, thoracic surgeons, obstetricians, geneticists, genetic counselors, and other related clinicians, timely information on the genetic aspects of congenital heart disease. The objective is to provide a comprehensive basis for interdisciplinary care for those with congenital heart disease.

From embryogenesis to adulthood: Critical role for GATA factors in heart development and function

Cardiac development is governed by a complex network of transcription factors (TFs) that regulate cell fates in a spatiotemporal manner. Among these, the GATA family of zinc finger TFs plays prominent roles in regulating the development of the myocardium, endocardium, and outflow tract. This family comprises six members three of which, GATA4, 5, and 6, are predominantly expressed in cardiac cells where they activate specific downstream gene targets via interactions with one another and with other TFs and signaling molecules. Their critical function in heart formation is evidenced by the phenotypes of animal models lacking these factors and by the broad spectrum of human congenital heart diseases associated with mutations in their genes. Similarly, in the postnatal heart, these proteins play significant and nonredundant roles in cardiac function, regulating adaptive stress responses including cardiomyocyte hypertrophy and survival, as well as endothelial homeostasis and angiogenesis. As such, decreased expression of either GATA4, 5, or 6 results in impaired cardiovascular homeostasis and increased risk of premature and serious cardiovascular events such as hypertension, arrhythmia, aortopathy, and heart failure. Although a great deal of progress has been made in understanding GATA-dependent regulatory processes in the heart, the molecular mechanisms underlying the specificity of GATA factors and their upstream regulation remain incompletely understood. The knowledge and tools developed since their discovery 25 years ago should accelerate progress toward further elucidation of their mechanisms of action in health and disease. This in turn will greatly improve diagnosis and care for the millions of individuals affected by congenital and acquired cardiac disease worldwide.

[Establishment and verification of a mouse model of Gata4 gene H435Y mutation]

OBJECTIVE

To establish a mouse model of H435Y mutation of Gata4 gene using CRISPR/Cas9- mediated gene targeting.

METHODS

The single-stranded guide RNA (sgRNA) specific to the H435Y loci of Gata4 gene was designed based on the sequence of Gata4 gene. After activity assessment, the active sgRNA and Cas9 were in vitro transcribed into RNA and microinjected along with the donor DNA fragment with point mutations into fertilized mouse eggs. The microinjected eggs were transferred into pseudopregnant mice to obtain the F0 generation mice with the target Gata4 gene mutation confirmed by PCR and gene sequencing. Gata4 gene mutations in the offsprings of the F0 generation mice were analyzed.

RESULTS

Gene sequencing confirmed the successful establishment of mouse models carrying H435Y mutation of Gata4 gene in 4 of the F0 generation mice. The positive F0 generation mice were crossed with wild-type C57BL/6J mice to obtain the F1 generation mice, and PCR confirmed the presence of H435Y mutations of Gata4 gene in 6 of the F1 mice. Then F2 generation mice were obtained by F1 generation matting with each other. PCR showed that H435Y mutation of Gata4 gene in F2 mice was found, indicating the mousemodel of Gata4 gene mutation in H435Y was established and propagated successfully.

CONCLUSIONS

We successfully established Gata4 gene H435Y mutant mouse models using CRISPR/Cas9 technique.

Functional mutant GATA4 identification and potential application in preimplantation diagnosis of congenital heart diseases

Congenital heart diseases (CHDs) affect nearly 1% of all neonates and show an increasing tendency. The complex inheritance patterns and multifactorial etiologies make these defects difficult to be identified before complete manifestation. Genetic screening has identified hundreds of specific mutant sites for CHDs based on cardiac transcriptional factors. GATA4 is a master regulator required for ventral morphogenesis and heart tube formation. Its mutation is most widely studied in CHDs. In the past decades, over 100 GATA4 mutant sites have been reported, but only a few functional sites have been identified. Thus, it is important to distinguish deleterious sites from neutral sites. In silico prediction of functional sites using bioinformatics tools can provide the valuable information, but it is not solid enough. Here, the roles of GATA4 in heart development is discussed in detail and its mutation sites in protein coding region are summarized systematically, providing an integrated resource for GATA4 mutations. Furthermore, we discussed the advantage and disadvantage of different methods for functional mutation identification. Especially, the disease model of induced pluripotent stem cell is emerging as a powerful tool to assess GATA4 mutations in human. In the recent years, single-cell based high-throughput sequencing is being applied in preimplantation diagnosis and assisted reproduction progressively, providing a new strategy for the prevention of congenital diseases as we discussed. Based on functional mutant sites identification, preimplantation diagnosis will contribute to CHDs prevention eventually.

TBX1 loss-of-function mutation contributes to congenital conotruncal defects

Conotruncal defects (CTDs) account for ~30% of all types of congenital heart disease and contribute to increased morbidity and mortality rates. Increasing evidence suggests that genetic risk factors are involved in the pathogenesis of CTDs. Mutations in a number of genes, including the TBX1 gene that codes for a T-box transcription factor essential for normal cardiovascular development, may contribute to the development of CTD. CTDs are genetically heterogeneous and the genetic defects responsible for CTDs in the majority of patients remain unknown. The present study sequenced the coding regions and splicing junction boundaries of TBX1 in 136 patients with CTDs and 300 matched healthy individuals. The disease-causing potential of the identified TBX1 sequence variation was evaluated using MutationTaster, PolyPhen-2, SIFT and PROVEN software. The functional characteristics of the mutant TBX1 gene were defined using a dual-luciferase reporter assay system. A novel heterozygous TBX1 mutation, p.S233Y, was identified in a patient with transposition of the great arteries (TGA) and a ventricular septal defect. This mutation was absent in the 300 controls and altered the amino acid produced, serine, which is evolutionarily conserved across several species, and was predicted to be pathogenic in silico. Luciferase assays conducted in COS-7 cells demonstrated that the newly identified TBX1 mutation was associated with significantly diminished transcriptional activation of the ANF promoter compared with the wild-type TBX1. To the best of our knowledge, the present study is the first to associate a TBX1 loss-of-function mutation with enhanced susceptibility to TGA, which adds significant insight to the molecular mechanism of TGA.

Utilization of Whole Exome Sequencing to Identify Causative Mutations in Familial Congenital Heart Disease

BACKGROUND

Congenital heart disease (CHD) is the most common type of birth defect with family- and population-based studies supporting a strong genetic cause for CHD. The goal of this study was to determine whether a whole exome sequencing (WES) approach could identify pathogenic-segregating variants in multiplex CHD families.

METHODS AND RESULTS

WES was performed on 9 kindreds with familial CHD, 4 with atrial septal defects, 2 with patent ductus arteriosus, 2 with tetralogy of Fallot, and 1 with pulmonary valve dysplasia. Rare variants (<1% minor allele frequency) that segregated with disease were identified by WES, and variants in 69 CHD candidate genes were further analyzed. These selected variants were subjected to in silico analysis to predict pathogenicity and resulted in the discovery of likely pathogenic mutations in 3 of 9 (33%) families. A GATA4 mutation in the transactivation domain, p.G115W, was identified in familial atrial septal defects and demonstrated decreased transactivation ability in vitro. A p.I263V mutation in TLL1 was identified in an atrial septal defects kindred and is predicted to affect the enzymatic functionality of TLL1. A disease-segregating splice donor site mutation in MYH11 (c.4599+1delG) was identified in familial patent ductus arteriosus and found to disrupt normal splicing of MYH11 mRNA in the affected individual.

CONCLUSIONS

Our findings demonstrate the clinical utility of WES to identify causative mutations in familial CHD and demonstrate the successful use of a CHD candidate gene list to allow for a more streamlined approach enabling rapid prioritization and identification of likely pathogenic variants from large WES data sets.

CLINICAL TRIAL REGISTRATION

URL: https://clinicaltrials.gov; Unique Identifier: NCT0112048.