Elevated methylation of the RXRA promoter region may be responsible for its downregulated expression in the myocardium of patients with TOF

Right Ventricle and Epigenetics: A Systematic Review

There is an increasing recognition of the crucial role of the right ventricle (RV) in determining the functional status and prognosis in multiple conditions. In the past decade, the epigenetic regulation (DNA methylation, histone modification, and non-coding RNAs) of gene expression has been raised as a critical determinant of RV development, RV physiological function, and RV pathological dysfunction. We thus aimed to perform an up-to-date review of the literature, gathering knowledge on the epigenetic modifications associated with RV function/dysfunction. Therefore, we conducted a systematic review of studies assessing the contribution of epigenetic modifications to RV development and/or the progression of RV dysfunction regardless of the causal pathology. English literature published on PubMed, between the inception of the study and 1 January 2023, was evaluated. Two authors independently evaluated whether studies met eligibility criteria before study results were extracted. Amongst the 817 studies screened, 109 studies were included in this review, including 69 that used human samples (e.g., RV myocardium, blood). While 37 proposed an epigenetic-based therapeutic intervention to improve RV function, none involved a clinical trial and 70 are descriptive. Surprisingly, we observed a substantial discrepancy between studies investigating the expression (up or down) and/or the contribution of the same epigenetic modifications on RV function or development. This exhaustive review of the literature summarizes the relevant epigenetic studies focusing on RV in human or preclinical setting.

De novo DNA methylation induced by circulating extracellular vesicles from acute coronary syndrome patients

BACKGROUND AND AIMS

DNA methylation is associated with gene silencing, but its clinical role in cardiovascular diseases (CVDs) remains to be elucidated. We hypothesized that extracellular vesicles (EVs) may carry epigenetic changes, showing themselves as a potentially valuable non-invasive diagnostic liquid biopsy. We isolated and characterized circulating EVs of acute coronary syndrome (ACS) patients and assessed their role on DNA methylation in epigenetic modifications.

METHODS

EVs were recovered from plasma of 19 ACS patients and 50 healthy subjects (HS). Flow cytometry, qRT-PCR, and Western blot (WB) were performed to evaluate both intra-vesicular and intra-cellular signals. ShinyGO, PANTHER, and STRING tools were used to perform GO and PPI network analyses.

RESULTS

ACS-derived EVs showed increased levels of DNA methyltransferases (DNMTs) (p<0.001) and Ten-eleven translocation (TET) genes reduction. Specifically, de novo methylation transcripts, as DNMT3A and DNMT3B, were significantly increased in plasma ACS-EVs. DNA methylation analysis on PBMCs from healthy donors treated with HS- and ACS-derived EVs showed an important role of DNMTs carried by EVs. PPI network analysis evidenced that ACS-EVs induced changes in PBMC methylome. In the most enriched subnetwork, the hub gene SRC was connected to NOTCH1, FOXO3, CDC42, IKBKG, RXRA, DGKG, BAIAP2 genes that were showed to have many molecular effects on various cell types into onset of several CVDs. Modulation in gene expression after ACS-EVs treatment was confirmed for SRC, NOTCH1, FOXO3, RXRA, DGKG and BAIAP2 (p<0.05).

CONCLUSIONS

Our data showed an important role for ACS-derived EVs in gene expression modulation through de novo DNA methylation signals, and modulating signalling pathways in target cells.

The effect of maternal polycyclic aromatic hydrocarbons exposure and methylation levels of CHDs-candidate genes on the risk of congenital heart diseases

OBJECTIVE

To evaluate the impact of maternal exposure to polycyclic aromatic hydrocarbons (PAHs) and methylation levels of CHDs-candidate genes on the risk of congenital heart diseases (CHDs), and the effect of PAHs exposure on DNA methylation states.

METHODS

A case-control study involving 60 mother -fetus pairs was performed by measuring 1-OHPG concentration in maternal urine and methylation levels of 20 CHDs-candidate genes in cord bloods. Logistic regression models were applied to determine the effect of maternal PAHs exposure and fetal methylation levels on the risk of CHDs. Spearman correlation was performed to correlate PAHs exposure and methylation levels.

RESULTS

Maternal higher PAHs exposure was associated with the risk of CHDs (aOR = 3.245, 95% CI: 1.060, 9.937) or some subtypes. The methylation levels of 23 amplicons within 11 genes exhibited significant differences between CHDs and controls. Higher methylation of NKX2-5_M1 was associated with decreased risk of CHDs (aOR=0.182, 95% CI:0.034, 0.983). No significant correlations were found between 1-OHPG concentration and methylation levels of NKX2-5_M1.

CONCLUSIONS

Maternal PAHs exposure was linked with CHDs. Higher methylation of the upstream sequence of NKX2-5 promoter decreased the risk of CHDs. There was no correlation between maternal PAHs exposure and the methylation level of NKX2-5. This article is protected by copyright. All rights reserved.

Epigenetics in Congenital Heart Disease

Embryonic heart development is an intricate process that mainly involves morphogens, transcription factors, and cardiac genes. The precise spatiotemporal expression of these genes during different developmental stages underlies normal heart development. Thus, mutation or aberrant expression of these genes may lead to congenital heart disease (CHD). However, evidence demonstrates that the mutation of genes accounts for only a small portion of CHD cases, whereas the aberrant expression regulated by epigenetic modification plays a predominant role in the pathogenesis of CHD. In this review, we provide essential knowledge on the aberrant epigenetic modification involved in the pathogenesis of CHD. Then, we discuss recent advances in the identification of novel epigenetic biomarkers. Last, we highlight the epigenetic roles in some adverse intrauterine environment‐related CHD, which may help the prevention, diagnosis, and treatment of these kinds of CHD.

DNA Methylation Levels of the TBX5 Gene Promoter Are Associated with Congenital Septal Defects in Mexican Paediatric Patients

The TBX5 gene regulates morphological changes during heart development, and it has been associated with epigenetic abnormalities observed in congenital heart defects (CHD). The aim of this research was to evaluate the association between DNA methylation levels of the TBX5 gene promoter and congenital septal defects. DNA methylation levels of six CpG sites in the TBX5 gene promoter were evaluated using pyrosequencing analysis in 35 patients with congenital septal defects and 48 controls. Average methylation levels were higher in individuals with congenital septal defects than in the controls (p < 0.004). In five CpG sites, we also found higher methylation levels in patients than in the controls (p < 0.05). High methylation levels were associated with congenital septal defects (OR = 3.91; 95% CI = 1.02–14.8; p = 0.045). The analysis of Receiver Operating Characteristic (ROC) showed that the methylation levels of the TBX5 gene could be used as a risk marker for congenital septal defects (AUC = 0.68, 95% CI = 0.56–0.80; p = 0.004). Finally, an analysis of environmental factors indicated that maternal infections increased the risk (OR = 2.90; 95% CI = 1.01–8.33; p = 0.048) of congenital septal defects. Our data suggest that a high DNA methylation of the TBX5 gene could be associated with congenital septal defects.

Genome-wide methylation analysis reveals differentially methylated CpG sites and altered expression of heart development-associated genes in fetuses with cardiac defects

DNA methylation, as an epigenetic mechanism, has a vital role in heart development. An increasing number of studies have investigated aberrant DNA methylation in pediatric or adult heart samples from patients with congenital heart defects (CHD). Placenta tissue, umbilical cord blood, or newborn blood have also been used to detect DNA methylation biomarkers for CHD. However, few studies have compared the methylation levels in fetal heart tissue with cardiac defects with that in normal controls. The present study conducted an integrative whole-genome and CpG site-specific DNA methylation analysis of fetal heart samples from 17 isolated cardiac defect cases, 14 non-isolated cardiac defect cases, and 22 controls with normal hearts, using methylated DNA immunoprecipitation microarray and MassARRAY EpiTYPER assays. Expression of genes adjacent to differentially methylated regions (DMRs) was measured by RT-qPCR and western blot analysis. The results revealed that fetuses with cardiac defects presented global hypomethylation. Genomic analysis of DMRs revealed that a proportion of DMRs were located in exons (12.4%), distal intergenic regions (11.14%), and introns (8.97%). Only 55.7% of DMRs were observed at promoter regions. Functional enrichment analysis for genes adjacent to these DMRs revealed that hypomethylated genes were involved in embryonic heart tube morphogenesis and immune-related regulation functions. Intergenic hypermethylation of EGFR and solute carrier family 19 member 1 (SLC19A1), and intragenic hypomethylation of NOTCH1 were validated in fetal heart tissues with cardiac defects. Only SLC19A1 expression was significantly decreased at the mRNA level, while EGFR, NOTCH1, and SLC19A1 expression were all significantly decreased at the protein level. In conclusion, the present study demonstrated that fetal cardiac defects may be associated with alterations in regional and single CpG site methylation outside of promoter regions, resulting in differentiated expression of corresponding genes associated with heart development. These results present new insights into the epigenetic mechanisms underlying abnormal heart development.

Genetic and epigenetic mechanisms in the development of congenital heart diseases

Congenital heart disease (CHD) is the most common of congenital cardiovascular malformations associated with birth defects, and it results in significant morbidity and mortality worldwide. The classification of CHD is still elusive owing to the complex pathogenesis of CHD. Advances in molecular medicine have revealed the genetic basis of some heart anomalies. Genes associated with CHD might be modulated by various epigenetic factors. Thus, the genetic and epigenetic factors are gradually accepted as important triggers in the pathogenesis of CHD. However, few literatures have comprehensively elaborated the genetic and epigenetic mechanisms of CHD. This review focuses on the etiology of CHD from genetics and epigenetics to discuss the role of these factors in the development of CHD. The interactions between genetic and epigenetic in the pathogenesis of CHD are also elaborated. Chromosome abnormalities and gene mutations in genetics, and DNA methylations, histone modifications and on-coding RNAs in epigenetics are summarized in detail. We hope the summative knowledge of these etiologies may be useful for improved diagnosis and further elucidation of CHD so that morbidity and mortality of children with CHD can be reduced in the near future.

The multi-faceted role of retinoid X receptor in cardiovascular diseases

Retinoid X receptors (RXRs) are members of ligand-dependent transcription factors whose effects on a diversity of cellular processes, including cellular proliferation, the immune response, and lipid and glucose metabolism. Knock out of RXRα causes a hypoplasia of the myocardium which is lethal during fetal life. In addition, the heart maintains a well-orchestrated balances in utilizing fatty acids (FAs) and other substrates to meet the high energy requirements. As the master transcriptional regulators of lipid metabolism, RXRs become particularly important for the energy needs of the heart. Accumulating evidence suggested that RXRs may exert direct beneficial effects in the heart both through heterodimerization with other nuclear receptors (NRs) and homodimerization, thus standing as suitable targets for treating in cardiovascular diseases. Although compounds that target RXRs are promising drugs, their use is limited by toxicity. A better understanding of the structural biology of RXRs in cardiovascular disease should enable the rational design of more selective nuclear receptor modulators to overcome these problems. Here, this review summarizes a brief overview of RXRs structure and versatility of RXR action in the control of cardiovascular diseases. And we also discussed the therapeutic potential of RXR ligand.

Hypermethylation-mediated down-regulation of lncRNA TBX5-AS1:2 in Tetralogy of Fallot inhibits cell proliferation by reducing TBX5 expression

Tetralogy of Fallot (TOF) is the most common complex congenital heart disease (CHD) with uncertain cause. Although long non‐coding RNAs (lncRNAs) have been implicated in heart development and several CHDs, their role in TOF is not well understood. This study aimed to investigate how dysregulated lncRNAs contribute to TOF. Using Gene Expression Omnibus data mining, bioinformatics analysis and clinical heart tissue sample detecting, we identified a novel antisense lncRNA TBX5‐AS1:2 with unknown function that was significantly down‐regulated in injured cardiac tissues from TOF patients. LncRNA TBX5‐AS1:2 was mainly located in the nucleus of the human embryonic kidney 293 (HEK293T) cells and formed an RNA‐RNA double‐stranded structure in the overlapping region with its sense mRNA T‐box transcription factor 5 (TBX5), which is an important regulator in heart development. Knock‐down of lncRNA TBX5‐AS1:2 via promoter hypermethylation reduced TBX5 expression at both the mRNA and protein levels by affecting its mRNA stability through RNA‐RNA interaction. Moreover, lncRNA TBX5‐AS1:2 knock‐down inhibited the proliferation of HEK293T cells. In conclusion, these results indicated that lncRNA TBX5‐AS1:2 may be involved in TOF by affecting cell proliferation by targeting TBX5.

Using Network Pharmacology to Explore Potential Treatment Mechanism for Coronary Heart Disease Using Chuanxiong and Jiangxiang Essential Oils in Jingzhi Guanxin Prescriptions

Background

To predict the active components and potential targets of traditional Chinese medicine and to determine the mechanism behind the curative effect of traditional Chinese medicine, a multitargeted method was used. Jingzhi Guanxin prescriptions expressed a high efficacy for coronary heart disease (CHD) patients of which essential oils from Chuanxiong and Jiangxiang were confirmed to be the most important effective substance. However, the interaction between the active components and the targets for the treatment of CHD has not been clearly explained in previous studies.

Materials and Methods

Genes associated with the disease and the treatment strategy were searched from the electronic database and analyzed by Cytoscape (version 3.2.1). Protein-protein interaction network diagram of CHD with Jiangxiang and Chuanxiong essential oils was constructed by Cytoscape. Pathway functional enrichment analysis was executed by clusterProfiler package in R platform.

Results

121 ingredients of Chuanxiong and Jiangxiang essential oils were analyzed, and 393 target genes of the compositions and 912 CHD-related genes were retrieved. 15 coexpression genes were selected, including UGT1A1, DPP4, RXRA, ADH1A, RXRG, UGT1A3, PPARA, TRPC3, CYP1A1, ABCC2, AHR, and ADRA2A. The crucial pathways of occurrence and treatment molecular mechanism of CHD were analyzed, including retinoic acid metabolic process, flavonoid metabolic process, response to xenobiotic stimulus, cellular response to xenobiotic stimulus, cellular response to steroid hormone stimulus, retinoid binding, retinoic acid binding, and monocarboxylic acid binding. Finally, we elucidate the underlying role and mechanism behind these genes in the pathogenesis and treatment of CHD.

Conclusions

Generally speaking, the nodes in subnetwork affect the pathological process of CHD, thus indicating the mechanism of Jingzhi Guanxin prescriptions containing Chuanxiong and Jiangxiang essential oils in the treatment of CHD.

DNA methylation status of TBX20 in patients with tetralogy of Fallot

Background

TBX20 plays an important role in heart development; however, its epigenetic regulation in the pathogenesis of tetralogy of Fallot (TOF) remains unclear.

Methods

The methylation levels of the TBX20 promoter region in the right ventricular myocardial tissues of TOF and control samples were measured by the Sequenom MassARRAY platform. Bisulphite-sequencing PCR (BSP) was used to confirm the TBX20 methylation of CpG sites in cells. Dual-luciferase reporter assays were performed to detect the influence of TBX20 methylation and Sp1 transcription factors on gene activity. An electrophoretic mobility shift assay (EMSA) was used to explore the binding of the Sp1 transcription factor to the TBX20 promoter.

Results

TOF cases had a significantly lower TBX20_M1 methylation level than controls (median methylation: 20.40% vs. 38.73%; p = 0.0047). The Sp1 transcription factor, which binds to Sp1 binding sites in the TBX20_M1 region and promotes TBX20 gene activity, was blocked by the methylation of Sp1 binding sites in normal controls. With decreasing methylation in the TOF cases, the Sp1 transcription factor can bind to its binding site within the TBX20 promoter M1 region and promote TBX20 gene expression.

Conclusions

Hypomethylation of the TBX20 promoter region was observed in the TOF cases, and the high expression of the TBX20 gene may be caused by activated Sp1 transcription factor binding because of the decreasing methylation at the Sp1 transcription factor binding sites within TBX20_M1.

Association between the promoter methylation of the TBX20 gene and tetralogy of fallot

OBJECTIVES

To investigate the association between promoter methylation of the TBX20 gene and tetralogy of Fallot (TOF)． Methods. The methylation level of TBX20 promoter regions in 23 patients with TOF and five controls were analyzed through bisulfite sequencing polymerase chain reaction. Meanwhile, the expression of TBX20 mRNA was measured using real time fluorescence quantitative polymerase chain reaction.

RESULTS

The region -400 to -48 in the TBX20 promoter consisting of 42 CpG sites was predicted to contain multiple transcription factor binding sites. In this study, the overall methylation level in this region was lower in patients with TOF than in the controls (P = .035). Among the 42 CpG sites, the methylation percentages of the CpG 26 site in the TOF cases were lower than those in the controls (P = .016). The mRNA expression of TBX20 in the right ventricular outflow tract myocardium was increased in TOF cases in contrast to those in the controls (P < .001). The methylation levels in TOF cases were correlated with mRNA expression values (r = -0.81, P < .001).

CONCLUSION

The downregulated methylation level at TBX20 promoter may be responsible for the elevated mRNA expression levels in patients with TOF. The abnormal methylation status of the TBX20 promoter may contribute to the pathogenesis of TOF.

DNA Methylation Variability in a Single Locus of the RXRα Promoter from Umbilical Vein Blood at Term Pregnancy

DNA methylation status of RXRα gene promoter has been correlated with maternal diet during early pregnancy, and associated with offspring's adiposity and bone mineral content. In adult life, increased methylation of RXRα promoter region is associated with myocardium pathologies. Early growth response proteins (EGR) are zinc finger transcription factors associated with several cellular pathways such as inflammation, apoptosis, and cardiopathies. DNA-binding sequences of EGR proteins have been reported in the RXRα gene promoter using chromatin immunoprecipitation methods. Here, we used correlations between the maternal pre-pregnancy body mass index (p-BMI), gestational weight gain (GWG), and birth weight (BW) as indirect indicators of the maternal nutritional status as modifier of DNA methylation in the offspring. DNA methylation status from newborns' umbilical vein blood in full-term pregnancy was evaluated in a short sequence (116 pb) of the RXRα gene promoter that contains the elements of response sequence for EGR proteins. Fifty-three bisulfite-modified DNA samples were assessed through methyl-sensitive high-resolution melting (MS-HRM) analysis. To validate the results, we directly sequenced MS-HRM samples to confirm the presence of CpG-methylated positions. In addition, the RXRα protein levels in extracts of umbilical vein blood were evaluated by western blot. We found differential methylation in a specific locus of the RXRα promoter surrounding the EGR-binding sequence; however, no correlation was found with the level of RXRα protein expression. Variability in the methylation status of the RXRα promoter near the EGR transcription factor binding site in newborn cord blood provides controversial epigenetic insights into RXRα regulation via EGR proteins.

Maternal Exposure of BALB/c Mice to Indoor NO2 and Allergic Asthma Syndrome in Offspring at Adulthood with Evaluation of DNA Methylation Associated Th2 Polarization

BACKGROUND

Fetal stress has been proposed to be associated with diseases in both children and adults. Epidemiological studies suggest that maternal exposure to nitrogen dioxide (NO2) contributes to increased morbidity and mortality of offspring with allergic asthma later in life.

OBJECTIVES

We aimed to test whether maternal NO2 exposure causes allergic asthma-related consequences in offspring absent any subsequent lung provocation and whether this exposure enhances the likelihood of developing allergic asthma or the intensity of developed allergic airway disease following postnatal allergic sensitization and challenge. In addition, if such consequences and enhancements occurred, we sought to determine the mechanism(s) of these responses.

METHODS

Pregnant BALB/c mice were exposed to either NO2 (2.5 ppm, 5 h/day) or air daily throughout the gestation period. Offspring were sacrificed on postnatal days (PNDs) 1, 7, 14, 21, and 42, and remaining offspring were sensitized by ovalbumin (OVA) injection followed by OVA aerosol challenge during postnatal wk 7-9. We analyzed the lung histopathology, inflammatory cell infiltration, airway hyper-responsiveness (AHR), immune responses, and gene methylation under different treatment conditions.

RESULTS

Maternal exposure to NO2 caused a striking increase in inflammatory cell infiltration and the release of type 2 cytokines in the lungs of offspring at PNDs 1 and 7; however, these alterations were reversed during postnatal development. Following OVA sensitization and challenge, the exposure enhanced the levels of allergic asthma-characterized OVA-immunoglobulin (Ig) E, AHR, and airway inflammation in adult offspring. Importantly, differentiation of T-helper (Th) 2 cells and demethylation of the interleukin-4 (IL4) gene occurred during the process.

CONCLUSIONS

Maternal exposure to indoor environmental NO2 causes allergic asthma-related consequences in offspring absent any subsequent lung provocation and potentiates the symptoms of allergic asthma in adult offspring following postnatal allergic sensitization and challenge; this response is associated with the Th2-based immune response and DNA methylation of the IL4 gene. https://doi.org/10.1289/EHP685.

Liganded retinoic acid X receptor α represses connexin 43 through a potential retinoic acid response element in the promoter region

INTRODUCTION

Retinoic acid X receptor alpha (RXRα) and Connexin 43 (Cx43) both play a crucial role in cardiogenesis. However, little is known about the interplay mechanism between the RXRα and Cx43.

METHODS

The activations of retinoic acid response element (RARE) in Cx43 were measured by luciferase transfection assay. Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) was performed to prove that RXRα can directly bind to the RARE sequence. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting were used to analyze the RXRα and Cx43 mRNA level and protein level in cells.

RESULTS

In this study, we confirmed the negative association of the gene expression between the RXRα and Cx43 in the cell level. Interestingly, a functional RARE was detected in the region from -1,426 to -314 base pairs upstream from the transcriptional start site of Cx43. Moreover, we also prove that RXRα can directly bind to this RARE sequence in vitro and in vivo.

CONCLUSIONS

RXRα negatively regulates the transcription and expression by directly binding to the RARE in the promoter of Cx43. The RARE-like sequence harbored in the Cx43 promoter region may serve as a functional RARE in the retinoic acid (RA) signaling pathway.

Genome-wide detection of CNVs in Chinese indigenous sheep with different types of tails using ovine high-density 600K SNP arrays

Chinese indigenous sheep can be classified into three types based on tail morphology: fat-tailed, fat-rumped, and thin-tailed sheep, of which the typical breeds are large-tailed Han sheep, Altay sheep, and Tibetan sheep, respectively. To unravel the genetic mechanisms underlying the phenotypic differences among Chinese indigenous sheep with tails of three different types, we used ovine high-density 600K SNP arrays to detect genome-wide copy number variation (CNV). In large-tailed Han sheep, Altay sheep, and Tibetan sheep, 371, 301, and 66 CNV regions (CNVRs) with lengths of 71.35 Mb, 51.65 Mb, and 10.56 Mb, respectively, were identified on autosomal chromosomes. Ten CNVRs were randomly chosen for confirmation, of which eight were successfully validated. The detected CNVRs harboured 3130 genes, including genes associated with fat deposition, such as PPARA, RXRA, KLF11, ADD1, FASN, PPP1CA, PDGFA, and PEX6. Moreover, multilevel bioinformatics analyses of the detected candidate genes were significantly enriched for involvement in fat deposition, GTPase regulator, and peptide receptor activities. This is the first high-resolution sheep CNV map for Chinese indigenous sheep breeds with three types of tails. Our results provide valuable information that will support investigations of genomic structural variation underlying traits of interest in sheep.

De novo 9q gain in an infant with tetralogy of Fallot with absent pulmonary valve: Patient report and review of congenital heart disease in 9q duplication syndrome

Genomic disruptions, altered epigenetic mechanisms, and environmental factors contribute to the heterogeneity of congenital heart defects (CHD). In recent years, chromosomal microarray analysis (CMA) has led to the identification of numerous copy number variations (CNV) in patients with CHD. Genes disrupted by and within these CNVs thus represent excellent candidate genes for CHD. Microduplications of 9q (9q+) have been described in patients with CHD, however, the critical gene locus remains undetermined. Here we discuss an infant with tetralogy of Fallot with absent pulmonary valve, fetal hydrops, and a 3.76 Mb de novo contiguous gain of 9q34.2-q34.3 detected by CMA, and confirmed by karyotype and FISH studies. This duplicated interval disrupted RXRA (retinoid X receptor alpha; OMIM #180245) at intron 1. We also review CHD findings among previously reported patients with 9q (9q+) duplication syndrome. This is the first report implicating RXRA in CHD with 9q duplication, providing additional data in understanding the genetic etiology of tetralogy of Fallot, CHD, and disorders linked to 9q microduplication syndrome. This report also highlights the significance of CMA in the clinical diagnosis and genetic counseling of patients and families with complex CHD.

Decoding the complex genetic causes of heart diseases using systems biology

The pace of disease gene discovery is still much slower than expected, even with the use of cost-effective DNA sequencing and genotyping technologies. It is increasingly clear that many inherited heart diseases have a more complex polygenic aetiology than previously thought. Understanding the role of gene-gene interactions, epigenetics, and non-coding regulatory regions is becoming increasingly critical in predicting the functional consequences of genetic mutations identified by genome-wide association studies and whole-genome or exome sequencing. A systems biology approach is now being widely employed to systematically discover genes that are involved in heart diseases in humans or relevant animal models through bioinformatics. The overarching premise is that the integration of high-quality causal gene regulatory networks (GRNs), genomics, epigenomics, transcriptomics and other genome-wide data will greatly accelerate the discovery of the complex genetic causes of congenital and complex heart diseases. This review summarises state-of-the-art genomic and bioinformatics techniques that are used in accelerating the pace of disease gene discovery in heart diseases. Accompanying this review, we provide an interactive web-resource for systems biology analysis of mammalian heart development and diseases, CardiacCode ( http://CardiacCode.victorchang.edu.au/ ). CardiacCode features a dataset of over 700 pieces of manually curated genetic or molecular perturbation data, which enables the inference of a cardiac-specific GRN of 280 regulatory relationships between 33 regulator genes and 129 target genes. We believe this growing resource will fill an urgent unmet need to fully realise the true potential of predictive and personalised genomic medicine in tackling human heart disease.