The role of DNA methylation in syndromic and non-syndromic congenital heart disease

Untangling the gordian knot: The intertwining interactions between developmental hormone signaling and epigenetic mechanisms in insects

Hormones control developmental and physiological processes, often by regulating the expression of multiple genes simultaneously or sequentially. Crosstalk between hormones and epigenetics is pivotal to dynamically coordinate this process. Hormonal signals can guide the addition and removal of epigenetic marks, steering gene expression. Conversely, DNA methylation, histone modifications and non-coding RNAs can modulate regional chromatin structure and accessibility and regulate the expression of numerous (hormone-related) genes. Here, we provide a review of the interplay between the classical insect hormones, ecdysteroids and juvenile hormones, and epigenetics. We summarize the mode-of-action and roles of these hormones in post-embryonic development, and provide a general overview of epigenetic mechanisms. We then highlight recent advances on the interactions between these hormonal pathways and epigenetics, and their involvement in development. Furthermore, we give an overview of several 'omics techniques employed in the field. Finally, we discuss which questions remain unanswered and possible avenues for future research.

DNMT3A promotes glioma growth and malignancy via TNF-α/NF-κB signaling pathway

Background

DNMT3A is the main molecule responsible for DNA methylation in cells. DNMT3A affects the progression of inflammation, degenerative diseases, and malignant tumors, and exhibits significant aberrantly expression in tumor tissues.

Methods

Transcriptome data and relevant clinical information were downloaded from The Cancer Genome Atlas (TCGA), Chinese Glioma Genome Atlas (CGGA), and Gene Expression Omnibus (GEO) datasets. Differential expression analysis and prognostic analysis were conducted based on above statistics. We constructed a clinical prognostic model and identified DNMT3A as an independent prognostic factor to accurately predict patient prognosis. Differential gene enrichment analysis revealed that DNMT3A affects the progression of glioma through multiple pathways, among which the tumor necrosis factor-α (TNF-α)/nuclear factor-kappa B (NF-κB) pathway shows a strong correlation. Immunological analysis also revealed a certain correlation between DNMT3A and tumor immunity. We demonstrated through gene editing that DNMT3A can affect the release of TNF-α in cells, thereby affecting the progression of glioma. Functional experiments have also demonstrated that DNMT3A plays a crucial role in tumors.

Results

RNA-sequencing and survival analyses of lower-grade glioma (LGG) patients in TCGA, CGGA, and GEO cohorts showed that high DNMT3A expression correlated with poor prognosis of LGG patients. Univariate and multivariate Cox regression analyses showed that DNMT3A expression was an independent prognostic indicator in LGG. The prognosis prediction nomogram with age, World Health Organization (WHO) grading, and DNMT3A expression showed reliable performance in predicting the 1-, 3-, and 5-year overall survival (OS) of LGG patients. Functional enrichment analysis, gene set enrichment analysis (GSEA), and ESTIMATE algorithm analyses showed that DNMT3A expression was associated with the tumor infiltration of immune cells and predicted response to immunotherapy in two immunotherapy cohorts of pan-cancer patients. Furthermore, short hairpin RNA (shRNA)-mediated knockdown of DNMT3A in the LGG cell lines suppressed proliferation, migration, and invasion of LGG cells by downregulating the TNF-α/NF-κB signaling pathway.

Conclusions

Our data showed that DNMT3A was a potential prognostic biomarker in glioma. DNMT3A promoted proliferation and malignancy of LGG cells through the TNF-α/NF-κB signaling pathway. DNMT3A is a promising therapeutic target for treating patients with LGG.

Post-translational modifications of vertebrate striated muscle myosin heavy chains

Post-translational modifications (PTMs) play a crucial role in regulating the function of many sarcomeric proteins, including myosin. Myosins comprise a family of motor proteins that play fundamental roles in cell motility in general and muscle contraction in particular. A myosin molecule consists of two myosin heavy chains (MyHCs) and two pairs of myosin light chains (MLCs); two MLCs are associated with the neck region of each MyHC's N-terminal head domain, while the two MyHC C-terminal tails form a coiled-coil that polymerizes with other MyHCs to form the thick filament backbone. Myosin undergoes extensive PTMs, and dysregulation of these PTMs may lead to abnormal muscle function and contribute to the development of myopathies and cardiovascular disorders. Recent studies have uncovered the significance of PTMs in regulating MyHC function and showed how these PTMs may provide additional modulation of contractile processes. Here, we discuss MyHC PTMs that have been biochemically and/or functionally studied in mammals' and rodents' striated muscle. We have identified hotspots or specific regions in three isoforms of myosin (MYH2, MYH6, and MYH7) where the prevalence of PTMs is more frequent and could potentially play a significant role in fine-tuning the activity of these proteins.

Identification of miR-20b-5p as an inhibitory regulator in cardiac differentiation via TET2 and DNA hydroxymethylation

BACKGROUND

Congenital heart disease (CHD) is a prevalent congenital cardiac malformation, which lacks effective early biological diagnosis and intervention. MicroRNAs, as epigenetic regulators of cardiac development, provide potential biomarkers for the diagnosis and treatment of CHD. However, the mechanisms underlying miRNAs-mediated regulation of cardiac development and CHD malformation remain to be further elucidated. This study aimed to explore the function of microRNA-20b-5p (miR-20b-5p) in cardiac development and CHD pathogenesis.

METHODS AND RESULTS

miRNA expression profiling identified that miR-20b-5p was significantly downregulated during a 12-day cardiac differentiation of human embryonic stem cells (hESCs), whereas it was markedly upregulated in plasma samples of atrial septal defect (ASD) patients. Our results further revealed that miR-20b-5p suppressed hESCs-derived cardiac differentiation by targeting tet methylcytosine dioxygenase 2 (TET2) and 5-hydroxymethylcytosine, leading to a reduction in key cardiac transcription factors including GATA4, NKX2.5, TBX5, MYH6 and cTnT. Additionally, knockdown of TET2 significantly inhibited cardiac differentiation, which could be partially restored by miR-20b-5p inhibition.

CONCLUSIONS

Collectively, this study provides compelling evidence that miR-20b-5p functions as an inhibitory regulator in hESCs-derived cardiac differentiation by targeting TET2, highlighting its potential as a biomarker for ASD.

Rescuing lung development through embryonic inhibition of histone acetylation

A major barrier to the impact of genomic diagnosis in patients with congenital malformations is the lack of understanding regarding how sequence variants contribute to disease pathogenesis and whether this information could be used to generate patient-specific therapies. Congenital diaphragmatic hernia (CDH) is among the most common and severe of all structural malformations; however, its underlying mechanisms are unclear. We identified loss-of-function sequence variants in the epigenomic regulator gene SIN3A in two patients with complex CDH. Tissue-specific deletion of Sin3a in mice resulted in defects in diaphragm development, lung hypoplasia, and pulmonary hypertension, the cardinal features of CDH and major causes of CDH-associated mortality. Loss of SIN3A in the lung mesenchyme resulted in reduced cellular differentiation, impaired cell proliferation, and increased DNA damage. Treatment of embryonic Sin3a mutant mice with anacardic acid, an inhibitor of histone acetyltransferase, reduced DNA damage, increased cell proliferation and differentiation, improved lung and pulmonary vascular development, and reduced pulmonary hypertension. These findings demonstrate that restoring the balance of histone acetylation can improve lung development in the Sin3a mouse model of CDH.

Biological Age in Congenital Heart Disease-Exploring the Ticking Clock

Over the past 50 years, there has been a major shift in age distribution of patients with congenital heart disease (CHD) thanks to significant advancements in medical and surgical treatment. Patients with CHD are, however, never cured and face unique challenges throughout their lives. In this review, we discuss the growing data suggesting accelerated aging in this population. Adults with CHD are more often and at a younger age confronted with age-related cardiovascular complications such as heart failure, arrhythmia, and coronary artery disease. These can be related to the original birth defect, complications of correction, or any residual defects. In addition, and less deductively, more systemic age-related complications are seen earlier, such as renal dysfunction, lung disease, dementia, stroke, and cancer. The occurrence of these complications at a younger age makes it imperative to further map out the aging process in patients across the spectrum of CHD. We review potential feasible markers to determine biological age and provide an overview of the current data. We provide evidence for an unmet need to further examine the aging paradigm as this stresses the higher need for care and follow-up in this unique, newly aging population. We end by exploring potential approaches to improve lifespan care.

CRISPR-based epigenome editing: mechanisms and applications

Epigenomic anomalies contribute significantly to the development of numerous human disorders. The development of epigenetic research tools is essential for understanding how epigenetic marks contribute to gene expression. A gene-editing technique known as CRISPR (clustered regularly interspaced short palindromic repeats) typically targets a particular DNA sequence using a guide RNA (gRNA). CRISPR/Cas9 technology has been remodeled for epigenome editing by generating a 'dead' Cas9 protein (dCas9) that lacks nuclease activity and juxtaposing it with an epigenetic effector domain. Based on fusion partners of dCas9, a specific epigenetic state can be achieved. CRISPR-based epigenome editing has widespread application in drug screening, cancer treatment and regenerative medicine. This paper discusses the tools developed for CRISPR-based epigenome editing and their applications.

Development of Biocompatible 3D-Printed Artificial Blood Vessels through Multidimensional Approaches

Within the human body, the intricate network of blood vessels plays a pivotal role in transporting nutrients and oxygen and maintaining homeostasis. Bioprinting is an innovative technology with the potential to revolutionize this field by constructing complex multicellular structures. This technique offers the advantage of depositing individual cells, growth factors, and biochemical signals, thereby facilitating the growth of functional blood vessels. Despite the challenges in fabricating vascularized constructs, bioprinting has emerged as an advance in organ engineering. The continuous evolution of bioprinting technology and biomaterial knowledge provides an avenue to overcome the hurdles associated with vascularized tissue fabrication. This article provides an overview of the biofabrication process used to create vascular and vascularized constructs. It delves into the various techniques used in vascular engineering, including extrusion-, droplet-, and laser-based bioprinting methods. Integrating these techniques offers the prospect of crafting artificial blood vessels with remarkable precision and functionality. Therefore, the potential impact of bioprinting in vascular engineering is significant. With technological advances, it holds promise in revolutionizing organ transplantation, tissue engineering, and regenerative medicine. By mimicking the natural complexity of blood vessels, bioprinting brings us one step closer to engineering organs with functional vasculature, ushering in a new era of medical advancement.

Epigenomic signature of major congenital heart defects in newborns with Down syndrome

BACKGROUND

Congenital heart defects (CHDs) affect approximately half of individuals with Down syndrome (DS), but the molecular reasons for incomplete penetrance are unknown. Previous studies have largely focused on identifying genetic risk factors associated with CHDs in individuals with DS, but comprehensive studies of the contribution of epigenetic marks are lacking. We aimed to identify and characterize DNA methylation differences from newborn dried blood spots (NDBS) of DS individuals with major CHDs compared to DS individuals without CHDs.

METHODS

We used the Illumina EPIC array and whole-genome bisulfite sequencing (WGBS) to quantitate DNA methylation for 86 NDBS samples from the California Biobank Program: (1) 45 DS-CHD (27 female, 18 male) and (2) 41 DS non-CHD (27 female, 14 male). We analyzed global CpG methylation and identified differentially methylated regions (DMRs) in DS-CHD versus DS non-CHD comparisons (both sex-combined and sex-stratified) corrected for sex, age of blood collection, and cell-type proportions. CHD DMRs were analyzed for enrichment in CpG and genic contexts, chromatin states, and histone modifications by genomic coordinates and for gene ontology enrichment by gene mapping. DMRs were also tested in a replication dataset and compared to methylation levels in DS versus typical development (TD) WGBS NDBS samples.

RESULTS

We found global CpG hypomethylation in DS-CHD males compared to DS non-CHD males, which was attributable to elevated levels of nucleated red blood cells and not seen in females. At a regional level, we identified 58, 341, and 3938 CHD-associated DMRs in the Sex Combined, Females Only, and Males Only groups, respectively, and used machine learning algorithms to select 19 Males Only loci that could distinguish CHD from non-CHD. DMRs in all comparisons were enriched for gene exons, CpG islands, and bivalent chromatin and mapped to genes enriched for terms related to cardiac and immune functions. Lastly, a greater percentage of CHD-associated DMRs than background regions were differentially methylated in DS versus TD samples.

CONCLUSIONS

A sex-specific signature of DNA methylation was detected in NDBS of DS-CHD compared to DS non-CHD individuals. This supports the hypothesis that epigenetics can reflect the variability of phenotypes in DS, particularly CHDs.

Linking environmental risk factors with epigenetic mechanisms in Parkinson's disease

Sporadic Parkinson's disease (PD) is a progressive neurodegenerative disease, with a complex risk structure thought to be influenced by interactions between genetic variants and environmental exposures, although the full aetiology is unknown. Environmental factors, including pesticides, have been reported to increase the risk of developing the disease. Growing evidence suggests epigenetic changes are key mechanisms by which these environmental factors act upon gene regulation, in disease-relevant cell types. We present a systematic review critically appraising and summarising the current body of evidence of the relationship between epigenetic mechanisms and environmental risk factors in PD to inform future research in this area. Epigenetic studies of relevant environmental risk factors in animal and cell models have yielded promising results, however, research in humans is just emerging. While published studies in humans are currently relatively limited, the importance of the field for the elucidation of molecular mechanisms of pathogenesis opens clear and promising avenues for the future of PD research. Carefully designed epidemiological studies carried out in PD patients hold great potential to uncover disease-relevant gene regulatory mechanisms. Therefore, to advance this burgeoning field, we recommend broadening the scope of investigations to include more environmental exposures, increasing sample sizes, focusing on disease-relevant cell types, and recruiting more diverse cohorts.

Epigenomic signature of major congenital heart defects in newborns with Down syndrome

Background

Congenital heart defects (CHDs) affect approximately half of individuals with Down syndrome (DS) but the molecular reasons for incomplete penetrance are unknown. Previous studies have largely focused on identifying genetic risk factors associated with CHDs in individuals with DS, but comprehensive studies of the contribution of epigenetic marks are lacking. We aimed to identify and characterize DNA methylation differences from newborn dried blood spots (NDBS) of DS individuals with major CHDs compared to DS individuals without CHDs.

Methods

We used the Illumina EPIC array and whole-genome bisulfite sequencing (WGBS) to quantitate DNA methylation for 86 NDBS samples from the California Biobank Program: 1) 45 DS-CHD (27 female, 18 male) and 2) 41 DS non-CHD (27 female, 14 male). We analyzed global CpG methylation and identified differentially methylated regions (DMRs) in DS-CHD vs DS non-CHD comparisons (both sex-combined and sex-stratified) corrected for sex, age of blood collection, and cell type proportions. CHD DMRs were analyzed for enrichment in CpG and genic contexts, chromatin states, and histone modifications by genomic coordinates and for gene ontology enrichment by gene mapping. DMRs were also tested in a replication dataset and compared to methylation levels in DS vs typical development (TD) WGBS NDBS samples.

Results

We found global CpG hypomethylation in DS-CHD males compared to DS non-CHD males, which was attributable to elevated levels of nucleated red blood cells and not seen in females. At a regional level, we identified 58, 341, and 3,938 CHD-associated DMRs in the Sex Combined, Females Only, and Males Only groups, respectively, and used machine learning algorithms to select 19 Males Only loci that could distinguish CHD from non-CHD. DMRs in all comparisons were enriched for gene exons, CpG islands, and bivalent chromatin and mapped to genes enriched for terms related to cardiac and immune functions. Lastly, a greater percentage of CHD-associated DMRs than background regions were differentially methylated in DS vs TD samples.

Conclusions

A sex-specific signature of DNA methylation was detected in NDBS of DS-CHD compared to DS non-CHD individuals. This supports the hypothesis that epigenetics can reflect the variability of phenotypes in DS, particularly CHDs.

Mitochondrial miRNA as epigenomic signatures: Visualizing aging-associated heart diseases through a new lens

Aging bears many hard knocks, but heart disorders earn a particular allusion, being the most widespread. Cardiovascular diseases (CVDs) are becoming the biggest concern to mankind due to sundry health conditions directly or indirectly related to heart-linked abnormalities. Scientists know that mitochondria play a critical role in the pathophysiology of cardiac diseases. Both environment and genetics play an essential role in modulating and controlling mitochondrial functions. Even a minor abnormality may prove detrimental to heart function. Advanced age combined with an unhealthy lifestyle can cause most cardiomyocytes to be replaced by fibrotic tissue which upsets the conducting system and leads to arrhythmias. An aging heart encounters far more heart-associated comorbidities than a young heart. Many state-of-the-art technologies and procedures are already being used to prevent and treat heart attacks worldwide. However, it remains a mystery when this heart bomb would explode because it lacks an alarm. This calls for a novel and effective strategy for timely diagnosis and a sure-fire treatment. This review article provides a comprehensive overture of prospective potentials of mitochondrial miRNAs that predict complicated and interconnected pathways concerning heart ailments and signature compilations of relevant miRNAs as biomarkers to plot the role of miRNAs in epigenomics. This article suggests that analysis of DNA methylation patterns in age-associated heart diseases may determine age-impelled biomarkers of heart disease.

Genome-wide DNA methylation analysis of discordant monozygotic twins reveals consistent sites of differential methylation associated with congenital heart disease

BACKGROUND

Despite being essentially genetically identical, monozygotic (MZ) twins can be discordant for congenital heart disease (CHD), thus highlighting the importance of in utero environmental factors for CHD pathogenesis. This study aimed to identify the epigenetic variations between discordant MZ twin pairs that are associated with CHD at birth.

METHODS

Cord blood of CHD-discordant MZ twins from the Chongqing Longitudinal Twin Study Cohort was subjected to whole-genome bisulfite sequencing, then validated by MeDIP-qPCR and qRT-PCR.

RESULTS

379 DMRs mapped to 175 differentially methylated genes (DMGs) were associated with CHD. Functional enrichment analysis identified these DMGs are involved in histone methylation, actin cytoskeleton organization, the regulation of cell differentiation, and adrenergic signaling in cardiomyocytes. Of note, SPESP1 and NOX5 were hypermethylated in CHD, and associated with lower gene expression levels.

CONCLUSIONS

Specific DNA methy (DNAm) variations in cord blood were associated with CHD, thus illustrating new biomarkers and potential interventional targets for CHD.

TRIAL REGISTRATION

ChiCTR-OOC-16008203, registered on 1 April 2016 at the Chinese Clinical Trial Registry.

DNMT3B rs2424913 as a Risk Factor for Congenital Heart Defects in Down Syndrome

Impairments of the genes that encode enzymes that are involved in one-carbon metabolism because of the presence of gene polymorphisms can affect the methylation pattern. The altered methylation profiles of the genes involved in cardiogenesis may result in congenital heart defects (CHDs). The aim of this study was to investigate the association between the MTHFR rs1801133, MTHFR rs1801131, MTRR rs1801394, DNMT1 rs2228611, DNMT3A rs1550117, DNMT3B rs1569686, and DNMT3B rs2424913 gene polymorphisms and congenital heart defects in Down syndrome (DS) individuals. The study was conducted on 350 participants, including 134 DS individuals with CHDs (DSCHD+), 124 DS individuals without CHDs (DSCHD−), and 92 individuals with non-syndromic CHD. The genotyping was performed using the PCR–RFLP method. A statistically significant higher frequency of the DNMT3B rs2424913 TT in the DSCHD+ individuals was observed. The DNMT3B rs2424913 TT genotype, as well as the T allele, had significantly higher frequencies in the individuals with DS and atrial septal defects (ASDs) in comparison with the individuals with DS and other CHDs. Furthermore, our results indicate a statistically significant effect of the DNMT3B rs1569686 TT genotype in individuals with non-syndromic CHDs. The results of the study suggest that the DNMT3B rs2424913 TT genotypes may be a possible predisposing factor for CHDs in DS individuals, and especially those with ASDs.

Association of Maternal Betaine-Homocysteine Methyltransferase (BHMT) and BHMT2 Genes Polymorphisms with Congenital Heart Disease in Offspring

To systematically explore the association of single nucleotide polymorphisms (SNPs) of maternal BHMT and BHMT2 genes with the risk of congenital heart disease (CHD) and its three subtypes including atrial septal defect (ASD), ventricular septal defect (VSD), and patent ductus arteriosus (PDA) in offspring. A hospital-based case-control study involving 683 mothers of CHD children and 740 controls was performed. Necessary exposure information was captured through epidemiological investigation. Totally twelve SNPs of maternal BHMT and BHMT2 genes were detected and analyzed systematically. The study showed that maternal BHMT gene polymorphisms at rs1316753 (CG vs. CC: OR = 1.96 [95% CI 1.41-2.71]; GG vs. CC: OR = 1.99 [95% CI 1.32-3.00]; dominant model: OR = 1.97 [95% CI 1.44-2.68]) and rs1915706 (TC vs. TT: OR = 1.93 [95% CI 1.44-2.59]; CC vs. TT: OR = 2.55 [95% CI 1.38-4.72]; additive model: OR = 1.77 [95% CI 1.40-2.24]) were significantly associated with increased risk of total CHD in offspring. And two haplotypes were observed to be significantly associated with risk of total CHD, including C-C haplotype involving rs1915706 and rs3829809 in BHMT gene (OR = 1.30 [95% CI 1.07-1.58]) and C-A-A-C haplotype involving rs642431, rs592052, rs626105, and rs682985 in BHMT2 gene (OR = 0.71 [95% CI 0.58-0.88]). Besides, a three-locus model involving rs1316753 (BHMT), rs1915706 (BHMT), and rs642431 (BHMT2) was identified through gene-gene interaction analyses (P < 0.01). As for three subtypes including ASD, VSD, and PDA, significant SNPs and haplotypes were also identified. The results indicated that maternal BHMT gene polymorphisms at rs1316753 and rs1915706 are significantly associated with increased risk of total CHD and its three subtypes in offspring. Besides, significant interactions between different SNPs do exist on risk of CHD. Nevertheless, studies with larger sample size in different ethnic populations and involving more SNPs in more genes are expected to further define the genetic contribution underlying CHD and its subtypes.

Neonatal frontal-limbic connectivity is associated with externalizing behaviours in toddlers with Congenital Heart Disease

Children with Congenital Heart Disease (CHD) are at increased risk of neurodevelopmental impairments. The neonatal antecedents of impaired behavioural development are unknown. 43 infants with CHD underwent presurgical brain diffusion-weighted MRI [postmenstrual age at scan median (IQR) = 39.29 (38.71-39.71) weeks] and a follow-up assessment at median age of 22.1 (IQR 22.0-22.7) months in which parents reported internalizing and externalizing problem scores on the Child Behaviour Checklist. We constructed structural brain networks from diffusion-weighted MRI and calculated edge-wise structural connectivity as well as global and local brain network features. We also calculated presurgical cerebral oxygen delivery, and extracted perioperative variables, socioeconomic status at birth and a measure of cognitively stimulating parenting. Lower degree in the right inferior frontal gyrus (partial ρ = -0.687, p < 0.001) and reduced connectivity in a frontal-limbic sub-network including the right inferior frontal gyrus were associated with higher externalizing problem scores. Externalizing problem scores were unrelated to neonatal clinical course or home environment. However, higher internalizing problem scores were associated with earlier surgery in the neonatal period (partial ρ = -0.538, p = 0.014). Our results highlight the importance of frontal-limbic networks to the development of externalizing behaviours and provide new insights into early antecedents of behavioural impairments in CHD.

Association and Interaction Effect of BHMT Gene Polymorphisms and Maternal Dietary Habits with Ventricular Septal Defect in Offspring

This study attempted to learn the association between maternal betaine-homocysteine methyltransferase (BHMT) gene polymorphisms, maternal dietary habits, and their interactions with the risk of ventricular septal defects (VSD) in offspring. A total of 426 mothers of VSD children and 740 control mothers were included in the study. Logistic regression was used to evaluate the level of associations and interaction effects. Our study suggested that mothers reporting excessive intake of smoked foods (aOR = 2.44, 95%CI: 1.89–3.13), barbecued foods (aOR = 1.86, 95%CI: 1.39–2.48), fried foods (aOR = 1.93, 95%CI: 1.51–2.46), and pickled vegetables (aOR = 2.50, 95%CI: 1.92–3.25) were at a significantly higher risk of VSD in offspring, instead, mothers reporting regular intake of fresh fruits (aOR = 0.47, 95%CI: 0.36–0.62), fish and shrimp (aOR = 0.35, 95%CI: 0.28–0.44), fresh eggs, (aOR = 0.56, 95%CI: 0.45–0.71), beans (aOR = 0.68, 95%CI: 0.56–0.83), and milk products (aOR = 0.67, 95%CI: 0.56–0.80) were at a lower risk of VSD in offspring. In addition, maternal BHMT gene polymorphisms at rs1316753 (CG vs. CC: aOR = 2.01, 95%CI: 1.43–2.83) and rs1915706 (CT vs. TT: (aOR = 1.81, 95%CI: 1.33–2.46) were significantly associated with increased risk of VSD in offspring. Furthermore, a significant interaction between BHMT polymorphisms and maternal bean intake was identified in the study. In conclusion, Maternal BHMT polymorphisms at rs1316753 and rs1915706, dietary habits as well as their interaction were observed to be significantly associated with the risk of VSD in offspring.

Accelerated Cardiac Aging in Patients With Congenital Heart Disease

An increasing number of patients with congenital heart disease (CHD) survive into adulthood but develop long-term complications including heart failure (HF). Cellular senescence, classically defined as stable cell cycle arrest, is implicated in biological processes such as embryogenesis, wound healing, and aging. Senescent cells have a complex senescence-associated secretory phenotype (SASP), involving a range of pro-inflammatory factors with important paracrine and autocrine effects on cell and tissue biology. While senescence has been mainly considered as a cause of diseases in the adulthood, it may be also implicated in some of the poor outcomes seen in patients with complex CHD. We propose that patients with CHD suffer from multiple repeated stress from an early stage of the life, which wear out homeostatic mechanisms and cause premature cardiac aging, with this term referring to the time-related irreversible deterioration of the organ physiological functions and integrity. In this review article, we gathered evidence from the literature indicating that growing up with CHD leads to abnormal inflammatory response, loss of proteostasis, and precocious age in cardiac cells. Novel research on this topic may inspire new therapies preventing HF in adult CHD patients.

Epigenetic Effect of Maternal Methyl-Group Donor Intake on Offspring’s Health and Disease

Maternal exposure to some dietary and environmental factors during embryonic development can affect offspring’s phenotype and, furthermore, the risk of developing diseases later in life. One potential mechanism responsible for this early programming may be the modification of the epigenome, such as DNA methylation. Methyl-group donors are essential for DNA methylation and are shown to have an important role in fetal development and later health. The main goal of the present review is to summarize the available literature data on the epigenetic effect (DNA methylation) of maternal methyl-group donor availability on reproductivity, perinatal outcome, and later health of the offspring. In our literature search, we found evidence for the association between alterations in DNA methylation patterns caused by different maternal methyl-group donor (folate, choline, methionine, betaine) intake and reproductivity, birth weight, neural tube defect, congenital heart defect, cleft lip and palate, brain development, and the development of obesity and associated non-communicable diseases in later life. We can conclude that maternal methyl-group donor availability could affect offspring’s health via alterations in DNA methylation and may be a major link between early environmental exposure and the development of diseases in the offspring. However, still, further studies are necessary to confirm the associations and causal relationships.

"The study of expression levels of DNA methylation regulators in patients affected with congenital heart defects (CHDs)"

BACKGROUND

Congenial heart defects (CHDs) have multifactorial etiology with complex interplay of genetic and environmental factors. Environmental impact can have epigenetic mechanism of CHD development. Many studies have reported the causal association between CHD and distinct DNA methylation profile which is one of the key epigenetic events, which has vital role in normal embryonic development. The products of DNMT1, DNMT3A, DNMT3B, and MBD2 are important regulators of DNA methylation process. Changes in the expression of these genes are implicated in congenital structural cardiac defects. Hence, in this proof-of-concept study, we have compared the expression levels of these genes in the blood samples of healthy controls and CHD cases while investigating the etiology of CHD.

METHODS

In this study with 48 CHD cases and 47 healthy controls, total RNA was isolated from the whole blood samples using TRI reagent. Quantitative RT PCR (qRT-PCR) was used to analyze the mRNA levels of DNMT1, DNMT3A, DNMT3B, and MBD2. The expression levels have been analyzed by relative quantification.

RESULTS

We observed that DNMT3B (fold change = -2.563; p = .0018) and DNMT3A (fold change = -2.169; p = .05) were significantly downregulated in CHD patients, whereas the expression of DNMT1 and MBD2 was not significantly different between cases and controls.

CONCLUSIONS

Lower expression of de novo methyltransferases, namely, DNMT3B and DNMT3A in CHD cases, may be an important contributor to the mechanism of CHD pathogenesis. Further studies with age-matched controls and analysis of global DNA methylation profile are required to investigate the proposed causal association.

CpG site hypomethylation at ETS1‑binding region regulates DLK1 expression in Chinese patients with Tetralogy of Fallot

Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart malformation accounting for ~10% of cases. Although the pathogenesis of TOF is complex and largely unknown, epigenetics plays a huge role, specifically DNA methylation. The protein δ like non-canonical Notch ligand 1 (DLK1) gene encodes a non-canonical ligand of the Notch signaling pathway, which is involved in heart development. However, the epigenetic mechanism of DLK1 in the pathogenesis of TOF is yet to be elucidated. Therefore, the present study aimed to clarify its specific mechanism. In this study, immunohistochemistry was used to detect the protein expression of DLK1 and the methylation status of the DLK1 promoter was measured via bisulfite sequencing PCR. Dual-luciferase reporter assays were performed to examine the influence of transcription factor ETS proto-oncogene 1 (ETS1) on DLK1 gene expression. The electrophoretic mobility shift assay and chromatin immunoprecipitation assay, both in vivo and in vitro, were used to verify the binding of the ETS1 transcription factor to the DLK1 promoter as well as the influence of methylation status of DLK1 promoter on this binding affinity. The expression of DLK1 in the right ventricular outflow tract was significantly lower in patients with Tetralogy of Fallot (TOF) than that in controls (P<0.001). Moreover, the methylation level of CpG site 10 and CpG site 11 in the DLK1_R region was significantly decreased in TOF cases compared with controls (P<0.01). The integral methylation levels of DLK1_R and the methylation status of the CpG site 11 were both positively associated with DLK1 protein expression in TOF cases. ETS1 was found to inhibit DLK1 transcriptional activity by binding to the CpG site 11 and this affinity could be influenced by the methylation level of the DLK1 promoter. These findings demonstrated that the hypomethylation of the DLK1 promoter could increase the binding affinity of ETS1 transcription factor, which in turn inhibited DLK1 gene transcriptional activity and contributed to the development of TOF.

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.

Epidemiology, Genetics and Epigenetics of Congenital Heart Diseases in Twins

Congenital heart defects (CHDs) refer to abnormalities in the heart function that arise at the fetal stages. It is the most common birth defect that affects 0.8% of all liveborn infants. There is an increase in the incidence of congenital heart disease in monochorionic twin gestation. A six-fold increase in CHDs exists among monochorionic twins especially in association with twin-twin transfusion syndrome (TTTS) compared to dichorionic twin pregnancy. In this review article, we discussed the epidemiology, the role of genetics like protein-coding genes, epigenetics, placenta, hemodynamics and environmental factors in the etiology of CHD in twins.

We conducted a literature search in PubMed indexed journals using the medical terms "twin pregnancy" and "congenital heart defect" to provide an overview of the uptrend in CHD in twin pregnancies, primarily due to assisted reproductive technologies (ARTs) and multiple other factors. Both the heart and placenta are vascular and share a common development window; therefore, CHD can develop secondary to placental pathologies. Among environmental factors, the strongest association of maternal smoking with CHD has been seen. We studied the causative factors to suggest improvement in echocardiographic skills in case of abnormal findings in twin gestations to decrease the CHD-associated morbidity and mortality, as early diagnosis allows doctors to precisely determine the risk of CHD. Systemic ultrasound scanning with five transverse views is very effective in diagnosing fetal CHD in twin pregnancy. In the case of genetics, prenatal counseling allows the expectant to understand the full ramifications of possible events after the pregnancy. The pathological basis of malformations specific to conjoined twinning and twin reversed arterial perfusion sequence is addressed. Also, there is evidence that folate supplementation may be protective against CHD but more research is needed to clarify the mechanisms.

We concluded from the literature that monochorionic twins are at high risk of CHD. Chorionicity seems to play a more vital role than zygosity. Even the type of heart defect in monochorial twin pregnancies was unique from single, dizygotic, or dichorionic twin pregnancies. We also emphasize improving echocardiographic skills of technicians in referring ART dichorionic twin fetuses with suspicious findings to fetal cardiologists and performing postnatal scans in the case of TTTS. To understand the role of the placenta, making use of newer technologies and examining the placenta both during pregnancy and beyond delivery will play a vital role in understanding the etiology. Even identifying early signals impacting the heart and placental vasculature and correcting them using advanced technology could downtrend the incidence in coming years. Increased maternal age as well as multiple pregnancies increasing the risk of CHD has also been implicated. For more clarity on the role of genetics, the cost of DNA sequencing needs to decrease. This will enable whole-genome sequencing in the future thus helping to discover the gene responsible for CHD ultimately proving beneficial for future generations. For environmental factors, we have to rely on observational studies to assess the risk to the unborn child. There is difficulty in studying natural factors due to the unreliability of exposure to contaminants like pesticides and air pollution.