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

Maternal obesity and metabolic disorders associate with congenital heart defects in the offspring: A systematic review

BACKGROUND

Congenital heart defects (CHDs) are the most common congenital malformations. The aetiology of CHDs is complex. Large cohort studies and systematic reviews and meta-analyses based on these have reported an association between higher risk of CHDs in the offspring and individual maternal metabolic disorders such as obesity, diabetes, hypertension, and preeclampsia, all conditions that can be related to insulin resistance or hyperglycaemia. However, the clinical reality is that these conditions often occur simultaneously. The aim of this review is, in consequence, both to evaluate the existing evidence on the association between maternal metabolic disorders, defined as obesity, diabetes, hypertension, preeclampsia, dyslipidaemia and CHDs in the offspring, as well as the significance of combinations, such as metabolic syndrome, as risk factors.

METHODS

A systematic literature search of papers published between January 1, 1990 and January 14, 2021 was conducted using PubMed and Embase. Studies were eligible if they were published in English and were case-control or cohort studies. The exposures of interest were maternal overweight or obesity, hypertension, preeclampsia, diabetes, dyslipidaemia, and/or metabolic syndrome, and the outcome of interest was CHDs in the offspring. Furthermore, the studies were included according to a quality assessment score.

RESULTS

Of the 2,250 identified studies, 32 qualified for inclusion. All but one study investigated only the individual metabolic disorders. Some disorders (obesity, gestational diabetes, and hypertension) increased risk of CHDs marginally whereas pre-gestational diabetes and early-onset preeclampsia were strongly associated with CHDs, without consistent differences between CHD subtypes. A single study suggested a possible additive effect of maternal obesity and gestational diabetes.

CONCLUSIONS

Future studies of the role of aberrations of the glucose-insulin homeostasis in the common aetiology and mechanisms of metabolic disorders, present during pregnancy, and their association, both as single conditions and-particularly-in combination, with CHDs are needed.

Congenital Rubella: A Salient Cause of Congenital Heart Defects in Infants

BACKGROUND

Structural congenital heart defects (CHD) take a huge toll of congenital defects in children in India. Limited information is available regarding modifiable risk factors for its causation. This study was planned with an aim to determine the prevalence of congenital rubella infection in Indian infants with structural CHD's.

METHODOLOGY

This cross-sectional, observational study was conducted at a tertiary care hospital in Northern India over 1 year period (1 July 2016 to 30 June 2017). Infants <6 months with structural CHD were enrolled after taking informed consent from their mothers. Blood samples were collected from mother-child binomials and tested for rubella IgM and IgG antibodies.

RESULTS

A total of 80 infants (M : F = 56 : 24), having mean age 69.4 (±56.5) days; were enrolled. In these infants, prevalence of congenital rubella infection (either infant's IgM rubella positive or infant's IgG rubella titers higher than mother's) was 8.75% (7/80). A total of 12.5% of studied mothers were seronegative for rubella IgG antibodies. Statistically significant association was found between the occurrence of congenital rubella and cataract (p = 0.0039), splenomegaly (p = 0.007) and microcephaly (p = 0.0084) in infants having structural CHD.

CONCLUSIONS

Congenital rubella syndrome still remains an important modifiable cause for structural CHD in India. Sincere efforts for rubella elimination via further strengthening current vaccination strategy would help in decreasing burden of structural CHD in India.

Screening of 22q11.2DS Using Multiplex Ligation-Dependent Probe Amplification as an Alternative Diagnostic Method

Background

The 22q11.2 deletion syndrome (22q11.2DS) is the most common form of deletion disorder in humans. Low copy repeats flanking the 22q11.2 region confers a substrate for nonallelic homologous recombination (NAHR) events leading to rearrangements which have been reported to be associated with highly variable and expansive phenotypes. The 22q11.2DS is reported as the most common genetic cause of congenital heart defects (CHDs).

Methods

A total of 42 patients with congenital heart defects, as confirmed by echocardiography, were recruited. Genetic molecular analysis using a fluorescence in situ hybridization (FISH) technique was conducted as part of routine 22q11.2DS screening, followed by multiplex ligation-dependent probe amplification (MLPA), which serves as a confirmatory test.

Results

Two of the 42 CHD cases (4.76%) indicated the presence of 22q11.2DS, and interestingly, both cases have conotruncal heart defects. In terms of concordance of techniques used, MLPA is superior since it can detect deletions within the 22q11.2 locus and outside of the typically deleted region (TDR) as well as duplications.

Conclusion

The incidence of 22q11.2DS among patients with CHD in the east coast of Malaysia is 0.047. MLPA is a scalable and affordable alternative molecular diagnostic method in the screening of 22q11.2DS and can be routinely applied for the diagnosis of deletion syndromes.

Long Noncoding RNA lnc-TSSK2-8 Activates Canonical Wnt/β-Catenin Signaling Through Small Heat Shock Proteins HSPA6 and CRYAB

Congenital heart defects (CHDs) are the most common birth defects worldwide. 22q11.2 deletion syndrome is the most common microdeletion disorder that has been frequently associated with conotruncal malformations. By now, the dosage-sensitive gene TBX1 has been adopted as the major pathogenic gene responsible for 22q11.2 deletion, which is regulated by canonical Wnt/β-catenin signaling pathway in heart outflow tract development. Here, we report the long noncoding RNA (lncRNA) lnc-TSSK2-8, which is encompassed in the 22q11.2 region, that can activate canonical Wnt/β-catenin signaling by protecting β-catenin from degradation, which could result from decreased ubiquitination. Such effects were mediated by two short heat shock proteins HSPA6 and α-β-crystallin (CRYAB), whose expression was regulated by lnc-TSSK2-8 through a competing endogenous RNA (ceRNA) mechanism. In clinical practice, the pathogenesis of copy number variation (CNV) was always attributed to haploinsufficiency of protein-coding genes. Here, we report that the 22q11.2 lncRNA lnc-TSSK2-8 significantly activated canonical Wnt/β-catenin signaling, which has major roles in cardiac outflow tract development and should act upstream of TBX1. Our results suggested that lncRNAs should contribute to the etiology of CNV-related CHD.

A new era of genetic testing in congenital heart disease: A review

Genetic and genomic testing in pediatric CHD is becoming increasingly routine, and can have important psychosocial, clinical and reproductive implications. In this paper we highlight important challenges and considerations when providing genetics consults and testing in pediatric CHD and illustrate the role of a dedicated CHD genetics clinic. Key lessons include that a) a genetic diagnosis can have clinical utility that justifies testing early in life, b) adequate genetic counselling is crucial to ensure families are supported, understand the range of possible results, and are prepared for new or unexpected health information, and c) further integration of the clinical genetics and cardiology workflows will be required to effectively manage the burgeoning information arising from genetic testing. Our experience demonstrates that a dedicated CHD genetics clinic is a valuable addition to a multidisciplinary team providing care to children with CHD.

The Roles of Reduced Folate Carrier-1 (RFC1) A80G (rs1051266) Polymorphism in Congenital Heart Disease: A Meta-Analysis

Background

We performed the present study to better elucidate the correlation of reduced folate carrier-1 (RFC1) A80G (rs1051266) polymorphism with the risk of congenital heart disease (CHD).

Material/Methods

According to the designed search strategy, a systematic literature search was performed through the PubMed, Cochrane Library, Web of Science, EMBASE, CNKI, VIP, and Wan Fang databases to collect published case-control studies on the correlation between RFC1 A80G polymorphism and CHD. All relevant studies up to October 1, 2019 were identified. The odds ratio (OR) and 95% confidence interval (CI) of the genotype distribution were used as the effect indicators.

Results

A total of 6 eligible studies was finally included in our meta-analysis, including 724 children with CHD, 760 healthy children, 258 mothers of the children with CHD, and 334 mothers of healthy control children. The meta-analysis revealed that for fetal analysis, only in the heterozygous model (GA vs GG, OR=1.36, 95% CI [1.06, 1.75], P=0.02) was RFC1 A80G polymorphism associated with risk of CHD. In maternal analysis, 3 genetic models of RFC1 A80G polymorphism increased the risk of CHD: the allelic model (A vs G, OR=1.36, 95% CI [1.07, 1.71], P=0.01), the homozygote model (AA vs GG, OR=2.99, 95%CI [1.06, 8.41], P=0.04), and the dominance model (GA+AA vs GG, OR=1.53, 95%CI [1.08, 2.16], P=0.02).

Conclusions

The maternal RFC1 A80G polymorphism has a strong correlation with CHD. Compared with the G allele, the A allele increases the risk of CHD by 0.36-fold.

Common Variation in Cytoskeletal Genes is Associated with Conotruncal Heart Defects

There is strong evidence for a genetic contribution to non-syndromic congenital heart defects (CHDs). However, exome- and genome-wide studies conducted at the variant and gene-level have identified few genome-wide significant CHD-related genes. Gene-set analyses are a useful complement to such studies and candidate gene-set analyses of rare variants have provided insight into the genetics of CHDs. However, similar analyses have not been conducted using data on common genetic variants. Consequently, we conducted common variant analyses of 15 CHD candidate gene-sets, using data from two common types of CHDs: conotruncal heart defects (1431 cases) and left ventricular outflow tract defects (509 cases). After Bonferroni correction for evaluation of multiple gene-sets, the cytoskeletal gene-set was significantly associated with conotruncal heart defects (β_S = 0.09; 95% confidence interval (CI) 0.03–0.15). This association was stronger when analyses were restricted to the sub-set of cytoskeletal genes that have been observed to harbor rare damaging genotypes in at least two CHD cases (β_S = 0.32, 95% CI 0.08–0.56). These findings add to the evidence linking cytoskeletal genes to CHDs and suggest that, for cytoskeletal genes, common variation may contribute to the risk of CHDs.

Prevalence of Common Disease Conditions in a Large Cohort of Individuals With Down Syndrome in the United States

Purpose

Given the current life expectancy and number of individuals living with Down syndrome (DS), it is important to learn common occurrences of disease conditions across the developmental lifespan. This study analyzed data from a large cohort of individuals with DS in an effort to better understand these disease conditions, inform future screening practices, tailor medical care guidelines, and improve utilization of health care resources.

Methods

This retrospective, descriptive study incorporated up to 28 years of data, compiled from 6078 individuals with DS and 30,326 controls matched on age and sex. Data were abstracted from electronic medical records within a large Midwestern health system.

Results

In general, individuals with DS experienced higher prevalence of testicular cancer, leukemias, moyamoya disease, mental health conditions, bronchitis and pneumonia, gastrointestinal conditions, thyroid disorder, neurological conditions, atlantoaxial subluxation, osteoporosis, dysphagia, diseases of the eyes/adnexa and of the ears/mastoid process, and sleep apnea, relative to matched controls. Individuals with DS experienced lower prevalence of solid tumors, heart disease conditions, sexually transmitted diseases, HIV, influenza, sinusitis, urinary tract infections, and diabetes. Similar rates of prevalence were seen for lymphomas, skin melanomas, stroke, acute myocardial infarction, hepatitis, cellulitis, and osteoarthritis.

Conclusions

While it is challenging to draw a widespread conclusion about comorbidities in individuals with Down syndrome, it is safe to conclude that care for individuals with DS should not automatically mirror screening, prevention, or treatment guidelines for the general U.S. population. Rather, care for those with DS should reflect the unique needs and common comorbidities of this population.

Opportunities, barriers, and recommendations in down syndrome research

BACKGROUND

Recent advances in medical care have increased life expectancy and improved the quality of life for people with Down syndrome (DS). These advances are the result of both pre-clinical and clinical research but much about DS is still poorly understood. In 2020, the NIH announced their plan to update their DS research plan and requested input from the scientific and advocacy community.

OBJECTIVE

The National Down Syndrome Society (NDSS) and the LuMind IDSC Foundation worked together with scientific and medical experts to develop recommendations for the NIH research plan.

METHODS

NDSS and LuMind IDSC assembled over 50 experts across multiple disciplines and organized them in eleven working groups focused on specific issues for people with DS.

RESULTS

This review article summarizes the research gaps and recommendations that have the potential to improve the health and quality of life for people with DS within the next decade.

CONCLUSIONS

This review highlights many of the scientific gaps that exist in DS research. Based on these gaps, a multidisciplinary group of DS experts has made recommendations to advance DS research. This paper may also aid policymakers and the DS community to build a comprehensive national DS research strategy.

Association of Damaging Variants in Genes With Increased Cancer Risk Among Patients With Congenital Heart Disease

Importance

Patients with congenital heart disease (CHD), the most common birth defect, have increased risks for cancer. Identification of the variables that contribute to cancer risk is essential for recognizing patients with CHD who warrant longitudinal surveillance and early interventions.

Objective

To compare the frequency of damaging variants in cancer risk genes among patients with CHD and control participants and identify associated clinical variables in patients with CHD who have cancer risk variants.

Design, Setting, and Participants

This multicenter case-control study included participants with CHD who had previously been recruited to the Pediatric Cardiac Genomics Consortium based on presence of structural cardiac anomaly without genetic diagnosis at the time of enrollment. Permission to use published sequencing data from unaffected adult participants was obtained from 2 parent studies. Data were collected for this study from December 2010 to April 2019.

Exposures

Presence of rare (allele frequency, <1 × 10-5) loss-of-function (LoF) variants in cancer risk genes.

Main Outcomes and Measures

Frequency of LoF variants in cancer risk genes (defined in the Catalogue of Somatic Mutations in Cancer-Cancer Gene Consensus database), were statistically assessed by binomial tests in patients with CHD and control participants.

Results

A total of 4443 individuals with CHD (mean [range] age, 13.0 [0-84] years; 2225 of 3771 with reported sex [59.0%] male) and 9808 control participants (mean [range] age, 52.1 [1-92] years; 4967 of 9808 [50.6%] male) were included. The frequency of LoF variants in regulatory cancer risk genes was significantly higher in patients with CHD than control participants (143 of 4443 [3.2%] vs 166 of 9808 [1.7%]; odds ratio [OR], 1.93 [95% CI, 1.54-2.42]; P = 1.38 × 10-12), and among CHD genes previously associated with cancer risk (58 of 4443 [1.3%] vs 18 of 9808 [0.18%]; OR, 7.2 [95% CI, 4.2-12.2]; P < 2.2 × 10-16). The LoF variants were also nominally increased in 14 constrained cancer risk genes with high expression in the developing heart. Seven of these genes (ARHGEF12, CTNNB1, LPP, MLLT4, PTEN, TCF12, and TFRC) harbored LoF variants in multiple patients with unexplained CHD. The highest rates for LoF variants in cancer risk genes occurred in patients with CHD and extracardiac anomalies (248 of 1482 individuals [16.7%]; control: 1099 of 9808 individuals [11.2%]; OR, 1.59 [95% CI, 1.37-1.85]; P = 1.3 × 10-10) and/or neurodevelopmental delay (209 of 1393 individuals [15.0%]; control: 1099 of 9808 individuals [11.2%]; OR, 1.40 [95% CI, 1.19-1.64]; P = 9.6 × 10-6).

Conclusions and Relevance

Genotypes of CHD may account for increased cancer risks. In this cohort, damaging variants were prominent in the 216 genes that predominantly encode regulatory proteins. Consistent with their fundamental developmental functions, patients with CHD and damaging variants in these genes often had extracardiac manifestations. These data may also implicate cancer risk genes that are repeatedly varied in patients with unexplained CHD as CHD genes.

In Vivo and In Vitro Genetic Models of Congenital Heart Disease

Congenital cardiovascular malformations represent the most common type of birth defect and encompass a spectrum of anomalies that range from mild to severe. The etiology of congenital heart disease (CHD) is becoming increasingly defined based on prior epidemiologic studies that supported the importance of genetic contributors and technological advances in human genome analysis. These have led to the discovery of a growing number of disease-contributing genetic abnormalities in individuals affected by CHD. The ever-growing population of adult CHD survivors, which are the result of reductions in mortality from CHD during childhood, and this newfound genetic knowledge have led to important questions regarding recurrence risks, the mechanisms by which these defects occur, the potential for novel approaches for prevention, and the prediction of long-term cardiovascular morbidity in adult CHD survivors. Here, we will review the current status of genetic models that accurately model human CHD as they provide an important tool to answer these questions and test novel therapeutic strategies.

SOX17 loss-of-function variation underlying familial congenital heart disease

As the most prevalent form of human birth defect, congenital heart disease (CHD) contributes to substantial morbidity, mortality and socioeconomic burden worldwide. Aggregating evidence has convincingly demonstrated that genetic defects exert a pivotal role in the pathogenesis of CHD, and causative mutations in multiple genes have been causally linked to CHD. Nevertheless, CHD is of pronounced genetic heterogeneity, and the genetic components underpinning CHD in the overwhelming majority of patients remain obscure. In this research, a four-generation consanguineous family suffering from CHD transmitted in an autosomal dominant mode was recruited. By whole-exome sequencing and bioinformatics analyses as well as Sanger sequencing analyses of the family members, a new heterozygous SOX17 variation, NM_022454.4: c.553G > T; p.(Glu185*), was identified to co-segregate with CHD in the family, with complete penetrance. The nonsense variation was neither detected in 310 unrelated healthy volunteers used as controls nor retrieved in such population genetics databases as the Exome Aggregation Consortium database, Genome Aggregation Database, and the Single Nucleotide Polymorphism database. Functional assays by utilizing a dual-luciferase reporter assay system unveiled that the Glu185*-mutant SOX17 protein had no transcriptional activity on its two target genes NOTCH1 and GATA4, which have been reported to cause CHD. Furthermore, the mutation abrogated the synergistic transactivation between SOX17 and NKX2.5, another established CHD-causing transcription factor. These findings firstly indicate SOX17 loss-of-function mutation predisposes to familial CHD, which adds novel insight to the molecular mechanism of CHD, implying potential implications for genetic risk appraisal and individualized prophylaxis of the family members affected with CHD.

Mending a broken heart: In vitro, in vivo and in silico models of congenital heart disease

Birth defects contribute to ∼0.3% of global infant mortality in the first month of life, and congenital heart disease (CHD) is the most common birth defect among newborns worldwide. Despite the significant impact on human health, most treatments available for this heterogenous group of disorders are palliative at best. For this reason, the complex process of cardiogenesis, governed by multiple interlinked and dose-dependent pathways, is well investigated. Tissue, animal and, more recently, computerized models of the developing heart have facilitated important discoveries that are helping us to understand the genetic, epigenetic and mechanobiological contributors to CHD aetiology. In this Review, we discuss the strengths and limitations of different models of normal and abnormal cardiogenesis, ranging from single-cell systems and 3D cardiac organoids, to small and large animals and organ-level computational models. These investigative tools have revealed a diversity of pathogenic mechanisms that contribute to CHD, including genetic pathways, epigenetic regulators and shear wall stresses, paving the way for new strategies for screening and non-surgical treatment of CHD. As we discuss in this Review, one of the most-valuable advances in recent years has been the creation of highly personalized platforms with which to study individual diseases in clinically relevant settings.

Mechanosensitive Pathways in Heart Development: Findings from Chick Embryo Studies

The heart is the first organ that starts to function in a developing embryo. It continues to undergo dramatic morphological changes while pumping blood to the rest of the body. Genetic regulation of heart development is partly governed by hemodynamics. Chick embryo is a major animal model that has been used extensively in cardiogenesis research. To reveal mechanosensitive pathways, a variety of surgical interferences and chemical treatments can be applied to the chick embryo to manipulate the blood flow. Such manipulations alter expressions of mechanosensitive genes which may anticipate induction of morphological changes in the developing heart. This paper aims to present different approaches for generating clinically relevant disturbed hemodynamics conditions using this embryonic chick model and to summarize identified mechanosensitive genes using the model, providing insights into embryonic origins of congenital heart defects.

A Survey of Compound Heterozygous Variants in Pediatric Cancers and Structural Birth Defects

Compound heterozygous (CH) variants occur when two recessive alleles are inherited and the variants are located at different loci within the same gene in a given individual. CH variants are important contributors to many different types of recessively inherited diseases. However, many studies overlook CH variants because identification of this type of variant requires knowing the parent of origin for each nucleotide. Using computational methods, haplotypes can be inferred using a process called "phasing," which estimates the chromosomal origin of most nucleotides. In this paper, we used germline, phased, whole-genome sequencing (WGS) data to identify CH variants across seven pediatric diseases (adolescent idiopathic scoliosis: n = 16, congenital heart defects: n = 709, disorders of sex development: n = 79, ewing sarcoma: n = 287, neuroblastoma: n = 259, orofacial cleft: n = 107, and syndromic cranial dysinnervation: n = 172), available as parent-child trios in the Gabriella Miller Kids First Data Resource Center. Relatively little is understood about the genetic underpinnings of these diseases. We classified CH variants as "potentially damaging" based on minor allele frequencies (MAF), Combined Annotation Dependent Depletion scores, variant impact on transcription or translation, and gene-level frequencies in the disease group compared to a healthy population. For comparison, we also identified homozygous alternate (HA) variants, which affect both gene copies at a single locus; HA variants represent an alternative mechanism of recessive disease development and do not require phasing. Across all diseases, 2.6% of the samples had a potentially damaging CH variant and 16.2% had a potentially damaging HA variant. Of these samples with potentially damaging variants, the average number of genes per sample was 1 with a CH variant and 1.25 with a HA variant. Across all samples, 5.1 genes per disease had a CH variant, while 35.6 genes per disease had a HA variant; on average, only 4.3% of these variants affected common genes. Therefore, when seeking to identify potentially damaging variants of a putatively recessive disease, CH variants should be considered as potential contributors to disease development. If CH variants are excluded from analysis, important candidate genes may be overlooked.

Genetic and Cellular Interaction During Cardiovascular Development Implicated in Congenital Heart Diseases

Congenital heart disease (CHD) is the most common life-threatening congenital anomaly. CHD occurs due to defects in cardiovascular development, and the majority of CHDs are caused by a multifactorial inheritance mechanism, which refers to the interaction between genetic and environmental factors. During embryogenesis, the cardiovascular system is derived from at least four distinct cell lineages: the first heart field, second heart field, cardiac neural crest, and proepicardial organ. Understanding the genes involved in each lineage is essential to uncover the genomic architecture of CHD. Therefore, we provide an overview of recent research progress using animal models and mutation analyses to better understand the molecular mechanisms and pathways linking cardiovascular development and CHD. For example, we highlight our recent work on genes encoding three isoforms of inositol 1,4,5-trisphosphate receptors (IP₃R1, 2, and 3) that regulate various vital and developmental processes, which have genetic redundancy during cardiovascular development. Specifically, IP₃R1 and 2 have redundant roles in the atrioventricular cushion derived from the first heart field lineage, whereas IP₃R1 and 3 exhibit redundancy in the right ventricle and the outflow tract derived from the second heart field lineage, respectively. Moreover, 22q11.2 deletion syndrome (22q11DS) is highly associated with CHD involving the outflow tract, characterized by defects of the cardiac neural crest lineage. However, our studies have shown that TBX1, a major genetic determinant of 22q11DS, was not expressed in the cardiac neural crest but rather in the second heart field, suggesting the importance of the cellular interaction between the cardiac neural crest and the second heart field. Comprehensive genetic analysis using the Japanese genome bank of CHD and mouse models revealed that a molecular regulatory network involving GATA6, FOXC1/2, TBX1, SEMA3C, and FGF8 was essential for reciprocal signaling between the cardiac neural crest and the second heart field during cardiovascular development. Elucidation of the genomic architecture of CHD using induced pluripotent stem cells and next-generation sequencing technology, in addition to genetically modified animal models and human mutation analyses, would facilitate the development of regenerative medicine and/or preventive medicine for CHD in the near future.

Understanding Heart Field Progenitor Cells for Modeling Congenital Heart Diseases

PURPOSE OF REVIEW

Heart development is a meticulously coordinated process that involves the specification of two distinct populations of cardiac progenitor cells, namely the first and the second heart field. Disruption of heart field progenitors can result in congenital heart defects. In this review, we aim to describe the signaling pathways and transcription factors that link heart field development and congenital heart disease.

RECENT FINDINGS

Single-cell transcriptomics, lineage-tracing mouse models, and stem cell-based in vitro modeling of cardiogenesis have significantly improved the spatiotemporal characterization of cardiac progenitors. Additionally, novel functional genomic studies have now linked more genetic variants with congenital heart disease. Dysregulation of cardiac progenitor cells causes malformations that can be lethal. Ongoing research will continue to shed light on cardiac morphogenesis and help us better understand and treat patients with congenital heart disease.

The Role of Epigenetics in Congenital Heart Disease

Congenital heart disease (CHD) is the most common birth defect among newborns worldwide and contributes to significant infant morbidity and mortality. Owing to major advances in medical and surgical management, as well as improved prenatal diagnosis, the outcomes for these children with CHD have improved tremendously so much so that there are now more adults living with CHD than children. Advances in genomic technologies have discovered the genetic causes of a significant fraction of CHD, while at the same time pointing to remarkable complexity in CHD genetics. For this reason, the complex process of cardiogenesis, which is governed by multiple interlinked and dose-dependent pathways, is a well investigated process. In addition to the sequence of the genome, the contribution of epigenetics to cardiogenesis is increasingly recognized. Significant progress has been made dissecting the epigenome of the heart and identified associations with cardiovascular diseases. The role of epigenetic regulation in cardiac development/cardiogenesis, using tissue and animal models, has been well reviewed. Here, we curate the current literature based on studies in humans, which have revealed associated and/or causative epigenetic factors implicated in CHD. We sought to summarize the current knowledge on the functional role of epigenetics in cardiogenesis as well as in distinct CHDs, with an aim to provide scientists and clinicians an overview of the abnormal cardiogenic pathways affected by epigenetic mechanisms, for a better understanding of their impact on the developing fetal heart, particularly for readers interested in CHD research.

Trends in the prenatal diagnosis of trisomy 21 show younger maternal age and shift in the distribution of congenital heart disease over a 20-year period

Prenatal testing has changed greatly over the past two decades, which may affect the diagnosis of congenital heart disease (CHD) in Down syndrome. The present study aimed to analyze changes in the prevalence and distribution of CHD diagnosed via ultrasonography and fetopathology in 462 fetuses with trisomy 21 between two consecutive 10-year periods (1999-2018), as well as the associations between CHDs, ultrasound markers, and extracardiac malformations. Overall, the frequency of cardiovascular malformations in trisomy 21 was 27.7 and 26.5%, and ultrasound identified 70 and 62% of CHDs during these periods. A profound increase in first-trimester ultrasound findings and associated anomalies with CHDs (ventricular septal defect, Tetralogy of Fallot) since 2009 were observed. Second-trimester nonstructural heart abnormalities were associated with ultrasound anomalies (74%) and major extracardiac malformations (42.9%). During both study periods, mothers carrying fetuses with CHD were significantly younger than those without CHD (p = 0.038, p = 0.009, respectively). Comparing the two 10-year periods, there were no changes in the prevalence and detection of CHDs. Trend analysis revealed that, although the frequency of CHD remained stable, the diagnostic spectrum had shifted between the study periods. Detection of nonstructural heart abnormalities necessitates detailed follow-up for cardiac/extracardiac malformations and chromosomal disorders.

Analysis of Copy Number Variations by Low-Depth Whole-Genome Sequencing in Fetuses with Congenital Cardiovascular Malformations

Congenital cardiovascular malformations (CVMs) due to genomic mutations bring a greater risk of morbidity and comorbidity and increase the risks related to heart surgery. However, reports on CVMs induced by genomic mutations based on actual clinical data are still limited. In this study, 181 fetuses were screened by fetal echocardiography for prenatal diagnosis of congenital heart disease, including 146 cases without ultrasound extracardiac findings (Group A) and 35 cases with ultrasound extracardiac findings (Group B). All cases were analyzed by clinical data, karyotyping, and low-depth whole-genome sequencing. The rates of chromosomal abnormalities in Groups A and B were 4.8% (7/146) and 37.1% (13/35), respectively. There was a significant difference in the incidence of chromosomal abnormalities between Groups A and B (p < 0.001). In Group A, CNV-seq identified copy number variations (CNVs) in an additional 9.6% (14/146) of cases with normal karyotypes, including 7 pathogenic CNVs and 7 variations of uncertain clinical significance. In Group B, one pathogenic CNV was identified in a case with normal karyotype. Chromosomal abnormality is one of the most common causes of CVM with extracardiac defects. Low-depth whole-genome sequencing could effectively become a first approach for CNV diagnosis in fetuses with CVMs.

Heart Disease and Stroke Statistics-2021 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update. The 2021 Statistical Update is the product of a full year's worth of effort by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. This year's edition includes data on the monitoring and benefits of cardiovascular health in the population, an enhanced focus on social determinants of health, adverse pregnancy outcomes, vascular contributions to brain health, the global burden of cardiovascular disease, and further evidence-based approaches to changing behaviors related to cardiovascular disease.

RESULTS

Each of the 27 chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policy makers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Race and Genetics in Congenital Heart Disease: Application of iPSCs, Omics, and Machine Learning Technologies

Congenital heart disease (CHD) is a multifaceted cardiovascular anomaly that occurs when there are structural abnormalities in the heart before birth. Although various risk factors are known to influence the development of this disease, a full comprehension of the etiology and treatment for different patient populations remains elusive. For instance, racial minorities are disproportionally affected by this disease and typically have worse prognosis, possibly due to environmental and genetic disparities. Although research into CHD has highlighted a wide range of causal factors, the reasons for these differences seen in different patient populations are not fully known. Cardiovascular disease modeling using induced pluripotent stem cells (iPSCs) is a novel approach for investigating possible genetic variants in CHD that may be race specific, making it a valuable tool to help solve the mystery of higher incidence and mortality rates among minorities. Herein, we first review the prevalence, risk factors, and genetics of CHD and then discuss the use of iPSCs, omics, and machine learning technologies to investigate the etiology of CHD and its connection to racial disparities. We also explore the translational potential of iPSC-based disease modeling combined with genome editing and high throughput drug screening platforms.

Pathways Regulating Establishment and Maintenance of Cardiac Chamber Identity in Zebrafish

The vertebrate heart is comprised of two types of chambers-ventricles and atria-that have unique morphological and physiological properties. Effective cardiac function depends upon the distinct characteristics of ventricular and atrial cardiomyocytes, raising interest in the genetic pathways that regulate chamber-specific traits. Chamber identity seems to be specified in the early embryo by signals that establish ventricular and atrial progenitor populations and trigger distinct differentiation pathways. Intriguingly, chamber-specific features appear to require active reinforcement, even after myocardial differentiation is underway, suggesting plasticity of chamber identity within the developing heart. Here, we review the utility of the zebrafish as a model organism for studying the mechanisms that establish and maintain cardiac chamber identity. By combining genetic and embryological approaches, work in zebrafish has revealed multiple players with potent influences on chamber fate specification and commitment. Going forward, analysis of cardiomyocyte identity at the single-cell level is likely to yield a high-resolution understanding of the pathways that link the relevant players together, and these insights will have the potential to inform future strategies in cardiac tissue engineering.

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.

Genetic Etiology of Left-Sided Obstructive Heart Lesions: A Story in Development

Congenital heart disease is the most common congenital defect observed in newborns. Within the spectrum of congenital heart disease are left‐sided obstructive lesions (LSOLs), which include hypoplastic left heart syndrome, aortic stenosis, bicuspid aortic valve, coarctation of the aorta, and interrupted aortic arch. These defects can arise in isolation or as a component of a defined syndrome; however, nonsyndromic defects are often observed in multiple family members and associated with high sibling recurrence risk. This clear evidence for a heritable basis has driven a lengthy search for disease‐causing variants that has uncovered both rare and common variants in genes that, when perturbed in cardiac development, can result in LSOLs. Despite advancements in genetic sequencing platforms and broadening use of exome sequencing, the currently accepted LSOL‐associated genes explain only 10% to 20% of patients. Further, the combinatorial effects of common and rare variants as a cause of LSOLs are emerging. In this review, we highlight the genes and variants associated with the different LSOLs and discuss the strengths and weaknesses of the present genetic associations. Furthermore, we discuss the research avenues needed to bridge the gaps in our current understanding of the genetic basis of nonsyndromic congenital heart disease.

Recent and Upcoming Drug Therapies for Pediatric Heart Failure

Pediatric heart failure (HF) is an important clinical condition with high morbidity, mortality, and costs. Due to the heterogeneity in clinical presentation and etiologies, the development of therapeutic strategies is more challenging in children than adults. Most guidelines recommending drug therapy for pediatric HF are extrapolated from studies in adults. Unfortunately, even using all available treatment, progression to cardiac transplantation is common. The development of prospective clinical trials in the pediatric population has significant obstacles, including small sample sizes, slow recruitment rates, challenging endpoints, and high costs. However, progress is being made as evidenced by the recent introduction of ivabradine and of sacubitril/valsartan. In the last 5 years, new drugs have also been developed for HF with reduced ejection fraction (HFrEF) in adults. The use of well-designed prospective clinical trials will be fundamental in the evaluation of safety and efficacy of these new drugs on the pediatric population. The aim of this article is to review the clinical presentation and management of acute and chronic pediatric heart failure, focusing on systolic dysfunction in patients with biventricular circulation and a systemic left ventricle. We discuss the drugs recently approved for children and those emerging, or in use for adults with HFrEF.

A Comprehensive Clinical Genetics Approach to Critical Congenital Heart Disease in Infancy

OBJECTIVE

To investigate the frequency of genetic diagnoses among infants with critical congenital heart disease (CHD) using a comprehensive cardiovascular genetics approach and to identify genotype-phenotype correlations.

STUDY DESIGN

A retrospective chart review of patients evaluated by cardiovascular genetics in a pediatric cardiac intensive care unit from 2010 to 2015 was performed. Infants with CHD who were <1 month of age were included. CHD was classified using structured phenotype definitions. Cardiac and noncardiac phenotypes were tested for associations with abnormal genetic testing using χ¹ and Fisher exact tests.

RESULTS

Genetic evaluation was completed in 293 infants with CHD, of whom 213 had isolated congenital heart disease (iCHD) and 80 had multiple congenital anomalies. Overall, the yield of abnormal genetic testing was 26%. The multiple congenital anomalies cohort had a greater yield of genetic testing (39%) than the iCHD cohort (20%) (OR 2.7). Using a non-hierarchical CHD classification and excluding 22q11.2 deletion and common aneuploidies, right ventricular obstructive defects were associated with abnormal genetic testing (P = .0005). Extracardiac features associated with abnormal genetic testing included ear, nose, and throat (P = .003) and brain (P = .0001) abnormalities. A diagnosis of small for gestational age or intrauterine growth retardation also was associated with abnormal genetic testing (P = .0061), as was presence of dysmorphic features (P = .0033, OR 3.5). Infants without dysmorphia with iCHD or multiple congenital anomalies had similar frequencies of abnormal genetic testing.

CONCLUSIONS

The present study provides evidence to support a comprehensive cardiovascular genetics approach in evaluating infants with critical CHD while also identifying important genotype-phenotype considerations.

Variants of significance: medical genetics and surgical outcomes in congenital heart disease

PURPOSE OF REVIEW

This article reviews the current understanding and limitations in knowledge of the effect genetics and genetic diagnoses have on perioperative and postoperative surgical outcomes in patients with congenital heart disease (CHD).

RECENT FINDINGS

Presence of a known genetic diagnosis seems to effect multiple significant outcome metrics in CHD surgery including length of stay, need for extracorporeal membrane oxygenation, mortality, bleeding, and heart failure. Data regarding the effects of genetics in CHD is complicated by lack of standard genetic assessment resulting in inaccurate risk stratification of patients when analyzing data. Only 30% of variation in CHD surgical outcomes are explained by currently measured variables, with 2.5% being attributed to diagnosed genetic disorders, it is thought a significant amount of the remaining outcome variation is because of unmeasured genetic factors.

SUMMARY

Genetic diagnoses clearly have a significant effect on surgical outcomes in patients with CHD. Our current understanding is limited by lack of consistent genetic evaluation and assessment as well as evolving knowledge and discovery regarding the genetics of CHD. Standardizing genetic assessment of patients with CHD will allow for the best risk stratification and ultimate understanding of these effects.

Susceptibility to Heart Defects in Down Syndrome Is Associated with Single Nucleotide Polymorphisms in HAS 21 Interferon Receptor Cluster and VEGFA Genes

BACKGROUND

Congenital heart defects (CHDs) are present in about 40-60% of newborns with Down syndrome (DS). Patients with DS can also develop acquired cardiac disorders. Mouse models suggest that a critical 3.7 Mb region located on human chromosome 21 (HSA21) could explain the association with CHDs. This region includes a cluster of genes (IFNAR1, IFNAR2, IFNGR2, IL10RB) encoding for interferon receptors (IFN-Rs). Other genes located on different chromosomes, such as the vascular endothelial growth factor A (VEGFA), have been shown to be involved in cardiac defects. So, we investigated the association between single nucleotide polymorphisms (SNPs) in IFNAR2, IFNGR2, IL10RB and VEGFA genes, and the presence of CHDs or acquired cardiac defects in patients with DS.

METHODS

Individuals (n = 102) with DS, and age- and gender-matched controls (n = 96), were genotyped for four SNPs (rs2229207, rs2834213, rs2834167 and rs3025039) using KASPar assays.

RESULTS

We found that the IFNGR2 rs2834213 G homozygous genotype and IL10RB rs2834167G-positive genotypes were more common in patients with DSand significantly associated with heart disorders, while VEGFA rs3025039T-positive genotypes (T/*) were less prevalent in patients with CHDs.

CONCLUSIONS

We identified some candidate risk SNPs for CHDs and acquired heart defects in DS. Our data suggest that a complex architecture of risk alleles with interplay effects may contribute to the high variability of DS phenotypes.

A novel TBX5 mutation predisposes to familial cardiac septal defects and atrial fibrillation as well as bicuspid aortic valve

TBX5 has been linked to Holt-Oram syndrome, with congenital heart defect (CHD) and atrial fibrillation (AF) being two major cardiac phenotypes. However, the prevalence of a TBX5 variation in patients with CHD and AF remains obscure. In this research, by sequencing analysis of TBX5 in 178 index patients with both CHD and AF, a novel heterozygous variation, NM_000192.3: c.577G>T; p.(Gly193*), was identified in one index patient with CHD and AF as well as bicuspid aortic valve (BAV), with an allele frequency of approximately 0.28%. Genetic analysis of the proband's pedigree showed that the variation co-segregated with the diseases. The pathogenic variation was not detected in 292 unrelated healthy subjects. Functional analysis by using a dual-luciferase reporter assay system showed that the Gly193*-mutant TBX5 protein failed to transcriptionally activate its target genes MYH6 and NPPA. Moreover, the mutation nullified the synergistic transactivation between TBX5 and GATA4 as well as NKX2-5. Additionally, whole-exome sequencing analysis showed no other genes contributing to the diseases. This investigation firstly links a pathogenic variant in the TBX5 gene to familial CHD and AF as well as BAV, suggesting that CHD and AF as well as BAV share a common developmental basis in a subset of patients.

Sudden cardiac death in children with congenital heart disease: a critical review of the literature

Sudden cardiac death is an uncommon but yet catastrophic event, which can occur in neonates and young children. Although extensive research has been carried out assessing the underlying causes, there still remains a degree of uncertainty around this area. Congenital heart disease (CHD) is one known cause of sudden cardiac death in children, the aetiology of which embraces virally induced mechanisms, genetic susceptibility, drug-induced, and maternal factors. Screening tools and investigations including electrocardiograms and echocardiograms alongside a concise history taking and physical examination can be used to identify the potential cardiovascular risk factors of sudden death. This review has comprehensively studied the causes and risk factors for sudden cardiac death in children with CHD and provides a collation and summary of the evidence available so far underpinning the complex link between the two. Moreover, current screening and prevention methods are discussed in detail in order to increase awareness and understanding of how we can improve patient outcomes.

Pregnancy outcomes in women with aortic coarctation

OBJECTIVE

Pregnancy in women with aortic coarctation (CoA) has an estimated moderately increased risk (mWHO II-III) of adverse cardiovascular, obstetric or fetal events, but prospective data to validate this risk classification are scarce. We examined pregnancy outcomes and identified associations with adverse outcomes.

METHODS

Pregnancies in women with CoA were selected from the worldwide prospective Registry of Pregnancy and Cardiac Disease (ROPAC, n=303 out of 5739), part of the European Society of Cardiology EURObservational Research Programme. The frequency of and associations with major adverse cardiac events (MACE) and hypertensive disorders (pregnancy-induced hypertension, (pre-)eclampsia or haemolysis, elevated liver enzymes and low platelets syndrome) were analysed.

RESULTS

Of 303 pregnancies (mean age 30 years, pregnancy duration 39 weeks), 9.6% involved unrepaired CoA and 27.1% were in women with pre-existing hypertension. No maternal deaths or aortic dissections occurred. MACE occurred in 13 pregnancies (4.3%), of which 10 cases were of heart failure (3.3%). Univariable associations with MACE included prepregnancy clinical signs of heart failure (OR 31.8, 95% CI 6.8 to 147.7), left ventricular ejection fraction <40% (OR 10.4, 95% CI 1.8 to 59.5), New York Heart Association class >1 (OR 11.4, 95% CI 3.6 to 36.3) and cardiac medication use (OR 4.9, 95% CI 1.3 to 18.3). Hypertensive disorders of pregnancy occurred in 16 (5.3%), cardiac medication use being their only predictor (OR 3.2, 95% CI 1.1 to 9.6). Premature births were 9.1%, caesarean section was performed in 49.7% of pregnancies. Of 4 neonatal deaths, 3 were after spontaneous extreme preterm birth.

CONCLUSIONS

The ROPAC data show low MACE and hypertensive disorder rates during pregnancy in women with CoA, suggesting pregnancy to be more safe and better tolerated than previously appreciated.

Recommendations for genetic testing in cardiology: Review of major international guidelines

In recent years, the importance of genetic causes of cardiovascular diseases has been increasingly recognized, as the result of significant advances in molecular diagnosis techniques. This growing knowledge has enabled the identification of new phenotypes and the subclassification of clinical syndromes, impacting the therapeutic approach and genetic counseling offered to affected families. This paper describes the state of the art of genetic testing in the main cardiovascular diseases, aiming to provide a useful tool to help cardiologists and other health professionals involved in the care of individuals with hereditary heart diseases and their families.

Patient-specific genomics and cross-species functional analysis implicate LRP2 in hypoplastic left heart syndrome

Congenital heart diseases (CHDs), including hypoplastic left heart syndrome (HLHS), are genetically complex and poorly understood. Here, a multidisciplinary platform was established to functionally evaluate novel CHD gene candidates, based on whole-genome and iPSC RNA sequencing of a HLHS family-trio. Filtering for rare variants and altered expression in proband iPSCs prioritized 10 candidates. siRNA/RNAi-mediated knockdown in healthy human iPSC-derived cardiomyocytes (hiPSC-CM) and in developing Drosophila and zebrafish hearts revealed that LDL receptor-related protein LRP2 is required for cardiomyocyte proliferation and differentiation. Consistent with hypoplastic heart defects, compared to patents the proband's iPSC-CMs exhibited reduced proliferation. Interestingly, rare, predicted-damaging LRP2 variants were enriched in a HLHS cohort; however, understanding their contribution to HLHS requires further investigation. Collectively, we have established a multi-species high-throughput platform to rapidly evaluate candidate genes and their interactions during heart development, which are crucial first steps toward deciphering oligogenic underpinnings of CHDs, including hypoplastic left hearts.

Genetic Basis of Human Congenital Heart Disease

Congenital heart disease (CHD) is the most common major congenital anomaly with an incidence of ∼1% of live births and is a significant cause of birth defect-related mortality. The genetic mechanisms underlying the development of CHD are complex and remain incompletely understood. Known genetic causes include all classes of genetic variation including chromosomal aneuploidies, copy number variants, and rare and common single-nucleotide variants, which can be either de novo or inherited. Among patients with CHD, ∼8%-12% have a chromosomal abnormality or aneuploidy, between 3% and 25% have a copy number variation, and 3%-5% have a single-gene defect in an established CHD gene with higher likelihood of identifying a genetic cause in patients with nonisolated CHD. These genetic variants disrupt or alter genes that play an important role in normal cardiac development and in some cases have pleiotropic effects on other organs. This work reviews some of the most common genetic causes of CHD as well as what is currently known about the underlying mechanisms.

Systems genetics analysis identifies calcium-signaling defects as novel cause of congenital heart disease

BACKGROUND

Congenital heart disease (CHD) occurs in almost 1% of newborn children and is considered a multifactorial disorder. CHD may segregate in families due to significant contribution of genetic factors in the disease etiology. The aim of the study was to identify pathophysiological mechanisms in families segregating CHD.

METHODS

We used whole exome sequencing to identify rare genetic variants in ninety consenting participants from 32 Danish families with recurrent CHD. We applied a systems biology approach to identify developmental mechanisms influenced by accumulation of rare variants. We used an independent cohort of 714 CHD cases and 4922 controls for replication and performed functional investigations using zebrafish as in vivo model.

RESULTS

We identified 1785 genes, in which rare alleles were shared between affected individuals within a family. These genes were enriched for known cardiac developmental genes, and 218 of these genes were mutated in more than one family. Our analysis revealed a functional cluster, enriched for proteins with a known participation in calcium signaling. Replication in an independent cohort confirmed increased mutation burden of calcium-signaling genes in CHD patients. Functional investigation of zebrafish orthologues of ITPR1, PLCB2, and ADCY2 verified a role in cardiac development and suggests a combinatorial effect of inactivation of these genes.

CONCLUSIONS

The study identifies abnormal calcium signaling as a novel pathophysiological mechanism in human CHD and confirms the complex genetic architecture underlying CHD.

DNA methylation at CpG island shore and RXRα regulate NR2F2 in heart tissues of tetralogy of Fallot patients

The nuclear receptor subfamily 2 group F member 2 (NR2F2) gene encodes a ligand-inducible transcription factor involved in angiogenesis and heart development. This study aimed to elucidate the molecular mechanism of epigenetic regulation of NR2F2 in tetralogy of Fallot (TOF) development. In the present study, immunohistochemical staining showed that NR2F2 protein expression was significantly higher in the right ventricular outflow tract (RVOT) tissues of TOF cases compared with controls. The methylation status of the CpG island shore (CGIS) of the NR2F2 gene was decreased in TOF cases, and the CpG site 3 in the CGIS region of NR2F2 promoter was a differential methylation site. Furthermore, the methylation level of the CpG site 3 and the NR2F2 protein expression were significantly negatively correlated in TOF patients. In vitro functional analysis revealed that RXRα could upregulate the NR2F2 gene by directly binding to the CGIS in the NR2F2 promoter, while hypomethylation of the NR2F2 promoter via treatment with 5-azacytidine influenced the affinity of RXRα to its binding sites, as shown by ChIP-qPCR. These findings suggest that promoter hypomethylation activates NR2F2 by enhancing RXRα binding to NR2F2 CGIS in the development of TOF.

Contribution of single-gene defects to congenital cardiac left-sided lesions in the prenatal setting

OBJECTIVES

To explore the contribution of single-gene defects to the genetic cause of cardiac left-sided lesions (LSLs), and to evaluate the incremental diagnostic yield of whole-exome sequencing (WES) for single-gene defects in fetuses with LSLs without aneuploidy or a pathogenic copy-number variant (pCNV).

METHODS

Between 10 April 2015 and 30 October 2018, we recruited 80 pregnant women diagnosed with a LSL who had termination of pregnancy and genetic testing. Eligible LSLs were aortic valve atresia or stenosis, coarctation of the aorta, mitral atresia or stenosis and hypoplastic left heart syndrome (HLHS). CNV sequencing (CNV-seq) and WES were performed sequentially on specimens from these fetuses and their parents. CNV-seq was used to identify aneuploidies and pCNVs, while WES was used to identify diagnostic genetic variants in cases without aneuploidy or pCNV.

RESULTS

Of 80 pregnancies included in the study, 27 (33.8%) had a genetic diagnosis. CNV-seq analysis identified six (7.5%) fetuses with aneuploidy and eight (10.0%) with pCNVs. WES analysis of the remaining 66 cases revealed diagnostic genetic variants in 13 (19.7%) cases, indicating that the diagnostic yield of WES for the entire cohort was 16.3% (13/80). KMT2D was the most frequently mutated gene (7/66 (10.6%)) in fetuses with LSL without aneuploidy or pCNVs, followed by NOTCH1 (4/66 (6.1%)). HLHS was the most prevalent cardiac phenotype (4/7) in cases with a KMT2D mutation in this cohort. An additional six (9.1%) cases were found to have potentially deleterious variants in candidate genes.

CONCLUSIONS

Single-gene defects contribute substantially to the genetic etiology of fetal LSLs. KMT2D mutations accounted for approximately 10% of LSLs in our fetal cohort. WES has the potential to provide genetic diagnoses in fetuses with LSLs without aneuploidy or pCNVs. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Genomic analyses implicate noncoding de novo variants in congenital heart disease

A genetic etiology is identified for one-third of patients with congenital heart disease (CHD), with 8% of cases attributable to coding de novo variants (DNVs). To assess the contribution of noncoding DNVs to CHD, we compared genome sequences from 749 CHD probands and their parents with those from 1,611 unaffected trios. Neural network prediction of noncoding DNV transcriptional impact identified a burden of DNVs in individuals with CHD (n = 2,238 DNVs) compared to controls (n = 4,177; P = 8.7 × 10-4). Independent analyses of enhancers showed an excess of DNVs in associated genes (27 genes versus 3.7 expected, P = 1 × 10-5). We observed significant overlap between these transcription-based approaches (odds ratio (OR) = 2.5, 95% confidence interval (CI) 1.1-5.0, P = 5.4 × 10-3). CHD DNVs altered transcription levels in 5 of 31 enhancers assayed. Finally, we observed a DNV burden in RNA-binding-protein regulatory sites (OR = 1.13, 95% CI 1.1-1.2, P = 8.8 × 10-5). Our findings demonstrate an enrichment of potentially disruptive regulatory noncoding DNVs in a fraction of CHD at least as high as that observed for damaging coding DNVs.

RYBP is important for cardiac progenitor cell development and sarcomere formation

We have previously established that epigenetic regulator RING1 and YY1 binding protein (RYBP) is required for the contractility of embryonic stem (ES) cell derived cardiomyocytes (CMCs), suggesting its essential role in contractility. In order to investigate the underlying molecular events of this phenotype, we compared the transcriptomic profile of the wild type and Rybp null mutant ES cells and CMCs differentiated from these cell lines. We identified genes related to ion homeostasis, cell adhesion and sarcomeric organization affected in the Rybp null mutant CMCs, by using hierarchical gene clustering and Gene Ontology analysis. We have also demonstrated that the amount of RYBP is drastically reduced in the terminally differentiated wild type CMCs whilst it is broadly expressed in the early phase of differentiation when progenitors form. We also describe that RYBP is important for the proper expression of key cardiac transcription factors including Mesp1, Shh and Mef2c. These findings identify Rybp as a gene important for both early cardiac gene transcription and consequent sarcomere formation necessary for contractility. Since impairment of sarcomeric function and contractility plays a central role in reduced cardiac pump function leading to heart failures in human, current results might be relevant to the pathophysiology of cardiomyopathies.

Genetic and Epigenetic Control of Heart Development

A transcriptional program implemented by transcription factors and epigenetic regulators governs cardiac development and disease. Mutations in these factors are important causes of congenital heart disease. Here, we review selected recent advances in our understanding of the transcriptional and epigenetic control of heart development, including determinants of cardiac transcription factor chromatin occupancy, the gene regulatory network that regulates atrial septation, the chromatin landscape and cardiac gene regulation, and the role of Brg/Brahma-associated factor (BAF), nucleosome remodeling and histone deacetylation (NuRD), and Polycomb epigenetic regulatory complexes in heart development.