Identification of Gender-Specific Genetic Variants in Patients With Bicuspid Aortic Valve

Risk and Resilience Variants in the Retinoic Acid Metabolic and Developmental Pathways Associated with Risk of FASD Outcomes

Fetal Alcohol Spectrum Disorder (FASD) is a common neurodevelopmental disorder that affects an estimated 2-5% of North Americans. FASD is induced by prenatal alcohol exposure (PAE) during pregnancy and while there is a clear genetic contribution, few genetic factors are currently identified or understood. In this study, using a candidate gene approach, we performed a genetic variant analysis of retinoic acid (RA) metabolic and developmental signaling pathway genes on whole exome sequencing data of 23 FASD-diagnosed individuals. We found risk and resilience alleles in ADH and ALDH genes known to normally be involved in alcohol detoxification at the expense of RA production, causing RA deficiency, following PAE. Risk and resilience variants were also identified in RA-regulated developmental pathway genes, especially in SHH and WNT pathways. Notably, we also identified significant variants in the causative genes of rare neurodevelopmental disorders sharing comorbidities with FASD, including STRA6 (Matthew-Wood), SOX9 (Campomelic Dysplasia), FDG1 (Aarskog), and 22q11.2 deletion syndrome (TBX1). Although this is a small exploratory study, the findings support PAE-induced RA deficiency as a major etiology underlying FASD and suggest risk and resilience variants may be suitable biomarkers to determine the risk of FASD outcomes following PAE.

Spatial transcriptomics reveals novel genes during the remodelling of the embryonic human arterial valves

Abnormalities of the arterial valves, including bicuspid aortic valve (BAV) are amongst the most common congenital defects and are a significant cause of morbidity as well as predisposition to disease in later life. Despite this, and compounded by their small size and relative inaccessibility, there is still much to understand about how the arterial valves form and remodel during embryogenesis, both at the morphological and genetic level. Here we set out to address this in human embryos, using Spatial Transcriptomics (ST). We show that ST can be used to investigate the transcriptome of the developing arterial valves, circumventing the problems of accurately dissecting out these tiny structures from the developing embryo. We show that the transcriptome of CS16 and CS19 arterial valves overlap considerably, despite being several days apart in terms of human gestation, and that expression data confirm that the great majority of the most differentially expressed genes are valve-specific. Moreover, we show that the transcriptome of the human arterial valves overlaps with that of mouse atrioventricular valves from a range of gestations, validating our dataset but also highlighting novel genes, including four that are not found in the mouse genome and have not previously been linked to valve development. Importantly, our data suggests that valve transcriptomes are under-represented when using commonly used databases to filter for genes important in cardiac development; this means that causative variants in valve-related genes may be excluded during filtering for genomic data analyses for, for example, BAV. Finally, we highlight "novel" pathways that likely play important roles in arterial valve development, showing that mouse knockouts of RBP1 have arterial valve defects. Thus, this study has confirmed the utility of ST for studies of the developing heart valves and broadens our knowledge of the genes and signalling pathways important in human valve development.

Mechanisms of Aortic Dilation in Patients With Bicuspid Aortic Valve: JACC State-of-the-Art Review

Bicuspid aortic valve is the most common congenital heart disease and exposes patients to an increased risk of aortic dilation and dissection. Aortic dilation is a slow, silent process, leading to a greater risk of aortic dissection. The prevention of adverse events together with optimization of the frequency of the required lifelong imaging surveillance are important for both clinicians and patients and motivated extensive research to shed light on the physiopathologic processes involved in bicuspid aortic valve aortopathy. Two main research hypotheses have been consolidated in the last decade: one supports a genetic basis for the increased prevalence of dilation, in particular for the aortic root, and the second supports the damaging impact on the aortic wall of altered flow dynamics associated with these structurally abnormal valves, particularly significant in the ascending aorta. Current opinion tends to rule out mutually excluding causative mechanisms, recognizing both as important and potentially clinically relevant.

Novel Association of the NOTCH Pathway Regulator MIB1 Gene With the Development of Bicuspid Aortic Valve

Importance

Nonsyndromic bicuspid aortic valve (nsBAV) is the most common congenital heart valve malformation. BAV has a heritable component, yet only a few causative genes have been identified; understanding BAV genetics is a key point in developing personalized medicine.

Objective

To identify a new gene for nsBAV.

Design, Setting, and Participants

This was a comprehensive, multicenter, genetic association study based on candidate gene prioritization in a familial cohort followed by rare and common association studies in replication cohorts. Further validation was done using in vivo mice models. Study data were analyzed from October 2019 to October 2022. Three cohorts of patients with BAV were included in the study: (1) the discovery cohort was a large cohort of inherited cases from 29 pedigrees of French and Israeli origin; (2) the replication cohort 1 for rare variants included unrelated sporadic cases from various European ancestries; and (3) replication cohort 2 was a second validation cohort for common variants in unrelated sporadic cases from Europe and the US.

Main Outcomes and Measures

To identify a candidate gene for nsBAV through analysis of familial cases exome sequencing and gene prioritization tools. Replication cohort 1 was searched for rare and predicted deleterious variants and genetic association. Replication cohort 2 was used to investigate the association of common variants with BAV.

Results

A total of 938 patients with BAV were included in this study: 69 (7.4%) in the discovery cohort, 417 (44.5%) in replication cohort 1, and 452 (48.2%) in replication cohort 2. A novel human nsBAV gene, MINDBOMB1 homologue MIB1, was identified. MINDBOMB1 homologue (MIB1) is an E3-ubiquitin ligase essential for NOTCH-signal activation during heart development. In approximately 2% of nsBAV index cases from the discovery and replication 1 cohorts, rare MIB1 variants were detected, predicted to be damaging, and were significantly enriched compared with population-based controls (2% cases vs 0.9% controls; P = .03). In replication cohort 2, MIB1 risk haplotypes significantly associated with nsBAV were identified (permutation test, 1000 repeats; P = .02). Two genetically modified mice models carrying Mib1 variants identified in our cohort showed BAV on a NOTCH1-sensitized genetic background.

Conclusions and Relevance

This genetic association study identified the MIB1 gene as associated with nsBAV. This underscores the crucial role of the NOTCH pathway in the pathophysiology of BAV and its potential as a target for future diagnostic and therapeutic intervention.

Diagnostic role of aortic valve calcium scoring in various etiologies of aortic stenosis

Most of the studies about aortic valve calcium (AVC) score in aortic stenosis (AS) were based on degenerative or bicuspid AS but not rheumatic AS. We aimed to study the diagnostic accuracy of AVC score to determine severe AS in various etiologies. Adult patients diagnosed with mild to severe AS were enrolled. AVC score were identified from multi-detector computed tomography (MDCT) scan. The AVC score was highest in bicuspid AS (3211.9 (IQR (1100.0-4562.4) AU) compared to degenerative AS (1803.7 (IQR (1073.6-2550.6) AU)), and rheumatic AS (875.6 (IQR 453.3-1594.0) AU), p < 0.001. For the ROC curve to identify severe AS, the AVC score performed well in degenerative and bicuspid AS with the area under the ROC curve (AuROC) 0.834 (95% CI, 0.730, 0.938) in degenerative group; and 0.820 (95% CI, 0.687, 0.953) in bicuspid AS. Whereas AVC score had non-significant diagnostic accuracy with AuROC 0.667 (95% CI, 0.357, 0.976) for male and 0.60(95% CI, 0.243, 0.957) for female in rheumatic AS. The cut-off AVC score values to identify severe AS were AVCS > 2028.9AU (male) and > 1082.5AU (female) for degenerative AS, and > 2431.8AU (male) and > 1293.5AU (female) for bicuspid AS. In conclusions, AVC score is the accurate test for assessing severity in patients with degenerative and bicuspid AS but performs poorly in rheumatic AS group.

Genetics of aortic valve disease

PURPOSE OF REVIEW

Aortic valve disease is a leading global cause of morbidity and mortality, posing an increasing burden on society. Advances in next-generation technologies and disease models over the last decade have further delineated the genetic and molecular factors that might be exploited in development of therapeutics for affected patients. This review describes several advances in the molecular and genetic understanding of AVD, focusing on bicuspid aortic valve (BAV) and calcific aortic valve disease (CAVD).

RECENT FINDINGS

Genomic studies have identified a myriad of genes implicated in the development of BAV, including NOTCH1 , SMAD6 and ADAMTS19 , along with members of the GATA and ROBO gene families. Similarly, several genes associated with the initiation and progression of CAVD, including NOTCH1 , LPA , PALMD , IL6 and FADS1/2 , serve as the launching point for emerging clinical trials.

SUMMARY

These new insights into the genetic contributors of AVD have offered new avenues for translational disease investigation, bridging molecular discoveries to emergent pharmacotherapeutic options. Future studies aimed at uncovering new genetic associations and further defining implicated molecular pathways are fuelling the new wave of drug discovery.

Bacterial Culture-Negative Acute Infective Endocarditis With Vegetation in Native Bicuspid Aortic Valve

A 51-year-old male with a past medical history of bicuspid aortic valve, hypertension, and anterior cerebral artery stroke of unclear etiology three months earlier, presented to the Emergency Department with progressive shortness of breath, hemoptysis, and night sweats. The patient's echocardiogram revealed a mobile mass greater than 1.0 cm in diameter on the bicuspid aortic valve, which was not present on the echocardiogram three months prior, during his stroke workup. Per modified Duke's criteria, this patient was found to have 'definite' infective endocarditis despite persistently negative blood cultures. The patient underwent urgent surgical aortic valve replacement and a ventricular septal defect was noted that was not seen on prior imaging. The patient was discharged on intravenous antibiotics and warfarin. The patient was able to return to his normal functional status weeks after surgery, and is continuing to exercise without limitation. This case provides an example of patients with bicuspid aortic valves having an increased propensity for developing infective endocarditis. While also highlighting the interesting intra-operative images and presentation of acute culture-negative endocarditis with vegetation, and the subsequent repair, treatment, and recovery.

Congenital aortic valve stenosis: from pathophysiology to molecular genetics and the need for novel therapeutics

Congenital aortic valve stenosis (AVS) is one of the most common valve anomalies and accounts for 3%-6% of cardiac malformations. As congenital AVS is often progressive, many patients, both children and adults, require transcatheter or surgical intervention throughout their lives. While the mechanisms of degenerative aortic valve disease in the adult population are partially described, the pathophysiology of adult AVS is different from congenital AVS in children as epigenetic and environmental risk factors play a significant role in manifestations of aortic valve disease in adults. Despite increased understanding of genetic basis of congenital aortic valve disease such as bicuspid aortic valve, the etiology and underlying mechanisms of congenital AVS in infants and children remain unknown. Herein, we review the pathophysiology of congenitally stenotic aortic valves and their natural history and disease course along with current management strategies. With the rapid expansion of knowledge of genetic origins of congenital heart defects, we also summarize the literature on the genetic contributors to congenital AVS. Further, this increased molecular understanding has led to the expansion of animal models with congenital aortic valve anomalies. Finally, we discuss the potential to develop novel therapeutics for congenital AVS that expand on integration of these molecular and genetic advances.

Cellular Senescence, Aging and Non-Aging Processes in Calcified Aortic Valve Stenosis: From Bench-Side to Bedside

Aortic valve stenosis (AS) is the most common valvular heart disease. The incidence of AS increases with age, however, a significant proportion of elderly people have no significant AS, indicating that both aging and nonaging pathways are involved in the pathomechanism of AS. Age-related and stress-induced cellular senescence accompanied by further active processes represent the key elements of AS pathomechanism. The early stage of aortic valve degeneration involves dysfunction and disruption of the valvular endothelium due to cellular senescence and mechanical stress on blood flow. These cells are replaced by circulating progenitor cells, but in an age-dependent decelerating manner. When endothelial denudation is no longer replaced by progenitor cells, the path opens for focal lipid deposition, initiating subsequent oxidation, inflammation and micromineralisation. Later stages of AS feature a complex active process with extracellular matrix remodeling, fibrosis and calcification. Echocardiography is the gold standard method for diagnosing aortic valve disease, although computed tomography and cardiac magnetic resonance are useful additional imaging methods. To date, no medical treatment has been proven to halt the progression of AS. Elucidation of differences and similarities between vascular and valvular calcification pathomechanisms may help to find effective medical therapy and reduce the increasing health burden of the disease.

Contribution of NOTCH1 genetic variants to bicuspid aortic valve and other congenital lesions

INTRODUCTION

Bicuspid aortic valve (BAV) affects 1% of the general population. NOTCH1 was the first gene associated with BAV. The proportion of familial and sporadic BAV disease attributed to NOTCH1 mutations has not been estimated.

AIM

The aim of our study was to provide an estimate of familial and sporadic BAV disease attributable to NOTCH1 mutations.

METHODS

The population of our study consisted of participants of the University of Leicester Bicuspid aoRtic vAlVe gEnetic research-8 pedigrees with multiple affected family members and 381 sporadic patients. All subjects underwent NOTCH1 sequencing. A systematic literature search was performed in the NCBI PubMed database to identify publications reporting NOTCH1 sequencing in context of congenital heart disease.

RESULTS

NOTCH1 sequencing in 36 subjects from 8 pedigrees identified one variant c.873C>G/p.Tyr291* meeting the American College of Medical Genetics and Genomics criteria for pathogenicity. No pathogenic or likely pathogenic NOTCH1 variants were identified in 381 sporadic patients. Literature review identified 64 relevant publication reporting NOTCH1 sequencing in 528 pedigrees and 9449 sporadic subjects. After excluding families with syndromic disease pathogenic and likely pathogenic NOTCH1 variants were detected in 9/435 (2.1%; 95% CI: 0.7% to 3.4%) of pedigrees and between 0.05% (95% CI: 0.005% to 0.10%) and 0.08% (95% CI: 0.02% to 0.13%) of sporadic patients. Incomplete penetrance of definitely pathogenic NOTCH1 mutations was observed in almost half of reported pedigrees.

CONCLUSIONS

Pathogenic and likely pathogenic NOTCH1 genetic variants explain 2% of familial and <0.1% of sporadic BAV disease and are more likely to associate with tetralogy of Fallot and hypoplastic left heart.

Association between single-nucleotide polymorphisms of NKX2.5 and congenital heart disease in Chinese population: A meta-analysis

NKX2.5 is a transcription factor that plays a key role in cardiovascular growth and development. Several independent studies have been previously conducted to investigate the association between the single-nucleotide polymorphism (SNP) 606G >C (rs3729753) in the coding region of NKX2.5 and congenital heart disease (CHD). However, the results of these studies have been inconsistent. Therefore, the present study aimed to reveal the relationship between NKX2.5 SNP 606G >C and the risk of CHD as possible in the Chinese population through meta-analysis. After retrieving related articles in PubMed, MEDLINE, EMBASE, Web of science, Cochrane, China National Knowledge Infrastructure, Wanfang DATA, and VIP database until August 2021, a total of eight studies were included in the present meta-analysis. The qualified research data were then merged into allele, dominant, recessive, heterozygous, homozygous, and additive models. Overall results of the current meta-analysis showed that 606G >C was not associated with CHD of the Chinese population in any model. In addition, subgroup analysis based on CHD type gave the same negative result. Results of sensitivity analysis showed that there was no significant correlation after the deletion of each study. Furthermore, it was noted that the results were negative and the heterogeneity was not significant. In conclusion, it was evident that NKX2-5 SNP 606G >C may not lead to the risk of CHD in Chinese population.

Sex Differences and Similarities in Valvular Heart Disease

As populations age worldwide, the burden of valvular heart disease has grown exponentially, and so has the proportion of affected women. Although rheumatic valve disease is declining in high-income countries, degenerative age-related causes are rising. Calcific aortic stenosis and degenerative mitral regurgitation affect a significant proportion of elderly women, particularly those with comorbidities. Women with valvular heart disease have been underrepresented in many of the landmark studies which form the basis for guideline recommendations. As a consequence, surgical referrals in women have often been delayed, with worse postoperative outcomes compared with men. As described in this review, a more recent effort to include women in research studies and clinical trials has increased our knowledge about sex-based differences in epidemiology, pathophysiology, diagnostic criteria, treatment options, outcomes, and prognosis.

Development of the Human Arterial Valves: Understanding Bicuspid Aortic Valve

Abnormalities in the arterial valves are some of the commonest congenital malformations, with bicuspid aortic valve (BAV) occurring in as many as 2% of the population. Despite this, most of what we understand about the development of the arterial (semilunar; aortic and pulmonary) valves is extrapolated from investigations of the atrioventricular valves in animal models, with surprisingly little specifically known about how the arterial valves develop in mouse, and even less in human. In this review, we summarise what is known about the development of the human arterial valve leaflets, comparing this to the mouse where appropriate.

Aortic root aortopathy in bicuspid aortic valve associated with high genetic risk

Background

The bicuspid aortic valve (BAV) is prone to ascending aortic dilatation (AAD) involving both the tubular segment and the aortic root. The genetic factor was proposed as one of the most important mechanisms for AAD. We hypothesized that the rare genetic variants mainly contribute to the pathogenesis of aortic roots in affected individuals.

Methods

The diameter of aortic root or ascending aorta ≥ 40 mm was counted as AAD. The targeted next-generation sequencing of 13 BAV-associated genes were performed on a continuous cohort of 96 unrelated BAV patients. The rare variants with allele frequency < 0.05% were selected and analyzed. Variants frequency was compared against the Exome aggregation consortium database. The pathogenicity of the genetic variants was evaluated according to the American College of Medical Genetics and Genomics guidelines.

Results

A total of 27 rare nonsynonymous coding variants involving 9 genes were identified in 25 individuals. The burden analysis revealed that variants in GATA5, GATA6, and NOTCH1 were significantly associated with BAV. Eighty percent of the pathogenic variants were detected in root group. The detection rate of rare variants was higher in root dilatation group (71.4%) compared with normal aorta (29.0%) and tubular dilatation groups (29.6%) (P = 0.018). The rare variant was identified as the independent risk factor of root dilatation [P = 0.014, hazard ratio = 23.9, 95% confidence interval (1.9–302.9)].

Conclusions

Our results presented a broad genetic spectrum in BAV patients. The rare variants of BAV genes contribute the most to the root phenotype among BAV patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02215-y.

Sex and Race Differences in the Pathophysiology, Diagnosis, Treatment, and Outcomes of Valvular Heart Diseases

Valvular heart diseases have long been considered to be similar in men and women and across races/ethnicities. Recently, studies have demonstrated major differences between sexes. Unfortunately, studies on valvular heart diseases, as on other cardiovascular diseases, are mostly performed in Caucasian men or in cohorts with a vast majority of Caucasian men. Therefore, our knowledge on valvular diseases in women and non-Caucasians remains limited. Nevertheless, aortic stenosis has been shown to be almost as prevalent in women as in men, and less prevalent in African Americans. Men appear to have a more calcified aortic valve lesion, and women tend to have a more fibrosed one. Primary mitral regurgitation is more frequent in women who have more rheumatic and Barlow etiologies, whereas men have more fibroelastic deficiency and posterior leaflet prolapse/flail. Left ventricular remodelling due to valvular heart diseases is sex related in terms of geometry and probably also in composition of the tissue. Outcomes seem to be worse in women after surgical interventions and better than or equivalent to men after transcatheter ones. Regarding other valvular heart diseases, very few studies are available: Aortic regurgitation is more frequent in men, isolated tricuspid regurgitation more frequent in women. Rheumatic valve diseases are more frequent in women and are mostly represented by mitral and aortic stenoses. Many other sex/gender- and race/ethnic-specific studies are still needed in epidemiology, pathophysiology, presentation, management, and outcomes. This review aims to report the available data on sex differences and race specificities in valvular heart diseases, with a primary focus on aortic stenosis and mitral regurgitation.

An interesting Mybpc3 heterozygous mutation associated with bicuspid aortic valve

BACKGROUND

Bicuspid aortic valve (BAV) is a common congenital heart defect (0.5-2.0% in the adult), potentially an onset factor of aortic stenosis (AS). Increasing evidence demonstrates that genetic risk factors play a key role in the pathogenesis of BAV, but the genetic basis underlying this cardiac malformation remains poorly understood.

METHODS

Whole exome sequencing (WES) was utilized to uncover genetic variants associated with BAV. Pathogenicity score and mode of inheritance through bioinformatics tools were undertook to identify the possible disease-causing mutation.

RESULTS

A heterozygous Ala58Val mutation in Myosin binding protein C (Mybpc3) was identified out of 2,840 variants in an 11-year-old female patient. The proband and her father were confirmed to be heterozygous carriers of 173 C>T hybridization, and her mother was homozygous negative of the mutation as confirmed through Sanger sequencing. Expression of mRNA in the proband and her father, who also carries the mutation, were almost half of proband's mother. Indicating Mybpc3 (p.Ala58Val) mutation affected its expression, and may play crucial roles for heritable BAV.

CONCLUSIONS

To our knowledge, this is the first time to report Mybpc3 heterozygous variant associated with heritable BAV. The relationship between the location of Mybpc3 mutation and BAV may provide a novel perspective of understanding this disorder.

New Concepts in the Development and Malformation of the Arterial Valves

Although in many ways the arterial and atrioventricular valves are similar, both being derived for the most part from endocardial cushions, we now know that the arterial valves and their surrounding structures are uniquely dependent on progenitors from both the second heart field (SHF) and neural crest cells (NCC). Here, we will review aspects of arterial valve development, highlighting how our appreciation of NCC and the discovery of the SHF have altered our developmental models. We will highlight areas of research that have been particularly instructive for understanding how the leaflets form and remodel, as well as those with limited or conflicting results. With this background, we will explore how this developmental knowledge can help us to understand human valve malformations, particularly those of the bicuspid aortic valve (BAV). Controversies and the current state of valve genomics will be indicated.

Age, Sex, and Valve Phenotype Differences in Fibro-Calcific Remodeling of Calcified Aortic Valve

Background

In calcific aortic valve disease on tricuspid aortic valves (TAVs), men have higher aortic valve calcification and less fibrosis than women. However, little is known in bicuspid aortic valves (BAV). We thus aimed to investigate the impact of age, sex, and valve phenotype (TAVs versus BAVs) on fibro‐calcific remodeling in calcific aortic valve disease.

Methods and Results

We included 2 cohorts: 411 patients who underwent multidetector computed tomography (37% women) for aortic valve calcification density assessment and 138 explanted aortic valves (histological cohort; 50% women). The cohorts were divided in younger (<60 years old) or older patients with BAV (≥60 years old), and TAV patients. In each group, women and men were matched. Women presented less aortic valve calcification density than men in each group of the multidetector computed tomography cohort (all P≤0.01). Moreover, in women, younger patients with BAV had the lowest aortic valve calcification density (both P=0.02). In multivariate analysis, aortic valve calcification density correlated with age (β estimate±standard error: 6.5±1.8; P=0.0004) and male sex (109.2±18.4; P<0.0001), and there was a trend with TAVs (41.5±23.0; P=0.07). Women presented a higher collagen content than men (77.8±10.8 versus 69.9±12.9%; P<0.001) in the entire cohort. In women, younger patients with BAV had denser connective tissue than TAV and older patients with BAV (both P≤0.05), while no difference was observed between men.

Conclusions

In calcific aortic valve disease, women had less calcification and more fibrotic remodeling than men, regardless of the phenotype of the valve or age of the patient. Moreover, younger women with BAVs had less valve calcification. Thus, mineralization/fibrosis of the aortic valve is likely to have sex/age‐specific mechanisms and be influenced by the valve morphology.

Piezo1 is required for outflow tract and aortic valve development

AIMS

During embryogenesis, the onset of circulatory blood flow generates a variety of hemodynamic forces which reciprocally induce changes in cardiovascular development and performance. It has been known for some time that these forces can be detected by as yet unknown mechanosensory systems which in turn promote cardiogenic events such as outflow tract and aortic valve development. PIEZO1 is a mechanosensitive ion channel present in endothelial cells where it serves to detect hemodynamic forces making it an ideal candidate to play a role during cardiac development. We sought to determine whether PIEZO1 is required for outflow tract and aortic valve development.

METHODS AND RESULTS

By analysing heart development in zebrafish we have determined that piezo1 is expressed in the developing outflow tract where it serves to detect hemodynamic forces. Consequently, disrupting Piezo1 signalling leads to defective outflow tract and aortic valve development and indicates this gene may be involved in the etiology of congenital heart diseases. Based on these findings, we analysed genomic data generated from patients who suffer from left ventricular outflow tract obstructions (LVOTO) and identified 3 probands who each harboured potentially pathogenic variants in PIEZO1. Subsequent in vitro and in vivo assays indicates that these variants behave as dominant negatives leading to an inhibition of normal PIEZO1 mechanosensory activity. Expressing these dominant negative PIEZO1 variants in zebrafish endothelium leads to defective aortic valve development.

CONCLUSION

These data indicate that the mechanosensitive ion channel piezo1 is required for outflow tract and aortic valve development.

The importance of genetics and genetic counselors in the evaluation of patients with bicuspid aortic valve and aortopathy

PURPOSE OF REVIEW

Bicuspid aortic valve (BAV) is a common congenital heart defect, with an estimated frequency of 1-2% in the general population. BAV may occur as an isolated finding or as a feature of certain syndromes. This article discusses potential genetic causes of BAV, includes a list of current known and candidate genes associated with BAV, provides a hypothetical case demonstrating the importance of genetic testing and cascade screening, and highlights the value of genetic counselors specializing in cardiovascular genetics.

RECENT FINDINGS

Individuals with BAV are at significantly increased risk of progressive aortic valve disease and aortic root aneurysms. There is high heritability associated with BAV, and several specific genes have recently been associated with BAV. There is wide phenotypic variability among BAV malformations, including which cusps are involved and the degree of aortic root involvement. Genotype-phenotype correlations exist that impact treatment recommendations. Genetic testing can reduce morbidity and mortality by guiding management strategies and identifying asymptomatic relatives before significant complications occur.

SUMMARY

Identifying cases of BAV with an identifiable genetic cause can significantly impact patients and family members. The list of associated genes is constantly growing. Genetic counselors have an important role in the evaluation of families at risk of BAV.

An overview of the molecular mechanisms underlying development and progression of bicuspid aortic valve disease

Bicuspid aortic valve (BAV) is a common congenital heart malformation frequently associated with the development of aortic valve diseases and severe aortopathy, such as aortic dilatation, aneurysm and dissection. To date, different genetic loci have been identified in syndromic and non- syndromic forms of BAV. Among these, genes involved in the regulation of extracellular matrix remodelling, epithelial to mesenchymal transition and nitric oxide metabolism appear to be the main contributors to BAV pathogenesis. However, no- single gene model explains BAV inheritance, suggesting that more factors are simultaneously involved. In this regard, characteristic epigenetic and immunological profiles have been documented to contradistinguish BAV individuals. In this review, we provide a comprehensive overview addressing molecular mechanisms involved in BAV development and progression.

New imaging techniques project the cellular and molecular alterations underlying bicuspid aortic valve development

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac malformation associated with an increased lifetime risk and a high rate of surgically-relevant valve deterioration and aortic dilatation. Genomic data revealed that different genes are associated with BAV. A dominant genetic factor for the recent past was the basis to the recommendation for a more extensive aortic intervention. However very recent evidence that hemodynamic stressors and alterations of wall shear stress play an important role independent from the genetic trait led to more conservative treatment recommendations. Therefore, there is a current need to improve the ability to risk stratify BAV patients in order to obtain an early detection of valvulopathy and aortopathy while also to predict valve dysfunction and/or aortic disease development. Imaging studies based on new cutting-edge technologies, such us 4-dimensional (4D) flow magnetic resonance imaging (MRI), two-dimensional (2D) or three-dimensional (3D) speckle-tracking imaging (STI) and computation fluid dynamics, combined with studies demonstrating new gene mutations, specific signal pathways alterations, hemodynamic influences, circulating biomarkers modifications, endothelial progenitor cell impairment and immune/inflammatory response, all detected BAV valvulopathy progression and aortic wall abnormality. Overall, the main purpose of this review article is to merge the evidences of imaging and basic science studies in a coherent hypothesis that underlies and thus projects the development of both BAV during embryogenesis and BAV-associated aortopathy and its complications in the adult life, with the final goal to identifying aneurysm formation/rupture susceptibility to improve diagnosis and management of patients with BAV-related aortopathy.

Association of NKX2-5, GATA4, and TBX5 polymorphisms with congenital heart disease in Egyptian children

Background

Several genes encoding transcription factors are known to be the primary cause of congenital heart disease. NKX2‐5 and GATA4 were the first congenital heart disease–causing genes identified by linkage analysis. This study designed to study the association of five single–nucleotide variants of NKX2‐5, GATA4, and TBX5 genes with sporadic nonsyndromic cases of a congenital cardiac septal defect in Egyptian children.

Methods

Venous blood samples from 150 congenital heart disease children (including a ventricular septal defect, atrial septal defect, tetralogy of Fallot, and patent ductus arteriosus) and 90 apparently healthy of matched age and sex were studied by polymerase chain reaction followed by direct sequencing in order to study two single–nucleotide variants of NKX2‐5 (rs2277923, rs28936670), two single–nucleotide variants of GATA4 (rs368418329, rs56166237) and one single–nucleotide variant TBX5 (rs6489957). The distribution of genotype and allele frequency in the congenital heart diseases (CHD) group and control group were analyzed.

Results

We found different genotype frequencies of the two variants of NKX2‐5, as CT genotype of rs2277923 was present in 58% and 36% in cases and control respectively, and TT genotype present in 6% of the cases. Also regarding missense variant rs28936670, heterozygous AG presented in 82% of the cases. Also, we observed a five prime UTR variant rs368418329, GT (42% of the cases) and GG (46% of the cases) genotypes showed the most frequent presentation in cases. While regarding a synonymous variant rs56166237, GT and GG were the most presented in cases (41.4%, 56% respectively) in contrast to control group (20%, 1.7% respectively). Also, a synonymous variant in TBX5, the distribution of genotype frequency was significantly different between the CHD group and control group. CT genotype of TBX5 ‐rs6489957 was found in 12 ASD, 24 VSD, six PDA, three aortic coarctation and nine fallot that represent 42% of the cases.

Conclusions

Significantly higher frequency of different allelle of five variants was observed in cases when compared to the control group, with significant risky effect for the development of septal defect. In addition to two polymorphisms of NKX2‐5 (rs2277923, rs28936670) variant in the cardiac septal defect, two variants in GATA4 (rs368418329, rs56166237) and one variant in TBX5 (rs6489957) seem to have a role in the pathogenesis of congenital heart disease.

NR2F2 loss‑of‑function mutation is responsible for congenital bicuspid aortic valve

Congenital bicuspid aortic valve (BAV) represents the most common type of cardiac birth defect affecting 0.4‑2% of the general population, and accounts for a markedly increased incidence of life‑threatening complications, including valvulopathy and aortopathy. Accumulating evidence has demonstrated the genetic basis of BAV. However, the genetic basis for BAV in the majority of cases remains to be elucidated. In the present study, the coding regions and splicing donors/acceptors of the nuclear receptor subfamily 2 group F member 2 (NR2F2) gene, which encodes a transcription factor essential for proper cardiovascular development, were sequenced in 176 unrelated cases of congenital BAV. The available family members of the proband carrying an identified NR2F2 mutation and 280 unrelated, sex‑ and ethnicity‑matched healthy individuals as controls were additionally genotyped for NR2F2. The functional effect of the mutation was characterized using a dual‑luciferase reporter assay system. As a result, a novel heterozygous NR2F2 mutation, NM_021005.3: c.288C>A; p.(Cys96*), was identified in a family with BAV, which was transmitted in an autosomal dominant mode with complete penetrance. The nonsense mutation was absent from the 560 control chromosomes. Functional analysis identified that the mutant NR2F2 protein had no transcriptional activity. Furthermore, the mutation disrupted the synergistic transcriptional activation between NR2F2 and transcription factor GATA‑4, another transcription factor that is associated with BAV. These findings suggested NR2F2 as a novel susceptibility gene of human BAV, which reveals a novel molecular pathogenesis underpinning BAV.

Bicuspid Aortic Valve: An Update in Morphology, Genetics, Biomarker, Complications, Imaging Diagnosis and Treatment

The bicuspid aortic valve, a kind of heart disease that comes from parents, has been paid attention around the world. Although most bicuspid aortic valve (BAV) patients will suffer from some complications including aortic stenosis, aortic regurgitation, endocarditis, and heart dysfunction in the late stage of the disease, there is none symptom in the childhood, which restrains us to diagnose and treatment in the onset phase of BAV. Hemodynamic abnormalities induced by the malformations of the valves in BAV patients for a long time will cause BAV-associated aortopathy: including progress aortic dilation, aneurysm, dissection and rupture, cardiac cyst and even sudden death. At present, preventive surgical intervention is the only effective method used in this situation and the diameter of the aorta is the primary reference criterion for surgery. And the treatment effects are always not satisfactory for patients and clinicians. Therefore, we need more methods to evaluate the progression of BAV and the surgery value and the appropriate intervention time by combining basic research with clinical treatment. In this review, advances in morphology, genetic, biomarkers, diagnosis and treatments are summarized, which expects to provide an update about BAV. It is our supreme expectations to provide some evidences for BAV early screening and diagnosis, and in our opinion, personalized surgical strategy is the trend of future BAV treatment.

Variants in cardiac GATA genes associated with bicuspid aortic valve

BACKGROUND

Bicuspid aortic valve (BAV) is a heterogeneous and still not fully understood condition, with diverse genetic aetiology and associated phenotypes ranging from aortic stenosis or regurgitation to aneurysm and dissection. Several genes have been associated with the presence of BAV, notably some members of the GATA family of transcription factors that play important roles in cardiac embryogenesis.

METHODS

A case-control study with 122 unrelated and ethnically matched patients with bicuspid and 154 with tricuspid aortic valve was performed. All exons of GATA4, GATA5, and GATA6 genes were sequenced searching for variants. Frequencies were compared and functional effects of rare variants were analysed by informatic prediction tools.

RESULTS

Four rare and potentially pathogenic variants were identified in only five sporadic cases: a missense p.Arg202Gln (rs782614097) in GATA5 and three synonymous variants, p.Cys274= (rs55980825) and p.His302= (rs201516339) in GATA4, and p.Asn458= (rs143026087) in GATA6. Minor alleles of p.His302=, p.Arg202Gln and rs3764962 are enriched in BAV patients compared to ExAC database (P = 0.01, 0.03, and 0.01 respectively). In addition, a common polymorphism in GATA5 (p.Asp203=, rs41305803) is associated with BAV showing a protective effect in carriers of the minor allele (OR [95%CI] = 0.45[0.25-0.81]; P = 0.004).

CONCLUSION

This study associates additional genetic variants in GATA4 and GATA5 with BAV, supporting the implication of these genes in the development of this valvulopathy. The discovery of all the genetic factors involved will contribute to a better understanding of the process and, therefore, to detect a genetic predisposition and even to the identification of therapeutic targets.

Bicuspid Aortic Valve: Role of Multiple Gene Variants in Influencing the Clinical Phenotype

Background. Bicuspid aortic valve (BAV) is a common congenital heart defect with increased prevalence of aortic dilatation and dissection. BAV has an autosomal dominant pattern of inheritance with reduced penetrance and variable expressivity. BAV has been described as an isolated trait or associated with other clinical manifestations in syndromic conditions. Identification of a syndromic condition in a BAV patient is clinically relevant in order to personalize indication to aortic surgery. We aimed to point out how genetic diagnosis by next-generation sequencing (NGS) can improve management of a patient with complex BAV clinical picture. Methods and Results. We describe a 45-year-old Caucasian male with BAV, thoracic aortic root and ascending aorta dilatation, and connective features evocative but inconclusive for clinical diagnosis of Marfan syndrome (MFS). Targeted (91 genes) NGS was used. Proband genetic variants were investigated in first-degree relatives. Proband carried 5 rare variants in 4 genes: FBN1(p.Asn542Ser and p.Lys2460Arg), NOTCH1(p.Val1739Met), LTBP1(p.Arg1330Gln), and TGFBR3(p.Arg423Trp). The two FBN1 variants were inherited in cis by the mother, showing systemic features evocative of MFS, but with a milder phenotype than that observed in the proband. Careful clinical observation along with the presence of the FBN1 variants allowed diagnosis of MFS in the proband and in his mother. NOTCH1 variant was found in mother and brother, not exhibiting BAV, thus not definitely supporting/excluding association with BAV. Interestingly, the proband, his brother and father, all showing root dilatation, and his sister, with upper range aortic root dimension, were carriers of a TGFBR3 variant. LTBP1 might also modulate the vascular phenotype. Conclusions. Our results underline the usefulness of NGS together with family evaluation in diagnosis of patients with monogenic traits and overlapping clinical manifestations due to contribution of the same genes and/or presence of comorbidities determined by different genes.

Genetics of bicuspid aortic valve aortopathy

PURPOSE OF REVIEW

The incidence of aortic dilation and acute complications (rupture and dissection) is higher in patients with a bicuspid aortic valve (BAV), the most frequent congenital heart defect.The present review focuses on the current knowledge in the genetics of BAV, emphasizing the clinical implications for early detection and personalized care.

RECENT FINDINGS

BAV is a highly heritable trait, but the genetic causes remain largely elusive. NOTCH1 is the only proven candidate gene to be associated with both familial and sporadic BAV. Other genes have been reported to be associated with BAV, but some of these associations may result from coexisting disease.The application of modern high-throughput technologies (next generation sequencing, genome-wide copy number and genome-wide methylation arrays) have begun to dissect the genetic heterogeneity underlying BAV as well as the diverse molecular pathways involved in the progression of BAV aortopathy.

SUMMARY

The clinical variability seen in BAV aortopathy, in terms of phenotype and natural/clinical history, suggests complex interactions between primary genetic defects, other modifier genes, epigenetic factors (DNA methylation or histone modifications, microRNA) and environmental factors (disturbed flow). Integrated, more comprehensive studies are needed for elucidating these connections to develop more individualized and accurate risk assessment methods.

Genomics and Epigenomics of Congenital Heart Defects: Expert Review and Lessons Learned in Africa

Congenital heart defects (CHD) are structural malformations found at birth with a prevalence of 1%. The clinical trajectory of CHD is highly variable and thus in need of robust diagnostics and therapeutics. Major surgical interventions are often required for most CHDs. In Africa, despite advances in life sciences infrastructure and improving education of medical scholars, the limited clinical data suggest that CHD detection and correction are still not at par with the rest of the world. But the toll and genetics of CHDs in Africa has seldom been systematically investigated. We present an expert review on CHD with lessons learned on Africa. We found variable CHD phenotype prevalence in Africa across countries and populations. There are important gaps and paucity in genomic studies of CHD in African populations. Among the available genomic studies, the key findings in Africa were variants in GATA4 (P193H), MTHFR 677TT, and MTHFR 1298CC that were associated with atrial septal defect, ventricular septal defect (VSD), Tetralogy of Fallot (TOF), and patent ductus arteriosus phenotypes and 22q.11 deletion, which is associated with TOF. There were no data on epigenomic association of CHD in Africa, however, other studies have shown an altered expression of miR-421 and miR-1233-3p to be associated with TOF and hypermethylation of CpG islands in the promoter of SCO2 gene also been associated with TOF and VSD in children with non-syndromic CHD. These findings signal the urgent need to develop and implement genetic and genomic research on CHD to identify the hereditary and genome-environment interactions contributing to CHD. These projected studies would also offer comparisons on CHD pathophysiology between African and other populations worldwide. Genomic research on CHD in Africa should be developed in parallel with next generation technology policy research and responsible innovation frameworks that examine the social and political factors that shape the emergence and societal embedding of new technologies.

GATA6 loss-of-function mutation contributes to congenital bicuspid aortic valve

Congenital bicuspid aortic valve (BAV), the most common form of birth defect in humans, is associated with substantial morbidity and mortality. Increasing evidence demonstrates that genetic risk factors play a key role in the pathogenesis of BAV. However, BAV is a genetically heterogeneous disease and the genetic determinants underpinning BAV in an overwhelming majority of patients remain unknown. In the present study, the coding exons and flanking introns of the GATA6 gene, which encodes a zinc-finger transcription factor essential for the normal development of the aortic valves, were sequenced in 152 unrelated patients with congenital BAV. The available relatives of a proband harboring an identified GATA6 mutation and 200 unrelated, ethnically matched healthy individuals used as controls were also genotyped for GATA6. The functional characteristics of the mutation were analyzed by using a dual-luciferase reporter assay system. As a result, a novel heterozygous GATA6 mutation, p.E386X, was identified in a family with BAV transmitted in an autosomal dominant mode. The nonsense mutation was absent in 400 control chromosomes. Biological assays revealed that the mutant GATA6 protein had no transcriptional activity compared with its wild-type counterpart. Furthermore, the mutation disrupted the synergistic transcriptional activation between GATA6 and GATA4, another transcription factor causally linked to BAV. In conclusion, this study firstly associates GATA6 loss-of-function mutation with enhanced susceptibility to familial BAV, which provides novel insight into the molecular mechanism of BAV, implying potential implications for genetic counseling and personalized management of BAV patients.

A Typical Immune T/B Subset Profile Characterizes Bicuspid Aortic Valve: In an Old Status?

Bicuspid valve disease is associated with the development of thoracic aortic aneurysm. The molecular mechanisms underlying this association still need to be clarified. Here, we evaluated the circulating levels of T and B lymphocyte subsets associated with the development of vascular diseases in patients with bicuspid aortic valve or tricuspid aortic valve with and without thoracic aortic aneurysm. We unveiled that the circulating levels of the MAIT, CD4+IL−17A+, and NKT T cell subsets were significantly reduced in bicuspid valve disease cases, when compared to tricuspid aortic valve cases in either the presence or the absence of thoracic aortic aneurysm. Among patients with tricuspid aortic valve, these cells were higher in those also affected by thoracic aortic aneurysm. Similar data were obtained by examining CD19+ B cells, naïve B cells (IgD+CD27−), memory unswitched B cells (IgD+CD27+), memory switched B cells (IgD−CD27+), and double-negative B cells (DN) (IgD−CD27−). These cells resulted to be lower in subjects with bicuspid valve disease with respect to patients with tricuspid aortic valve. In whole, our data indicate that patients with bicuspid valve disease show a quantitative reduction of T and B lymphocyte cell subsets. Future studies are encouraged to understand the molecular mechanisms underlying this observation and its pathophysiological significance.

DNA methylome analysis reveals distinct epigenetic patterns of ascending aortic dissection and bicuspid aortic valve

Aims

Epigenetics may mediate the effects of environmental risk factors on disease, including heart disease. Thus, measuring the DNA methylome offers the opportunity to identify novel disease biomarkers and novel insights into disease mechanisms. The DNA methylation landscape of ascending aortic dissection (AD) and bicuspid aortic valve (BAV) with aortic aneurysmal dilatation remain uncharacterized. The present study aimed to explore the genome-wide DNA methylation landscape underpinning these two diseases.

Methods and results

We used Illumina 450k DNA methylation beadarrays to analyse 21 ascending aorta samples, including 10 cases with AD, 5 with BAV and 6 healthy controls. We adjusted for intra-sample cellular heterogeneity, providing the first unbiased genome-wide exploration of the DNA methylation landscape underpinning these two diseases. We discover that both diseases are characterized by loss of DNA methylation at non-CpG sites. We validate this non-CpG hypomethylation signature with pyrosequencing. In contrast to non-CpGs, AD and BAV exhibit distinct DNA methylation landscapes at CpG sites, with BAV characterized mainly by hypermethylation of EZH2 targets. In the case of AD, integrative DNA methylation gene expression analysis reveals that AD is characterized by a dedifferentiated smooth muscle cell phenotype. Our integrative analysis further reveals hypomethylation associated overexpression of RARA in AD, a pattern which is also seen in cells exposed to smoke toxins.

Conclusion

Our data supports a model in which increased cellular proliferation in AD and BAV underpins loss of methylation at non-CpG sites. Our data further supports a model, in which AD is associated with an inflammatory vascular remodeling process, possibly mediated by the epigenome and linked to environmental risk factors such as smoking.

GATA4 Loss-of-Function Mutation and the Congenitally Bicuspid Aortic Valve

Aggregating evidence suggests that genetic determinants play a pivotal role in the pathogenesis of the congenitally bicuspid aortic valve (BAV). BAV is of pronounced genetic heterogeneity, and the genetic components underlying BAV in an overwhelming majority of patients remain elusive. In the current study, the whole coding exons and adjacent introns, as well as 5' and 3' untranslated regions of the GATA4 gene, which codes for a zinc-finger transcription factor crucial for the normal development of the aortic valve, were screened by direct sequencing in 150 index patients with congenital BAV. The available family members of an identified mutation carrier and 300 unrelated, ethnically matched healthy individuals used as controls were also genotyped for GATA4. The functional effect of the mutation was characterized using a dual-luciferase reporter assay system. As a result, a novel heterozygous GATA4 mutation, p.E147X, was identified in a family with BAV transmitted in an autosomal dominant pattern. The nonsense mutation was absent in 600 control chromosomes. Functional deciphers revealed that the mutant GATA4 protein lost transcriptional activity compared with its wild-type counterpart. Furthermore, the mutation disrupted the synergistic transcriptional activation between GATA4 and NKX2.5, another transcription factor responsible for BAV. In conclusion, this study associates the GATA4 loss-of-function mutation with enhanced susceptibility to a BAV, thus providing novel insight into the molecular mechanism underpinning the BAV.

Deficiency of Natriuretic Peptide Receptor 2 Promotes Bicuspid Aortic Valves, Aortic Valve Disease, Left Ventricular Dysfunction, and Ascending Aortic Dilatations in Mice

RATIONALE

Aortic valve disease is a cell-mediated process without effective pharmacotherapy. CNP (C-type natriuretic peptide) inhibits myofibrogenesis and osteogenesis of cultured valve interstitial cells and is downregulated in stenotic aortic valves. However, it is unknown whether CNP signaling regulates aortic valve health in vivo.

OBJECTIVE

The aim of this study is to determine whether a deficient CNP signaling axis in mice causes accelerated progression of aortic valve disease.

METHODS AND RESULTS

In cultured porcine valve interstitial cells, CNP inhibited pathological differentiation via the guanylate cyclase NPR2 (natriuretic peptide receptor 2) and not the G-protein-coupled clearance receptor NPR3 (natriuretic peptide receptor 3). We used Npr2^+/- and Npr2^+/-;Ldlr^-/- mice and wild-type littermate controls to examine the valvular effects of deficient CNP/NPR2 signaling in vivo, in the context of both moderate and advanced aortic valve disease. Myofibrogenesis in cultured Npr2^+/- fibroblasts was insensitive to CNP treatment, whereas aged Npr2^+/- and Npr2^+/-;Ldlr-/- mice developed cardiac dysfunction and ventricular fibrosis. Aortic valve function was significantly impaired in Npr2^+/- and Npr2^+/-;Ldlr^-/- mice versus wild-type littermates, with increased valve thickening, myofibrogenesis, osteogenesis, proteoglycan synthesis, collagen accumulation, and calcification. 9.4% of mice heterozygous for Npr2 had congenital bicuspid aortic valves, with worse aortic valve function, fibrosis, and calcification than those Npr2^+/- with typical tricuspid aortic valves or all wild-type littermate controls. Moreover, cGK (cGMP-dependent protein kinase) activity was downregulated in Npr2^+/- valves, and CNP triggered synthesis of cGMP and activation of cGK1 (cGMP-dependent protein kinase 1) in cultured porcine valve interstitial cells. Finally, aged Npr2^+/-;Ldlr^-/- mice developed dilatation of the ascending aortic, with greater aneurysmal progression in Npr2^+/- mice with bicuspid aortic valves than those with tricuspid valves.

CONCLUSIONS

Our data establish CNP/NPR2 signaling as a novel regulator of aortic valve development and disease and elucidate the therapeutic potential of targeting this pathway to arrest disease progression.

Targeted next-generation sequencing identified ADAMTS5 as novel genetic substrate in patients with bicuspid aortic valve

BACKGROUND

Bicuspid Aortic Valve (BAV) is the most common congenital heart disease, affecting >1% of the general population. Up to date, three genes, NOTCH1, GATA5 and SMAD6, have been linked to the isolated form of BAV. However, potential genetic determinants remain largely unknown in most BAV patients.

MATERIAL AND METHODS

Targeted next-generation sequencing of 7 BAV candidate genes (NOTCH1, GATA5, SMAD6, NOS3, ADAMTS5, Alk2 and SMAD2) was performed in 32 BAV patients. Additional 35 BAV patients and 238 tricuspid aortic valve (TAV) patients, consisting of 107 patients from the transcatheter aortic valve implantation (TAVI) registry and 131 patients from the coronary artery disease (CAD) registry, were selected for further genotyping.

RESULTS

We found 2 rare non-synonymous variants in 2/7 genes in 3 BAV patients: one was NOTCH1:c.4297G>A and the other one was ADMTS5:c.935C>A that shared by two patients. NOTCH1:c.4297G>A has not been reported previously. ADMTS5:c.935C>A was predicted to be pathogenic by all applied algorithms. Alignment of protein sequences from all available species revealed that ADMTS5:p.Arg312Leu, produced by ADMTS5:c.935C>A, is located in a highly conserved region. The minor allele frequency of ADMTS5:c.935C>A in BAV patients was significantly higher than the matched population in TAV group (0.015 vs. 0, P=0.048).

CONCLUSION

Our results suggested that ADMTS5:c.935C>A are potentially associated with BAV. Further studies, such as large sample case-control replication test and functional research, are needed to explore the role of this rare variant in the development of BAV.

Pathogenic Mechanisms of Bicuspid Aortic Valve Aortopathy

Bicuspid aortic valve (BAV) is the most common congenital valvular defect and is associated with ascending aortic dilation (AAD) in a quarter of patients. AAD has been ascribed both to the hemodynamic consequences of normally functioning and abnormal BAV morphology, and to the effect of rare and common genetic variation upon function of the ascending aortic media. AAD manifests in two overall and sometimes overlapping phenotypes: that of aortic root aneurysm, similar to the AAD of Marfan syndrome; and that of tubular AAD, similar to the AAD seen with tricuspid aortic valves (TAVs). These aortic phenotypes appear to be independent of BAV phenotype, have different embryologic origins and have unique etiologic factors, notably, regarding the role of hemodynamic changes inherent to the BAV phenotype. Further, in contrast to Marfan syndrome, the AAD seen with BAV is infrequently present as a strongly inherited syndromic phenotype; rather, it appears to be a less-penetrant, milder phenotype. Both reduced levels of normally functioning transcriptional proteins and structurally abnormal proteins have been observed in aneurysmal aortic media. We provide evidence that aortic root AAD has a stronger genetic etiology, sometimes related to identified common non-coding fibrillin-1 (FBN1) variants and other aortic wall protein variants in patients with BAV. In patients with BAV having tubular AAD, we propose a stronger hemodynamic influence, but with pathology still based on a functional deficit of the aortic media, of genetic or epigenetic etiology. Although it is an attractive hypothesis to ascribe common mechanisms to BAV and AAD, thus far the genetic etiologies of AAD have not been associated to the genetic etiologies of BAV, notably, not including BAV variants in NOTCH1 and GATA4.

Genetic Bases of Bicuspid Aortic Valve: The Contribution of Traditional and High-Throughput Sequencing Approaches on Research and Diagnosis

Bicuspid aortic valve (BAV) is a common (0.5-2.0% of general population) congenital heart defect with increased prevalence of aortic dilatation and dissection. BAV has an autosomal dominant inheritance with reduced penetrance and variable expressivity. BAV has been described as an isolated trait or associated with syndromic conditions [e.g., Marfan Marfan syndrome or Loeys-Dietz syndrome (MFS, LDS)]. Identification of a syndromic condition in a BAV patient is clinically relevant to personalize aortic surgery indication. A 4-fold increase in BAV prevalence in a large cohort of unrelated MFS patients with respect to general population was reported, as well as in LDS patients (8-fold). It is also known that BAV is more frequent in patients with thoracic aortic aneurysm (TAA) related to mutations in ACTA2, FBN1, and TGFBR2 genes. Moreover, in 8 patients with BAV and thoracic aortic dilation, not fulfilling the clinical criteria for MFS, FBN1 mutations in 2/8 patients were identified suggesting that FBN1 or other genes involved in syndromic conditions correlated to aortopathy could be involved in BAV. Beyond loci associated to syndromic disorders, studies in humans and animal models evidenced/suggested the role of further genes in non-syndromic BAV. The transcriptional regulator NOTCH1 has been associated with the development and acceleration of calcium deposition. Genome wide marker-based linkage analysis demonstrated a linkage of BAV to loci on chromosomes 18, 5, and 13q. Recently, a role for GATA4/5 in aortic valve morphogenesis and endocardial cell differentiation has been reported. BAV has also been associated with a reduced UFD1L gene expression or involvement of a locus containing AXIN1/PDIA2. Much remains to be understood about the genetics of BAV. In the last years, high-throughput sequencing technologies, allowing the analysis of large number of genes or entire exomes or genomes, progressively became available. The latter issue together with the development of "BigData" analysis methods improving their interpretation and integration with clinical data represents a promising opportunity to increase the disease knowledge and diagnosis in monogenic and multifactorial complex traits. This review summarized the main knowledge on the BAV genetic bases, the role of genetic diagnosis in BAV patient managements and the crucial challenges for the comprehension of genetics of BAV in research and diagnosis.

HAND1 Loss-of-Function Mutation Causes Tetralogy of Fallot

As the most prevalent form of birth defect in humans worldwide, congenital heart disease (CHD) is responsible for substantial morbidity and is still the leading cause of birth defect-related demises. Increasing evidence demonstrates that genetic defects play an important role in the pathogenesis of CHD, and mutations in multiple genes, especially in those coding for cardiac core transcription factors, have been causally linked to various CHDs. Nevertheless, CHD is a genetically heterogeneous disease and the genetic determinants underpinning CHD in an overwhelming majority of patients remain elusive. In the current study, genomic DNA was extracted from venous blood samples of 165 unrelated patients with CHD, and the coding exons and splicing junction sites of the HAND1 gene, which encodes a basic helix-loop-helix transcription factor essential for cardiovascular development, were sequenced. As a result, a novel heterozygous mutation, p.R118C, was identified in a patient with tetralogy of Fallot (TOF). The missense mutation, which was absent in 600 referential chromosomes, altered the amino acid that was completely conserved evolutionarily. Biological assays with a dual-luciferase reporter assay system revealed that the R118C-mutant HAND1 protein had significantly reduced transcriptional activity when compared with its wild-type counterpart. Furthermore, the mutation significantly decreased the synergistic activation of a downstream target gene between HAND1 and GATA4, another cardiac core transcription factor associated with TOF. To our knowledge, this is the first report on the association of a HAND1 loss-of-function mutation with enhanced susceptibility to TOF in humans. The findings provide novel insight into the molecular etiology underlying TOF, suggesting potential implications for the improved prophylactic and therapeutic strategies for TOF.

Array comparative genomic hybridization and genomic sequencing in the diagnostics of the causes of congenital anomalies

The aim of this review is to provide the current state of knowledge about the usefulness of modern genetic technologies in uncovering the causality of isolated and multiple congenital anomalies. Array comparative genomic hybridization and next-generation sequencing have revolutionized the clinical approach to patients with these phenotypes. Both technologies enable early diagnosis, especially in clinically challenging newborn populations, and help to uncover genetic defects associated with various phenotypes. The application of both complementary methods could assist in identifying many variants that may simultaneously be involved in the development of a number of isolated or multiple congenital anomalies. Both technologies carry serious variant misinterpretation risks as well. Therefore, the methods of variant classification and accessible variant databases are mentioned. A useful strategy of clinical genetic testing with the application of both methodologies is presented. Finally, future directions and challenges are briefly commented on in this review.