CELSR1 Risk Alleles in Familial Bicuspid Aortic Valve and Hypoplastic Left Heart Syndrome

Deciphering the digenic architecture of congenital heart disease using trio exome sequencing data

Congenital heart disease (CHD) is the most common congenital anomaly and a leading cause of infant morbidity and mortality. Despite extensive exploration of the monogenic causes of CHD over the last decades, ∼55% of cases still lack a molecular diagnosis. Investigating digenic interactions, the simplest form of oligogenic interactions, using high-throughput sequencing data can elucidate additional genetic factors contributing to the disease. Here, we conducted a comprehensive analysis of digenic interactions in CHD by utilizing a large CHD trio exome sequencing cohort, comprising 3,910 CHD and 3,644 control trios. We extracted pairs of presumably deleterious rare variants observed in CHD-affected and unaffected children but not in a single parent. Burden testing of gene pairs derived from these variant pairs revealed 29 nominally significant gene pairs. These gene pairs showed a significant enrichment for known CHD genes (p < 1.0 × 10-4) and exhibited a shorter average biological distance to known CHD genes than expected by chance (p = 3.0 × 10-4). Utilizing three complementary biological relatedness approaches including network analyses, biological distance calculations, and candidate gene prioritization methods, we prioritized 10 final gene pairs that are likely to underlie CHD. Analysis of bulk RNA-sequencing data showed that these genes are highly expressed in the developing embryonic heart (p < 1 × 10-4). In conclusion, our findings suggest the potential role of digenic interactions in CHD pathogenesis and provide insights into unresolved molecular diagnoses. We suggest that the application of the digenic approach to additional disease cohorts will significantly enhance genetic discovery rates.

Identification of Hypoplastic Left Heart Genotypes and Phenotypes; The Window toward Future Cell-Based Therapy: A Narrative Review

Hypoplastic left heart syndrome (HLHS) is a prevalent and lethal type of single ventricle anomaly. During early prenatal evaluations, left heart hypoplasia may be neglected due to its progressive features. It is a heterogeneous congenital heart disease with different phenotypes. Currently, there is no definite treatment for HLHS. This is in part due to its heterogeneous phenotypes that require different management. In addition, hindrances in recognizing the etiologic factors do not allow early preventive or therapeutic procedures. Phenotypic determination is fundamental to identifying the etiologic factors and therapeutic strategies. This review article introduces comprehensive information about different phenotypes and genotypes of HLHS and their novel molecular strategy. Genetic defects and flow-mediated mechanisms are the main known factors of HLHS. Recent studies reported additional data about its nonmendelian genetic origins associated with heterogeneous phenotypes. The genetic defects influence endocardium or cardiomyocyte development to yield early or late valve deformities and myocardial malformations. The new molecular therapeutic methods are essentially based on genetic etiologies. The principal therapeutic purpose is reinforcing the function of the right ventricle in patients with nonfunctional left ventricles. The ultimate desire is to create a biventricular heart in selected cases.

Feto-placental and coronary endothelial genes implicated in miscarriage, congenital heart disease and stillbirth, a systematic review and meta-analysis

The first trimester placenta is very rarely investigated for placental vascular formation in developmental or diseased contexts. Defects in placental formation can cause heart defects in the fetus, and vice versa. Determining the causality is therefore difficult as both organs develop concurrently and express many of the same genes. Here, we performed a systematic review to determine feto-placental and coronary endothelial genes implicated in miscarriages, stillbirth and congenital heart defects (CHD) from human genome wide screening studies. 4 single cell RNAseq datasets from human first/early second trimester cardiac and placental samples were queried to generate a list of 1187 endothelial genes. This broad list was cross-referenced with genes implicated in the pregnancy disorders above. 39 papers reported feto-placental and cardiac coronary endothelial genes, totalling 612 variants. Vascular gene variants were attributed to the incidence of miscarriage (8 %), CHD (4 %) and stillbirth (3 %). The most common genes for CHD (NOTCH, DST, FBN1, JAG1, CHD4), miscarriage (COL1A1, HERC1), and stillbirth (AKAP9, MYLK), were involved in blood vessel and cardiac valve formation, with roles in endothelial differentiation, angiogenesis, extracellular matrix signaling, growth factor binding and cell adhesion. NOTCH1, AKAP12, CHD4, LAMC1 and SOS1 showed greater relative risk ratios with CHD. Many of the vascular genes identified were expressed highly in both placental and heart EC populations. Both feto-placental and cardiac vascular genes are likely to result in poor endothelial cell development and function during human pregnancy that leads to higher risk of miscarriage, congenital heart disease and stillbirth.

Insights into the Inherited Basis of Valvular Heart Disease

PURPOSE OF REVIEW: Increases in the availability of genetic data and advances in the tools and methods for their analyses have enabled well-powered genetic association studies that have significantly enhanced our understanding of the genetic factors underlying both rare and common valve diseases. Valvular heart diseases, such as congenital valve malformations and degenerative valve lesions, increase the risk of heart failure, arrhythmias, and sudden death. In this review, we provide an updated overview of our current understanding of the genetic mechanisms underlying valvular heart diseases. With a focus on discoveries from the past 5 years, we describe recent insights into genetic risk and underlying biological pathways. RECENT FINDINGS: Recently acquired knowledge around valvular heart disease genetics has provided important insights into novel mechanisms related to disease pathogenesis. Newly identified risk loci associated valvular heart disease mainly regulate the composition of the extracellular matrix, accelerate the endothelial-to-mesenchymal transition, contribute to cilia formation processes, and play roles in lipid metabolism. Large-scale genomic analyses have identified numerous risk loci, genes, and biological pathways associated with degenerative valve disease and congenital valve malformations. Shared risk genes suggest common mechanistic pathways for various valve pathologies. More recent studies have combined cardiac magnetic resonance imaging and machine learning to offer a novel approach for exploring genotype-phenotype relationships regarding valve disease. Progress in the field holds promise for targeted prevention, particularly through the application of polygenic risk scores, and innovative therapies based on the biological mechanisms for predominant forms of valvular heart diseases.

Rare Genomic Copy Number Variants Implicate New Candidate Genes for Bicuspid Aortic Valve

Bicuspid aortic valve (BAV), the most common congenital heart defect, is a major cause of aortic valve disease requiring valve interventions and thoracic aortic aneurysms predisposing to acute aortic dissections. The spectrum of BAV ranges from early onset valve and aortic complications (EBAV) to sporadic late onset disease. Rare genomic copy number variants (CNVs) have previously been implicated in the development of BAV and thoracic aortic aneurysms. We determined the frequency and gene content of rare CNVs in EBAV probands (n = 272) using genome-wide SNP microarray analysis and three complementary CNV detection algorithms (cnvPartition, PennCNV, and QuantiSNP). Unselected control genotypes from the Database of Genotypes and Phenotypes were analyzed using identical methods. We filtered the data to select large genic CNVs that were detected by multiple algorithms. Findings were replicated in cohorts with late onset sporadic disease (n = 5040). We identified 34 large and rare (< 1:1000 in controls) CNVs in EBAV probands. The burden of CNVs intersecting with genes known to cause BAV when mutated was increased in case-control analysis. CNVs intersecting with GATA4 and DSCAM were enriched in cases, recurrent in other datasets, and segregated with disease in families. In total, we identified potentially pathogenic CNVs in 8% of EBAV cases, implicating alterations of candidate genes at these loci in the pathogenesis of BAV.

Repurposing Normal Chromosomal Microarray Data to Harbor Genetic Insights into Congenital Heart Disease

About 15% of congenital heart disease (CHD) patients have a known pathogenic copy number variant. The majority of their chromosomal microarray (CMA) tests are deemed normal. Diagnostic interpretation typically ignores microdeletions smaller than 100 kb. We hypothesized that unreported microdeletions are enriched for CHD genes. We analyzed "normal" CMAs of 1762 patients who were evaluated at a pediatric referral center, of which 319 (18%) had CHD. Using CMAs from monozygotic twins or replicates from the same individual, we established a size threshold based on probe count for the reproducible detection of small microdeletions. Genes in the microdeletions were sequentially filtered by their nominal association with a CHD diagnosis, the expression level in the fetal heart, and the deleteriousness of a loss-of-function mutation. The subsequent enrichment for CHD genes was assessed using the presence of known or potentially novel genes implicated by a large whole-exome sequencing study of CHD. The unreported microdeletions were modestly enriched for both known CHD genes and those of unknown significance identified using their de novo mutation in CHD patients. Our results show that readily available "normal" CMA data can be a fruitful resource for genetic discovery and that smaller deletions should receive more attention in clinical evaluation.

A Comprehensive Review of Management Strategies for Bicuspid Aortic Valve (BAV): Exploring Epidemiology, Aetiology, Aortopathy, and Interventions in Light of Recent Guidelines

OBJECTIVE

bicuspid aortic valve (BAV) stands as the most prevalent congenital heart condition intricately linked to aortic pathologies encompassing aortic regurgitation (AR), aortic stenosis, aortic root dilation, and aortic dissection. The aetiology of BAV is notably intricate, involving a spectrum of genes and polymorphisms. Moreover, BAV lays the groundwork for an array of structural heart and aortic disorders, presenting varying degrees of severity. Establishing a tailored clinical approach amid this diverse range of BAV-related conditions is of utmost significance. In this comprehensive review, we delve into the epidemiology, aetiology, associated ailments, and clinical management of BAV, encompassing imaging to aortic surgery. Our exploration is guided by the perspectives of the aortic team, spanning six distinct guidelines.

METHODS

We conducted an exhaustive search across databases like PubMed, Ovid, Scopus, and Embase to extract relevant studies. Our review incorporates 84 references and integrates insights from six different guidelines to create a comprehensive clinical management section.

RESULTS

BAV presents complexities in its aetiology, with specific polymorphisms and gene disorders observed in groups with elevated BAV prevalence, contributing to increased susceptibility to other cardiovascular conditions. The altered hemodynamics inherent to BAV instigate adverse remodelling of the aorta and heart, thus fostering the development of epigenetically linked aortic and heart diseases. Employing TTE screening for first-degree relatives of BAV patients might be beneficial for disease tracking and enhancing clinical outcomes. While SAVR is the primary recommendation for indicated AVR in BAV, TAVR might be an option for certain patients endorsed by adept aortic teams. In addition, proficient teams can perform aortic valve repair for AR cases. Aortic surgery necessitates personalized evaluation, accounting for genetic makeup and risk factors. While the standard aortic replacement threshold stands at 55 mm, it may be tailored to 50 mm or even 45 mm based on patient-specific considerations.

CONCLUSION

This review reiterates the significance of considering the multifactorial nature of BAV as well as the need for further research to be carried out in the field.

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.

Bicuspid Aortic Valve-Associated Regulatory Regions Reveal GATA4 Regulation and Function During Human-Induced Pluripotent Stem Cell-Based Endothelial-Mesenchymal Transition-Brief Report

BACKGROUND

The endothelial-mesenchymal transition (EndoMT) is a fundamental process for heart valve formation and defects in EndoMT cause aortic valve abnormalities. Our previous genome-wide association study identified multiple variants in a large chromosome 8 segment as significantly associated with bicuspid aortic valve (BAV). The objective of this study is to determine the biological effects of this large noncoding segment in human induced pluripotent stem cell (hiPSC)-based EndoMT.

METHODS

A large genomic segment enriched for BAV-associated variants was deleted in hiPSCs using 2-step CRISPR/Cas9 editing. To address the effects of the variants on GATA4 expression, we generated CRISPR repression hiPSC lines (CRISPRi) as well as hiPSCs from BAV patients. The resulting hiPSCs were differentiated to mesenchymal/myofibroblast-like cells through cardiovascular-lineage endothelial cells for molecular and cellular analysis. Single-cell RNA sequencing was also performed at different stages of EndoMT induction.

RESULTS

The large deletion impaired hiPSC-based EndoMT in multiple biallelic clones compared with their isogenic control. It also reduced GATA4 transcript and protein levels during EndoMT, sparing the other genes nearby the deletion segment. Single-cell trajectory analysis revealed the molecular reprogramming during EndoMT. Putative GATA-binding protein targets during EndoMT were uncovered, including genes implicated in endocardial cushion formation and EndoMT process. Differentiation of cells derived from BAV patients carrying the rs117430032 variant as well as CRISPRi repression of the rs117430032 locus resulted in lower GATA4 expression in a stage-specific manner. TWIST1 was identified as a potential regulator of GATA4 expression, showing specificity to the locus tagged by rs117430032.

CONCLUSIONS

BAV-associated distal regions regulate GATA4 expression during hiPSC-based EndoMT, which in turn promotes EndoMT progression, implicating its contribution to heart valve development.

Considering the Genetic Architecture of Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is among the most severe cardiovascular malformations and understanding its causes is crucial to making progress in prevention and treatment. Genetic analysis is a broadly useful tool for dissecting complex causal mechanisms and it is playing a significant role in HLHS research. However, unlike classical Mendelian disorders where a relatively small number of genes are largely determinative of the occurrence and severity of the disease, the picture in HLHS is complex. De novo single-gene and copy number variant (CNV) disorders make an important contribution, but there is emerging evidence for causal contributions from lower penetrance and common variation. Integrating this emerging knowledge into clinical diagnostics and translating the findings into effective prevention and treatment remain challenges for the future.

Whole Genome Sequencing in Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a genetically complex disorder. Whole genome sequencing enables comprehensive scrutiny of single nucleotide variants and small insertions/deletions, within both coding and regulatory regions of the genome, revolutionizing susceptibility-gene discovery research. Because millions of rare variants comprise an individual genome, identification of alleles linked to HLHS necessitates filtering algorithms based on various parameters, such as inheritance, enrichment, omics data, known genotype–phenotype associations, and predictive or experimental modeling. In this brief review, we highlight family and cohort-based strategies used to analyze whole genome sequencing datasets and identify HLHS candidate genes. Key findings include compound and digenic heterozygosity among several prioritized genes and genetic associations between HLHS and bicuspid aortic valve or cardiomyopathy. Together with findings of independent genomic investigations, MYH6 has emerged as a compelling disease gene for HLHS and other left-sided congenital heart diseases.