Ebstein's anomaly may be caused by mutations in the sarcomere protein gene MYH7

MYH7 in cardiomyopathy and skeletal muscle myopathy

Myosin heavy chain gene 7 (MYH7), a sarcomeric gene encoding the myosin heavy chain (myosin-7), has attracted considerable interest as a result of its fundamental functions in cardiac and skeletal muscle contraction and numerous nucleotide variations of MYH7 are closely related to cardiomyopathy and skeletal muscle myopathy. These disorders display significantly inter- and intra-familial variability, sometimes developing complex phenotypes, including both cardiomyopathy and skeletal myopathy. Here, we review the current understanding on MYH7 with the aim to better clarify how mutations in MYH7 affect the structure and physiologic function of sarcomere, thus resulting in cardiomyopathy and skeletal muscle myopathy. Importantly, the latest advances on diagnosis, research models in vivo and in vitro and therapy for precise clinical application have made great progress and have epoch-making significance. All the great advance is discussed here.

Sin3a associated protein 130 kDa, sap130, plays an evolutionary conserved role in zebrafish heart development

Hypoplastic left heart syndrome (HLHS) is a congenital heart disease where the left ventricle is reduced in size. A forward genetic screen in mice identified SIN3A associated protein 130 kDa (Sap130), part of the chromatin modifying SIN3A/HDAC complex, as a gene contributing to the etiology of HLHS. Here, we report the role of zebrafish sap130 genes in heart development. Loss of sap130a, one of two Sap130 orthologs, resulted in smaller ventricle size, a phenotype reminiscent to the hypoplastic left ventricle in mice. While cardiac progenitors were normal during somitogenesis, diminution of the ventricle size suggest the Second Heart Field (SHF) was the source of the defect. To explore the role of sap130a in gene regulation, transcriptome profiling was performed after the heart tube formation to identify candidate pathways and genes responsible for the small ventricle phenotype. Genes involved in cardiac differentiation and cardiac function were dysregulated in sap130a, but not in sap130b mutants. Confocal light sheet analysis measured deficits in cardiac output in MZsap130a supporting the notion that cardiomyocyte maturation was disrupted. Lineage tracing experiments revealed a significant reduction of SHF cells in the ventricle that resulted in increased outflow tract size. These data suggest that sap130a is involved in cardiogenesis via regulating the accretion of SHF cells to the growing ventricle and in their subsequent maturation for cardiac function. Further, genetic studies revealed an interaction between hdac1 and sap130a, in the incidence of small ventricles. These studies highlight the conserved role of Sap130a and Hdac1 in zebrafish cardiogenesis.

Sin3a Associated Protein 130kDa, sap130, plays an evolutionary conserved role in zebrafish heart development

Hypoplastic left heart syndrome (HLHS) is a congenital heart disease where the left ventricle is reduced in size. A forward genetic screen in mice identified SIN3A associated protein 130kDa ( Sap130 ), a protein in the chromatin modifying SIN3A/HDAC1 complex, as a gene contributing to the digenic etiology of HLHS. Here, we report the role of zebrafish sap130 genes in heart development. Loss of sap130a, one of two Sap130 orthologs, resulted in smaller ventricle size, a phenotype reminiscent to the hypoplastic left ventricle in mice. While cardiac progenitors were normal during somitogenesis, diminution of the ventricle size suggest the Second Heart Field (SHF) was the source of the defect. To explore the role of sap130a in gene regulation, transcriptome profiling was performed after the heart tube formation to identify candidate pathways and genes responsible for the small ventricle phenotype. Genes involved in cardiac differentiation and cell communication were dysregulated in sap130a , but not in sap130b mutants. Confocal light sheet analysis measured deficits in cardiac output in MZsap130a supporting the notion that cardiomyocyte maturation was disrupted. Lineage tracing experiments revealed a significant reduction of SHF cells in the ventricle that resulted in increased outflow tract size. These data suggest that sap130a is involved in cardiogenesis via regulating the accretion of SHF cells to the growing ventricle and in their subsequent maturation for cardiac function. Further, genetic studies revealed an interaction between hdac1 and sap130a , in the incidence of small ventricles. These studies highlight the conserved role of Sap130a and Hdac1 in zebrafish cardiogenesis.

Neurological, Extracardiac, and Cardiac Manifestations of Ebstein's Anomaly Along With its Genetics, Diagnostic Techniques, Treatment Updates, and the Future Ahead

Ebstein's anomaly is a congenital heart defect characterized by the displacement of the tricuspid valve, and its leaflets to be malformed. Due to the defect involving the tricuspid valve, there is a reverse flow of blood into the right-sided atrium, which may lead to cardiac hypertrophy and edema of the lower extremities. There is a decreased flow of blood out of the right heart due to reduced right ventricular contractility and tricuspid regurgitation. Children afflicted with this anomaly usually suffer from atrial septal defect and this is usually diagnosed before birth on a routine ultrasound scan. In neonates, cyanosis can be seen due to right-to-left atrial shunting or as a result of severe congestive heart failure. If the infant has pulmonary hypertension, cyanosis is markedly increased as there will be a limitation in pulmonary blood flow. In adults, arrhythmias, cyanosis, and heart failure are seen. The bundle of Kent leads to the formation of an electrical conduction abnormality between the right ventricle and atrium. This leads to a condition commonly known as Wolff- Parkinson-White syndrome in patients. An enlarged spherical heart is usually present on a chest X-ray. ECG changes of Ebstein's anomaly show taller than usual P waves, PR prolongation, and right bundle branch block. There can be certain neurological and extracardiac manifestations too such as hemiplegia, stroke, dysarthria, etc. During fetal life, specifically at 16 and 20 weeks of gestation, the anomaly can be diagnosed via echocardiography. Prostaglandin infusion (PGE1) is given to maintain pulmonary circulation in neonates if cyanosis is seen. In children and adults with congestive cardiac failure due to this anomaly, medical management includes digoxin, beta-blockers, diuretics, and angiotensin converting enzyme (ACE) inhibitors to improve heart failure. Surgical treatment includes valve reconstruction. In this article, we review the pathophysiology, genetics, diagnosis, management, and prognosis of Ebstein's Anomaly along with a comprehensive discussion on its genetics, neurological manifestations, extracardiac features, and current advancements in treatment.

Ebstein's Anomaly: From Fetus to Adult-Literature Review and Pathway for Patient Care

Ebstein's anomaly, first described in 1866 by Dr William Ebstein, accounts for 0.3-0.5% of congenital heart defects and represents 40% of congenital tricuspid valve abnormalities. Ebstein's anomaly affects the development of the tricuspid valve with widely varying morphology and, therefore, clinical presentation. Associated congenital cardiac lesions tend to be found more often in younger patients and may even be the reason for presentation. Presentation can vary from the most extreme form in fetal life, to asymptomatic diagnosis late in adult life. The most symptomatic patients need intensive care support in the neonatal period. This article summarizes and analyzes the literature on Ebstein's anomaly and provides a framework for the investigation, management, and follow-up of these patients, whether they present via fetal detection or late in adult life. For each age group, the clinical presentation, required diagnostic investigations, natural history, and management are described. The surgical options available for patients with Ebstein's anomaly are detailed and analyzed, starting from the initial mono-leaflet repairs to the most recent cone repair and its modifications. The review also assesses the effects of pregnancy on the Ebstein's circulation, and vice versa, the effects of Ebstein's on pregnancy outcomes. Finally, two attached appendices are provided for a structured echocardiogram protocol and key information useful for comprehensive Multi-Disciplinary Team discussion.

A Systematic Review of Ebstein’s Anomaly with Left Ventricular Noncompaction

Traditional definitions of Ebstein’s anomaly (EA) and left ventricular noncompaction (LVNC), two rare congenital heart defects (CHDs), confine disease to either the right or left heart, respectively. Around 15–29% of patients with EA, which has a prevalence of 1 in 20,000 live births, commonly manifest with LVNC. While individual EA or LVNC literature is extensive, relatively little discussion is devoted to the joint appearance of EA and LVNC (EA/LVNC), which poses a higher risk of poor clinical outcomes. We queried PubMed, Medline, and Web of Science for all peer-reviewed publications from inception to February 2022 that discuss EA/LVNC and found 58 unique articles written in English. Here, we summarize and extrapolate commonalities in clinical and genetic understanding of EA/LVNC to date. We additionally postulate involvement of shared developmental pathways that may lead to this combined disease. Anatomical variation in EA/LVNC encompasses characteristics of both CHDs, including tricuspid valve displacement, right heart dilatation, and left ventricular trabeculation, and dictates clinical presentation in both age and severity. Disease treatment is non-specific, ranging from symptomatic management to invasive surgery. Apart from a few variant associations, mainly in sarcomeric genes MYH7 and TPM1, the genetic etiology and pathogenesis of EA/LVNC remain largely unknown.

Case Report of a 33-year-old with Ebstein malformation of tricuspid valve and hypertrophic cardiomyopathy

Ebstein malformation of tricuspid valve is a congenital disease of tricuspid valve with associated right ventricular cardiomyopathy. Hypertrophic cardiomyopathy is a form of inherited left ventricular cardiomyopathy caused by sarcomeric protein gene mutations with inherent risks of sudden cardiac death. Here we report a rare case with co-occurrence of Ebstein malformation of tricuspid valve and hypertrophic cardiomyopathy in a young patient.

Diverse cardiac phenotypes among different carriers of the same MYH7 splicing variant allele (c.732+1G>A) from a family

Background

Left ventricular non-compaction cardiomyopathy (LVNC) is a rare congenital heart defect. Gene defections have been found in patients with LVNC and their family members; and MYH7 is the most frequent gene associated with LVNC.

Methods

We performed a complete prenatal ultrasound and echocardiographic examination on a fetus with cardiac abnormality and a parent–child trio whole-exome sequencing to identify the potential genetic causes. When the genetic abnormality in MYH7 was identified in the fetus, we performed echocardiography and genetic screening on its high-risk relatives.

Results

Second trimester ultrasound and echocardiography showed several malformations in the fetus: Ebstein’s anomaly (EA), heart dilatation, perimembranous ventricle septal defects, mild seroperitoneum, and single umbilical artery. Heterozygous genotyping of a splicing variant allele (NM_00025.3: c.732+G>A) was identified in this fetus and her mother, not her father, indicating a maternal inheritance. Subsequently, direct sequencing confirmed the presence of this splicing variant among her grandmother (mother of mother), mother, older sister, and herself in a heterozygous manner. No PCR products were amplified by qRT-PCR for the RNA samples extracted from peripheral blood cells. In addition to this proband who was diagnosed with EA, her older sister and grandmother (mother of mother) were diagnosed with isolated asymptomatic LVCN, but her mother was just a carrier with no marked clinical manifestations after family screening.

Conclusion

The presence of MYH7 splicing variant c.732+G>A can be inherited maternally, and its cardiac phenotypes are different from one carrier to another.

Ebstein Anomaly and Right Aortic Arch in Patient with Charge Syndrome

Ebstein anomaly is a rare congenital heart disease characterized by a varying degree of anatomical and functional abnormalities of tricuspid valve and right ventricle. It often coexists with other congenital cardiac malformations. Up to 79–89% of patients with Ebstein anomaly have interatrial communication in the form of patent oval foramen or atrial septal defect and more than one-third has other types of cardiac malformations. Association between Ebstein anomaly and right aortic arch is extremely rare and only few cases have been described in the literature so far. Much rarer than with other cardiac malformations, Ebstein anomaly is associated with non-cardiac malformations or genetic syndromes. Several cases of association between Ebstein anomaly and Charge syndrome have been reported, nevertheless, Ebstein anomaly accounts for less than 1% of cardiac defects seen in patients with Charge syndrome. In this case report, we present a unique case of a patient with Charge syndrome where both Ebstein anomaly and right aortic arch are present. The diagnosis of Ebstein anomaly and right aortic arch was established prenatally. In the first years of life, the patient did not exhibit any remarkable symptoms. However, over time, deterioration of right ventricle function and increased tricuspid regurgitation were observed, requiring consideration of surgical treatment at the age of five. In addition, delay in physical, motor, and mental development was observed and thus, at the age of five, the patient was consulted by a medical geneticist and a gene panel to test for structural heart defects was ordered. The test showed a mutation in chromodomain helicase DNA binding protein 7 (CHD7) gene, which, along with clinical features, allowed to establish a diagnosis of Charge syndrome. To the best of the authors’ knowledge, this is the first case report of a patient with Charge syndrome, Ebstein anomaly, and right aortic arch that has been described in the literature.

Ebstein Anomaly in the Adult Patient

Ebstein anomaly is a congenital malformation involving primarily the tricuspid valve, with failure of delamination from the underlying myocardium and right ventricular myopathy. Echocardiography is diagnostic in most patients and demonstrates apical displacement of the septal leaflet and variable tethering of leaflet tissue to the right ventricular myocardium. Operative intervention is considered for exertional symptoms, progressive right ventricular enlargement, or right ventricular dysfunction. Tricuspid valve cone repair is the preferred surgical approach. Tricuspid valve replacement and bidirectional cavopulmonary shunt also are considered in patients with advanced disease. Pregnancy generally is well tolerated. Patients with Ebstein anomaly require lifelong follow-up.

Congenital heart defects and left ventricular non-compaction in males with loss-of-function variants in NONO

BACKGROUND

The non-POU domain containing octamer-binding gene (NONO) is located on chromosome Xq13.1 and encodes a member of a small family of RNA-binding and DNA-binding proteins that perform a variety of tasks involved in RNA synthesis, transcriptional regulation and DNA repair. Loss-of-function variants in NONO have been described as a cause of intellectual disability in males but have not been described in association with congenital heart defects or cardiomyopathy. In this article, we seek to further define the phenotypic consequences of NONO depletion in human subjects.

METHODS

We searched a clinical database of over 6000 individuals referred for exome sequencing and over 60 000 individuals referred for CNV analysis.

RESULTS

We identified two males with atrial and ventricular septal defects, left ventricular non-compaction (LVNC), developmental delay and intellectual disability, who harboured de novo, loss-of-function variants in NONO. We also identified a male infant with developmental delay, congenital brain anomalies and severe LVNC requiring cardiac transplantation, who inherited a single-gene deletion of NONO from his asymptomatic mother.

CONCLUSIONS

We conclude that in addition to global developmental delay and intellectual disability, males with loss-of-function variants in NONO may also be predisposed to developing congenital heart defects and LVNC with the penetrance of these cardiac-related problems being influenced by genetic, epigenetic, environmental or stochastic factors. Brain imaging of males with NONO deficiency may reveal structural defects with abnormalities of the corpus callosum being the most common. Although dysmorphic features vary between affected individuals, relative macrocephaly is a common feature.

Ebstein anomaly: a review

Cardiac congenital abnormalities are a leading cause in neonatal mortality occurring in up to 1 in 200 of live births. Ebstein anomaly, also known as Kassamali anomaly, accounts for 1 percent of all congenital cardiac anomalies. This congenital abnormality involves malformation of the tricuspid valve and of the right ventricle. In this review, the causes of the anomaly are outlined and the pathophysiology is discussed, with a focus on the symptoms, management, and treatments available to date.

A Biobank for Long-term and Sustainable Research in the Field of Congenital Heart Disease in Germany

Congenital heart disease (CHD) is the most frequent birth defect (0.8%-1% of all live births). Due to the advance in prenatal and postnatal early diagnosis and treatment, more than 90% of these patients survive into adulthood today. However, several mid- and long-term morbidities are dominating the follow-up of these patients. Due to the rarity and heterogeneity of the phenotypes of CHD, multicenter registry-based studies are required. The CHD-Biobank was established in 2009 with the aim to collect DNA from patients and their parents (trios) or from affected families, as well as cardiovascular tissues from patients undergoing corrective heart surgery for cardiovascular malformations. Clinical/phenotype data are matched to the International Paediatric and Congenital Cardiac Code (IPCCC) and the International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10). The DNA collection currently comprises samples from approximately 4200 participants with a wide range of CHD phenotypes. The collection covers about 430 trios and 120 families with more than one affected member. The cardiac tissue collection comprises 1143 tissue samples from 556 patients after open heart surgery. The CHD-Biobank provides a comprehensive basis for research in the field of CHD with high standards of data privacy, IT management, and sample logistics.

Structural implications of β-cardiac myosin heavy chain mutations in human disease

Over 500 disease-causing point mutations have been found in the human β-cardiac myosin heavy chain, many quite recently with modern sequencing techniques. This review shows that clusters of these mutations occur at critical points in the sequence and investigates whether the many studies on these mutants reveal information about the function of this protein.

Familial ebstein anomaly, left ventricular hypertrabeculation, and ventricular septal defect associated with a MYH7 mutation

Ebstein anomaly is a rare congenital heart defect that most often occurs sporadically within a kindred. Familial cases, although reported, are uncommon. At this time, the genetic etiology of Ebstein anomaly is not fully elucidated. Here, we describe clinical and molecular investigations of a rare case of familial Ebstein anomaly in association with a likely pathogenic mutation of the MYH7 gene. The severity of presentation varies, and Ebstein anomaly can be observed in association with such other heart defects as ventricular septal defect and left ventricular (LV) hypertrabeculation, as seen in our family of study. In our family of study, the 31-year-old father and four of his children have been diagnosed with Ebstein anomaly. Genetic testing revealed that the father was heterozygous for the Glu1220del variant detected in exon 27 of the MYH7 gene. The MYH7 gene encodes the β-myosin heavy chain and is expressed in cardiac muscle. DNA sequencing of three of his affected children confirmed that they carried the same variant while the fourth affected child was not available for testing. This is the first report of familial Ebstein anomaly associated with the Glu1220del mutation of the MYH7 gene. The mutation segregates with disease in a family with autosomal dominant transmission of congenital heart defects including Ebstein anomaly and other associated cardiovascular defects including LV hypertrabeculation and ventricular septal defect.

Ebstein anomaly associated with left ventricular noncompaction: an autosomal dominant condition that can be caused by mutations in MYH7

Left ventricular noncompaction (LVNC) is a relatively common genetic cardiomyopathy, characterized by prominent trabeculations with deep intertrabecular recesses in mainly the left ventricle. Although LVNC often occurs in an isolated entity, it may also be present in various types of congenital heart disease (CHD). The most prevalent CHD in LVNC is Ebstein anomaly, which is a rare form of CHD characterized by apical displacement and partial fusion of the septal and posterior leaflet of the tricuspid valve with the ventricular septum. Several reports of sporadic as well as familial cases of Ebstein anomaly associated with LVNC have been reported. Recent studies identified mutations in the MYH7 gene, encoding the sarcomeric β-myosin heavy chain protein, in patients harboring this specific phenotype. Here, we will review the association between Ebstein anomaly, LVNC and mutations in MYH7, which seems to represent a subtype of Ebstein anomaly with autosomal dominant inheritance and variable penetrance.

A patient of Ebstein's anomaly associated with biventricular noncompaction presented with Wolf Parkinson White syndrome - A rare presentation

A 34 year-old male patient presented with recurrent attack of palpitation and chest pain due to Wolf Parkinson White syndrome (WPWS). Two dimensional echocardiography demonstrated features of Ebstein's anomaly along with biventricular non compaction. Color flow Doppler studies confirmed the presence of blood flow within the trabeculations. Biventricular myocardial non-compaction associated with Ebstein's anomaly who presented with WPWS is a very rare association. So far, Medline search revealed only three reported cases in the literatures. The patient was treated with radiofrequency ablation of right sided posteroseptal accessory pathway of WPWS and was asymptomatic in further follow-up.

Human gene copy number spectra analysis in congenital heart malformations

The clinical significance of copy number variants (CNVs) in congenital heart disease (CHD) continues to be a challenge. Although CNVs including genes can confer disease risk, relationships between gene dosage and phenotype are still being defined. Our goal was to perform a quantitative analysis of CNVs involving 100 well-defined CHD risk genes identified through previously published human association studies in subjects with anatomically defined cardiac malformations. A novel analytical approach permitting CNV gene frequency "spectra" to be computed over prespecified regions to determine phenotype-gene dosage relationships was employed. CNVs in subjects with CHD (n = 945), subphenotyped into 40 groups and verified in accordance with the European Paediatric Cardiac Code, were compared with two control groups, a disease-free cohort (n = 2,026) and a population with coronary artery disease (n = 880). Gains (≥200 kb) and losses (≥100 kb) were determined over 100 CHD risk genes and compared using a Barnard exact test. Six subphenotypes showed significant enrichment (P ≤ 0.05), including aortic stenosis (valvar), atrioventricular canal (partial), atrioventricular septal defect with tetralogy of Fallot, subaortic stenosis, tetralogy of Fallot, and truncus arteriosus. Furthermore, CNV gene frequency spectra were enriched (P ≤ 0.05) for losses at: FKBP6, ELN, GTF2IRD1, GATA4, CRKL, TBX1, ATRX, GPC3, BCOR, ZIC3, FLNA and MID1; and gains at: PRKAB2, FMO5, CHD1L, BCL9, ACP6, GJA5, HRAS, GATA6 and RUNX1. Of CHD subjects, 14% had causal chromosomal abnormalities, and 4.3% had likely causal (significantly enriched), large, rare CNVs. CNV frequency spectra combined with precision phenotyping may lead to increased molecular understanding of etiologic pathways.