Rare loss-of-function variants in matrisome genes are enriched in Ebstein's anomaly

Ebstein's anomaly, a rare congenital heart disease, is distinguished by the failure of embryological delamination of the tricuspid valve leaflets from the underlying primitive right ventricle myocardium. Gaining insight into the genetic basis of Ebstein's anomaly allows a more precise definition of its pathogenesis. In this study, two distinct cohorts from the Chinese Han population were included: a case-control cohort consisting of 82 unrelated cases and 125 controls without cardiac phenotypes and a trio cohort comprising 36 parent-offspring trios. Whole-exome sequencing data from all 315 participants were utilized to identify qualifying variants, encompassing rare (minor allele frequency < 0.1% from East Asians in the gnomAD database) functional variants and high-confidence (HC) loss-of-function (LoF) variants. Various statistical models, including burden tests and variance-component models, were employed to identify rare variants, genes, and biological pathways associated with Ebstein's anomaly. Significant associations were noted between Ebstein's anomaly and rare HC LoF variants found in genes related to the matrisome, a collection of extracellular matrix (ECM) components. Specifically, 47 genes with HC LoF variants were exclusively or predominantly identified in cases, while nine genes showed such variants in the probands. Over half of unrelated cases (n = 42) and approximately one-third of probands (n = 12) were found to carry one or two LoF variants in these prioritized genes. These results highlight the role of the matrisome in the pathogenesis of Ebstein's anomaly, contributing to a better understanding of the genetic architecture underlying this condition. Our findings hold the potential to impact the genetic diagnosis and treatment approaches for Ebstein's anomaly.

Heterozygous nonsense variants in laminin subunit 3α resulting in Ebstein's anomaly

Ebstein's anomaly is a rare congenital heart disease characterized by tricuspid valve downward displacement and is associated with additional cardiac phenotypes such as left ventricle non-compaction. The genetic basis of Ebstein's anomaly has yet to be fully elucidated, although several genes (e.g., NKX2-5, MYH7, TPM1, and FLNA) may contribute to Ebstein's anomaly. Here, in two Ebstein's anomaly families (a three-generation family and a trio), we identified independent heterozygous nonsense variants in laminin subunit 3 α (LAMA3), cosegregated with phenotypes in families with reduced penetrance. Furthermore, knocking out Lama3 in mice revealed that haploinsufficiency of Lama3 led to Ebstein's malformation of the tricuspid valve and an abnormal basement membrane structure. In conclusion, we identified a novel gene-disease association of LAMA3 implicated in Ebstein's anomaly, and the findings extended our understanding of the role of the extracellular matrix in Ebstein's anomaly etiology.

Integrated microRNA and mRNA Expression Profiling Identifies Novel Targets and Networks Associated with Ebstein's Anomaly

Little is known about abundance level changes of circulating microRNAs (miRNAs) and messenger RNAs (mRNA) in patients with Ebstein’s anomaly (EA). Here, we performed an integrated analysis to identify the differentially abundant miRNAs and mRNA targets and to identify the potential therapeutic targets that might be involved in the mechanisms underlying EA. A large panel of human miRNA and mRNA microarrays were conducted to determine the genome-wide expression profiles in the blood of 16 EA patients and 16 age and gender-matched healthy control volunteers (HVs). Differential abundance level of single miRNA and mRNA was validated by Real-Time quantitative PCR (RT-qPCR). Enrichment analyses of altered miRNA and mRNA abundance levels were identified using bioinformatics tools. Altered miRNA and mRNA abundance levels were observed between EA patients and HVs. Among the deregulated miRNAs and mRNAs, 76 miRNAs (49 lower abundance and 27 higher abundance, fold-change of ≥2) and 29 mRNAs (25 higher abundance and 4 lower abundance, fold-change of ≥1.5) were identified in EA patients compared to HVs. Bioinformatics analysis identified 37 pairs of putative miRNA-mRNA interactions. The majority of the correlations were detected between the lower abundance level of miRNA and higher abundance level of mRNA, except for let-7b-5p, which showed a higher abundance level and their target gene, SCRN3, showed a lower abundance level. Pathway enrichment analysis of the deregulated mRNAs identified 35 significant pathways that are mostly involved in signal transduction and cellular interaction pathways. Our findings provide new insights into a potential molecular biomarker(s) for the EA that may guide the development of novel targeting therapies.

Novel KLHL26 variant associated with a familial case of Ebstein's anomaly and left ventricular noncompaction

BACKGROUND

Ebstein's anomaly (EA) is a rare congenital heart disease of the tricuspid valve and right ventricle. Patients with EA often manifest with left ventricular noncompaction (LVNC), a cardiomyopathy. Despite implication of cardiac sarcomere genes in some cases, very little is understood regarding the genetic etiology of EA/LVNC. Our study describes a multigenerational family with at least 10 of 17 members affected by EA/LVNC.

METHODS

We performed echocardiography on all family members and conducted exome sequencing of six individuals. After identifying candidate variants using two different bioinformatic strategies, we confirmed segregation with phenotype using Sanger sequencing. We investigated structural implications of candidate variants using protein prediction models.

RESULTS

Exome sequencing analysis of four affected and two unaffected members identified a novel, rare, and damaging coding variant in the Kelch-like family member 26 (KLHL26) gene located on chromosome 19 at position 237 of the protein (GRCh37). This variant region was confirmed by Sanger sequencing in the remaining family members. KLHL26 (c.709C > T p.R237C) segregates only with EA/LVNC-affected individuals (FBAT p < .05). Investigating structural implications of the candidate variant using protein prediction models suggested that the KLHL26 variant disrupts electrostatic interactions when binding to part of the ubiquitin proteasome, specifically Cullin3 (CUL3), a component of E3 ubiquitin ligase.

CONCLUSION

In this familial case of EA/LVNC, we have identified a candidate gene variant, KLHL26 (p.R237C), which may have an important role in ubiquitin-mediated protein degradation during cardiac development.

Left ventricular non-compaction with Ebstein anomaly attributed to a TPM1 mutation

Left ventricular non-compaction (cardiomyopathy) (LVN(C)) is a rare hereditary cardiac condition, resulting from abnormal embryonic myocardial development. While it mostly occurs as an isolated condition, association with other cardiovascular manifestations such as Ebstein anomaly (EA) has been reported. This congenital heart defect is characterized by downward displacement of the tricuspid valve and leads to diminished ventricular size and function. In an autosomal dominant LVN(C) family consisting of five affected individuals, of which two also presented with EA and three with mitral valve insufficiency, we pursued the genetic disease cause using whole exome sequencing (WES). WES revealed a missense variant (p.Leu113Val) in TPM1 segregating with the LVN(C) phenotype. TPM1 encodes α-tropomyosin, which is involved in myocardial contraction, as well as in stabilization of non-muscle cytoskeletal actin filaments. So far, LVN(C)-EA has predominantly been linked to pathogenic variants in MYH7. However, one sporadic LVN(C)-EA case with a de novo TPM1 variant has recently been described. We here report the first LVN(C)-EA family segregating a pathogenic TPM1 variant, further establishing the association between EA predisposition and TPM1-related LVN(C). Consequently, we recommend genetic testing for both MYH7 and TPM1 in patients or families in which LVN(C)/non-compaction and EA coincide.

Genetic Variants in Isolated Ebstein Anomaly Implicated in Myocardial Development Pathways

Ebstein anomaly (EA) is a rare heart defect in which the tricuspid valve is malformed and displaced. The tricuspid valve abnormalities can lead to backflow of blood from the right ventricle to the right atrium, preventing proper circulation of blood to the lungs. Although the etiology of EA is largely unresolved, increased prevalence of EA in those with a family history of congenital heart disease suggests EA has a genetic component. Copy number variants (CNVs) are a major source of genetic variation and have been implicated in a range of congenital heart defect phenotypes. We performed a systematic, genome-wide search for CNVs in 47 isolated EA cases using genotyping microarrays. In addition, we used a custom HaloPlex panel to sequence three known EA genes and 47 candidate EA genes. We identified 35 candidate CNVs in 24 (51%) EA cases. Rare sequence variants in genes associated with cardiomyopathy were identified in 11 (23%) EA cases. Two CNVs near the transcriptional repressor HEY1, a member of the NOTCH signaling pathway, were identified in three unrelated cases. All other candidate CNVs were each identified in a single case. At least 11 of 35 candidate CNVs include genes involved in myocardial development or function, including multiple genes in the BMP signaling pathway. We identified enrichment of gene sets involved in histone modification and cardiomyocyte differentiation, supporting the involvement of the developing myocardium in the etiology of EA. Gene set enrichment analysis also identified ribosomal RNA processing, a potentially novel pathway of altered cardiac development in EA. Our results suggest an altered myocardial program may contribute to abnormal tricuspid valve development in EA. Future studies should investigate abnormal differentiation of cardiomyocytes as a potential etiological factor in EA.

Ebstein's anomaly

Ebstein's anomaly is a rare congenital heart disease, accounting for less than 1% of all congenital heart diseases, characterized by a wide clinical, electrocardiographic, echocardiographic, anatomic and prognostic polymorphism. The disease can be fatal since birth or may remain asymptomatic until adulthood, sometimes being associated with septal defects, transposition of great vessels, preexcitation syndromes, or left ventricular noncompaction. The genetic changes underlying this syndrome are not fully known, but in the cases associating left ventricular nonompaction a mutation in MYH7 gene encoding the beta-myosin heavy chain was recently detected. The authors present 2 cases of Ebstein's anomaly with different onset and course and discuss the current clinical, electrocardiographic and echocardiographic criteria used for prognostic stratification of Ebstein disease in relation to international literature.

Mutations in the sarcomere gene MYH7 in Ebstein anomaly

BACKGROUND

Ebstein anomaly is a rare congenital heart malformation characterized by adherence of the septal and posterior leaflets of the tricuspid valve to the underlying myocardium. An association between Ebstein anomaly with left ventricular noncompaction (LVNC) and mutations in MYH7 encoding β-myosin heavy chain has been shown; in this report, we have screened for MYH7 mutations in a cohort of probands with Ebstein anomaly in a large population-based study.

METHODS AND RESULTS

Mutational analysis in a cohort of 141 unrelated probands with Ebstein anomaly was performed by next-generation sequencing and direct DNA sequencing of MYH7. Heterozygous mutations were identified in 8 of 141 samples (6%). Seven distinct mutations were found; 5 were novel and 2 were known to cause hypertrophic cardiomyopathy. All mutations except for 1 3-bp deletion were missense mutations; 1 was a de novo change. Mutation-positive probands and family members showed various congenital heart malformations as well as LVNC. Among 8 mutation-positive probands, 6 had LVNC, whereas among 133 mutation-negative probands, none had LVNC. The frequency of MYH7 mutations was significantly different between probands with and without LVNC accompanying Ebstein anomaly (P<0.0001). LVNC segregated with the MYH7 mutation in the pedigrees of 3 of the probands, 1 of which also included another individual with Ebstein anomaly.

CONCLUSIONS

Ebstein anomaly is a congenital heart malformation that is associated with mutations in MYH7. MYH7 mutations are predominantly found in Ebstein anomaly associated with LVNC and may warrant genetic testing and family evaluation in this subset of patients.

D-transposition of the great arteries in a case of microduplication 22q11.2

The 22q11.2 deletion syndrome is one of the most frequent genetic syndromes, mainly characterized by cleft palate, facial dysmorphism, conotruncal heart malformations and immune deficiencies. Microduplication of the 22q11.2 region is a quite recently characterized genetic entity comprising a variable phenotype including some overlapping features with the 22q11.2 deletion syndrome. So far only few reports of patients with this microduplication and heart defects have been published. To our knowledge this is the first description of a patient with genetically confirmed duplication of the 22q11.2 region and d-transposition of the great arteries (d-TGA) as well as Ebstein's anomaly.

Familial biventricular myocardial noncompaction associated with Ebstein's malformation

BACKGROUND

Noncompaction of the ventricular myocardium is a rare congenital cardiomyopathy characterized by numerous excessively prominent trabeculations and deep intertrabecular recesses. Noncompaction of the ventricular myocardium is most often an isolated cardiac malformation presenting as a sporadic disease. Associated cardiac anomalies are present in some patients. We report a family with three adult males from consecutive generations having a biventricular form of noncompaction of the myocardium. Two of the patients have an associated Ebstein's malformation of the tricuspid valve.

METHODS

Clinical evaluation and follow-up, electrocardiography, echocardiography, heart catheterization, coronary angiography, contrast cineventriculography, and magnetic resonance imaging.

RESULTS AND CONCLUSIONS

The association of noncompaction of the ventricular myocardium and Ebstein's malformation has not been reported so far. We believe that both defects were caused by a developmental arrest of the right ventricular myocardium. Echocardiography is the diagnostic modality of choice in patients and in the male relatives, irrespective of their clinical status. Thromboembolic events, cardiac rhythm disorders and heart failure mandate treatment. Anticoagulation treatment and implantation of cardioverter-defibrillator pacemaker have to be strongly considered in these patients.

Ebstein anomaly and duplication of the distal arm of chromosome 15: Report of two patients

Ebstein anomaly of the tricuspid valve is an uncommon congenital heart defect. We report two unrelated patients with Ebstein anomaly and duplication of the distal long arm of chromosome 15 (15q22 --> qter and 15q24 --> qter). Duplication of 15q is a well-described phenotype that includes congenital heart defects, and these are the first cases with Ebstein anomaly. Duplication of 15q likely affects the early morphogenesis of cardiac structures, including the normal formation of the tricuspid valve.

Canine tricuspid valve malformation, a model of human Ebstein anomaly, maps to dog chromosome 9

BACKGROUND

Ebstein anomaly of the tricuspid valve is a congenital cardiac malformation characterised by downward displacement of the attachment of the septal and posterior leaflets of the tricuspid valve. Canine tricuspid valve malformation (CTVM) is morphologically similar to Ebstein anomaly; familial occurrence of CTVM has been described. Several observations suggest a genetic cause but most cases appear to be sporadic.

METHODS

Three purebred Labrador Retriever kindreds enriched for CTVM underwent clinical examination and echocardiography. DNA was extracted from whole blood. Genotyping was carried out using polymorphic repeat markers with an average spacing of 15 cM and polymorphic information content of 0.74.

RESULTS

Pedigree analysis identified CTVM segregating as an autosomal dominant trait with reduced penetrance. Genome wide linkage analysis in one kindred identified a CTVM susceptibility locus on dog chromosome 9 (CFA9) with a maximum multipoint lod score of 3.33. The two additional kindreds showed a conserved disease haplotype.

CONCLUSIONS

This study identifies a CTVM susceptibility locus on CFA9 and a founder effect in apparently unrelated Labrador Retriever kindreds. These results provide the basis for a positional candidate cloning effort to identify the CTVM disease gene. Identification of the CTVM gene will permit mutation screening of patients with Ebstein anomaly, which should provide additional insights into the genetic programmes of valve development.

Ebstein's anomaly in siblings: an original observation

Siblings, a 26-year old male and a 31-year old female, were found do have Ebstein's anomaly. Ebstein's anomaly is characterized by a downward displacement of the tricuspid valve into the right ventricle due to anomalous attachment of the tricuspid leaflets. Echocardiography is the method of choice to diagnose Ebstein's anomaly on its own or in association with other heart defects. Complications such as right ventricular failure, infective endocarditis, and paradoxical embolism can occur. Ebstein's anomaly diagnosed in adult life is a benign and stable disease, particularly if the patient is asymptomatic. These cases may represent a familial form of Ebstein's anomaly.

[Familial occurrence of Ebstein anomaly]

Ebstein anomaly is a rare congenital disease which affects location, structure and mobility of the tricuspid valve, and right atrium and ventricle. Although most cases are sporadic, familial occurrence has been reported. We report 2 brothers born with Ebstein anomaly. The parents were first degree cousins and there were 8 other children. 2 daughters were born with other congenital heart anomalies, 1 with ventricular septal defect and the other with severe pulmonary artery stenosis. We suggest that in some families, Ebstein anomaly is an autosomal dominant disease with different expression in the sexes.

Congenital malformations of the tricuspid valve in siblings

The occurrence of familial heart disease in association with tricuspid atresia is rare. The first reported instance of tricuspid atresia and Ebstein's anomaly in siblings is presented. The presence of these two distinct pathologic variants of tricuspid valve malformations in siblings suggests that these malformations result from a common abnormality occurring during the development of the inlet portion of the right ventricle.

Ebstein's malformation of the tricuspid valve: genetic and environmental factors. The Baltimore-Washington Infant Study Group

Ebstein's anomaly is a specific structural deformity of the tricuspid valve, and its rarity has hampered etiologic evaluation. Cases of Ebstein's anomaly registered in the Baltimore Washington Infant Study (BWIS), a regional case-control study of cardiovascular malformations (CVM) in infancy, are reviewed. Between 1981 and 1989 a total of 4,390 CVM cases, including 47 Ebstein cases, and 3,572 controls were registered. The prevalence of Ebstein's anomaly was 5.2 per 100,000 livebirths. Additional cardiac anomalies were present in 38.3% of Ebstein cases. Non-cardiac malformations were present in 19.1% of Ebstein cases vs. 25.5% of other CVM, and 1.7% of controls. Case-fatality by 1 year of age was 23.4% in Ebstein vs. 18.1% in other CVM. Interviews of parents of Ebstein cases, other CVM, and controls (n = 44, 3,335, and 3,572, respectively) elicited information on family history of malformations, maternal illnesses, reproductive history, therapeutic drugs, parental lifestyle, and environmental exposures during the periconceptional period. Case-control analyses suggest genetic, reproductive, and environmental risk factors: twins [odds ratio (OR) 8.2, 95% confidence interval (CI) 2.6-25.3]; family history of CVM (OR 6.4, 95% CI 1.8-22.2); white race (OR 2.9 with non-whites as reference, 95% CI 1.2-7.0); previous miscarriages (OR 2.0, 95% CI 1.2-3.3); maternal exposure to benzodiazepines (OR 5.4, 95% CI 1.5-19.1); and varnishing (OR 3.4, 95% CI 1.3-9.1). Additional multicenter investigations are warranted to elucidate the role of genetic, reproductive, and environmental factors in the etiology of this anomaly.

Ebstein anomaly: report of a familial occurrence and prenatal diagnosis

The Ebstein anomaly is a rare congenital heart disease involving the position and structure of the tricuspid valve. Although most cases are sporadic, familial occurrence has been documented. We report on 2 sisters, born to consanguineous parents, who were diagnosed prenatally with severe Ebstein anomaly.

Familial Ebstein's anomaly: a report of six cases in two generations associated with mild skeletal abnormalities

In a family of 11 persons in three generations six had Ebstein's anomaly. Five of the six showed mild skeletal anomalies--that is, restricted finger extension, with or without limitation of larger joints, and externally rotated little toes. Two other members of the family had the skeletal features without Ebstein's anomaly. The findings suggest a dominantly inherited syndrome of Ebstein's anomaly and skeletal abnormalities. The four female patients were all mildly affected whereas three of the four male patients were severely affected.

Persistent atrial standstill in familial Ebstein's anomaly

Persistent atrial standstill occurred in a father and his youngest son with familial Ebstein's anomaly. In both cases routine electrocardiograms showed no atrial electrical activity and cross sectional echocardiograms showed inferior displacement of the septal tricuspid leaflet and tethering of the tricuspid leaflets to the right ventricle. The father had a cerebral embolism and died of a myocardial infarction. Necropsy showed attachment of the septal tricuspid leaflet below the membranous septum. On serial histological examination fibrofatty infiltration of the right atrial wall, the atrioventricular node, and the inferior part of the His bundle up to the bifurcation was present. The son had haemodynamic and electrophysiological findings consistent with mild Ebstein's anomaly and persistent atrial standstill, for which permanent cardiac pacing was necessary. The persistent atrial standstill with slow escape rhythm was most probably a consequence of the abnormalities in both the atrial wall and the His bundle which, together with the abnormal attachment of the tricuspid valve, may be features of the same congenital cardiac anomaly.

Familial Ebstein's anomaly

2 adult siblings with Ebstein's anomaly are presented in this report. The second sibling was found to have the anomaly 20 years after the first sibling was diagnosed. The use of echocardiography in screening for Ebstein's anomaly and the diagnostic features are emphasized. Documentation by electrode catheter recording intracardiac electrocardiogram and pressures in the right heart were made.

Familial Ebstein's anomaly

A family is described in which both a father and son are affected with Ebstein's anomaly, while several other family members manifest different cardiac malformations. Five additional instances of familial Ebstein's anomaly were found in the literature and compared with our family. Inspection of possible modes of inheritance in this group of families suggests that Ebstein's anomaly is probably inherited as a polygenic character with a threshold phenomenon.

Ebstein's anomaly. Genetic study of 26 families

The families of 26 patients with Ebstein's anomaly were examined. There were 120 first-degree relatives, 100 of whom were living, and 93 of these were examined. Information was available on 14 of the 20 who had died. No case of Ebstein's anomaly was found among the first-degree relatives, but 2 had ventricular septal defects and another, who died at 7 months, was said to have had congenital heart disease. In more distant relatives there were 6 with congenital heart disease, including 2 with ventricular septal defects and 2 with Fallot's tetralogy.