Frequency, Penetrance, and Variable Expressivity of Dilated Cardiomyopathy-Associated Putative Pathogenic Gene Variants in UK Biobank Participants

Navigating the penetrance and phenotypic spectrum of inherited cardiomyopathies

Inherited cardiomyopathies are genetic diseases that can lead to heart failure and sudden cardiac death. These conditions tend to run in families, following an autosomal dominant pattern where first-degree relatives have a 50% chance of carrying the pathogenic variant. Despite significant advancements and increased accessibility of genetic testing, accurately predicting the phenotypic expression of these conditions remains challenging due to the inherent variability in their clinical manifestations and the incomplete penetrance observed. This poses challenges in providing patient care and effectively communicating the potential risk of future disease to patients and their families. To address these challenges, this review aims to synthesize the available evidence on penetrance, expressivity, and factors influencing disease expression to improve communication and risk assessment for patients with inherited cardiomyopathies and their family members.

Penetrance of Dilated Cardiomyopathy in Genotype-Positive Relatives

BACKGROUND

Disease penetrance in genotype-positive (G+) relatives of families with dilated cardiomyopathy (DCM) and the characteristics associated with DCM onset in these individuals are unknown.

OBJECTIVES

This study sought to determine the penetrance of new DCM diagnosis in G+ relatives and to identify factors associated with DCM development.

METHODS

The authors evaluated 779 G+ patients (age 35.8 ± 17.3 years; 459 [59%] females; 367 [47%] with variants in TTN) without DCM followed at 25 Spanish centers.

RESULTS

After a median follow-up of 37.1 months (Q1-Q3: 16.3-63.8 months), 85 individuals (10.9%) developed DCM (incidence rate of 2.9 per 100 person-years; 95% CI: 2.3-3.5 per 100 person-years). DCM penetrance and age at DCM onset was different according to underlying gene group (log-rank P = 0.015 and P <0.01, respectively). In a multivariable model excluding CMR parameters, independent predictors of DCM development were: older age (HR per 1-year increase: 1.02; 95% CI: 1.0-1.04), an abnormal electrocardiogram (HR: 2.13; 95% CI: 1.38-3.29); presence of variants in motor sarcomeric genes (HR: 1.92; 95% CI: 1.05-3.50); lower left ventricular ejection fraction (HR per 1% increase: 0.86; 95% CI: 0.82-0.90) and larger left ventricular end-diastolic diameter (HR per 1-mm increase: 1.10; 95% CI: 1.06-1.13). Multivariable analysis in individuals with cardiac magnetic resonance and late gadolinium enhancement assessment (n = 360, 45%) identified late gadolinium enhancement as an additional independent predictor of DCM development (HR: 2.52; 95% CI: 1.43-4.45).

CONCLUSIONS

Following a first negative screening, approximately 11% of G+ relatives developed DCM during a median follow-up of 3 years. Older age, an abnormal electrocardiogram, lower left ventricular ejection fraction, increased left ventricular end-diastolic diameter, motor sarcomeric genetic variants, and late gadolinium enhancement are associated with a higher risk of developing DCM.

Prospective study design and data analysis in UK Biobank

Population-based prospective studies, such as UK Biobank, are valuable for generating and testing hypotheses about the potential causes of human disease. We describe how UK Biobank's study design, data access policies, and approaches to statistical analysis can help to minimize error and improve the interpretability of research findings, with implications for other population-based prospective studies being established worldwide.

Postmortem genetic testing in sudden unexplained death: A public health laboratory experience

Sudden unexplained death in the young poses a diagnostically challenging situation for practicing autopsy pathologists, especially in the absence of anatomic and toxicological findings. Postmortem genetic testing may identify pathogenic variants in the deceased of such cases, including those associated with arrhythmogenic channelopathies and cardiomyopathies. The Wisconsin State Laboratory of Hygiene (WSLH) is a state-run public health laboratory which performs postmortem genetic testing at no cost to Wisconsin medical examiners and coroners. The current study examines sequencing data from 18 deceased patients (ages 2 months to 49 years, 5 females) submitted to WSLH, from 2016 to 2021. Panel-based analysis was performed on 10 cases, and whole exome sequencing was performed on the most recent 8 cases. Genetic variants were identified in 14 of 18 decedents (77.8%), including 7 with pathogenic or likely pathogenic variants (38.9%). Whole exome sequencing was more likely to yield a positive result, more variants per decedent, and a larger number of variants of uncertain significance. While panel-based testing may offer definitive pathogenic variants in some cases, less frequent variants may be excluded. Whole exome testing may identify rare variants missed by panels, but increased yield of variants of uncertain significance may be difficult to interpret. Postmortem genetic testing in young decedents of sudden unexplained death can provide invaluable information to autopsy pathologists to establish accurate cause and manner of death and to decedent's relatives to allow appropriate management. A public health laboratory model may be a financially advisable alternative to commercial laboratories for medical examiner's/coroner's offices.

Peripheral temperature dysregulation associated with functionally altered NaV1.8 channels

The voltage-gated sodium channel NaV1.8 is prominently expressed in the soma and axons of small-caliber sensory neurons, and pathogenic variants of the corresponding gene SCN10A are associated with peripheral pain and autonomic dysfunction. While most disease-associated SCN10A variants confer gain-of-function properties to NaV1.8, resulting in hyperexcitability of sensory neurons, a few affect afferent excitability through a loss-of-function mechanism. Using whole-exome sequencing, we here identify a rare heterozygous SCN10A missense variant resulting in alteration p.V1287I in NaV1.8 in a patient with a 15-year history of progressively worsening temperature dysregulation in the distal extremities, particularly in the feet. Further symptoms include increasingly intensifying tingling and numbness in the fingers and increased sweating. To assess the impact of p.V1287I on channel function, we performed voltage-clamp recordings demonstrating that the alteration confers loss- and gain-of-function characteristics to NaV1.8 characterized by a right-shifted voltage dependence of channel activation and inactivation. Current-clamp recordings from transfected mouse dorsal root ganglion neurons further revealed that NaV1.8-V1287I channels broaden the action potentials of sensory neurons and increase their firing rates in response to depolarizing current stimulations, indicating a gain-of-function mechanism of the variant at the cellular level in a heterozygous setting. The data support the hypothesis that the properties of NaV1.8 p.V1287I are causative for the patient's symptoms and that nonpainful peripheral paresthesias should be considered part of the clinical spectrum of NaV1.8-associated disorders.

The Role of Genetics in the Management of Heart Failure Patients

Over the last decades, the relevance of genetics in cardiovascular diseases has expanded, especially in the context of cardiomyopathies. Its relevance extends to the management of patients diagnosed with heart failure (HF), given its capacity to provide invaluable insights into the etiology of cardiomyopathies and identify individuals at a heightened risk of poor outcomes. Notably, the identification of an etiological genetic variant necessitates a comprehensive evaluation of the family lineage of the affected patients. In the future, these genetic variants hold potential as therapeutic targets with the capability to modify gene expression. In this complex setting, collaboration among cardiologists, specifically those specializing in cardiomyopathies and HF, and geneticists becomes paramount to improving individual and family health outcomes, as well as therapeutic clinical results. This review is intended to offer geneticists and cardiologists an updated perspective on the value of genetic research in HF and its implications in clinical practice.

Cardiomyopathy in Asian Cohorts: Genetic and Epigenetic Insights

Previous studies on cardiomyopathies have been particularly valuable for clarifying pathological mechanisms in heart failure, an etiologically heterogeneous disease. In this review, we specifically focus on cardiomyopathies in Asia, where heart failure is particularly pertinent. There has been an increase in prevalence of cardiomyopathies in Asia, in sharp contrast with the decline observed in Western countries. Indeed, important disparities in cardiomyopathy incidence, clinical characteristics, and prognosis have been reported in Asian versus White cohorts. These have been accompanied by emerging descriptions of a distinct rare and common genetic basis for disease among Asian cardiomyopathy patients marked by an increased burden of variants with uncertain significance, reclassification of variants deemed pathogenic based on evidence from predominantly White cohorts, and the discovery of Asian-specific cardiomyopathy-associated loci with underappreciated pathogenicity under conventional classification criteria. Findings from epigenetic studies of heart failure, particularly DNA methylation studies, have complemented genetic findings in accounting for the phenotypic variability in cardiomyopathy. Though extremely limited, findings from Asian ancestry-focused DNA methylation studies of cardiomyopathy have shown potential to contribute to general understanding of cardiomyopathy pathophysiology by proposing disease and cause-relevant pathophysiological mechanisms. We discuss the value of multiomics study designs incorporating genetic, methylation, and transcriptomic information for future DNA methylation studies in Asian cardiomyopathy cohorts to yield Asian ancestry-specific insights that will improve risk stratification in the Asian population.

Predicted Deleterious Variants in Cardiomyopathy Genes Prognosticate Mortality and Composite Outcomes in UK Biobank

BACKGROUND

Inherited cardiomyopathies present with broad variation of phenotype. Data are limited regarding genetic screening strategies and outcomes associated with predicted deleterious variants in cardiomyopathy-associated genes in the general population.

OBJECTIVES

The authors aimed to determine the risk of mortality and composite cardiomyopathy-related outcomes associated with predicted deleterious variants in cardiomyopathy-associated genes in the UK Biobank.

METHODS

Using whole exome sequencing data, variants in dilated, hypertrophic, and arrhythmogenic right ventricular cardiomyopathy-associated genes with at least moderate evidence of disease causality according to ClinGen Expert Panel curations were annotated using REVEL (≥0.65) and ANNOVAR (predicted loss-of-function) considering gene-disease mechanisms. Genotype-positive and genotype-negative groups were compared using time-to-event analyses for the primary (all-cause mortality) and secondary outcomes (diagnosis of cardiomyopathy; composite outcome of diagnosis of cardiomyopathy, heart failure, arrhythmia, stroke, and death).

RESULTS

Among 200,619 participants (age at recruitment 56.46 ± 8.1 years), 5,292 (2.64%) were found to host ≥1 predicted deleterious variants in cardiomyopathy-associated genes (CMP-G+). After adjusting for age and sex, CMP-G+ individuals had higher risk for all-cause mortality (HR: 1.13 [95% CI: 1.01-1.25]; P = 0.027), increased risk for being diagnosed with cardiomyopathy later in life (HR: 5.75 [95% CI: 4.58-7.23]; P < 0.0001), and elevated risk for composite outcome (HR: 1.29 [95% CI: 1.20-1.39]; P < 0.0001) than CMP-G- individuals. The higher risk for being diagnosed with cardiomyopathy and composite outcomes in the genotype-positive subjects remained consistent across all cardiomyopathy subgroups.

CONCLUSIONS

Adults with predicted deleterious variants in cardiomyopathy-associated genes exhibited a slightly higher risk of mortality and a significantly increased risk of developing cardiomyopathy, and cardiomyopathy-related composite outcomes, in comparison with genotype-negative controls.

The Genetic Evaluation of Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is a common cause of heart failure and is the primary indication for heart transplantation. A genetic etiology can be found in 20-35% of patients with DCM, especially in those with a family history of cardiomyopathy or sudden cardiac death at an early age. With advancements in genome sequencing, the understanding of genotype-phenotype relationships in DCM has expanded with over 60 genes implicated in the disease. Subsequently, these findings have increased adoption of genetic testing in the management of DCM, which has allowed for improved risk stratification and identification of at risk family members. In this review, we discuss the genetic evaluation of DCM with a focus on practical genetic testing considerations, genotype-phenotype associations, and insights into upcoming personalized therapies.

Principles of Genetic Counseling in Inherited Heart Conditions

Cardiac genetic counseling is the process of helping individuals adapt to a personal diagnosis or family history of an inherited heart condition. The process is shown to benefit patients and includes specialized skills, such as counseling children and interpreting complex genetic results. Emerging areas include: evolving service delivery models for caring for patients and communicating risk to relatives, new areas of need including postmortem molecular autopsy, and new populations of individuals found to carry a likely pathogenic/pathogenic cardiac variant identified through genomic screening. This article provides an overview of the cardiac genetic counseling process and evolving areas in the field.

Actionability of unanticipated monogenic disease risks in newborn genomic screening: Findings from the BabySeq Project

Newborn genomic sequencing (NBSeq) to screen for medically important genetic information is of considerable interest but data characterizing the actionability of such findings, and the downstream medical efforts in response to discovery of unanticipated genetic risk variants, are lacking. From a clinical trial of comprehensive exome sequencing in 127 apparently healthy infants and 32 infants in intensive care, we previously identified 17 infants (10.7%) with unanticipated monogenic disease risks (uMDRs). In this analysis, we assessed actionability for each of these uMDRs with a modified ClinGen actionability semiquantitative metric (CASQM) and created radar plots representing degrees of penetrance of the condition, severity of the condition, effectiveness of intervention, and tolerability of intervention. In addition, we followed each of these infants for 3-5 years after disclosure and tracked the medical actions prompted by these findings. All 17 uMDR findings were scored as moderately or highly actionable on the CASQM (mean 9, range: 7-11 on a 0-12 scale) and several distinctive visual patterns emerged on the radar plots. In three infants, uMDRs revealed unsuspected genetic etiologies for existing phenotypes, and in the remaining 14 infants, uMDRs provided risk stratification for future medical surveillance. In 13 infants, uMDRs prompted screening for at-risk family members, three of whom underwent cancer-risk-reducing surgeries. Although assessments of clinical utility and cost-effectiveness will require larger datasets, these findings suggest that large-scale comprehensive sequencing of newborns will reveal numerous actionable uMDRs and precipitate substantial, and in some cases lifesaving, downstream medical care in newborns and their family members.

Single coronary artery presenting dilated cardiomyopathy and hyperlipidemia with the SCN5A and APOA5 gene mutation: A case report and review of the literature

We present a 55-year-old man with chest tightness and dyspnoea after activity lasting for 2 months who was diagnosed with single coronary artery (SCA) and presented with dilated cardiomyopathy (DCM) with the c.1858C > T mutation in the SCN5A gene. The computed tomography coronary angiogram (CTCA) showed congenital absence of the right coronary artery (RCA), and the right heart was nourished by the left coronary artery branch with no apparent stenosis. Transthoracic echocardiography (TTE) revealed enlargement of the left heart and cardiomyopathy. Cardiac magnetic resonance imaging (CMR) revealed DCM. Genetic testing showed that the c.1858C > T variant of the SCN5A gene could lead to Brugada syndrome and DCM. SCA is a rare congenital anomaly of the coronary anatomy, and this case reported as SCA accompanied by DCM is even rarer. We present a rare case of a 55-year-old man with DCM with the c.1858C > T (p. Arg620Cys)/c.1008G > A (p.(Pro336=) variant of the SCN5A gene, congenital absence of RCA, and c.990_993delAACA (p. Asp332Valfs*5) variant of the APOA5 gene. To our knowledge, this is the first report of DCM combined with the SCN5A gene mutation in SCA after searching the PubMed, CNKI and Wanfang databases.

VEZF1 loss-of-function mutation underlying familial dilated cardiomyopathy

Dilated cardiomyopathy (DCM), characteristic of left ventricular or biventricular dilation with systolic dysfunction, is the most common form of cardiomyopathy, and a leading cause of heart failure and sudden cardiac death. Aggregating evidence highlights the underlying genetic basis of DCM, and mutations in over 100 genes have been causally linked to DCM. Nevertheless, due to pronounced genetic heterogeneity, the genetic defects underpinning DCM in most cases remain obscure. Hence, this study was sought to identify novel genetic determinants of DCM. In this investigation, whole-exome sequencing and bioinformatics analyses were conducted in a family suffering from DCM, and a novel heterozygous mutation in the VEZF1 gene (coding for a zinc finger-containing transcription factor critical for cardiovascular development and structural remodeling), NM_007146.3: c.490A > T; p.(Lys164*), was identified. The nonsense mutation was validated by Sanger sequencing and segregated with autosome-dominant DCM in the family with complete penetrance. The mutation was neither detected in another cohort of 200 unrelated DCM patients nor observed in 400 unrelated healthy individuals nor retrieved in the Single Nucleotide Polymorphism database, the Human Gene Mutation Database and the Genome Aggregation Database. Biological analyses by utilizing a dual-luciferase reporter assay system revealed that the mutant VEZF1 protein failed to transactivate the promoters of MYH7 and ET1, two genes that have been associated with DCM. The findings indicate VEZF1 as a new gene responsible for DCM, which provides novel insight into the molecular pathogenesis of DCM, implying potential implications for personalized precisive medical management of the patients affected with DCM.

Genetically transitional disease: a new concept in genomic medicine

Traditional classification of genetic diseases as monogenic and polygenic has lagged far behind scientific progress. In this opinion article, we propose and define a new terminology, genetically transitional disease (GTD), referring to cases where a large-effect mutation is necessary, but not sufficient, to cause disease. This leads to a working disease nosology based on gradients of four types of genetic architecture: monogenic, polygenic, GTD, and mixed. We present four scenarios under which GTD may occur; namely, subsets of traditionally Mendelian disease, modifiable Tier 1 monogenic conditions, variable penetrance, and situations where a genetic mutational spectrum produces qualitatively divergent pathologies. The implications of the new nosology in precision medicine are discussed, in which therapeutic options may target the molecular cause or the disease phenotype.