Genetic Determinants and Genotype-Phenotype Correlations in Vietnamese Patients With Dilated Cardiomyopathy

Systematic Review, Meta-Analysis, and Population Study to Determine the Biologic Sex Ratio in Dilated Cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) appears to be diagnosed twice as often in male than in female patients. This could be attributed to underdiagnosis in female patients or sex differences in susceptibility. Up to 30% of cases have an autosomal dominant monogenic cause, where equal sex prevalence would be expected. The aim of this systematic review, meta-analysis, and population study was to assess the sex ratio in patients with DCM, stratified by genetic status, and evaluate whether this is influenced by diagnostic bias.

METHODS

A literature search identified DCM patient cohorts with discernible sex ratios. Exclusion criteria were studies with a small (n<100), pediatric, or peripartum population. Meta-analysis and metaregression compared the proportion of female participants for an overall DCM cohort and the following subtypes: all genetic DCM, individual selected DCM genes (TTN and LMNA), and gene-elusive DCM. Population DCM sex ratios generated from diagnostic codes were also compared with those from sex-specific means using the UK Biobank imaging cohort; this established ICD coded, novel imaging-first, and genotype first determined sex ratios.

RESULTS

A total of 99 studies, with 37 525 participants, were included. The overall DCM cohort had a 0.30 female proportion (95% CI, 0.28-0.32), corresponding to a male:female ratio (M:F) of 2.38:1. This was similar to patients with an identified DCM variant (0.31 [95% CI, 0.26-0.36]; M:F 2.22:1; P=0.56). There was also no significant difference when compared with patients with gene-elusive DCM (0.30 [95% CI, 0.24-0.37]; M:F 2.29:1; P=0.81). Furthermore, the ratio within autosomal dominant gene variants was not significantly different for TTN (0.28 [95% CI, 0.22-0.36]; M:F 2.51:1; P=0.82) or LMNA (0.35 [95% CI, 0.27-0.44]; M:F 1.84:1; P=0.41). Overall, the sex ratio for DCM in people with disease attributed to autosomal dominant gene variants was similar to the all-cause group (0.34 [95% CI, 0.28-0.40]; M:F 1.98:1; P=0.19). In the UK Biobank (n=47 549), DCM defined by International Classification of Diseases, 10th revision, coding had 4.5:1 M:F. However, implementing sex-specific imaging-first and genotype-first diagnostic approaches changed this to 1.7:1 and 2.3:1, respectively.

CONCLUSIONS

This study demonstrates that DCM is twice as prevalent in male patients. This was partially mitigated by implementing sex-specific DCM diagnostic criteria. The persistent male excess in genotype-positive patients with an equally prevalent genetic risk suggests additional genetic or environmental drivers for sex-biased penetrance.

REGISTRATION

URL: https://www.crd.york.ac.uk/prospero; Unique identifier: CRD42023451944.

Unveiling the Spectrum of Minor Genes in Cardiomyopathies: A Narrative Review

Hereditary cardiomyopathies (CMPs), including arrhythmogenic cardiomyopathy (ACM), dilated cardiomyopathy (DCM), and hypertrophic cardiomyopathy (HCM), represent a group of heart disorders that significantly contribute to cardiovascular morbidity and mortality and are often driven by genetic factors. Recent advances in next-generation sequencing (NGS) technology have enabled the identification of rare variants in both well-established and minor genes associated with CMPs. Nowadays, a set of core genes is included in diagnostic panels for ACM, DCM, and HCM. On the other hand, despite their lesser-known status, variants in the minor genes may contribute to disease mechanisms and influence prognosis. This review evaluates the current evidence supporting the involvement of the minor genes in CMPs, considering their potential pathogenicity and clinical significance. A comprehensive analysis of databases, such as ClinGen, ClinVar, and GeneReviews, along with recent literature and diagnostic guidelines provides a thorough overview of the genetic landscape of minor genes in CMPs and offers guidance in clinical practice, evaluating each case individually based on the clinical referral, and insights for future research. Given the increasing knowledge on these less understood genetic factors, future studies are essential to clearly assess their roles, ultimately leading to improved diagnostic precision and therapeutic strategies in hereditary CMPs.

Prevalence of Genetically Associated Dilated Cardiomyopathy: A Systematic Literature Review and Meta-Analysis

Background

Dilated cardiomyopathy (DCM) is a leading cause of heart failure and cardiac transplantation globally. Disease-associated genetic variants play a significant role in the development of DCM. Accurately determining the prevalence of genetically associated DCM (genetic DCM) is important for developing targeted prevention strategies. This review synthesized published literature on the global prevalence of genetic DCM across various populations, focusing on two of the most common variants: titin (TTN) and myosin heavy chain 7 (MYH7).

Methods

MEDLINE® and Embase were searched from database inception to September 19, 2022 for English-language studies reporting the prevalence of genetic DCM within any population. Studies using family history as a proxy for genetic DCM were excluded.

Results

Of 2,736 abstracts, 57 studies were included. Among the global adult or mixed (mostly adults with few pediatric patients) DCM population, median prevalence was 20.2% (interquartile range (IQR): 16.3-36.0%) for overall genetic DCM, 11.4% (IQR: 8.2-17.8%) for TTN-associated DCM, and 3.2% (IQR: 1.8-5.2%) for MYH7-associated DCM. Global prevalence of overall pediatric genetic DCM within the DCM population was similar (weighted mean: 21.3%). Few studies reported data on the prevalence of genetic DCM within the general population.

Conclusions

Our study identified variable prevalence estimates of genetic DCM across different populations and geographic locations. The current evidence may underestimate the genetic contributions due to limited screening and detection of potential DCM patients. Epidemiological studies using long-read whole genome sequencing to identify structural variants or non-coding variants are needed, as well as large cohort datasets with genotype-phenotype correlation analyses.

Genetic Characterization of Dilated Cardiomyopathy in Romanian Adult Patients

Dilated cardiomyopathy (DCM) represents a group of disorders affecting the structure and function of the heart muscle, leading to a high risk of heart failure and sudden cardiac death (SCD). DCM frequently involves an underlying genetic etiology. Genetic testing is valuable for risk stratification, treatment decisions, and family screening. Romanian population data on the genetic etiology of DCM are lacking. We aimed to investigate the genetic causes for DCM among Romanian adult patients at tertiary referral centers across the country. Clinical and genetic investigations were performed on adult patients presenting to tertiary hospitals in Romania. The genetic investigations used next-generation sequencing panels of disease-associated DCM genes. A total of 122 patients with DCM underwent genetic testing. The mean age at DCM diagnosis was 41.6 ± 12.4 years. The genetic investigations identified pathogenic or likely pathogenic variants in 50.8% of participants, while 25.4% had variants of unknown significance. Disease-causing variants in 15 genes were identified in people with DCM, with 31 previously unreported variants. Variants in TTN, LMNA, and DSP explained 75% of genetic causes for DCM. In total, 52.4% of patients had a family history of DCM/SCD. Left ventricular ejection fraction of <35% was observed in 41.9% of patients with disease-causing variants and 55% with negative or uncertain findings. Further genotype-phenotype correlations were explored in this study population. The substantial percentage (50.8%) of disease-causing variants identified in patients with DCM acknowledges the importance of genetic investigations. This study highlights the genetic landscape in genes associated with DCM in the Romanian population.

Mechanisms of RBM20 Cardiomyopathy: Insights From Model Systems

RBM20 (RNA-binding motif protein 20) is a vertebrate- and muscle-specific RNA-binding protein that belongs to the serine-arginine-rich family of splicing factors. The RBM20 gene was first identified as a dilated cardiomyopathy-linked gene over a decade ago. Early studies in Rbm20 knockout rodents implicated disrupted splicing of RBM20 target genes as a causative mechanism. Clinical studies show that pathogenic variants in RBM20 are linked to aggressive dilated cardiomyopathy with early onset heart failure and high mortality. Subsequent studies employing pathogenic variant knock-in animal models revealed that variants in a specific portion of the arginine-serine-rich domain in RBM20 not only disrupt splicing but also hinder nucleocytoplasmic transport and lead to the formation of RBM20 biomolecular condensates in the sarcoplasm. Conversely, mice harboring a disease-associated variant in the RRM (RNA recognition motif) do not show evidence of adverse remodeling or exhibit sudden death despite disrupted splicing of RBM20 target genes. Thus, whether disrupted splicing, biomolecular condensates, or both contribute to dilated cardiomyopathy is under debate. Beyond this, additional questions remain, such as whether there is sexual dimorphism in the presentation of RBM20 cardiomyopathy. What are the clinical features of RBM20 cardiomyopathy and why do some individuals develop more severe disease than others? In this review, we summarize the reported observations and discuss potential mechanisms of RBM20 cardiomyopathy derived from studies employing in vivo animal models and in vitro human-induced pluripotent stem cell-derived cardiomyocytes. Potential therapeutic strategies to treat RBM20 cardiomyopathy are also discussed.

DMD-Associated Dilated Cardiomyopathy: Genotypes, Phenotypes, and Phenocopies

BACKGROUND

Variants in the DMD gene, that encodes the cytoskeletal protein, dystrophin, cause a severe form of dilated cardiomyopathy (DCM) associated with high rates of heart failure, heart transplantation, and ventricular arrhythmias. Improved early detection of individuals at risk is needed.

METHODS

Genetic testing of 40 male probands with a potential X-linked genetic cause of primary DCM was undertaken using multi-gene panel sequencing, multiplex polymerase chain reaction, and array comparative genomic hybridization. Variant location was assessed with respect to dystrophin isoform patterns and exon usage. Telomere length was evaluated as a marker of myocardial dysfunction in left ventricular tissue and blood.

RESULTS

Four pathogenic/likely pathogenic DMD variants were found in 5 probands (5/40: 12.5%). Only one rare variant was identified by gene panel testing with 3 additional multi-exon deletion/duplications found following targeted assays for structural variants. All of the pathogenic/likely pathogenic DMD variants involved dystrophin exons that had percent spliced-in scores >90, indicating high levels of constitutive expression in the human adult heart. Fifteen DMD variant-negative probands (15/40: 37.5%) had variants in autosomal genes including TTN, BAG3, LMNA, and RBM20. Myocardial telomere length was reduced in patients with DCM irrespective of genotype. No differences in blood telomere length were observed between genotype-positive family members with/without DCM and controls.

CONCLUSIONS

Primary genetic testing using multi-gene panels has a low yield and specific assays for structural variants are required if DMD-associated cardiomyopathy is suspected. Distinguishing X-linked causes of DCM from autosomal genes that show sex differences in clinical presentation is crucial for informed family management.

Diagnostic yield of genetic testing in a multinational heterogeneous cohort of 2088 DCM patients

Background

Familial dilated cardiomyopathy (DCM) causes heart failure and may lead to heart transplantation. DCM is typically a monogenic disorder with autosomal dominant inheritance. Currently disease-causing variants have been reported in over 60 genes that encode proteins in sarcomeres, nuclear lamina, desmosomes, cytoskeleton, and mitochondria. Over half of the patients undergoing comprehensive genetic testing are left without a molecular diagnosis even when patient selection follows strict DCM criteria.

Methods and results

This study was a retrospective review of patients referred for genetic testing at Blueprint Genetics due to suspected inherited DCM. Next generation sequencing panels included 23-316 genes associated with cardiomyopathies and other monogenic cardiac diseases. Variants were considered diagnostic if classified as pathogenic (P) or likely pathogenic (LP). Of the 2,088 patients 514 (24.6%) obtained a molecular diagnosis; 534 LP/P variants were observed across 45 genes, 2.7% (14/514) had two diagnostic variants in dominant genes. Nine copy number variants were identified: two multigene and seven intragenic. Diagnostic variants were observed most often in TTN (45.3%), DSP (6.7%), LMNA (6.7%), and MYH7 (5.2%). Clinical characteristics independently associated with molecular diagnosis were: a lower age at diagnosis, family history of DCM, paroxysmal atrial fibrillation, absence of left bundle branch block, and the presence of an implantable cardioverter-defibrillator.

Conclusions

Panel testing provides good diagnostic yield in patients with clinically suspected DCM. Causative variants were identified in 45 genes. In minority, two diagnostic variants were observed in dominant genes. Our results support the use of genetic panels in clinical settings in DCM patients with suspected genetic etiology.

Dilated cardiomyopathy caused by a pathogenic nucleotide variant in RBM20 in an Iranian family

Introduction

Dilated cardiomyopathy (DCM) is characterized by the dilation and impaired contraction of 1 or both ventricles and can be caused by a variety of disorders. Up to 50% of idiopathic DCM cases have heritable familial diseases, and the clinical screening of family members is recommended. Identifying a genetic cause that can explain the DCM risk in the family can help with better screening planning and clinical decision-making. Whole-exome sequencing (WES) has aided significantly in the detection of causative genes in many genetically heterogeneous diseases. In the present study, we applied WES to identify the causative genetic variant in a family with heritable DCM.

Methods

WES was applied to identify genetic variants on a 26-year-old man as the proband of a family with DCM. Subsequently, Sanger sequencing was performed to confirm the variant in the patient and all the available affected and unaffected family members. The pathogenicity of the variant was evaluated through co-segregation analysis in the family and employment of in silico predictive software.

Results

WES demonstrated the missense pathogenic heterozygous nucleotide variant, c.1907G > A, (p.Arg636His, rs267607004, NM_0011343), in exon 9 of the RBM20 gene in the proband. The variant was co-segregated in all the affected family members in a heterozygous form and the unaffected family members. The in silico analysis confirmed the variant as pathogenic.

Conclusion

Pathogenic RBM20 nucleotide variants are associated with arrhythmogenic DCM. We believe that our report is the first to show an RBM20 variant in Iranian descent associated with DCM.

Genetics in Congenital Heart Diseases: Unraveling the Link Between Cardiac Morphogenesis, Heart Muscle Disease, and Electrical Disorders

The genetic background of congenital heart diseases (CHDs) is extremely complex, heterogenous, and still majorly to be determined. CHDs can be sporadic or familial. In this article we discuss in detail the phenotypic spectrum of selected genes including MYH7, GATA4, NKX2-5, TBX5, and TBX20. Our goal is to offer the clinician a general overview of the clinical spectrum of the analyzed topics that are traditionally known as causative for CHDs but we underline in this review the possible progressive functional (cardiomyopathy) and electric aspects (arrhythmias) caused by the genetic background.