Variants In Dilated Cardiomyopathy Research Articles

Age and Sex Differences in the Genetics of Cardiomyopathy

Cardiomyopathy has variable penetrance. We analyzed age and sex-related genetic differences in 1,397 cardiomyopathy patients (Ontario, UK) with whole genome sequencing. Pediatric cases (n = 471) harbored more deleterious protein-coding variants in Tier 1 cardiomyopathy genes compared to adults (n = 926) (34.6% vs 25.9% respectively, p = 0.0015), with variant enrichment in constrained coding regions. Pediatric patients had a higher burden of sarcomere and lower burden of channelopathy gene variants compared to adults. Specifically, pediatric patients had more MYH7 and MYL3 variants in hypertrophic cardiomyopathy, and fewer TTN truncating variants in dilated cardiomyopathy. MYH7 variants clustered in the myosin head and neck domains in children. OBSCN was a top mutated gene in adults, enriched for protein-truncating variants. In dilated cardiomyopathy, female patients had a higher burden of z-disc gene variants compared to males. Genetic differences may explain age and sex-related variability in cardiomyopathy penetrance. Genotype-guided predictions of age of onset can inform pre-test genetic counseling.Graphical Pediatric cardiomyopathy patients were more likely to be genotype-positive than adults with a higher burden of variants in MYH7, MYL3, TNNT2, VCL. Adults had a higher burden of OBSCN and TTN variants. Females with dilated cardiomyopathy (DCM) had a higher burden of z-disc gene variants compared to males.

Mislocalization of pathogenic RBM20 variants in dilated cardiomyopathy is caused by loss-of-interaction with Transportin-3

Severe forms of dilated cardiomyopathy (DCM) are associated with point mutations in the alternative splicing regulator RBM20 that are frequently located in the arginine/serine-rich domain (RS-domain). Such mutations can cause defective splicing and cytoplasmic mislocalization, which leads to the formation of detrimental cytoplasmic granules. Successful development of personalized therapies requires identifying the direct mechanisms of pathogenic RBM20 variants. Here, we decipher the molecular mechanism of RBM20 mislocalization and its specific role in DCM pathogenesis. We demonstrate that mislocalized RBM20 RS-domain variants retain their splice regulatory activity, which reveals that aberrant cellular localization is the main driver of their pathological phenotype. A genome-wide CRISPR knockout screen combined with image-enabled cell sorting identified Transportin-3 (TNPO3) as the main nuclear importer of RBM20. We show that the direct RBM20-TNPO3 interaction involves the RS-domain, and is disrupted by pathogenic variants. Relocalization of pathogenic RBM20 variants to the nucleus restores alternative splicing and dissolves cytoplasmic granules in cell culture and animal models. These findings provide proof-of-principle for developing therapeutic strategies to restore RBM20’s nuclear localization in RBM20-DCM patients.

Diagnostic yield and predictive value on left ventricular remodelling of genetic testing in dilated cardiomyopathy.

We assessed the diagnostic yield of genetic testing and the relationship of left ventricular (LV) reverse remodelling (LVRR) with the presence of DNA pathogenic (P) or likely pathogenic (LP) variants in patients with dilated cardiomyopathy (DCM). From 680 outpatients followed at the Heart Failure Outpatient Clinic of our institution, we selected subjects with a diagnosis of DCM as defined by LV ejection fraction (LVEF) ≤40% and LV dilatation not explained by coronary artery disease or other causes. All patients were offered genetic investigation of 42 disease-associated DCM genes with next-generation sequencing. Seventy patients fulfilled the definition of DCM and 66 underwent genetic investigation. We identified 18 P/LP variants in 16 patients, with a diagnostic yield of 24%. The most common variants were truncating TTN variants (n=7), followed by LMNA (n=3), cytoskeleton Z-disc (n=3), ion channel (n=2), motor sarcomeric (n=2), and desmosomal (n=1) genes. After a median follow-up of 53months (inter-quartile range 20-111), patients without P/LP variants exhibited higher systolic and diastolic blood pressure, lower plasma brain natriuretic peptide levels, and a larger extent of LVRR, as reflected by the increase in LVEF (+14% vs. +1%, P=0.0008) and decrease in indexed LV end-diastolic diameter (-6.5 vs. -2mm/m2 , P=0.03) compared with patients with P/LP variants. Our results confirm the high diagnostic yield of genetic testing in selected DCM patients and suggest that identification of P/LP variants in DCM portends poorer LVRR in response to guideline-directed medical therapy.

Identification and in silico characterization of CSRP3 synonymous variants in dilated cardiomyopathy

Synonymous variations have always been ignored while studying the underlying genetic mechanisms for most of the human diseases. However, recent studies have suggested that these silent changes in the genome can alter the protein expression and folding. CSRP3, which is a well-known candidate gene associated with dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM), was screened for 100 idiopathic DCM cases and 100 controls. Three synonymous variations were identified viz., c.96G > A, p.K32=; c.336G > A, p.A112=; c.354G > A, p.E118=. A comprehensive in silico analysis was performed using various web based widely accepted tools, Mfold, Codon Usage, HSF3.1 and RNA22. Mfold predicted structural changes in all the variants except c.96 G > A (p.K32=), however it predicted changes in the stability of mRNA due to all the synonymous variants. Codon bias was observed as evident by the Relative Synonymous Codon Usage and Log Ratio of Codon Usage Frequencies. The Human Splicing Finder also predicted remarkable changes in the regulatory elements in the variants c.336G > A and c.354 G > A. The miRNA target prediction using varied modes available in RNA22 revealed that 70.6% of the target sites of miRNAs in CSRP3 were altered due to variant c.336G > A while 29.41% sites were completely lost. Findings of the present study suggest that synonymous variants revealed striking deviations in the structural conformation of mRNA, stability of mRNA, relative synonymous codon usage, splicing and miRNA binding sites from the wild type suggesting their possible role in the pathogenesis of DCM, either by destabilizing the mRNA structure, or codon usage bias or else altering the cis-acting regulatory elements during splicing.

Rare variants in the FBN1 gene are associated with sporadic dilated cardiomyopathy in a Chinese Han population

Introduction: Dilated cardiomyopathy (DCM) represents a diverse set of myocardial diseases characterized by notable genetic heterogeneity. Although over 50 genes have been associated with DCM, these collectively explain 35% of idiopathic DCM cases. Variants in the FBN1 gene encoding fibrillin-1 are primarily linked to connective tissue disorders. Considering the potential of these disorders to impact myocardial tissue, this study probes into the possible association between FBN1 variants and DCM. Aim: The objective of this study was to investigate the association between FBN1 variants and DCM in a Chinese Han population. Methods and Results: We performed whole-exome sequencing (WES) to identify rare FBN1 variants among 1,059 DCM cases and 514 controls. Utilizing a case-control strategy and the optimal sequence kernel association test (SKAT-O), we found a significant enrichment of rare deleterious FBN1 variants in DCM patients (19 of 1,059 vs. 0 of 514, PSKAT-O = 7.49E-04). Clinical characteristics analysis indicated a higher occurrence of atrial fibrillation and a higher rate of implantable cardioverter-defibrillator (ICD) implantation among DCM patients carrying FBN1 variants (FBN1+) compared to non-carriers (FBN1-). However, these FBN1 variants did not significantly affect primary endpoints, defined as cardiac mortality or heart transplantation, yet appeared to increase the risk of secondary endpoints, including all-cause mortality or heart failure recurrence. Conclusion: The findings suggest an association between rare deleterious variants in the FBN1 gene and DCM in a Chinese Han population. Our findings underline the importance of further research to validate these results and elucidate the role of FBN1 in DCM. Potential Impact of the findings: This research provides fresh insights into the potential role of FBN1 rare variants in DCM, pointing to new directions for future genetic studies and potential therapeutic strategies in DCM management.

802 DIAGNOSTIC YIELD AND PREDICTIVE VALUE ON LEFT VENTRICULAR REVERSE REMODELING OF GENETIC TESTING IN DILATED CARDIOMYOPATHY

Abstract Background Genetic testing is one essential element in the diagnostic workup of patients with idiopathic dilated cardiomyopathy (DCM), and genotype-phenotype correlations are still poorly understood. We assessed the diagnostic yield of genetic testing in a selected DCM cohort including both familial and nonfamilial cases and evaluated phenotypic differences and the relationship of left ventricular reverse remodeling (LVRR) with the presence of pathogenic (P) or likely pathogenic (LP) variants of disease-associated DCM genes. Methods From 680 outpatients with heart with reduced ejection fraction followed at our Heart Failure Outpatient Clinic we selected subjects with a diagnosis of DCM before 65 years of age and without secondary causes of DCM including ischemic, valvular, hypertensive, or drug-induced heart disease or myocarditis. All patients underwent extensive clinical, laboratory, and imaging evaluation at the time of diagnosis and during regular follow-up visits and were offered genetic investigations with Next Generation Sequencing (NGS) of 42 disease-associated DCM genes. Results Of 680 DCM outpatients, 70 fulfilled the definition of idiopathic DCM and 66 gave consent to undergo genetic investigation (median age at diagnosis 57 years, 68% males). A total of 18 pathogenic/likely pathogenic (P/LP) variants were identified in 16 patients (diagnostic yield 24%), the most common (7, 39% of all variants) involving the TTN gene, followed by lamin A/C (n=3), cytoskeleton Z-disk (n=3), motor sarcomeric (n=2), desmosomal (n=1), and ion channel (n=1) gene variants. At the time of DCM diagnosis, patients with P/LP had a higher left ventricular (LV) ejection fraction (LVEF) compared with subjects (31±11% vs 28±8%, p=0.17). After a median follow-up of 53 (IQR 20-111) months, P/LP-positive patients had lower systolic and diastolic blood pressure and higher plasma natriuretic peptide levels than patients without P/LP variants. Patients without P/LP variants exhibited a larger extent of LVRR, as reflected by the increase in LVEF (+14% vs. +1%, p=0.0008) and decrease in LVEDDi (-3 vs. -1 mm/m2, p=0.03) compared with subjects carrying P/LP variants (Figure). Conclusions Our results confirm the high diagnostic yield of genetic testing in selected DCM patients and suggest that identification of P/LP variants in DCM portends poorer left ventricular reverse remodeling in response to guideline-directed medical therapy.

Pathogenic variants damage cell composition and single cell transcription in cardiomyopathies.

Pathogenic variants in genes that cause dilated cardiomyopathy (DCM) and arrhythmogenic cardiomyopathy (ACM) convey high risks for the development of heart failure through unknown mechanisms. Using single-nucleus RNA sequencing, we characterized the transcriptome of 880,000 nuclei from 18 control and 61 failing, nonischemic human hearts with pathogenic variants in DCM and ACM genes or idiopathic disease. We performed genotype-stratified analyses of the ventricular cell lineages and transcriptional states. The resultant DCM and ACM ventricular cell atlas demonstrated distinct right and left ventricular responses, highlighting genotype-associated pathways, intercellular interactions, and differential gene expression at single-cell resolution. Together, these data illuminate both shared and distinct cellular and molecular architectures of human heart failure and suggest candidate therapeutic targets.

A biallelic loss-of-function variant in MYZAP is associated with a recessive form of severe dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) is a primary disorder of the cardiac muscle, characterized by dilatation of the left ventricle and contractile dysfunction. About 50% of DCM cases can be attributed to monogenic causes, whereas the etiology in the remaining patients remains unexplained. We report a family with two brothers affected by severe DCM with onset in the adolescent period. Using exome sequencing, we identified a homozygous premature termination variant in the MYZAP gene in both affected sibs. MYZAP encodes for myocardial zonula adherens protein—a conserved cardiac protein in the intercalated disc structure of cardiomyocytes. The effect of the variant was demonstrated by light and electron microscopy of the heart muscle and immunohistochemical and western blot analysis of the MYZAP protein in the heart tissue of the proband. Functional characterization using patient-derived induced pluripotent stem cell cardiomyocytes revealed significantly lower force and longer time to peak contraction and relaxation consistent with severe contractile dysfunction. We provide independent support for the role of biallelic loss-of-function MYZAP variants in dilated cardiomyopathy. This report extends the spectrum of cardiac disease associated with dysfunction of cardiac intercalated disc junction and sheds light on the mechanisms leading to DCM.

Neonatal-lethal dilated cardiomyopathy due to a homozygous LMOD2 donor splice-site variant

Dilated cardiomyopathy (DCM) is characterized by cardiac enlargement and impaired ventricular contractility leading to heart failure. A single report identified variants in leiomodin-2 (LMOD2) as a cause of neonatally-lethal DCM. Here, we describe two siblings with DCM who died shortly after birth due to heart failure. Exome sequencing identified a homozygous LMOD2 variant in both siblings, (GRCh38)chr7:g.123656237G > A; NM_207163.2:c.273 + 1G > A, ablating the donor 5′ splice-site of intron-1. Pre-mRNA splicing studies and western blot analysis on cDNA derived from proband cardiac tissue, MyoD-transduced proband skin fibroblasts and HEK293 cells transfected with LMOD2 gene constructs established variant-associated absence of canonically spliced LMOD2 mRNA and full-length LMOD2 protein. Immunostaining of proband heart tissue unveiled abnormally short actin-thin filaments. Our data are consistent with LMOD2 c.273 + 1G > A abolishing/reducing LMOD2 transcript expression by: (1) variant-associated perturbation in initiation of transcription due to ablation of the intron-1 donor; and/or (2) degradation of aberrant LMOD2 transcripts (resulting from use of alternative transcription start-sites or cryptic splice-sites) by nonsense-mediated decay. LMOD2 expression is critical for life and the absence of LMOD2 is associated with thin filament shortening and severe cardiac contractile dysfunction. This study describes the first splice-site variant in LMOD2 and confirms the role of LMOD2 variants in DCM.

Association of Genetic Variants With Outcomes in Patients With Nonischemic Dilated Cardiomyopathy

BackgroundThe clinical relevance of genetic variants in nonischemic dilated cardiomyopathy (DCM) is unsettled. ObjectivesThe study sought to assess the prognostic impact of disease-causing genetic variants in DCM. MethodsBaseline and longitudinal clinical data from 1,005 genotyped DCM probands were retrospectively collected at 20 centers. A total of 372 (37%) patients had pathogenic or likely pathogenic variants (genotype positive) and 633 (63%) were genotype negative. The primary endpoint was a composite of major adverse cardiovascular events. Secondary endpoints were end-stage heart failure (ESHF), malignant ventricular arrhythmia (MVA), and left ventricular reverse remodeling (LVRR). ResultsAfter a median follow-up of 4.04 years (interquartile range: 1.70-7.50 years), the primary endpoint had occurred in 118 (31.7%) patients in the genotype-positive group and in 125 (19.8%) patients in the genotype-negative group (hazard ratio [HR]: 1.51; 95% confidence interval [CI]: 1.17-1.94; P = 0.001). ESHF occurred in 60 (16.1%) genotype-positive patients and in 55 (8.7%) genotype-negative patients (HR: 1.67; 95% CI: 1.16-2.41; P = 0.006). MVA occurred in 73 (19.6%) genotype-positive patients and in 77 (12.2%) genotype-negative patients (HR: 1.50; 95% CI: 1.09-2.07; P = 0.013). LVRR occurred in 39.6% in the genotype-positive group and in 46.2% in the genotype-negative group (P = 0.047). Among individuals with baseline left ventricular ejection fraction ≤35%, genotype-positive patients exhibited more major adverse cardiovascular events, ESHF, and MVA than their genotype-negative peers (all P < 0.02). LVRR and clinical outcomes varied depending on the underlying affected gene. ConclusionsIn this study, DCM patients with pathogenic or likely pathogenic variants had worse prognosis than genotype-negative individuals. Clinical course differed depending on the underlying affected gene.

Genetic Overlap of Acute Myocarditis and Inherited Cardiomyopathy

Background: Acute myocarditis is a complex inflammatory disease increasingly associated with dilated cardiomyopathy (DCM) and arrhythmogenic ventricular cardiomyopathy (ACM), but its underlying genetic basis is unknown. We sought to determine if there is a genetic overlap between myocarditis and inherited forms of cardiomyopathy. Methods: Population-based cohort of 336 consecutive patients with acute myocarditis enrolled in London and Maastricht. All participants underwent targeted DNA-sequencing for well-characterised cardiomyopathy-associated genes with comparison to healthy controls (n=1053). Case ascertainment was assessed against national admission data. Findings: Variants of known or likely pathogenicity were identified in 6% of cases compared to <1% of controls (∆+5%; p=0.0097). In London (n=230; median age 33years; 84% men), which was representative of national myocarditis admissions (median age 32years; 71% men; 66% case ascertainment), 4.8% of cases carried rare truncating variants (tv), particularly within ACM genes (3% cases vs 0% controls; odds ratio 8.2; p=0.001). This was predominantly driven by desmoplakin ( DSP )-tv in patients with normal LVEF and ventricular arrhythmia. In Maastricht (n=106; median age 54years; 61% men), there was enrichment of rare tv in DCM genes, particularly TTN -tv found in 7% (all with LVEF<50%) compared to 1% in controls (OR 3.6; p=0.0116). DCM variants occurred in patients with LV dysfunction (median LVEF 39% vs 60%; p<0.0001). During a median follow-up of 1.9years, all-cause mortality was greatest with a DCM variant (18% vs 4% with no variant; OR 5.0; p=0.004). Interpretation: One in 20 myocarditis cases had a DCM- or ACM-associated genetic variant that would potentially inform clinical management and need for family screening. This was dominated by DSP -tv in those with normal LVEF, and TTN -tv in those with reduced LVEF. Routine genetic testing may be beneficial in acute myocarditis. Funding: British Heart Foundation, Alexander Jansons Foundation, Royal Brompton Hospital, Imperial College London, Wellcome Trust, Medical Research Council and Rosetrees Trust. Declaration of Interest: SKP has received honoraria from Bayer Schering and travel support from Circle 42, outside the submitted work. JSW has received personal fees from Myokardia, outside the submitted work. JSW also has a patent (US 62383189—Methods, systems and apparatus for identifying pathogenic gene variants) issued. DJP has received research support from Siemens and Bayer, and personal fees from Bayer and Chiesi, outside the submitted work. All other authors declare no competing interests. Ethical Approval: All participants in cohorts 1, 2 and 3 provided written informed consent as approved by the 23 National Research Ethics Service [references 09/H0504/104+5 and 09/H0707/69] or Medical Ethical Committee of Maastricht University.

Risk predictors in a Spanish cohort with cardiac laminopathies. The REDLAMINA registry

Introduction and objectivesAccording to sudden cardiac death guidelines, an implantable cardioverter-defibrillator (ICD) should be considered in patients with LMNA-related dilated cardiomyopathy (DCM) and ≥ 2 risk factors: male sex, left ventricular ejection fraction (LVEF) <45%, nonsustained ventricular tachycardia (NSVT), and nonmissense genetic variants. In this study we aimed to describe the clinical characteristics of carriers of LMNA genetic variants among individuals from a Spanish cardiac-laminopathies cohort (REDLAMINA registry) and to assess previously reported risk criteria. MethodsThe relationship between risk factors and cardiovascular events was evaluated in a cohort of 140 carriers (age ≥ 16 years) of pathogenic LMNA variants (54 probands, 86 relatives). We considered: a) major arrhythmic events (MAE) if there was appropriate ICD discharge or sudden cardiac death; b) heart failure death if there was heart transplant or death due to heart failure. ResultsWe identified 11 novel and 21 previously reported LMNA-related DCM variants. LVEF <45% (P=.001) and NSVT (P <.001) were related to MAE, but not sex or type of genetic variant. The only factor independently related to heart failure death was LVEF <45% (P <.001). ConclusionsIn the REDLAMINA registry cohort, the only predictors independently associated with MAE were NSVT and LVEF <45%. Therefore, female carriers of missense variants with either NSVT or LVEF <45% should not be considered a low-risk group. It is important to individualize risk stratification in carriers of LMNA missense variants, because not all have the same prognosis.

Predictores de riesgo en una cohorte española con cardiolaminopatías. Registro REDLAMINA

Introduction and objectivesAccording to sudden cardiac death guidelines, an implantable cardioverter-defibrillator (ICD) should be considered in patients with LMNA-related dilated cardiomyopathy (DCM) and ≥ 2 risk factors: male sex, left ventricular ejection fraction (LVEF) <45%, nonsustained ventricular tachycardia (NSVT), and nonmissense genetic variants. In this study we aimed to describe the clinical characteristics of carriers of LMNA genetic variants among individuals from a Spanish cardiac-laminopathies cohort (REDLAMINA registry) and to assess previously reported risk criteria. MethodsThe relationship between risk factors and cardiovascular events was evaluated in a cohort of 140 carriers (age ≥ 16 years) of pathogenic LMNA variants (54 probands, 86 relatives). We considered: a) major arrhythmic events (MAE) if there was appropriate ICD discharge or sudden cardiac death; b) heart failure death if there was heart transplant or death due to heart failure. ResultsWe identified 11 novel and 21 previously reported LMNA-related DCM variants. LVEF <45% (P=.001) and NSVT (P <.001) were related to MAE, but not sex or type of genetic variant. The only factor independently related to heart failure death was LVEF <45% (P <.001). ConclusionsIn the REDLAMINA registry cohort, the only predictors independently associated with MAE were NSVT and LVEF <45%. Therefore, female carriers of missense variants with either NSVT or LVEF <45% should not be considered a low-risk group. It is important to individualize risk stratification in carriers of LMNA missense variants, because not all have the same prognosisFull English text available from:www.revespcardiol.org/en

RARE LOSS-OF-FUNCTION VARIANT ANALYSIS IN LONE ATRIAL FIBRILLATION

Atrial fibrillation (AF) is a complex heritable disorder that substantially increases the risk for stroke, sudden death and all-cause mortality. Lone AF is a subset defined by early diagnosis (less than 60 years) and with no evidence of cardiopulmonary disease. Genome-wide association studies have associated loci near genes for structural integrity and function of muscles with AF susceptibility. In addition, some studies have identified rare loss-of-function (LoF) variants in dilated cardiomyopathy (DCM) genes in lone AF. The increased burden of these variants in lone AF patients may indicate a shared predisposition between AF and DCM. We performed a retrospective study on 252 adult patients and a control group of 503 healthy European subjects. Exome sequencing and microarray assays were performed at the McGill Genome Center while exome data from the controls was retrieved from 1KG Consortium. Principal component analysis was performed to define a group with common ancestry using SVS software. Variants within candidate DCM genes were filtered by minor allele frequency of ≤0.1%, a Combined Annotation Dependent Depletion (CADD) Phred score of >20 and a LoF variant type (frameshift, splice acceptor, splice donor and stop gain). These factors were retrieved from public annotation databases and applied using VarSeq software for variant analysis. All variants were confirmed with Sanger sequencing. Cascade screening was attempted on all cases positive for variants. The AF cohort, an ethnically homogenous composite of 181 lone AF cases, had 6 heterozygous LoF variants, including 4 novel variants, in 6 individuals, while the controls had 4 in 503 individuals. Half of variants in the cases were in the TTN gene (3/6). The prevalence of rare LoF variants in the lone AF cohort was 3.3% while in the control cohort 0.79%, the odds ratio of rare LoF variants found in lone AF patients compared to controls is 4.28 (95%CI: 1.19-15.33, P-value: 2.5E-02). Cascade screening in one family demonstrated co-segregation of one of the rare TTN variants and AF. Patients with lone AF carry a significant burden of heterozygous LoF variants in DCM genes. Our results are in agreement with a previous study identifying TTN variants in lone AF patients. Further, we identified novel variants in different DCM genes and confirmed the co-segregation of a TTN variant and AF in one family. Our findings may indicate a common genetic predisposition between lone AF and DCM, which may help elucidate novel pathophysiologic mechanisms, and improve diagnosis and treatment.

P337Natural history, reversibility and arrhythmias associated with truncating titin variants in dilated cardiomyopathy

Abstract Background Truncating genetic variants in titin (TTNtv) are identified in 15–25% of patients with primary dilated cardiomyopathy (DCM). Previous genotype/phenotype studies have reported conflicting results regarding disease severity and pathologic features associated with TTNtv. Purpose To investigate the natural history, reversibility and burden of arrhythmias associated with TTNtv in a Danish cohort with long-term follow-up. Methods Patients with DCM, recruited from two Danish tertiary centers, were included based on the presence of a TTNtv in a cardiac expressed titin exon. Data on patients' medical history including symptoms, demography, family history, comorbidities, treatment, ECG features, and echocardiograms were registered. Outcome data including all-cause mortality, need of heart transplantation (HTX) or left ventricular assist device (LVAD), and presence of ventricular and supraventricular arrhythmias were registered. Left ventricular reverse remodeling (LVRR) was defined as an absolute increase in left ventricular ejection fraction (LVEF) ≥10% points or normalization. Results A total of 104 patients (71 men, 69%; 72 probands) with definite TTNtv-DCM were included. The mean age at DCM diagnosis was (mean±SD) 45±13 years (43±13 for men; 49±14 for women, p&lt;0.04) and median follow-up was 8.1 years. The mean LVEF was 28±13% at time of diagnosis (26±12% for men; 30±13% for women, p=0.173). During follow-up, 31 patients (30%; 24 men) died or needed HTX/LVAD. Medical therapy was associated with LVRR in 79% of patients 3.6 years after diagnosis. LVRR was maintained long-term in 64% of patients. Women had a better response to medical therapy compared to men (mean LVEF increase 19%; vs 15% in men, p&lt;0.04). Atrial fibrillation/flutter was observed in 40% of patients and ventricular arrhythmias in 23% of patients. Men had an earlier occurrence of both supraventricular and ventricular arrhythmias (p=0.005) with half of the men having experienced an arrhythmia at the age of 54 years. Freedom from arrhythmias with age Conclusion TTNtv leads to a DCM phenotype associated with a marked gender-difference in age at DCM diagnosis and high burden of both supraventricular and ventricular arrhythmias. Importantly, the DCM-TTNtv phenotype was associated with a high degree of reversibility of systolic function following medical therapy.

A gene-centric strategy for identifying disease-causing rare variants in dilated cardiomyopathy

PurposeWe evaluated strategies for identifying disease-causing variants in genetic testing for dilated cardiomyopathy (DCM). MethodsCardiomyopathy gene panel testing was performed in 532 DCM patients and 527 healthy control subjects. Rare variants in 41 genes were stratified using variant-level and gene-level characteristics. ResultsA majority of DCM cases and controls carried rare protein-altering cardiomyopathy gene variants. Variant-level characteristics alone had limited discriminative value. Differentiation between groups was substantially improved by addition of gene-level information that incorporated ranking of genes based on literature evidence for disease association. The odds of DCM were increased to nearly 9-fold for truncating variants or high-impact missense variants in the subset of 14 genes that had the strongest biological links to DCM (P <0.0001). For some of these genes, DCM-associated variants appeared to be clustered in key protein functional domains. Multiple rare variants were present in many family probands, however, there was generally only one “driver” pathogenic variant that cosegregated with disease. ConclusionRare variants in cardiomyopathy genes can be effectively stratified by combining variant-level and gene-level information. Prioritization of genes based on their a priori likelihood of disease causation is a key factor in identifying clinically actionable variants in cardiac genetic testing.

Variants in NKX2-5 and FLNC Cause Dilated Cardiomyopathy and Sudden Cardiac Death.

Dilated cardiomyopathy (DCM) is an important cause of heart failure. Variants in >50 genes have been reported to cause DCM, but causative variants have been found in less than half of familial cases. Variants causing DCM in Iceland have not been reported before. We performed a genome-wide association study on DCM based on whole genome sequencing. We tested the association of 32.5 million sequence variants in 424 cases and 337 689 population controls in Iceland. We identified 2 DCM variants in established cardiomyopathy genes, a missense variant p.Phe145Leu in NKX2-5 carried by 1 in 7100 Icelanders ( P=7.0×10-12) and a frameshift variant p.Phe1626Serfs*40 in FLNC carried by 1 in 3600 Icelanders ( P=2.1×10-10). Both variants associate with heart failure and sudden cardiac death. Additionally, p.Phe145Leu in NKX2-5 associates with high degree atrioventricular block and atrial septal defect ( P<1.4×10-4). The penetrance of serious heart disease among carriers of the NKX2-5 variant is high and higher than that of the FLNC variant. Two rare variants in NKX2-5 and FLNC, carried by 1 in 2400 Icelanders, cause familial DCM in Iceland. These genes have recently been associated with DCM. Given the serious consequences of these variants, we suggest screening for them in individuals with DCM and their family members, with subsequent monitoring of carriers, offering early intervention.

Multigenic Disease and Bilineal Inheritance in Dilated Cardiomyopathy Is Illustrated in Nonsegregating LMNA Pedigrees.

We have previously described 19 pedigrees with apparent lamin (LMNA)-related dilated cardiomyopathy (DCM) manifesting in affected family members across multiple generations. In 6 of 19 families, at least 1 individual with idiopathic DCM did not carry the family's LMNA variant. We hypothesized that additional genetic cause may underlie DCM in these families. Affected family members underwent exome sequencing to identify additional genetic cause of DCM in the 6 families with nonsegregating LMNA variants. In 5 of 6 pedigrees, we identified at least 1 additional rare variant in a known DCM gene that could plausibly contribute to disease in the LMNA variant-negative individuals. Bilineal inheritance was clear or presumed to be present in 3 of 5 families and was possible in the remaining 2. At least 1 individual with a LMNA variant also carried a variant in an additional identified DCM gene in each family. Using a multivariate linear mixed model for quantitative traits, we demonstrated that the presence of these additional variants was associated with a more severe phenotype after adjusting for sex, age, and the presence/absence of the family's nonsegregating LMNA variant. Our data support DCM as a genetically heterogeneous disease with, at times, multigene causation. Although the frequency of DCM resulting from multigenic cause is uncertain, our data suggest it may be higher than previously anticipated.

Filamin C Truncation Mutations Are Associated With Arrhythmogenic DilatedCardiomyopathy and Changes inthe Cell-Cell Adhesion Structures.

OBJECTIVESThe purpose of this study was to assess the phenotype of Filamin C (FLNC) truncating variants in dilated cardiomyopathy (DCM) and understand the mechanism leading to an arrhythmogenic phenotype.BACKGROUNDMutations in FLNC are known to lead to skeletal myopathies, which may have an associated cardiac component. Recently, the clinical spectrum of FLNC mutations has been recognized to include a cardiac-restricted presentation in the absence of skeletal muscle involvement.METHODSA population of 319 U.S. and European DCM cardiomyopathy families was evaluated using whole-exome and targeted next-generation sequencing. FLNC truncation probands were identified and evaluated by clinical examination, histology, transmission electron microscopy, and immunohistochemistry.RESULTSA total of 13 individuals in 7 families (2.2%) were found to harbor 6 different FLNC truncation variants (2 stopgain, 1 frameshift, and 3 splicing). Of the 13 FLNC truncation carriers, 11 (85%) had either ventricular arrhythmias or sudden cardiac death, and 5 (38%) presented with evidence of right ventricular dilation. Pathology analysis of 2 explanted hearts from affected FLNC truncation carriers showed interstitial fibrosis in the right ventricle and epicardial fibrofatty infiltration in the left ventricle. Ultrastructural findings included occasional disarray of Z-discs within the sarcomere. Immunohistochemistry showed normal plakoglobin signal at cell–cell junctions, but decreased signals for desmoplakin and synapse-associated protein 97 in the myocardium and buccal mucosa.CONCLUSIONSWe found FLNC truncating variants, present in 2.2% of DCM families, to be associated with a cardiac-restricted arrhythmogenic DCM phenotype characterized by a high risk of life-threatening ventricular arrhythmias and a pathological cellular phenotype partially overlapping with arrhythmogenic right ventricular cardiomyopathy.

Genomic structural variations lead to dysregulation of important coding and non-coding RNA species in dilated cardiomyopathy.

The transcriptome needs to be tightly regulated by mechanisms that include transcription factors, enhancers, and repressors as well as non‐coding RNAs. Besides this dynamic regulation, a large part of phenotypic variability of eukaryotes is expressed through changes in gene transcription caused by genetic variation. In this study, we evaluate genome‐wide structural genomic variants (SVs) and their association with gene expression in the human heart. We detected 3,898 individual SVs affecting all classes of gene transcripts (e.g., mRNA, miRNA, lncRNA) and regulatory genomic regions (e.g., enhancer or TFBS). In a cohort of patients (n = 50) with dilated cardiomyopathy (DCM), 80,635 non‐protein‐coding elements of the genome are deleted or duplicated by SVs, containing 3,758 long non‐coding RNAs and 1,756 protein‐coding transcripts. 65.3% of the SV‐eQTLs do not harbor a significant SNV‐eQTL, and for the regions with both classes of association, we find similar effect sizes. In case of deleted protein‐coding exons, we find downregulation of the associated transcripts, duplication events, however, do not show significant changes over all events. In summary, we are first to describe the genomic variability associated with SVs in heart failure due to DCM and dissect their impact on the transcriptome. Overall, SVs explain up to 7.5% of the variation of cardiac gene expression, underlining the importance to study human myocardial gene expression in the context of the individual genome. This has immediate implications for studies on basic mechanisms of cardiac maladaptation, biomarkers, and (gene) therapeutic studies alike.