Dilated Cardiomyopathy Families Research Articles

An alpha-helix variant p.Arg156Pro in LMNA as a cause of hereditary dilated cardiomyopathy: genetics and bioinfomatics exploration

LMNA gene encodes lamin A/C protein which participates in the construction of nuclear lamina, the mutations of LMNA result in a wide variety of diseases known as laminopathies. LMNA-related dilated cardiomyopathy(LMNA-DCM) is one of the more common laminopathy which characterized by progressive heart failure and arrhythmia. However, the mutation features of LMNA-DCM are yet to be elucidated. Herein we described a dilated cardiomyopathy family carrying novel variant c.467G > C(p.Arg156Pro) of LMNA as heterozygous pathogenic variant identified by whole-exome sequencing. With the help of Alphafold2, we predicted mutant protein structure and found an interrupted α-helix region in lamin A/C. In the analysis of 49 confirmed pathogenic missense of laminopathies, Chi-square test showed the DCM phenotype was related to the α-helix region mutation (p < 0.017). After screening the differentially expressed genes (DEGs) in both mice models and human patients in Gene Expression Omnibus database, we found the variation of α-helix-coding region in LMNA caused abnormal transcriptomic features in cell migration, collagen-containing extracellular matrix, and PI3K-Akt signaling pathway. Subsequently we constructed (TF)-mRNA-microRNA (miRNA) regulatory network and identified 7 key genes (FMOD, CYP1B1, CA3, F2RL1, HAPLIN1, SNAP91, and KANSL1) as potential biomarkers or therapeutic targets in LMNA-DCM patients.

Genotype Complements the Phenotype: Identification of the Pathogenicity of an LMNA Splice Variant by Nanopore Long-Read Sequencing in a Large DCM Family.

Dilated cardiomyopathy (DCM) is a common cause of heart failure (HF) and is of familial origin in 20–40% of cases. Genetic testing by next-generation sequencing (NGS) has yielded a definite diagnosis in many cases; however, some remain elusive. In this study, we used a combination of NGS, human-induced pluripotent-stem-cell-derived cardiomyocytes (iPSC-CMs) and nanopore long-read sequencing to identify the causal variant in a multi-generational pedigree of DCM. A four-generation family with familial DCM was investigated. Next-generation sequencing (NGS) was performed on 22 family members. Skin biopsies from two affected family members were used to generate iPSCs, which were then differentiated into iPSC-CMs. Short-read RNA sequencing was used for the evaluation of the target gene expression, and long-read RNA nanopore sequencing was used to evaluate the relevance of the splice variants. The pedigree suggested a highly penetrant, autosomal dominant mode of inheritance. The phenotype of the family was suggestive of laminopathy, but previous genetic testing using both Sanger and panel sequencing only yielded conflicting evidence for LMNA p.R644C (rs142000963), which was not fully segregated. By re-sequencing four additional affected family members, further non-coding LMNA variants could be detected: rs149339264, rs199686967, rs201379016, and rs794728589. To explore the roles of these variants, iPSC-CMs were generated. RNA sequencing showed the LMNA expression levels to be significantly lower in the iPSC-CMs of the LMNA variant carriers. We demonstrated a dysregulated sarcomeric structure and altered calcium homeostasis in the iPSC-CMs of the LMNA variant carriers. Using targeted nanopore long-read sequencing, we revealed the biological significance of the variant c.356+1G>A, which generates a novel 5′ splice site in exon 1 of the cardiac isomer of LMNA, causing a nonsense mRNA product with almost complete RNA decay and haploinsufficiency. Using novel molecular analysis and nanopore technology, we demonstrated the pathogenesis of the rs794728589 (c.356+1G>A) splice variant in LMNA. This study highlights the importance of precise diagnostics in the clinical management and workup of cardiomyopathies.

Aberrant interaction between TEAD1 and Lamin A/C causes cardiomyopathy

Abstract Background Mutations in the LMNA gene encoding Lamin A/C, a major component of the nuclear lamina, cause laminopathies including dilated cardiomyopathy (DCM). DCM patients with LMNA mutations have particularly severe clinical courses such as heart transplantation and death due to heart failure. However, underlying mechanisms of LMNA-induced DCM remains elusive. Methods and results We identified LMNA Q353R mutation in a DCM family with severe heart failure. We generated Q353R heterozygous knock-in mice, which showed sarcomere dysplasia and perinatal lethality. Integrative single-cell analyses of the fetal murine hearts and patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSCMs) revealed that transcriptional regulation of cardiomyocyte maturation/development genes governed by TEAD1 was impaired in LMNA mutant cardiomyocytes. Protein array and immunostaining uncovered increased binding of TEAD1 to mutant Lamin A/C protein and abnormal localization of TEAD1 at the nuclear periphery. Furthermore, TT-10, a Hippo pathway inhibitor, rescued the dysregulation of cardiac developmental genes in LMNA mutant cardiomyocytes. Single-cell RNA-seq of cardiac tissues from DCM patients with the LMNA Q353R mutation confirmed the dysregulated expression of TEAD1 and its target genes. These results demonstrated abnormal interaction between TEAD1 and mutant Lamin A/C impairs structural maturation of cardiomyocytes and suggests that LMNA Q353R-related DCM can be treated through intervention in the Hippo pathway. Conclusion TEAD1 trapped by mutant Lamin A/C protein at the nuclear membrane perturbs transcriptional maturation in LMNA Q353R-related DCM. Funding Acknowledgement Type of funding sources: None.

Communal Coping as a Strategy to Enhance Family Engagement in Dilated Cardiomyopathy.

Assuring that relatives are informed about a genetic diagnosis and have appropriate medical follow-up can be challenging. We hypothesize that communal coping (CC)-an approach in which a group views a stressor (such as a new genetic diagnosis) as our problem, versus my or your problem, and takes joint action to address it-can help families to address this challenge. A better understanding of CC could also inform counseling interventions to promote CC and family follow-up. In the Dilated Cardiomyopathy (DCM) PM study (Precision Medicine), living first-degree relatives of DCM probands were invited to undergo clinical screening; 31% of these did so. This research program offers the opportunity to determine the frequency of CC in DCM families, assess whether CC attitudes and actions occurred more commonly among families in which family members participated, and conduct prospective follow-up to evaluate family coping and counseling needs over time. The proposed studies will provide evidence about the frequency of CC attitudes and actions among DCM families, assess the association of CC with increased family follow-up, and identify counseling needs related to family follow-up. The DCM PM study offers an opportunity to test the hypothesis that CC contributes to increased family follow-up and generate evidence to inform counseling interventions to encourage such follow-up.

A novel deletion mutation accompanied by a point mutation in Lamin A/C gene: Screened from a dilated cardiomyopathy family.

There are 30%-40% of patients with dilated cardiomyopathy (DCM) having genetic causes, among which Lamin A and C gene (LMNA) mutation is the second most frequent DCM-related mutation, and Lamin A/C may be involved in the pathogenesis of DCM through the regulation of gene transcription or the direct effect of cell structure. Methods: Echocardiography and electrocardiogram were used to diagnose DCM and arrhythmia in a DCM family. Then, linked mutations on LMNA were screened out by high-throughput sequencing and verified by Sanger sequencing in all research individuals. Meanwhile, Human Genome Variation Society (HGVS) and Integrative Genomics Viewer (IGV) were used to analyse the characteristics of the mutated Lamin A/C protein. Finally, mutated-type and wild-type LMNA plasmid was transfected into AC-16 cardiomyocytes with the form of a lentivirus vector, and its effect on nucleus and actin was studied by immunofluorescence detection. In this study, we found a new frame-shifted mutation of LMNA (p.Ser414Alafs*66) linked with another point mutation from a DCM family by using High-throughput sequencing, and this deletion mutation led to a truncation of Lamin A/C. By analysing the clinical characteristics of this DCM family, we found that all DCM patients with arrhythmia were carriers of this co-segregation mutation. In the cytological experiment, we found that the mutated-type transfections showed weaker fluorescent intensities on both actin and cell nucleus. A co-segregation mutation of LMNA (Point mutation chr1 156107548 c.1712 G>A and truncated frame-shifted mutation chr1 156106086 c.1240delA) was found from a DCM family, and this type of mutation could participate in the pathogenesis of DCM by affecting the expression of actin.

Abstract 12946: Identification of a LMNA Synonymous Variant Associated With Severe Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the most common cardiac phenotypes caused by mutations of lamin A/C (LMNA) gene in humans. Almost 50% of LMNA variants reported in ClinVar as pathogenic or likely pathogenic are due to frameshift, nonsense, or splicing variants, predictive of haploinsufficiency for LMNA protein. In contrast, synonymous variants that do not immediately suggest a haploinsufficiency mechanism are much harder to interpret. We evaluated a cohort of 57 patients who underwent heart transplant for dilated cardiomyopathy for LMNA variants and identified a novel synonymous variant c.936G&gt;A in the last nucleotide of exon 5 of LMNA in a DCM family. Clinically, LMNA c.936G&gt;A carriers presented with severe DCM, conduction disease and high creatine-kinase levels. Sanger sequencing showed the presence of LMNA c.936G&gt;A in the genomic DNA but not in the cDNA derived from one family member’s heart tissue. RT-PCR using RNA from the patient’s heart tissue was performed with primers that amplified LMNA exons 4-6. DNA fragments amplified by RT-PCR were then cloned into pcDNAII vector and 40 clones were picked and sequenced. An aberrantly spliced mRNA containing the variant and a premature stop codon was identified in 1 of the 40 clones. Real-time quantitative PCR showed significantly lower LMNA mRNA levels in the patient’s heart compared to the controls. Our findings suggest that the c.936G&gt;A LMNA variant resulted in aberrant RNA splicing, which possibly triggers nonsense-mediated RNA decay, leading to reduced mRNA and likely protein expression. These results expand the understanding on the association between synonymous LMNA variants and the molecular pathogenesis of LMNA-DCM.

Clinical Features of LMNA-Related Cardiomyopathy in 18 Patients and Characterization of Two Novel Variants.

Dilated cardiomyopathy (DCM) refers to a spectrum of heterogeneous myocardial disorders characterized by ventricular dilation and depressed myocardial performance in the absence of hypertension, valvular, congenital, or ischemic heart disease. Mutations in LMNA gene, encoding for lamin A/C, account for 10% of familial DCM. LMNA-related cardiomyopathies are characterized by heterogeneous clinical manifestations that vary from a predominantly structural heart disease, mainly mild-to-moderate left ventricular (LV) dilatation associated or not with conduction system abnormalities, to highly pro-arrhythmic profiles where sudden cardiac death (SCD) occurs as the first manifestation of disease in an apparently normal heart. In the present study, we select, among 77 DCM families referred to our center for genetic counselling and molecular screening, 15 patient heterozygotes for LMNA variants. Segregation analysis in the relatives evidences other eight heterozygous patients. A genotype–phenotype correlation has been performed for symptomatic subjects. Lastly, we perform in vitro functional characterization of two novel LMNA variants using dermal fibroblasts obtained from three heterozygous patients, evidencing significant differences in terms of lamin expression and nuclear morphology. Due to the high risk of SCD that characterizes patients with lamin A/C cardiomyopathy, genetic testing for LMNA gene variants is highly recommended when there is suspicion of laminopathy.

585 Pregnancy Outcomes in Women With Dilated Cardiomyopathy Gene Variants: A Retrospective Cohort Study

To assess the pregnancy outcomes and experiences in a cohort of dilated cardiomyopathy (DCM) variant carriers DCM families were referred to the Royal Melbourne Hospital cardiac genetics clinic 2009-2019. Among families where a disease gene was identified, female carriers with at least one previous pregnancy were invited to take part. Participants underwent a clinical interview and comprehensive file review to qualitatively describe pregnancy outcomes including symptoms, pregnancy complications and adverse cardiovascular events. Twenty-seven women consented to take part, 5 probands and 22 relatives. Thirteen participants (48%) had DCM at time of assessment, five were diagnosed on family screening. Three participants (11%) were diagnosed with DCM during or shortly after pregnancy: one died of complications post intrapartum cardiac arrest, one had a stroke post-partum and was found to have cardiomyopathy, one had family screening at 34 weeks with an ejection fraction of 36% and clinical heart failure. Ten participants (37%) were diagnosed with DCM after pregnancy (range 2-35 years, median 13.5 years). Of these, only one recollected symptoms of heart failure during pregnancy. There were fourteen unaffected carriers and only one reported symptoms of increasing palpitations during pregnancy. Four participants have had pregnancies since their genetic diagnosis, one with DCM and three carriers. All have had close cardiological antenatal monitoring with no adverse events. Of the thirteen participants with DCM, three (23%) were diagnosed during or shortly after pregnancy with significant associated morbidity and mortality. This highlights the potential role for pregnancy in unmasking genetic cardiomyopathy.

Mutations in ILK, encoding integrin-linked kinase, are associated with arrhythmogenic cardiomyopathy

Arrhythmogenic cardiomyopathy is a genetic heart muscle disorder characterized by fibro-fatty replacement of cardiomyocytes leading to life-threatening ventricular arrhythmias, heart failure, and sudden cardiac death. Mutations in genes encoding cardiac junctional proteins are known to cause about half of cases, while remaining genetic causes are unknown. Using exome sequencing, we identified 2 missense variants (p.H33N and p.H77Y) that were predicted to be damaging in the integrin-linked kinase (ILK) gene in 2 unrelated families. The p.H33N variant was found to be de novo. ILK links integrins and the actin cytoskeleton, and is essential for the maintenance of normal cardiac function. Both of the new variants are located in the ILK ankyrin repeat domain, which binds to the first LIM domain of the adaptor proteins PINCH1 and PINCH2. In silico binding studies proposed that the human variants disrupt the ILK-PINCH complex. Recombinant mutant ILK expressed in H9c2 rat myoblast cells shows aberrant prominent cytoplasmic localization compared to the wild-type. Expression of human wild-type and mutant ILK under the control of the cardiac-specific cmlc2 promotor in zebrafish shows that p.H77Y and p.P70L, a variant previously reported in a dilated cardiomyopathy family, cause cardiac dysfunction and death by about 2-3 weeks of age. Our findings provide genetic and functional evidence that ILK is a cardiomyopathy disease gene and highlight its relevance for diagnosis and genetic counseling of inherited cardiomyopathies.

Penetrance of Dilated Cardiomyopathy in Families with Truncating TTN Variants: a National Perspective

Truncating variants in the TTN gene (TTNtv) are common in dilated cardiomyopathy (DCM) patients (15–20% cases) but are also present in unaffected individuals in DCM families and in the general population. Interpreting the clinical significance of these variants is challenging. Our aim was to determine DCM penetrance in a large cohort of kindreds with TTNtv-related familial DCM that were identified by a network of investigators in the Australian Genomics Cardiac Flagship. Eligible families were required to carry a high-impact TTNtv, with genetic testing offered in an unbiased way to affected and unaffected relatives. Probands from 65 families were identified from 8 clinical genetic testing or research services. 457 individuals were genotyped (mean age 52 years, range 13 to 93; 51% males). There were no differences in the relative distribution of TTNtv positive (n = 228, 50%) and TTNtv negative (n = 229, 50%) individuals, or in the numbers of male (n = 234, 51%) and female (n = 223, 49%) participants. The median age of DCM onset in TTNtv carriers was 51 years with DCM penetrance increasing from 34% at 40 years to 93% at 80 years. Male TTNtv carriers had a higher DCM penetrance (p < 0.0001; 59% vs 33% at 50 years) and lower median age of onset (45 vs 55 years) compared to females. Our data show that the overall penetrance of DCM in TTNtv carriers is high, but that a substantial proportion of relatives, particularly females, can remain asymptomatic until late in life. These findings have implications for screening surveillance and genetic counselling of asymptomatic TTNtv carriers.

A-Band Titin Truncation in Zebrafish Causes Dilated Cardiomyopathy and Hemodynamic Stress Intolerance

Background Truncating variants in the TTN gene ( TTNtv) are common in patients with dilated cardiomyopathy (DCM) but also occur in the general population. Whether TTNtv are sufficient to cause DCM or require a second hit for DCM manifestation is an important clinical issue. Methods We generated a zebrafish model of an A-band TTNtv identified in 2 human DCM families in which early-onset disease appeared to be precipitated by ventricular volume overload. Cardiac phenotypes were serially assessed from 0 to 12 months using video microscopy, high-frequency echocardiography, and histopathologic analysis. The effects of sustained hemodynamic stress resulting from an anemia-induced hyperdynamic state were also evaluated. Results Homozygous ttna mutants had severe cardiac dysmorphogenesis and premature death, whereas heterozygous mutants ( ttnatv/+) survived into adulthood and spontaneously developed DCM. Six-month-old ttnatv/+ fish had reduced baseline ventricular systolic function and failed to mount a hypercontractile response when challenged by hemodynamic stress. Pulsed wave and tissue Doppler analysis also revealed unsuspected ventricular diastolic dysfunction in ttnatv/+ fish with prolonged isovolumic relaxation and increased diastolic passive stiffness in the absence of myocardial fibrosis. These defects reduced diastolic reserve under stress conditions and resulted in disproportionately greater atrial dilation than observed in wild-type fish. Conclusions Heterozygosity for A-band titin truncation is sufficient to cause DCM in adult zebrafish. Abnormalities of systolic and diastolic reserve in titin-truncated fish reduce stress tolerance and may contribute to a substrate for atrial arrhythmogenesis. These data suggest that hemodynamic stress may be an important modifiable risk factor in human TTNtv-related DCM.

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.

Exome Sequencing Identifies a Novel DES Mutation (R227C) in a Chinese Dilated Cardiomyopathy Family

Objectives: Dilated cardiomyopathy (DCM) is a common disease in the clinic, and it is the leading cause of heart failure and sudden cardiac death. Previous studies have proven that genetic factors play a crucial role in the occurrence of DCM; more than 50 disease genes including desmin (DES) have been identified to be associated with DCM. At present, most DES mutations are reported in desmin-related myofibrilla myopathy patients, but variants leading to isolated DCM are rarely reported. Methods: We applied whole-exome sequencing and cardiomyopathy-related gene filtering strategies to discover the genetic factors in a Chinese DCM family. Results: A novel mutation (c.679 C>T /p.R227C) in exon 3 of DES was identified and cosegregated with the affected members of a Chinese family with isolated DCM phenotypes (left ventricle and left atrial diameters). Conclusion: This mutation leads to a substitution of arginine by cysteine and it is predicted to be deleterious by bioinformatics programs. Our study not only contributes to the genetic diagnosis and counseling of families with DCM, but it also further proves that DES mutations may lead to isolated DCM and provides a new case for the study of the relationship between DES mutations and DCM.

Whole-Exome Sequencing Identifies Two Novel TTN Mutations in Chinese Families with Dilated Cardiomyopathy

Objectives: Dilated cardiomyopathy (DCM) is a leading cause of sudden cardiac death. So far, only 127 mutations of Titin(TTN) have been reported in patients with different phenotypes such as isolated cardiomyopathies, purely skeletal muscle phenotypes or complex overlapping disorders of muscles. Methods: We applied whole-exome sequencing (WES) to investigate cardiomyopathy patients and a cardiomyopathy-related gene-filtering strategy was used to analyze the disease-causing mutations. Sanger sequencing was applied to confirm the mutation cosegregation in the affected families. Results: A nonsense mutation (c.12325C>T/p.R4109X) and a missense mutation (c.17755G>C/p.G5919R) of TTN were identified in 2 Chinese DCM families, respectively. Both mutations were cosegregated in all affected members of both families. The nonsense mutation is predicted to result in a truncated TTN protein and the missense mutation leads to a substitution of glycine by arginine. Both variants may cause the structure changes of titin protein. Conclusions: We employed WES to detect the mutations of DCM patients and identified 2 novel mutations. Our study expands the spectrum of TTN mutations and offers accurate genetic testing information for DCM patients who are still clinically negative.

11. Gene Therapy Mediated Increase in dATP Improves Cardiac Performance in Models of Systolic Heart Failure

Heart Failure results in more deaths and hospitalizations than almost any other single cause. We are exploring gene therapy treatment strategies that increase 2 deoxy-adenosine triphosphate (dATP) levels via cardiac specific expression of ribonucleotide reductase (RNR) in heart muscle. dATP is produced by RNR. In vitro studies show it increases the magnitude & rate of contraction in rodent, pig & failing human heart muscle without altering calcium handling or slowing relaxation. RNR expression in heart muscle increases intracellular dATP, cardiomyocyte contraction & cardiac performance in rodents. To do this we ligated a cDNA encoding both human RNR subunits to miniaturized cardiac specific enhancer/promoter portions of human cardiac troponin T and packaged the therapeutic “BB-R12” gene in AAV6. In the current study expanded the types of heart failure treated by BB-R12 by testing the effect of dATP on contractile function in a transgenic mouse model of familial dilated cardiomyopathy (DCM). These mice carry and phenocopy a missense mutation (D230N) in alpha-tropomyosin (Tm) that was identified in two DCM family cohorts that exhibit progressive ventricular dilation and loss of systolic function. We measured the effect of dATP on the Ca2+ sensitivity of force in demembranated trabeculae from young adult D230N & WT mice (3 mice & 8-10 trabeculae per group). pCa50 was decreased (lower Ca2+ sensitivity) for D230N Tm (5.47±0.01) compared to WT (5.59±0 0.03) mice, and substituting dATP for ATP rescued this defect (5.55±0.03). dATP also increased isometric force ~20% at pCa=5.8, the approximate level of intracellular Ca2+ seen in a cardiomyocyte twitch. We also measured force and the kinetics of activation & relaxation of isolated myofibrils. Force at pCa=5.6 decreased from 85±14 mN/mm2 in WT myofibrils to 52±7 mN/mm2 (p<0.05) in D230N Tm myofibrils. Importantly, the force deficit was improved to 72±14 mN/mm2 (p=0.47) with dATP. Similarly, the activation rate decreased in D230N Tm myofibrils (1.6±0.2 s-1) vs. WT mice (3.5±0.3 s-1), and this was partially corrected by dATP (2.5±0.4 s-1). dATP also corrected alterations in the early, slow relaxation phase of myofibrils from D230N Tm mice. In ongoing studies, we are systemically injecting 4-6 week old D230N Tm mice with AAV6-BB-R12 to determine how this affects cardiac function acutely, as well as the time course of reduced systolic function, progressive ventricular dilation & wall remodeling. In related studies, we found AAV6-BB-R12 rescues cardiac function in an infarcted pig heart failure model. These studies assess the ability of BB-R12 to acutely treat diseased hearts and act as a preventative agent in progressive heart failure.

A systematic analysis of genetic dilated cardiomyopathy reveals numerous ubiquitously expressed and muscle-specific genes.

Despite considerable progress being made in genetic diagnostics for dilated cardiomyopathy (DCM) using panels of the most prevalent genes, the cause remains unsolved in a substantial percentage of patients. We hypothesize that several previously described DCM genes with low or unknown prevalence have been neglected, which, if catalogued, could increase the yield of diagnostic DCM testing. The aim of this study is to catalogue all genetic evidence on DCM comprehensively. We have conducted a systematic literature search on PubMed, Embase, and OMIM to find genes implicated in syndromic and non-syndromic DCM and peripartum cardiomyopathy (PPCM). Our search yielded 110 nuclear protein-coding genes and 24 mitochondrial DNA genes. For nuclear genes, in addition to 42 genes sufficiently reviewed previously (group A), we provide a comprehensive annotation of the level of genetic evidence for the remaining 68 genes (group B). Next, we investigated the tissue specificity of the collected genes using public RNA sequencing data. We show that genes primarily expressed in heart and skeletal muscle are more likely to result in DCM with possible skeletal myopathies, while genes expressed ubiquitously cause DCM with extramuscular manifestations. This comprehensive analysis of DCM-associated genes revealed a much higher number of genes than currently screened in diagnostics. Since most genes in group B have only been found mutated in single DCM patients or families, their importance for DCM genetic diagnostics needs to be validated in large cohorts. Targeted sequencing of validated DCM-implicated protein-coding genes and mitochondrial DNA, together with consideration of the tissue specificity of mutated genes, may facilitate further genotype-phenotype studies in DCM.

Abstract 13585: Up Regulation of Autophagy in Hsp60 Mutant Heart is an Adaptive Response to Increased Oxidative Stress and Causes Cardiomyopathy

Introduction: Despite the recent advance of genetic studies, genetic causes of hereditary dilated cardiomyopathy (DCM) are still unknown in most cases. Heat shock protein 60 (Hsp60) is a well-known chaperonin, responsible for correct folding and transportation of cytoplasmic protein to mitochondria. This study is aimed to investigate whether dysfunction of Hsp60 leads to cardiomyopathy in a fish model. Methods: We previously developed a zebrafish mutant, nbl, which has a missense mutation in hsp60, leading to the loss of function. To evaluate the phenotype of cardiomyopathy in nbl, we performed RT-PCR, western blot and immunohistochemistry of the hearts. Results: Homozygous nbl embryos showed lower survival rate (65%), compared to 81% in wild-type (WT) embryos, when subjected to 33°C (stress condition). We observed pericardial edema in 92% of nbl homozygous mutants. Also, nbl homozygotes showed sudden death at around 8 months post fertilization (mpf), when grown in non-stress condition. At 8 mpf, nbl mutants showed dilated heart and high expression of reactive oxygen species (ROS). Both mRNA and protein levels of Hsp60 were similar in nbl homozygotes and WT, at 3 mpf but, much higher expression of Hsp60 in nbl homozygotes was observed at 6 mpf, beginning of death of nbl homozygous mutants. Electron microscopy analysis showed dark mitochondria, disrupted sarcomeric structure and higher number of autophagosomes in nbl homozygote hearts at 8 mpf. We, then, analyzed autophagy related genes and found that atg5, atg3 and gabarap mRNAs were increased in nbl homozygotes, suggesting the increased autophagy might underlie the pathogenesis of DCM. Furthermore, analysis of genetically unrelated patients with familial DCM, who had no mutations in the known DCM-causing genes, identified an hsp60 mutation in one DCM family in which two of four mutation prone individuals died suddenly. Over expression of nbl mutation or DCM-associated hsp60 mutation, but not normal hsp60, increased autophagosomes in Hela cells carrying GFP-LC3. Conclusions: Functional loss of Hsp60 increased oxidative stress in the heart, which leads to increased autophagy and confer the susceptibility to cardiomyopathy.

Whole exome sequencing identifies a novel EMD mutation in a Chinese family with dilated cardiomyopathy.

BackgroundVariants in the emerin gene (EMD) were implicated in X-linked recessive Emery-Dreifuss muscular dystrophy (EDMD), characterized by early-onset contractures of tendons, progressive muscular weakness and cardiomyopathy. To date, 223 mutations have been reported in EMD gene and the majority of them caused a predominant skeletal muscular phenotype. In this study, we identified a novel deletion mutation in EMD exon 1, which results in almost a complete loss of emerin protein in a large Chinese family. However, the patients suffered severe dilated cardiomyopathy (DCM) but very mild skeletal muscle disorder.Case presentationWhole exome sequencing (WES) and linkage analysis were performed to identify the underlying mutation in a Chinese DCM family spanning five generations. A missense variation in the GPR50 gene was found co-segregated with the disease phenotype, whereas no functional alteration was detected in the variant GPR50 protein. When analyzing the failure sequences in the exome sequencing data, a novel deletion mutation (c.26_39delATACCGAGCTGACC) in EMD exon 1, was identified in this family. Different from the typical clinical features caused by most reported EMD mutations, patients in our study presented very mild skeletal muscle degeneration that had not been diagnosed until the mutation was found.ConclusionWe described a family with rare clinical presentations caused by a novel EMD deletion mutation. Our findings broaden the heterogeneous spectrum of phenotypes attributed to EMD mutations and provide new insight to explain the genotype-phenotype correlations between EMD mutations and EDMD symptoms.

Potential genetic predisposition for anthracycline-associated cardiomyopathy in families with dilated cardiomyopathy

ObjectiveAnthracyclines are successfully used in cancer treatment, but their use is limited by their cardiotoxic side effects. Several risk factors for anthracycline-associated cardiomyopathy (AACM) are known, yet the occurrence of...

Whole Exome Sequencing Identifies a Troponin T Mutation Hot Spot in Familial Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) commonly causes heart failure and shows extensive genetic heterogeneity that may be amenable to newly developed next-generation DNA sequencing of the exome. In this study we report the successful use of exome sequencing to identify a pathogenic variant in the TNNT2 gene using segregation analysis in a large DCM family. Exome sequencing was performed on three distant relatives from a large family with a clear DCM phenotype. Missense, nonsense, and splice variants were analyzed for segregation among the three affected family members and confirmed in other relatives by direct sequencing. A c.517T C>T, Arg173Trp TNNT2 variant segregated with all affected family members and was also detected in one additional DCM family in our registry. The inclusion of segregation analysis using distant family members markedly improved the bioinformatics filtering process by removing from consideration variants that were not shared by all affected subjects. Haplotype analysis confirmed that the variant found in both DCM families was located on two distinct haplotypes, supporting the notion of independent mutational events in each family. In conclusion, an exome sequencing strategy that includes segregation analysis using distant affected relatives within a family represents a viable diagnostic strategy in a genetically heterogeneous disease like DCM.