Genetic basis of dilated cardiomyopathy

SnRNA-seq reveals differential functional transcriptional pathway alterations in three mutant types of dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a leading cause of heart failure, characterized by ventricular dilation, thinning of the ventricular walls, and systolic dysfunction in either the left or both ventricles, often accompanied by fibrosis. Human cardiac tissue is composed of various cell types, including cardiomyocytes (CMs), fibroblasts (FBs), endothelial cells (ECs), macrophages, lymphocytes and so on. In DCM patients, these cells frequently undergo functional and phenotypic changes, contributing to contractile dysfunction, inflammation, fibrosis, and cell death, thereby increasing the risk of heart failure. This study focuses on DCM patients with mutations (LMNA, RBM20, and TTN) and analyzes functional changes in subpopulations of four cardiac cell types. The study involves functional annotation of subpopulations within each cell type and explores the association between gene mutations and specific functions and pathways. Additionally, the SCENIC method is employed of a particular cell subpopulation with significant functional importance, aiming to identify key transcriptional regulators in specific cell states. By analyzing the expression levels of ligand-receptor pairs in vCM4, vFB2, EC5.0, T cells, and NK cells across the DCM mutant genotypes, we predicted their signaling pathways and communications. This research provides insights into the molecular mechanisms of DCM and potential therapeutic targets.

The effects of sodium-glucose cotransporter 2 inhibitors on the 'forgotten' right ventricle

With the progress in diagnosis, treatment and imaging techniques, there is a growing recognition that impaired right ventricular (RV) function profoundly affects the prognosis of patients with heart failure (HF), irrespective of their left ventricular ejection fraction (LVEF). In addition, right HF (RHF) is a common complication associated with various diseases, including congenital heart disease, myocardial infarction (MI), pulmonary arterial hypertension (PAH) and dilated cardiomyopathy (DCM), and it can manifest at any time after left ventricular assist devices (LVADs). The sodium-glucose cotransporter 2 (SGLT2) inhibition by gliflozins has emerged as a cornerstone medicine for managing type 2 diabetes mellitus (T2DM) and HF, with an increasing focus on its potential to enhance RV function. In this review, we aim to present an updated perspective on the pleiotropic effects of gliflozins on the right ventricle and offer insights into the underlying mechanisms. We can ascertain their advantageous impact on the right ventricle by discussing the evidence obtained in animal models and monumental clinical trials. In light of the pathophysiological changes in RHF, we attempt to elucidate crucial mechanisms regarding their beneficial effects, including alleviation of RV overload, reduction of hyperinsulinaemia and inflammatory responses, regulation of nutrient signalling pathways and cellular energy metabolism, inhibition of oxidative stress and myocardial fibrosis, and maintenance of ion balance. Finally, this drug class's potential application and benefits in various clinical settings are described, along with a prospective outlook on future clinical practice and research directions.

The role of genetic testing in management and prognosis of individuals with inherited cardiomyopathies

Inherited cardiomyopathies are a heterogeneous group of heart muscle conditions where disease classification has traditionally been based on clinical characteristics. However, this does not always align with genotype. While there are well described challenges of genetic testing, understanding the role of genotype in patient management is increasingly required. We take a gene-by-gene approach, reviewing current evidence for the role of genetic testing in guiding prognosis and management of individuals with inherited cardiomyopathies. In particular, focusing on causal variants in genes definitively associated with arrhythmogenic cardiomyopathy, dilated cardiomyopathy, and hypertrophic cardiomyopathy. This review identifies genotype-specific disease sub-groups with strong evidence supporting the use of genetics in clinical management and highlights that at present, the spectrum of clinical utility is not reflected in current guidelines. Of 13 guideline or expert consensus statements for management of cardiomyopathies, there are seven gene-specific therapeutic recommendations that have been published from four documents. Understanding how genotype influences phenotype provides evidence for the role of genetic testing for prognostic and therapeutic purposes, moving us closer to precision-medicine based care.

Sudden cardiac death and post-traumatic stress disorder: More research is needed

Sudden cardiac death is an event which is traumatic for the individuals, who survive and their relatives. Very few research is concentrated on these survivals and the symptoms arising from post-traumatic stress disorders. In this journal, Birk et al. report on twelve eligible cardiac arrest survivors contacted, of which ten were enrolled. The authors report on heart rate variability biofeedback, which is, according to the authors, a promising non-pharmacologic approach for reducing anxiety. The intervention was comprised of daily sessions of diaphragmatic paced breathing and real-time monitoring of cardiac activity guided by a smartphone app and heart rate monitor. Ninety percent of the patients had good scores for intervention acceptability and feasibility, and 80 % reported good scores for its appropriateness and usability for reducing fear. Trait anxiety decreased significantly pre-to-post intervention. We comment on this finding highlighting other studies targeting sudden cardiac death and supporting that more research with very large randomized clinical trials is needed.

Anesthetic Management of Patients with Dilated Cardiomyopathy Undergoing Noncardiac Surgery

Dilated cardiomyopathy (DCM), a primary myocardial disease, is characterized by dilation of the left or both ventricles and systolic dysfunction with or without congestive heart failure. DCM per se is a well-recognized risk factor for sudden cardiac death and poor surgical outcomes following noncardiac surgery. Surgical trauma/stress represents unique challenges for DCM patient management. Unfortunately, there is a big knowledge gap in managing DCM patients undergoing non-cardiac surgery. Therefore, the aim of our review is to provide basic facts and current advances in DCM, as well as a practical guideline to perioperative care providers, for the management of surgical patients with DCM, who are quite rare compared with the general surgical population. This review summarizes recent advances in the medical management of DCM as well as perioperative assessment and management strategies for DCM patients undergoing noncardiac surgery. Optimal surgical outcomes depend on multiple-disciplinary care to minimize perioperative cardiovascular disturbances.

Integrated bioinformatics analysis for identifying key genes and pathways in female and male patients with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a common cause of heart failure, and males are more likely to suffer from DCM than females. This research aimed at exploring possible DCM-associated genes and their latent regulatory effects in female and male patients. WGCNA analysis found that in the yellow module, 341 and 367 key DEGs were identified in females and males, respectively. A total of 22 hub genes in females and 17 hub genes in males were identified from the PPI networks of the key DEGs based on Metascape database. And twelve and eight potential TFs of the key DEGs were also identified in females and males, respectively. Eight miRNAs of 15 key DEGs were screened in both females and males, which may be differentially expressed in females and males. Dual-luciferase reporter assay demonstrated that miR-21-5P could directly target the key gene MATN2. Furthermore, Sex differences in KEGG pathways were identified. Both KOBAS and GSEA analysis identified 19 significantly enriched pathways related to immune response in both females and males, and the TGF-β signaling pathway was exclusively identified in males. Network pharmacology analysis revealed that seven key DEGs were potential targets for the treatment of DCM, of which the OLR1 gene was only identified in males, the expression levels of the seven genes were verified by RT-PCR. The above results could offer a novel understanding of sex differences in key genes and pathways in DCM progression.

Jmjd4 Facilitates Pkm2 Degradation in Cardiomyocytes and Is Protective Against Dilated Cardiomyopathy

BACKGROUND

A large portion of idiopathic and familial dilated cardiomyopathy (DCM) cases have no obvious causal genetic variant. Although altered response to metabolic stress has been implicated, the molecular mechanisms underlying the pathogenesis of DCM remain elusive. The JMJD family proteins, initially identified as histone deacetylases, have been shown to be involved in many cardiovascular diseases. Despite their increasingly diverse functions, whether JMJD family members play a role in DCM remains unclear.

METHODS

We examined Jmjd4 expression in patients with DCM, and conditionally deleted and overexpressed Jmjd4 in cardiomyocytes in vivo to investigate its role in DCM. RNA sequencing, metabolites profiling, and mass spectrometry were used to dissect the molecular mechanism of Jmjd4-regulating cardiac metabolism and hypertrophy.

RESULTS

We found that expression of Jmjd4 is significantly decreased in hearts of patients with DCM. Induced cardiomyocyte-specific deletion of Jmjd4 led to spontaneous DCM with severely impaired mitochondrial respiration. Pkm2, the less active pyruvate kinase compared with Pkm1, which is normally absent in healthy adult cardiomyocytes but elevated in cardiomyopathy, was found to be drastically accumulated in hearts with Jmjd4 deleted. Jmjd4 was found mechanistically to interact with Hsp70 to mediate degradation of Pkm2 through chaperone-mediated autophagy, which is dependent on hydroxylation of K66 of Pkm2 by Jmjd4. By enhancing the enzymatic activity of the abundant but less active Pkm2, TEPP-46, a Pkm2 agonist, showed a significant therapeutic effect on DCM induced by Jmjd4 deficiency, and heart failure induced by pressure overload, as well.

CONCLUSIONS

Our results identified a novel role of Jmjd4 in maintaining metabolic homeostasis in adult cardiomyocytes by degrading Pkm2 and suggest that Jmjd4 and Pkm2 may be therapeutically targeted to treat DCM, and other cardiac diseases with metabolic dysfunction, as well.

Study of pathogenic genes in a pedigree with familial dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is a genetically heterogeneous cardiac disorder characterized by left ventricular dilation and contractile dysfunction. The substantial genetic heterogeneity evident in patients with DCM contributes to variable disease severity and complicates overall prognosis, which can be very poor.

AIM

To identify pathogenic genes in DCM through pedigree analysis.

METHODS

Our research team identified a patient with DCM in the clinic. Through investigation, we found that the family of this patient has a typical DCM pedigree. High-throughput sequencing technology, next-generation sequencing, was used to sequence the whole exomes of seven samples in the pedigree.

RESULTS

A novel and potentially pathogenic gene mutation-ANK2p.F3067L-was discovered. The mutation was completely consistent with the clinical information for this DCM pedigree. Sanger sequencing was used to further verify the locus of the mutation in pedigree samples. These results were consistent with those of high-throughput sequencing.

CONCLUSIONS

ANK2p.F3067L is considered a novel and potentially pathogenic gene mutation in DCM.

Characterization of cardiac involvement in children with LMNA-related muscular dystrophy

Introduction: LMNA-related muscular dystrophy is a rare entity that produce "laminopathies" such as Emery-Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy type 1B (LGMD1B), and LMNA-related congenital muscular dystrophy (L-CMD). Heart failure, malignant arrhythmias, and sudden death may occur. No consensus exists on cardiovascular management in pediatric laminopathies. The aim was to perform an exhaustive cardiologic follow-up in pediatric patients diagnosed with LMNA-related muscular dystrophy. Methods: Baseline cardiac work-up consisted of clinical assessment, transthoracic Doppler echocardiography, 12-lead electrocardiogram, electrophysiological study, and implantation of a long-term implantable cardiac loop recorder (ILR). Results: We enrolled twenty-eight pediatric patients diagnosed with EDMD (13 patients), L-CMD (11 patients), LGMD1B (2 patients), and LMNA-related mild weakness (2 patients). Follow-up showed dilated cardiomyopathy (DCM) in six patients and malignant arrhythmias in five (four concomitant with DCM) detected by the ILR that required implantable cardioverter defibrillator (ICD) implantation. Malignant arrhythmias were detected in 20% of our cohort and early-onset EDMD showed worse cardiac prognosis. Discussion: Patients diagnosed with early-onset EDMD are at higher risk of DCM, while potentially life-threatening arrhythmias without DCM appear earlier in L-CMD patients. Early onset neurologic symptoms could be related with worse cardiac prognosis. Specific clinical guidelines for children are needed to prevent sudden death.

Identification of a novel TNNI3 synonymous variant causing intron retention in autosomal recessive dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy type 2A (DCM2A, MIM: #611880) is a rare autosomal recessive heart disease leading to heart failure and sudden cardiac death. However, the causative role of TNNI3 in DCM2A is still questioned due to few cases reported and the conflicting molecular biological evidence.

METHODS

Trio whole-exome sequencing (trio-WES) was performed in a Chinese family with dilated cardiomyopathy. Sanger sequencing and real-time quantitative PCR were used to confirm the variants identified. Expression outcome caused by the synonymous mutation was validated by minigene splicing analyses.

RESULTS

The one-year-old girl presented severe left ventricular enlargement and significantly reduced left ventricular systolic function and she died of respiratory and heart failure soon after her diagnosis. Trio-WES revealed a compound heterozygous variants of TNNI3, a novel c.24G＞A (p.Ala8Ala) (NM_000363.4) in exon 2 and a deletion of entire gene. Minigene splicing analyses showed it led to an intron retention (c.24 + 1_24 + 45ins) by intron 2 cryptic splicing.

CONCLUSIONS

Our study describes and characterizes a synonymous mutation in TNNI3 gene, supporting the clinical diagnosis of an autosomal recessive DCM. Our study emphasizes the importance of functional analysis to assess the potential pathogenicity of synonymous mutations, especially when the synonymous variants are not annotated as benign.

Rbm20 ablation is associated with changes in the expression of titin-interacting and metabolic proteins

Dilated cardiomyopathy (DCM) is a major risk factor for developing heart failure and is often associated with an increased risk for life-threatening arrhythmia. Although numerous causal genes for DCM have been identified, RNA binding motif protein 20 (Rbm20) remains one of the few splicing factors that, when mutated or genetically ablated, leads to the development of DCM. In this study we sought to identify changes in the cardiac proteome in Rbm20 knockout (KO) rat hearts using global quantitative proteomics to gain insight into the molecular mechanisms precipitating the development of DCM in these rats. Our analysis identified changes in titin-interacting proteins involved in mechanical stretch-based signaling, as well as mitochondrial enzymes, which suggests that activation of pathological hypertrophy and altered mitochondrial metabolism and/or dysfunction, among other changes, contribute to the development of DCM in Rbm20 KO rats. Collectively, our findings provide the first report on changes in the cardiac proteome associated with genetic ablation of Rbm20.

A novel causative functional mutation in GATA6 gene is responsible for familial dilated cardiomyopathy as supported by in silico functional analysis

Dilated cardiomyopathy (DCM), one of the most common types of cardiomyopathies has a heterogeneous nature and can be seen in Mendelian forms. Next Generation Sequencing is a powerful tool for identifying novel variants in monogenic disorders. We used whole-exome sequencing (WES) and Sanger sequencing techniques to identify the causative mutation of DCM in an Iranian pedigree. We found a novel variant in the GATA6 gene, leading to substituting Histidine by Tyrosine at position 329, observed in all affected family members in the pedigree, whereas it was not established in any of the unaffected ones. We hypothesized that the H329Y mutation may be causative for the familial pattern of DCM in this family. The predicted models of GATA6 and H329Y showed the high quality according to PROCHECK and ERRAT. Nonetheless, simulation results revealed that the protein stability decreased after mutation, while the flexibility may have been increased. Hence, the mutation led to the increased compactness of GATA6. Overall, these data indicated that the mutation could affect the protein structure, which may be related to the functional impairment of GATA6 upon H329Y mutation, likewise their involvement in pathologies. Further functional investigations would help elucidating the exact mechanism.

An Robust Rank Aggregation and Least Absolute Shrinkage and Selection Operator Analysis of Novel Gene Signatures in Dilated Cardiomyopathy

Objective: Dilated cardiomyopathy (DCM) is a heart disease with high mortality characterized by progressive cardiac dilation and myocardial contractility reduction. The molecular signature of dilated cardiomyopathy remains to be defined. Hence, seeking potential biomarkers and therapeutic of DCM is urgent and necessary.

Methods: In this study, we utilized the Robust Rank Aggregation (RRA) method to integrate four eligible DCM microarray datasets from the GEO and identified a set of significant differentially expressed genes (DEGs) between dilated cardiomyopathy and non-heart failure. Moreover, LASSO analysis was carried out to clarify the diagnostic and DCM clinical features of these genes and identify dilated cardiomyopathy derived diagnostic signatures (DCMDDS).

Results: A total of 117 DEGs were identified across the four microarrays. Furthermore, GO analysis demonstrated that these DEGs were mainly enriched in the regulation of inflammatory response, the humoral immune response, the regulation of blood pressure and collagen–containing extracellular matrix. In addition, KEGG analysis revealed that DEGs were mainly enriched in diverse infected signaling pathways. Moreover, Gene set enrichment analysis revealed that immune and inflammatory biological processes such as adaptive immune response, cellular response to interferon and cardiac muscle contraction, dilated cardiomyopathy are significantly enriched in DCM. Moreover, Least absolute shrinkage and selection operator (LASSO) analyses of the 18 DCM-related genes developed a 7-gene signature predictive of DCM. This signature included ANKRD1, COL1A1, MYH6, PERELP, PRKACA, CDKN1A, and OMD. Interestingly, five of these seven genes have a correlation with left ventricular ejection fraction (LVEF) in DCM patients.

Conclusion: Our present study demonstrated that the signatures could be robust tools for predicting DCM in clinical practice. And may also be potential treatment targets for clinical implication in the future.

Next-Generation Sequencing Reveals Novel Genetic Variants for Dilated Cardiomyopathy in Pediatric Chinese Patients

Dilated cardiomyopathy (DCM) is a myocardial disease characterized by bilateral or left ventricular cardiac dilation and systolic dysfunction that can lead to heart failure and sudden cardiac death in children. Many studies have focused on genetic variation in DCM-related genes in adult populations; however, the mutational landscape in pediatric DCM patients remains undetermined, especially in the Chinese population. We applied next-generation sequencing (NGS) technology to genetically analyze 46 pediatric DCM patients to reveal genotype-phenotype correlations. Our results indicated DCM-associated pathogenic mutations in 10 genes related to the structure or function of the sarcomere, desmosome, and cytoskeleton. We also identified 6 pathogenic mutations (5 novel) in the Titin (TTN) gene that resulted in truncated TTN variants in 6 (13%) out of 46 patients. Correlations between TTN mutations and clinical outcomes were assessed. Our data indicate that one-third of pediatric DCM cases are caused by genetic mutations. The role of TTN variants should not be underestimated in pediatric DCM and age-dependent pathogenic penetrance of these mutations should be considered for familial DCM cases. We argue that genetic testing of DCM cases is valuable for predicting disease severity, prognosis, and recurrence risk, and for screening first-degree relatives.

MicroRNAs in Hypertrophic, Arrhythmogenic and Dilated Cardiomyopathy

MicroRNAs (miRNAs) are a class of non-coding RNAs of about 20 nucleotides in length, involved in the regulation of many biochemical pathways in the human body. The level of miRNAs in tissues and circulation can be deregulated because of altered pathophysiological mechanisms; thus, they can be employed as biomarkers for different pathological conditions, such as cardiac diseases. This review summarizes published findings of these molecular biomarkers in the three most common structural cardiomyopathies: human dilated, arrhythmogenic and hypertrophic cardiomyopathy.

Dilated cardiomyopathy and arrhythmogenic left ventricular cardiomyopathy: a comprehensive genotype-imaging phenotype study

AIMS

Myocardial scar detected by cardiovascular magnetic resonance has been associated with sudden cardiac death in dilated cardiomyopathy (DCM). Certain genetic causes of DCM may cause a malignant arrhythmogenic phenotype. The concepts of arrhythmogenic left ventricular (LV) cardiomyopathy (ALVC) and arrhythmogenic DCM are currently ill-defined. We hypothesized that a distinctive imaging phenotype defines ALVC.

METHODS AND RESULTS

Eighty-nine patients with DCM-associated mutations [desmoplakin (DSP) n = 25, filamin C (FLNC) n = 7, titin n = 30, lamin A/C n = 12, bcl2-associated athanogene 3 n = 3, RNA binding motif protein 20 n = 3, cardiac sodium channel NAv1.5 n = 2, and sarcomeric genes n = 7] were comprehensively phenotyped. Clustering analysis resulted in two groups: 'DSP/FLNC genotypes' and 'non-DSP/FLNC'. There were no significant differences in age, sex, symptoms, baseline electrocardiography, arrhythmia burden, or ventricular volumes between the two groups. Subepicardial LV late gadolinium enhancement with ring-like pattern (at least three contiguous segments in the same short-axis slice) was observed in 78.1% of DSP/FLNC genotypes but was absent in the other DCM genotypes (P < 0.001). Left ventricular ejection fraction (LVEF) and global longitudinal strain were lower in other DCM genotypes (P = 0.053 and P = 0.015, respectively), but LV regional wall motion abnormalities were more common in DSP/FLNC genotypes (P < 0.001). DSP/FLNC patients with non-sustained ventricular tachycardia (NSVT) had more LV scar (P = 0.010), whereas other DCM genotypes patients with NSVT had lower LVEF (P = 0.001) than patients without NSVT.

CONCLUSION

DSP/FLNC genotypes cause more regionality in LV impairment. The most defining characteristic is a subepicardial ring-like scar pattern in DSP/FLNC, which should be considered in future diagnostic criteria for ALVC.

Familial dilated cardiomyopathy with RBM20 mutation in an Indian patient: a case report

Background

Dilated cardiomyopathy (DCM) is a disease of the heart muscle characterized by ventricular dilation and a left ventricular ejection fraction of less than 40%. Unlike hypertrophic cardiomyopathy (HCM) and arrhythmogenic right ventricular cardiomyopathy (ARVC), DCM-causing mutations are present in a large number of genes. In the present study, we report a case of the early age of onset of DCM associated with a pathogenic variant in the RBM20 gene in a patient from India.

Case presentation

A 19-year-old Indian male diagnosed with DCM was suggested for heart transplantation. His ECG showed LBBB and echocardiography showed an ejection fraction of 14%. He had a sudden cardiac death. A detailed family history revealed it to be a case of familial DCM. Genetic screening identified the c.1900C>T variant in the RBM20 gene which led to a missense variant of amino acid 634 (p.Arg634Trp).

Conclusion

To the best of our knowledge, the variant p.Arg634Trp has been earlier reported in the Western population, but this is the first case of p.Arg634Trp in an Indian patient. The variant has been reported to be pathogenic at an early age of onset; therefore, close clinical follow-up should be done for the family members caring for the variant.

Generation of an iPSC cell line (USFi003-A) from a patient with dilated cardiomyopathy carrying a heterozygous mutation in LMNA (p.R541C)

Mutations in the gene that encodes the nuclear envelope proteins lamin A/C (LMNA) are considered to be a prominent cause of Dilated cardiomyopathy (DCM), a leading cause of heart failure and a prevalent indication for heart transplant. Here we described the generation of induced pluripotent stem cells (iPSCs) from a 53-year-old female with DCM plus progressive conduction disease who carry a heterozygous mutation in LMNA (c.1621C > T, p.R541C). PBMCs isolated from the patient were reprogrammed with Yamanaka factors KOS, KLF4, and c-MYC by the non-integrating sendai virus vector system. The obtained iPSC lines demonstrated normal karyotype and pluripotent identity.

Heterozygous desmin gene (DES) mutation contributes to familial dilated cardiomyopathy

Familial dilated cardiomyopathy (FDCM) is characterized by high genetic heterogeneity and an increased risk of heart failure or sudden cardiac death in adults. We report the case of a 62-year-old man with a 2-month history of shortness of breath during activity, without paroxysmal nocturnal dyspnea. The patient underwent a series of examinations including transthoracic echocardiography, coronary arteriography, transesophageal echocardiography, and myocardial perfusion imaging. After excluding secondary cardiac enlargement, he was diagnosed with dilated cardiomyopathy (DCM). His sister had also been diagnosed with DCM several years before. Genetic sequencing analysis revealed that the patient, his sister, and his son all had the same mutation in the desmin gene (DES) (chr2-220785662, c.1010C>T). Genetic testing confirmed a heterozygous DES mutation contributing to FDCM. In this case, the etiology of the patient’s whole-heart enlargement was determined as FDCM with DES gene mutation. This is the first report to describe DES c.1010C>T as a cause of FDCM.

Malignant Arrhythmogenic Role Associated with RBM20: A Comprehensive Interpretation Focused on a Personalized Approach

The RBM20 gene encodes the muscle-specific splicing factor RNA-binding motif 20, a regulator of heart-specific alternative splicing. Nearly 40 potentially deleterious variants in RBM20 have been reported in the last ten years, being found to be associated with highly arrhythmogenic events in familial dilated cardiomyopathy. Frequently, malignant arrhythmias can be a primary manifestation of disease. The early recognition of arrhythmic genotypes is crucial in avoiding lethal episodes, as it may have an impact on the adoption of personalized preventive measures. Our study performs a comprehensive update of data concerning rare variants in RBM20 that are associated with malignant arrhythmogenic phenotypes with a focus on personalized medicine.

Genetic Restrictive Cardiomyopathy: Causes and Consequences-An Integrative Approach

The sarcomere as the smallest contractile unit is prone to alterations in its functional, structural and associated proteins. Sarcomeric dysfunction leads to heart failure or cardiomyopathies like hypertrophic (HCM) or restrictive cardiomyopathy (RCM) etc. Genetic based RCM, a very rare but severe disease with a high mortality rate, might be induced by mutations in genes of non-sarcomeric, sarcomeric and sarcomere associated proteins. In this review, we discuss the functional effects in correlation to the phenotype and present an integrated model for the development of genetic RCM.

hiPSC-Derived Cardiac Tissue for Disease Modeling and Drug Discovery

Relevant, predictive normal, or disease model systems are of vital importance for drug development. The difference between nonhuman models and humans could contribute to clinical trial failures despite ideal nonhuman results. As a potential substitute for animal models, human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) provide a powerful tool for drug toxicity screening, modeling cardiovascular diseases, and drug discovery. Here, we review recent hiPSC-CM disease models and discuss the features of hiPSC-CMs, including subtype and maturation and the tissue engineering technologies for drug assessment. Updates from the international multisite collaborators/administrations for development of novel drug discovery paradigms are also summarized.

LncRNA AC061961.2 overexpression inhibited endoplasmic reticulum stress induced apoptosis in dilated cardiomyopathy rats and cardiomyocytes via activating wnt/β-catenin pathway

Down-regulated lncRNA AC061961.2 in dilated cardiomyopathy (DCM) patients was previous reported. Whether AC061961.2 has regulatory effect on DCM still need exploration. Here, we tried to investigate the effect of AC061961.2 on DCM. After DCM model rat was established through injecting Adriamycin, left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), left ventricular ejection fraction (LVEF), and left ventricular fractional shortening (LVFS) were measured by echocardiography. Histopathological changes and apoptosis were detected by hematoxylin-eosin, Masson staining, and TUNEL. After cardiomyocytes were isolated and identified by immunofluorescence, DCM cell model was established by injecting adriamycin. After transfected with overexpressed-AC061961.2 plasmids, cell apoptosis was detected by flow cytometry. The expressions of AC061961.2, β-catenin, Axin2, c-Myc, CRP78, CHOP, Caspase-3, Bcl-2, and Bax in cardiomyocytes and heart tissues were detected by RT-qPCR or western blot. LVEDD and LVESD were increased while LVEF and LVFS were decreased in DCM rats. The histopathological of heart tissues showed a typical sign of DCM. Apoptosis were increased in heart tissues of DCM rats. In DCM rats, the expressions of AC061961.2, β-catenin, Axin2, c-Myc, and Bcl-2 were decreased, the expressions of CRP78, CHOP, Caspase-3, and Bax were increased. After the overexpression of AC061961.2, levels of β-catenin, Axin2, c-Myc, and Bcl-2 were increased, while levels of CRP78, CHOP, Caspase-3, and Bax were decreased, compared with that in DCM cardiomyocytes. LncRNA AC061961.2 overexpression inhibited endoplasmic reticulum stress induced apoptosis in DCM rats and cardiomyocytes via activating Wnt/β-catenin pathway.

Molecular Basis of Inflammation in the Pathogenesis of Cardiomyopathies

Cardiomyopathies (CMPs) represent a diverse group of heart muscle diseases, grouped into specific morphological and functional phenotypes. CMPs are associated with mutations in sarcomeric and non-sarcomeric genes, with several suspected epigenetic and environmental mechanisms involved in determining penetrance and expressivity. The understanding of the underlying molecular mechanisms of myocardial diseases is fundamental to achieving a proper management and treatment of these disorders. Among these, inflammation seems to play an important role in the pathogenesis of CMPs. The aim of the present study is to review the current knowledge on the role of inflammation and the immune system activation in the pathogenesis of CMPs and to identify potential molecular targets for a tailored anti-inflammatory treatment.

From Anti-EBV Immune Responses to the EBV Diseasome via Cross-reactivity

Sequence analyses highlight a massive peptide sharing between immunoreactive Epstein-Barr virus (EBV) epitopes and human proteins that—when mutated, deficient or improperly functioning—associate with tumorigenesis, diabetes, lupus, multiple sclerosis, rheumatoid arthritis, and immunodeficiencies, among others. Peptide commonality appears to be the molecular platform capable of linking EBV infection to the vast EBV-associated diseasome via cross-reactivity and questions the hypothesis of the “negative selection” of self-reactive lymphocytes. Of utmost importance, this study warns that using entire antigens in anti-EBV immunotherapies can associate with autoimmune manifestations and further supports the concept of peptide uniqueness for designing safe and effective anti-EBV immunotherapies.

A very long-term observation of a family with dilated cardiomyopathy and overlapping phenotype from lamin A/C mutation

AIMS

We aim to describe one of the longest longitudinal follow-ups reported so far (>22 years), concerning a whole family affected by a missense lamin A/C mutation (Arg60Gly), which manifested as an overlapping phenotype with cardiac and extracardiac involvement over time.

METHODS

Starting from the family history, two generations of that family were prospectively observed, from 1997 until 2020. At baseline, four individuals with dilated cardiomyopathy and cardiac conduction defects showed the same mutation. This was also found in three young individuals, phenotypically unaffected at baseline assessment.

RESULTS

The prolonged clinical and laboratory evaluation has shown the evolution of an overlapping phenotype in which cardiac alterations have been associated with lipodystrophy and neurological manifestations. In the first observed generation, the prognosis was negatively affected by the progression of heart failure and lipodystrophy, whereas in the second generation the first phenotypic manifestations became evident after the 2nd decade. Cardiac magnetic resonance played a relevant role in the early detection of cardiac alteration. Right bundle branch block was another sign of initial phenotypical expression.

CONCLUSION

In lamin A/C gene mutation carriers, a strict, multidisciplinary follow-up allows the opportunity to monitor the progress of the disease and to intervene precociously with the best available treatments.

Pathophysiology and pathological remodelling associated with dilated cardiomyopathy in broiler chickens predisposed to heart pump failure

Broiler chickens selected for rapid growth are highly susceptible to dilated cardiomyopathy (DCM). In order to elucidate the pathophysiology of DCM, the present study examines the fundamental features of pathological remodelling associated with DCM in broiler chickens using light microscopy, transmission electron microscopy (TEM), and synchrotron Fourier Transform Infrared (FTIR) micro-spectroscopy. The morphological features and FTIR spectra of the left ventricular myocardium were compared among broiler chickens affected by DCM with clinical signs of heart pump failure, apparently normal fast-growing broiler chickens showing signs of subclinical DCM (high risk of heart failure), slow-growing broiler chickens (low risk of heart failure) and Leghorn chickens (resistant to heart failure, used here as physiological reference). The findings indicate that DCM and heart pump failure in fast-growing broiler chickens are a result of a complex metabolic syndrome involving multiple catabolic pathways. Our data indicate that a good deal of DCM pathophysiology in chickens selected for rapid growth is associated with conformational changes of cardiac proteins, and pathological changes indicative of accumulation of misfolded and aggregated proteins in the affected cardiomyocytes. From TEM image analysis it is evident that the affected cardiomyocytes demonstrate significant difficulty in the disposal of damaged proteins and maintenance of proteostasis, which leads to pathological remodelling of the heart and contractile dysfunction. It appears that the underlying causes of accumulation of damaged proteins are associated with dysregulated auto phagosome and proteasome systems, which, in susceptible individuals, create a milieu conducive for the development of DCM and heart failure. RESEARCH HIGHLIGHTS The light and electron microscopy image analyses revealed degenerative changes and protein aggregates in the cardiomyocytes of chickens affected by DCM. The analyses of FTIR spectra of the myocardium revealed that DCM and heart pump failure in broiler chickens are associated with conformational changes of myocardial proteins. The morphological changes in cardiomyocytes and conformational changes in myocardial proteins architecture are integral constituents of pathophysiology of DCM in fast-growing broiler chickens.

Dilated cardiomyopathies and non-compaction cardiomyopathy

Dilated cardiomyopathy (DCM) is the most common form of cardiomyopathy and one of the most common causes of heart failure. It is characterized by left or biventricular dilation and a reduced systolic function. The causes are manifold and range from myocarditis to alcohol and other toxins, to rheumatological, endocrinological, and metabolic diseases. Peripartum cardiomyopathy is a special form that occurs at the end of or shortly after pregnancy. Genetic mutations can be detected in approximately 30-50% of DCM patients. Owing to the growing possibilities of genetic diagnostics, increasingly more triggering variants and hereditary mechanisms emerge. This is particularly important with regard to risk stratification for patients with variants with an increased risk of arrhythmias. Patient prognosis is determined by the occurrence of heart failure and arrhythmias. In addition to the treatment of the underlying disease or the elimination of triggering harmful toxins, therapy consists in guideline-directed heart failure treatment including drug and device therapy.

Genetic variants of uncertain significance: How to match scientific rigour and standard of proof in sudden cardiac death?

In many SCD cases, in particular in pediatric age, autopsy can be completely negative and then a post-mortem genetic testing (molecular autopsy) is indicated. In NGS era finding new/rare variants is extremely frequent and, when only variants of unknown significance are found, molecular autopsy fails to find a cause of death. We describe the emblematic case of the sudden death of a 7-year-old girl. We performed a full-body micro-CT analysis, an accurate autopsy, a serum tryptase test and toxicological tests. Since the only macroscopic abnormality we found was a myocardial bridging (length: 1,1 cm, thickness: 0,5 cm) of the left anterior descending coronary artery, a molecular autopsy has been performed. NGS analysis on victim DNA detected rare variants in DPP6, MYH7, SCN2B and NOTCH1 and segregation analysis was then achieved. On the basis of ACMG/AMP (clinical) guidelines, all the found variants were classified as of unknown significance. In other words, both the macroscopic and genetic anomalies we found were of uncertain significance and then the autopsy failed to find the cause of the death. Our case raises three main discussion points: (a) economical, ethical and legal limitations of genetic investigation; (b) risk that genetic testing does not succeed in finding a certain cause of the death; (c) absence of specific guidelines to face the problem of VUS in forensic cases.

Peripheral microRNA panels to guide the diagnosis of familial cardiomyopathy

Etiology-based diagnosis of dilated cardiomyopathy (DCM) is challenging. We evaluated whether peripheral microRNAs (miRNAs) could be used to characterize the DCM etiology. We investigated the miRNA plasma profiles of 254 subjects that comprised 5 groups: Healthy subjects (n = 70), idiopathic DCM patients (n = 55), ischemic DCM patients (n = 60) and 2 groups of patients with pathogenic variants responsible for familial DCM in the LMNA (LMNA^MUT, n = 37) and BAG3 (BAG3^MUT, n = 32) genes. Diagnostic performance was assessed using receiver operating characteristic curves. In a screening study (n = 30), 179 miRNAs robustly detected in plasma samples were profiled in idiopathic DCM and carriers of pathogenic variants. After filtering, 26 miRNA candidates were selected for subsequent quantification in the whole study population. In the validation study, a 6-miRNA panel identified familial DCM with an AUC (95% confidence interval [CI]) of 87.8 (82.0-93.6). The 6-miRNA panel also distinguished between specific DCM etiologies with AUCs ranging from 85.9 to 89.9. Only 1 to 10 of the subjects in the first and second tertiles of the 6-miRNA panel were patients with familial DCM. Additionally, a 5-miRNA panel showed an AUC (95% CI) of 87.5 (80.4-94.6) for the identification of carriers with pathogenic variants who were phenotypically negative for DCM. The 5-miRNA panel discriminated between carriers and healthy controls with AUCs ranging from 83.2 to 90.8. Again, only 1 to 10 of the subjects in the lowest tertiles of the 5-miRNA panel were carriers of pathogenic variants. In conclusion, miRNA signatures could be used to rule out patients with pathogenic variants responsible for DCM.

Sudden Cardiac Death and Copy Number Variants: What Do We Know after 10 Years of Genetic Analysis?

Over the last ten years, analysis of copy number variants has increasingly been applied to the study of arrhythmogenic pathologies associated with sudden death, mainly due to significant advances in the field of massive genetic sequencing. Nevertheless, few published reports have focused on the prevalence of copy number variants associated with sudden cardiac death. As a result, the frequency of these genetic alterations in arrhythmogenic diseases as well as their genetic interpretation and clinical translation has not been established. This review summarizes the current available data concerning copy number variants in sudden cardiac death-related diseases.

Emerging role of microRNAs in dilated cardiomyopathy: evidence regarding etiology

Dilated cardiomyopathy (DCM) is a heart muscle disease characterized by ventricular dilation and systolic dysfunction in the absence of abnormal loading conditions or coronary artery disease. This cardiac disorder is a major health problem due to its high prevalence, morbidity, and mortality. DCM is a complex disease with a common phenotype but heterogeneous pathological mechanisms. Early etiological diagnosis and prognosis stratification is crucial for the clinical management of the patient. Advances in imaging technology and genetic tests have provided useful tools for clinical practice. Nevertheless, the assessment of the disease remains challenging. Novel noninvasive indicators are still needed to assist in decision-making. microRNAs (miRNAs), a group of small noncoding RNAs, have been identified as key mediators of cell biology. They are found in a stable form in body fluids and their concentration is altered in response to stress. Previous research has suggested that the miRNA signature constitutes a novel source of noninvasive biomarkers for a wide array of cardiovascular diseases. Specifically, several studies have reported the potential role of miRNAs as clinical indicators among the etiologies of DCM. However, this field has not been reviewed in detail. Here, we summarize the evidence of intracellular and circulating miRNAs in DCM and their usefulness in the development of novel diagnostic, prognostic and therapeutic approaches, with a focus on DCM etiology. Although the findings are still preliminary, due to methodological and technical limitations and the lack of robust population-based studies, miRNAs constitute a promising tool to assist in the clinical management of DCM.

Is genomic screening necessary for fetuses who suffer moderate to severe tricuspid regurgitation?: A case report

RATIONALE

Tricuspid regurgitation (TR) is a frequent finding during echocardiography screening in fetal or neonatal life, which reveals a weak association between TR and cardiac malformation. Except for structural abnormalities, dilated cardiomyopathy (DCM) ranks as the top reason for early child morbidity and mortality among all kinds of cardiomyopathy. In the early fetal stage, cardiac abnormalities detected by early fetal genetic testing followed by abnormalities on ultrasound would provide more valuable information for parents and physicians to make a better therapeutic schedule.

PATIENT CONCERNS

A case of severe TR was found via the fetal ultrasound screening. After birth, this child suffered severe heart dysfunction, and echocardiography confirmed a DCM phenotype within a very short time.

DIAGNOSIS AND INTERVENTION

A 40-year-old female received routine fetal echocardiographic screening, which demonstrated that the fetus presented severe TR. Six months after birth, the baby experienced severe heart failure, as the EF dropped to 22% with an extremely large LV chamber. The genomic sequence had been determined, and 3 pathogenic gene mutations located in 2 genes, cardiac troponin T (TNNT2) c.548G>A, desmoplakin (DSP) c.3146C>T, and DSP c.5213G>A, were identified. Finally, the patient was diagnosed with DCM. This child received digoxin, hydrochlorothiazide, spironolactone diuresis, captopril, and L-carnitine, and the symptoms of heart failure had been controlled as the patient waited for heart transplantation.

OUTCOMES

During the follow-up, the patient still suffered from poor heart function and an enlarged left ventricle. Concomitantly, the parents placed her on a waiting list for heart transplantation.

LESSONS

Fetal TR is a common phenomenon, and many studies have indicated that isolated TR is not an appropriate predictor of chromosomal abnormalities or congenital heart defects. However, according to this case, it is urgent to recommend that the mother should take advantage of free fetal DNA analysis in a maternal blood sample to obtain further molecular evidence once fetal echocardiography reveals moderate to severe TR with any maternal high-risk factors for birth defects.

FLNC pathogenic variants in patients with cardiomyopathies: Prevalence and genotype-phenotype correlations

Pathogenic variants in FLNC encoding filamin C have been firstly reported to cause myopathies, and were recently linked to isolated cardiac phenotypes. Our aim was to estimate the prevalence of FLNC pathogenic variants in subtypes of cardiomyopathies and to study the relations between phenotype and genotype. DNAs from a cohort of 1150 unrelated index-patients with isolated cardiomyopathy (700 hypertrophic, 300 dilated, 50 restrictive cardiomyopathies, and 100 left ventricle non-compactions) have been sequenced on a custom panel of 51 cardiomyopathy disease-causing genes. An FLNC pathogenic variant was identified in 28 patients corresponding to a prevalence ranging from 1% to 8% depending on the cardiomyopathy subtype. Truncating variants were always identified in patients with dilated cardiomyopathy, while missense or in-frame indel variants were found in other phenotypes. A personal or family history of sudden cardiac death (SCD) was significantly higher in patients with truncating variants than in patients carrying missense variants (P = .01). This work reported the first observation of a left ventricular non-compaction associated with a unique probably causal variant in FLNC which highlights the role of FLNC in cardiomyopathies. A correlation between the nature of the variant and the cardiomyopathy subtype was observed as well as with SCD risk.

Myocardial-specific ablation of Jumonji and AT-rich interaction domain-containing 2 (Jarid2) leads to dilated cardiomyopathy in mice

Cardiomyopathy is a common myocardial disease that can lead to sudden death. However, molecular mechanisms underlying cardiomyopathy remain unclear. Jumonji and AT-rich interaction domain-containing 2 (Jarid2) is necessary for embryonic heart development, but functions of Jarid2 after birth remain to be elucidated. Here, we report that myocardial-specific deletion of Jarid2 using αMHC::Cre mice (Jarid2 ^αMHC) causes dilated cardiomyopathy (DCM) and premature death 6-9 months after birth. To determine functions of Jarid2 in the adult heart and DCM, we analyzed gene expression in the heart at postnatal day (p)10 (neonatal) and 7 months (DCM). Pathway analyses revealed that dysregulated genes in Jarid2 ^αMHC hearts at p10, prior to cardiomyopathy, represented heart development and muscle contraction pathways. At 7 months, down-regulated genes in Jarid2 ^αMHC hearts were enriched in metabolic process and ion channel activity pathways and up-regulated genes in extracellular matrix components. In normal hearts, expression levels of contractile genes were increased from p10 to 7 months but were not sufficiently increased in Jarid2 ^αMHC hearts. Moreover, Jarid2 was also necessary to repress fetal contractile genes such as TroponinI1, slow skeletal type (Tnni1) and Actin alpha 2, smooth muscle (Acta2) in neonatal stages through ErbB2-receptor tyrosine kinase 4 (ErbB4) signaling. Interestingly, Ankyrin repeat domain 1 (Ankrd1) and Neuregulin 1 (Nrg1), whose expression levels are known to be increased in the failing heart, were already elevated in Jarid2 ^αMHC hearts within 1 month of birth. Thus, we demonstrate that ablation of Jarid2 in cardiomyocytes results in DCM and suggest that Jarid2 plays important roles in cardiomyocyte maturation during neonatal stages.

Influenza and sudden unexpected death: the possible role of peptide cross-reactivity

This study investigates the hypothesis that cross-reactions may occur between human cardiac proteins and influenza antigens, thus possibly representing the molecular mechanism underlying influenzaassociated sudden unexpected death (SUD). Using titin protein as a research model, data were obtained on (1) the occurrence of the titin octapeptide AELLVLLE or its mimic AELLVALE in influenza A virus hemagglutinin (HA) sequences; (2) the immunological potential of AELLVLLE and its mimic AELLVALE; (3) the possible role of the flanking amino acid aa) context of the two octapeptide determinants in eliciting cross-reactivity between the human cardiac titin protein and HA antigens.

Whole-exome sequencing reveals doubly novel heterozygous Myosin Binding Protein C and Titin mutations in a Chinese patient with severe dilated cardiomyopathy

BACKGROUND

Dilated Cardiomyopathy is a serious heart disorder that may induce sudden cardiac death and heart failure. Significant progress has been made in understanding the molecular basis of dilated cardiomyopathy. In previous studies, mutations in more than fifty genes have been identified in dilated cardiomyopathy patients. The purpose of this study was to detect the genetic lesion in a family from the central south of China affected by severe dilated cardiomyopathy.

METHODS

Whole-exome sequencing combined with cardiomyopathy-related genes list were used to analyse the mutations of the proband. Co-segregation analysis was performed by Sanger sequencing.Results and conclusionsTwo novel heterozygous mutations - Myosin Binding Protein C: p.L1014RfsX6 and Titin: p.R9793X - were identified in the proband. The deletion mutation c.3041delT/p.L1014RfsX6 caused a premature stop codon at position 1020 in exon 28 of the Myosin Binding Protein C. The nonsense mutation, c.29377 C>T/ p. R9793X, of Titin was located in the highly evolutionarily conserved domain, resulting in truncation of the Titin protein as well. Co-segregation analysis further revealed that the Myosin Binding Protein C mutation came from his mother and the Titin mutation came from his father. Both mutations are reported in dilated cardiomyopathy patients for the first time. Our study not only provides a unique example of the genes and molecular mechanisms involved in dilated cardiomyopathy but also expands the spectrum of Myosin Binding Protein C and Titin mutations and contributes to the genetic diagnosis and counselling of dilated cardiomyopathy patients.

Alternative Splicing Regulator RBM20 and Cardiomyopathy

RBM20 is a vertebrate-specific RNA-binding protein with two zinc finger (ZnF) domains, one RNA-recognition motif (RRM)-type RNA-binding domain and an arginine/serine (RS)-rich region. RBM20 has initially been identified as one of dilated cardiomyopathy (DCM)-linked genes. RBM20 is a regulator of heart-specific alternative splicing and Rbm20^ΔRRM mice lacking the RRM domain are defective in the splicing regulation. The Rbm20^ΔRRM mice, however, do not exhibit a characteristic DCM-like phenotype such as dilatation of left ventricles or systolic dysfunction. Considering that most of the RBM20 mutations identified in familial DCM cases were heterozygous missense mutations in an arginine-serine-arginine-serine-proline (RSRSP) stretch whose phosphorylation is crucial for nuclear localization of RBM20, characterization of a knock-in animal model is awaited. One of the major targets for RBM20 is the TTN gene, which is comprised of the largest number of exons in mammals. Alternative splicing of the TTN gene is exceptionally complicated and RBM20 represses >160 of its consecutive exons, yet detailed mechanisms for such extraordinary regulation are to be elucidated. The TTN gene encodes the largest known protein titin, a multi-functional sarcomeric structural protein specific to striated muscles. As titin is the most important factor for passive tension of cardiomyocytes, extensive heart-specific and developmentally regulated alternative splicing of the TTN pre-mRNA by RBM20 plays a critical role in passive stiffness and diastolic function of the heart. In disease models with diastolic dysfunctions, the phenotypes were rescued by increasing titin compliance through manipulation of the Ttn pre-mRNA splicing, raising RBM20 as a potential therapeutic target.

Exploring the Crosstalk Between LMNA and Splicing Machinery Gene Mutations in Dilated Cardiomyopathy

Mutations in the LMNA gene, which encodes for the nuclear lamina proteins lamins A and C, are responsible for a diverse group of diseases known as laminopathies. One type of laminopathy is Dilated Cardiomyopathy (DCM), a heart muscle disease characterized by dilation of the left ventricle and impaired systolic function, often leading to heart failure and sudden cardiac death. LMNA is the second most commonly mutated gene in DCM. In addition to LMNA, mutations in more than 60 genes have been associated with DCM. The DCM-associated genes encode a variety of proteins including transcription factors, cytoskeletal, Ca2+-regulating, ion-channel, desmosomal, sarcomeric, and nuclear-membrane proteins. Another important category among DCM-causing genes emerged upon the identification of DCM-causing mutations in RNA binding motif protein 20 (RBM20), an alternative splicing factor that is chiefly expressed in the heart. In addition to RBM20, several essential splicing factors were validated, by employing mouse knock out models, to be embryonically lethal due to aberrant cardiogenesis. Furthermore, heart-specific deletion of some of these splicing factors was found to result in aberrant splicing of their targets and DCM development. In addition to splicing alterations, advances in next generation sequencing highlighted the association between splice-site mutations in several genes and DCM. This review summarizes LMNA mutations and splicing alterations in DCM and discusses how the interaction between LMNA and splicing regulators could possibly explain DCM disease mechanisms.

Phosphorylation of the RSRSP stretch is critical for splicing regulation by RNA-Binding Motif Protein 20 (RBM20) through nuclear localization

RBM20 is a major regulator of heart-specific alternative pre-mRNA splicing of TTN encoding a giant sarcomeric protein titin. Mutation in RBM20 is linked to autosomal-dominant familial dilated cardiomyopathy (DCM), yet most of the RBM20 missense mutations in familial and sporadic cases were mapped to an RSRSP stretch in an arginine/serine-rich region of which function remains unknown. In the present study, we identified an R634W missense mutation within the stretch and a G1031X nonsense mutation in cohorts of DCM patients. We demonstrate that the two serine residues in the RSRSP stretch are constitutively phosphorylated and mutations in the stretch disturb nuclear localization of RBM20. Rbm20^S637A knock-in mouse mimicking an S635A mutation reported in a familial case showed a remarkable effect on titin isoform expression like in a patient carrying the mutation. These results revealed the function of the RSRSP stretch as a critical part of a nuclear localization signal and offer the Rbm20^S637A mouse as a good model for in vivo study.

A multidimensional sight on cardiac failure: uncovered from structural to molecular level

Heart failure is one of the leading causes of death, with high mortality rate within 5 years after diagnosis. Treatment and prognosis options for heart failure primarily targeted on hemodynamic and neurohumoral components that drive progressive deterioration of the heart. However, given the multifactorial background that eventually leads to the "phenotype" named heart failure, better insight into the various components may lead to personalized treatment opportunities. Indeed, currently used criteria to diagnose and/or classify heart failure are possibly too focused on phenotypic improvement rather than the molecular driver of the disease and could therefore be further refined by integrating the leap of molecular and cellular knowledge. The ambiguity of the ejection fraction-based classification criteria became evident with development of advanced molecular techniques and the dawn of omics disciplines which introduced the idea that disease is caused by a myriad of cellular and molecular processes rather than a single event or pathway. The fact that different signaling pathways may underlie similar clinical manifestations calls for a more holistic study of heart failure. In this context, the systems biology approach can offer a better understanding of how different components of a system are altered during disease and how they interact with each other, potentially leading to improved diagnosis and classification of this condition. This review is aimed at addressing heart failure through a multilayer approach that covers individually some of the anatomical, morphological, functional, and tissue aspects, with focus on cellular and subcellular features as an alternative insight into new therapeutic opportunities.

Whole exome sequencing identifies a novel mutation (c.333 + 2T > C) of TNNI3K in a Chinese family with dilated cardiomyopathy and cardiac conduction disease

Dilated Cardiomyopathy (DCM) and cardiac conduction disease (CCD) are two kinds if diseases that can induce heart failure, syncope and even sudden cardiac death (SCD). DCM patients can experience CCD at the same time. In recent research, some disease-causing genes and variants have been identified in patients with DCM and CCD, such as Alpha-Actinin-2 and TNNI3 Interacting Kinase (TNNI3K). In this study, we employed whole-exome sequencing (WES) to explore the potential causative genes in a Chinese family with DCM and CCD. A novel splice site mutation (c.333 + 2 T > C) of TNNI3K was identified and co-segregated with the affected family members. This novel mutation was also absent in 200 healthy local controls and predicted to be disease-causing by Mutationtaster. The splice site mutation (c.333 + 2 T > C) may result in a premature stop codon in exon 4 of the TNNI3K gene and can induce nonsense-mediated mRNA decay. Real-time qPCR also confirmed that the level of TNNI3K mRNA expression was decreased significantly compared with the controls, which may lead to myocardial structural disorder and arrhythmia. In this study we reported the third novel mutation of TNNI3K in DCM and CCD patients which further supported the important role of TNNI3K in heart development and expanded the spectrum of TNNI3K mutations. The results may contribute to the genetic diagnosis and counseling of families with DCM and CCD.