Missense mutations in the rod domain of the lamin A/C gene as causes of dilated cardiomyopathy and conduction-system disease

Perinuclear organelle trauma at the nexus of cardiomyopathy pathogenesis arising from loss of function LMNA mutation

Over the past 25 years, nuclear envelope (NE) perturbations have been reported in various experimental models with mutations in the LMNA gene. Although the hypothesis that NE perturbations from LMNA mutations are a fundamental feature of striated muscle damage has garnered wide acceptance, the molecular sequalae provoked by the NE damage and how they underlie disease pathogenesis such as cardiomyopathy (LMNA cardiomyopathy) remain poorly understood. We recently shed light on one such consequence, by employing a cardiomyocyte-specific Lmna deletion in vivo in the adult heart. We observed extensive NE perturbations prior to cardiac function deterioration with collateral damage in the perinuclear space. The Golgi is particularly affected, leading to cytoprotective stress responses that are likely disrupted by the progressive deterioration of the Golgi itself. In this review, we discuss the etiology of LMNA cardiomyopathy with perinuclear 'organelle trauma' as the nexus between NE damage and disease pathogenesis.

Nuclear envelope and chromatin choreography direct cellular differentiation

The nuclear envelope plays an indispensable role in the spatiotemporal organization of chromatin and transcriptional regulation during the intricate process of cell differentiation. This review outlines the distinct regulatory networks between nuclear envelope proteins, transcription factors and epigenetic modifications in controlling the expression of cell lineage-specific genes during differentiation. Nuclear lamina with its associated nuclear envelope proteins organize heterochromatin via Lamina-Associated Domains (LADs), proximal to the nuclear periphery. Since nuclear lamina is mechanosensitive, we critically examine the impact of extracellular forces on differentiation outcomes. The nuclear envelope is spanned by nuclear pore complexes which, in addition to their central role in transport, are associated with chromatin organization. Furthermore, mutations in the nuclear envelope proteins disrupt differentiation, resulting in developmental disorders. Investigating the underlying nuclear envelope controlled regulatory mechanisms of chromatin remodelling during lineage commitment will accelerate our fundamental understanding of developmental biology and regenerative medicine.

High incidence of malignant arrhythmias and heart failure in patients with RBM20-associated cardiomyopathy: A multicenter cohort study and review of the literature

BACKGROUND

Patients with RBM20 cardiomyopathy present with an aggressive phenotype, associated with premature malignant arrhythmias, sudden cardiac death, and progressive heart failure (HF). This study aimed to investigate genotype-phenotype correlations, clinical outcomes, and causes of death in patients with RBM20-associated cardiomyopathy and review the current literature.

METHODS

The cohort included patients with cardiomyopathy harboring pathogenic (P) or likely pathogenic (LP) RBM20 variants. For survival and regression analysis, a control group matched for sex, age, and presence of left ventricular dysfunction was included. Additionally, a comprehensive literature search was conducted.

RESULTS

Sixty-two patients (45 % male, 42 ± 15 years at presentation) were included. We found 11 truncating variants. Patients with truncating variants diagnosed with HF were older compared to patients with missense variants (mean age 62 ± 9 vs. 45 ± 14; p = 0.01). Over a median follow-up duration of 5.0 [1.0-10.5] years, 21 (34 %) patients reached the composite endpoint, with 19 (31 %) patients experiencing malignant ventricular arrhythmia (VA) (mean age 45 ± 15 years, 63 % males). Males exhibited higher risk for the composite endpoint (log-rank p = 0.02), particularly for VA (log-rank p = 0.007). The literature review analyzed 34 studies comprising 678 patients (53 % male). In these studies, 123 (24 %) patients experienced a VA, 58 (12 %) underwent a heart transplant or were treated with LVAD, and 52 (11 %) died.

CONCLUSION

This multicenter study highlights the severe phenotype associated with LP/P RBM20 variants, with a high incidence of VA, particularly in males. Additionally, this study presents 11 truncating variants mainly observed in older individuals.

Rare Variation in LMNA Underlies Polycystic Ovary Syndrome Pathogenesis in 2 Independent Cohorts

CONTEXT

Polycystic ovary syndrome (PCOS) is a common, heritable endocrinopathy that is a common cause of anovulatory infertility in reproductive age women. Variants in LMNA cause partial lipodystrophy, a syndrome with overlapping features to PCOS.

OBJECTIVE

We tested the hypothesis that rare variation in LMNA contributes to PCOS pathogenesis and selects a lipodystrophy-like subtype of PCOS.

METHODS

We sequenced LMNA by targeted sequencing a Discovery cohort of 811 PCOS patients and 164 healthy controls. We then analyzed LMNA from whole-exome sequencing of a Replication cohort of 718 PCOS patients and 281 healthy controls. We evaluated variation in the LMNA gene and hormone and lipid profiles of participants.

RESULTS

In the Discovery cohort, we identified 8 missense variants in 15/811 cases, and 1 variant in 1/172 reproductively healthy controls. There is strong evidence for association between the variants and PCOS compared to gnomAD non-Finnish European population controls (χ2 = 17, P = 3.7 × 10-5, OR = 2.9). In the Replication cohort, we identified 11 unique variants in 15/718 cases, and 1 variant in 281 reproductively healthy controls. Again, there is strong evidence for association with population controls (χ2 = 30.5, P = 3.4 × 10-8, OR = 4.0). In both the Discovery and Replication cohorts, variants in LMNA identify women with PCOS with high triglycerides and extreme insulin resistance.

CONCLUSION

Rare missense variation in LMNA is reproducibly associated with PCOS and identifies some individuals with lipodystrophy-like features. The overlap between this PCOS phenotype and genetic partial lipodystrophy syndromes warrants further investigation into additional lipodystrophy genes and their potential in PCOS etiology.

Olmesartan Restores LMNA Function in Haploinsufficient Cardiomyocytes

BACKGROUND

Gene mutations are responsible for a sizeable proportion of cases of heart failure. However, the number of patients with any specific mutation is small. Repositioning of existing US Food and Drug Administration-approved compounds to target specific mutations is a promising approach to efficient identification of new therapies for these patients.

METHODS

The National Institutes of Health Library of Integrated Network-Based Cellular Signatures database was interrogated to identify US Food and Drug Administration-approved compounds that demonstrated the ability to reverse the transcriptional effects of LMNA knockdown. Top hits from this screening were validated in vitro with patient-specific induced pluripotent stem cell-derived cardiomyocytes combined with force measurement, gene expression profiling, electrophysiology, and protein expression analysis.

RESULTS

Several angiotensin receptor blockers were identified from our in silico screen. Of these, olmesartan significantly elevated the expression of sarcomeric genes and rate and force of contraction and ameliorated arrhythmogenic potential. In addition, olmesartan exhibited the ability to reduce phosphorylation of extracellular signal-regulated kinase 1 in LMNA-mutant induced pluripotent stem cell-derived cardiomyocytes.

CONCLUSIONS

In silico screening followed by in vitro validation with induced pluripotent stem cell-derived models can be an efficient approach to identifying repositionable therapies for monogenic cardiomyopathies.

Cardiac phenotypes in LMNA mutations

PURPOSE OF REVIEW

This review highlights the diverse cardiac manifestations of LMNA mutations, focusing on their underlying molecular mechanisms and clinical implications. As LMNA mutations are implicated in cardiomyopathies, such as dilated cardiomyopathy (DCM), arrhythmogenic cardiomyopathy (ARVC), and conduction system diseases, understanding these phenotypes is critical for advancing diagnosis and management strategies.

RECENT FINDINGS

Recent studies reveal that LMNA mutations disrupt nuclear envelope stability, activating the DNA damage response (DDR) and compromising chromatin organization and mechanotransduction. Mouse models have elucidated pathways linking LMNA dysfunction to fibrosis, arrhythmias, and myocardial remodeling. Emerging evidence demonstrates that fibroblasts play a crucial role in cardiac phenotypes. Advances in genetic screening have also underscored the importance of early identification and risk stratification, particularly for arrhythmias and sudden cardiac death.

SUMMARY

The diverse spectrum of LMNA-related cardiac phenotypes, from isolated conduction defects to severe DCM and ARVC, underscores the necessity of personalized care strategies. Bridging insights from molecular studies and clinical research paves the way for targeted therapies to slow disease progression and improve patient outcomes. Future efforts should prioritize translational research on molecular mechanisms with potential in mouse models, alongside a deeper exploration of genotype-phenotype correlations, to refine and implement effective therapeutic interventions.

A genetic variant in SMAD7 acts as a modifier of LMNA-associated muscular dystrophy, implicating SMAD signaling as a therapeutic target

Mutations in LMNA cause multiple types of muscular dystrophy (LMNA-MD). The symptoms of LMNA-MD are highly variable and sensitive to genetic background. To identify genetic contributions to this phenotypic variability, we performed whole-genome sequencing on four siblings possessing the same LMNA mutation with differing degrees of skeletal muscle disease severity. We identified a variant in SMAD7 that segregated with severe muscle disease. To functionally test the SMAD7 variant, we generated a Drosophila model possessing the LMNA mutation and the SMAD7 variant in the orthologous fly genes. The SMAD7 variant increased SMAD signaling and enhanced muscle defects caused by the mutant lamin. Conversely, overexpression of wild-type SMAD7 rescued muscle function. These findings were extended to humans by showing that SMAD signaling is increased in muscle biopsy tissue from individuals with LMNA-MD compared to age-matched controls. Collectively, our findings support SMAD7 as the first functionally tested genetic modifier for LMNA-MD and suggest components of the SMAD pathway as therapeutic targets.

Dilated cardiomyopathy: from genes and molecules to potential treatments

Dilated cardiomyopathy is a myocardial condition marked by the enlargement of the heart's ventricular chambers and the gradual decline in systolic function, frequently resulting in congestive heart failure. Dilated cardiomyopathy has obvious familial characteristics, and mutations in related pathogenic genes can account for about 50% of patients with dilated cardiomyopathy. The most common genes related to dilated cardiomyopathy include TTN, LMNA, MYH7, etc. With more and more research on these genes, it will undoubtedly provide more potential targets and therapeutic pathways for the treatment of dilated cardiomyopathy. In addition, myocardial inflammation, myocardial metabolism abnormalities and cardiomyocyte apoptosis all have an important impact on the pathogenesis of dilated cardiomyopathy. Approximately half of sudden deaths among children and adolescents, along with the majority of patients undergoing heart transplantation, stem from cardiomyopathy. Therefore, precise and prompt clinical diagnosis holds paramount importance. Currently, diagnosis primarily hinges on the patient's medical background and imaging tests, with the significance of genetic testing steadily gaining prominence. The primary treatment for dilated cardiomyopathy remains heart transplantation. However, the scarcity of donors and the risk of severe immune rejection underscore the pressing need for novel therapies. Presently, research is actively exploring preclinical treatments like stem cell therapy as potential solutions.

Discovery of therapeutic targets in cardiovascular diseases using high-throughput chromosome conformation capture (Hi-C)

Epigenetic changes have been associated with several cardiovascular diseases. In recent years, epigenetic inheritance based on spatial changes has gradually attracted attention. Alterations in three-dimensional chromatin structures have been shown to regulate gene expression and influence disease onset and progression. High-throughput Chromosome Conformation Capture (Hi-C) is a powerful method to detect spatial chromatin conformation changes. Since its development, Hi-C technology has been widely adopted for discovering novel therapeutic targets in cardiovascular research. In this review, we summarize key targets identified by Hi-C in cardiovascular diseases and discuss their potential implications for epigenetic therapy.

Genomics of pediatric cardiomyopathy

Cardiomyopathy in children is a leading cause of heart failure and cardiac transplantation. Disease-associated genetic variants play a significant role in the development of the different subtypes of disease. Genetic testing is increasingly being recognized as the standard of care for diagnosing this heterogeneous group of disorders, guiding management, providing prognostic information, and facilitating family-based risk stratification. The increase in clinical and research genetic testing within the field has led to new insights into this group of disorders. Mutations in genes encoding sarcomere, cytoskeletal, Z-disk, and sarcolemma proteins appear to play a major role in causing the overlapping clinical phenotypes called cardioskeletal myopathies through "final common pathway" links. For myocarditis, the high frequency of infectious exposures and wide spectrum of presentation suggest that genetic factors mediate the development and course of the disease, including genetic risk alleles, an association with cardiomyopathy, and undiagnosed arrhythmogenic cardiomyopathy. Finally, while we have made strides in elucidating the genetic architecture of pediatric cardiomyopathy, understanding the clinical implications of variants of uncertain significance remains a major issue. The need for continued genetic innovation in this field remains great, particularly as a basis to drive forward targeted precision medicine and gene therapy efforts. IMPACT: Cardiomyopathy and skeletal myopathy can occur in the same patient secondary to gene mutations that encode for sarcomeric or cytoskeletal proteins, which are expressed in both muscle groups, highlighting that there are common final pathways of disease. The heterogeneous presentation of myocarditis is likely secondary to a complex interaction of multiple environmental and genetic factors, suggesting a utility to genetic testing in pediatric patients with myocarditis, particularly those in higher risk groups. Given the high prevalence of variants of uncertain significance in genetic testing, better bioinformatic tools and pipelines are needed to resolve their clinical meaning.

Advances in the study and treatment of genetic cardiomyopathies

Cardiomyopathies are primary disorders of the heart muscle. Three key phenotypes have been defined, based on morphology and arrhythmia burden: hypertrophic cardiomyopathy (HCM), with thickened heart muscle and diastolic dysfunction; dilated cardiomyopathy (DCM), with left ventricular enlargement and systolic dysfunction; and arrhythmogenic cardiomyopathy (ACM), with right, left, or biventricular involvement and arrhythmias out of proportion to systolic dysfunction. Genetic discoveries of the molecular basis of disease are paving the way for greater precision in diagnosis and management and revealing mechanisms that account for distinguishing clinical features. This deeper understanding has propelled the development of new treatments for cardiomyopathies: disease-specific, mechanistically based medicines that counteract pathophysiology, and emergent gene therapies that aim to intercept disease progression and restore cardiac physiology. Together, these discoveries have advanced fundamental insights into cardiac biology and herald a new era for patients with cardiomyopathy.

Extensive cardiac involvement in laminopathies diagnosed in pediatric-aged patients: A single-center study

BACKGROUND

Pathogenic variations in lamin A/C (LMNA) result in a group of inherited conditions termed laminopathies. Cardiac manifestations of laminopathies include atrial and ventricular arrhythmias, atrioventricular conduction disorders, and cardiomyopathy, with or without skeletal muscle involvement. Because of rarity and previous cardiac characterization as adult onset, pediatric data are limited.

OBJECTIVE

This study sought to investigate the natural history of cardiac disease in pediatric patients with pathogenic LMNA variants.

METHODS

We identified patients ≤18 years with genetically confirmed pathogenic variants in LMNA observed at a single center between 2003 and 2024. Clinical phenotypes along with cardiac test results were retrospectively catalogued.

RESULTS

We identified 12 patients with pathogenic LMNA variant with a median age of 4.9 years at diagnosis (interquartile range, 3.7-10.7 years). Of the 12 patients, 9 (75%) were male and 10 (83%) had skeletal muscle involvement. Cardiac manifestations developed in 9 patients (75%) during a median follow-up of 9.5 years (interquartile range, 7.0-13.3 years). Nine patients (75%) had conduction abnormalities or arrhythmias (atrioventricular block, ventricular/atrial tachycardias), and 4 (33%) had cardiovascular implantable electronic devices placed. Two (17%) patients were diagnosed with cardiomyopathy, 1 (8%) requiring heart transplant. Two (17%) patients died during the study.

CONCLUSION

Cardiac involvement, specifically cardiomyopathy and progressive conduction system abnormalities, were common in pediatric patients with pathogenic LMNA variants. Early genetic diagnosis of laminopathies with frequent surveillance for arrhythmias and cardiac dysfunction is necessary for more timely initiation of advanced therapies to prevent adverse events. More comprehensive phenotype-genotype correlation is strongly needed to better understand early cardiac manifestations in laminopathies.

Genotype-phenotype insights of pediatric dilated cardiomyopathy

Dilated cardiomyopathy (DCM) in children is a severe myocardial disease characterized by enlargement of the left ventricle or both ventricles with impaired contractile function. DCM can cause adverse consequences such as heart failure, sudden death, thromboembolism, and arrhythmias. This article reviews the latest advances in genotype and phenotype research in pediatric DCM. With the development of gene sequencing technologies, considerable progress has been made in genetic research on DCM. Research has shown that DCM exhibits notable genetic heterogeneity, with over 100 DCM-related genes identified to date, primarily involving functions such as calcium handling, the cytoskeleton, and ion channels. As human genomic variations are linked to phenotypes, DCM phenotypes are influenced by numerous genetic variations across the entire genome. Children with DCM display high genetic heterogeneity and are characterized by early onset, rapid disease progression, and poor prognosis. The genetic architecture of pediatric DCM markedly differs from that of adult DCM, necessitating analyses through clinical phenotyping, familial cosegregation studies, and functional validation. Clarifying the genotype-phenotype relationship can improve diagnostic accuracy, enhance prognosis, and guide follow-up treatment for genotype-positive and phenotype-negative patients identified through genetic testing, providing new insights for precision medicine. Future research should further explore novel pathogenic genes and mutations and strengthen genotype-phenotype correlation analyses to facilitate precise diagnosis and treatment of DCM in children.

Contemporary Insights into LMNA Cardiomyopathy

PURPOSE OF REVIEW

This review aims to explore how a diagnosis of LMNA-related cardiomyopathy (LMNA-CM) informs clinical management, focusing on the prevention and management of its complications, through practical clinical strategies.

RECENT FINDINGS

Longitudinal studies have enhanced our understanding of the natural history of LMNA-CM including its arrhythmic and non-arrhythmic complications. A LMNA specific ventricular arrhythmia risk prediction strategy has been integrated into clinical practice guidelines. Although less robust, observational studies are shaping gene-specific strategies for mitigating other complications including atrioventricular block, atrial fibrillation and cardiomyopathy, while novel therapies have been evaluated in clinical trials. LMNA-CM follows an aggressive yet generally stereotyped course. Early recognition of anticipated complications allows for more effective prevention and management in both symptomatic and asymptomatic patients.

LMNA-related cardiomyopathy: From molecular pathology to cardiac gene therapy

BACKGROUND

The genetic variants of LMNA cause an array of diseases that often affect the heart. LMNA-related cardiomyopathy exhibits high-penetrance and early-onset phenotypes that lead to late-stage heart failure or lethal arrhythmia. As a subtype of dilated cardiomyopathy and arrhythmogenic cardiomyopathy, LMNA-related cardiac dysfunction is resistant to existing cardiac therapeutic strategies, leaving a major unmet clinical need in cardiomyopathy management.

AIM OF REVIEW

Here we comprehensively summarize current knowledge about the genetic basis, disease models and pathological mechanisms of LMNA-related cardiomyopathy. Recent translational studies were highlighted to indicate new therapeutic modalities such as gene supplementation, gene silencing and genome editing therapy, which offer potential opportunities to overcome the difficulties in the development of specific drugs for this disease.

KEY SCIENTIFIC CONCEPTS OF REVIEW

LMNA-related cardiomyopathy involves many diverse disease mechanisms that preclude small-molecule drugs that target only a small fraction of the mechanisms. Agreeing to this notion, the first-in-human clinical trial for this disease recently reported futility. By contrast, gene therapy offers the new hope to directly intervene LMNA variants and demonstrates a tremendous potential for breakthrough therapy for this disease. Concepts in this review are also applicable to studies of other genetic diseases that lack effective therapeutics.

Noncoding RNA Terc-53 and hyaluronan receptor Hmmr regulate aging in mice

One of the basic questions in the aging field is whether there is a fundamental difference between the aging of lower invertebrates and mammals. A major difference between the lower invertebrates and mammals is the abundancy of noncoding RNAs, most of which are not conserved. We have previously identified a noncoding RNA Terc-53 that is derived from the RNA component of telomerase Terc. To study its physiological functions, we generated two transgenic mouse models overexpressing the RNA in wild-type and early-aging Terc-/- backgrounds. Terc-53 mice showed age-related cognition decline and shortened life span, even though no developmental defects or physiological abnormality at an early age was observed, indicating its involvement in normal aging of mammals. Subsequent mechanistic study identified hyaluronan-mediated motility receptor (Hmmr) as the main effector of Terc-53. Terc-53 mediates the degradation of Hmmr, leading to an increase of inflammation in the affected tissues, accelerating organismal aging. adeno-associated virus delivered supplementation of Hmmr in the hippocampus reversed the cognition decline in Terc-53 transgenic mice. Neither Terc-53 nor Hmmr has homologs in C. elegans. Neither do arthropods express hyaluronan. These findings demonstrate the complexity of aging in mammals and open new paths for exploring noncoding RNA and Hmmr as means of treating age-related physical debilities and improving healthspan.

Chromatin accessibility: biological functions, molecular mechanisms and therapeutic application

The dynamic regulation of chromatin accessibility is one of the prominent characteristics of eukaryotic genome. The inaccessible regions are mainly located in heterochromatin, which is multilevel compressed and access restricted. The remaining accessible loci are generally located in the euchromatin, which have less nucleosome occupancy and higher regulatory activity. The opening of chromatin is the most important prerequisite for DNA transcription, replication, and damage repair, which is regulated by genetic, epigenetic, environmental, and other factors, playing a vital role in multiple biological progresses. Currently, based on the susceptibility difference of occupied or free DNA to enzymatic cleavage, solubility, methylation, and transposition, there are many methods to detect chromatin accessibility both in bulk and single-cell level. Through combining with high-throughput sequencing, the genome-wide chromatin accessibility landscape of many tissues and cells types also have been constructed. The chromatin accessibility feature is distinct in different tissues and biological states. Research on the regulation network of chromatin accessibility is crucial for uncovering the secret of various biological processes. In this review, we comprehensively introduced the major functions and mechanisms of chromatin accessibility variation in different physiological and pathological processes, meanwhile, the targeted therapies based on chromatin dynamics regulation are also summarized.

Advances in research on the relationship between the LMNA gene and human diseases (Review)

The LMNA gene, which is responsible for encoding lamin A/C proteins, is recognized as a primary constituent of the nuclear lamina. This protein serves crucial roles in various cellular physiological activities, including the maintenance of cellular structural stability, regulation of gene expression, mechanosensing and cellular motility. A significant association has been established between the LMNA gene and several major human diseases. Mutations, dysregulated expression of the LMNA gene, and improper processing of its encoded protein can result in a spectrum of pathological conditions. These diseases, collectively termed laminopathies, are directly attributed to LMNA gene dysfunction. The present review examines the recent advancements in research concerning the LMNA gene and its association with human diseases, while exploring its pathological roles. Particular emphasis is placed on the current status of LMNA gene research in the context of tumors. This includes an analysis of the abundance of LMNA alterations in cancer and its interplay with various signaling pathways. The aim of the present review was to provide novel perspectives for studying the development of LMNA‑related diseases and additional theoretical insights for basic and clinical translational research in this field.

Characterization and natural history of patients with LMNA-related dilated cardiomyopathy in the phase 3 REALM-DCM trial

AIMS

LMNA-related dilated cardiomyopathy (DCM) is a rare disease with an incompletely defined phenotype. The phase 3 REALM-DCM trial evaluated a potential disease-modifying therapy for LMNA-related DCM but was terminated due to futility without safety concern. This study utilized pooled data from REALM-DCM to descriptively characterize the phenotype and progression of LMNA-related DCM in a contemporary cohort of patients using common heart failure (HF) measures.

METHODS

REALM-DCM enrolled patients with stable LMNA-related DCM, an implanted cardioverter defibrillator or cardiac resynchronization therapy defibrillator, and New York Heart Association (NYHA) Class II/III HF symptoms.

RESULTS

Between 2018 and 2022, 77 patients took part in REALM-DCM. The median patient age was 53 years (range: 23-72), and 57% were male. Overall, 88% of patients had a pathogenic or likely pathogenic LMNA variant, and 12% had a variant of uncertain significance with a concordant phenotype. Among patients with confirmed sequencing, 55% had a missense variant. Atrial fibrillation was present in 60% of patients; 79% of all patients had NYHA Class II and 21% had NYHA Class III HF symptoms at baseline. Median (range) left ventricular ejection fraction (LVEF), 6 min walk test (6MWT) distance, Kansas City Cardiomyopathy Questionnaire Overall Summary (KCCQ-OS) score and N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentration at baseline were 42% (23-62), 403 m (173-481), 67 (18-97) and 866 pg/mL (57-5248), respectively. LVEF, 6MWT distance and KCCQ-OS score were numerically lower in patients who had NYHA Class III versus II symptoms at baseline (LVEF: 38% vs. 43%; 6MWT distance: 326 vs. 413 m; and KCCQ-OS score: 43 vs. 70), whereas NT-proBNP concentration was higher (1216 vs. 799 pg/mL). Median follow-up was 73 weeks (range: 0.4-218; 73 in NYHA Class II and 75 in NYHA Class III). Patients displayed variable change from baseline in 6MWT, KCCQ-OS and NT-proBNP values during follow-up. Overall, 25% of patients experienced ventricular tachycardia, and 8% had ventricular fibrillation. Ten (13%) patients met the composite endpoint of worsening HF (adjudicated HF-related hospitalization or urgent care visit) or all-cause death; six had NYHA Class II and four had NYHA Class III at baseline. All-cause mortality occurred in 6 (8%) patients; three had NYHA Class II and three had NYHA Class III symptoms at baseline.

CONCLUSIONS

Findings confirm the significant morbidity and mortality associated with LMNA-related DCM despite the standard of care management. Typical measures of HF, including 6MWT distance, KCCQ-OS score and NT-proBNP concentration, were variable but correlated with NYHA class. An unmet treatment need remains among patients with LMNA-related DCM. NCT03439514.

Much More Than a Stroke: Emery-Dreifuss Muscular Dystrophy Type 2 Revealed by Ischemic Stroke

Emery-Dreifuss muscular dystrophy type 2 (EDMD2) is a rare autosomal dominant neuromuscular disorder caused by LMNA gene mutations and characterized by progressive skeletal muscle weakness and significant cardiac involvement. We report the case of a 45-year-old woman who presented with sudden-onset, left-sided hemiparesis and dysarthria. Initial imaging was unremarkable, and symptoms transiently improved, suggesting a transient ischemic attack. However recurrent deficits led to the identification of right middle cerebral artery occlusion and new-onset atrial fibrillation. Mechanical thrombectomy was successfully performed. Subsequent cardiac evaluation revealed dilated cardiomyopathy with moderately depressed systolic function and segmental wall motion abnormalities, although coronary arteries were normal. Cardiac magnetic resonance imaging demonstrated myocardial fibrosis with late gadolinium enhancement in the subendocardial and mid-wall regions, suggestive of genetic cardiomyopathy. A neurological examination noted lordotic posture, waddling gait, positive Gowers' sign, generalized proximal muscle atrophy, and flaccid hyporeflexic tetraparesis. Electromyography confirmed a proximal myopathy. The patient reported limb weakness since her twenties. Family history was significant for similar neuromuscular and cardiac symptoms. Genetic testing identified a heterozygous LMNA missense variant (ClinVar ID: 804298), confirming the diagnosis of EDMD2. Despite the implantation of a cardiac resynchronization therapy defibrillator and optimal medical management, she experienced recurrent ventricular tachyarrhythmias, necessitating listing for heart transplantation. This case highlights the diagnostic challenges of EDMD2, particularly when the initial presentation is ischemic stroke, a rare manifestation of this genetic myopathy. It underscores the importance of a multidisciplinary approach for early diagnosis and management to improve the outcomes of this rare but impactful disorder.

Dilated Cardiomyopathy: A Genetic Journey from Past to Future

Dilated cardiomyopathy (DCM) is characterized by reduced systolic function and cardiac dilation. Cases without an identified secondary cause are classified as idiopathic dilated cardiomyopathy (IDC). Over the last 35 years, many cases of IDC have increasingly been recognized to be genetic in etiology with a core set of definitively causal genes in up to 40% of cases. While over 200 genes have been associated with DCM, the evidence supporting pathogenicity for most remains limited. Further, rapid advances in sequencing and bioinformatics have recently revealed a complex genetic spectrum ranging from monogenic to polygenic in DCM. These advances have also led to the discovery of causal and modifier genetic variants in secondary forms of DCM (e.g., alcohol-induced cardiomyopathy). Current guidelines recommend genetic counseling and screening, as well as endorsing a handful of genotype-specific therapies (e.g., device placement in LMNA cardiomyopathy). The future of genetics in DCM will likely involve polygenic risk scores, direct-to-consumer testing, and pharmacogenetics, requiring providers to have a thorough understanding of this rapidly developing field. Herein we outline three decades of genetics in DCM, summarize recent advances, and project possible future avenues for the field.

Nuclear envelope budding inhibition slows down progerin-induced aging process

Progerin causes Hutchinson-Gilford progeria syndrome (HGPS), but how progerin accelerates aging is still an interesting question. Here, we provide evidence linking nuclear envelope (NE) budding and accelerated aging. Mechanistically, progerin disrupts nuclear lamina to induce NE budding in concert with lamin A/C, resulting in transport of chromatin into the cytoplasm where it is removed via autophagy, whereas emerin antagonizes this process. Primary cells from both HGPS patients and mouse models express progerin and display NE budding and chromatin loss, and ectopically expressing progerin in cells can mimic this process. More excitingly, we screen a NE budding inhibitor chaetocin by high-throughput screening, which can dramatically sequester progerin from the NE and prevent this NE budding through sustaining ERK1/2 activation. Chaetocin alleviates NE budding-induced chromatin loss and ameliorates HGPS defects in cells and mice and significantly extends lifespan of HGPS mice. Collectively, we propose that progerin-induced NE budding participates in the induction of progeria, highlight the roles of chaetocin and sustained ERK1/2 activation in anti-aging, and provide a distinct avenue for treating HGPS.

Cardiomegaly: Navigating the uncharted territories of heart failure - A multimodal radiological journey through advanced imaging, pathophysiological landscapes, and innovative therapeutic frontiers

Cardiomegaly is among the disorders categorized by a structural enlargement of the heart by any of the situations including pregnancy, resulting in damage to heart muscles and causing trouble in normal heart functioning. Cardiomegaly can be defined in terms of dilatation with an enlarged heart and decreased left or biventricular contraction. The genetic origin of cardiomegaly is becoming more evident due to extensive genomic research opening up new avenues to ensure the use of precision medicine. Cardiomegaly is usually assessed by using an array of radiological modalities, including computed tomography (CT) scans, chest X-rays, and MRIs. These imaging techniques have provided an important opportunity for the physiology and anatomy of the heart. This review aims to highlight the complexity of cardiomegaly, highlighting the contribution of both ecological and genetic variables to its progression. Moreover, we further highlight the worth of precise clinical diagnosis, which comprises blood biomarkers and electrocardiograms (EKG ECG), demonstrating the significance of distinguishing between numerous basic causes. Finally, the analysis highlights the extensive variation of treatment lines, such as lifestyle modifications, prescription drugs, surgery, and implantable devices, although highlighting the critical need for individualized and personalized care.

Intermediate filaments at a glance

Intermediate filaments (IFs) comprise a large family of versatile cytoskeletal proteins, divided into six subtypes with tissue-specific expression patterns. IFs have a wide repertoire of cellular functions, including providing structural support to cells, as well as active roles in mechanical support and signaling pathways. Consequently, defects in IFs are associated with more than 100 diseases. In this Cell Science at a Glance article, we discuss the established classes of IFs and their general features, their functions beyond structural support, and recent advances in the field. We also highlight their involvement in disease and potential use as clinical markers of pathological conditions. Finally, we provide our view on current knowledge gaps and the future directions of the IF field.

The Pathogenic Mechanisms of and Novel Therapies for Lamin A/C-Related Dilated Cardiomyopathy Based on Patient-Specific Pluripotent Stem Cell Platforms and Animal Models

Variants (pathogenic) of the LMNA gene are a common cause of familial dilated cardiomyopathy (DCM), which is characterised by early-onset atrioventricular (AV) block, atrial fibrillation and ventricular tachyarrhythmias (VTs), and progressive heart failure. The unstable internal nuclear lamina observed in LMNA-related DCM is a consequence of the disassembly of lamins A and C. This suggests that LMNA variants produce truncated or alternative forms of protein that alter the nuclear structure and the signalling pathway related to cardiac muscle diseases. To date, the pathogenic mechanisms and phenotypes of LMNA-related DCM have been studied using different platforms, such as patient-specific induced pluripotent stem-cell-derived cardiomyocytes (iPSC-CMs) and transgenic mice. In this review, point variants in the LMNA gene that cause autosomal dominantly inherited forms of LMNA-related DCM are summarised. In addition, potential therapeutic targets based on preclinical studies of LMNA variants using transgenic mice and human iPSC-CMs are discussed. They include mitochondria deficiency, variants in nuclear deformation, chromatin remodelling, altered platelet-derived growth factor and ERK1/2-related pathways, and abnormal calcium handling.

Advanced Heart Failure Therapies in Neuromuscular Diseases

Purpose of Review

The main objective of this review article is to discuss the prevalence, utilization, and outcomes associated with advanced heart failure therapies among patients with neuromuscular disorders.

Recent Findings

Neuromuscular disorders often have multisystem involvement with a high prevalence of cardiovascular pathology. With the improvement in management of respiratory related complications, heart failure is now the leading cause of mortality in this patient population. Advanced heart failure therapies with durable left ventricular assist devices and heart transplantation have proven to be feasible and safe treatment options in selected patients.

Summary

Management of neuromuscular disease involves multidisciplinary team involvement given the systemic nature of the disease. Early recognition and close monitoring of these patients will allow for timely initiation of advanced heart failure therapies that can lead to successful outcomes.

Pervasive nuclear envelope ruptures precede ECM signaling and disease onset without activating cGAS-STING in Lamin-cardiomyopathy mice

Nuclear envelope (NE) ruptures are emerging observations in Lamin-related dilated cardiomyopathy, an adult-onset disease caused by loss-of-function mutations in Lamin A/C, a nuclear lamina component. Here, we test a prevailing hypothesis that NE ruptures trigger the pathological cGAS-STING cytosolic DNA-sensing pathway using a mouse model of Lamin cardiomyopathy. The reduction of Lamin A/C in cardio-myocyte of adult mice causes pervasive NE ruptures in cardiomyocytes, preceding inflammatory transcription, fibrosis, and fatal dilated cardiomyopathy. NE ruptures are followed by DNA damage accumulation without causing immediate cardiomyocyte death. However, cGAS-STING-dependent inflammatory signaling remains inactive. Deleting cGas or Sting does not rescue cardiomyopathy in the mouse model. The lack of cGAS-STING activation is likely due to the near absence of cGAS expression in adult cardiomyocytes at baseline. Instead, extracellular matrix (ECM) signaling is activated and predicted to initiate pro-inflammatory communication from Lamin-reduced cardiomyocytes to fibroblasts. Our work nominates ECM signaling, not cGAS-STING, as a potential inflammatory contributor in Lamin cardiomyopathy.

Multi-level transcriptomic analysis of LMNA -related dilated cardiomyopathy identifies disease-driving processes

LMNA- related dilated cardiomyopathy ( LMNA -DCM) is one of the most severe forms of DCM. The incomplete understanding of the molecular disease mechanisms results in lacking treatment options, leading to high mortality amongst patients. Here, using an inducible, cardiomyocyte-specific lamin A/C depletion mouse model, we conducted a comprehensive transcriptomic study, combining both bulk and single nucleus RNA sequencing, and spanning LMNA -DCM disease progression, to identify potential disease drivers. Our refined analysis pipeline identified 496 genes already misregulated early in disease. The expression of these genes was largely driven by disease specific cardiomyocyte sub-populations and involved biological processes mediating cellular response to DNA damage, cytosolic pattern recognition, and innate immunity. Indeed, DNA damage in LMNA -DCM hearts was significantly increased early in disease and correlated with reduced cardiomyocyte lamin A levels. Activation of cytosolic pattern recognition in cardiomyocytes was independent of cGAS, which is rarely expressed in cardiomyocytes, but likely occurred downstream of other pattern recognition sensors such as IFI16. Altered gene expression in cardiac fibroblasts and immune cell infiltration further contributed to tissue-wide changes in gene expression. Our transcriptomic analysis further predicted significant alterations in cell-cell communication between cardiomyocytes, fibroblasts, and immune cells, mediated through early changes in the extracellular matrix (ECM) in the LMNA -DCM hearts. Taken together, our work suggests a model in which nuclear damage in cardiomyocytes leads to activation of DNA damage responses, cytosolic pattern recognition pathway, and other signaling pathways that activate inflammation, immune cell recruitment, and transcriptional changes in cardiac fibroblasts, which collectively drive LMNA -DCM pathogenesis.

Global Proteomic Analysis Reveals Alterations in Differentially Expressed Proteins between Cardiopathic Lamin A/C Mutations

Lamin A/C (LMNA) is an important component of nuclear lamina. Mutations cause arrhythmia, heart failure, and sudden cardiac death. While LMNA-associated cardiomyopathy typically has an aggressive course that responds poorly to conventional heart failure therapies, there is variability in severity and age of penetrance between and even within specific mutations, which is poorly understood at the cellular level. Further, this heterogeneity has not previously been captured to mimic the heterozygous state, nor have the hundreds of clinical LMNA mutations been represented. Herein, we have overexpressed cardiopathic LMNA variants in HEK cells and utilized state-of-the-art quantitative proteomics to compare the global proteomic profiles of (1) aggregating Q353 K alone, (2) Q353 K coexpressed with WT, (3) aggregating N195 K coexpressed with WT, and (4) nonaggregating E317 K coexpressed with WT to help capture some of the heterogeneity between mutations. We analyzed each data set to obtain the differentially expressed proteins (DEPs) and applied gene ontology (GO) and KEGG pathway analyses. We found a range of 162 to 324 DEPs from over 6000 total protein IDs with differences in GO terms, KEGG pathways, and DEPs important in cardiac function, further highlighting the complexity of cardiac laminopathies. Pathways disrupted by LMNA mutations were validated with redox, autophagy, and apoptosis functional assays in both HEK 293 cells and in induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) for LMNA N195 K. These proteomic profiles expand our repertoire for mutation-specific downstream cellular effects that may become useful as druggable targets for personalized medicine approach for cardiac laminopathies.

In vivo rescue of genetic dilated cardiomyopathy by systemic delivery of nexilin

BACKGROUND

Dilated cardiomyopathy (DCM) is one of the most common causes of heart failure. Multiple identified mutations in nexilin (NEXN) have been suggested to be linked with severe DCM. However, the exact association between multiple mutations of Nexn and DCM remains unclear. Moreover, it is critical for the development of precise and effective therapeutics in treatments of DCM.

RESULTS

In our study, Nexn global knockout mice and mice carrying human equivalent G645del mutation are studied using functional gene rescue assays. AAV-mediated gene delivery is conducted through systemic intravenous injections at the neonatal stage. Heart tissues are analyzed by immunoblots, and functions are assessed by echocardiography. Here, we identify functional components of Nexilin and demonstrate that exogenous introduction could rescue the cardiac function and extend the lifespan of Nexn knockout mouse models. Similar therapeutic effects are also obtained in G645del mice, providing a promising intervention for future clinical therapeutics.

CONCLUSIONS

In summary, we demonstrated that a single injection of AAV-Nexn was capable to restore the functions of cardiomyocytes and extended the lifespan of Nexn knockout and G645del mice. Our study represented a long-term gene replacement therapy for DCM that potentially covers all forms of loss-of-function mutations in NEXN.

Is Cardiac Transplantation Still a Contraindication in Patients with Muscular Dystrophy-Related End-Stage Dilated Cardiomyopathy? A Systematic Review

Inherited muscular diseases (MDs) are genetic degenerative disorders typically caused by mutations in a single gene that affect striated muscle and result in progressive weakness and wasting in affected individuals. Cardiac muscle can also be involved with some variability that depends on the genetic basis of the MD (Muscular Dystrophy) phenotype. Heart involvement can manifest with two main clinical pictures: left ventricular systolic dysfunction with evolution towards dilated cardiomyopathy and refractory heart failure, or the presence of conduction system defects and serious life-threatening ventricular arrhythmias. The two pictures can coexist. In these cases, heart transplantation (HTx) is considered the most appropriate option in patients who are not responders to the optimized standard therapeutic protocols. However, cardiac transplant is still considered a relative contraindication in patients with inherited muscle disorders and end-stage cardiomyopathies. High operative risk related to muscle impairment and potential graft involvement secondary to the underlying myopathy have been the two main reasons implicated in the generalized reluctance to consider cardiac transplant as a viable option. We report an overview of cardiac involvement in MDs and its possible association with the underlying molecular defect, as well as a systematic review of HTx outcomes in patients with MD-related end-stage dilated cardiomyopathy, published so far in the literature.

A bibliometric and visual analysis of research trends and hotspots of familial hypertrophic cardiomyopathy: A review

Familial hypertrophic cardiomyopathy (FHCM) is an inherited cardiac disease caused by mutations of sarcomere proteins and can be the underlining substrate for major cardiovascular events. Early identification and diagnosis of FHCM are essential to reduce sudden cardiac death. So, this paper summarized the current knowledge on FHCM, and displayed the analysis via bibliometrics method. The relevant literature on FHCM were screened searched via the Web of Science Core Collection database from 2012 to 2022. The literatures were was summarized and analyzed via the bibliometrics method analyzed via CiteSpace and VOSviewer according to topic categories, distribution of spatiotemporal omics and authors, as well as references. Since 2012, there are 909 research articles and reviews related to FHCM. The number of publication for the past 10 years have shown that the development of FHCM research has been steady, with the largest amount of literature in 2012. The most published papers were from the United States, followed by the United Kingdom and Italy. The University of London (63 papers) was the institution that published the most research articles, followed by Harvard University (45 papers) and University College London (45 papers). Keywords formed 3 clusters, focused on the pathogenesis of FHCM, the diagnosis of FHCM, FHCM complications, respectively. The bibliometric analysis and visualization techniques employed herein highlight key trends and focal points in the field, predominantly centered around FHCM's pathogenesis, diagnostic approaches, and its complications. These insights are instrumental in steering future research directions in this area.

DNA double-stranded breaks, a hallmark of aging, defined at the nucleotide resolution, are increased and associated with transcription in the cardiac myocytes in LMNA-cardiomyopathy

AIMS

An intrinsic feature of gene transcription is the formation of DNA superhelices near the transcription bubble, which are resolved upon induction of transient double-stranded breaks (DSBs) by topoisomerases. Unrepaired DSBs are pathogenic as they lead to cell cycle arrest, senescence, inflammation, and organ dysfunction. We posit that DSBs would be more prevalent at the genomic sites that are associated with gene expression. The objectives were to identify and characterize genome-wide DSBs at the nucleotide resolution and determine the association of DSBs with transcription in cardiac myocytes.

METHODS AND RESULTS

We identified the genome-wide DSBs in ∼1 million cardiac myocytes per heart in three wild-type and three myocyte-specific LMNA-deficient (Myh6-Cre:LmnaF/F) mice by END-Sequencing. The prevalence of DSBs was 0.8% and 2.2% in the wild-type and Myh6-Cre:LmnaF/F myocytes, respectively. The END-Seq signals were enriched for 8 and 6764 DSBs in the wild-type and Myh6-Cre:LmnaF/F myocytes, respectively (q < 0.05). The DSBs were preferentially localized to the gene regions, transcription initiation sites, cardiac transcription factor motifs, and the G quadruplex forming structures. Because LMNA regulates transcription through the lamin-associated domains (LADs), we defined the LADs in cardiac myocytes by a Cleavage Under Targets & Release Using Nuclease (CUT&RUN) assay (N = 5). On average there were 818 LADs per myocyte. Constitutive LADs (cLADs), defined as LADs that were shared by at least three genomes (N = 2572), comprised about a third of the mouse cardiac myocyte genomes. Transcript levels of the protein-coding genes located at the cLADs (N = 3975) were ∼16-fold lower than those at the non-LAD regions (N = ∼17 778). The prevalence of DSBs was higher in the non-LAD as compared to the cLAD regions. Likewise, DSBs were more common in the loss-of-LAD regions, defined as the genomic regions in the Myh6-Cre:LmnaF/F that were juxtaposed to the LAD regions in the wild-type myocytes.

CONCLUSION

To our knowledge, this is the first identification of the DSBs, at the nucleotide resolution in the cardiovascular system. The prevalence of DSBs was higher in the genomic regions associated with transcription. Because transcription is pervasive, DSBs are expected to be common and pathogenic in various states and aging.

Skeletal Muscle Involvement in Patients With Truncations of Titin and Familial Dilated Cardiomyopathy

BACKGROUND

Genetic variants in titin (TTN) are associated with dilated cardiomyopathy (DCM) and skeletal myopathy. However, the skeletal muscle phenotype in individuals carrying heterozygous truncating TTN variants (TTNtv), the leading cause of DCM, is understudied.

OBJECTIVES

This study aimed to assess the skeletal muscle phenotype associated with TTNtv.

METHODS

Participants with TTNtv were included in a cross-sectional study. Skeletal muscle fat fraction was evaluated by magnetic resonance imaging (compared with healthy controls and controls with non-TTNtv DCM). Muscle strength was evaluated by dynamometry and muscle biopsy specimens were analyzed.

RESULTS

Twenty-five TTNtv participants (11 women, mean age 51 ± 15 years, left ventricular ejection fraction 45% ± 10%) were included (19 had DCM). Compared to healthy controls (n = 25), fat fraction was higher in calf (12.5% vs 9.9%, P = 0.013), thigh (12.2% vs 9.3%, P = 0.004), and paraspinal muscles (18.8% vs 13.9%, P = 0.008) of TTNtv participants. Linear mixed effects modelling found higher fat fractions in TTNtv participants compared to healthy controls (2.5%; 95% CI: 1.4-3.7; P < 0.001) and controls with non-TTNtv genetic DCM (n = 7) (1.5%; 95% CI: 0.2-2.8; P = 0.025). Muscle strength was within 1 SD of normal values. Biopsy specimens from 21 participants found myopathic features in 13 (62%), including central nuclei. Electron microscopy showed well-ordered Z-lines and T-tubuli but uneven and discontinuous M-lines and excessive glycogen depositions flanked by autophagosomes, lysosomes, and abnormal mitochondria with mitophagy.

CONCLUSIONS

Mild skeletal muscle involvement was prevalent in patients with TTNtv. The phenotype was characterized by an increased muscle fat fraction and excessive accumulation of glycogen, possibly due to reduced autophagic flux. These findings indicate an impact of TTNtv beyond the heart.

The structure and function of lamin A/C: Special focus on cardiomyopathy and therapeutic interventions

Lamins are inner nuclear membrane proteins that belong to the intermediate filament family. Lamin A/C lie adjacent to the heterochromatin structure in polymer form, providing skeletal to the nucleus. Based on the localization, lamin A/C provides nuclear stability and cytoskeleton to the nucleus and modulates chromatin organization and gene expression. Besides being the structural protein making the inner nuclear membrane in polymer form, lamin A/C functions as a signalling molecule involved in gene expression as an enhancer inside the nucleus. Lamin A/C regulates various cellular pathways like autophagy and energy balance in the cytoplasm. Its expression is highly variable in differentiated tissues, higher in hard tissues like bone and muscle cells, and lower in soft tissues like the liver and brain. In muscle cells, including the heart, lamin A/C must be expressed in a balanced state. Lamin A/C mutation is linked with various diseases, such as muscular dystrophy, lipodystrophy, and cardiomyopathies. It has been observed that a good number of mutations in the LMNA gene impact cardiac activity and its function. Although several works have been published, there are still several unexplored areas left regarding the lamin A/C function and structure in the cardiovascular system and its pathological state. In this review, we focus on the structural organization, expression pattern, and function of lamin A/C, its interacting partners, and the pathophysiology associated with mutations in the lamin A/C gene, with special emphasis on cardiovascular diseases. With the recent finding on lamin A/C, we have summarized the possible therapeutic interventions to treat cardiovascular symptoms and reverse the molecular changes.

Lamin A K97E leads to NF-κB-mediated dysfunction of inflammatory responses in dilated cardiomyopathy

BACKGROUND INFORMATION

Lamins are type V intermediate filament proteins underlying the inner nuclear membrane which provide structural rigidity to the nucleus, tether the chromosomes, maintain nuclear homeostasis, and remain dynamically associated with developmentally regulated regions of the genome. A large number of mutations particularly in the LMNA gene encoding lamin A/C results in a wide array of human diseases, collectively termed as laminopathies. Dilated Cardiomyopathy (DCM) is one such laminopathic cardiovascular disease which is associated with systolic dysfunction of left or both ventricles leading to cardiac arrhythmia which ultimately culminates into myocardial infarction.

RESULTS

In this work, we have unraveled the epigenetic landscape to address the regulation of gene expression in mouse myoblast cell line in the context of the missense mutation LMNA 289A

CONCLUSIONS

We report here for the first time that there is a significant downregulation of the NF-κB pathway, which has been implicated in cardio-protection elsewhere.

SIGNIFICANCE

This provides a new pathophysiological explanation that correlates an LMNA mutation and dilated cardiomyopathy.

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Key Words

• NF‐κB signaling
• dilated cardiomyopathy
• epigenetic modifications
• interleukins
• lamin A

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MESH Headings

• Mice
• Animals
• Humans
• Cardiomyopathy, Dilated/genetics
• Cardiomyopathy, Dilated/metabolism
• Lamin Type A/genetics
• Lamin Type A/chemistry
• Lamin Type A/metabolism
• NF-kappa B/genetics
• NF-kappa B/metabolism
• Mutation
• Nuclear Lamina

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Grants

• Department of Atomic Energy, Government of India

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Affiliation(s)

Duhita Sengupta Biophysics and Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India Homi Bhabha National Institute (HBNI), Mumbai, India
Kaushik Sengupta Biophysics and Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India Homi Bhabha National Institute (HBNI), Mumbai, India

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Collaborators Collapse

A Clinical Diagnosis of Laminopathy without Systolic Dysfunction: When Does Nuclei Malformation Start?

Nuclear shape abnormalities in laminopathy are well known to occur in patients with cardiac systolic dysfunction. However, those in patients without systolic dysfunction are still unclear. We herein report a 42-year-old man who presented with advanced atrioventricular block without systolic dysfunction. Genetic testing identified a laminopathic mutation, c.497G>C, and an endocardial biopsy was performed. The hyperperfine structure on electron microscopy showed malformation of the nuclei, euchromatic nucleoplasm, and partial existence of heterochromatin clumps. Intrusion of heterochromatin into the nuclear fibrous lamina was observed. Cardiomyocyte nuclear shape abnormalities were observed before the progression of systolic dysfunction.

Sex-specific preservation of neuromuscular function and metabolism following systemic transplantation of multipotent adult stem cells in a murine model of progeria

Onset and rates of sarcopenia, a disease characterized by a loss of muscle mass and function with age, vary greatly between sexes. Currently, no clinical interventions successfully arrest age-related muscle impairments since the decline is frequently multifactorial. Previously, we found that systemic transplantation of our unique adult multipotent muscle-derived stem/progenitor cells (MDSPCs) isolated from young mice-but not old-extends the health-span in DNA damage mouse models of progeria, a disease of accelerated aging. Additionally, induced neovascularization in the muscles and brain-where no transplanted cells were detected-strongly suggests a systemic therapeutic mechanism, possibly activated through circulating secreted factors. Herein, we used ZMPSTE24-deficient mice, a lamin A defect progeria model, to investigate the ability of young MDSPCs to preserve neuromuscular tissue structure and function. We show that progeroid ZMPST24-deficient mice faithfully exhibit sarcopenia and age-related metabolic dysfunction. However, systemic transplantation of young MDSPCs into ZMPSTE24-deficient progeroid mice sustained healthy function and histopathology of muscular tissues throughout their 6-month life span in a sex-specific manner. Indeed, female-but not male-mice systemically transplanted with young MDSPCs demonstrated significant preservation of muscle endurance, muscle fiber size, mitochondrial respirometry, and neuromuscular junction morphometrics. These novel findings strongly suggest that young MDSPCs modulate the systemic environment of aged animals by secreted rejuvenating factors to maintain a healthy homeostasis in a sex-specific manner and that the female muscle microenvironment remains responsive to exogenous regenerative cues in older age. This work highlights the age- and sex-related differences in neuromuscular tissue degeneration and the future prospect of preserving health in older adults with systemic regenerative treatments.

Genetics of Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is defined as dilation and/or reduced function of one or both ventricles and remains a common disease worldwide. An estimated 40% of cases of familial DCM have an identifiable genetic cause. Accordingly, there is a fast-growing interest in the field of molecular genetics as it pertains to DCM. Many gene mutations have been identified that contribute to phenotypically significant cardiomyopathy. DCM genes can affect a variety of cardiomyocyte functions, and particular genes whose function affects the cell-cell junction and cytoskeleton are associated with increased risk of arrhythmias and sudden cardiac death. Through advancements in next-generation sequencing and cardiac imaging, identification of genetic DCM has improved over the past couple decades, and precision medicine is now at the forefront of treatment for these patients and their families. In addition to standard treatment of heart failure and prevention of arrhythmias and sudden cardiac death, patients with genetic cardiomyopathy stand to benefit from gene mechanism-specific therapies.

Case Report: Four cases of cardiac sarcoidosis in patients with inherited cardiomyopathy-a phenotypic overlap, co-existence of two rare cardiomyopathies or a second-hit disease

Cardiac sarcoidosis (CS), a rare condition characterized by non-caseating granulomas, can manifest with symptoms such as atrioventricular block and ventricular tachycardia (VT), as well as mimic inherited cardiomyopathies. A 48-year-old male presented with recurrent VT. The initial 18F-fluorodeoxyglucose positron emission tomography (18FDG-PET) scan showed uptake of the mediastinal lymph node. Cardiovascular magnetic resonance (CMR) demonstrated intramyocardial fibrosis. The follow-up 18FDG-PET scan revealed the presence of tracer uptake in the left ventricular (LV) septum, suggesting the likelihood of CS. Genetic testing identified a pathogenic LMNA variant. A 47-year-old female presented with complaints of palpitations and syncope. An Ajmaline provocation test confirmed Brugada syndrome (BrS). CMR revealed signs of cardiac inflammation. An endomyocardial biopsy (EMB) confirmed the diagnosis of cardiac sarcoidosis. Polymorphic VT was induced during an electrophysiological study, and an implantable cardioverter-defibrillator (ICD) was implanted. A 58-year-old woman presented with sustained VT with a prior diagnosis of hypertrophic cardiomyopathy (HCM). A genetic work-up identified the presence of a heterozygous MYBC3 variant of unknown significance (VUS). CMR revealed late gadolinium enhancement (LGE), while the 18FDG-PET scan demonstrated LV tracer uptake. The immunosuppressive therapy was adjusted, and no further VTs were observed. A 28-year-old male athlete with right ventricular dilatation and syncope experienced a cardiac arrest during training. Genetic testing identified a pathogenic mutation in PKP2. The autopsy has confirmed the presence of ACM and a distinctive extracardiac sarcoidosis. Cardiac sarcoidosis and inherited cardiomyopathies may interact in several different ways, altering the clinical presentation. Overlapping pathologies are frequently overlooked. Delayed or incomplete diagnosis risks inadequate treatment. Thus, genetic testing and endomyocardial biopsies should be recommended to obtain a clear diagnosis.

Comprehensive review on gene mutations contributing to dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is one of the most common primary myocardial diseases. However, to this day, it remains an enigmatic cardiovascular disease (CVD) characterized by ventricular dilatation, which leads to myocardial contractile dysfunction. It is the most common cause of chronic congestive heart failure and the most frequent indication for heart transplantation in young individuals. Genetics and various other factors play significant roles in the progression of dilated cardiomyopathy, and variants in more than 50 genes have been associated with the disease. However, the etiology of a large number of cases remains elusive. Numerous studies have been conducted on the genetic causes of dilated cardiomyopathy. These genetic studies suggest that mutations in genes for fibronectin, cytoskeletal proteins, and myosin in cardiomyocytes play a key role in the development of DCM. In this review, we provide a comprehensive description of the genetic basis, mechanisms, and research advances in genes that have been strongly associated with DCM based on evidence-based medicine. We also emphasize the important role of gene sequencing in therapy for potential early diagnosis and improved clinical management of DCM.

Case report: A new de novo mutation of the Troponin T2 gene in a Chinese patient with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a cardiovascular disease characterized by persistent ventricular dilatation and systolic dysfunction. DCM has a variety of causes, including myocarditis; exposure to narcotics, alcohol, or other toxins; and metabolic or endocrine disorders. Genetic factors play a dominant role in 30%-40% of DCM cases. Here, we report a case of DCM with very severe heart failure. Because of the severity of heart failure, the patient underwent heart transplantation. We speculated that the patient's DCM might be due to a mutation; hence, we performed whole-exome sequencing of the patient and their parents, which showed a de novo heterozygous mutation (NM_001001431.2c.769G>A:p.E257K) in TNNT2, which was considered pathogenic according to the ACMG pathogenicity assessment. This finding expands the genetic map of DCM and TNNT2 and will be important for future studies on the genetic and disease relationships between DCM and TNNT2.