Patrón fenotípico de las miocardiopatías por mutaciones en el gen de la desmina. Estudio clínico y genético en dos unidades de cardiopatías familiares

Genetic Insights into Primary Restrictive Cardiomyopathy

Restrictive cardiomyopathy is a rare cardiac disease causing severe diastolic dysfunction, ventricular stiffness and dilated atria. In consequence, it induces heart failure often with preserved ejection fraction and is associated with a high mortality. Since it is a poor clinical prognosis, patients with restrictive cardiomyopathy frequently require heart transplantation. Genetic as well as non-genetic factors contribute to restrictive cardiomyopathy and a significant portion of cases are of unknown etiology. However, the genetic forms of restrictive cardiomyopathy and the involved molecular pathomechanisms are only partially understood. In this review, we summarize the current knowledge about primary genetic restrictive cardiomyopathy and describe its genetic landscape, which might be of interest for geneticists as well as for cardiologists.

The Novel Desmin Variant p.Leu115Ile Is Associated With a Unique Form of Biventricular Arrhythmogenic Cardiomyopathy

BACKGROUND

Arrhythmogenic cardiomyopathy (AC) is a heritable myocardial disorder and a major cause of sudden cardiac death. It is typically caused by mutations in desmosomal genes. Desmin gene (DES) variants have been previously reported in AC but with insufficient evidence to support their pathogenicity.

METHODS

We aimed to assess a large AC patient cohort for DES mutations and describe a unique phenotype associated with a recurring variant in three families. A cohort of 138 probands with a diagnosis of AC and no identifiable desmosomal gene mutations were prospectively screened by whole-exome sequencing.

RESULTS

A single DES variant (p.Leu115Ile, c.343C>A) was identified in 3 index patients (2%). We assessed the clinical phenotypes within their families and confirmed cosegregation. One carrier required heart transplantation, 2 died suddenly, and 1 died of noncardiac causes. All cases had right- and left-ventricular (LV) involvement. LV late gadolinium enhancement was present in all, and circumferential subepicardial distribution was confirmed on histology. A significant burden of ventricular arrhythmias was noted. Desmin aggregates were not observed macroscopically, but analysis of the desmin filament formation in transfected cardiomyocytes derived from induced pluripotent stem cells, and SW13 cells revealed cytoplasmic aggregation of mutant desmin. Atomic force microscopy revealed that the mutant form accumulates into short protofilaments and small fibrous aggregates.

CONCLUSIONS

DES p.Leu115Ile leads to disruption of the desmin filament network and causes a malignant biventricular form of AC, characterized by LV dysfunction and a circumferential subepicardial distribution of myocardial fibrosis.

Cardiomyopathy in Children: Classification and Diagnosis: A Scientific Statement From the American Heart Association

In this scientific statement from the American Heart Association, experts in the field of cardiomyopathy (heart muscle disease) in children address 2 issues: the most current understanding of the causes of cardiomyopathy in children and the optimal approaches to diagnosis cardiomyopathy in children. Cardiomyopathies result in some of the worst pediatric cardiology outcomes; nearly 40% of children who present with symptomatic cardiomyopathy undergo a heart transplantation or die within the first 2 years after diagnosis. The percentage of children with cardiomyopathy who underwent a heart transplantation has not declined over the past 10 years, and cardiomyopathy remains the leading cause of transplantation for children >1 year of age. Studies from the National Heart, Lung, and Blood Institute-funded Pediatric Cardiomyopathy Registry have shown that causes are established in very few children with cardiomyopathy, yet genetic causes are likely to be present in most. The incidence of pediatric cardiomyopathy is ≈1 per 100 000 children. This is comparable to the incidence of such childhood cancers as lymphoma, Wilms tumor, and neuroblastoma. However, the published research and scientific conferences focused on pediatric cardiomyopathy are sparcer than for those cancers. The aim of the statement is to focus on the diagnosis and classification of cardiomyopathy. We anticipate that this report will help shape the future research priorities in this set of diseases to achieve earlier diagnosis, improved clinical outcomes, and better quality of life for these children and their families.

A novel phenotype with splicing mutation identified in a Chinese family with desminopathy

BACKGROUND

Desminopathy, a hereditary myofibrillar myopathy, mainly results from the desmin gene (DES) mutations. Desminopathy involves various phenotypes, mainly including different cardiomyopathies, skeletal myopathy, and arrhythmia. Combined with genotype, it helps us precisely diagnose and treat for desminopathy.

METHODS

Sanger sequencing was used to characterize DES variation, and then a minigene assay was used to verify the effect of splice-site mutation on pre-mRNA splicing. Phenotypes were analyzed based on clinical characteristics associated with desminopathy.

RESULTS

A splicing mutation (c.735+1G>T) in DES was detected in the proband. A minigene assay revealed skipping of the whole exon 3 and transcription of abnormal pre-mRNA lacking 32 codons. Another affected family member who carried the identical mutation, was identified with a novel phenotype of desminopathy, non-compaction of ventricular myocardium. There were 2 different phenotypes varied in cardiomyopathy and skeletal myopathy among the 2 patients, but no significant correlation between genotype and phenotype was identified.

CONCLUSIONS

We reported a novel phenotype with a splicing mutation in DES, enlarging the spectrum of phenotype in desminopathy. Molecular studies of desminopathy should promote our understanding of its pathogenesis and provide a precise molecular diagnosis of this disorder, facilitating clinical prevention and treatment at an early stage.

Molecular and genetic insights into progressive cardiac conduction disease

Progressive cardiac conduction disease (PCCD) is often a primarily genetic disorder, with clinical and genetic overlaps with other inherited cardiac and metabolic diseases. A number of genes have been implicated in PCCD pathogenesis with or without structural heart disease or systemic manifestations. Precise genetic diagnosis contributes to risk stratification, better selection of specific therapy and allows familiar cascade screening. Cardiologists should be aware of the different phenotypes emerging from different gene-mutations and the potential risk of sudden cardiac death. Genetic forms of PCCD often overlap or coexist with other inherited heart diseases or manifest in the context of multisystem syndromes. Despite the significant advances in the knowledge of the genetic architecture of PCCD and overlapping diseases, in a measurable fraction of PCCD cases, including in familial clustering of disease, investigations of known cardiac disease-associated genes fail to reveal the underlying substrate, suggesting that new causal genes are yet to be discovered. Here, we provide insight into genetics and molecular mechanisms of PCCD and related diseases. We also highlight the phenotypic overlaps of PCCD with other inherited cardiac and metabolic diseases, present unmet challenges in clinical practice, and summarize the available therapeutic options for affected patients.

Translating emerging molecular genetic insights into clinical practice in inherited cardiomyopathies

Cardiomyopathies are primarily genetic disorders of the myocardium associated with higher risk of life-threatening cardiac arrhythmias, heart failure, and sudden cardiac death. The evolving knowledge in genomic medicine during the last decade has reshaped our understanding of cardiomyopathies as diseases of multifactorial nature and complex pathophysiology. Genetic testing in cardiomyopathies has subsequently grown from primarily a research tool into an essential clinical evaluation piece with important clinical implications for patients and their families. The purpose of this review is to provide with a contemporary insight into the implications of genetic testing in diagnosis, therapy, and prognosis of patients with inherited cardiomyopathies. Here, we summarize the contemporary knowledge on genotype-phenotype correlations in inherited cardiomyopathies and highlight the recent significant achievements in the field of translational cardiovascular genetics.

Molecular insights into cardiomyopathies associated with desmin (DES) mutations

Increasing usage of next-generation sequencing techniques pushed during the last decade cardiogenetic diagnostics leading to the identification of a huge number of genetic variants in about 170 genes associated with cardiomyopathies, channelopathies, or syndromes with cardiac involvement. Because of the biochemical and cellular complexity, it is challenging to understand the clinical meaning or even the relevant pathomechanisms of the majority of genetic sequence variants. However, detailed knowledge about the associated molecular pathomechanism is essential for the development of efficient therapeutic strategies in future and genetic counseling. Mutations in DES, encoding the muscle-specific intermediate filament protein desmin, have been identified in different kinds of cardiac and skeletal myopathies. Here, we review the functions of desmin in health and disease with a focus on cardiomyopathies. In addition, we will summarize the genetic and clinical literature about DES mutations and will explain relevant cell and animal models. Moreover, we discuss upcoming perspectives and consequences of novel experimental approaches like genome editing technology, which might open a novel research field contributing to the development of efficient and mutation-specific treatment options.

Novel Desmin Mutation p.Glu401Asp Impairs Filament Formation, Disrupts Cell Membrane Integrity, and Causes Severe Arrhythmogenic Left Ventricular Cardiomyopathy/Dysplasia

BACKGROUND

Desmin (DES) mutations cause severe skeletal and cardiac muscle disease with heterogeneous phenotypes. Recently, DES mutations were described in patients with inherited arrhythmogenic right ventricular cardiomyopathy/dysplasia, although their cellular and molecular pathomechanisms are not precisely known. Our aim is to describe clinically and functionally the novel DES-p.Glu401Asp mutation as a cause of inherited left ventricular arrhythmogenic cardiomyopathy/dysplasia.

METHODS

We identified the novel DES mutation p.Glu401Asp in a large Spanish family with inherited left ventricular arrhythmogenic cardiomyopathy/dysplasia and a high incidence of adverse cardiac events. A full clinical evaluation was performed on all mutation carriers and noncarriers to establish clinical and genetic cosegregation. In addition, desmin, and intercalar disc-related proteins expression were histologically analyzed in explanted cardiac tissue affected by the DES mutation. Furthermore, mesenchymal stem cells were isolated and cultured from 2 family members with the DES mutation (1 with mild and 1 with severe symptomatology) and a member without the mutation (control) and differentiated ex vivo to cardiomyocytes. Then, important genes related to cardiac differentiation and function were analyzed by real-time quantitative polymerase chain reaction. Finally, the p.Glu401Asp mutated DES gene was transfected into cell lines and analyzed by confocal microscopy.

RESULTS

Of the 66 family members screened for the DES-p.Glu401Asp mutation, 23 of them were positive, 6 were obligate carriers, and 2 were likely carriers. One hundred percent of genotype-positive patients presented data consistent with inherited arrhythmogenic cardiomyopathy/dysplasia phenotype with variable disease severity expression, high-incidence of sudden cardiac death, and absence of skeletal myopathy or conduction system disorders. Immunohistochemistry was compatible with inherited arrhythmogenic cardiomyopathy/dysplasia, and the functional study showed an abnormal growth pattern and cellular adhesion, reduced desmin RNA expression, and some other membrane proteins, as well, and desmin aggregates in transfected cells expressing the mutant desmin.

CONCLUSIONS

The DES-p.Glu401Asp mutation causes predominant inherited left ventricular arrhythmogenic cardiomyopathy/dysplasia with a high incidence of adverse clinical events in the absence of skeletal myopathy or conduction system disorders. The pathogenic mechanism probably corresponds to an alteration in desmin dimer and oligomer assembly and its connection with membrane proteins within the intercalated disc.