Dystrophin disruption in enterovirus-induced myocarditis and dilated cardiomyopathy: from bench to bedside

Genetic defects of the dystrophin-glycoprotein complex (DGC) cause hereditary dilated cardiomyopathy. Enteroviruses can also cause cardiomyopathy and we have previously described a mechanism involved in enterovirus-induced dilated cardiomyopathy: The enteroviral protease 2A directly cleaves dystrophin in the hinge 3 region, leading to functional dystrophin impairment. During infection of mice with coxsackievirus B3, the DGC in the heart is disrupted and the sarcolemmal integrity is lost in virus-infected cardiomyocytes. Additionally, dystrophin deficiency markedly increases enterovirus-induced cardiomyopathy in vivo, suggesting a pathogenetic role of the dystrophin cleavage in enterovirus-induced cardiomyopathy. Here, we extend these experimental findings to a patient with dilated cardiomyopathy due to a coxsackievirus B2 myocarditis. Endomyocardial biopsy specimens showed an inflammatory infiltrate and myocytolysis. Immunostaining for the enteroviral capsid antigen VP1 revealed virus-infected cardiomyocytes. Focal areas of cardiomyocytes displayed a loss of the sarcolemmal staining pattern for dystrophin and -sarcoglycan identical to previous findings in virus-infected mouse hearts. In vitro, coxsackievirus B2 protease 2A cleaved human dystrophin. These findings demonstrate that in human coxsackievirus B myocarditis a focal disruption of the DGC can principally occur and may contribute to the pathogenesis of human enterovirus-induced dilated cardiomyopathy.     

Investigation of de novo variation in pediatric cardiomyopathy

Pediatric cardiomyopathies can be caused by variants in genes encoding the sarcomere and cytoskeleton in cardiomyocytes. Variants are typically inherited in an autosomal dominant manner with variable expressivity. De novo variants have been reported, however their overall frequency is largely unknown. We sought to determine the rate of de novo, pathogenic and likely pathogenic (P/LP) variants in children with a diagnosis of hypertrophic, dilated, or restrictive cardiomyopathy (HCM, DCM, or RCM), and to compare disease outcomes between individuals with and without a de novo variant. A retrospective record review identified 126 individuals with HCM (55%), DCM (37%), or RCM (8%) ≤18 years of age who had genetic testing. Overall, 50 (40%) had positive genetic testing and 18% of P/LP variants occurred de novo. The rate of de novo variation in those with RCM (80%) was higher than in those with HCM (9%) or DCM (20%). There was evidence of germline mosaicism in one family with RCM. Individuals with de novo variants were more likely than those without to have a history of arrhythmia (p = .049), sudden cardiac arrest (p = .024), hospitalization (p = .041), and cardiac transplantation (p = .030). The likelihood of de novo variation and impact on family risk and screening should be integrated into genetic counseling.     

骨髓间充质干细胞分化为血管内皮细胞的实验研究

目的 :探讨骨髓间充质干细胞 (MSCs)自体移植后在扩张型心肌病(DCM)微环境中分化为血管内皮细胞的可行性。方法 :以日本大耳白兔为研究对象 ,分离培养扩增MSCs,盐酸阿霉素耳缘静脉注射复制兔DCM模型 ,将 5溴脱氧尿嘧啶 (BrdU)标记的MSCs移植到DCM心肌内 ,4周后观察移植细胞的增殖分化情况。结果 :细胞移植 4周后 ,实验组心肌内有BrdU标记的阳性细胞 ,有一部分参与组成新生血管 ,对照组中没有发现 ,且实验组毛细血管密度大于对照组 ,差异具有显著性 (P<0 .0 1)。结论 :MSCs自体移植到扩张型心肌病后可以分化为血管内皮细胞。     

Novel OCTN2 mutations: No genotype–phenotype correlations: Early carnitine therapy prevents cardiomyopathy

Primary systemic carnitine deficiency or carnitine uptake defect (OMIM 212140) is a potentially lethal, autosomal recessive disorder characterized by progressive infantile‐onset cardiomyopathy, weakness, and recurrent hypoglycemic hypoketotic encephalopathy, which is highly responsive to L ‐carnitine therapy. Molecular analysis of the SLC22A5 (OCTN2) gene, encoding the high‐affinity carnitine transporter, was done in 11 affected individuals by direct nucleotide sequencing of polymerase chain reaction products from all 10 exons. Carnitine uptake (at Km of 5 μM) in cultured skin fibroblasts ranged from 1% to 20% of normal controls. Eleven mutations (delF23, N32S, and one 11‐bp duplication in exon 1; R169W in exon 3; a donor splice mutation [IVS3+1 G > A] in intron 3; frameshift mutations in exons 5 and 6; Y401X in exon 7; T440M, T468R and S470F in exon 8) are described. There was no correlation between residual uptake and severity of clinical presentation, suggesting that the wide phenotypic variability is likely related to exogenous stressors exacerbating carnitine deficiency. Most importantly, strict compliance with carnitine from birth appears to prevent the phenotype. © 2002 Wiley‐Liss, Inc.     

阿霉素性心肌病之心肌线粒体酶的细胞化学研究

阿霉素性心肌病之心肌线粒体SDH和CCO的细胞化学观察发现,多数线粒体的酶活性较弱,少数较强或中等,并与ADR的累积用量和心肌损伤程度有关。作者认为SDH和CCO活性降低,线粒体能量代谢障碍在ADR引起心肌病的过程中起着重要作用。     

No evidence for humoral autoimmunity against cardiomyocytes,adrenergic or muscarinic receptors in patients with Tako-Tsubo cardiomyopathy

Background

An association between Tako-Tsubo cardiomyopathy (TTC) and underlying malignancies has been observed, suggesting that TTC might be the consequence of paraneoplastic phenomena. This study investigates the presence of autoantibodies against cardiomyocytes as well as adrenergic (β₁, β₂) and muscarinic (M2) receptors in patients with TTC.

Severe dilated cardiomyopathy as a consequence of Ecstasy intake

Dilated cardiomyopathy (DCM) is one of the most common causes of heart failure with a prevalence of 1:2500. There are several primary and secondary etiologic factors, including gene mutations, infection agents, particularly viruses, toxins, autoimmune, and systemic disorders, and pheochromocytoma, neuromuscular, metabolic, mitochondrial, and nutritional disorders. However, a precise diagnosis can be reached only in no more than 50% of all cases. Herein, we report a rare case of hepatic damage and severe DCM as a consequence of relatively popular socially used narcotic-Ecstasy (3,4-methylenedioxy-N-methylamphetamine [MDMA]).     

Loss of lamin A/C expression revealed by immuno-electron microscopy in dilated cardiomyopathy with atrioventricular block caused by<Emphasis Type="Italic"> LMNA</Emphasis> gene defects

Mutations of the LMNA gene encoding the lamin A and C nuclear envelope proteins cause an autosomal dominant form of dilated cardiomyopathy (DCM) with atrioventricular block (AVB). The aim of this study was to investigate ultrastructural nuclear membrane changes by conventional electron microscopy and protein expression by immuno-electron microscopy in the heart of patients with DCM and AVB due to LMNA gene mutations. Four immunohistochemical techniques were used: pre-embedding and post-embedding in Epon-Araldite resin and London Resin White (LRW), with and without silver enhancement. Parallel light microscopy immunohistochemistry studies were performed. Conventional electron microscopy showed a loss of integrity of the myocyte nuclei with blebs of the nuclear membrane, herniations and delamination of the nuclear lamina and nuclear pore clustering. Post-embedding LRW was the most informative technique for morphology and immuno-labelling. Immuno-labelling was almost absent in the nuclear envelope of patients with LMNA gene mutations, but intensely present in controls. The loss of labelling selectively affected myocyte nuclei; the endothelial cell nuclei were immunostained in patients and controls. Light immunohistochemistry confirmed the results. These findings confirm the hypothesis that LMNA gene defects are associated with a loss of protein expression in the selective compartment of non-cycling myocyte nuclei.     

Genomic structure and eight novel exonic polymorphisms of the human N-cadherin gene

 Analysis of the detailed genomic structure of human N-cadherin revealed that the 16-exon gene is more than 72 kb in length and that it consists of a mosaic of exons. Five repeated cadherin domains, a transmembrane domain, and a cytoplasmic domain are encoded by exons 4 to 13, 13 and 14, and 14 to 16, respectively. A search for molecular variants in the entire coding region in 96 Japanese individuals resulted in the identification of eight sequence polymorphisms including three CCT- or GCC-type trinucleotide repeat polymorphisms adjacent to the initiation codon and five other novel single-nucleoticle polymorphisms (SNPs) in the coding region. Three of the five SNPs accompanied an amino acid substitution: Ala118Thr, Ala826Thr, and Asn845Ser. Knowlege of the fine gene structure and eight novel polymorphisms will be useful for the genetic study of the role of N-cadherin in diseases involving cell adhesion in the brain and in cardiomyocytes. Received: January 23, 2002 / Accepted: March 12, 2002     

Structural and functional analysis of a new desmin variant causing desmin‐related myopathy

Desmin‐related myopathy is a familial or sporadic disease characterized by skeletal muscle weakness and cardiomyopathy as well as the presence of intracytoplasmic aggregates of desmin‐reactive material in the muscle cells. Previously, two kinds of deletions and eight missense mutations have been identified in the desmin gene and proven to be responsible for the disorder. The present study was conducted to determine structural and functional defects in a pathogenic desmin variant that caused a disabling disorder in an isolated case presenting with distal and proximal limb muscle weakness and cardiomyopathy. We identified a novel heterozygous Q389P desmin mutation located at the C‐terminal part of the rod domain as the causative mutation in this case. Transfection of desmin cDNA containing the patient’s mutation into C2.7, MCF7, and SW13 cells demonstrated that the Q389P mutant is incapable of constructing a functional intermediate filament network and has a dominant negative effect on filament formation. We conclude that Q389P mutation is the molecular event leading to the development of desmin‐related myopathy. Hum Mutat 18:388–396, 2001. © 2001 Wiley‐Liss, Inc.