Lamin A/C mutations in dilated cardiomyopathy.

Dilated cardiomyopathy (DCM) is one of the leading causes of heart failure and heart transplant. Mutations in 60 genes have been associated with DCM. Approximately 6% of all DCM cases are caused by mutations in the lamin A/C gene (LMNA). LMNA codes for type-V intermediate filaments that support the structure of the nuclear membrane and are involved in chromatin structure and gene expression. Most LMNA mutations result in striated muscle diseases while the rest affects the adipose tissue, peripheral nervous system, multiple tissues or lead to progeroid syndromes/overlapping syndromes. Patients with LMNA mutations exhibit a variety of cellular and physiological phenotypes. This paper explores the current phenotypes observed in LMNA-caused DCM, the results and implications of the cellular and animal models of DCM and the prevailing theories on the pathogenesis of laminopathies.

LMNA mutations in Polish patients with dilated cardiomyopathy: prevalence, clinical characteristics, and in vitro studies.

BACKGROUND: LMNA mutations are most frequently involved in the pathogenesis of dilated cardiomyopathy with conduction disease. The goal of this study was to identify LMNA mutations, estimate their frequency among Polish dilated cardiomyopathy patients and characterize their effect both in vivo and in vitro. METHODS: Between January, 2008 and June, 2012 two patient populations were screened for the presence of LMNA mutations by direct sequencing: 66 dilated cardiomyopathy patients including 27 heart transplant recipients and 39 dilated cardiomyopathy patients with heart failure referred for heart transplantation evaluation, and 44 consecutive dilated cardiomyopathy patients, referred for a family evaluation and mutation screening. RESULTS: We detected nine non-synonymous mutations including three novel mutations: p.Ser431*, p.Val256Gly and p.Gly400Argfs*11 deletion. There were 25 carriers altogether in nine families. The carriers were mostly characterized by dilated cardiomyopathy and heart failure with conduction system disease and/or complex ventricular arrhythmia, although five were asymptomatic. Among the LMNA mutation carriers, six underwent heart transplantation, fourteen ICD implantation and eight had pacemaker. In addition, we obtained ultrastructural images of cardiomyocytes from the patient carrying p.Thr510Tyrfs*42. Furthermore, because the novel p.Val256Gly mutation was found in a sporadic case, we verified its pathogenicity by expressing the mutation in a cellular model. CONCLUSIONS: In conclusion, in the two referral centre populations, the screening revealed five mutations among 66 heart transplant recipients or patients referred for heart transplantation (7.6%) and four mutations among 44 consecutive dilated cardiomyopathy patients referred for familial evaluation (9.1%). Dilated cardiomyopathy patients with LMNA mutations have poor prognosis, however considerable clinical variability is present among family members.

Variants of the lamin A/C (LMNA) gene in non-valvular atrial fibrillation patients: a possible pathogenic role of the Thr528Met mutation.

BACKGROUND AND OBJECTIVE: Lamin A/C (LMNA) gene mutations cause dilated cardiomyopathy, often accompanied by conduction disturbances. Our aim was to search for LMNA mutations in individuals with atrial fibrillation. METHODS: A cohort of Polish subjects (N = 103) with non-valvular atrial fibrillation with a high (48.5%) prevalence of conduction system disturbances was screened for LMNA variants by direct DNA sequencing. RESULTS: We found a single non-synonymous variant (Thr528Met) in a 72-year-old patient with normal left ventricular function and episodes of advanced atrioventricular block. One of his two mutation-carrying daughters had episodes of type I second-degree atrioventricular block on a 24-hour Holter ECG and peak exercise arrhythmia. Interpretation of cardiac anomalies observed in the other daughter was complicated by thyroid insufficiency. A Thr528Met weak pathogenic effect was supported by transient transfections of C2C12 mouse myoblasts and computationally. Another interesting variant was Ile26Ile (c.78C>T), found in a New York Heart Association class III patient with a depressed left ventricular ejection fraction (30%), left bundle branch block, and a family history of heart disease. Ile26Ile was absent in 246 healthy individuals and was computationally predicted to interfere with splicing. CONCLUSION: LMNA mutations are not a frequent cause of atrial fibrillation even when conduction disease is present. Unlike the majority of LMNA mutations clearly associated with a severe clinical phenotype and a poor prognosis, Thr528Met results in a more subtle pathogenic effect, while Ile26Ile should be considered as a variant of unknown significance.

A new c.1621 C > G, p.R541G lamin A/C mutation in a family with DCM and regional wall motion abnormalities (akinesis/dyskinesis): genotype-phenotype correlation.

Mutations in the lamin A/C gene (LMNA) are established causes of familial dilated cardiomyopathy (DCM) with atrio-ventricular block although relatively little is known about genotype-phenotype correlations. We describe a 23-year-old patient who presented with inferolateral wall thinning and akinesis with evidence of mid-myocardial fibrosis on cardiac magnetic resonance. Molecular analysis driven by clinical similarities with a previously described case harboring the p.R541C LMNA mutation revealed a novel c.1621 C > G, p.R541G substitution whose pathogenicity was confirmed by transfection of mouse myoblasts. Our results emphasize the role of LMNA mutations at position R541 in DCM cases with segmental LV wall motion akinesis/dyskinesis.

Dilated cardiomyopathy with profound segmental wall motion abnormalities and ventricular arrhythmia caused by the R541C mutation in the LMNA gene.

In laminopathies cardiac involvement is common with dilated cardiomyopathy associated with atrio-ventricular block and malignant ventricular arrhythmia found in vast majority of patients. However, the specific disease course can be very different even among members of the same family which makes genotype-phenotype correlations difficult. Here we describe a 19-year-old patient with the LMNA R541C mutation and compare the course of his disease with two previously reported cases of the same molecular defect. We found that our patient shared important features with the previously described other subjects: significant LV segmental contractility defects (dyskinesis of the inferior wall and akinesis of LV apex), the presence of LBBB without atrio-ventricular block on 12-lead standard ECG and ICD requirement. The important differences between our subject and previously reported cases were early presentation (first symptoms at the age of 11 years) and early, progressive LV dilatation. We conclude that the LMNA R541C mutation should be considered not only in patients with malignant ventricular arrhythmia and LV local wall motion abnormalities, but also in classic dilated cardiomyopathy with profound segmental LV contractility defects.