Clinical and Functional Characterization of a Novel Mutation in Lamin A/C Gene in a Multigenerational Family with Arrhythmogenic Cardiac Laminopathy

Abstract

Mutations in the lamin A/C gene (LMNA) were associated with dilated cardiomyopathy (DCM) and, recently, were related to severe forms of arrhythmogenic right ventricular cardiomyopathy (ARVC). Both genetic and phenotypic overlap between DCM and ARVC was observed; molecular pathomechanisms leading to the cardiac phenotypes caused by LMNA mutations are not yet fully elucidated. This study involved a large Italian family, spanning 4 generations, with arrhythmogenic cardiomyopathy of different phenotypes, including ARVC, DCM, system conduction defects, ventricular arrhythmias, and sudden cardiac death. Mutation screening of LMNA and ARVC-related genes PKP2, DSP, DSG2, DSC2, JUP, and CTNNA3 was performed. We identified a novel heterozygous mutation (c.418_438dup) in LMNA gene exon 2, occurring in a highly conserved protein domain across several species. This newly identified variant was not found in 250 ethnically-matched control subjects. Genotype-phenotype correlation studies suggested a co-segregation of the LMNA mutation with the disease phenotype and an incomplete and age-related penetrance. Based on clinical, pedigree, and molecular genetic data, this mutation was considered likely disease-causing. To clarify its potential pathophysiologic impact, functional characterization of this LMNA mutant was performed in cultured cardiomyocytes expressing EGFP-tagged wild-type and mutated LMNA constructs, and indicated an increased nuclear envelope fragility, leading to stress-induced apoptosis as the main pathogenetic mechanism. This study further expands the role of the LMNA gene in the pathogenesis of cardiac laminopathies, suggesting that LMNA should be included in mutation screening of patients with suspected arrhythmogenic cardiomyopathy, particularly when they have ECG evidence for conduction defects. The combination of clinical, genetic, and functional data contribute insights into the pathogenesis of this form of life-threatening arrhythmogenic cardiac laminopathy.

Lamin A/C -Related Cardiac Disease

“…Recently, another LMNA mutation (p.(Leu140_Ala146dup)) was described as associated with both arrhythmogenic right ventricular cardiomyopathy and DCM. 32 In 2 other studies, genetic screening in patients with arrhythmogenic right ventricle cardiomyopathy revealed 5 missense mutations and 1 nonsense mutation in LMNA in the absence of mutations in the desmosomal genes. 33,34 Although DCM was the predominant form of cardiomyopathy in our cohort, right ventricular involvement was seen in 57% of the patients with DCM, and the available pathology reports in 2 probands describe extensive right ventricle involvement.…”

Functional Characterization of a Novel Truncating Mutation in Lamin A/C Gene in a Family with a Severe Cardiomyopathy with Conduction Defects

“…In recent years, mutations of the lamin A/C gene have been associated with a combination of morphofunctional phenotypes between DCM and ARVC, suggesting a new (and wider) classification of cardiomyopathies [35]. Patients carrying LMNA variants displayed arrhythmogenic cardiomyopathies with high intra-familial variability, including ARVC, DCM, left ventricular (LV) systolic dysfunction without LV enlargement, system conduction defects and arrhythmias [4,5,36]. The patients evaluated in this study and harboring the D243Gfs*4 LMNA mutation are characterized by conduction defect and arrhythmia, which can be both explained by CX43 downregulation in patient's cardiomyocytes.…”

“…The frameshift nucleotide deletion LMNA p.D243Gfs*4 was performed with Stratagene's Quik Change II XL site-directed mutagenesis kit (Agilent Technologies, Santa Clara, CA, USA), using the PCR product of LMNA cDNA cloned in the pcDNA™6.2/N-EmGFP-DEST (Thermo Fisher Scientific, Waltham, MA, USA) vector system as a template [5,8]. Mutagenic primers were designed using Quik Change Primer Design Program available online at www.agilent.com/genomics/qcpd/.…”

“…sinus node dysfunction or atrioventricular conduction block), impaired systolic function and ventricular dilation, ultimately increasing the risk of sudden cardiac death and heart failure [1,4]. However, in addition to DCM-CD, other forms of arrhythmogenic cardiomyopathies such as arrhythmogenic right ventricular cardiomyopathy (ARVC) have been linked to LMNA mutations [5].…”

The expression of Lamin A mutant R321X leads to endoplasmic reticulum stress with aberrant Ca2+ handling

“…The non‐synonymous C961T nucleotide substitution was performed with Stratagene's Quik Change II XL site‐directed mutagenesis kit (Agilent Technologies, Santa Clara, CA, USA), using the PCR product of LMNA cDNA cloned in the pcDNA ™ 6.2/N‐EmGFP‐DEST (Thermo Fisher Scientific, Waltham, MA, USA) vector system as a template . Mutagenic primers were designed using Quik Change Primer Design Program available online at http://www.agilent.com/genomics/qcpd/.…”