Cardiogenetics 2013; volume 3:e1 Lamin A/C mutation affecting right side of the heart. The phenotype resem- bles ARVC but does not fulfill the Task Force Correspondence: Laura Ollila and Tiina Heliö, primarily the right side Criteria. The main clinical manifestations of HYKS/Meilahden sairaala, Sydäntutkimusosasto, of the heart the mutation were severe tricuspid insuffi- PL 340, 00029 HUS, Finland. ciency, right ventricular enlargement and fail- Fax: +358.9.471.74574. Laura Ollila,1 Johanna Kuusisto,2 ure. Three of the affected patients died of the E-mail: [email protected]; [email protected] 2 2 Keijo Peuhkurinen, Satu Kärkkäinen, heart disease, and the two living patients Key words: LMNA, Lamin A/C, dilated cardiomy- Petri Tuomainen,2 Maija Kaartinen,1 received heart transplants at ages 44 and 47. opathy, arrhythmogenic right ventricular car- Olayinka Raheem,3 Bjarne Udd,3,4,5 Electron microscopy showed nuclear blebbing diomyopathy. Jarkko Magga,6 Janne Rapola,1 compatible with laminopathy. Immunohisto - Annukka M. Lahtinen,7 Eero Lehtonen,8,9 chemical analysis did not suggest desmosomal Acknowledgements: we would like to thank Sini Weckström for technical assistance. Miia Holmström,10 Sari Kivistö,10 pathology. No desmosomal mutations were found. The Phe237Ser LMNA mutation causes Elisabeth Widén,11 Markku Saksa,12 Contributions: LO, TH, responsible for all aspects a phenotype different from traditional cardio- Tiina Heliö1 of reliability and freedom from bias of presented laminopathy. Our findings suggest that car- data and their discussed interpretation; JK, 1Helsinki University Hospital, Department diomyopathy affecting primarily the right side genetic analysis, clinical data acquisition and 2 of Cardiology, Helsinki; University of of the heart is not always caused by desmoso- analysis, manuscript revision; KP, PT, MK, JM, JR, Tampere, Tampere; 3Neuromuscular mal pathology. Our observations highlight the MH, SKi, EW, MS, clinical data acquisition and Research Unit, Tampere University and challenges in classifying cardiomyopathies, as analysis, manuscript revision; SKä, AL, genetic University Hospital, Tampere; there often is significant overlap between the analysis, manuscript revision; OR, BU, EL, immunohistochemical analysis of endomyocar- 4Folkhälsan Institute of Genetics and traditional categories. dial samples, manuscript revision. Department of Medical Genetics, Haartman Institute, University of Funding: Finnish Foundation for Cardiovascular Helsinki, Helsinki; 5Neurology Research, Finnish Medical Foundation, Special Department, Vaasa Central Hospital, Introduction governmental subsidy for health sciences onlyresearch, EVO-funds, Finnish Cultural Vaasa; 6Oulu University Hospital, Oulu; Foundation. 7Research Programs Unit, Molecular Idiopathic dilated cardiomyopathy (DCM) is characterized by left ventricular dilatation and Medicine and Department of Medicine, Conflict of interests: the authors declare no impaired systolic function in the absence of University of Helsinki, Helsinki; potential conflict of interests. hypertension, coronary artery disease,use valvular 8Department of Pathology, University of disease or other apparent cause. It is estimat- Received for publication: 5 November 2012. Helsinki; 9Laboratory Animal Centre, ed to be hereditary in 25-50% of patients.1-3 Revision received: 15 January 2013. University of Helsinki, Helsinki; Familial DCM has a diverse genetic back- Accepted for publication: 19 January 2013. 10 Department of Radiology, University ground. So far, mutations in more than 40 of Helsinki and HUS Radiology (Medical autosomal genes have been found to cause This work is licensed under a Creative Commons 11 Attribution NonCommercial 3.0 License (CC BY- Imaging Center), Helsinki; Institute for familial DCM in a typically autosomal domi- NC 3.0). Molecular Medicine Finland (FIMM), nant inheritance pattern.3,4 Genes shown to University of Helsinki, Helsinki; cause DCM can be grouped by function or cel- ©Copyright L. Ollila et al., 2013 12Kanta-Häme Central Hospital, lular location into nuclear envelope proteins, Licensee PAGEPress, Italy Hämeenlinna, Finland such as Lamin A/C (LMNA), emerin and Cardiogenetics 2013; 3:e1 nesprin, cytoskeletal proteins such as dys- doi:10.4081/cardiogenetics.2013.e1 commercialtrophin, and sarcomere genes such as - myosin heavy chain and troponin T.3 Using the Abstract traditional Sanger sequencing a genetic cause ent. Carriers of Lamin A/C mutations have also for familial DCM patients can be found in been shown to be at a high risk of ventricular LMNA mutations are amongstNon the most about a third of the cases.5 The proportion of arrhythmias and sudden death.9,10 important causes of familial dilated cardiomy- patients receiving a genetic diagnosis for their Arrhythmogenic right ventricular cardiomy- opathy. The most important cause of arrhyth- disease will likely increase with the use of next opathy (ARVC) affects primarily the right ven- mogenic right ventricular cardiomyopathy generation sequencing techniques as suggest- tricle, although lately biventricular and left (ARVC) is desmosomal pathology. The aim of ed recently by Herman et al. reporting that ventricular forms have been identified.11,12 the study was to elucidate the role of LMNA truncating titin mutations explain approxi- ARVC is characterized by life-threatening mutations among Finnish cardiomyopathy mately 25% of familial DCM.6 arrhythmias and the replacement of the patients. We screened 135 unrelated cardiomy- Lamin A/C has been shown to cause 9% of myocardium with fibro-fatty tissue. It has been opathy patients for LMNA mutations. Because DCM leading to heart transplantation in considered to be caused mainly by mutations of unusual phenotype, two patients were Finland.7 Six Lamin A/C mutations leading to in genes encoding several desmosomal pro- screened for the known Finnish ARVC-related heart disease have been previously reported in teins.13 In addition, non-desmosomal genes mutations of desmosomal genes, and their Finland.7,8 Clinical characteristics most often such as ryanodine receptor 2 (RYR2), trans- Plakophilin-2b gene was sequenced. associated with the Lamin A/C mutations that forming growth factor beta 3 (TGFB3), trans- Myocardial samples from two patients were cause DCM are arrhythmias, in particular atri- membrane protein 43 (TMEM43), and recently examined by immunohistochemical plakoglo- al fibrillation, atrioventricular conduction LMNA, have been associated with ARVC.14-17 bin staining and in one case by electron defects, and bradycardia resulting in a need of Surprisingly, in a population-based cohort of microscopy. We found a new LMNA mutation a pacemaker, left ventricular dilatation and over 6000 Finns, the prevalence of ARVC-relat- Phe237Ser in a family of five affected members eventually heart failure. The onset of clinical ed desmosomal mutations was 1:200 suggest- with a cardiomyopathy affecting primarily the manifestations of the disease is age-depend- ing incomplete penetrance.18 There is signifi- [Cardiogenetics 2013; 3:e1] [page 1] Article cant overlap between the traditional clinical using polymerase chain reaction (PCR). The lead citrate and examined in a Jeol 1400 elec- subtypes of cardiomyopathy. It is not uncom- coding regions of the LMNA gene were directly tron microscope equipped with Olympus-SIS mon for a cardiomyopathy patient to have char- sequenced with ABIPRISM 310 or 3100 Genetic Morada digital camera. acteristics of more than one clinical subtype, analyzer (PE Applied Biosystems, Foster City, Parametric linkage analysis was carried out or change phenotype as the disease progress- CA, USA). The pathogenicity of Lamin A/C in Pedigree 1 by utilizing the software es. The vastly growing genetic knowledge of mutations was assessed in silico using Poly Merlin.23 An affected-only model was used, set- cardiomyopathies also challenges the rigid Phen-2 software.21 ting the disease and marker allele frequencies division of cardiomyopathies in to the classic The genetic analyses of desmosomal pro- to 1/10,000, and considering family-members categories.1,11 teins were performed at the University of with atrioventricular blocks, arrhythmias or In our search for new LMNA mutations in Helsinki. All protein-coding exons and exon- DCM as affected. All participants of the study Finnish cardiomyopathy patients we found intron junctions of plakophilin-2b (PKP2b) signed written informed consent. The study three new mutations and one that has been were amplified using PCR and sequenced with protocol was approved by the Ethics previously reported elsewhere.19 One of the BigDye Terminator v3.1 and ABI 3730xl DNA Committees of the Universities of Helsinki and new mutations is associated with a clinical Analyzer (Applied Biosystems, Carlsbad, CA, Eastern Finland, and is in compliance with the phenotype affecting primarily the right side of USA). All five known Finnish ARVC-associated Helsinki declaration. the heart. Another new mutation is located in mutations plakophilin-2 (PKP2) Q59L, PKP2 the same codon as a previously described Q62K, PKP2 N613K, desmoplakin (DSP) mutation.20 T1373A, and desmoglein-2 (DSG2) 3059_3062delAGAG were assayed using direct Results sequencing or restriction enzyme assays as described previously.18,22 We found one previously reported Lamin A/C Materials and Methods Myocardial samples of the patients III:4 and mutation (Arg166Pro)19 and three new muta- III:6 carrying the LMNA Phe237Ser mutation tions (Phe 237Ser, c.1442 dup A, and We screened