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Hypertrophic cardiomyopathy (HCM) is a monogenic disease with autosomal dominant inheritance. Genotype−phenotype relationships are complex, with variable penetrance even within the same family. The involvement of other modulating genetic and environmental factors is unknown. We aimed to analyze the HCM in monozygotic twins, carriers of the same founder pathogenic variant MYBPC3 p.G263*. The relationship was verified using the PowerPlex 16 HS System kit. Phenotypic differences and environmental differences (overloading conditions, coexistence and location, lifestyle, sport, and intensity) were analyzed. Three pairs of twins genetically identical for all markers and carriers of MYBPC3 G263* were identified. No environmental differences were identified. One of the 89-year-old twins had symptomatic severe obstructive HCM that required septal ablation, while her twin has remained asymptomatic with mild phenotype >80 years. A 49-year-old twin had a severe phenotype of obstructive HCM and pending myectomy, while his twin had a mild asymptomatic phenotype. In the last pair of twins, one presented a much larger left ventricular hypertrophy than his identical twin. In summary, we present three pairs of HCM twin patients sharing not only the genetic cause of the inherited disease but the entire genetic background. Despite identical genetic information and the absence of other known clinical, environmental, or lifestyle differences, the severity of the HCM phenotype is strikingly different. These unexplained differences should prompt the study of other unknown modulating factors, either epigenetic or environmental. Show less

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease. The current challenge relies on the accurate classification of the pathogenicity of the variants. Transthoracic echocardiography (TTE) is recommended at initial evaluation and cardiac magnetic resonance (CMR) imaging should also be considered. We aimed to reappraise the penetrance and clinical expression of the MYBPC3 p.G263* variant. Three hundred and eighty-four HCM probands and a control cohort of 450 individuals were studied for the main sarcomere genes by next-generation sequencing. All MYBPC3 p.G263* carriers were identified and family screening was performed. Clinical information was recorded retrospectively before 2015 and prospectively thereafter. Extra effort was invested in performing CMR in all carriers, despite TTE results. Thirteen HCM probands and none of the controls were carriers of the MYBPC3 p.G263* pathogenic variant (according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology). A total of 39 carriers were identified with family screening. Most patients with HCM were asymptomatic at the time of diagnosis and showed late-onset disease. Despite having a relatively benign course in the young, late HCM-related complications could occur. Penetrance was around 70% when evaluated by TTE and was 87.2% with TTE plus CMR. Penetrance was age-dependent, reaching 100% in carriers older than 55 years. MYBPC3 p.G263* shares with most truncating pathogenic variants in this gene a late onset, relatively benign clinical course in the young, and high penetrance. Cardiac magnetic resonance could be a useful tool to evaluate carriers despite TTE results. Show less

Recent exome sequencing studies identified filamin C ( A total of 448 HCM patients were next generation-sequenced (semiconductor chip technology) for the We provide a compelling evidence of the involvement of Show less

Hypertrophic cardiomyopathy (HCM) is a common cardiac genetic disorder associated with heart failure and sudden death. Mutations in the cardiac sarcomere genes are found in approximately half of HCM patients and are more common among cases with a family history of the disease. Data about the mutational spectrum of the sarcomeric genes in HCM patients from Northern Africa are limited. The population of Tunisia is particularly interesting due to its Berber genetic background. As founder mutations have been reported in other disorders. We performed semiconductor chip (Ion Torrent PGM) next generation sequencing of the nine main sarcomeric genes (MYH7, MYBPC3, TNNT2, TNNI3, ACTC1, TNNC1, MYL2, MYL3, TPM1) as well as the recently identified as an HCM gene, FLNC, in 45 Tunisian HCM patients. We found sarcomere gene polymorphisms in 12 patients (27%), with MYBPC3 and MYH7 representing 83% (10/12) of the mutations. One patient was homozygous for a new MYL3 mutation and two were double MYBPC3 + MYH7 mutation carriers. Screening of the FLNC gene identified three new mutations, which points to FLNC mutations as an important cause of HCM among Tunisians. The mutational background of HCM in Tunisia is heterogeneous. Unlike other Mendelian disorders, there were no highly prevalent mutations that could explain most of the cases. Our study also suggested that FLNC mutations may play a role on the risk for HCM among Tunisians. Show less

Massive DNA sequencing, also known as next-generation sequencing, has revolutionized genetic diagnosis. This technology has reduced the effort and cost needed to analyze several genes simultaneously and has made genetic evaluation available to a larger number of patients. In hypertrophic cardiomyopathy, genetic analysis has increased from the 3 main genes implicated in the disease (MYH7, MYBPC3, TNNT2) to sequencing of more than 20 related genes. Despite the advantages of acquiring this additional information, many patients show variants of uncertain significance (mainly amino acid changes), which may also be present in at least 1 healthy control undergoing genome sequencing. This will be a dead-end situation unless the variant can be demonstrated to be associated with the disease in the patient's family. In the absence of clear evidence that these variants are truly pathogenic, they cannot be used for reliable genetic counselling in family members. Massive sequencing also enables identification of new candidate genes, but again, the problem of variants of uncertain significance limits the success of these assessments. Show less

Mutations in at least 30 genes have been linked to hypertrophic cardiomyopathy (HCM). Due to the large size of the main HCM genes, Sanger sequencing is labor intensive and expensive. The purpose was to develop a next-generation sequencing (NGS) procedure for the main HCM genes. METHODS AND RESULTS: Multiplex amplification of the coding exons of MYH7,MYBPC3,TNNT2,TNNI3,ACTC1,TNNC1,MYL2,MYL3, and TPM1 was designated, followed by NGS with the Ion Torrent PGM (Life Technologies). A total of 8 pools containing DNA from HCM patients were sequenced in a 2-step approach. First, a total of 60 patients (validation cohort) underwent both PGM and Sanger sequencing for the 9 genes. No false-negative variants were found on NGS (100% sensitivity), and a specificity of 97% and 80% was achieved for single-nucleotide and insertion/deletion variants, respectively. Second, the PGM was used to search for mutations in a total of 76 cases not previously studied (discovery cohort). A total of 19 putative mutations were identified in the discovery pools, which were confirmed and assigned to specific patients on Sanger sequencing. An NGS procedure has been developed for the main sarcomeric genes that would facilitate the screening of large cohorts of patients. In addition, this procedure would facilitate the uncovering of rare gene variants on a population scale. Show less

Mutation of a sarcomeric gene is the most frequent cause of hypertrophic cardiomyopathy. For each such gene, however, previous studies have reported a range of different mutation frequencies, and clinical manifestations have been highly heterogeneous, both of which limit the use of genetic information in clinical practice. Our aim was to determine the frequency of mutations in the sarcomeric genes MYH7, MYBPC3, TNNT2, TNNI3, and TPM1 in a cohort of Spanish patients with hypertrophic cardiomyopathy. We used sequencing to analyze the coding regions of these five genes in 120 patients (29% with a family history) and investigated how the patient phenotype varied with the gene mutated. In total, 32 patients were found to have mutations: 10 in MYH7 (8%), 20 in MYBPC3 (16%), 2 in TNNT2, 1 in TPM1 and none in TNNI3. Overall, 61% of mutations had not been described before. Two patients had two mutations (i.e., double mutants). There was no difference in the mean age at diagnosis or the extent of the hypertrophy between those with MYH7 mutations and those with MYBPC3 mutations. Some 26% of patients had a mutation in one of the five sarcomeric genes investigated. More than half of the mutations had not been described before. The MYBPC3 gene was the most frequently mutated, followed by MYH7. No phenotypic differences were observed between carriers of the various mutations, which makes it difficult to use genetic information to stratify risk in these patients. Show less

Sudden death during sports activities, although unfrequent, is a tragic event with great impact on both the general and medical communities. The two commonest conditions leading to sudden cardiac death in young athletes are hyperthrophic cardiomyopathy (HCM), the main cause in the USA, and arrythmogenic right ventricular cardiomyopathy, which is the leading cause in Europe. We report the case of a 17-year-old football player with a pathological electrocardiography (ECG) in the pre-participation screening programme, highly suggestive of HCM, in which ECG study showed a septum thickness of 28 mm. Genetic analysis revealed R 495 W mutation in the 18 exon of the MyBPC3 (myosin-binding protein C) and sports activities were contraindicated. Two years later, septum thickness was 19.5 mm. Usefulness of 12-lead ECG, differential diagnosis between athlete's heart and HCM, and the stratification in patients with HCM are discussed. Show less

Mutations in the cardiac myosin-binding protein C gene (MYBPC3) are responsible for up to 50% of familial cases with hypertrophic cardiomyopathy (HC). Compared to patients with mutations in other sarcomeric genes, patients with MYBPC3 mutations would have a milder form of the disease, with a lower incidence of sudden cardiac death. Because most of the mutations have been found in only one family, it is currently difficult to establish a correlation between a particular mutation and the HC phenotype. The aim of our study was to contribute to understanding of the role of MYBPC3 mutations in HC. We analysed the MYBPC3 exons and intron flanking regions in 10 patients from 10 families with at least two HC cases. After direct sequencing of polymerase chain reaction (PCR) fragments, we found three new mutations in three families (V771M, V342D, and A627V). These changes affected evolutionary conserved amino acids and were not found in 100 healthy controls. The Ala 627>Val was found homozygous in a 47-year-old patient with a severe form of HC, while his mother and a nephew were heterozygous carriers and asymptomatic. This fact suggests a dosage effect for mutations at the MYPBC3 gene. Show less