Mutations In Sarcomere Protein Genes Research Articles

Hypertrophic Cardiomyopathy: Genetic Foundations, Outcomes, Interconnections, and Their Modifiers.

Hypertrophic cardiomyopathy (HCM) is the most prevalent heritable cardiomyopathy. HCM is considered to be caused by mutations in cardiac sarcomeric protein genes. Recent research suggests that the genetic foundation of HCM is much more complex than originally postulated. The clinical presentations of HCM are very variable. Some mutation carriers remain asymptomatic, while others develop severe HCM, terminal heart failure, or sudden cardiac death. Heterogeneity regarding both genetic mutations and the clinical course of HCM hinders the establishment of universal genotype-phenotype correlations. However, some trends have been identified. The presence of a mutation in some genes encoding sarcomeric proteins is associated with earlier HCM onset, more severe left ventricular hypertrophy, and worse clinical outcomes. There is a diversity in the mechanisms implicated in the pathogenesis of HCM. They may be classified into groups, but they are interrelated. The lack of known supplementary elements that control the progression of HCM indicates that molecular mechanisms that exist between genotype and clinical presentations may be crucial. Secondary molecular changes in pathways implicated in HCM pathogenesis, post-translational protein modifications, and epigenetic factors affect HCM phenotypes. Cardiac loading conditions, exercise, hypertension, diet, alcohol consumption, microbial infection, obstructive sleep apnea, obesity, and environmental factors are non-molecular aspects that change the HCM phenotype. Many mechanisms are implicated in the course of HCM. They are mostly interconnected and contribute to some extent to final outcomes.

The Definition of Sarcomeric and Non-Sarcomeric Gene Mutations in Hypertrophic Cardiomyopathy Patients: A Multicenter Diagnostic Study Across Türkiye.

Hypertrophic cardiomyopathy is a common genetic heart disease and up to 40%-60% of patients have mutations in cardiac sarcomere protein genes. This genetic diagnosis study aimed to detect pathogenic or likely pathogenic sarcomeric and non-sarcomeric gene mutations and to confirm a final molecular diagnosis in patients diagnosed with hypertrophic cardiomyopathy. A total of 392 patients with hypertrophic cardiomyopathy were included in this nationwide multicenter study conducted at 23 centers across Türkiye. All samples were analyzed with a 17-gene hypertrophic cardiomyopathy panel using next-generation sequencing technology. The gene panel includes ACTC1, DES, FLNC, GLA, LAMP2, MYBPC3, MYH7, MYL2, MYL3, PLN, PRKAG2, PTPN11, TNNC1, TNNI3, TNNT2, TPM1, and TTR genes. The next-generation sequencing panel identified positive genetic variants (variants of unknown significance, likely pathogenic or pathogenic) in 12 genes for 121 of 392 samples, including sarcomeric gene mutations in 30.4% (119/392) of samples tested, galactosidase alpha variants in 0.5% (2/392) of samples and TTR variant in 0.025% (1/392). The likely pathogenic or pathogenic variants identified in 69 (57.0%) of 121 positive samples yielded a confirmed molecular diagnosis. The diagnostic yield was 17.1% (15.8% for hypertrophic cardiomyopathy variants) for hypertrophic cardiomyopathy and hypertrophic cardiomyopathy phenocopies and 0.5% for Fabry disease. Our study showed that the distribution of genetic mutations, the prevalence of Fabry disease, and TTR amyloidosis in the Turkish population diagnosed with hypertrophic cardiomyopathy were similar to the other populations, but the percentage of sarcomeric gene mutations was slightly lower.

Features of Diagnostics and Course of Hypertrophic Cardiomyopathy in Real Clinical Practice

Introduction and purpose. Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular (LV) wall thickening not associated with increased afterload (hypertension and aortic stenosis), is usually caused by mutations in sarcomeric protein genes, and is inherited in an autosomal dominant manner. Unlike HCM, myocardial hypertrophy in its phenocopies is associated with the accumulation of substances such as amyloid, glycogen, etc. in the myocardium. The aim of our work was to analyze the features of the diagnosis and course of HCM in real clinical practice. Material and methods. A retrospective analysis of medical records of 80 patients (56.3 % of men) discharged with a diagnosis of HCM from a multidisciplinary hospital in Moscow in the period from 2007 to 2021 was carried out. The diagnosis of HCM in all patients was established on the basis of echocardiography data. The median age (25th and 75th percentiles are indicated in brackets) was 57 (48.5; 63) years. The duration of hospitalization was 8 (6; 12.5) days. Results. The reason for hospitalization was angina syndrome in 35 %, suspicion of acute coronary syndrome in 16.3 %, paroxysmal atrial fibrillation (AF) in 11.3 %, decompensation of chronic heart failure in 11.3 %, syncope in 7.5 % %, hypertensive crisis in 3.8 %, coronary angiography in 3.8 %, pacemaker implantation in 2.5 %, consultation with an arrhythmologist in 2.5 %, implantation of a cardioverter-defibrillator in 1.2 %, medical examination to resolve the issue of fitness for military service in 1.2 %, acute cerebrovascular accident in 1.2 %, hypotension in 1.2 %, drug bradycardia in 1.2 % of patients. Before hospitalization, a history of myocardial infarction was diagnosed in 15 %, arterial hypertension — in 53.8 %, chronic heart failure — in 77.6 %, chronic kidney disease — in 21.3 % of patients. Prior to the analyzed hospitalization, a history of myocardial infarction was diagnosed in 15 %, arterial hypertension in 53.8 %, chronic heart failure in 77.6 %, chronic kidney disease in 21.3 % of patients. LV wall thickness ≥1.5 cm was detected in 91.2 %, symmetrical form of hypertrophy — 22.1 %, apical — 5.2 %, papillary muscle hypertrophy — 1.3 %, interventricular septum — 71.4 % of patients. Permanent obstruction of the LV outflow tract (LVOTO) was detected in 62.8 % (9.0 % of patients had a history of septal reduction), transient LVOTO — in 1.3 %, non-obstructive HCM — in 35.9 %. The ejection fraction (EF) of the LV (according to Simpson) was 63 (55-70) %, CHF with reduced LV EF <40 % was detected in 3.8 %, with a moderately reduced LV EF (40-49 %) — in 5 %, with preserved LV EF — in 68.8 % of patients. Anterior systolic movement of the anterior leaflet of the mitral valve occurred in 47.5 %, prolapse of the anterior leaflet of the mitral valve was described in 7.14 %. Mitral regurgitation was registered in 75 % of patients. 45 % of patients with HCM suffered from AF: permanent 15 %, paroxysmal 23.8 %, persistent 6.2 % of patients. During hospitalization, ventricular tachycardia was registered in 7.5 %, supraventricular tachycardia — 3.8 %, conduction disturbances were noted in 36.3 % of patients, of which atrioventricular block in 6.3 %, blockade of the right bundle branch block in 21.3 %, left bundle branch block in 15 %, and Wolff-Parkinson-White syndrome in 1.3 % . Implantation of a pacemaker in history was in 5 %, including in connection with MorgagniAdams-Stokes attacks — in 3.8 % of patients. During a median follow-up of 87 (interquartile range 45–131.5) months, 13.8 % of patients with HCM died. In deceased patients, LVOTO was significantly more common (in the dead 100 %, in the living 58.2 %, p = 0.006) and AF (in the dead 72.7 %, in the living 40.6 %, p = 0.047). Genetic testing and exclusion of HCM phenocopies was not performed during hospitalization and was not recommended for any patient. Conclusion. In real clinical practice, in most cases, only phenotypic diagnosis of HCM is carried out according to echocardiography, and screening for genetic mutations and HCM phenocopies is not performed. It is necessary to widely introduce genetic testing and screening for HCM phenocopies for the timely diagnosis of pathology that requires the appointment of specific pathogenetic therapy to improve the prognosis of patients

Sarcomeric Thin Filament Associated Cardiomyopathic Mouse Models

Cardiomyopathies are diseases primarily associated with defects in the structure and physiological function of the heart. Hypertrophic and dilated cardiomyopathies are two common conditions associated with severe pathological abnormalities that often lead to heart failure. Studies in the early 1990’s by the Seidman laboratories linked hypertrophic cardiomyopathy with mutations in both thick and thin sarcomeric protein genes. Since then, the development and analysis of animal models of both hypertrophic and dilated cardiomyopathy has significantly advanced our knowledge of the structural, molecular, biochemical, and physiological disease processes that lead to these cardiomyopathic conditions. The focus of this article is an examination of mouse models of hypertrophic and dilated cardiomyopathies with mutations in sarcomeric thin filament protein genes (actin, tropomyosin, troponin T, I, and C) and the information these models provide in our understanding of the disease processes. Special attention addresses the significant role that tropomyosin mutation models have contributed to this information. In addition, we address how various methods have been developed to phenotypically rescue these diseased hearts with respect to their morphological and physiological functions. By thorough analysis of these mouse models, not only can we better understand the disease processes, but there is a great potential for the development of effective therapeutics to treat these severe pathological conditions.

Ablation of lysophosphatidic acid receptor 1 attenuates hypertrophic cardiomyopathy in a mouse model

Myocardial fibrosis is a key pathologic feature of hypertrophic cardiomyopathy (HCM). However, the fibrotic pathways activated by HCM-causing sarcomere protein gene mutations are poorly defined. Because lysophosphatidic acid is a mediator of fibrosis in multiple organs and diseases, we tested the role of the lysophosphatidic acid pathway in HCM. Lysphosphatidic acid receptor 1 (LPAR1), a cell surface receptor, is required for lysophosphatidic acid mediation of fibrosis. We bred HCM mice carrying a pathogenic myosin heavy-chain variant (403+/-) with Lpar1-ablated mice to create mice carrying both genetic changes (403+/- LPAR1 -/-) and assessed development of cardiac hypertrophy and fibrosis. Compared with 403+/- LPAR1WT, 403+/- LPAR1 -/- mice developed significantly less hypertrophy and fibrosis. Single-nucleus RNA sequencing of left ventricular tissue demonstrated that Lpar1 was predominantly expressed by lymphatic endothelial cells (LECs) and cardiac fibroblasts. Lpar1 ablation reduced the population of LECs, confirmed by immunofluorescence staining of the LEC markers Lyve1 and Ccl21a and, by in situ hybridization, for Reln and Ccl21a. Lpar1 ablation also altered the distribution of fibroblast cell states. FB1 and FB2 fibroblasts decreased while FB0 and FB3 fibroblasts increased. Our findings indicate that Lpar1 is expressed predominantly by LECs and fibroblasts in the heart and is required for development of hypertrophy and fibrosis in an HCM mouse model. LPAR1 antagonism, including agents in clinical trials for other fibrotic diseases, may be beneficial for HCM.

Mavacamten: A First-in-class Oral Modulator of Cardiac Myosin for the Treatment of Symptomatic Hypertrophic Obstructive Cardiomyopathy.

Hypertrophic cardiomyopathy is the most common monogenic cardiovascular disease that is caused by sarcomeric protein gene mutations. A hallmark of the most common form of the disease is outflow obstruction secondary to systolic narrowing of the left ventricular outflow tract from septal hypertrophy, mitral valve abnormalities and, most importantly, hyperdynamic contractility. Recent mechanistic studies have identified excessive myosin adenosine triphosphatase activation and actin-myosin cross-bridging as major underlying causes. These studies have led to the development of mavacamten, a first-in-class myosin adenosine triphosphatase inhibitor and the first specific therapy for hypertrophic obstructive cardiomyopathy. Preclinical and subsequent pivotal clinical studies have demonstrated the efficacy and safety of mavacamten. A remarkable improvement among treated patients in peak oxygen consumption, functional capacity, symptom relief and post-exercise left ventricular outflow tract gradient, along with dramatic reductions in heart failure biomarkers, suggests that this new medication will be transformative for the symptom management of hypertrophic obstructive cardiomyopathy. There is also hope and early evidence that mavacamten may delay or obviate the need for invasive septal reduction therapies. In this article, we review the current evidence for the efficacy and safety of mavacamten and highlight important considerations for its clinical use.

Abstract 11879: The Genetic Characteristics Based on Next Generation Sequencing in Patients With Hypertrophic Cardiomyopathy

Objective: This study aimed to explore the genetic epidemiological characteristics in patients with hypertrophic cardiomyopathy (HCM). Methods: We prospectively enrolled 383 unrelated HCM probands who received genetic testing and 3.0 T cardiac MRI examination, including 118 familial HCM and 265 sporadic HCM. The diagnosis of HCM is based on the diagnostic criteria of the American Heart Association and American College of Cardiology guidelines. Patients with familial HCM underwent targeted next generation sequencing including 117 candidate pathogenic genes associated with cardiomyopathies, while sporadic HCM underwent whole-exome sequencing. The genotypic characteristics were analyzed. Results: Among the 383 unrelated Chinese HCM probands, we reported 56 new pathogenic or likely pathogenic gene site mutations, including 3 new rare non-sarcomeric gene mutations and 53 new sarcomeric gene mutations. According to the analysis of genotypic characteristics, it was found that the frequency of rare genes was 3.4%, and the positive rate of sarcomere protein gene detection was 62.4%. Among them, MYH7 and MYBPC3 are the most common pathogenic genes, accounting for 61.9% of sarcomere protein gene mutations. Additionally, in the included HCM population, there was no significant difference in the positive detection rate of sarcomere protein gene between familial HCM and sporadic HCM (66.1% vs 64%, P = 0.7). The proportion of sporadic HCM carrying polygenic mutations was higher than that of familial HCM (11.2% vs. 1.8%, P = 0.003). Conclusion: We reported 56 new gene mutations, which expanded the gene spectrum of HCM. Additionally, the frequency of rare disease genes in the HCM cohort is 3.4%, and the composition ratio of sarcomere protein gene is similar to that of North American or European HCM populations. However, the gene positive rate of sporadic HCM is similar to that of familial HCM, but the composition ratio of genotypes is different.

Arrhythmic phenotypes in patients with left ventricular non-compaction cardiomyopathy

Abstract Background Identification of pts with left ventricular non-compaction cardiomyopathy (NCCM) at high risk of life-threatening arrhythmic events is focused on clinical and instrumental criteria. The genetic component is not taken into account when deciding on a strategy for preventive measures. Purpose To analyze life-threatening arrhythmic events in pts with the arrhythmic variant of NCCM and to identify genetic factors that may increase the risk of life-threatening arrhythmic events. Methods The study included 159 pts, among whom 58 had malignant ventricular arrhythmias (mean age 43.54±11.95 years, 34/24/58.6% male). The NCCM criteria were confirmed using Echocardiography and CMR. Mutation search was carried out by the next generation sequencing (NGS) in 21 pts with nonsustained ventricular tachycardia (NVT). Results During the follow-up period (median follow-up of 36 months), life-threatening arrhythmic events (documented sustained VT, SCD with successful resuscitation and CD implantation, SCD) were registered in 29 pts (50%), and 10 pts had CD implanted. As a result of sequencing, 23.8% (5 out of 21) of pts with NVT revealed rare genetic variants with uncertain clinical significance (VUS) in 3 genes encoding ion channel proteins: KCNQ1, KCNH2 (9.5%), RYR2 (9.5%). In 9 (42.9%) pts, 10 identified mutations were localized in the genes responsible for the synthesis of sarcomeric proteins: MYBPC3 (23.8%), MYH7 (23.8%). 12 genetic variants were found in overlapping phenotypes between NCCM, ARVC and DCM: PKP2, DSP, PLN, TRPM4 (14.3%), RBM20, LDB3 (9.5%), DPP6, DTNA, NEXN in 11 (52.4%) pts. In this group of pts, the most common (81.8% of cases) were life-threatening arrhythmic events that required surgical intervention: 6 pts were implanted with CD for primary prevention of SCD, two pts - CRT-D, two pts with systolic dysfunction were performed with OHT and one patient was implanted with the Accucinch transcatheter direct mitral valve annuloplasty system. In pts with mutations in sarcomeric protein genes, CD was implanted in 4.7% of cases, and in 14.3% of pts with mutations in ion channel genes (p<0.01). Conclusion The presence of mutations in genes that control the functioning of ion channels in complex overlapping genotypes is an additional risk factor for ventricular arrhythmias in patients with NCCM. Determining the genetic component opens up new opportunities for personalizing the risk stratification of pts with NCCM. Funding Acknowledgement Type of funding source: None

Penetrance of hypertrophic cardiomyopathy and outcome in sarcomeric mutation carriers

Abstract Background Predictive genetic screening of the first degree relatives of patients with hypertrophic cardiomyopathy (HCM) caused by sarcomere protein (SP) gene mutations is current standard of care, but there are few data on long-term outcomes in mutation carriers without HCM. Purpose To establish the role of sex and genotype in HCM penetrance as well as the rate of major adverse clinical events in SP mutation carriers and following the diagnosis of HCM. Methods Retrospective analysis of consecutive adult and paediatric SP mutation carriers identified during family screening and who did not fulfill diagnostic criteria for HCM at first evaluation. Results 321 individuals from 170 families [median age first evaluation 15.2 years (IQR 7.3–32.6); 153 (47.7%) males] were evaluated. Causal SP genes were: MYBPC3 (n=133 (41.4%)), MYH7 (n=77 (24.0%)), TNNI3 (n=51 (15.9%)), TNNT2 (n=40 (12.5%)), TPM1 (n=9 (2.8%)), MYL2 (n=6 (1.9%)), and ACTC1 (n=1 (0.3%)); 4 (1.3%) carried multiple mutations. After a median follow up of 7.4 years (IQR 2.5–12.7), 89 (27.7%) patients developed HCM. Disease penetrance at the age of 50 years was 47% (95% CI 38%-56%). One hundred and fifty three (47.7%) individuals underwent cardiac magnetic resonance (CMR) imaging; among those diagnosed with HCM, 22/89 (24.7%) fulfilled criteria on CMR but not echocardiography. In a multivariable model adjusted for genotype, follow up duration and evaluation with CMR, independent predictors of HCM development were male sex (HR 3.11; CI 1.82–5.32) and abnormal ECG (HR 7.87; CI 4.43–13.97). Patients with MYH7 and multiple mutations were more likely to develop HCM than those with MYBPC3 mutations (HR 2.03; CI 1.04–3.96 and HR 10.13; CI 1.40–72.92, respectively). Disease penetrance was lowest in carriers of TNNI3 mutations (HR 0.13; CI 0.03–0.48). There were no major adverse events in individuals without HCM. Following the diagnosis of HCM, the combined rate of all-cause death, appropriate defibrillator shock or resuscitated cardiac arrest was 1.1%/year [median follow up 4.0 years (IQR 2.1–8.9)]. Conclusions Approximately 50% of SP mutation carriers develop HCM by the age of 50 and become prone to disease complications during long-term follow-up. Sex, MYH7 mutations and the presence of an abnormal ECG are associated with a higher risk of disease development. CMR should be employed systematically in long-term screening. HCM penetrance by sex Funding Acknowledgement Type of funding source: None

Penetrance of Hypertrophic Cardiomyopathy in Sarcomere Protein Mutation Carriers

BackgroundPredictive genetic screening of relatives of patients with hypertrophic cardiomyopathy (HCM) caused by sarcomere protein (SP) gene mutations is current standard of care, but there are few data on long-term outcomes in mutation carriers without HCM. ObjectivesThe aim of this study was to determine the incidence of new HCM diagnosis in SP mutation carriers. MethodsThis was a retrospective analysis of adult and pediatric SP mutation carriers identified during family screening who did not fulfill diagnostic criteria for HCM at first evaluation. ResultsThe authors evaluated 285 individuals from 156 families (median age 14.2 years [interquartile range: 6.8 to 31.6 years], 141 [49.5%] male individuals); 145 (50.9%) underwent cardiac magnetic resonance (CMR). Frequency of causal genes was as follows: MYBPC3 n = 123 (43.2%), MYH7 n = 69 (24.2%), TNNI3 n = 39 (13.7%), TNNT2 n = 34 (11.9%), TPM1 n = 9 (3.2%), MYL2 n = 6 (2.1%), ACTC1 n = 1 (0.4%), multiple mutations n = 4 (1.4%). Median follow-up was 8.0 years (interquartile range: 4.0 to 13.3 years) and 86 (30.2%) patients developed HCM; 16 of 50 (32.0%) fulfilled diagnostic criteria on CMR but not echocardiography. Estimated HCM penetrance at 15 years of follow-up was 46% (95% confidence interval [CI]: 38% to 54%). In a multivariable model adjusted for age and stratified for CMR, independent predictors of HCM development were male sex (hazard ratio [HR]: 2.91; 95% CI: 1.82 to 4.65) and abnormal electrocardiogram (ECG) (HR: 4.02; 95% CI: 2.51 to 6.44); TNNI3 variants had the lowest risk (HR: 0.19; 95% CI: 0.07 to 0.55, compared to MYBPC3). ConclusionsFollowing a first negative screening, approximately 50% of SP mutation carriers develop HCM over 15 years of follow-up. Male sex and an abnormal ECG are associated with a higher risk of developing HCM. Regular CMR should be considered in long-term screening.

Apical Hypertrophic Cardiomyopathy: The Variant Less Known.

Hypertrophic cardiomyopathy (HCM) is an umbrella term for a heterogeneous heart muscle disease that was historically (and still is) defined by the detection of left ventricular (LV) hypertrophy (LVH) in the absence of abnormal cardiac loading conditions. Long after this morphological definition was established, the genetic basis of HCM was discovered, and we now know it is predominantly caused by autosomal dominant mutations in sarcomeric protein genes.1 Several patterns of LVH have been described in HCM: asymmetric septal (here referred to as “classic” HCM), concentric, reverse septal, neutral, and apical (ApHCM),2 as well as other, rarer LVH variants such as isolated lateral LVH and isolated inferoseptal LVH. Distinguishing between morphological HCM subtypes has conferred little in terms of personalized management strategies, with one distinctive exception: ApHCM. Compared with classic HCM, ApHCM is more sporadic, sarcomere mutations are detected less frequently, there is more atrial fibrillation (AF) and sudden cardiac death (SCD) risk factors differ. No authoritative ApHCM‐specific recommendations to guide diagnosis, family screening, and patient risk stratification currently exist. First described in Japan in 1976,2 ApHCM is exemplified by “giant” negative precordial T‐waves on electrocardiography and by “spadelike” configuration of its LV cavity in end diastole.3 This review summarizes the epidemiology, clinical expression, genetics, and prognosis of ApHCM, while also highlighting knowledge gaps

Left ventricular hypertrophy: The tip of the iceberg

In the current European Guidelines, hypertrophic cardiomyopathy (HCM) is defined as a wall thickness (WT) ≥ 15 mm. Its epidemiology is presented as such: 40-60% sarcomeric protein gene mutations, 25–30% unknown and 5–10% genetic and non-genetic causes. However, clinical practice does not necessarily confirm these values. We sought to describe the panel of LVWT and final aetiologic diagnoses among patients referred for assessment of LVWT ≥ 12 mm. Consecutive patients referred to our tertiary centre since January 2017 for the assessment of LVWT ≥ 12 mm were retrospectively included. Patients presenting with severe aortic stenosis ( n = 107) were excluded. 121 patients were included in the final analysis. Personal and familial history were collected for all patients and each patient underwent a complete physical examination, electrocardiogram and transthoracic echocardiography. Additional assessments were carried out based on the results of this first screening. Median LVWT was 15 mm (IQR 14 – 17). Final aetiologies were distributed as follows: 38 (31%) amyloidosis, 26 (21%) post-hypertensive, 35 (29%) sarcomeric, 4 (3%) other diagnoses and 18 (16%) undetermined. Among patients diagnosed with amyloidosis, 4 (11%) were inherited TTR, 8 (21%) wild-type TTR, 13 (34%) TTR of undetermined type, 11 (29%) light chain and 2 (6%) AA or apoA2 amyloidosis. Among patients diagnosed with sarcomeric HCMs, 4 (11%) were carriers of a mutation. 43 patients (36%) had a maximal LVWT between 12 and 15 mm. 11 (26%) of them had cardiac amyloidosis, 4 (9%) sarcomeric HCM, 17 (40%) undetermined LVH, 11 (26%) post-hypertensive HCM and 2 (5%) other aetiologies. Meaningful diagnoses of HCMs, such as cardiac amyloidosis (26%) and sarcomeric HCM (9%), could be made in the 12 to 15 mm range of LVWT. Overall, sarcomeric HCM does not seem to be the main aetiology and the true prevalence of cardiac amyloidosis seems to be underestimated.

Cпектр мутаций в генах саркомерных белков и их фенотипическое проявление у белорусских пациентов с гипертрофической кардиомиопатией

Введение. Гипертрофическая кардиомиопатия (ГКМП) относится к наследственной патологии, основной причиной которой являются мутации в генах, кодирующих белковые компоненты миофибрильного аппарата кардиомиоцитов, при этом спектр этих генетических изменений имеет популяционные особенности. Целью данного исследования являлось определение спектра мутаций в генах, кодирующих саркомерные белки, у пациентов с ГКМП из Беларуси, а также изучение взаимосвязей между генотипом и фенотипическими проявлениями заболевания. Материалы и методы. В исследование были включены 340 неродственных пациентов с ГКМП, проживающих в Беларуси. Обнаружение мутаций в кодирующих последовательностях генов ACTC1, MYBPC3, MYH7, MYL2, MYL3, TNNI3, TNNT2, TNNС1 и TPM1 у 89 пациентов проводили методом высокопроизводительного секвенирования (NGS). Направленный поиск выявленных методом NGS генетических дефектов осуществлялся методом автоматического секвенирования по Сэнгеру, а также с использованием ПЦР-ПДРФ анализа. Результаты. У 51,7% пациентов методом NGS обнаружены мутации в генах: MYBPC3 (20,2%), MYH7 (16,9%), TPM1 (3,4%), ACTC1 (2,3%), MYL2 (1,1%) и TNNC1 (1,1%). У 6,7% индивидуумов встречались две (5,6%) или три (1,1%) замены. Обнаружены новые мутации p.Ala49Asn, p.Val1407Phe в гене MYH7; р.Tyr501Ser, р.Trp1007fs, р.Tyr1043*, р.Pro1066Arg, p.Arg1138fs, р.Pro1181Gln, р.Cys1202Arg в гене MYBPC3. Установлены часто встречающиеся мутации: р.Gln1233*, р.Ser871Alafs, комбинация р.Glu1265Val+р.Cys1266Arg, р.Gln401* и р.Trp1214Arg в гене MYBPC3, p.Arg403Trp, p.Arg663Cys, p.Arg663His, p.Ala729Pro, p.Glu924Lys и p.Glu1356Lys в гене MYH7. По данным ЭхоКГ-исследования носители мутаций в генах белков саркомера, особенно обладатели миссенс-мутаций в гене MYBPC3, имели более выраженную гипертрофию миокарда и раннюю манифестацию заболевания по сравнению с пациентами без мутаций в этих генах. Для носителей наиболее распространенной среди белорусских пациентов мутации р.Gln1233* характерны позднее начало заболевания, умеренная гипертрофия миокарда левого желудочка, частое развитие фибрилляции предсердий. Выводы. Распределение встречаемости мутаций в генах, кодирующих саркомерные белки, у пациентов с ГКМП из Беларуси не отличалось от других европейских популяций. 84,9% обнаруженных мутаций локализовано в генах MYBPC3 и MYH7. Background. Hypertrophic cardiomyopathy (HCM) is a hereditary pathology, the main cause of which is mutations in the genes encoding the protein components of the myofibril apparatus of cardiomyocytes, and the spectrum of these genetic changes has population features. The aim of the study was to determine the spectrum of mutations in the genes encoding sarcomeric proteins in patients with HCM from Belarus, as well as to study the association between the genotype and the phenotypic manifestations of the disease. Materials and methods. The study included 340 unrelated patients with HCM from Belarus. Mutation detection in the coding sequences of ACTC1, MYBPC3, MYH7, MYL2, MYL3, TNNI3, TNNT2, TNNС1 и TPM1 genes was performed by next generation sequencing (NGS) in 89 patients. The directed search for genetic defects detected by the NGS method was carried out by the automatic sequencing method using Sanger and PCR-RFLP analysis. Results. The NGS method allowed to detect mutations in the genes of 51,7% of patients: MYBPC3 (20,2%), MYH7 (16,9%), TPM1 (3,4%), ACTC1 (2,3%), MYL2 (1,1 %) and TNNC1 (1,1%). In 6,7% of individuals two (5,6%) or three (1,1%) substitutions were observed. New mutations were found: p.Ala49Asn, p.Val1407Phe in the MYH7 gene; p.Tyr501Ser, p.Trp1007fs, p.Tyr1043*, p.Pro1066Arg, p.Arg1138fs, p.Pro1181Gln, р.Cys1202Arg in the MYBPC3 gene. The most frequently occurring mutations were identified: p.Gln1233*, p.Ser871Alafs, the combination of the р.Glu1265Val + p.Cys1266Arg, R.Gln401*, and Trp1214Arg in the MYBPC3 gene, p.Glu924Lys and p.Glu1356Lys in the MYH7 gene. According to the ECG study, carriers of mutations in sarcomere protein genes, especially with missense mutations in the MYBPC3 gene, had more severe myocardial hypertrophy and early disease manifestation then patients without mutations in those genes. The p.Gln1233* mutation was the most common among Belarusian patients and characterized by late onset of the disease, mild left ventricular myocardial hypertrophy and the more frequent development of atrial fibrillation. Conclusions. In general, the distribution of mutations in the genes encoding sarcomeric proteins in patients with HCM from Belarus didn’t differ from other European populations. 84,9% of the detected mutations were localized in MYBPC3 and MYH7 genes.

Risk stratification in childhood hypertrophic cardiomyopathy.

[first paragraph of article]The true prevalence of hypertrophic cardiomyopathy (HCM) in childhood is unknown, but population-based studies have reported an annual incidence between 0.24–0.47 per 100,000 children. The aetiology of disease is more heterogeneous than that seen in adult populations, with up to 30% of patients having an inborn error of metabolism, malformation syndrome or neuromuscular syndrome. However, as in adults, most cases are caused by mutations in the cardiac sarcomere protein genes, even in young children. The long-term outcome of childhood HCM is highly variable and has been shown to depend partly on the age of presentation and underlying aetiology. Outside of infancy, the most frequent cause of mortality is sudden cardiac death (SCD), and one of the greatest challenges in managing young patients with HCM is identifying those at greatest risk of an arrhythmic event.

Added value of cardiac deformation imaging in differential diagnosis of left ventricular hypertrophy.

[first paragraph of article]Hypertrophic cardiomyopathy is clinically defined by the presence of increased left ventricular (LV) wall thickness that is not solely explained by abnormal loading conditions. The aetiology is diverse, but in 60% of patients the disease is an autosomal dominant trait caused by cardiac sarcomere protein gene mutation (HCM). In 10% of cases, the cause is inherited metabolic and neuromuscular disease, chromosomic abnormalities and genetic syndromes, whereas, in the remaining 30% of patients the aetiology remains unknown.

Differences in Actomyosin Function in the Left and Right Ventricles of Human Hearts

In both ventricles of the heart, actin is expressed from the same genes [1]. There are no differences in twitch duration, work performance and power among the right (RV) and left (LV) ventricles in animals [2] So there is no expectation that the properties of actin or myosin isolated from either ventricle would be different. Nevertheless, the situation is more complex in human hearts. The LV must pump more powerfully, because it has to overcome a larger resistance presented by the systemic system than the RV, which has to overcome a lower resistance offered by the pulmonary system. The question arises whether stronger pumping action of the LV is partially caused by the LV actomyosin developing more force than the RV actomyosin. Such a question is impossible to answer by making macroscopic measurements, (such as tension or ATPase activity) because the number of molecules involved in such processes are enormous (of the order of 1011). To obtain molecular information, measurements must be taken from a few molecules. We measured variations in the polarization of fluorescence of a few actomyosin molecules during the contraction cycle and obtained molecular information by calculating its autocorrelation function using R (version 3.3.1). The autocorrelation curve was fitted with a bi-exponential decay model in order to extract the rate constants using XPFIT (version 1.2.1) Alango Ltd. XPFIT employs the Inverse Laplace algorithm in order to numerically invert the decay time domain data. The goodness of fit was assessed by chi-squared. The results suggest that actomyosin function is identical in both ventricles. Refs: 1. Wessels, M.W. and P.J. Willems, Mutations in sarcomeric protein genes not only lead to cardiomyopathy but also to congenital cardiovascular malformations. Clin Genet, 2008. 74(1): p. 16-9. 2. Wikman-Coffelt, J., C. Fenner, A. Smith, and D.T. Mason, Comparative analyses of the kinetics and subunits of myosins from canine skeletal muscle and cardiac tissue. J Biol Chem, 1975. 250(4): p. 1257-62.

Cardiomyopathies with Mixed and Inapparent Morphological Features in Cardiac Troponin I3 Mutation.

The fact that different types of cardiomyopathies can be manifested by the same sarcomere protein gene mutation in a single family is well known. However, mixed features of different types of cardiomyopathies in a single patient have not been well appreciated. We identified a novel mutation in cardiac troponin I3 (Arg186Gly) in the present case, and two of the family members showed mixed morphologic features of hypertrophic cardiomyopathy and left ventricular non-compaction. Moreover, both the features of cardiomyopathies were not apparent for each type of cardiomyopathy. In the patient's family, four other members had unexpected deaths before the age of 30.

Life-long tailoring of management for patients with hypertrophic cardiomyopathy : Awareness and decision-making in changing scenarios.

Hypertrophic cardiomyopathy (HCM) is the most common genetic heart disease, characterised by complex pathophysiology and extensive genetic and clinical heterogeneity. In most patients, HCM is caused by mutations in cardiac sarcomere protein genes and inherited as an autosomal dominant trait. The clinical phenotype ranges from severe presentations at a young age to lack of left ventricular hypertrophy in genotype-positive individuals. No preventative treatment is available as the sequence and causality of the pathomechanisms that initiate and exacerbate HCM are unknown. Sudden cardiac death and end-stage heart failure are devastating expressions of this disease. Contemporary management including surgical myectomy and implantable cardiac defibrillators has shown significant impact on long-term prognosis. However, timely recognition of specific scenarios – including transition to the end-stage phase – may be challenging due to limited awareness of the progression patterns of HCM. This in turn may lead to missed therapeutic opportunities. To illustrate these difficulties, we describe two HCM patients who progressed from the typical hyperdynamic stage of asymmetric septal thickening to end-stage heart failure with severely reduced ejection fraction. We highlight the different stages of this complex inherited cardiomyopathy based on the clinical staging proposed by Olivotto and colleagues. In this way, we aim to provide a practical guide for clinicians and hope to increase awareness for this common form of cardiac disease.

Relationship between aetiology and left ventricular systolic dysfunction in hypertrophic cardiomyopathy

BackgroundSevere left ventricular (LV) systolic dysfunction is an uncommon complication of hypertrophic cardiomyopathy (HCM) that is associated with poor prognosis. Small observational series suggest that patients with rare causes of...

Identification of novel mutations including a double mutation in patients with inherited cardiomyopathy by a targeted sequencing approach using the Ion Torrent PGM system.

Inherited cardiomyopathy is the major cause of sudden cardiac death (SCD) and heart failure (HF). The disease is associated with extensive genetic heterogeneity; pathogenic mutations in cardiac sarcomere protein genes, cytoskeletal protein genes and nuclear envelope protein genes have been linked to its etiology. Early diagnosis is conducive to clinical monitoring and allows for presymptomatic interventions as needed. In the present study, the entire coding sequences and flanking regions of 12 major disease (cardiomyopathy)-related genes [namely myosin, heavy chain 7, cardiac muscle, β (MYH7); myosin binding protein C, cardiac (MYBPC3); lamin A/C (LMNA); troponin I type 3 (cardiac) (TNNI3); troponin T type 2 (cardiac) (TNNT2); actin, α, cardiac muscle 1 (ACTC1); tropomyosin 1 (α) (TPM1); sodium channel, voltage gated, type V alpha subunit (SCN5A); myosin, light chain 2, regulatory, cardiac, slow (MYL2); myosin, heavy chain 6, cardiac muscle, α (MYH6); myosin, light chain 3, alkali, ventricular, skeletal, slow (MYL3); and protein kinase, AMP-activated, gamma 2 non-catalytic subunit (PRKAG2)] in 8 patients with dilated cardiomyopathy (DCM) and in 8 patients with hypertrophic cardiomyopathy (HCM) were amplified and then sequenced using the Ion Torrent Personal Genome Machine (PGM) system. As a result, a novel heterozygous mutation (MYH7, p.Asn885Thr) and a variant of uncertain significance (TNNT2, p.Arg296His) were identified in 2 patients with HCM. These 2 missense mutations, which were absent in the samples obtained from the 200 healthy control subjects, altered the amino acid that was evolutionarily conserved among a number of vertebrate species; this illustrates that these 2 non-synonymous mutations play a role in the pathogenesis of HCM. Moreover, a double heterozygous mutation (PRKAG2, p.Gly100Ser plus MYH7, p.Arg719Trp) was identified in a patient with severe familial HCM, for the first time to the best of our knowledge. This patient provided us with more information regarding the genotype-phenotype correlation between mutations of MYH7 and PRKAG2. Taken together, these findings provide insight into the molecular mechanisms underlying inherited cardiomyopathy. The mutations identified in this study may be further investigated in the future in order to improve the diagnosis and treatment of patients with inherited cardiomyopathy. Furthermore, our findings indicated that sequencing using the Ion Torrent PGM system is a useful approach for the identification of pathogenic mutations associated with inherited cardiomyopathy, and it may be used for the risk evaluation of individuals with a possible susceptibility to inherited cardiomyopathy.