Biophysical mechanisms of myocardium sodium channelopathies

Genetic variants of gene SCN5A encoding the alpha-subunit of cardiac voltage-gated sodium channel Nav1.5 are associated with various diseases, including long QT syndrome (LQT3), Brugada syndrome (BrS1), and progressive cardiac conduction disease (PCCD). In the last decades, the great progress in understanding molecular and biophysical mechanisms of these diseases has been achieved. The LQT3 syndrome is associated with gain-of-function of sodium channels Nav1.5 due to impaired inactivation, enhanced activation, accelerated recovery from inactivation or the late current appearance. In contrast, BrS1 and PCCD are associated with the Nav1.5 loss-of-function, which in electrophysiological experiments can be manifested as reduced current density, enhanced fast or slow inactivation, impaired activation, or decelerated recovery from inactivation. Genetic variants associated with congenital arrhythmias can also disturb interactions of the Nav1.5 channel with different proteins or drugs and cause unexpected reactions to drug administration. Furthermore, mutations can affect post-translational modifications of the channels and their sensitivity to pH and temperature. Here we briefly review the current knowledge on biophysical mechanisms of LQT3, BrS1 and PCCD. We focus on limitations of studies that use heterologous expression systems and induced pluripotent stem cells (iPSC) derived cardiac myocytes and summarize our understanding of genotype-phenotype relations of SCN5A mutations.

In silico analysis of TRPM4 variants of unknown clinical significance

BACKGROUND

TRPM4 is a calcium-activated channel that selectively permeates monovalent cations. Genetic variants of the channel in cardiomyocytes are associated with various heart disorders, such as progressive familial heart block and Brugada syndrome. About97% of all known TRPM4 missense variants are classified as variants of unknown clinical significance (VUSs). The very large number of VUSs is a serious problem in diagnostics and treatment of inherited heart diseases.

METHODS AND RESULTS

We collected 233 benign or pathogenic missense variants in the superfamily of TRP channels from databases ClinVar, Humsavar and Ensembl Variation to compare performance of 22 algorithms that predict damaging variants. We found that ClinPred is the best-performing tool for TRP channels. We also used the paralogue annotation method to identify disease variants across the TRP family. In the set of 565 VUSs of hTRPM4, ClinPred predicted pathogenicity of 299 variants. Among these, 12 variants are also categorized as LP/P variants in at least one paralogue of hTRPM4. We further used the cryo-EM structure of hTRPM4 to find scores of contact pairs between parental (wild type) residues of VUSs for which ClinPred predicts a high probability of pathogenicity of variants for both contact partners. We propose that 68 respective missense VUSs are also likely pathogenic variants.

CONCLUSIONS

ClinPred outperformed other in-silico tools in predicting damaging variants of TRP channels. ClinPred, the paralogue annotation method, and analysis of residue contacts the hTRPM4 cryo-EM structure collectively suggest pathogenicity of 80 TRPM4 VUSs.

Desmin mutations impact the autophagy flux in C2C12 cell in mutation-specific manner

Desmin is the main intermediate filament of striated and smooth muscle cells and plays a crucial role in maintaining the stability of muscle fiber during contraction and relaxation cycles. Being a component of Z-disk area, desmin integrates autophagic pathways, and the disturbance of Z-disk proteins' structure negatively affects chaperone-assisted selective autophagy (CASA). In the present study, we focused on alteration of autophagy flux in myoblasts expressing various Des mutations. We applied Western blotting, immunocytochemistry, RNA sequencing, and shRNA approach to demonstrate that DesS12F, DesA357P, DesL345P, DesL370P, and DesD399Y mutations. Mutation-specific effect on autophagy flux being most severe in aggregate-prone Des mutations such as DesL345P, DesL370P, and DesD399Y. RNA sequencing data confirmed the most prominent effect of these mutations on expression profile and, in particular, on autophagy-related genes. To verify CASA contribution to desmin aggregate formation, we suppressed CASA by knocking down Bag3 and demonstrated that it promoted aggregate formation and lead to downregulation of Vdac2 and Vps4a and upregulation of Lamp, Pink1, and Prkn. In conclusion, Des mutations showed a mutation-specific effect on autophagy flux in C2C12 cells with either a predominant impact on autophagosome maturation or on degradation and recycling processes. Aggregate-prone desmin mutations lead to the activation of basal autophagy level while suppressing the CASA pathway by knocking down Bag3 can promote desmin aggregate formation.

miR-21, miR-93, miR-191, miR-let-7b, and miR-499 Expression Level in Plasma and Cerebrospinal Fluid in Patients with Prolonged Disorders of Consciousness

In recent decades, significant progress has been achieved in understanding the mechanisms of disturbance and restoration of consciousness in patients after severe brain damage resulting in prolonged disorders of consciousness (pDOC). MicroRNAs (miRs) may be potential candidates as possible biomarkers for the classification of disease subtypes, and prognosis in patients with pDOC. The aim of the study was to analyze miRs expression levels (hsa-miR-21-5p, hsa-miR-93-5p, hsa-miR-191-5p, mmu-miR-499-5p, hsa-let-7b-5p) by a real-time polymerase chain reaction in plasma and cerebrospinal fluid (CSF) from patients with pDOC and to identify a potential biomarker for dividing patients into groups according to disease severity. We analyzed the levels of investigated miRs in pDOC patients, divided by etiology, CRSI, and the total group compared with controls. Our results showed that dividing patients with pDOC into groups according to the etiology of the disease resulted in the most significant differences in the levels of miR-93, -21, and -191 in CSF and plasma samples between groups of patients. Among the analyzed miRs, we did not find a marker that would help to distinguish VS/UWS patient groups from MCS. Examining of miRs as possible prognostic markers in patients with pDOC, the starting point seems to be the cause that led to the development of the disease.

Characterization of the novel heterozygous SCN5A genetic variant Y739D associated with Brugada syndrome

Genetic variants in SCN5A gene were identified in patients with various arrhythmogenic conditions including Brugada syndrome. Despite significant progress of last decades in studying the molecular mechanism of arrhythmia-associated SCN5A mutations, the understanding of relationship between genetics, electrophysiological consequences and clinical phenotype is lacking. We have found a novel genetic variant Y739D in the SCN5A-encoded sodium channel Na_v1.5 of a male patient with Brugada syndrome (BrS). The objective of the study was to characterize the biophysical properties of Na_v1.5-Y739D and provide possible explanation of the phenotype observed in the patient. The WT and Y739D channels were heterologously expressed in the HEK-293T cells and the whole-cell sodium currents were recorded. Substitution Y739D reduced the sodium current density by 47 ± 2% at −20 mV, positively shifted voltage-dependent activation, accelerated both fast and slow inactivation, and decelerated recovery from the slow inactivation. The Y739D loss-of-function phenotype likely causes the BrS manifestation. In the hNa_v1.5 homology models, which are based on the cryo-EM structure of rat Na_v1.5 channel, Y739 in the extracellular loop IIS1-S2 forms H-bonds with K1381 and E1435 and pi-cation contacts with K1397 (all in loop IIIS5-P1). In contrast, Y739D accepts H-bonds from K1397 and Y1434. Substantially different contacts of Y739 and Y739D with loop IIIS5-P1 would differently transmit allosteric signals from VSD-II to the fast-inactivation gate at the N-end of helix IIIS5 and slow-inactivation gate at the C-end of helix IIIP1. This may underlie the atomic mechanism of the Y739D channel dysfunction.

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A novel BrS-associated genetic variant Y739D in gene SCN5A is identified.

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Y739D caused Nav1.5 loss-of-function by enhancing slow and fast inactivation.

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Y739 in loop IIS1-S2 forms H-bonds and pi-cation contacts with loop IIIS5-P1.

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The contacts may mediate signal transfer from VSD-II to two inactivation gates.

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Altered contacts of Y739D would affect the allosteric signal transduction.

Mechanisms of Regenerative Potential Activation in Cardiac Mesenchymal Cells

Recovery of the contractile function of the heart and the regeneration of the myocardium after ischemic injury are contemporary issues in regenerative medicine and cell biology. This study aimed to analyze early transcriptional events in cardiac tissue after infarction and to explore the cell population that can be isolated from myocardial tissue. We induced myocardial infarction in Wistar rats by permanent ligation of the left coronary artery and showed a change in the expression pattern of Notch-associated genes and Bmp2/Runx2 in post-MI tissues using RNA sequencing and RT-PCR. We obtained primary cardiac mesenchymal cell (CMC) cultures from postinfarction myocardium by enzymatic dissociation of tissues, which retained part of the activation stimulus and had a pronounced proliferative potential, assessed using a “xCELLigence” real-time system. Hypoxia in vitro also causes healthy CMCs to overexpress Notch-associated genes and Bmp2/Runx2. Exogenous activation of the Notch signaling pathway by lentiviral transduction of healthy CMCs resulted in a dose-dependent activation of the Runx2 transcription factor but did not affect the activity of the Bmp2 factor. Thus, the results of this study showed that acute hypoxic stress could cause short-term activation of the embryonic signaling pathways Notch and Bmp in CMCs, and this interaction is closely related to the processes of early myocardial remodeling after a heart attack. The ability to correctly modulate and control the corresponding signals in the heart can help increase the regenerative capacity of the myocardium before the formation of fibrotic conditions.

Practical guidelines for the diagnosis and treatment of transthyretin amyloid cardiomyopathy (ATTR-CM or transthyretin cardiac amyloidosis)

This paper summarizes the data from updated international protocols and guidelines for diagnosis of transthyretin amyloid cardiomyopathy (ATTR-CM). The invasive and non-invasive diagnosis techniques and their combinations are briefly reviewed; the evidentiary foundations for each diagnostic option and tool are analyzed. The paper describes a customized algorithm for sequential diagnosis and differential diagnosis of patients with suspected ATTR-CM with allowance for the combination of clinical signs and diagnostic findings. Along with the awareness of primary care providers about the red flags of the disease and visualization criteria, as well as providing information to the patients about the possibility of performing therapy of ATTR amyloidosis and the risks of delayed diagnosis, the proposed algorithm enables timely patient routing and prescribing specific treatment.

Intersegment Contacts of Potentially Damaging Variants of Cardiac Sodium Channel

Over 1,500 missense variants of sodium channel hNav1.5, which are reported in the ClinVar database, are associated with cardiac diseases. For most of the variants, the clinical significance is uncertain (VUS), not provided (NP), or has conflicting interpretations of pathogenicity (CIP). Reclassifying these variants as pathogenic/likely pathogenic (P/LP) variants is important for diagnosing genotyped patients. In our earlier work, several bioinformatics tools and paralogue annotation method consensually predicted that 74 VUS/NP/CIP variants of 54 wild type residues (set w54) are potentially damaging variants (PDVs). Atomic mechanisms underlying dysfunction of the PDVs are unknown. Here we employed a recent cryo-EM structure of the hNav1.5 channel with likely inactivated pore domain (PD) and activated voltage-sensing domains (VSDs), and ad hoc models of the closed and open PD and resting VSDs to explore intersegment contacts of w54 residues. We found that 44 residues from set w54 contact 84 residues with 118 disease missense variants. These include 104 VUS/NP/CIP variants, most of which are associated with the loss-of-function Brugada syndrome (BrS1) or gain-of-function long QT syndrome (LQT3). Matrix representation of the PDVs and their contact variants facilitated recognition of coupled mutations associated with the same disease. In particular, BrS1-associated coupled mutations, which disturb the P-loops region with the selectivity filter slow inactivation gate, would cause the channel dysfunction. Other likely causes of the channel dysfunction include coupled BrS1-associated variants within VSDs that would destabilize their activated states and coupled LQT3-associated variants, which would stabilize the open PD or activated VSDs. Our study proposes mechanisms of channel dysfunction for scores of BrS1- and LQT3-associated variants, confirms status for 82% of PDVs, and suggests damaging status for their contact variants, which are currently categorized as VUS/NP/CIP variants.

Possible Interactions of Extracellular Loop IVP2-S6 With Voltage-Sensing Domain III in Cardiac Sodium Channel

Motion transmission from voltage sensors to inactivation gates is an important problem in the general physiology of ion channels. In a cryo-EM structure of channel hNa_v1.5, residues N1736 and R1739 in the extracellular loop IVP2-S6 approach glutamates E1225 and E1295, respectively, in the voltage-sensing domain III (VSD-III). ClinVar-reported variants E1230K, E1295K, and R1739W/Q and other variants in loops IVP2-S6, IIIS1-S2, and IIIS3-S4 are associated with cardiac arrhythmias, highlighting the interface between IVP2-S6 and VSD-III as a hot spot of disease mutations. Atomic mechanisms of the channel dysfunction caused by these mutations are unknown. Here, we generated mutants E1295R, R1739E, E1295R/R1739E, and N1736R, expressed them in HEK-293T cells, and explored biophysical properties. Mutation E1295R reduced steady-state fast inactivation and enhanced steady-state slow inactivation. In contrast, mutation R1739E slightly enhanced fast inactivation and attenuated slow inactivation. Characteristics of the double mutant E1295R/R1739E were rather similar to those of the wild-type channel. Mutation N1736R attenuated slow inactivation. Molecular modeling predicted salt bridging of R1739E with the outermost lysine in the activated voltage-sensing helix IIIS4. In contrast, the loss-of-function substitution E1295R repelled R1739, thus destabilizing the activated VSD-III in agreement with our data that E1295R caused a depolarizing shift of the G-V curve. In silico deactivation of VSD-III with constraint-maintained salt bridge E1295-R1739 resulted in the following changes: 1) contacts between IIIS4 and IVS5 were switched; 2) contacts of the linker-helix IIIS4-S5 with IVS5, IVS6, and fast inactivation tripeptide IFM were modified; 3) contacts of the IFM tripeptide with helices IVS5 and IVS6 were altered; 4) mobile loop IVP2-S6 shifted helix IVP2 that contributes to the slow inactivation gate and helix IVS6 that contributes to the fast inactivation gate. The likelihood of salt bridge E1295-R1739 in deactivated VSD-III is supported by Poisson–Boltzmann calculations and state-dependent energetics of loop IVP2-S6. Taken together, our results suggest that loop IVP2-S6 is involved in motion transmission from VSD-III to the inactivation gates.

Molecular background of impairments in skeletal muscle of heart failure patients

Background

Heart failure (HF) is characterised by systematic inflammation and chronic metabolic dysregulation. HF enhances the release of pro-inflammatory cytokines, induces activation of the complement system, production of autoantibodies, and over-expression of the major histocompatibility (MHC) complex class II molecules. It is known that skeletal muscles are exposed to the immunologic injury in disease; and muscle tissue appeared to be affected by HF leading to the muscle weakness and exercise intolerance development. However, molecular abnormalities occurring in HF patients' muscles and the mechanisms underlying its development are not clarified.

Purpose

To understand the molecular mechanisms underlying skeletal muscle immune and non-immune impairments in HF.

Methods

8 health donors and 5 HF patients with reduced ejection fraction (NYHA Class II and III) were enrolled in this study in accordance with the principles under the Declaration of Helsinki (1989). mRNA of skeletal muscle biopsies of gastrocnemius lateralis were sequenced on Illumina HiSeq. RNA-seq analysis was performed using STAR with reference genome GRCh38 and featureCounts program; differentially expressed genes (DEGs) were assessed using R package DESeq2 with FDR=0.01 and log2 fold change (l2fc) >1.5 filter; pathway analysis was performed using clusterProfiler in R (FDR=0.01).

Results

1404 differentially expressed genes distinguish muscles of HF patients and controls. Among upregulated genes there are different classical MHC molecules and specific one HLA-G (l2fc=2) that has been previously shown appeared in muscles under autoimmune myopathies, and potentially protect them. Unregulated DEGs were responsible for the activation of many molecular immunological pathways: type I interferon signaling pathway (16 DEGs out of total 89), regulation of T cell proliferation (14/153), neutrophil degranulation (31/485), granulocyte differentiation (7/32), negative regulation of viral process (11/53), that indicates about specific inflammatory response in HF muscles. Response to hypoxia (22/314) and gluconeogenesis pathways (12/87) were also activated. Downregulated genes include SLC5A1 (l2fc=−4) sodium glucose cotransporter; NRP3 (l2fc=−4) that plays a role in modulating intravascular volume and vascular tone; MMP1 (l2fc=−13) involved in the breakdown of extracellular matrix; the expression of many genes responsible for DNA-repair (44/534) and cilium assembly (34/366) was also suppressed.

Conclusion

Transcriptome analysis shows immunological and non-immunological alterations in HF skeletal muscles and provides the information about molecular mechanisms of its development.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Russian Science Foundation grant

Emery-Dreifuss muscular dystrophy presenting as a heart rhythm disorders in children

Introduction

Emery-Dreifuss muscular dystrophy (EDMD) is an inherited muscle dystrophy often accompanied by cardiac abnormalities in the form of supraventricular arrhythmias, conduction defects, sinus node dysfunction. Cardiac phenotype typically arises years after skeletal muscle presentations, though, can be severe and life-threatening. The disease usually manifests during the third decade of life with elbow joint contractions and progressive muscle weakness and atrophy.

Objective

To present our clinical experience of diagnosis and treatment of arrhythmias in children with Emery-Dreifuss muscular dystrophy

Materials and methods

We enrolled 5 patients with different forms of EDMD (X-linked and autosomal dominant) linked to the mutations in EMD and LMNA genes, presented with early onset of cardiac abnormalities and no leading skeletal muscle phenotype. The predominant forms of cardiac pathology were atrial flutter, atrial fibrillation and conduction disturbances that progress over time.

Clinical examination included physical examination, 12-lead electrocardiography, Holter ECG monitoring (HM), transthoracic echocardiography, neurological examination and biochemical and hormone tests. Also we performed CMR, electrophysiological study (EPS), treadmill test of some patients. One patient underwent an endomyocardial biopsy to exclude inflammatory heart disease. Target sequencing was performed using a panel of 108 or 172 genes

Results

We observed five patients with EDMD and cardiac debut during first-second decades of life: 3 with 1st subtype (variants in EMD gene) and 2 with 2nd subtype (variants in LMNA gene). All patients were males. The mean age of cardiac manifestation was 13,2±3,11 (from 9 to 16 y.o.). The mean follow-up period was 7,4±2,6 years.

All patients presented with sinus node dysfunction and four out of five with AV conduction abnormalities. The leading arrhythmic phenotypes included various types of supraventricular arrhythmias: multifocal atrial tachycardia (AT) (n=4), premature atrial captures (PACs) (n=4), atrial flutter, (AF) (n=3), atrial fibrillation (AFib) (n=3) and AV nodal recurrent tachycardia (AVRNT). Heart rhythm disorders were the first manifestation in all three patients with 1st EDMD subtype. Radiofrequency ablation was performed in 2 patients, one of them received permanent pacemaker implantation.

Conclusions

In conclusion, while being the rare cases, heart rhythm disorders can represent the first and for a long time, the only clinical symptom of EDMD even in the pediatric group of patients. Therefore, thorough laboratory and neurological screening along with genetic studies, are of importance in each pediatric patient presenting with complex heart rhythm disorders of primary supraventricular origin to exclude EDMD or other neuromuscular disorders.

Funding Acknowledgement

Type of funding sources: None.

Regulatory Action of Plasma from Patients with Obesity and Diabetes towards Muscle Cells Differentiation and Bioenergetics Revealed by the C2C12 Cell Model and MicroRNA Analysis

Obesity and type 2 diabetes mellitus (T2DM) are often combined and pathologically affect many tissues due to changes in circulating bioactive molecules. In this work, we evaluated the effect of blood plasma from obese (OB) patients or from obese patients comorbid with diabetes (OBD) on skeletal muscle function and metabolic state. We employed the mouse myoblasts C2C12 differentiation model to test the regulatory effect of plasma exposure at several levels: (1) cell morphology; (2) functional activity of mitochondria; (3) expression levels of several mitochondria regulators, i.e., Atgl, Pgc1b, and miR-378a-3p. Existing databases were used to computationally predict and analyze mir-378a-3p potential targets. We show that short-term exposure to OB or OBD patients' plasma is sufficient to affect C2C12 properties. In fact, the expression of genes that regulate skeletal muscle differentiation and growth was downregulated in both OB- and OBD-treated cells, maximal mitochondrial respiration rate was downregulated in the OBD group, while in the OB group, a metabolic switch to glycolysis was detected. These alterations correlated with a decrease in ATGL and Pgc1b expression in the OB group and with an increase of miR-378a-3p levels in the OBD group.

AL-amyloidosis with cardiac involvement. Diagnostic capabilities of non-invasive methods

There are presented the literature data and a description of the clinical course of the disease in isolated/predominant cardiac amyloidosis. Amyloid cardiomyopathy is the most common phenocopy of hypertrophic cardiomyopathy. The modern possibilities of non-invasive diagnostics using osteoscintigraphy for the differential diagnosis between amyloid cardiomyopathy caused by AL- and transthyretin amyloidosis are described in detail.

Different Expressions of Pericardial Fluid MicroRNAs in Patients With Arrhythmogenic Right Ventricular Cardiomyopathy and Ischemic Heart Disease Undergoing Ventricular Tachycardia Ablation

Introduction: Pericardial fluid is enriched with biologically active molecules of cardiovascular origin including microRNAs. Investigation of the disease-specific extracellular microRNAs could shed light on the molecular processes underlying disease development. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart disease characterized by life-threatening arrhythmias and progressive heart failure development. The current data about the association between microRNAs and ARVC development are limited.

Methods and Results: We performed small RNA sequence analysis of microRNAs of pericardial fluid samples obtained during transcutaneous epicardial access for ventricular tachycardia (VT) ablation of six patients with definite ARVC and three post-infarction VT patients. Disease-associated microRNAs of pericardial fluid were identified. Five microRNAs (hsa-miR-1-3p, hsa-miR-21-5p, hsa-miR-122-5p, hsa-miR-206, and hsa-miR-3679-5p) were found to be differentially expressed between patients with ARVC and patients with post-infarction VT. Enrichment analysis of differentially expressed microRNAs revealed their close linkage to cardiac diseases.

Conclusion: Our data extend the knowledge of pericardial fluid microRNA composition and highlight five pericardial fluid microRNAs potentially linked to ARVC pathogenesis. Further studies are required to confirm the use of pericardial fluid RNA sequencing in differential diagnosis of ARVC.

Association of Common Genetic Risk Variants With Gestational Diabetes Mellitus and Their Role in GDM Prediction

OBJECTIVE

We aimed to explore the associations between common genetic risk variants with gestational diabetes mellitus (GDM) risk in Russian women and to assess their utility in the identification of GDM cases.

METHODS

We conducted a case-control study including 1,142 pregnant women (688 GDM cases and 454 controls) enrolled at Almazov National Medical Research Centre. The International Association of Diabetes and Pregnancy Study Groups criteria were used to diagnose GDM. A total of 11 single- nucleotide polymorphisms (SNPs), including those in HKDC1 (rs10762264), GCK (rs1799884), MTNR1B (rs10830963 and rs1387153), TCF7L2 (rs7903146 and rs12255372), KCNJ11 (rs5219), IGF2BP2 (rs4402960), IRS1 (rs1801278), FTO (rs9939609), and CDKAL1 (rs7754840) were genotyped using Taqman assays. A logistic regression model was used to calculate odds ratios (ORs) and their confidence intervals (CIs). A simple-count genetic risk score (GRS) was calculated using 6 SNPs. The area under the receiver operating characteristic curve (c-statistic) was calculated for the logistic regression model predicting the risk of GDM using clinical covariates, SNPs that had shown a significant association with GDM in our study, GRS, and their combinations.

RESULTS

Two variants in MTNR1B (rs1387153 and rs10830963) demonstrated a significant association with an increased risk of GDM. The association remained significant after adjustment for age, pre-gestational BMI, arterial hypertension, GDM in history, impaired glucose tolerance, polycystic ovary syndrome, family history of diabetes, and parity (P = 0.001 and P < 0.001, respectively). After being conditioned by each other, the effect of rs1387153 on GDM predisposition weakened while the effect of rs10830963 remained significant (P = 0.004). The risk of GDM was predicted by clinical variables (c-statistic 0.712, 95 % CI: 0.675 - 0.749), and the accuracy of prediction was modestly improved by adding GRS to the model (0.719, 95 % CI 0.682 - 0.755), and more by adding only rs10830963 (0.729, 95 % CI 0.693 - 0.764).

CONCLUSION

Among 11 SNPs associated with T2D and/or GDM in other populations, we confirmed significant association with GDM for two variants in MTNR1B in Russian women. However, these variants showed limited value in the identification of GDM cases.

LMNA Mutations G232E and R482L Cause Dysregulation of Skeletal Muscle Differentiation, Bioenergetics, and Metabolic Gene Expression Profile

Laminopathies are a family of monogenic multi-system diseases resulting from mutations in the LMNA gene which include a wide range of neuromuscular disorders. Although lamins are expressed in most types of differentiated cells, LMNA mutations selectively affect only specific tissues by mechanisms that remain largely unknown. We have employed the combination of functional in vitro experiments and transcriptome analysis in order to determine how two LMNA mutations associated with different phenotypes affect skeletal muscle development and metabolism. We used a muscle differentiation model based on C2C12 mouse myoblasts genetically modified with lentivirus constructs bearing wild-type human LMNA (WT-LMNA) or R482L-LMNA/G232E-LMNA mutations, linked to familial partial lipodystrophy of the Dunnigan type and muscular dystrophy phenotype accordingly. We have shown that both G232E/R482L-LMNA mutations cause dysregulation in coordination of pathways that control cell cycle dynamics and muscle differentiation. We have also found that R482/G232E-LMNA mutations induce mitochondrial uncoupling and a decrease in glycolytic activity in differentiated myotubes. Both types of alterations may contribute to mutation-induced muscle tissue pathology.

Systematic dissection of biases in whole-exome and whole-genome sequencing reveals major determinants of coding sequence coverage

Advantages and diagnostic effectiveness of the two most widely used resequencing approaches, whole exome (WES) and whole genome (WGS) sequencing, are often debated. WES dominated large-scale resequencing projects because of lower cost and easier data storage and processing. Rapid development of 3^rd generation sequencing methods and novel exome sequencing kits predicate the need for a robust statistical framework allowing informative and easy performance comparison of the emerging methods. In our study we developed a set of statistical tools to systematically assess coverage of coding regions provided by several modern WES platforms, as well as PCR-free WGS. We identified a substantial problem in most previously published comparisons which did not account for mappability limitations of short reads. Using regression analysis and simple machine learning, as well as several novel metrics of coverage evenness, we analyzed the contribution from the major determinants of CDS coverage. Contrary to a common view, most of the observed bias in modern WES stems from mappability limitations of short reads and exome probe design rather than sequence composition. We also identified the ~ 500 kb region of human exome that could not be effectively characterized using short read technology and should receive special attention during variant analysis. Using our novel metrics of sequencing coverage, we identified main determinants of WES and WGS performance. Overall, our study points out avenues for improvement of enrichment-based methods and development of novel approaches that would maximize variant discovery at optimal cost.

P195 Postinfarction myocardial remodelling according to 2D ECHO data and genetic predictors: effect of genetic common variants in HSPB7 and MADD genes

Purpose

To study the impact of genetic variants rs1739843, rs2290149 and rs10838692 in HSPB7 and MADD genes on myocardial remodeling in the patients with postinfarction cardiosclerosis.

Methods and Results. The study included 252 men aged 30-65 y.o., who had MI more than 1 year ago. All patients had Q-MI of the anterior wall of the LV. Echocardiography was performed by the standard method (Vivid S6, GE, USA). Arterial hypertension (AH) was registered in more than 60% patients. Myocardial revascularization (CABG/PCI) was performed in more than in 50% of cases. Among 252 cases studies 156 patients had HFrEF (II–IV NYHA) LVEF (Sim)&lt;40% (№1 group) and 96 patients had no clinical signs of HF and LVEF (Sim)&gt;55% (№2 group). The groups were comparable in the AH prevalence and age. Patients all groups were on optimal drug therapy. Polymorphic genetic variants were studies using real-time-PCR. Eccentric types of LV remodeling prevailed in group 1 and concentric types of LV remodeling prevailed in group 2 (p &lt; 0.001). The presence AH combined with CC genotype of rs1739843 in HSPB7 gene and TT genotype of rs2290149 in MADD and simultaneous carriage of the CC genotype of rs1739843 HSPB7 were associated with the presence of non-dilated ventricle (LV volume index ≤75 mL/m2) and relative wall thickness (RWT) &gt;0.42 independently to LV mass index (p = 0.03). The T allele of rs1739843 HSPB7 (p = 0.006) and a combination of T allele of rs1739843 HSPB7 with the TT genotype of rs2290149 of the MADD gene were associated with the presence of dilated ventricles (p = 0.009) with LV hypertrophy (LV mass index &gt;115 g/m2) independently to RWT.

Conclusion

Our preliminary data demonstrate that the genotype of HSPB7 (rs1739843) can modulated the association of AH and MADD rs2290149 with markers of ventricular hypertrophy and predispose to various types of post-MI remodeling of LV.

[Left ventricular non - compaction: contemporary view of genetic background, clinical course, diagnostic and treatment]

This review highlights and discusses recent advances in understanding left ventricular non - compaction (LVNC). Clinical profile, prognosis and even diagnosis are still a great challenge faced by the world. The population prevalence of left ventricular non - compaction remains unknown. High variability of clinical manifestations, genetic heterogenity with overlap of different phenotypes, variability of hereditary patterns suggests that LVNC seems to be rather an isolated trait or a part of phenotypic expression of different cardiac diseases or complex genetic syndromes.

P1597Two novel mutations in SCN5A gene cause enhanced inactivation and lead to Brugada syndrome

Background

Mutations in gene SCN5A, encoding cardiac potential-dependent sodium channel Nav1.5, are associated with various arrhythmogenic disorders among which the Brugada syndrome (BrS) and the Long QT syndrome (LQT) are the best characterized. BrS1 is associated with sodium channel dysfunction, which can be reflected by decreased current, impaired activation and enhanced inactivation. We found two novel mutations in our patients with BrS and explored their effect on fast and slow inactivation of cardiac sodium channel.

Purpose

The aim of this study was to investigate the effect of BrS (Y739D, L1582P) mutations on different inactivation processes in in vitro model.

Methods

Y739D and L1582P substitutions were introduced in SCN5A cDNA using site-directed mutagenesis. Sodium currents were recorded at room temperature in transfected HEK293-T cells using patch-clamp technique with holding potential −100 mV. In order to access the fast steady-state inactivation curve we used double-pulse protocol with 10 ms prepulses. To analyze voltage-dependence of slow inactivation we used two-pulse protocol with 10s prepulse, 20ms test pulse and 25ms interpulse at −100mV to allow recovery from fast inactivation. Electrophysiological measurements are presented as mean ±SEM.

Results

Y739D mutation affects highly conserved tyrosine 739 among voltage-gated sodium and calcium channels in the segment IIS2. Mutation L1582P located in the loop IVS4-S5, and leucine in this position is not conserved among voltage-gated channels superfamily. We have shown that Y739D leads to significant changes in both fast and slow inactivation, whereas L1582P enhanced slow inactivation only. Steady-state fast inactivation for Y739D was shifted on 8.9 mV towards more negative potentials compare with that for WT, while L1582P did not enhanced fast inactivation (V1/2 WT: −62.8±1.7 mV; Y739D: −71.7±2.3 mV; L1582P: −58.7±1.4 mV). Slow inactivation was increased for both substitutions (INa (+20mV)/INa (−100mV) WT: 0.45±0.03; Y739D: 0,34±0.09: L1582P: 0.38±0.04).

Steady-state fast inactivation

Conclusions

Both mutations, observed in patients with Brugada syndrome, influence on the slow inactivation process. Enhanced fast inactivation was shown only for Y739D mutant. The more dramatic alterations in sodium channel biophysical characteristics are likely linked with mutated residue conservativity.

Acknowledgement/Funding

RSF #17-15-01292

P904Heart rhythm and conduction disorders in children with restrictive cardiomyopathy

Introduction

Restrictive cardiomyopathy (RCMP) is characterized by restrictive filling and reduced diastolic volume of either or both ventricles with normal or near-normal systolic function and wall thickness. It may occur idiopathically or as a cardiac manifestation of systemic diseases and various neuromuscular disorders. Often RCMP occurs with severe symptoms of heart failure and has an poor prognosis. Given the presence of structural myocardial abnormalities, atrial dilatation, this group of patients has a high risk of heart rhythm and conduction disturbances.

Objective

To present our clinical experience in RCMP with the heart rhythm and conduction disturbances in children.

Material and methods

The study was approved by the Institute Ethical Review Board. On behalf of the children enrolled in the study, written informed consent was obtained from the next of kin. The study included 18 children with RCMP presented with heart failure class II-IV. The genotyping was performed to all patients. The identified genetic variants were classified according to ACMG guidelines. We analyzed clinical history, data of physical examination, laboratory findings, ECG, echocardiography, Holter monitoring, genetic test, cardiac MRI and CT performed according to clinical indications and physician's.

Results

Mean age of RCMP manifestation was 2,1 y.o. [0–11] with HF as a main clinical feature. Rhythm and conduction disorders were reported in 83% (n=15) of children. The structure of the disorders included: atriventricular block 1–2 degrees in 22% (n=4), supraventricular disorders (extrasystole, tachycardia, atrial fibrillation) in 44% (n=8), ventricular disorders (extrasystole, tachycardia) in 16% of patients (n=3). One patient had a combined rhythm and conduction disorder (sinus sick syndrome, atrial fibrillation, supraventricular and ventricular tachycardia), which required implantation of a pacemaker with a defibrillator function. In one patient, the manifestation of the disease was with hemodynamically significant permanent-recurrent atrial tachycardia. Mortality in this group of patients was 27% (= 5), the cause of death was the progression of heart failure in 3 children and sudden arrhythmial death in 2 patients.

Conclusions

Thus, RCMP is a severe, genetically caused, with early manifestation progressive disease with high risks of rhythm and conduction disturbances, sudden arrhythmial death. According to the testimony, patients should receive antiarrhythmic therapy and, if necessary, pacemaker implantation is indicated.

[Hypertrophic cardiomyopathy: modern aspects of pharmacologic treatment]

This article discusses recent advances in understanding genetic basis and classification of hypertrophic cardiomyopathy. Here, we review pharmacologic treatment strategies and new developments in disease - specific management of HCM.

Extracellular MicroRNAs and Mitochondrial DNA as Potential Biomarkers of Arrhythmogenic Cardiomyopathy

Differential diagnosis of arrhythmogenic cardiomyopathy (ACM) during the disease latent phase is a challenging clinical problem that requires identification of early ACM biomarkers. Because extracellular nucleic acids are stable, specific, and can be easily detected, they can be used as reliable biomarkers of various diseases. In this study, we analyzed the levels of extracellular microRNAs and mitochondrial DNA in the conditioned medium collected from cardiomyocytes differentiated from induced pluripotent stem cells of ACM patients and healthy donor. Several microRNAs were expressed differently by the affected and healthy cardiomyocytes; therefore, they could be considered as potential ACM biomarkers.

Atomic Mechanisms of Timothy Syndrome-Associated Mutations in Calcium Channel Cav1.2

Timothy syndrome (TS) is a very rare multisystem disorder almost exclusively associated with mutations G402S and G406R in helix IS6 of Cav1.2. Recently, mutations R518C/H in helix IIS0 of the voltage sensing domain II (VSD-II) were described as a cause of cardiac-only TS. The three mutations are known to decelerate voltage-dependent inactivation (VDI). Here, we report a case of cardiac-only TS caused by mutation R518C. To explore possible impact of the three mutations on interdomain contacts, we modeled channel Cav1.2 using as templates Class Ia and Class II cryo-EM structures of presumably inactivated channel Cav1.1. In both models, R518 and several other residues in VSD-II donated H-bonds to the IS6-linked α1-interaction domain (AID). We further employed steered Monte Carlo energy minimizations to move helices S4–S5, S5, and S6 from the inactivated-state positions to those seen in the X-ray structures of the open and closed NavAb channel. In the open-state models, positions of AID and VSD-II were similar to those in Cav1.1. In the closed-state models, AID moved along the β subunit (Cavβ) toward the pore axis and shifted AID-bound VSD-II. In all the models R518 retained strong contacts with AID. Our calculations suggest that conformational changes in VSD-II upon its deactivation would shift AID along Cavβ toward the pore axis. The AID-linked IS6 would bend at flexible G402 and G406, facilitating the activation gate closure. Mutations R518C/H weakened the IIS0-AID contacts and would retard the AID shift. Mutations G406R and G402S stabilized the open state and would resist the pore closure. Several Cav1.2 mutations associated with long QT syndromes are consistent with this proposition. Our results provide a mechanistic rationale for the VDI deceleration caused by TS-associated mutations and suggest targets for further studies of calcium channelopathies.

Cellular Mechanisms of Aortic Valve Calcification

Comparative in vitro study examined the osteogenic potential of interstitial cells of aortic valve obtained from the patients with aortic stenosis and from control recipients of orthotopic heart transplantation with intact aortic valve. The osteogenic inductors augmented mineralization of aortic valve interstitial cells (AVIC) in patients with aortic stenosis in comparison with the control level. Native AVIC culture of aortic stenosis patients demonstrated overexpression of osteopontin gene (OPN) and underexpression of osteoprotegerin gene (OPG) in comparison with control levels. In both groups, AVIC differentiation was associated with overexpression of RUNX2 and SPRY1 genes. In AVIC of aortic stenosis patients, expression of BMP2 gene was significantly greater than the control level. The study revealed an enhanced sensitivity of AVIC to osteogenic inductors in aortic stenosis patients, which indicates probable implication of OPN, OPG, and BMP2 genes in pathogenesis of aortic valve calcification.

EXTRACELLULAR VESICLES FROM BLOOD PLASMA STUDIED BY LOW VOLTAGE SCANNING ELECTRON MICROSCOPY

Extracellular vesicles are subspherical membranous structures secreted by cells and enriched with different types of biological molecules. The number and the molecular content of these structures depend on pathological conditions and the physiological state of the organism. Extracellular vesicles play an important role in intercellular communication and represent potential disease biomarkers. However, mechanisms of formation, functions and morphological characteristics of extracellular vesicles are still studied insufficiently. Low voltage scanning electron microscopy is a promising method to investigate extracellular vesicles, since it does not require conductive coating and therefore enables a high-resolution visualization of morphological details of nanosized objects. This paper presents the results of low voltage scanning electron microscopy study of morphology and size of objects from blood plasma fractions.

THE ROLE OF LMNA MUTATIONS IN MYOGENIC DIFFERENTIATION OF PRIMARY SATELLITE CELLS AND C2C12 CELLS

Nuclear lamins form nuclear lamina localized under the inner nuclear membrane. It was previously considered that the nuclear lamina predominantly plays a structural role, however, its involvement have been recently described in the regulatory processes such as chromatin organization and gene transcription. It is known that mutations in the LMNA gene lead to the development of a large number of diseases, laminopathies, which mainly affect mesenchymal tissue. Nowadays, the mechanisms by which the lamina can regulate cell differentiation remain incompletely understood. In the present work, we have studied the effect of LMNA gene mutations on the process of muscle differentiation of primary satellite cells and Ñ2Ñ12 cell line. The genome of satellite cells and Ñ2Ñ12 cell line was modified by the introduction of lentiviral constructs encoding LMNA G232E associated with the development of muscular dystrophy Emery—Dreyfus and LMNA R571S associated with the development of dilated cardiomyopathy. The morphology of the cells was estimated using immunofluorescence, the expression level of myogenic genes were analyzed by qPCR. We have shown that the analyzed mutations reduce the ability of cells to differentiate, to fuse and to form myotubes. We have suggested that it is due to enhanced expression of markers at the early stages and to reduced expression markers at the late stages of myogenesis. Therefore, mutations in nuclear lamins can influence the process of muscle differentiation.

Chicken rRNA Gene Cluster Structure

Ribosomal RNA (rRNA) genes, whose activity results in nucleolus formation, constitute an extremely important part of genome. Despite the extensive exploration into avian genomes, no complete description of avian rRNA gene primary structure has been offered so far. We publish a complete chicken rRNA gene cluster sequence here, including 5'ETS (1836 bp), 18S rRNA gene (1823 bp), ITS1 (2530 bp), 5.8S rRNA gene (157 bp), ITS2 (733 bp), 28S rRNA gene (4441 bp) and 3'ETS (343 bp). The rRNA gene cluster sequence of 11863 bp was assembled from raw reads and deposited to GenBank under KT445934 accession number. The assembly was validated through in situ fluorescent hybridization analysis on chicken metaphase chromosomes using computed and synthesized specific probes, as well as through the reference assembly against de novo assembled rRNA gene cluster sequence using sequenced fragments of BAC-clone containing chicken NOR (nucleolus organizer region). The results have confirmed the chicken rRNA gene cluster validity.

[PROTEIN KINASE C EXPRESSION FOLLOWING REMOTE ISCHEMIC PRECONDITIONING IN CARDIAC SURGERY]

OBJECTIVE

To evaluate cardioprotective effects of remote ischemic preconditioning (RIPC) in cardiac surgery patients undergoing aortic valve replacement depending on the type of anesthesia and investigate the level of myocardial protein kinase C epsilon (PKC-ε) expression after RIPC.

METHODS

In prospective randomized trial, forty eight patients aging from 50 to 75 years old (64 (56 ;69)) were included All patients were scheduled for aortic valve replacement using cardiopulmonary bypass (CPB). The patients were randomized into 4 groups: 1) RIPC applied during propofol anesthesia (RIPC prop, n = 12), 2) RIPC applied during sevoflurane anesthesia (RIPC sev, n = 12), 3) propofol anesthesia without RIPC (CONTROL prop, n = 12), 4) sevoflurane anesthesia without RIPC (CONTROL sev, n = 12). There was no difference found between the groups as to the baseline patient's data. RIPC protocol consisted of 3 simultaneous ischemic episodes of both lower limbs (5 minutes) with 5-min reperfusion intervals. PKC-ε expression in right atrial myocardium was assessed using Western blotting. Troponin I (cTnI) was estimated before anesthesia induction, after 30 min, 6, 12, 24, 48 hours after CPB completion. Also we calculated area under curve of cTnI (cTnI AUC). According to nonparametric distribution, data were assessed by the Mann-Whitney U-test and Newman-Keuls methodfor multigroup comparison. p < 0.05 was considered signifcant. The data are presented as median (25th; 75th percentile).

RESULTS

Cardioprotective effects of RIPC were observed only after sevoflurane anesthesia: cTnI AUC was 134,8 (122,3; 232.4) ng/ml/48 h in CONTROL sev group and only 74.3 (64.7; 85.0) ng/ml/48 h in RIPC sev group (p < 0.05). RIPC applied during propofol anesthesia was not associated with cTnIAUC decrease: 93.8 (74.1; 246.8) ng/ml/48 h in CONTROL prop group and 122.5 (74.1; 185.0) ng/ml/48 h in RIPC prop group (p = 0.37). RIPC applied during sevoflurane anesthesia significantly increased PKC-ε expression: 1221 (921; 1438) U in CONTROL sev group vs 1882 (1564; 2131) U in RIPC sev group 6 (p < 0.05). RIPC implication during propofol anesthesia was not associated with any significant difference in PKC-ε expression in comparison with control group: 620 (436; 782) U in CONTROL prop group versus 788 (574;1063) U in RIPC prop group. In control groups, PKC-ε expression was significantly higher in sevoflurane anesthesia in comparison with propofol anesthesia.

CONCLUSION

RIPC was only effective when it was applied during sevofiurane anesthesia. This was confirmed by PKC-ε expression increase and lower value of cTnI. There were no evidence of preconditioning and cardioprotection when MPG was initiated during propofol anesthesia.

Functional properties of bone marrow derived multipotent mesenchymal stromal cells are altered in heart failure patients, and could be corrected by adjustment of expansion strategies

BACKGROUND

Bone marrow multipotent mesenchymal stromal cells (BM-MMSC) considered as a prospective substrate for cell therapy applications, however adult stem cells could be affected by donor-specific factors: age, gender, medical history. Our aim was to investigate how HF affects the functional properties of BM-MMSC.

MATERIALS AND METHODS

BM-MMSC from 10 healthy donors (HD), and 16 donors with chronic HF were evaluated for proliferative activity, ability to differentiate, replicative senescence, expression of genes that affect regeneration and fibrosis. The effect of culturing conditions on efficiency of BM-MMSC expansion was determined.

RESULTS

HF-derived BM-MMSC demonstrated early decrease of proliferative activity and upregulation of genes that control both, regeneration and fibrosis: Tgf-β pathway, synthesis of ECM, remodeling enzymes, adhesion molecules. We assume that these effects were related to increase of frequency of myofibroblast-like CD146+/SMAα+ CFU-F in HF samples; (ii) low seeding density and hypoxia resulted in predominant purification and expansion of CD146+/SMAα- CFU-Fs. (iii) the activity of NPs system was downregulated in HF BM-MMSC;

CONCLUSIONS

downregulation of NP signaling in combination with upregulation of Tgf-β pathway in BM-MMSC would result in pro-fibrotic phenotype and make these cells non-effective for therapeutic applications; the corrections in culturing strategy resulted in 2(3)-2(7) increase of expansion efficiency.

[THE EFFECT OF PLAKOPHILIN-2 GENE MUTATIONS ON ACTIVITY OF THE CANONICAL Wnt SIGNALING PATHWAY]

Plakophilin-2 is a desmosomal protein encoded by PKP2 gene. Desmosomal proteins are usually considered as structural proteins with the main function of maintaining intercellular interactions. Genetic studies revealed that mutations in desmosomal genes could lead to arrhythmogenic right ventricular cardiomyopathy, heart disease characterized by substitution of cardiomyocytes by adipose and fibrotic tissue predominantly in right ventricle. Wnt signaling pathway is one of the signal transduction pathways which could be involved in the formation of the pathology. The purpose of this study was to investigate Wnt activity changes caused by PKP2 mutations during adipogenic and cardiomyogenic differentiation. We used multipotent mesenchymal stromal cells and iPS cells generated from patient carrying PKP2 gene mutation. We show that Wnt activity is lower in the cells with mutant PKP2. This data indicate a possible signaling role of plakophilin-2 by regulating Wnt activity.

[Possibilities of cryopreservation of ovarian tissue for fertility preservation in cancer patients]

One of the effective methods of fertility preservation is an autologous transplantation of cryopreserved ovarian tissue. Currently, according to the world literature, after orthotopic autotransplantation of ovarian tissue 37 healthy children were born. In 2014 at the North-West Federal Medical Research Center it was established Cryobank of ovarian tissue, which is now kept 50 samples of ovarian tissue of man. Cryoconservation is performed by standard slow freezing. Autotransplantation of cryopreserved ovarian tissue has unique advantages over other methods of fertility preservation. This method does not lead to the postponement of anticancer therapy, safe for hormone-dependent cancer and can be performed regardless of the day of menstrual cycle and it is the only option for fertility preservation in prepubertal girls. The use of this method in clinical practice leads to restoration of endocrine function of the ovaries as well as of fertility in the future.

[Nuclear lamins regulate osteogenic differentiation of mesenchymal stem cells]

Nuclear lamins are the major proteins of nuclear envelope and provide the strength of nuclear membrane as well as the interaction of extra-nuclear structures with components of cell nucleus. Recently, it became clear that lamins not only play a structural role in the cell, but could also regulate cell fate, for example lamins could influence cell differentiation via interaction with components of the Notch signaling pathway. Human mutations in LMNA, encoding lamin A/C lead to diseases commonly referred to as laminopathies. Different mutations cause tissue specific phenotypes that affect predominantly a tissue of mesenchymal origin. The nature of this phenomenon, as well as the mechanisms by which lamins regulate cell differentiation remain poorly understood. The aim of this study was to investigate the effect of different mutations of the LMNA on human mesenchymal stem cell (MSC) osteogenic differentiation, and to explore a possible interaction of lamins and Notch signaling pathway. We modified human MSC with mutant LMNA bearing known mutations with tissue specific phenotype associated with different laminopathies. We have shown that mutations associated with different diseases have different effects on the efficiency of MSC osteogenic differentiation and on the expression of specific osteogenic markers SPP1, IBSP and BGLAP. We have also shown that one of the mechanisms involved in the regulation of MSC differentiation may be an interaction of lamins A/C with components of Notch signaling.

[Comparative assessment of different approaches for obtaining terminally differentiated muscle cells]

Relevant cell model is essential to study pathogenesis of muscle disorders. However, in the field of muscle research there is no ultimate cell line considered as a standard for studying muscular and neuromuscular diseases. Standard cell line claimed to be well differentiated in muscle lineage, be morphological and physiological similar to mature muscle cells and be easily genetically modified. Therefore, the goal of our study was to pick up available and fruitful cell model of muscle differentiation, that could be further applied for examination of muscular disorder pathogenesis in vitro. We characterized human mesenchymal stem cells (MSC), mature murine muscle fibers and primary murine satellite cells. It has been shown that MSC have very small capacity to myogenic differentiation; moreover, they were able to differentiate only in presence of C2C12 cells. Lentiviral transduction exhibited rather high toxic effect on primary myofibers, and positively transduced cells were not able to response to electrical stimulation, i. e. were functionally inactive. Satellite cells turned out to be the most fruitful cell model since they were easily transduced via lentiviruses and rapidly formed myotubes in differentiation media. Functional analysis of obtained myotubes has confirmed their ability to react to electrical and chemical stimulations; besides, potassium and calcium channels availability has been also demonstrated via patch-clump technique. Taken together, these results imply that satellite cells are the most promising cell line for further experiments aimed at exploring the molecular pathways of muscle pathologies.

[Functional properties of smooth muscle cells in ascending aortic aneurysm]

Thoracic aortic aneurism (TAA) develops as a result of complex series of events that dynamically alter the structure and composition of the aortic vascular extracellular matrix (ECM). The main elements that alter the composition of aortic wall are smooth muscle cells (SMC). The purpose of the present work was to study alteration of smooth muscle cell functions derived from the patients with TAA and from healthy donors. As it is supposed that TAA associated with bicuspid aortic valve (BAV) and with tricuspid aortic valve (TAV) differ in their pathogenesis, we compared the SMC and tissues samples from BAV-, TAV-patients and healthy donors. We compared TAA patients' derived tissues and SMC to healthy donors' ones in several parameters: SMC growth, migration and apoptotic dynamics; metalloproteinase MMP2 and MMP9 activity (zymography) and elastin, collagen and fibrillin content (Western blot) in both tissue samples and cultured SMC. Proliferation ability of both BAV and TAV SMC was decreased comparing to donors cells; migration ability in scratch tests was increased in TAV-derived SMC comparing to donor cells. BAV-cells migration ability was not changed comparing to donor-SMC. Elastin content was decreased in TAA SMC comparing to donor cells whereas the content of fibrillin and collagen was not altered. At the same time elastin and collagen protein level was significantly higher in tissue samples of TAA patients comparing to donor-derived samples. SMS proliferation and migration ability is differently affected in TAV and BAV-associated TAA that supports the idea of different nature of these two groups of TAA. Also our data show that SMC functional properties are altered in TAA patients and these alterations could play a significant role in the disease pathogenesis.

[Lamin A/C mutations change differentiation potential of mesenchymal stem cells]

Mutations in lamin A/C gene (LMNA) lead to development of severe disorders--laminopathies. Unlike most other types of intermediate filaments, where the pathological effect of mutations is tightly linked to alteration of mechanical and integrative functions, the detailed mechanism of lamin mutations is still unclear and possibly involves the alteration of nuclear signaling and transcriptional processes. Since the mesenchymal lineage tissues such as myocardium, skeletal muscle, adipose and bone tissues are mostly affected in laminopathies, the role of lamin A/C in differentiation process of mesenchymal stem cells has been assumed. The aim of the study was to estimate the effect of LMNA mutations of differentiation of mesenchymal stem cells into adipose lineages. In vitro mitagenesis was performed on wild type LMNA gene incorporated in a lentiviral vector. Several previously described mutations in LMNA were used, each associated with a certain phenotype. Adipose-derived mesenchymal stem cells from healthy donors were transduced with lentiviruses bearing either wild-type or mutant LMNA. Cells were then induced to adipose differentiation. We show that mutant LMNA/C promotes differentiation capacity of mesenchymal stem cells as seen by morphological changes and by expression of specific adipose markers.

[Desmin-related cardiomyopathy]

The observation of 26 years old patient with desminopathy declared itself by hypertrophied cardiomyopathy with its transformation into restrictive phenotype is presented. The features of pathologic course at the patient were a dominance and diversity of cardiac manifestations. Endomyocardiac biopsy allowed suspecting the desminopathy confirmed by genetic analysis. Morphological features of desmin-related cardiomyopathy were irregular desmin conglomerates mainly located under sarcolemma and an indirect histological signs of idiopathic cardiomyopathy as well nuclear polymorphism, perinuclear "nimbus", chaotic located myofibrils.