Time-appropriate, stage-by-stage development of tissues and organs is achieved by coordinated operation of epigenetic mechanisms of gene expression regulation (DNA methylation, histone modifications, effects mediated by non-coding RNAs). It has been established that disruption of one single component of epigenetic regulation leads to changes in the functioning of others. Over the past 10 years there have been discovered more than 60 epigenomic signatures representing unique genome methylation patterns specific for hereditary disorders associated with disruption of the epigenetic machinery. The episignature can partially determine phenotypic traits and potentially serve as a reliable diagnostic tool due to its high specificity. This review aims to shed light on one of the central links of epigenetic regulation, histone methylation, as well as hereditary diseases that develop when it is disrupted, and the episignatures specific for these syndromes.

Background. Given the increasing prevalence of postpartum hemorrhage, a lot of work has been done today on the pathogenesis of uterine atony. Nevertheless, the study and search for candidate genes involved in the development of uterine atony remain relevant.
Objective: to evaluate association of the genetic polymorphism NOS1 rs41279104 with myometrial dysfunction and the risk of postpartum uterine atony in Uzbek women.
Methods. We examined 101 women who developed postpartum atonic bleeding of varying severity. Common laboratory and instrumental examinations were performed on all women. Genomic DNA was used for the detection of the NOS1 rs41279104.
Results. Allele A is the risk factor for postpartum uterine atony more than 1.7 times (χ² = 4.2, OR = 1.7, p = 0.05) in parturient women with a gestational age of 37-42 weeks. Conclusion. The results of our research indicate that the NOS1 rs41279104 has an association with postpartum atonic bleeding. In women with 37-42 weeks of gestation, allelic variant A may be a risk factor for PPH.

Aim: to describe the clinical significance of the number of CAG repeats in exon 1 of the HTT gene in patients with Huntington’s disease in the Russian Federation.
Methods. A total of 1290 DNA samples was obtained from previously collected samples of patients. The number of CAG repeats in the HTT gene was evaluated in the «Laboratory for diagnostics of autoimmune diseases» the Federal State Budgetary Educational Institution of Higher Education Academician I.P. Pavlov First St. Petersburg State Medical University of the Ministry of Healthcare of Russian Federation. Informed consent was obtained from each patient. To evaluate CAG-repeats number in HTT gene, fragment analysis and triplet repeat primed PCR were used. The «Normal» group included patients with number of CAG repeats ≤26. The «Premutation» group consisted of patients who had at least one allele with the number of triplets from 27 to 35 (intermediate alleles, IA). The «Mutation» group included patients with number of CAG repeats ≥36 . Statistical analysis was performed by using the GraphPad Prism 8 program (GraphPad Software Inc., USA).
Results. A total of 659 samples had no expansion, 44 samples had at least one IA, 587 samples had ≥36 CAG repeats. In the «Mutation» group the association between the age of examination in the laboratory and the size of the expansion allele was investigated and an inverse correlation between these parameters was revealed (p< 0.0001 r= 0.4930). In 15 of 32 familial cases, the expansion allele was transmitted to the child. Transmission of the mutation from the father occurred in 86.67% of cases, from the mother − in 13.33% of cases.
Conclusions. Inverse correlation was revealed between age of the patient’s first visit to laboratory and the number of CAG-repeats. The revealed prevalence of intermediate alleles in the population accentuates the importance of studying the characteristics of the clinical course of Huntington’s disease in their carriers.

Introduction. Facial clefts are one of the most common and severe congenital malformations. Due to gross anatomical disorders, children with cleft lip and palate may experience serious disturbances in nutrition, speech, hearing, as well as mental and social disorders. To study the causes of these defects, as well as to develop preventive measures, it is necessary to know their epidemiological characteristics, which is the purpose of this study.
Methods. The analysis used data on cleft lip and palate from 24 regions of the Russian Federation that monitor congenital malformations. All cases of facial clefts among newborns from 2020-2022 were included. The total number of cases of malformations was 473 cases of cleft palate (CP) and 980 cases of cleft lip/palate (CLP). The total number of births was 1,136,551. Frequencies were calculated per 10,000 births.
Results. According to the results of the study, the total estimate of frequencies for all regions for three years was for CP – 4.16, for CLP – 8.62 per 10,000 births. Interregional differences in estimates of the frequencies of CP and CLP were revealed. For the period 2020- 2022 in the regions of the Russian Federation, the frequency of CP ranges from 1.70 to 11.09, the frequency of CLP – from 3.08 to 15.97. The sex ratio for CP was 0.85M:1F, for CLP – 1.69M:1F, i.e. for CP girls are more often affected; for CLP boys are more often affected. Most cases of facial clefts are isolated forms. No changes in the frequency of defects are observed over time.
Conclusion. Facial clefts are characterized by a high frequency with geographic and interregional differences, knowledge of which is important for the scientifically based development of preventive measures, as well as justification of the scope of diagnostic and therapeutic care for patients with these defects.

Background. Coronavirus disease 2019 (COVID-19) is a highly contagious disease, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Several risk factors of COVID-19 susceptibility and severity are associated with oxidative stress.
Aim: to investigate the association of single nucleotide polymorphisms (SNPs) of glutathione S-transferase pi-1 (GSTP1) and glutathione peroxidase 4 (GPX4) genes with the severity of COVID-19.
Methods. Study subjects were divided into two groups based on the severity of their symptoms. Allele-specific real time polymerase chain reaction (RT-PCR) was used for genotyping, and multifactor dimensionality reduction (MDR) analysis was performed to investigate the SNP-SNP interaction models.
Results. The results showed a significant association of GPX4 rs713041 with the severity of COVID-19 (p=0.035). Most of GPX4 718TT carriers had a severe course of COVID-19 (OR=3.50; 95% CI [1.18-10.35]). The resulted three-locus SNP-SNP interaction model was statistically significant (p=0.0084, OR = 2.42; 95% CI [1.24 - 4.73]). Linkage disequilibrium analysis of GSTP1 SNPs rs1695 and rs1138272 showed a high possibility of linkage disequilibrium between the two sites (D’ = 0.949).
Conclusions: To our knowledge, this is the first study to investigate the association of GSTP1 rs1695, GSTP1 rs1138272, and GPX4 rs713041 and SNP-SNP interaction with the severity of COVID-19 symptoms. The obtained results may serve as a novel potential factor of COVID-19 prognosis.

Atrial fibrillation (AF) is the most common cardiac arrhythmia. AF can occur both in isolation and in a number of diseases. Often, AF and arterial hypertension (AH) coexist, since these nosologies have common risk factors and conditions that increase the incidence of both. According to large clinical studies, the leading role of hypertension in the development of AF has been established. The range of candidate genes involved in the implementation of hypertension is quite wide and includes groups of genes that control various metabolic and homeostatic systems, the disturbances of which are involved in the pathogenesis of cardiovascular diseases. In particular, these are the genes of the renin-angiotensin system. It is relevant to study the genes of the renin-angiotensin-aldosterone system (RAAS) in AF, since the associative effect of angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists (ARA II) in the prevention of AF has been proven. RAAS blockers can not only reduce the risk of developing new-onset AF in patients, both with and without arterial hypertension, but also prevent relapse of AF. In this study, 68 patients with non-valvular AF were examined. All patients were divided into two groups: patients with atrial fibrillation with hypertension and patients with atrial fibrillation without hypertension. Genetic research methods included DNA isolation and determination of genetic polymorphisms of the RAAS using the polymerase chain reaction method in real time using a thermal cycler and reagents from the DNA-Technology company (Russia). A comparative analysis of polymorphic variants of the RAAS genes: rs4961 ADD1, rs699 AGT, rs4762 AGT, rs5186 AGTR1, rs1403543 AGTR2, rs1799998 CYP11B2, rs5443 GNB3 in patients with AF in the study groups did not reveal statistically significant differences.