Multiple epimutations in imprinted genes change the expression level of maternal and paternal genes. This leads to disturbance in embryonic and postembryonic human development. The phenomenon of multiple epimutations indicates the possibility of the existence of special mechanisms controlling the epigenetic status of multiple imprinted genome loci. Therefore, the study of these mechanisms is of interest. The following review is devoted to the new class of genes ( NLRP 2, NLRP 5, NLRP7 , KHDC3L , ZFP57 and PADI6 ), mutations in which are accompanied by multiple epimutations in imprinted loci both during embryonic development and hereditary syndromes.

Chromosomal heteromorphism, in the form of increasing of the short arms of acrocentric chromosomes, is quite common in cytogenetic diagnosis. In some cases, these may be increased due to unbalanced translocation involving heterochromatin, most often Yq. This phenomenon can be explained by the association of these chromosomes with the XY complex in early pachytene. Carriers of unbalanced Y-autosomal translocations usually have a normal phenotype and fertility. However, in some reports, it has been shown that carriers t (Y; 15) (q12; p11) may have reproductive problems or children with abnormal phenotype. When using molecular cytogenetic methods, a detailed characterization of heteromorphism of acrocentric chromosomes was given in four cases. FISH analysis allowed us to determine the unbalanced translocation Y;15 in three cases, and Y;14 - in one. Information on the variants of heterochromatin chromosome regions allows to provide appropriate medical-genetic counseling to the family.

Background. Gastric cancer (GC) is one of the most common oncological diseases, with the fifth place in the world in terms of morbidity and the third on mortality among all malignant neoplasms. Until recently, the classification of GC was based mainly on histological criteria. Objective. To characterize the spectra of gene mutations in various histological types of gastric tumors, and to search for novel mutations in the Russian patients. Material and methods. To analyze 52 GC samples and the samples of morphologically unaltered tissues from the same patients, we have used NGS with two panels, an Ion AmpliSeq Cancer Hotspot Panel v2, widely used for the analysis of «hot spots» in cancer related genes, and an in-house panel developed for sequencing the genes involved in gastric carcinogenesis. Results. In total, with two panels, we have identified 20 genetic variants with exceptionally low general population frequencies (no higher than 0.00004 according to the gnomAD database), and 19 genetic variants that have never been reported previously. We report a statistically significant enrichment of a cohort of intestinal tumors with somatic missense mutations in the TP53 gene compared to diffuse tumors. The germline status was determined for 4 novel genetic variants, in the RB1 , SMO and CDH1 genes.

Recurrent pregnancy loss (RPL) is a multifactorial pathology with significant proportion of idiopathic cases. Comparative analysis of the chromosomal abnormalities rates in abortions in primary vs. secondary RPL can shed light on the genetic heterogeneity of these groups. The aim of this study was to establish the contribution of the embryonic chromosomal abnormalities in the pathogenesis of primary and secondary RPL. Of the 563 abortuses karyotyped, 335 were from women with primary and 228 with secondary RPL. The frequency of chromosomal aberrations was 43.9% and 52.6% in the groups with primary and secondary RPL, respectively (p = 0.041). Double trisomy were revealed in 5.2% of abortuses and the most of cases were found in secondary RPL group (p = 0.0002). There were no significant differences in the frequency of involvement of individual chromosomes in aneuploidy between groups with primary and secondary RPL. The frequency of aneuploid pregnancy significantly higher in secondary RPL, and this difference is due to the «lack» of abortuses with abnormal karyotypes in older women with primary RPL.

Background. In cases of neurofibromatosis type 1 and type 2, pathogenic mutations are distributed evenly along the coding regions of the NF1 and NF2 genes. Herewith, in more than 50% of cases, the disease is the result of a de novo mutation. Therefore, the search for a causative mutation is particularly time-consuming and the catalogs of pathogenic and non-pathogenic genetic variants are an indispensable assistance handbook for geneticists in their work. Objective. To determine the spectrum of genetic alterations in Russian neurofibromatosis patients and to characterize novel pathogenic mutations and rare non-pathogenic genetic variants in the NF1 and NF2 genes. Material and methods. The study was carried out on the peripheral blood lymphocyte and/or tumor tissue DNA samples from 617 patients. NGS was performed on the Ion Torrent PGM and Ion Torrent S5 sequencing machines using NF1 and NF2 AmpliSeq gene panel. Gene panel encompasses exons of the NF1 and NF2 genes, adjacent intron segments (20-70 bp), 3’UTRs, and 5’UTRs. Sanger sequencing was used to verify pathogenic genetic variants and the MLPA method was used to search for NF1 and NF2 gross deletions. Result. Complex molecular genetic diagnostics of the NF1 and NF2 alterations was accomplished for 617 patients. The NF1 and NF2 mutations were detected in 303 and 19 cases, respectively. Conclusion. We have characterized 69 novel pathogenic mutations, 68 in the NF1 gene, and 1 in the NF2 gene, as well as 68 rare non-pathogenic genetic variants. Most non-pathogenic genetic variants are represented by synonymous SNPs and nucleotide substitutions in untranslated regions, which are particularly difficult to interpret during medical-genetic counseling.

Copy number variations (CNVs) are one of the genetic causes of congenital heart disease. Existing views on CNVs in the etiology of the congenital heart disease (CHD) does not fully explain the formation of a specific heart defect. The obtained knowledge will be directed to the development of new approaches for improving the diagnosis of genomic imbalance in patients with CHD. This study aim at investigating the presence of pathogenetically significant CNVs in the nosological structure of CHD. Materials and methods. 31 children with CHD, combined with extracardiac pathology were included in the study. Samples of DNA were analyzed using high-density DNA microarrays SurePrint G3 Human Genome CGH + SNP Microarray Kit, 8 х 60K (Agilent Technologies, USA). ICD-11 was used to describe the nosological structure. Results. Pathogenic and likely pathogenic CNVs were detected in 32% (10/31) of patients with CHD and extracardiac pathology. CNVs were identified in the categories of CHD: anomaly of a ventricle or the ventricular septum; anomaly of atrial septum; anomaly of a ventriculo-arterial valve or adjacent regions; anomaly of the mediastinal vein. Conclusions. The detection of pathogenic or likely pathogenic CNVs is more often associated with conotruncal, septal or complex heart defects.

Introduction: The process of the X chromosome inactivation in females is random, while preferential inactivation of one of the parental homologues may indicate the presence of mutations in it and lead to the development of hereditary pathology in the offspring. Aim: Identification of X-linked loci the epigenetic modifications of which can compensate for the development of a pathological phenotype. Materials and methods: 111 women with miscarriage and 47 women with no history of spontaneous abortions were examined. Using methyl-sensitive PCR and array comparative genomic hybridization, X-linked copy number variations (CNV) were analyzed in blood lymphocytes of women with an extreme skewing of X chromosome inactivation. Results: The incidence of extreme skewing of X chromosome inactivation in women with miscarriage and in the control group was 9 and 4%, respectively (p>0.05). In 8 women with an extreme skewing of inactivation and miscarriage X-linked CNVs at Xp11.23, Xp22.33, Xq24 and Xq28 were identified and their gene content was analyzed. It was shown that most of the identified CNVs were in one way or another associated with the development of X-linked forms of mental retardation. Conclusions: The epigenetic modification of X-linked CNVs compensates for their phenotypic manifestation in female carriers. At the same time, the absence of compensatory epigenetic/

Relevance. Sudden cardiac death (SCD) risk assessment in patients with hypertrophic cardiomyopathy (HCM) is based solely on clinical and instrumental parameters. Still, there is an issue of inadequate prognosis of SCD risk requiring further investigations of individual risk factors. Objective of the present study was to assess genotype-phenotype associations in cohort of subjects with HCM who died from SCD, or had high risk of SCD with mutations in sarcomere protein genes. Materials and methods. The study comprised 29 individuals with HCM: 10 subjects died from SCD, 4 were successfully resuscitated and ICD implanted, and 15 individuals had a history complicated by SCD in first-line relatives. All patients were analyzed using clinical and instrumental data, and the search of mutations in protein-encoding sequences of sarcomere protein genes (using high throughput sequencing in 27 subjects, and Sanger automated sequencing in 2 subjects) was made. Results. Thirteen out of 18 (72,2%) HCM individuals with high risk of SCD by HCM-Risk SCD showed mutations and substitutions of unknown significance previously reported in literature including Val186Leu, Arg403Trp, Lys450Glu, Val606Met, Arg663Cys & Glu924Lys in MYH7; Asp610Asn combined with Pro1066Arg, Trp1214Arg, Gln1233*, Glu1265Val combined with Cys1266Arg in MYBPC3 and two new Tyr1043* & Arg1138fs in MYBPC3 gene. Six out of 11 subjects (54,5%) with low-to moderate SCD risk by HCM-Risk SCD showed mutations and substitutions of unknown significance previously reported including Arg1712Trp in MYH7 combined with the mutation of Arg502Gln in MYBPC3; Ser217Gly, Arg346His, Glu894Asp, in MYBPC3; Leu238Pro in ACTC1, and previously unknown substitution Trp1007fs in MYBPC3 gene. Conclusion. It seems feasible to include genetic data in SCD risk assessment, particularly for patients with low-to-moderate risk established using ESC-2014 HCM Risk-SCD score.

The human chromosome region 14q32 contains a number of imprinted genes that are expressed either from the paternal or from the maternal alleles. Genetic alterations of these genes lead to distinct phenotypes, known as maternal uniparental disomy 14 (Temple syndrome ОMIM #616222) or paternal uniparental disomy 14 (Kagami-Ogata syndrome ОMIM# 608149). Kagami-Ogata syndrome characterizes by a small bell-shaped thorax with a coat-hanger configuration of the ribs, abdominal wall defects, joint contractures and polyhydramnios during the pregnancy. In both syndromes, three types of molecular alterations have been reported: uniparental disomy 14, deletions and epimutations. Most described deletions in previous articles included one or both of the differentially methylated regions: DLK1 and MEG3. In contrast to uniparental disomy and epimutations, deletions affecting regulatory elements in 14q32.2 are associated with a high-recurrence risk. Patients and Methods. We present clinical case Kagami-Ogata syndrome is caused deletion 14q32.2. We performed microsatellite analysis of trio and microarray analysis of the mother. Results. Microsatellite analysis of trio and microarray analysis of mother have allowed to define the extent of deletions (378 kb) affecting the regions 14q32.2-14q32.1, including genes (MEG3, RTL1, MEG8) that are expressed from the maternal allele and do not affect the IG-DMR. We performed a comparative analysis of patient’s phenotypes, described earlier, with different deletions involving IG-DMR and MEG3-DMR. Conclusion. Analysis of deletions origin, as well as its included genes, in the diagnosis of diseases allows making an accurate diagnosis and using the methods of prenatal and/or preimplantation diagnostics in patients with a high risk of hereditary pathology.

The article presents a family with cases of dilated cardiomyopathy (DCM) registered for two generations. The study aim was to determine the genetic cause of the disease development. Materials: DNA samples obtained from the buccal epithelium of the proband and family members. Methods: clinical and laboratory methods for diagnosis establishing and verifying, NGS and direct sequencing for the definition of the pathogenic variant leading to the cardiomyopathy. Results: a heterozygous mutation c.1901G> A was identified in the gene of the alternative splicing factor RBM20 (10q25.2), leading to the replacement of the highly conserved arginine residue by glutamine in the RS domain of the protein - p.R634Q. Its carriage co-segregated with the DCM phenotype in family members. Mutations in this gene lead to the alternative splicing disruption and the formation of atypical mRNA variants. Published articles about the splicing regulation of genes expressed in the cardiac muscle by RBM20 are reviewed. Conclusion: variant c.1901G>A in the RBM20 gene should be considered as pathogenic. The molecular genetic analysis specified the diagnosis of the proband and her son - DCM 1DD.

We report a rare germline missense variant in the RET protooncogene found in a 55-year-old woman with medullary thyroid carcinoma (MTC). Calcitonin before surgery was 400 pg/ml (N = 2-6 pg/ml). Postoperative calcitonin was 0.45 pg/ml. Pheochromocytoma and hyperparathyroidism were excluded. Sanger sequencing of eight exons (5, 8, 10, 11, 13-16) (peripheral blood-derived genomic DNA) of the RET gene identified the heterozygous germline missense variant p.Arg886Gln (exon 15). But its clinical significance has not yet been determined. The proband`s parents were not available. In the control group we only found wild-type alleles.