[Twin gestation with regressive partial hydatidiform mole and coexisting live fetus]. / Nerazvivayushchiisya chastichnyi puzyrnyi zanos v slitnoi dikhorial'noi platsente s normal'nym razvitiem vtorogo bliznetsa.

The case of dichorionic twin pregnancy is described, with a fused placenta, one part of which is represented by a tissue of partial hydatidiform mole (PHM) with signs of regression, the second part is a placenta of a common structure with a normal development of the second twin. The delivery took place at the term of 38 weeks with a live healthy girl weighing 3250 g. A single placental disc consisted of two fused placentas with a clear boundary between them. The placenta of a live-born girl was mature, with focal chorangiosis, the second part of the disc was represented by the PHM tissue with avascular giant bizarre villi, some of them with central cisterns, with stromal fibrosis, low proliferative activity of the villous trophoblast and a significant narrowing of the intervillous space. A genetic study was carried out on the material of paraffin blocks from two parts of the placental disc containing the tissue of the villous chorion, and the blood of the parents. Comparative analysis of DNA isolated from the paraffin block of PHM with the DNA of the parents revealed the presence of diandric dispermic triploidy. No chromosomal pathology was found in the placenta of a living girl. For hydatidiform mole in the case of multiple pregnancy, an increase in the volume of the affected placenta is characteristic compared to the normal placenta of the twin. In our observation, the presence in the placenta with PHM signs characteristic of placentas with antenatal fetal death, stromal fibrosis of the villi and low proliferative activity of the trophoblast suggests a regression of PHM.

[Epigenetic Regulation Disturbances on Gene Expression in Imprinting Diseases].

Epigenetic regulation is hereditary and non-hereditary changes in the expression of a particular gene without any corresponding structural changes in its nucleotide sequence. Genomic imprinting is an epigenetic mechanism for regulating the expression of homologous genes depending on parental origin, i.e., they are expressed monoallelically in the mammalian diploid cell. Being genetically imprinted, only the maternal or only the paternal genome is unable to ensure normal embryonic development. The most studied epigenetic modification, which plays one of the main roles in the maintenance of imprinting processes, is the specific methylation of cytosine in CpG-dinucleotides. All known imprinted genes contain differential DNA methylation regions on homologous parent chromosomes, which are necessary for their monoallelic expression. However, it is now known that not only DNA methylation, but chromatin remodeling, histone modifications, and non-coding RNAs also ensure the proper functioning of imprinted genes in the human body. Structural and functional disturbances of epigenetic mechanisms lead to imprinting diseases.

[Clinical and genetic aspects of ABCA4-associated inherited retinal diseases]. / Klinicheskie i geneticheskie aspekty ABCA4-assotsiirovannykh nasledstvennykh zabolevanii setchatki.

The clinical and genetic characteristics of ABCA4-associated inherited retinal diseases have been studied for more than 2 decades, since the identification of the ABCA4 protein in 1978 and the ABCA4 gene in 1997. ABCA4 mutations were initially associated with autosomal recessive Stargardt disease (STGD1). It has now been established that mutations in this gene can cause other inherited retinal diseases, such as cone-rod dystrophy and retinitis pigmentosa. In addition, the phenotypes of ABCA4-associated diseases can vary greatly from the classic presentation of Stargardt disease, from loss of central vision in adolescence to disease with early onset and rapid progression or late onset and milder course. ABCA4-associated diseases are inherited in autosomal recessive manner, i.e. the disease develops only if both alleles of the gene are damaged, one inherited from the father and the other inherited from the mother. As with many other recessive hereditary diseases, which are characterized by a variety of clinical manifestations, the diversity of the phenotypes of ABCA4-associated retinal diseases is explained by combinations of sequence variants in the ABCA4 gene inherited by patients from their parents. Despite the fact that in this respect inherited retinal diseases associated with mutations in the ABCA4 gene do not fundamentally differ from other autosomal recessive traits, due to the structure of the gene and the protein encoded by it, there are a number of features thatshould be taken into account when performing molecular diagnostics, predicting the possibility of manifestation and the course of the disease, and planning the approaches to treatment.

[New possibilities in the treatment of Stargardt disease]. / Novye vozmozhnosti terapii bolezni Shtargardta.

Stargardt disease is a hereditary retinal dystrophy associated with mutations in the ABCA4 gene. Currently, no etiopathogenetic drugs nor treatment methods for Stargardt disease have completely passed clinical trials. The review summarizes experimental and clinical studies of drugs aimed at reducing the accumulation of vitamin A dimers, lipofuscin, complement inhibition and RPE regeneration by stem cell transplantation, as well as gene therapy studies with intravitreal vector injection of the ABCA4 functional gene.

[Phenotype-genotype correlations in patients with inherited retinal diseases with p.G1961E mutation in the ABCA4 gene]. / Kliniko-geneticheskie korreliatsii u patsientov s nasledstvennymi zabolevaniiami setchatki pri mutatsii p.G1961E v gene AVSA4.

PURPOSE: To evaluate phenotype-genotype correlations in patients with inherited retinal diseases (IRD) with mutation p.G1961E in the ABCA4 gene. MATERIAL AND METHODS: The study included 20 patients with p.G1961E mutation in the heterozygous state in the ABCA4 gene who underwent complete ophthalmic examination, as well as high-performance parallel sequencing of the coding sequences and adjacent areas of the introns of the ABCA4, ELOVL4, PROM1, CNGB3 genes. RESULTS: The p.G1961E mutation was detected in heterozygous state with missense mutations, splice site mutations, a frameshift duplication, and a nonsense mutation in 18 patients, a second mutation was not detected in 2 patients. The duration of the disease in 4 patients was 2-5 years, which made it impossible to assess the morphofunctional changes in dynamics. In 13 of the 16 patients with IRD duration of 29±14 years and p.G1961E mutation in the ABCA4 gene the course of the disease was relatively mild: visual acuity of 0.15±0.07, loss of visual acuity averaging 0.037±0.019 per year, absolute/relative scotoma within 5-20°, and 3.52±1.21 mm loss of ellipsoid photoreceptor zone in the macular area according to OCT. In 3 patients, including one without a second mutation in the ABCA4 gene, better pronounced changes were revealed. Multifocal electroretinogram was altered in all 20 cases. In 7 of the 8 patients with p.G1961E in the heterozygous state in combination with complex mutation p.[L541P;A1038V], as well as in 2 patients without a second mutation, full-field electroretinography (Ganzfeld; ffERG) had changes (abnormalities) of varying intensity. CONCLUSION: A frequent mutation in the ABCA4 gene - p.G1961E - is associated with a relatively mild course of IRD in 81% of cases, even in the presence of a second, severe mutation. However, in rare cases a more severe phenotype of the IRD in patients with p.G1961E mutation can be observed, which may be associated with other genetic factors. In patients with the p.G1961E mutation in heterozygous state with p.[L541P;A1038V], ffERG changes (abnormalities) were revealed.

[Inherited retinal diseases in patients with ABCA4 gene mutations]. / Nasledstvennye zabolevaniia setchatki pri mutatsiiakh gena ABCA4.

ABCA4 is one of the main genes which mutations are associated with various inherited retinal diseases (IRD) such as Stargardt disease, cone dystrophy, cone-rod dystrophy, and retinitis pigmentosa. Wide prevalence of IRD, high heterogeneity of ABCA4 gene mutations that lead to impaired function of the protein with varying expressiveness make studying of the clinical and genetic characteristics of retinal diseases relevant for further investigations into pathogenesis, prognosis and outcome of the disease. This article reviews the literature on incidence of IRD caused by mutations in the ABCA4 gene and characteristics of the clinical progression of retinal diseases associated with various types of mutations, and presents analysis of clinical and genetic correlations in terms of the effect the mutation has on the structure or function of the protein.

[Clinical polymorphism of splice site mutations in the ABCA4 gene]. / Polimorfizm klinicheskikh proiavlenii pri mutatsiiakh saita splaisinga v gene AVSA4.

ABCA4 is one of the main genes whose mutations are associated with various inherited retinal diseases (IRD) such as Stargardt disease, cone dystrophy, cone-rod dystrophy, and retinitis pigmentosa. The severity of retinal dystrophy phenotype may be related to the degree of mutation pathogenicity, which depends on the localization in various regulatory regions of the gene and the effect on the amino acid composition of the protein molecule. The article describes two clinical cases of patients with splice site mutations in the compound heterozygous state with missense mutations in the ABCA4 gene with various phenotypic manifestations, which demonstrate the importance of molecular genetic analysis in patients with IRD. Such analysis allows determination and accumulation of data on phenotype-genotype correlations that can help predict the disease course.

Detection of Rare Mutations by Routine Analysis of KRAS, NRAS, and BRAF Oncogenes.

Molecular genetic analysis of KRAS, NRAS, and BRAF genes was carried out in order to develop an optimal algorithm for detection of minor mutations. We analyzed 35 melanoma and 33 colorectal cancer specimens. Frequent G12D/V/A/C/S mutations were detected in KRAS. The most frequent BRAF mutation in melanoma was V600E, the percentage of rare mutations is significant for DNA diagnosis (24%). Identification of rare BRAF mutations 1790C→G (L597R), 1798_1799delinsAA (V600K), 1798_1799delinsAG (V600R), and 1799_1800delinsAA (V600E) and NRAS mutation 38G→T (G13V) was possible only by Sanger sequencing. The combination of real-time PCR and sequencing can improve analysis sensitivity and ensure concordance of the tested loci with the international recommendations.

[DNA methylation in the promoter regions of the laminin family genes in normal and breast carcinoma tissues].

Extracellular glycoproteins of the laminin family are essential components of basement membranes involved in a number of biological processes, including tissue differentiation, wound healing, and tumorigenesis. We present the first comprehensive study of promoter methylation status of the genes encoding laminin chains in normal tissues (peripheral blood leucocytes, buccal epithelial cells, autopsy breast tissue samples) and in breast carcinoma samples. Based on the results of this study, we divide laminin genes into three categories. Genes, constitutively methylated in breast tissues include LAMA3A, LAMB2, LAMB3, and LAMC2. Genes prone to abnormal methylation in breast carcinoma include LAMA1, LAMA2, LAMA3B, LAMA4, LAMB1, and LAMC3. Genes that are rarely if ever methylated in breast carcinoma include LAMA5 and LAMC1. The constitutively methylated group includes all of the genes that encode subunits of laminin-5 (the historical name of laminin 332), the promoters of which were previously considered unmethylated in normal tissues and prone to abnormal methylation in breast cancer.

[Reduced representation bisulfite sequencing design for assessing the methylation of human CpG islands in large samples].

The reduced representation bisulfite sequencing (RRBS) method has been developed for the high-throughput analysis of DNA methylation based on the sequencing of genomic libraries treated with sodium bisulfite by next-generation approaches. In contrast to whole-genome sequencing, the RRBS approach elaborates specific endonucleases to prepare libraries in order to produce pools of CpG-rich DNA fragments. The original RRBS technology based on the use of the MspI libraries allows one to increase the relative number of CpG islands in the pools of genomic fragments compared to whole-genome bisulfite sequencing. Nevertheless, this technology is rarely used due to the high cost compared with bisulfite methylation analysis with hybridization microarrays and significant residual amount of data represented by the sequences of genomic repeats that complicates the alignment and is not of particular interest for developing DNA methylation markers, which is often the main goal of biomedical research. We have developed an algorithm for estimating the likelihood that recognition sites of restriction endonucleases will be represented in CpG islands and present a method of reducing the effective size of the RRBS library without a significant loss of the CpG islands based on the use of the XmaI endonuclease for library preparation. In silico analysis demonstrates that the optimum range of the XmaI-RRBS fragment lengths is 110-200 base pairs. The sequencing of this library allows one to assess the methylation status of over 125000 CpG dinucleotides, of which over 90000 belong to CpG islands.

[Mutagen influence with different mechanisms of action on DNA global methylation in human whole-blood lymphocytes in vitro].

Data that support the evidence of mutagens known to cause epigenetic abnormalities that could potentially result in genomic instability and the development of cancer rather than to modifications in the human genome at the gene and chromosomal levels only. The level of global methylation in human lymphocytes in vitro caused by exposure to two mutagens with different mechanisms of action, i.e., dioxidine and methyl methanesulphonate (MMS), was demonstrated in the present study. Global methylation was assessed by methyl-sensitive comet assay. An increase in the level of global methylation to 45.64% was revealed during culturing with dioxidine in a concentration of 0.01 mg/mL (p < 0.001), while the addition of dioxidine in a concentration of 0.1 mg/mL resulted in a decreased level of methylation up to 42.31% (p < 0.001). The addition of M MS in concentrations of 0.0025 and 0.01 mg/mL resulted in minor but significant modifications (p < 0.05) of the global methylation level ranged within natural variations in global methylation. Accordingly, the addition ofdioxidine in the concentration of 0.1 mg/mL might cause genomic instability and might be considered a potential carcinogen.

TNR/11q#1 trinucleotide (GCC)n repeat alleles and predisposition to acute and chronic leukemia.

TNR/11q#1 is a polymorphic trinucleotide (GCC)n repeat located within the minimal region of the 11q deletion in chronic lymphocytic leukemia (CLL). It was recently shown that certain alleles of this repeat are associated with a worse prognosis in CLL patients. To investigate the role of TNR/11q#1 variants as risk-modifying factors in leukemogenesis, we conducted a case-control study on 113 acute lymphotic leukemia (ALL) patients, 82 CLL patients and 146 healthy controls of Russian origin. Comparison of allele and genotype distributions in the control, ALL and CLL groups, performed by Fisher's exact test with two-sized P-value, showed significant decrease in the presence of the GCC(6) allele in the ALL and CLL groups compared to controls. Moreover, 'rare' alleles GCC(7-8) and GCC(13-14) were significantly overrepresented in the ALL group versus controls. We found that CLL risk genotypes were those with both alleles containing more than 6 GCC repeats (P = 0,0212, odds ratio = 1,68 (95% CI, 1,121...2,531)). ALL risk genotypes include three allele combination variants: 1) both alleles containing more than 6 GCC repeats (P = 0,0019, odds ratio = 1,756 (95% CI 1,223...2,502)); 2) one of the alleles containing 7 or 8 repeats (P = 0,0155, odds ratio = 18,22 (95% CI 1,93...136.37)); 3) one of the alleles containing more than 12 repeats (P = 0,0209, Odds ratio = 2,599 (95% CI 1,161...5,815)). Association of certain alleles and genotypes of the TNR/11q#1 repeat with both acute and chronic lymphocytic leukemia suggests the presence of a cancer related gene, involved in a wide spectrum of neoplasia, in the vicinity of this repeat.