[[Length polymorphism of minisatellite repeat B2-VNTR of the bradykinin B2 receptor gene in healthy Russians and in patients with coronary heart disease].

Bradykinin B2 receptor is involved in many processes, including the regulation of blood pressure and smooth muscle contraction, vasodilation, inflammation, edema, cell proliferation, pain. It is suggested that this receptor may be one of the factors that have cardioprotective and infarct-limiting effects. It is assumed that certain genetic variants in both coding and non-coding regions ofBDKRB2 gene may influence its expression. In the 3'-untranslated region of BDKRB2 exon 3 the minisatellite repeat B2-VNTR is located. B2-VNTR has previously been shown to affect the BDKRB2 mRNA stability. Therefore, it is important to perform the molecular genetic analysis of this minisatellite in patients with different forms of coronary heart disease in order to reveal possible associations between specific B2-VNTR alleles and certain clinical forms of coronary heart disease. In the present study, a comparative analysis of the allele and genotype frequencies of B2-VNTR was carried out in groups of healthy individuals and patients with two clinical forms of coronary heart disease (angina pectoris and myocardial infarction), ethnically Russian. The results of the B2-VNTR length polymorphism analysis indicate that this tandem repeat may be attributed to a class of low polymorphic and non-hypervariable minisatellite. In all analyzed groups we revealed three B2-VNTR alleles, consisting of 43, 38 and 33 repeat units. Alleles of 43 and 33 repeats were major in all investigated groups. No statistically significant differences were found in the B2-VNTR allele and genotype frequencies between men and women in control group, and also between healthy men and men with angina pectoris and myocardial infarction. Thus, B2-VNTR length polymorphism was not associated with these clinical forms of coronary heart disease in Russian men. However, we do not exclude the possibility of association between the B2-VNTR short alleles (38 and 33 repeats) and cardioprotective effects of bradykinin B2 receptor in women with coronary heart disease. This hypothesis requires further investigation.

[Instability of repetitive units of foreign centromeric satellite DNA in transgenic mice and transfected cells]. / Analiz nestabil'nosti povtoriaiushchikhsia edinits chuzherodnoi tsentromernoi satellitnoi DNK u transgennykh myshei i v transfektnykh kletkakh.

Cytologically detectable instability of centromeric satellite DNA may cause hereditary disorders in human. To study the mechanisms of such instability, two transgenic mouse lines and 11 clones of transfected F9 mouse embryonic teratocarcinoma cells were obtained with the 3.8-kb repetitive unit (Sat) of Bos taurus satellite DNA IV. Intergeneration and somatic instability of exogenous satellite DNA (satDNA) was observed in transgenic mice and transfected cells as a change in nucleotide sequence of an internal Sat region approximately 1000 bp in size. Since Sat was in the hemizygous state in both cases by the experimental protocol, the instability was attributed to intra-allelic processes. Intergeneration instability probably took place in the premeiotic period of gametogenesis or in early embryo development and led to prenatal death of transgenic embryos after at least one generation. No direct or inverse correlation was observed between methylation and instability of Sat. The results testify that submicroscopic changes in highly repetitive noncoding DNA sequences may already affect the genome function in higher eukaryotes.

Bovine satellite DNA induces heterochromatinization of host chromosomal DNA in cells of trassatellite mouse embryonal carcinoma.

Embryonal teratocarcinoma F9 cells were transfected with a fragment (3.8 kb) of bovine satellite DNA IV (Sat), which is not homologous to mouse satellite DNA. FISH analysis revealed various chromosomal integration sites of integrated Sat in different transsatellite clones. After several passages, transsatellite had a tendency to spread along chromosome bearing Sat in one of the studied lines. The integrated transsatellites were enriched with prolonged single-strand DNA regions (SSR) revealed by FISH without previous chromosomal denaturation, and were unmethylated. The observed SSR are presumably supposed to represent intermediates of transsatellite DNA instability via unequal sister chromatid exchanges. DAPI staining demonstrated that the integrated Sat induced the formation of prominent ectopic neoheterochromatin blocks in regions adjacent to integrated Sat. These blocks were located exclusively between integrated Sat and centromeric heterochromatin. Thus, mouse repetitive centromeric DNA (AT-rich, DAPI-positive) "spreads" along the chromosome in response to integration of the bovine satellite GC-rich DNA. The results obtained are discussed in the context of possible position effect variegation mechanisms operating in undifferentiated cells.

[Modeling heterochromatin regions in transgenic mice]. / Modelirovanie geterokhromatinovykh raionov u transgennykh myshei.

Transgenic mice carrying bovine satellite DNA IV were obtained. The size of the transgene integrated into the mouse genome was approximately 390 kb (about 100 transgene copies) as determined by a semiquantitative PCR. Restriction analysis with isoschizomeric restrictases HpaII and MspI, showed that the alien DNA was methylated. In the genome of a transgenic founder male, two integration sites for satellite DNA IV were revealed by in situ hybridization and in situ PCR. These sites are situated on two different chromosomes: in pericentromeric heterochromatin and within a chromosomal arm. In transgenic mice, de novo formation of heterochromatin regions (C-block and the CMA3 disk within the centromeric heterochromatin of another chromosome) was revealed by C-banding and staining with chromomycin A3. This formation is not characteristic of mice, because their chromosomes normally contain no interstitial C-blocks or sequences intensely stained by chromomycin A3.

[The detection of transgenic animals using a polymerase chain reaction in situ]. / Obnaruzhenie transgennykh zhivotnykh pri pomoshchi polimeraznoi tsepnoi reaktsii in situ.

The technique for detecting both foreign and host specific DNA sequences inside nuclei and chromosomes of single cells of transgenic mice with the help of polymerase chain reaction (PCR) in situ is described. The mouse preimplantation and postimplantation embryonic and adult cells were studied. The methodology is described in detail with particular attention to the optimization of composition of reaction mixture, kind of fixation and preliminary denaturation of target DNA. The reaction takes only several hours and needs no sophisticated equipment.