[Spiral cores of synaptonemal complex lateral elements at the diplotene stage in rye include the ASY1 protein].

After completing their functioning, synaptonemal complexes (SCs) degrade during the diplotene stage. In the pollen mother cells of rye Secale cereal L., this occurs through the formation of gaps in lateral elements of the SCs and the shortening of fragments of SCs until their complete disappearance. However, when contrasting SCs with silver nitrate solution at a pH of 3.5-4.5, these gaps appear to be filled with threads associated with SC lateral elements. As the diplotene stage proceeds and gradual degradation of SC fragments continues, these threads turn into submicroscopic spirals. In this study, we found that the threads and spirals associated with degrading synaptonemal complexes are stained by antibodies to the ASY1 protein ofArabidopsis thaliana lateral elements and thus are degradation products of the lateral elements of SCs.

[The peculiarities of the chromosome organization in meiosis].

Meiotic and mitotic chromosomes differ in a number of features. 1. At the early prophase I of meiosis, chromosomes acquire proteinaceous axial elements (AEs) which were absent at mitosis. In addition to somatic cohesins, AEs contain meiosis-specific cohesins REC8, SMC1beta, STAG3. 2. At the middle prophase I, proteinaceous lateral elements (LEs) of synaptonemal complexes (SC) are shaped on a basis of AEs. Proteins of LEs are not conserved, but in Saccharomyces cerevisiae and Arabidopsis thaliana they contain functional domains with conserved secondary structure. Proteins or functional domains similar to SC proteins have been found in green and brown algae, some of lower fungi and in Coelenterata amongs about 679 hundreds of proteins of primitive eukaryotes studied with bioinformatic methods. 3. During the pachytene and diplotene stages of meiosis, chromosomes of spermatocytes and mother pollen cells acquire the structure resembling in miniature the structure of amphibian and avian lamp brush chromosomes. Lateral chromatin loops of 90, 160 and more than 480 Kb in size are observed in human spermatocytes during the diplotene stage. Taken together, these findings support the idea of considerable conservation of the scheme of molecular and ultrastructural organization of meiotic chromosomes in a variety of eukaryotic organisms.

[Damage to synaptonemal complex structure and peculiarities of selection of mouse spermatocytes I at response to drug administration].

Using immunocytochemistry methods, the structure of synaptonemal complexes (SC) of chromosomes in spread nuclei of primary spermatocytes of mice at 1, 10, and 36 days after the 10-day intraperitoneal administration of antibacterial preparations of three pharmacological groups: furacilin, an antiseptic derivative of nitrofuran; cifran, an antibiotic from the group of fluoroquinolones; and sextaphage, a polyvalent piobacteriophage was investigated. The maximal number of disturbances in the structure and behavior of synaptonemal complex was revealed on the first day after the end of preparation administration. On days 10 and 36, the total number of disturbances in SC structure decreased gradually. On the first day after the end of the administration of cifran and sextaphage in 41.8 and 25% of nuclei, respectively, the fragmentation of synaptonemal complexes was revealed and, in males to whom furacilin had been administered, the fragmentation of synaptonemal complexes was identified in 100% of nuclei. Multiple chromosome fragmentation is a meiotic disaster and results in the degeneration of cells without enabling the mechanism ofpachytene arrest. The features of pachytene arrest were revealed in the nuclei of primary spermatocytes with the disturbances of chromosomes pairing. After the administration of sextaphage, circle structures released from the lateral elements of SC and are dyed with antibodies to SCP3 protein.

[Morphological manifestation of a unique DNA segment in human meiotic prophase I].

The commercial sample of human DNA fragment from the choromosome 17 was used as the probe for FISH to study of the mode of its attachment to the lateral elements of synaptonemal complex (SC) in human spermatocytes. It was a 160 kb probe from the band 17p1.2, containing RAI1 gene with D17S620 marker (the probe for deletion causing Smith-Magenis syndrome). The probe made lateral chromatin protrusions, contacting with SC stained with anty-SYCP3. Different morphological configuration of lateral chromatin protrusions where observed. They depended on substages of meiotic prophase I. At zygotene, FISH probe form two sticks, c. a. 6 micro long, which was perpendicular to SC longitudinal axe, one stick at each SC side. At early pachytene, each stick transforms into a globule, one globule at each SC side again. At late pachytene each globule transformed into two crumbly globules containing short threads and clumps. At diplotene, globules finally transformed into thin DNA (chromatin) loops up to 10 micro long from the base to top with periodical thickenings (beads) along their length. As the result of this dynamics of transformation, two chromatin loops with beads were found on each side of SC of the chromosome 17. These loops most probably were the loops of sister chromatides, the full set of chromatide loops at the particular SC (bivalent) site being four in number, i. e. representing of two pair of chromatides. This study is the first one in which lateral chromatin loops in human mail meiotic prophase I are visualized as true open loop instead of that usually postulated "loops" after observation of condensed road-like or brush-like chromatin protrusion attached to the lateral elements of synaptonemal complexes. Open configuration of the loops, presumably, depends on activation of transcription during late pachytene-early diplotene. They resemble lateral loops of mini lampbrush chromosomes.

A comparative analysis of the mole vole sibling species Ellobius tancrei and E. talpinus (Cricetidae, Rodentia) through chromosome painting and examination of synaptonemal complex structures in hybrids.

A comparative genomic analysis was carried out in the mole vole sibling species Ellobius tancrei and E. talpinus. Performing fluorescent in situ hybridisation (Zoo-FISH) using chromosome paints from the field vole Microtus agrestis showed no differences in the allocation of syntenic groups in the karyotypes of these sibling species. The only difference between their karyotypes was the position of the centromere in one pair of chromosomes, which is assumed to be the result of an inversion. To verify this hypothesis, we analysed chromosome synapsis in prophase I of meiosis. We utilised a synaptonemal complex (SC) surface-spreading technique to visualise the process of chromosome synapsis in the spermatocytes and oocytes of first-generation hybrids and back-crosses of these sibling species. In prophase I of meiosis, immunocytochemical and electron microscopy analyses revealed that all bivalents had been fully adjusted. Even in the case of a submetacentric-acrocentric bivalent with different centromere locations, synapsis of SC lateral elements was fulfilled along the entire length of the chromosomes and the formation of an inversion loop was not observed. We hypothesise that a possible mechanism leading to the change in centromere position is the repositioning and/or generation of a neocentromere. Despite the great similarity in the karyotypes of these sibling species, they exhibited significant genomic diversification, which manifested as hybrid sterility and parous female death.

[DNA repeated sequences may be involved in the synaptonemal complexes formation].

Synatonemal complexes (SCs) are the intranuclear structures which facilitate reversible lateral synapsis of the homologous chromosomes in the course of meiosis. It is still unclear which DNA nucleotide sequences are responsible for the chromatin attachment to the SC lateral elements. Considering the features of the dispersed repeated sequences (RS) it is worth to assume their participation in the structure functional organization of the meiotic chromosome. Using numerical analysis we have investigated the relationship between RS and the distribution of events of the meiotic recombination in mouse chromosome 1. Using in situ hybridization on spread mouse spermatocytes, we have demonstrated the arrangement of different types of RS relative to SCs. Hybridization signals of B1(Alu), B2, and minisatellite probes were localizating predominantly in the SCs regions. Our results allow us to suggest the model of the meiotic chromosome organization with the RS as the sequences, participating in the attachment of chromatin loops and SCs.

[How do chromosomes attach to synaptonemal complexes?].

Fluorochrome-labeled oligonucleotides (n = 44) corresponding to mouse genome repetitive sequences were hybridized in situ with pachytene nuclei of mouse spermatocytes. Signals of the repetitive sequences MaLR, MER, and (GT)22 were found to be dispersed through chromatin, and signals of BI 1 repeats and minisatellites were mostly attached to synaptonemal complexes immunostained with anti-SYCP3 antibodies. These results suggest that B 1 repeats and minisatellites are candidates for sequences anchoring chromatin to synaptonemal complexes.