S. Ya. Dadashev

Similarity of the domain structure of proteins as a basis for the conservation of meiosis.

Meiosis is conserved in all eucaryotic kingdoms, and homologous rows of variability are revealed for the cytological traits of meiosis. To find the nature of these phenomenons, we reviewed the most-studied meiosis-specific proteins and studied them with the methods of bioinformatics. We found that synaptonemal complex proteins have no homology of amino-acid sequence, but are similar in the domain organization and three-dimensional (3D) structure of functionally important domains in budding yeast, nematode, Drosophila, Arabidopsis, and human. Recombination proteins of Rad51/Dmc1 family are conserved to the extent which permits them to make filamentous single-strand deoxyribonucleic acid (ssDNA)-protein intermediates of meiotic recombination. The same structural principles are valid for conservation of the ultrastructure of kinetochores, cell gap contacts, and nuclear pore complexes, such as in the cases when ultrastructure 3D parameters are important for the function. We suggest that self-assembly of protein molecules plays a significant role in building-up of all biological structures mentioned.

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 damages 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 damages 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 catastrophe and results in the degeneration of cells without enabling the mechanism of pachytene arrest. The features of pachytene arrest were revealed in the nuclei of primary spermatocytes with the violation 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.

On the Use of Alleles of Gliadin-Coding Loci as Possible Adaptability Markers in the Spring Wheat ( Triticum aestivum L.) Cultivars during Seed Germination

Prolamine proteolysis is assumed to be among numerous adaptability factors in cereals. The patterns of gliadin proteolysis have been studied in 16 cultivars of spring wheat via analysis of electrophoretic spectra. Four proteolytic patterns have been identified. It is hypothesized that the cultivars characterized by early and rapid proteolysis (the first and third types) are the most adaptable. The gliadin genetic formulas of chromosomes of the first homeologous group have been determined. The alleles of gliadin loci (Gli-A1f, Gli-B1e, Gli-D1a, and Gli-D1b) have been found that can be used as markers of adaptability in spring wheat cultivars.

Gene CG17604 of Drosophila melanogaster May Be a Functional Homolog of Yeast Gene ZIP1 and Mammal Gene SCP1 (SYCP1) Encoding Proteins of the Synaptonemal Complex

From data on the molecular organization of transverse filament proteins of the synaptonemal complex (SC)—Zip1 in yeast and SCP1 in mammals—and on the width of the SC central space in these organisms and in Drosophila, the putative molecular structure and size of a transverse filament protein of the SC in Drosophila has been inferred. Using genetic and molecular databases and software from the Internet, we carried out in silico screening for a candidate gene for the Drosophila transverse filament protein. As a most likely candidate, gene c(3)G was chosen. The search in the 250-kb region overlapping the locus of this gene (sections 88E-89B) and containing 78 predicted genes has revealed only one gene,CG17604, whose protein meets all requirements for the transverse filament protein of the SC. It was suggested that gene CG17604is gene c(3)G. In this case, genec(3)G must be localized in section 89A7-8 of the cytological map of Drosophila melanogaster.

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 B1 repeats and minisatellites were mostly attached to synaptonemal complexes immunostained with anti-SYCP3 antibodies. These results suggest that B1 repeats and minisatellites are candidates for sequences anchoring chromatin to synaptonemal complexes.

[In silico identification and characterization of meiotic DNA: AluJb possibly participates in the attachment of chromatin loops to synaptonemal complex].

Earlier, using bioinformatic methods, we reported the identification of repeated DNA sequences (RSs), presumably responsible for the attachment of chromatin loops to the lateral elements of synaptonemal complex in meiotic chromosomes. In the present study, consensus sequences for this class of RS were identified. It was demonstrated that at least part of these sequences belonged to the AluJb subfamily of Alu sequences. The Alu copies distribution along the major human histocompatibility complex (MHC) and their spatial separation from the sites of meiotic recombination was examined. It was demonstrated that simple sequences, like (GT/CA)n, were flanking meiotic recombination sites. A model of the RS organization in meiotic chromosome, most efficiently linking experimental data on the meiotic recombination in MHC and the in silico data on the RS localization (the coefficient of multiple correlation, r = 0.92) is suggested.

The Use of Artificial Neural Networks for Automatic Analysis and Genetic Identification of Gliadin Electrophoretic Spectra in Durum Wheat

Each wheat cultivar has a characteristic spectrum of gliadins. This makes it possible to use blocks of the components of reserve proteins as genetic markers when estimating seed purity and identity. However, identification of the blocks that constitute the electrophoretic spectrum is a complicated task. For this purpose artificial neural network (ANN) technology is proposed. Using experimental data, a teaching database and testing databases have been created. ANN was shown to be highly efficient (efficiency up to 100%) expert system for deciphering the electrophoretic spectra of gliadins of durum wheat cultivars.

Morphological manifestation of unique DNA segments in human meiotic prophase I

DNA attachment to the lateral elements of the synaptonemal complex (SC) in human spermatocytes was studied by the FISH technique using a commercial probe. The probe is a 160-kbp fragment from the 17p11.2 region containing the RAII gene and D17S620 marker (the probe for the deletion in human chromosome 17 causing Smith-Magenis syndrome). It was found that the DNA probe produced lateral chromatin protrusions in contact with SC stained with antibodies to SYCP3 protein. The morphological configuration of lateral chromatin protrusions depended on the substages of meiotic prophase I. At the zygotene, FISH probe forms two sticks with lengths about 6 μm perpendicular to the SC longitudinal axis, one stick at each SC side. At the early pachytene, each stick transforms into a globule, again one globule at each SC side. At the late pachytene, each globule transforms into two crumbly globules composed of short threads and clumps. At the diplotene, globules finally transform into thin DNA (chromatin) loops up to 10 μm from the base to the top with periodic thickenings (beads) along their length. As a result of this dynamic transformation, two chromatin loops with beads have been formed on each side of the SC of chromosome 17. These loops are most probably the loops of sister chromatides. Thereby, four loops of the full set of four chromatides were observed in the particular site of chromosome 17 bivalent, i.e., representing two pairs of chromatides. Thus, we are the first to have visualized true “open” lateral chromatin loops in human male meiotic prophase I rather than the usually postulated “loops” in reports on condensed road- or brushlike chromatin protrusions attached to the lateral elements of synaptonemal complexes. The open configuration of chromatin loops presumably depends on activation of transcription during the late pachytene-early diplotene. They resemble mini lateral loops of lampbrush chromosomes.

DNA repeated sequences may be involved in synaptonemal complex formation

Synaptonemal complexes (SCs) are intranuclear structures that facilitate the reversible lateral synapsis of homologous chromosomes in the course of meiosis. It is still unclear which DNA nucleotide sequences are responsible for the attachment of chromatin to SC lateral elements. Considering the features of the dispersed repeated sequences (RSs), it is possible to assume that they participate in the structure and functional organization of the meiotic chromosomes. Using numerical analysis, we have investigated the relationship between the RS and the distribution of meiotic recombination events in mouse chromosome 1. Using in situ hybridization on spread mouse spermatocytes, we have examined the arrangement of different types of RSs relative to SCs. Hybridization signals of B1(Alu), B2, and minisatellite probes were localized predominantly in SCs regions. Based on the results, we proposed a model of meiotic chromosome organization. According to the model, RSs participate in the attachment of chromatin loops to SCs.

Identification and Characterization in silico of Meiotic DNA

A method of in silico search for specific repetitive DNA sequences related to the synaptonemal complex (meiDNA) in mammalian genomes was developed. A study of the distribution of these repeats over chromosomes revealed their scarcity on the Y chromosome and a decrease in recombination frequency in regions enriched in meiDNA. The results are discussed in context of the model of the looplike meiotic chromosome organization during the formation of the synaptonemal complex.