Search for functional amyloid structures in chicken and fruit fly female reproductive cells.

We conducted a cytological search for amyloid structures in female reproductive cells of Gallus gallus domesticus and Drosophila melanogaster. We have shown that the amyloid-specific dye, Thioflavin S, but not Congo red, stains some cytoplasmic and even nuclear structures in chicken ovaries. In fruit fly eggs both Thioflavin S and Congo red specifically stain eggshell structures such as micropyle, dorsal appendages and pillars. Moreover, these structures, when stained with Congo red, demonstrate birefringence in polarized light, which is a characteristic feature of all classical amyloids. Our data show that female reproductive cells during evolution began to use amyloid fibrils to form various functional structures necessary for development under certain environmental conditions.

Mitochondrial DNA D-loop haplogroup contributions to the genetic diversity of East European domestic chickens from Russia.

To elucidate geographical and historical aspects of chicken dispersal across Eastern Europe, we analysed the complete mitochondrial DNA D-loop sequence of 86 representatives from chicken breeds traditionally raised in the territory of the East European Plain (Orloff, Pavlov, Russian White, Yurlov Crower, Uzbek Game and Naked Neck). From the 1231-1232 bp D-loop sequence, 35 variable sites that defined 22 haplotypes were identified in modern chicken. All populations, except Uzbek Game, exhibited high values of haplotype and nucleotide diversity suggesting a wide variation in maternal diversity. Inclusion of mtDNA sequences from other European and Asian countries revealed representatives from this study belonging to haplogroups A, E1 and C1. We also assessed fossil chicken material dated to the 9th-18th century from archaeological sites in Northern and Eastern Europe. Three haplotypes found in the fossil specimens belonged to haplogroup E1, while one sample dated to the 18th century was assigned to the C1 haplogroup. This is the first report of the occurrence of the C1 haplogroup in European chicken populations prior to the 20th century based on the fossil material. These results provide evidence for a relatively recent introduction of all haplotypes other than E1 into the East European chicken gene pool with the significant impact of the C1 haplogroup mainly distributed in Southern China.

HE ROLE OF REPETITIVE SEQUENCES IN THE EVOLUTION OF SEX CHROMOSOMES IN BIRDS.

In this paper, we analyzed the distribution and the transcriptional activity of different repetitive elements in the sex chromosomes of chicken at the lampbrush stage. Based on these results, we suggest participation of interspersed repeats in the maintenance evolutionarily significant level of variability of heteromorphic sex chromosomes in birds. Analysis of the organization peculiarities of chicken sex chromosome W specific repeats allowed us to hypothesize that the accumulation of tandem repeats enriched with homopurine tracks is significant for the evolution of sex chromosomes.

[Lampbrush chromosomes of the Japanese quail (Coturnix coturnix japonica): a new version of cytogenetic maps].

Avian oocyte chromosomes are transfomed into giant transcriptionally active lampbrush chromosomes (LBCs) at meiosis 1 diplotene. These chromosomes are a convenient tool for high-resulution cytogenetic analysis. Using differential staining with fluorochromes DAPI and CMA3, we have constructed detailed cytological maps for lampbrush macrochromosomes 1-5 and ZW of the Japanese quail Coturnix coturnix japonica. We also performed a comparative analysis ofmitotic chromosomes and LBCs corresponding to them. We estimated the decondensation coefficient during LBC formation and determined the centromere indices for mitotic and diplotene chromosomes and thus found that different chromosomes and chromosomal regions demonstrate unequal degrees of decondensation.

[Crossing over in the oogenesis of Gallus gallus domesticus chickens: periodicity in the distribution of chiasmata over the length of chromosomes].

The periodic occurrence of chiasmata was studied in lampbrush chromosomes of the chicken (Gallus gallus domesticus). It was shown that the most probable interference distance in chicken macrobivalents 1-3 corresponded to 24.48 Mb. The distance at which absolute interference is observed in chicken macrochromosomes varies from 5.75 to 9.02 Mb.

Cytogenetic repartition of chicken CR1 sequences evidenced by PRINS in Galliformes and some other birds.

Chicken repeat 1 (CR1) belongs to the non-long repeat class of retrotransposons. Nearly 100000 repeats interspersed in the chicken genome are subdivided into at least six distinct subfamilies, each 300 bp long and all sharing substantial sequence similarity. CR1-like elements were found in genomes from invertebrates to mammals, suggesting their importance for genome structure and/or function. Moreover, numerous data support the hypothesis of their implication in regulation of gene expression. So, the chromosomal distribution of these CR1 sequences in vertebrates is of great interest to improve our knowledge about the genome structure, function and evolution. A comparison of the cytogenetic distribution of CR1 sequences was performed by PRINS using consensus chicken primers on the chromosomes of chicken and species of several bird orders: Galliformes, Anseriformes, Passeriformes and Falconiformes. The study revealed that CR1 repeats are spread over nearly all chicken chromosomes with a higher density on the macrochromosomes and in particular with hot spots on subtelomeric regions of chromosome 1, 2, 3q, 4q, 5q. Their distribution on the macrochromosomes forms a kind of banding pattern, which was not systematically matched with R- or G-banding. This banding pattern appears to be conserved on the chromosomes of the Galliformes studied, irrespective of their karyotypes, rearranged or not. CR1 primers also show similar signals on the chromosomes of birds phylogenetically more distant (Anseriformes, Passeriformes and Falconiformes). This fact confirms the importance of these sequences at the large scale of bird evolution and in the chromosomal structure. The location of CR1 sequences, and in particular of the hot spots, mainly within the richest CG areas are in conformity with the data on an epigenetic role of these highly conserved sequences.

Crossing over in chicken oogenesis: cytological and chiasma-based genetic maps of the chicken lampbrush chromosome 1.

Chiasmata in diplotene bivalents are located at the points of physical exchange (crossing-over) between homologous chromosomes. We have studied chiasma distribution within chicken lampbrush chromosome 1 to estimate the crossing-over frequency between chromosome landmarks. The position of the centromere and chromosome region 1q3.3-1q3.6 on lampbrush chromosome 1 were determined by comparative physical mapping of the TTAGGG repeats in the chicken mitotic and lampbrush chromosomes. The comparison of the chiasma (=crossing over)-based genetic distances on chicken chromosome 1 with the genetic linkage map obtained in genetic experiments showed that current genetic distances estimated by the high-resolution genetic mapping of the East Lansing, Compton, and Wageningen chicken reference populations are 1.2-1.9 times longer than those based on chiasma counts. Conceivable reasons for this discrepancy are discussed.

Compositional mapping of chicken chromosomes and identification of the gene-richest regions.

'Compositional chromosomal mapping', namely the assessment of the GC level of chromosomal bands, led to the identification, in the human chromosomes, of the GC-richest H3+ bands and of the GC-poorest L1+ bands, which were so called on the basis of the isochore family predominantly present in the bands. The isochore organization of the avian genome is very similar to those of most mammals, the only difference being the presence of an additional, GC-richest, H4 isochore family. In contrast, the avian karyotypes are very different from those of mammals, being characterized, in most species, by few macrochromosomes and by a large number of microchromosomes. The 'compositional mapping' of chicken mitotic and meiotic chromosomes by in-situ hybridization of isochore families showed that the chicken GC-richest isochores are localized not only on a large number of microchromosomes but also on almost all telomeric bands of macrochromosomes. On the other hand, the GC-poorest isochores are generally localized on the internal regions of macrochromosomes and are almost absent in microchromosomes. Thus, the distinct localization of the GC-richest and the GC-poorest bands observed on human chromosomes appears to be a general feature of chromosomes from warm-blooded vertebrates.

[Determination of the minimum size of Gallus gallus domesticus chicken microchromosome by a pulse electrophoresis method]. / Opredelenie minimal'nogo razmera mikrokhromosom kuritsy Gallus gallus domesticus metodom pul's-élektroforeza.

The karyotype of the chicken Gallus gallus domesticus was studied by means of pulsed-field electrophoresis. An electrokaryogram was obtained for the microchromosomal (MI) portion of the chicken genome. Chicken MIs were separated into two fractions. A fraction with a higher mobility included MIs sized 3.4-4.8 Mb; the lower size limit of a less mobile fraction corresponded to MIs of approximately 5 Mb. The smallest MI in the chicken karyotype was estimated at 3.4 +/- 0.25 Mb.