In diplotene oocyte nuclei of all vertebrate species, except mammals, chromosomes lack interchromosomal contacts and chromatin is linearly compartmentalized into distinct chromomere-loop complexes forming lampbrush chromosomes. However, the mechanisms underlying the formation of chromomere-loop complexes remain unexplored. Here we aimed to juxtapose somatic topologically associating domains (TADs), recently identified in chicken embryonic fibroblasts, with chromomere-loop complexes in lampbrush meiotic chromosomes.By measuring 3D-distances and colocalization between linear equidistantly located genomic loci, positioned within one TAD or separated by a TAD border, we confirmed the presence of predicted TADs in chicken embryonic fibroblast nuclei. Using three-colored FISH with BAC probes we mapped equidistant genomic regions included in several sequential somatic TADs on isolated chicken lampbrush chromosomes. Eight genomic regions, each comprising two or three somatic TADs, were mapped to non-overlapping neighboring lampbrush chromatin domainslateral loops, chromomeres or chromomere-loop complexes. Genomic loci from the neighboring somatic TADs could localize in one lampbrush chromomere-loop complex, while genomic loci belonging to the same somatic TAD could be localized in neighboring lampbrush chromomereloop domains. In addition, FISH-mapping of BAC probes to the nascent transcripts on the lateral loops indicates transcription of at least 17 protein-coding genes and 2 non-coding RNA genes during the lampbrush stage of chicken oogenesis, including genes involved in oocyte maturation and early embryo development.
Conclusions: Here we show that the loss or over-expression of CHD1 severely and very specifically affect the global chromatin organization of Drosophila polytene chromosomes� Our finding suggests a new link between the organization of hyperactive chromatin of the male X-chromosome and of transcriptionally silent heterochromatin�
In diplotene oocyte nuclei of all vertebrate species, except mammals, chromosomes lack interchromosomal contacts and chromatin is linearly compartmentalized into distinct chromomere-loop complexes forming lampbrush chromosomes. However, the mechanisms underlying the formation of chromomere-loop complexes remain unexplored. Here we aimed to juxtapose somatic topologically associating domains (TADs), recently identified in chicken embryonic fibroblasts, with chromomere-loop complexes in lampbrush meiotic chromosomes. By measuring 3D-distances and colocalization between linear equidistantly located genomic loci, positioned within one TAD or separated by a TAD border, we confirmed the presence of predicted TADs in chicken embryonic fibroblast nuclei. Using three-colored FISH with BAC probes we mapped equidistant genomic regions included in several sequential somatic TADs on isolated chicken lampbrush chromosomes. Eight genomic regions, each comprising two or three somatic TADs, were mapped to non-overlapping neighboring lampbrush chromatin domains – lateral loops, chromomeres or chromomere-loop complexes. Genomic loci from the neighboring somatic TADs could localize in one lampbrush chromomere-loop complex, while genomic loci belonging to the same somatic TAD could be localized in neighboring lampbrush chromomere- loop domains. In addition, FISH-mapping of BAC probes to the nascent transcripts on the lateral loops indicates transcription of at least 17 protein-coding genes and 2 non-coding RNA genes during the lampbrush stage of chicken oogenesis, including genes involved in oocyte maturation and early embryo development.
Background. Long coevolution of prey and predator species of mammals creates specific mechanisms of their interaction, e. g. prey’s innate behavior aversive to the predator odor. However, little is known about genetic responses in the prey organism. We assessed genome instability of the bone marrow cells in mice affected by the cat’s odor influence, and proposed pathway of such action. Materials and methods. CBA mouse males were exposed to volatiles from adult cat urine for 2 or 24 hours. To estimate the genetic effect, ana-telophase method of chromosome aberration analysis and comet assay were used. The level of corticosterone was also measured after the exposure for 30 or 60 minutes. Results. The exposure to cat’s urine volatiles for 2 hours induced damage of DNA in bone marrow cells of the mouse males as was shown by the DNA comet analysis. The exposure for 24 hours elevated the frequency of chromosome aberrations in mitotically dividing cells at ana-telophase stage. No significant changes were found in the level of corticosterone in the peripheral blood. Conclusion. We have shown that volatile chemosignals from predator’s urine induce genomic instability in bone marrow cells of a prey. The hormonal pathway of such influence is still unknown. Intraorganismic paths leading to genome damage are discussed as well as far consequences of discovered effects.
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