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Chromosoma

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https://www.readbyqxmd.com/read/29327130/main-steps-in-dna-double-strand-break-repair-an-introduction-to-homologous-recombination-and-related-processes
#1
REVIEW
Lepakshi Ranjha, Sean M Howard, Petr Cejka
DNA double-strand breaks arise accidentally upon exposure of DNA to radiation and chemicals or result from faulty DNA metabolic processes. DNA breaks can also be introduced in a programmed manner, such as during the maturation of the immune system, meiosis, or cancer chemo- or radiotherapy. Cells have developed a variety of repair pathways, which are fine-tuned to the specific needs of a cell. Accordingly, vegetative cells employ mechanisms that restore the integrity of broken DNA with the highest efficiency at the lowest cost of mutagenesis...
January 11, 2018: Chromosoma
https://www.readbyqxmd.com/read/29322240/ki-67-more-than-a-proliferation-marker
#2
REVIEW
Xiaoming Sun, Paul D Kaufman
Ki-67 protein has been widely used as a proliferation marker for human tumor cells for decades. In recent studies, multiple molecular functions of this large protein have become better understood. Ki-67 has roles in both interphase and mitotic cells, and its cellular distribution dramatically changes during cell cycle progression. These localizations correlate with distinct functions. For example, during interphase, Ki-67 is required for normal cellular distribution of heterochromatin antigens and for the nucleolar association of heterochromatin...
January 10, 2018: Chromosoma
https://www.readbyqxmd.com/read/29256059/x-inactivation-in-a-mammal-species-with-three-sex-chromosomes
#3
Frédéric Veyrunes, Julie Perez
X inactivation is a fundamental mechanism in eutherian mammals to restore a balance of X-linked gene products between XY males and XX females. However, it has never been extensively studied in a eutherian species with a sex determination system that deviates from the ubiquitous XX/XY. In this study, we explore the X inactivation process in the African pygmy mouse Mus minutoides, that harbours a polygenic sex determination with three sex chromosomes: Y, X, and a feminizing mutant X, named X*; females can thus be XX, XX*, or X*Y, and all males are XY...
December 18, 2017: Chromosoma
https://www.readbyqxmd.com/read/29250704/telomere-chromatin-establishment-and-its-maintenance-during-mammalian-development
#4
REVIEW
Mathieu Tardat, Jérôme Déjardin
Telomeres are specialized structures that evolved to protect the end of linear chromosomes from the action of the cell DNA damage machinery. They are composed of tandem arrays of repeated DNA sequences with a specific heterochromatic organization. The length of telomeric repeats is dynamically regulated and can be affected by changes in the telomere chromatin structure. When telomeres are not properly controlled, the resulting chromosomal alterations can induce genomic instability and ultimately the development of human diseases, such as cancer...
December 18, 2017: Chromosoma
https://www.readbyqxmd.com/read/29243212/controlling-centriole-numbers-geminin-family-members-as-master-regulators-of-centriole-amplification-and-multiciliogenesis
#5
REVIEW
Marina Arbi, Dafni-Eleftheria Pefani, Stavros Taraviras, Zoi Lygerou
To ensure that the genetic material is accurately passed down to daughter cells during mitosis, dividing cells must duplicate their chromosomes and centrosomes once and only once per cell cycle. The same key steps-licensing, duplication, and segregation-control both the chromosome and the centrosome cycle, which must occur in concert to safeguard genome integrity. Aberrations in genome content or centrosome numbers lead to genomic instability and are linked to tumorigenesis. Such aberrations, however, can also be part of the normal life cycle of specific cell types...
December 14, 2017: Chromosoma
https://www.readbyqxmd.com/read/29238858/spatial-organization-of-chromosome-territories-in-the-interphase-nucleus-of-trisomy-21-cells
#6
Stephan Kemeny, Christophe Tatout, Gaelle Salaun, Céline Pebrel-Richard, Carole Goumy, Natasha Ollier, Eugenie Maurin, Bruno Pereira, Philippe Vago, Laetitia Gouas
In the interphase cell nucleus, chromosomes adopt a conserved and non-random arrangement in subnuclear domains called chromosome territories (CTs). Whereas chromosome translocation can affect CT organization in tumor cell nuclei, little is known about how aneuploidies can impact CT organization. Here, we performed 3D-FISH on control and trisomic 21 nuclei to track the patterning of chromosome territories, focusing on the radial distribution of trisomic HSA21 as well as 11 disomic chromosomes. We have established an experimental design based on cultured chorionic villus cells which keep their original mesenchymal features including a characteristic ellipsoid nuclear morphology and a radial CT distribution that correlates with chromosome size...
December 14, 2017: Chromosoma
https://www.readbyqxmd.com/read/29234867/photoconversion-of-dapi-and-hoechst-dyes-to-green-and-red-emitting-forms-after-exposure-to-uv-excitation
#7
Travis J Karg, Kent G Golic
The fluorescent dye 4'-6-Diamidino-2-phenylindole (DAPI) is frequently used in fluorescence microscopy as a chromosome and nuclear stain because of its high specificity for DNA. Normally, DAPI bound to DNA is maximally excited by ultraviolet (UV) light at 358 nm, and emits maximally in the blue range, at 461 nm. Hoechst dyes 33258 and 33342 have similar excitation and emission spectra and are also used to stain nuclei and chromosomes. It has been reported that exposure to UV can convert DAPI and Hoechst dyes to forms that are excited by blue light and emit green fluorescence, potentially confusing the interpretation of experiments that use more than one fluorochrome...
December 12, 2017: Chromosoma
https://www.readbyqxmd.com/read/29230532/rna-mediated-transgenerational-inheritance-in-ciliates-and-plants
#8
REVIEW
Zachary T Neeb, Mariusz Nowacki
In the age of next-generation sequencing (NGS) and with the availability of whole sequenced genomes and epigenomes, some attention has shifted from purely sequence-based studies to those of heritable epigenetic modifications. Transgenerational inheritance can be defined as heritable changes to the state of DNA that may be passed on to subsequent generations without alterations to the underlying DNA sequence. Although this phenomenon has been extensively studied in many systems, studies of transgenerational inheritance in mammals and other higher-level eukaryotes may be complicated by the fact that many epigenetic marks are reprogrammed during sexual reproduction...
December 11, 2017: Chromosoma
https://www.readbyqxmd.com/read/29192338/evolutionary-trends-in-animal-ribosomal-dna-loci-introduction-to-a-new-online-database
#9
Jana Sochorová, Sònia Garcia, Francisco Gálvez, Radka Symonová, Aleš Kovařík
Ribosomal DNA (rDNA) loci encoding 5S and 45S (18S-5.8S-28S) rRNAs are important components of eukaryotic chromosomes. Here, we set up the animal rDNA database containing cytogenetic information about these loci in 1343 animal species (264 families) collected from 542 publications. The data are based on in situ hybridisation studies (both radioactive and fluorescent) carried out in major groups of vertebrates (fish, reptiles, amphibians, birds, and mammals) and invertebrates (mostly insects and mollusks). The database is accessible online at www...
November 30, 2017: Chromosoma
https://www.readbyqxmd.com/read/29151149/impact-of-xist-rna-on-chromatin-modifications-and-transcriptional-silencing-maintenance-at-different-stages-of-imprinted-x-chromosome-inactivation-in-vole-microtus-levis
#10
Alexander I Shevchenko, Elena V Grigor'eva, Sergey P Medvedev, Irina S Zakharova, Elena V Dementyeva, Eugeny A Elisaphenko, Anastasia A Malakhova, Sophia V Pavlova, Suren M Zakian
In vole Microtus levis, cells of preimplantation embryo and extraembryonic tissues undergo imprinted X chromosome inactivation (iXCI) which is triggered by a long non-coding nuclear RNA, Xist. At early stages of iXCI, chromatin of vole inactive X chromosome is enriched with the HP1 heterochromatin-specific protein, trimethylated H3K9 and H4K20 attributable to constitutive heterochromatin. In the study, using vole trophoblast stem (TS) cells as a model of iXCI, we further investigated chromatin of the inactive X chromosome of M...
November 18, 2017: Chromosoma
https://www.readbyqxmd.com/read/29124392/tracking-the-evolutionary-pathway-of-sex-chromosomes-among-fishes-characterizing-the-unique-xx-xy1y2-system-in-hoplias-malabaricus-teleostei-characiformes
#11
Ezequiel Aguiar de Oliveira, Alexandr Sember, Luiz Antonio Carlos Bertollo, Cassia Fernanda Yano, Tariq Ezaz, Orlando Moreira-Filho, Terumi Hatanaka, Vladimir Trifonov, Thomas Liehr, Ahmed Basheer Hamid Al-Rikabi, Petr Ráb, Hugmar Pains, Marcelo de Bello Cioffi
The Neotropical fish, Hoplias malabaricus, is one of the most cytogenetically studied fish taxon with seven distinct karyomorphs (A-G) comprising varying degrees of sex chromosome differentiation, ranging from homomorphic to highly differentiated simple and multiple sex chromosomes. Therefore, this fish offers a unique opportunity to track evolutionary mechanisms standing behind the sex chromosome evolution and differentiation. Here, we focused on a high-resolution cytogenetic characterization of the unique XX/XY1Y2 multiple sex chromosome system found in one of its karyomorphs (G)...
November 9, 2017: Chromosoma
https://www.readbyqxmd.com/read/29079971/characterization-of-the-lamin-analogue-nmcp2-in-the-monocot-allium-cepa
#12
Malgorzata Ciska, Kiyoshi Masuda, Susana Moreno Díaz de la Espina
Nuclear lamina organization is similar in metazoan and plants though the latter lack orthologs of lamins, the main components of the metazoan lamina. Current evidence suggests that Nuclear Matrix Constituent Proteins (NMCPs) are the lamin analogues in plants as these proteins share several key features: higher-order secondary structure and domain layout, subnuclear distribution, and involvement in the regulation of nuclear shape and size, as well as in higher-order chromatin organization. Previously, we studied the NMCP family in flowering plants (angiosperms), in which it comprises two phylogenetic groups: NMCP1 and NMCP2...
October 27, 2017: Chromosoma
https://www.readbyqxmd.com/read/28821911/erratum-to-unique-sequence-organization-and-small-rna-expression-of-a-selfish-b-chromosome
#13
Yue Li, Xueyuan A Jing, John C Aldrich, C Clifford, Jian Chen, Omar S Akbari, Patrick M Ferree
No abstract text is available yet for this article.
December 2017: Chromosoma
https://www.readbyqxmd.com/read/28803373/th2a-is-phosphorylated-at-meiotic-centromere-by-haspin
#14
Masashi Hada, Jihye Kim, Erina Inoue, Yuko Fukuda, Hiromitsu Tanaka, Yoshinori Watanabe, Yuki Okada
Histone phosphorylation is sometimes associated with mitosis and meiosis. We have recently identified a phosphorylation of the 127th threonine on TH2A (pTH2A), a germ cell-specific H2A variant, in condensed spermatids and mitotic early preimplantation embryos of mice. Here, we further report the existence of pTH2A at the centromeres in metaphase I spermatocytes and oocytes. Moreover, we identified Haspin, a known kinase for the 3rd threonine on H3, is responsible for pTH2A in vivo. In contrast to the severe meiotic defect in oocytes treated with a Haspin inhibitor, pTH2A-deficient mice, in which the 127th threonine was replaced by alanine, maintained the fertility and exhibited no obvious defect in both oocytes and spermatogenesis...
December 2017: Chromosoma
https://www.readbyqxmd.com/read/28780664/unique-sequence-organization-and-small-rna-expression-of-a-selfish-b-chromosome
#15
Yue Li, Xueyuan A Jing, John C Aldrich, C Clifford, Jian Chen, Omar S Akbari, Patrick M Ferree
B chromosomes are found in numerous plants and animals. These nonessential, supernumerary chromosomes are often composed primarily of noncoding DNA repeats similar to those found within transcriptionally "silenced" heterochromatin. In order to persist within their resident genomes, many B chromosomes exhibit exceptional cellular behaviors, including asymmetric segregation into gametes and induction of genome elimination during early development. An important goal in understanding these behaviors is to identify unique B chromosome sequences and characterize their transcriptional contributions...
December 2017: Chromosoma
https://www.readbyqxmd.com/read/28766050/unique-xci-evolution-in-tokudaia-initial-xci-of-the-neo-x-chromosome-in-tokudaia-muenninki-and-function-loss-of-xist-in-tokudaia-osimensis
#16
Hideki Zushi, Chie Murata, Shusei Mizushima, Chizuko Nishida, Asato Kuroiwa
X chromosome inactivation (XCI) is an essential mechanism to compensate gene dosage in mammals. Here, we show that XCI has evolved differently in two species of the genus Tokudaia. The Amami spiny rat, Tokudaia osimensis, has a single X chromosome in males and females (XO/XO). By contrast, the Okinawa spiny rat, Tokudaia muenninki, has XX/XY sex chromosomes like most mammals, although the X chromosome has acquired a neo-X region by fusion with an autosome. BAC clones containing the XIST gene, which produces the long non-coding RNA XIST required for XCI, were obtained by screening of T...
December 2017: Chromosoma
https://www.readbyqxmd.com/read/28756515/reconstruction-of-chromosome-rearrangements-between-the-two-most-ancestral-duckweed-species-spirodela-polyrhiza-and-s-intermedia
#17
Phuong T N Hoang, Ingo Schubert
The monophyletic duckweeds comprising five genera within the monocot order Alismatales are neotenic, free-floating, aquatic organisms with fast vegetative propagation. Some species are considered for efficient biomass production, for life stock feeding, and for (simultaneous) wastewater phytoremediation. The ancestral genus Spirodela consists of only two species, Spirodela polyrhiza and Spirodela intermedia, both with a similar small genome (~160 Mbp/1C). Reference genome drafts and a physical map of 96 BACs on the 20 chromosome pairs of S...
December 2017: Chromosoma
https://www.readbyqxmd.com/read/28688040/identification-of-all-homoeologous-chromosomes-of-newly-synthetic-allotetraploid-cucumis-%C3%A3-hytivus-and-its-wild-parent-reveals-stable-subgenome-structure
#18
Yunzhu Wang, Qinzheng Zhao, Xiaodong Qin, Shuqiong Yang, Ziang Li, Ji Li, Qunfeng Lou, Jinfeng Chen
Allopolyploidy and homoeologous recombination are two important processes in reshaping genomes and generating evolutionary novelties. Newly formed allopolyploids usually display chromosomal perturbations as a result of pairing errors at meiosis. To understand mechanisms of stabilization of allopolyploid species derived from distant chromosome bases, we investigated mitotic stability of a synthetic Cucumis allotetraploid species in relation to meiosis chromosome behavior. The Cucumis × hytivus is an allotetraploid synthesized from interspecific hybridization between cucumber (Cucumis sativus, 2n = 14) and its wild relative Cucumis hystrix (2n = 24) followed by spontaneous chromosome doubling...
December 2017: Chromosoma
https://www.readbyqxmd.com/read/28688038/dadd1-and-dxnp-prevent-genome-instability-by-maintaining-hp1a-localization-at-drosophila-telomeres
#19
Joselyn Chavez, Juan Manuel Murillo-Maldonado, Vanessa Bahena, Ana Karina Cruz, América Castañeda-Sortibrán, Rosario Rodriguez-Arnaiz, Mario Zurita, Viviana Valadez-Graham
Telomeres are important contributors to genome stability, as they prevent linear chromosome end degradation and contribute to the avoidance of telomeric fusions. An important component of the telomeres is the heterochromatin protein 1a (HP1a). Mutations in Su(var)205, the gene encoding HP1a in Drosophila, result in telomeric fusions, retrotransposon regulation loss and larger telomeres, leading to chromosome instability. Previously, it was found that several proteins physically interact with HP1a, including dXNP and dAdd1 (orthologues to the mammalian ATRX gene)...
December 2017: Chromosoma
https://www.readbyqxmd.com/read/28975408/genome-wide-analysis-of-su-var-3-9-distribution-in-chromosomes-of-drosophila-melanogaster
#20
Daniil A Maksimov, Petr P Laktionov, Olga V Posukh, Stepan N Belyakin, Dmitry E Koryakov
Histone modifications represent one of the key factors contributing to proper genome regulation. One of histone modifications involved in gene silencing is methylation of H3K9 residue. Present in the chromosomes across different eukaryotes, this epigenetic mark is controlled by SU(VAR)3-9 and its orthologs. Despite SU(VAR)3-9 was discovered over two decades ago, little is known about the details of its chromosomal distribution pattern. To fill in this gap, we used DamID-seq approach and obtained high-resolution genome-wide profiles for SU(VAR)3-9 in two somatic (salivary glands and brain ganglia) and two germline (ovarian nurse cells and testes) tissues of Drosophila melanogaster...
October 3, 2017: Chromosoma
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