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Azahara C Martín, María-Dolores Rey, Peter Shaw, Graham Moore
Allopolyploids must possess a mechanism for facilitating synapsis and crossover (CO) between homologues, in preference to homoeologues (related chromosomes), to ensure successful meiosis. In hexaploid wheat, the Ph1 locus has a major effect on the control of these processes. Studying a wheat mutant lacking Ph1 provides an opportunity to explore the underlying mechanisms. Recently, it was proposed that Ph1 stabilises wheat during meiosis, both by promoting homologue synapsis during early meiosis and preventing MLH1 sites on synapsed homoeologues from becoming COs later in meiosis...
April 1, 2017: Chromosoma
Keyvan Torabi, Darawalee Wangsa, Immaculada Ponsa, Markus Brown, Anna Bosch, Maria Vila-Casadesús, Tatiana S Karpova, Maria Calvo, Antoni Castells, Rosa Miró, Thomas Ried, Jordi Camps
Human chromosomes occupy distinct territories in the interphase nucleus. Such chromosome territories (CTs) are positioned according to gene density. Gene-rich CTs are generally located in the center of the nucleus, while gene-poor CTs are positioned more towards the nuclear periphery. However, the association between gene expression levels and the radial positioning of genes within the CT is still under debate. In the present study, we performed three-dimensional fluorescence in situ hybridization experiments in the colorectal cancer cell lines DLD-1 and LoVo using whole chromosome painting probes for chromosomes 8 and 11 and BAC clones targeting four genes with different expression levels assessed by gene expression arrays and RT-PCR...
March 25, 2017: Chromosoma
Jeffrey G Ault, Kristen D Felt, Ryan N Doan, Alexander O Nedo, Cassondra A Ellison, Leocadia V Paliulis
During meiosis I, homologous chromosomes join together to form bivalents. Through trial and error, bivalents achieve stable bipolar orientations (attachments) on the spindle that eventually allow the segregation of homologous chromosomes to opposite poles. Bipolar orientations are stable through tension generated by poleward forces to opposite poles. Unipolar orientations lack tension and are stereotypically not stable. The behavior of sex chromosomes during meiosis I in the male black widow spider Latrodectus mactans (Araneae, Theridiidae) challenges the principles governing such a scenario...
February 23, 2017: Chromosoma
Dongjie Li, Jie Liu, Wu Liu, Guang Li, Zhongnan Yang, Peng Qin, Lin Xu
Imitation Switch (ISWI) is a member of the ATP-dependent chromatin remodeling factor family, whose members move or restructure nucleosomes using energy derived from ATP hydrolysis. ISWI proteins are conserved in eukaryotes and usually form complexes with DDT (DNA-binding homeobox and different transcription factors)-domain proteins. Here, we review recent research on ISWI in the model plant Arabidopsis thaliana (AtISWI). AtISWI forms complexes with AtDDT-domain proteins, many of which have domain structures that differ from those of DDT-domain proteins in yeast and animals...
February 17, 2017: Chromosoma
Josefa Cabrero, María Martín-Peciña, Francisco J Ruiz-Ruano, Ricardo Gómez, Juan Pedro M Camacho
Most supernumerary (B) chromosomes are parasitic elements carrying out an evolutionary arms race with the standard (A) chromosomes. A variety of weapons for attack and defense have evolved in both contending elements, the most conspicuous being B chromosome drive and A chromosome drive suppression. Here, we show for the first time that most microspermatids formed during spermiogenesis in two grasshopper species contain expulsed B chromosomes. By using DNA probes for B-specific satellite DNAs in Eumigus monticola and Eyprepocnemis plorans, and also 18S rDNA in the latter species, we were able to count the number of B chromosomes in standard spermatids submitted to fluorescence in situ hybridization, as well as visualizing B chromosomes inside most microspermatids...
February 11, 2017: Chromosoma
Benjamin M Skinner, Emma E P Johnson
Studies of chromosome and genome biology often focus on condensed chromatin in the form of chromosomes and neglect the non-dividing cells. Even when interphase nuclei are considered, they are often then treated as interchangeable round objects. However, different cell types can have very different nuclear shapes, and these shapes have impacts on cellular function; indeed, many pathologies are linked with alterations to nuclear shape. In this review, we describe some of the nuclear morphologies beyond the spherical and ovoid...
March 2017: Chromosoma
Érica Ramos, Adauto L Cardoso, Judith Brown, Diego F Marques, Bruno E A Fantinatti, Diogo C Cabral-de-Mello, Rogério A Oliveira, Rachel J O'Neill, Cesar Martins
Supernumerary chromosomes have been studied in many species of eukaryotes, including the cichlid fish, Astatotilapia latifasciata. However, there are many unanswered questions about the maintenance, inheritance, and functional aspects of supernumerary chromosomes. The cichlid family has been highlighted as a model for evolutionary studies, including those that focus on mechanisms of chromosome evolution. Individuals of A. latifasciata are known to carry up to two B heterochromatic isochromosomes that are enriched in repetitive DNA and contain few intact gene sequences...
March 2017: Chromosoma
Larisa Melnikova, Igor Shapovalov, Margarita Kostyuchenko, Pavel Georgiev, Anton Golovnin
Recent data suggest that insulators organize chromatin architecture in the nucleus. The best characterized Drosophila insulator, found in the gypsy retrotransposon, contains 12 binding sites for the Su(Hw) protein. Enhancer blocking, along with Su(Hw), requires BTB/POZ domain proteins, Mod(mdg4)-67.2 and CP190. Inactivation of Mod(mdg4)-67.2 leads to a direct repression of the yellow gene promoter by the gypsy insulator. Here, we have shown that such repression is regulated by the level of the EAST protein, which is an essential component of the interchromatin compartment...
March 2017: Chromosoma
Emad A Ahmed, Eukene Vélaz, Michael Rosemann, Klaus-P Gilbertz, Harry Scherthan
Noncycling and terminally differentiated (TD) cells display differences in radiosensitivity and DNA damage response. Unlike other TD cells, Sertoli cells express a mixture of proliferation inducers and inhibitors in vivo and can reenter the cell cycle. Being in a G1-like cell cycle stage, TD Sertoli cells are expected to repair DSBs by the error-prone nonhomologous end-joining pathway (NHEJ). Recently, we have provided evidence for the involvement of Ku-dependent NHEJ in protecting testis cells from DNA damage as indicated by persistent foci of the DNA double-strand break (DSB) repair proteins phospho-H2AX, 53BP1, and phospho-ATM in TD Sertoli cells of Ku70-deficient mice...
March 2017: Chromosoma
Samantha J Williams, Ariane Abrieu, Ana Losada
Centromeric chromatin containing the histone H3 variant centromere protein A (CENP-A) directs kinetochore assembly through a hierarchical binding of CENPs, starting with CENP-C and CENP-T. Centromeres are also the chromosomal regions where cohesion, mediated by cohesin, is most prominently maintained in mitosis. While most cohesin dissociates from chromosome arms in prophase, Shugoshin 1 (Sgo1) prevents this process at centromeres. Centromeric localization of Sgo1 depends on histone H2A phosphorylation by the kinase Bub1, but whether additional interactions with kinetochore components are required for Sgo1 recruitment is unclear...
March 2017: Chromosoma
Silvia Portela-Bens, Manuel Alejandro Merlo, María Esther Rodríguez, Ismael Cross, Manuel Manchado, Nadezda Kosyakova, Thomas Liehr, Laureana Rebordinos
The evolution of genes related to sex and reproduction in fish shows high plasticity and, to date, the sex determination system has only been identified in a few species. Solea senegalensis has 42 chromosomes and an XX/XY chromosome system for sex determination, while related species show the ZZ/ZW system. Next-generation sequencing (NGS), multi-color fluorescence in situ hybridization (mFISH) techniques, and bioinformatics analysis have been carried out, with the objective of revealing new information about sex determination and reproduction in S...
March 2017: Chromosoma
M Giovannotti, V A Trifonov, A Paoletti, I G Kichigin, P C M O'Brien, F Kasai, G Giovagnoli, B L Ng, P Ruggeri, P Nisi Cerioni, A Splendiani, J C Pereira, E Olmo, W Rens, V Caputo Barucchi, M A Ferguson-Smith
Anoles are a clade of iguanian lizards that underwent an extensive radiation between 125 and 65 million years ago. Their karyotypes show wide variation in diploid number spanning from 26 (Anolis evermanni) to 44 (A. insolitus). This chromosomal variation involves their sex chromosomes, ranging from simple systems (XX/XY), with heterochromosomes represented by either micro- or macrochromosomes, to multiple systems (X1X1X2X2/X1X2Y). Here, for the first time, the homology relationships of sex chromosomes have been investigated in nine anole lizards at the whole chromosome level...
March 2017: Chromosoma
Devika Ranade, Shivsmriti Koul, Joyce Thompson, Kumar Brajesh Prasad, Kundan Sengupta
Chromosome territories assume non-random positions in the interphase nucleus with gene-rich chromosomes localized toward the nuclear interior and gene-poor chromosome territories toward the nuclear periphery. Lamins are intermediate filament proteins of the inner nuclear membrane required for the maintenance of nuclear structure and function. Here, we show using whole-genome expression profiling that Lamin A/C or Lamin B2 depletion in an otherwise diploid colorectal cancer cell line (DLD1) deregulates transcript levels from specific chromosomes...
March 2017: Chromosoma
José R Cussiol, Diego Dibitetto, Achille Pellicioli, Marcus B Smolka
Homologous recombination-mediated DNA repair is essential for maintaining genome integrity. It is a multi-step process that involves resection of DNA ends, strand invasion, DNA synthesis and/or DNA end ligation, and finally, the processing of recombination intermediates such as Holliday junctions or other joint molecules. Over the last 15 years, it has been established that the Slx4 protein plays key roles in the processing of recombination intermediates, functioning as a scaffold to coordinate the action of structure-specific endonucleases...
February 2017: Chromosoma
Aurora Ruiz-Herrera, Miluse Vozdova, Jonathan Fernández, Hana Sebestova, Laia Capilla, Jan Frohlich, Covadonga Vara, Adrià Hernández-Marsal, Jaroslav Sipek, Terence J Robinson, Jiri Rubes
Homologous chromosomes exchange genetic information through recombination during meiosis, a process that increases genetic diversity, and is fundamental to sexual reproduction. In an attempt to shed light on the dynamics of mammalian recombination and its implications for genome organization, we have studied the recombination characteristics of 112 individuals belonging to 28 different species in the family Bovidae. In particular, we analyzed the distribution of RAD51 and MLH1 foci during the meiotic prophase I that serve, respectively, as proxies for double-strand breaks (DSBs) which form in early stages of meiosis and for crossovers...
January 18, 2017: Chromosoma
Vahideh Hassan-Zadeh, Peter Rugg-Gunn, David P Bazett-Jones
Epiblast stem cells (EpiSCs), which are pluripotent cells isolated from early post-implantation mouse embryos (E5.5), show both similarities and differences compared to mouse embryonic stem cells (mESCs), isolated earlier from the inner cell mass (ICM) of the E3.5 embryo. Previously, we have observed that while chromatin is very dispersed in E3.5 ICM, compact chromatin domains and chromocentres appear in E5.5 epiblasts after embryo implantation. Given that the observed chromatin re-organization in E5.5 epiblasts coincides with an increase in DNA methylation, in this study, we aimed to examine the role of DNA methylation in chromatin re-organization during the in vitro conversion of ESCs to EpiSCs...
January 13, 2017: Chromosoma
Sergey V Razin, Yegor S Vassetzky
No abstract text is available yet for this article.
December 15, 2016: Chromosoma
Dal-Hoe Koo, Wenxuan Liu, Bernd Friebe, Bikram S Gill
A crossover (CO) and its cytological signature, the chiasma, are major features of eukaryotic meiosis. The formation of at least one CO/chiasma between homologous chromosome pairs is essential for accurate chromosome segregation at the first meiotic division and genetic recombination. Polyploid organisms with multiple sets of homoeologous chromosomes have evolved additional mechanisms for the regulation of CO/chiasma. In hexaploid wheat (2n = 6× = 42), this is accomplished by pairing homoeologous (Ph) genes, with Ph1 having the strongest effect on suppressing homoeologous recombination and homoeologous COs...
December 1, 2016: Chromosoma
Taehyun Kim, Kathleen Plona, Anthony Wynshaw-Boris
Approximately 1 in 500 newborns are born with chromosomal abnormalities that include trisomies, translocations, large deletions, and duplications. There is currently no therapeutic approach for correcting such chromosomal aberrations in vivo or in vitro. When we attempted to produce induced pluripotent stem cell (iPSC) models from patient-derived fibroblasts that contained ring chromosomes, we found that the ring chromosomes were eliminated and replaced by duplicated normal copies of chromosomes through a mechanism of uniparental isodisomy (Bershteyn et al...
November 23, 2016: Chromosoma
Thomas Schalch, Florian A Steiner
The centromere is essential for the segregation of chromosomes, as it serves as attachment site for microtubules to mediate chromosome segregation during mitosis and meiosis. In most organisms, the centromere is restricted to one chromosomal region that appears as primary constriction on the condensed chromosome and is partitioned into two chromatin domains: The centromere core is characterized by the centromere-specific histone H3 variant CENP-A (also called cenH3) and is required for specifying the centromere and for building the kinetochore complex during mitosis...
November 17, 2016: Chromosoma
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