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ring chromosome

Stephen M Hinshaw, Vasso Makrantoni, Stephen C Harrison, Adèle L Marston
The ring-shaped cohesin complex brings together distant DNA domains to maintain, express, and segregate the genome. Establishing specific chromosomal linkages depends on cohesin recruitment to defined loci. One such locus is the budding yeast centromere, which is a paradigm for targeted cohesin loading. The kinetochore, a multiprotein complex that connects centromeres to microtubules, drives the recruitment of high levels of cohesin to link sister chromatids together. We have exploited this system to determine the mechanism of specific cohesin recruitment...
September 21, 2017: Cell
Yasutaka Kakui, Frank Uhlmann
Chromatin is a very long DNA-protein complex that controls the expression and inheritance of the genetic information. Chromatin is stored within the nucleus in interphase and further compacted into chromosomes during mitosis. This process, known as chromosome condensation, is essential for faithful segregation of genomic DNA into daughter cells. Condensin and cohesin, members of the structural maintenance of chromosomes (SMC) family, are fundamental for chromosome architecture, both for establishment of chromatin structure in the interphase nucleus and for the formation of condensed chromosomes in mitosis...
September 21, 2017: Current Genetics
Daniel Beaudet, Tara Akhshi, Julia Phillipp, Christopher Law, Alisa Piekny
Cytokinesis cleaves a cell into two daughters at the end of mitosis, and must be spatially coordinated with chromosome segregation to prevent aneuploidy. The dogma is that the mitotic spindle governs the assembly and constriction of an actomyosin ring. Here, we reveal a function for active Ran in spatially restricting the ring. Our model is that during anaphase, 'free' importins, whose gradient inversely correlates with active Ran and chromatin position, function as a molecular ruler for the recruitment and localization of anillin, a contractile protein and crucial regulator of cytokinesis...
September 20, 2017: Molecular Biology of the Cell
James D P Rhodes, Judith H I Haarhuis, Jonathan B Grimm, Benjamin D Rowland, Luke D Lavis, Kim A Nasmyth
To ensure disjunction to opposite poles during anaphase, sister chromatids must be held together following DNA replication. This is mediated by cohesin, which is thought to entrap sister DNAs inside a tripartite ring composed of its Smc and kleisin (Scc1) subunits. How such structures are created during S phase is poorly understood, in particular whether they are derived from complexes that had entrapped DNAs prior to replication. To address this, we used selective photobleaching to determine whether cohesin associated with chromatin in G1 persists in situ after replication...
September 19, 2017: Cell Reports
Chanil Jeon, Youngkyun Jung, Bae-Yeun Ha
Macromolecular crowding influences various cellular processes such as macromolecular association and transcription, and is a key determinant of chromosome organization in bacteria. The entropy of crowders favors compaction of long chain molecules such as chromosomes. To what extent is the circular bacterial chromosome, often viewed as consisting of "two arms", organized entropically by crowding? Using computer simulations, we examine how a ring polymer is organized in a crowded and cylindrically-confined space, as a coarse-grained bacterial chromosome...
September 19, 2017: Scientific Reports
James Dp Rhodes, Davide Mazza, Kim A Nasmyth, Stephan Uphoff
The cohesin complex mediates DNA-DNA interactions both between (sister chromatid cohesion) and within chromosomes (DNA looping). It has been suggested that intra-chromosome loops are generated by extrusion of DNAs through the lumen of cohesin's ring. Scc2 (Nipbl) stimulates cohesin's ABC-like ATPase and is essential for loading cohesin onto chromosomes. However, it is possible that the stimulation of cohesin's ATPase by Scc2 also has a post-loading function, for example driving loop extrusion. Using fluorescence recovery after photobleaching (FRAP) and single- molecule tracking, we show that Scc2 binds dynamically to chromatin, principally through an association with cohesin...
September 15, 2017: ELife
Rossella Cannarella, Teresa Mattina, Rosita A Condorelli, Laura M Mongioì, Giuseppe Pandini, Sandro La Vignera, Aldo E Calogero
Insulin-like growth factor 1 receptor (IGF1R), mapping on the 15q26.3 chromosome, is required for normal embryonic and postnatal growth. The aim of the present study was to evaluate the IGF1R gene expression and function in three unrelated patients with chromosome 15 structural abnormalities. We report two male patients with the smallest 15q26.3 chromosome duplication described so far, and a female patient with ring chromosome 15 syndrome. Patient one, with a 568 kb pure duplication, had overgrowth, developmental delay, mental and psychomotor retardation, obesity, cryptorchidism, borderline low testis volume, severe oligoasthenoteratozoospermia and gynecomastia...
October 2017: Endocrine Connections
Chen Chen, Li-Wen Wu, Fang He, Li-Fen Yang, Pu Miao, Yu-Ping Ma, Xiao-Le Wang, Jing Peng
No abstract text is available yet for this article.
September 2017: Zhongguo Dang Dai Er Ke za Zhi, Chinese Journal of Contemporary Pediatrics
Inna E Pristyazhnyuk, Aleksei G Menzorov
Ring chromosomes (RCs) are circular DNA molecules, which occur rarely in eukaryotic nuclear genomes. Lilian Vaughan Morgan first described them in the fruit fly. Human embryos very seldom have RCs, about 1:50,000. Carriers of RCs may have varying degrees of symptoms, from healthy phenotype to serious pathologies in physical and intellectual development. Many authors describe common symptoms of RC presence: short stature and some developmental delay that could be described as a "ring chromosome syndrome." As a rule, RCs arise de novo through the end-joining of two DNA double-strand breaks, telomere-subtelomere junction, or inv dup del rearrangement in both meiosis and mitosis...
September 12, 2017: Protoplasma
Beatrice Oneda, Reza Asadollahi, Silvia Azzarello-Burri, Dunja Niedrist, Rosa Baldinger, Rahim Masood, Albert Schinzel, Bea Latal, Oskar G Jenni, Anita Rauch
Chromosomal mosaicism, which represents a diagnostic challenge for detection and interpretation, has been described in several genetic conditions. It can contribute to a large phenotypic variation in diseases. At analysis of a well-characterized cohort of 714 patients with neurodevelopmental disorders (NDDs) of unknown etiology using a high-resolution chromosomal microarray platform, we found 2 cases (0.28%) of low-level mosaicism and defined a previously detected extra chromosome in a third patient. Two of the cases were mosaics for segmental imbalances (a partial trisomy 3q26...
August 2017: Molecular Syndromology
John James Tello Cajiao, Mario Pietro Carante, Mario Antonio Bernal Rodriguez, Francesca Ballarini
Although chromosome aberrations are known to derive from distance-dependent mis-rejoining of chromosome fragments, evaluating whether a certain model describes such "proximity effects" better than another one is complicated by the fact that different approaches have often been tested under different conditions. Herein, a biophysical model ("BIANCA", i.e. BIophysical ANalysis of Cell death and chromosome Aberrations) was upgraded, implementing explicit chromosome-arm domains and two new models for the dependence of the rejoining probability on the fragment initial distance, r...
August 24, 2017: DNA Repair
Yonggang Lu, Minjie Lin, Robert John Aitken
In this study, we have investigated the impact of dibutyl phthalate (DBP) on early embryogenesis in a sessile marine invertebrate, Galeolaria caespitosa. DBP was found to induce sperm dysfunction as well as impaired and defective embryogenesis characterised by a particular pattern of abnormality. Thus, after the first cleavage, one blastomere in these abnormal embryos was able to carry out further mitoses, while the other arrested. Analysis of microtubules, chromosomes and actin filaments demonstrated that the mitotic spindles in the abnormal embryos were irregularly bent, shortened and unable to anchor to the cortex, resulting in the defective segregation of chromosomes...
August 19, 2017: Aquatic Toxicology
Larissa Wilhelm, Stephan Gruber
Chromosome organization, DNA replication, and transcription are only some of the processes relying on dynamic and highly regulated protein-DNA interactions. Here, we describe a biochemical assay to study the molecular details of associations between ring-shaped protein complexes and chromosomes in the context of living cells. Any protein complex embracing chromosomal DNA can be enriched by this method, allowing for the underlying loading mechanisms to be investigated.
2017: Methods in Molecular Biology
Matthew W Rosenbaum, Olga Pozdnyakova, Julia T Geyer, Paola Dal Cin, Robert Hasserjian
Ring chromosome (RC) is a poorly understood genetic anomaly seen in myeloid neoplasms. This study aims to shed light on the clinical significance of this finding. We identified 96 cases of myeloid neoplasms with RC from 3 academic hospitals. Clinicopathologic features and overall- (OS) and leukemia-free survival were reviewed and compared to cases of myeloid neoplasms lacking RC. We identified 59 acute myeloid leukemias (AML-RC) and 37 myelodysplastic syndromes (MDS-RC) with RC identified on routine karyotyping...
August 22, 2017: Human Pathology
Emilie Montembault, Marie-Charlotte Claverie, Lou Bouit, Cedric Landmann, James Jenkins, Anna Tsankova, Clemens Cabernard, Anne Royou
Chromatid segregation must be coordinated with cytokinesis to preserve genomic stability. Here we report that cells clear trailing chromatids from the cleavage site by undergoing two phases of cell elongation. The first phase relies on the assembly of a wide contractile ring. The second phase requires the activity of a pool of myosin that flows from the ring and enriches the nascent daughter cell cortices. This myosin efflux is a novel feature of cytokinesis and its duration is coupled to nuclear envelope reassembly and the nuclear sequestration of the Rho-GEF Pebble...
August 23, 2017: Nature Communications
Maria Helena Faria Ornellas, Maria Christina Paixão Maioli, Stella Beatriz Sampaio Gonçalves de Lucena, Elenice Ferreira Bastos, Tatiana Silva Chaves, Karina Vieira de Melo, Marilza de Moura Ribeiro-Carvalho, Thomas Liehr, Gilda Alves
CONTEXT: Complex karyotypes in acute myeloid leukemia (AML) are characterized by an overall low response rate with frequent relapses after clinical treatment. CASE REPORT: Here, we describe the case of a 61-year-old obese female with clinically diagnosed AML who presented a complex karyotype involving an uncommon abnormality: ring chromosome 11. Immunophenotypic analysis confirmed the diagnosis. Classical and molecular cytogenetic analyses, using GTG banding and FISH (fluorescence in situ hybridization), revealed the presence of complex structural rearrangement involving r(11), add(12)(p13), der(5) and der(13)...
August 21, 2017: São Paulo Medical Journal, Revista Paulista de Medicina
Anatoli Naumov, Stella Kratzer, Li-Min Ting, Kami Kim, Elena S Suvorova, Michael W White
Our knowledge of cell cycle regulatory mechanisms in apicomplexan parasites is very limited. In this study, we describe a novel Toxoplasma gondii factor that has a vital role in chromosome replication and the regulation of cytoplasmic and nuclear mitotic structures, and we named this factor ECR1 for essential for chromosome replication 1. ECR1 was discovered by complementation of a temperature-sensitive (ts) mutant that suffers lethal, uncontrolled chromosome replication at 40°C similar to a ts mutant carrying a defect in topoisomerase...
August 22, 2017: MBio
Ethan S Winter, Anna Schwarz, Gunar Fabig, Jessica L Feldman, André Pires-daSilva, Thomas Müller-Reichert, Penny L Sadler, Diane C Shakes
Asymmetric partitioning is an essential component of many developmental processes. As spermatogenesis concludes, sperm are streamlined by discarding unnecessary cellular into cellular wastebags called residual bodies (RBs). During nematode spermatogenesis, this asymmetric partitioning event occurs shortly after anaphase II, and both microtubules and actin partition into a central RB. Here we use fluorescence and transmission electron microscopy to elucidate and compare the intermediate steps of RB formation in C...
August 21, 2017: Development
Blerta Shtylla
We examine the localization patterns of ParA, ParB, PopZ, and MipZ, which are key division proteins in C. crescentus bacteria. While Par and PopZ proteins have been implicated in the physical segregation of the replicated chromosome, MipZ dimers control the placement of the cell division plane by preventing FtsZ proteins from assembling into a Z-ring. MipZ proteins generate bipolar gradients that are sensitive to Par protein localization, however, it is not understood how the MipZ gradient is shaped so as to allow for the correct Z-ring placement during asymmetric cell division in C...
August 18, 2017: Journal of Theoretical Biology
J Carter, H Brittain, D Morrogh, N Lench, J J Waters
Interstitial deletions of 4q are rarely reported, vary in size, and have limited genotype-phenotype correlations. Here, genome-wide array CGH analysis identified a 21.6 Mb region of copy number loss at 4q12-q21.1 in a patient diagnosed with dysmorphism, linear skin pigmentation, and hepatomegaly. An additional small ring chromosome was detected in 5/30 cells examined via G-banding. Confirmation of the origin of the ring chromosome was obtained by FISH analysis which identified that the ring chromosome contained material from the deleted region of chromosome 4 and was therefore complementary to the 21...
2017: Case Reports in Genetics
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