DNA changes involved in the formation of metaphase chromosomes, as observed in mouse duodenal crypt cells stained by osmium-ammine I. New structures arise during the S phase and condense at prophase into ?chromomeres,? which fuse at prometaphase into mitotic chromosomes

1995 ◽  
Vol 242 (4) ◽  
pp. 433-448 ◽  
Author(s):  
Mohamed El-Alfy ◽  
Dong Feng Liu ◽  
Charles Philippe Leblond
Keyword(s):  
S Phase ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Crypt Cells

scholarly journals Units of chromosome replication and packing

1983 ◽  
Vol 64 (1) ◽  
pp. 179-193
Author(s):  
A.M. Mullinger ◽  
R.T. Johnson
Keyword(s):  
Spatial Distribution ◽  
Light Microscope ◽  
Individual Cell ◽  
S Phase ◽  
Scanning Electron Micrographs ◽  
Metaphase Chromosomes ◽  
Impregnation Technique ◽  
Osmium Impregnation ◽  
The Relationship ◽  
Scanning Electron

Fusion between mitotic and S-phase cells induces the formation of prematurely condensed chromosomes (PCC) in the interphase partner. Viewed in the light microscope, S-phase PCC derived from the Indian muntjac appear to be fragmented and heterogeneous. In scanning electron micrographs prepared by an osmium impregnation technique, which avoids the need to sputter-coat the specimen, the S-phase fragments derived from an individual cell are resolved into about 1000 fibre aggregates, together with more dispersed fibres. Aggregates are roughly spherical and vary in diameter between about 0.25 and 1.6 micron. The spatial distribution of the aggregates shows some order: chains of single aggregates and, less commonly, duplicated chains occur. Regions of the PCC where the fibres are more dispersed are considered to be likely candidates for sites of replication at the time of fusion. The relationship between the condensed aggregate structure of the S-phase PCC and replication clusters is discussed, and also the assembly of aggregates to form metaphase chromosomes.

scholarly journals Chromosome disentanglement driven via optimal compaction of loop-extruded brush structures

2019 ◽  
Vol 116 (50) ◽  
pp. 24956-24965 ◽  
Author(s):  
Sumitabha Brahmachari ◽  
John F. Marko
Keyword(s):  
Expression Patterns ◽  
Polymer Brush ◽  
Mitotic Chromosomes ◽  
Mechanical Stiffness ◽  
Structural Reorganization ◽  
Metaphase Chromosomes ◽  
Dna Topoisomerase ◽  
Topo Ii ◽  
Strand Passage

Eukaryote cell division features a chromosome compaction–decompaction cycle that is synchronized with their physical and topological segregation. It has been proposed that lengthwise compaction of chromatin into mitotic chromosomes via loop extrusion underlies the compaction-segregation/resolution process. We analyze this disentanglement scheme via considering the chromosome to be a succession of DNA/chromatin loops—a polymer “brush”—where active extrusion of loops controls the brush structure. Given type-II DNA topoisomerase (Topo II)-catalyzed topology fluctuations, we find that interchromosome entanglements are minimized for a certain “optimal” loop that scales with the chromosome size. The optimal loop organization is in accord with experimental data across species, suggesting an important structural role of genomic loops in maintaining a less entangled genome. Application of the model to the interphase genome indicates that active loop extrusion can maintain a level of chromosome compaction with suppressed entanglements; the transition to the metaphase state requires higher lengthwise compaction and drives complete topological segregation. Optimized genomic loops may provide a means for evolutionary propagation of gene-expression patterns while simultaneously maintaining a disentangled genome. We also find that compact metaphase chromosomes have a densely packed core along their cylindrical axes that explains their observed mechanical stiffness. Our model connects chromosome structural reorganization to topological resolution through the cell cycle and highlights a mechanism of directing Topo II-mediated strand passage via loop extrusion-driven lengthwise compaction.

Cytogenetic studies on Sauria (Reptilia). I. Mitotic chromosomes of the Agamidae

1988 ◽  
Vol 9 (3) ◽  
pp. 301-310 ◽  
Author(s):  
E. Solleder ◽  
M. Schmid
Keyword(s):  
Chromosome Number ◽  
Chromosome Morphology ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Banding Patterns ◽  
The Family ◽  
Telocentric Chromosomes ◽  
Cytogenetic Studies ◽  
Pericentric Inversions ◽  
Dna Organization

The karotypes of nine species of the family Agamidae were analyzed with various banding techniques and conventional cytogenetic stainings. Whereas the examined species of the genera Calotes and Leiolepis exhibit conservative karyotypes, the chromosome number and chromosome morphology varies considerably within the genus Agama. This is attributed to centric fusions between telocentric chromosomes and pericentric inversions within the chromosomes. None of the species demonstrated multiple quinacrine banding patterns in the euchromatic segments of the metaphase chromosomes. This is probably due to the special DNA organization in these organisms.

scholarly journals Mouse satellite DNA, centromere structure, and sister chromatid pairing.

1986 ◽  
Vol 103 (4) ◽  
pp. 1145-1151 ◽  
Author(s):  
L M Lica ◽  
S Narayanswami ◽  
B A Hamkalo
Keyword(s):  
Electron Microscopy ◽  
Sister Chromatid ◽  
Satellite Dna ◽  
Marker Chromosome ◽  
Restriction Enzymes ◽  
Centromeric Heterochromatin ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Sister Chromatids ◽  
Mouse Satellite Dna

The experiments described were directed toward understanding relationships between mouse satellite DNA, sister chromatid pairing, and centromere function. Electron microscopy of a large mouse L929 marker chromosome shows that each of its multiple constrictions is coincident with a site of sister chromatid contact and the presence of mouse satellite DNA. However, only one of these sites, the central one, possesses kinetochores. This observation suggests either that satellite DNA alone is not sufficient for kinetochore formation or that when one kinetochore forms, other potential sites are suppressed. In the second set of experiments, we show that highly extended chromosomes from Hoechst 33258-treated cells (Hilwig, I., and A. Gropp, 1973, Exp. Cell Res., 81:474-477) lack kinetochores. Kinetochores are not seen in Miller spreads of these chromosomes, and at least one kinetochore antigen is not associated with these chromosomes when they were subjected to immunofluorescent analysis using anti-kinetochore scleroderma serum. These data suggest that kinetochore formation at centromeric heterochromatin may require a higher order chromatin structure which is altered by Hoechst binding. Finally, when metaphase chromosomes are subjected to digestion by restriction enzymes that degrade the bulk of mouse satellite DNA, contact between sister chromatids appears to be disrupted. Electron microscopy of digested chromosomes shows that there is a significant loss of heterochromatin between the sister chromatids at paired sites. In addition, fluorescence microscopy using anti-kinetochore serum reveals a greater inter-kinetochore distance than in controls or chromosomes digested with enzymes that spare satellite. We conclude that the presence of mouse satellite DNA in these regions is necessary for maintenance of contact between the sister chromatids of mouse mitotic chromosomes.

scholarly journals Aurora A kinase phosphorylates Hec1 to regulate metaphase kinetochore–microtubule dynamics

2017 ◽  
Vol 217 (1) ◽  
pp. 163-177 ◽  
Author(s):  
Keith F. DeLuca ◽  
Amanda Meppelink ◽  
Amanda J. Broad ◽  
Jeanne E. Mick ◽  
Olve B. Peersen ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Microtubule Dynamics ◽  
Aurora B ◽  
Aurora A Kinase ◽  
Aurora A ◽  
Tail Domain ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Mitotic Kinases ◽  
Microtubule Attachment

Precise regulation of kinetochore–microtubule attachments is essential for successful chromosome segregation. Central to this regulation is Aurora B kinase, which phosphorylates kinetochore substrates to promote microtubule turnover. A critical target of Aurora B is the N-terminal “tail” domain of Hec1, which is a component of the NDC80 complex, a force-transducing link between kinetochores and microtubules. Although Aurora B is regarded as the “master regulator” of kinetochore–microtubule attachment, other mitotic kinases likely contribute to Hec1 phosphorylation. In this study, we demonstrate that Aurora A kinase regulates kinetochore–microtubule dynamics of metaphase chromosomes, and we identify Hec1 S69, a previously uncharacterized phosphorylation target site in the Hec1 tail, as a critical Aurora A substrate for this regulation. Additionally, we demonstrate that Aurora A kinase associates with inner centromere protein (INCENP) during mitosis and that INCENP is competent to drive accumulation of the kinase to the centromere region of mitotic chromosomes. These findings reveal that both Aurora A and B contribute to kinetochore–microtubule attachment dynamics, and they uncover an unexpected role for Aurora A in late mitosis.

scholarly journals Chromosome disentanglement driven via optimal compaction of loop-extruded brush structures

2019 ◽  
Author(s):  
Sumitabha Brahmachari ◽  
John F. Marko
Keyword(s):  
Expression Patterns ◽  
Polymer Brush ◽  
Chromosome Size ◽  
Mitotic Chromosomes ◽  
Mechanical Stiffness ◽  
Structural Reorganization ◽  
Metaphase Chromosomes ◽  
Topo Ii ◽  
Strand Passage

AbstractEukaryote cell division features a chromosome compaction-decompaction cycle that is synchronized with their physical and topological segregation. It has been proposed that lengthwise compaction of chromatin into mitotic chromosomes via loop extrusion underlies the compaction-segregation/resolution process. We analyze this disentanglement scheme via considering the chromosome to be a succession of DNA/chromatin loops - a polymer “brush” - where active extrusion of loops controls the brush structure. Given topoisomerase (TopoII)-catalyzed topology fluctuations, we find that inter-chromosome entanglements are minimized for a certain “optimal” loop that scales with the chromosome size. The optimal loop organization is in accord with experimental data across species, suggesting an important structural role of genomic loops in maintaining a less entangled genome. Application of the model to the interphase genome indicates that active loop extrusion can maintain a level of chromosome compaction with suppressed entanglements; the transition to the metaphase state requires higher lengthwise compaction, and drives complete topological segregation. Optimized genomic loops may provide a means for evolutionary propagation of gene-expression patterns while simultaneously maintaining a disentangled genome. We also find that compact metaphase chromosomes have a densely packed core along their cylindrical axes that explains their observed mechanical stiffness. Our model connects chromosome structural reorganization to topological resolution through the cell cycle, and highlights a mechanism of directing Topo-II mediated strand passage via loop extrusion driven lengthwise compaction.

Stochastic chromatin packing of 3D mitotic chromosomes revealed by coherent X-rays

2021 ◽  
Vol 118 (46) ◽  
pp. e2109921118
Author(s):  
Daeho Sung ◽  
Chan Lim ◽  
Masatoshi Takagi ◽  
Chulho Jung ◽  
Heemin Lee ◽  
...  
Keyword(s):  
Information Transfer ◽  
3D Structure ◽  
Three Dimensional ◽  
Information Storage ◽  
Atomic Scale ◽  
Scaling Analysis ◽  
X Rays ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Chromatin Packing

DNA molecules are atomic-scale information storage molecules that promote reliable information transfer via fault-free repetitions of replications and transcriptions. Remarkable accuracy of compacting a few-meters-long DNA into a micrometer-scale object, and the reverse, makes the chromosome one of the most intriguing structures from both physical and biological viewpoints. However, its three-dimensional (3D) structure remains elusive with challenges in observing native structures of specimens at tens-of-nanometers resolution. Here, using cryogenic coherent X-ray diffraction imaging, we succeeded in obtaining nanoscale 3D structures of metaphase chromosomes that exhibited a random distribution of electron density without characteristics of high-order folding structures. Scaling analysis of the chromosomes, compared with a model structure having the same density profile as the experimental results, has discovered the fractal nature of density distributions. Quantitative 3D density maps, corroborated by molecular dynamics simulations, reveal that internal structures of chromosomes conform to diffusion-limited aggregation behavior, which indicates that 3D chromatin packing occurs via stochastic processes.

scholarly journals BrdUrd labeling of S-phase cells in testes and small intestine of mice, using microwave irradiation for immunogold-silver staining: an immunocytochemical study.

1990 ◽  
Vol 38 (2) ◽  
pp. 267-273 ◽  
Author(s):  
B Thoolen
Keyword(s):  
Small Intestine ◽  
Microwave Irradiation ◽  
Silver Staining ◽  
Leydig Cells ◽  
Protein A ◽  
S Phase ◽  
Immunocytochemical Study ◽  
Gold Solution ◽  
Proliferating Cells ◽  
Crypt Cells

In this study, BrdUrd labeling of S-phase cells in the small intestine and testes was accomplished using microwave irradiation. In this way crypt cells, spermatogonia, and Leydig cells could be labeled using removable plastic-embedded sections and immunogold-silver staining (IGSS). By using short periods of microwave irradiation for incubation of the monoclonal antibodies and the protein A-colloidal gold solution, the detection of BrdUrd-labeled cells could be remarkably enhanced. A comparative study of BrdUrd labeled spermatogonia in the testis of a Cpb-N mouse that received both [3H]-thymidine and BrdUrd proved that 90% of the BrdUrd-labeled cells also showed [3H]-thymidine labeling. The radioactive [3H]-thymidine labeling was a time-consuming method of 4 weeks' duration, whereas the BrdUrd-labeled cells could be labeled, fixed, enhanced, and counterstained in less than 3 hr. This investigation proves that BrdUrd labeling of S-phase cells can be a reliable, reproductive, rapid, and non-radioactive alternative method for [3H]-thymidine labeling of proliferating cells.

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