scholarly journals Interphase cohesin regulation ensures mitotic fidelity after genome reduplication

2019 ◽  
Vol 30 (2) ◽  
pp. 219-227 ◽  
Author(s):  
Benjamin M. Stormo ◽  
Donald T. Fox
Keyword(s):  
Mitotic Chromosome ◽  
Chromosome Structure ◽  
Distinct Form ◽  
Structural Alterations ◽  
Chromosome Duplication ◽  
Naturally Occurring ◽  
A Cell ◽  
Chromosome Separation ◽  
Separation Failure ◽  
Mitotic Cells

To ensure faithful genome propagation, mitotic cells alternate one round of chromosome duplication with one round of chromosome separation. Chromosome separation failure thus causes genome reduplication, which alters mitotic chromosome structure. Such structural alterations are well documented to impair mitotic fidelity following aberrant genome reduplication, including in diseased states. In contrast, we recently showed that naturally occurring genome reduplication does not alter mitotic chromosome structure in Drosophila papillar cells. Our discovery raised the question of how a cell undergoing genome reduplication might regulate chromosome structure to prevent mitotic errors. Here, we show that papillar cells ensure mitotic fidelity through interphase cohesin regulation. We demonstrate a requirement for cohesins during programmed rounds of papillar genome reduplication known as endocycles. This interphase cohesin regulation relies on cohesin release but not cohesin cleavage and depends on the conserved cohesin regulator Pds5 . Our data suggest that a distinct form of interphase cohesin regulation ensures mitotic fidelity after genome reduplication.

Spindle scaling mechanisms

2020 ◽  
Vol 64 (2) ◽  
pp. 383-396
Author(s):  
Lara K. Krüger ◽  
Phong T. Tran
Keyword(s):  
Cell Size ◽  
Spindle Assembly ◽  
Dependent Manner ◽  
Post Translational Modification ◽  
Size Dependent ◽  
A Cell ◽  
Chromosome Separation ◽  
Spindle Elongation ◽  
Protein Gradients ◽  
Spindle Structure

Abstract The mitotic spindle robustly scales with cell size in a plethora of different organisms. During development and throughout evolution, the spindle adjusts to cell size in metazoans and yeast in order to ensure faithful chromosome separation. Spindle adjustment to cell size occurs by the scaling of spindle length, spindle shape and the velocity of spindle assembly and elongation. Different mechanisms, depending on spindle structure and organism, account for these scaling relationships. The limited availability of critical spindle components, protein gradients, sequestration of spindle components, or post-translational modification and differential expression levels have been implicated in the regulation of spindle length and the spindle assembly/elongation velocity in a cell size-dependent manner. In this review, we will discuss the phenomenon and mechanisms of spindle length, spindle shape and spindle elongation velocity scaling with cell size.

Does early enucleation affect the decussation pattern of alpha cells in the ferret?

1994 ◽  
Vol 11 (3) ◽  
pp. 447-454 ◽  
Author(s):  
Benjamin E. Reese ◽  
Janal L. Urich
Keyword(s):  
Cell Death ◽  
Ganglion Cells ◽  
Alpha Cell ◽  
Alpha Cells ◽  
Naturally Occurring ◽  
Cell Class ◽  
Selective Elimination ◽  
A Cell ◽  
Decussation Pattern ◽  
Binocular Competition

AbstractNaturally occurring cell death has been hypothesized to sculpt various features of the organization of the mature visual pathways, including the recent proposal that the selective elimination of ganglion cells in the temporal retina shapes the formation of decussation patterns. Through a class-specific interocular competition, ganglion cells in the two temporal hemiretinae are selectively lost to produce the decussation patterns characteristic of each individual cell class (Leventhal et al., 1988). The present study has tested this hypothesis by asking whether the removal of one retina in newborn ferrets, which should disrupt binocular interactions at the level of the terminals, alters the decussation pattern of the alpha cells, a cell class that is entirely decussating in the normal adult ferret. Enucleation on the day of birth was found to increase the uncrossed projection by ≈50%, but not a single uncrossed alpha cell was found in the temporal retina. Either alpha cells never project ipsilaterally during development, or if they do, they cannot be rescued by early enucleation. While naturally occurring cell death plays many roles during development, creating the decussation pattern of the ferreth's alpha cell class via a binocular competition at the level of the targets is unlikely to be one of them.

Polytene and mitotic chromosome analysis in Ceratitis capitata (Diptera; Tephritidae)

1986 ◽  
Vol 28 (2) ◽  
pp. 180-188 ◽  
Author(s):  
D. G. Bedo
Keyword(s):  
X Chromosome ◽  
Silver Staining ◽  
Mitotic Chromosome ◽  
Ceratitis Capitata ◽  
Fat Body ◽  
Polytene Chromosomes ◽  
Chromosome Analysis ◽  
Mitotic Chromosomes ◽  
Chromosome Separation ◽  
Ectopic Pairing

Polytene chromosomes were found in several larval and pupal tissues of the Medfly, Ceratitis capitata, during a search for chromosomes suitable for detailed cytological analysis. Well-banded highly polytene chromosomes, which could be adequately separated and spread, were found in trichogen cells of the spatulate superior orbital bristles of male pupae. These chromosomes proved suitable for full polytene analysis. Thoracic trichogen cells of both male and female pupae also contain useful polytene chromosomes, although they are considerably thinner and thus more difficult to analyze. Contrasting with those in pupal trichogen cells, the chromosomes in the salivary glands, Malphighian tubules, midgut, hindgut, and fat body of larvae and pupae were difficult to prepare because of high levels of ectopic pairing and chromosome fragmentation. In hindgut preparations partial separation of up to three chromosomes was achieved, but in all other tissues no useful chromosome separation was possible. In trichogen polytene cells, five banded chromosomes and a prominent heterochromatic network associated with a nucleolus are found. The mitotic chromosomes respond to C- and Q-banding and silver staining with considerable variation. This is especially so in the X chromosome, which displays an extensive array of bands following both Q-banding and silver staining. Comparison of Q-banded metaphase and polytene chromosomes demonstrates that the five autosomes are represented by conventional polytene chromosomes, while the sex chromosomes are contained in the heterochromatic net, most of which fluoresces strongly. This suggests that the Q-bands of the mitotic X chromosome are replicated to a greater extent than the nonfluorescent material in polytene cells. This investigation shows C. capitata to have excellent cytological material for both polytene and mitotic analysis.Key words: Ceratitis capitata, Medfly, chromosomes (polytene), banding (chromosome).

scholarly journals Condensed Mitotic Chromosome Structure at Nanometer Resolution Using PALM and EGFP- Histones

PLoS ONE ◽  
2010 ◽  
Vol 5 (9) ◽  
pp. e12768 ◽  
Author(s):  
Atsushi Matsuda ◽  
Lin Shao ◽  
Jerome Boulanger ◽  
Charles Kervrann ◽  
Peter M. Carlton ◽  
...  
Keyword(s):  
Mitotic Chromosome ◽  
Chromosome Structure ◽  
Nanometer Resolution

scholarly journals Cryo-Fracture or Freeze-Fracture, a Method to Expose Internal Tissue Surfaces and Cell Surfaces for Viewing in the Scanning Electron Microscope

2008 ◽  
Vol 16 (4) ◽  
pp. 56-59 ◽  
Author(s):  
Jeannette Taylor
Keyword(s):  
Membrane Surface ◽  
Freeze Fracture ◽  
Internal Tissue ◽  
Cell Surfaces ◽  
Naturally Occurring ◽  
Critical Point Drying ◽  
Tissue Surfaces ◽  
A Cell ◽  
Bowman's Capsule ◽  
Scanning Electron

Cryo-fracture, in conjunction with critical point drying is a method used to prepare biological samples in order to expose, for viewing via scanning electron microscopy, those naturally occurring surfaces which might otherwise remain obscure. For example, the Bowman’s capsule and tubules of a kidney, tiny blood vessels on any organ, inter-cellular spaces in liver or alveoli in the lungs. Also, some surfaces, not normally exposed at all such as the membrane surface of a nuclear envelope, mitochondria or chloroplasts or the cytoplasm of a cell, can be brought to light with this method. Herein is a review of the development of cryo-fracture and how it is currently used at our facility.

scholarly journals CDK1-mediated phosphorylation at H2B serine 6 is required for mitotic chromosome segregation

2019 ◽  
Vol 218 (4) ◽  
pp. 1164-1181 ◽  
Author(s):  
Markus Seibert ◽  
Marcus Krüger ◽  
Nikolaus A. Watson ◽  
Onur Sen ◽  
John R. Daum ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Chromosomal Instability ◽  
Mitotic Chromosome ◽  
Chromatin Modification ◽  
Genomic Stability ◽  
Cyclin B1 ◽  
Aurora B ◽  
Chromatin Binding ◽  
Histone H2b ◽  
Chromosome Separation

Faithful mitotic chromosome segregation is required for the maintenance of genomic stability. We discovered the phosphorylation of histone H2B at serine 6 (H2B S6ph) as a new chromatin modification site and found that this modification occurs during the early mitotic phases at inner centromeres and pericentromeric heterochromatin. This modification is directly mediated by cyclin B1–associated CDK1, and indirectly by Aurora B, and is antagonized by PP1-mediated dephosphorylation. H2B S6ph impairs chromatin binding of the histone chaperone SET (I2PP2A), which is important for mitotic fidelity. Injection of phosphorylation-specific H2B S6 antibodies in mitotic cells caused anaphase defects with impaired chromosome segregation and incomplete cytokinesis. As H2B S6ph is important for faithful chromosome separation, this modification may contribute to the prevention chromosomal instability and aneuploidy which frequently occur in cancer cells.

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