scholarly journals Interpolar spindle microtubules in PTK cells.

1993 ◽  
Vol 123 (6) ◽  
pp. 1475-1489 ◽  
Author(s):  
D N Mastronarde ◽  
K L McDonald ◽  
R Ding ◽  
J R McIntosh
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Specific Interaction ◽  
Spindle Pole ◽  
Serial Sections ◽  
Spindle Poles ◽  
Late Anaphase ◽  
Computer Image Processing ◽  
Spindle Microtubules ◽  
Anaphase B

Spindle microtubules (MTs) in PtK1 cells, fixed at stages from metaphase to telophase, have been reconstructed using serial sections, electron microscopy, and computer image processing. We have studied the class of MTs that form an interdigitating system connecting the two spindle poles (interpolar MTs or ipMTs) and their relationship to the spindle MTs that attach to kinetochores (kMTs). Viewed in cross section, the ipMTs cluster with antiparallel near neighbors throughout mitosis; this bundling becomes much more pronounced as anaphase proceeds. While the minus ends of most kMTs are near the poles, those of the ipMTs are spread over half of the spindle length, with at least 50% lying > 1.5 microns from the poles. Longitudinal views of the ipMT bundles demonstrate a major rearrangement of their plus ends between mid- and late anaphase B. However, the minus ends of these MTs do not move appreciably farther from the spindle midplane, suggesting that sliding of these MTs contributes little to anaphase B. The minus ends of ipMTs are markedly clustered in the bundles of kMTs throughout anaphase A. These ends lie close to kMTs much more frequently than would be expected by chance, suggesting a specific interaction. As sister kinetochores separate and kMTs shorten, the minus ends of the kMTs remain associated with the spindle poles, but the minus ends of many ipMTs are released from the kMT bundles, allowing the spindle pole and the kMTs to move away from the ipMTs as the spindle elongates.

scholarly journals Analysis of the distribution of spindle microtubules in the diatom Fragilaria.

1978 ◽  
Vol 79 (3) ◽  
pp. 737-763 ◽  
Author(s):  
D H Tippit ◽  
D Schulz ◽  
J D Pickett-Heaps
Keyword(s):  
Spatial Arrangement ◽  
Spindle Pole ◽  
Serial Sections ◽  
Late Prophase ◽  
Central Spindle ◽  
Sources Of Error ◽  
Late Anaphase ◽  
Spindle Microtubules ◽  
Spindle Elongation ◽  
Intercellular Variability

The spindle of the colonial diatom Fragilaria contains two distinct sets of spindle microtubules (MTs): (a) MTs comprising the central spindle, which is composed of two half-spindles interdigitated to form a region of "overlap"; (b) MTs which radiate laterally from the poles. The central spindles from 28 cells are reconstructed by tracking each MT of the central spindle through consecutive serial sections. Because the colonies of Fragilaria are flat ribbons of contiguous cells (clones), it is possible, by using single ribbons of cells, to compare reconstructed spindles at different mitotic stages with minimal intercellular variability. From these reconstructions we have determined: (a) the changes in distribution of MTs along the spindle during mitosis; (b) the change in the total number of MTs during mitosis; (c) the length of each MT (measured by the number of sections each traverses) at different mitotic stages; (d) the frequency of different classes of MTs (i.e., free, continuous, etc.); (e) the spatial arrangement of MTs from opposite poles in the overlap; (f) the approximate number of MTs, separate from the central spindle, which radiate from each spindle pole. From longitudinal sections of the central spindle, the lengths of the whole spindle, half-spindle, and overlap were measured from 80 cells at different mitotic stages. Numerous sources of error may create inaccuracies in these measurements; these problems are discussed. The central spindle at prophase consists predominantly of continuous MTs (pole to pole). Between late prophase and prometaphase, spindle length increases, and the spindle is transformed into two half-spindles (mainly polar MTs) interdigitated to form the overlap. At late anaphase-telophase, the overlap decreases concurrent with spindle elongation. Our interpretation is that the MTs of the central spindle slide past one another at both late prophase and late anaphase. These changes in MT distribution have the effect of elongating the spindle and are not involved in the poleward movement of the chromosomes. Some aspects of tracking spindle MTs, the interaction of MTs in the overlap, formation of the prophase spindle, and our interpretation of rearrangements of MTs, are discussed.

scholarly journals ULTRASTRUCTURE AND TIME COURSE OF MITOSIS IN THE FUNGUS FUSARIUM OXYSPORUM

1972 ◽  
Vol 55 (2) ◽  
pp. 368-389 ◽  
Author(s):  
James R. Aist ◽  
P. H. Williams
Keyword(s):  
Electron Microscopy ◽  
Fusarium Oxysporum ◽  
Time Course ◽  
Light And Electron Microscopy ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Metaphase Chromosomes ◽  
Mitotic Apparatus ◽  
Spindle Poles ◽  
Spindle Microtubules

Mitosis in Fusarium oxysporum Schlect. was studied by light and electron microscopy. The average times required for the stages of mitosis, as determined from measurements made on living nuclei, were as follows: prophase, 70 sec; metaphase, 120 sec; anaphase, 13 sec; and telophase, 125 sec, for a total of 5.5 min. New postfixation procedures were developed specifically to preserve the fine-structure of the mitotic apparatus. Electron microscopy of mitotic nuclei revealed a fibrillo-granular, extranuclear Spindle Pole Body (SPB) at each pole of the intranuclear, microtubular spindles. Metaphase chromosomes were attached to spindle microtubules via kinetochores, which were found near the spindle poles at telophase. The still-intact, original nuclear envelope constricted around the incipient daughter nuclei during telophase.

scholarly journals Nsk1 ensures accurate chromosome segregation by promoting association of kinetochores to spindle poles during anaphase B

2011 ◽  
Vol 22 (23) ◽  
pp. 4486-4502 ◽  
Author(s):  
Graham J. Buttrick ◽  
John C. Meadows ◽  
Theresa C. Lancaster ◽  
Vincent Vanoosthuyse ◽  
Lindsey A. Shepperd ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
Growth Defect ◽  
Catalytic Subunits ◽  
Spindle Poles ◽  
Sister Chromatids ◽  
Anaphase B ◽  
Novel Protein

Type 1 phosphatase (PP1) antagonizes Aurora B kinase to stabilize kinetochore–microtubule attachments and to silence the spindle checkpoint. We screened for factors that exacerbate the growth defect of Δdis2 cells, which lack one of two catalytic subunits of PP1 in fission yeast, and identified Nsk1, a novel protein required for accurate chromosome segregation. During interphase, Nsk1 resides in the nucleolus but spreads throughout the nucleoplasm as cells enter mitosis. Following dephosphorylation by Clp1 (Cdc14-like) phosphatase and at least one other phosphatase, Nsk1 localizes to the interface between kinetochores and the inner face of the spindle pole body during anaphase. In the absence of Nsk1, some kinetochores become detached from spindle poles during anaphase B. If this occurs late in anaphase B, then the sister chromatids of unclustered kinetochores segregate to the correct daughter cell. These unclustered kinetochores are efficiently captured, retrieved, bioriented, and segregated during the following mitosis, as long as Dis2 is present. However, if kinetochores are detached from a spindle pole early in anaphase B, then these sister chromatids become missegregated. These data suggest Nsk1 ensures accurate chromosome segregation by promoting the tethering of kinetochores to spindle poles during anaphase B.

scholarly journals Central-spindle microtubules are strongly coupled to chromosomes during both anaphase A and anaphase B

2019 ◽  
Vol 30 (19) ◽  
pp. 2503-2514 ◽  
Author(s):  
Che-Hang Yu ◽  
Stefanie Redemann ◽  
Hai-Yin Wu ◽  
Robert Kiewisz ◽  
Tae Yeon Yoo ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Tomographic Reconstruction ◽  
Mitotic Spindles ◽  
Strongly Coupled ◽  
Central Spindle ◽  
Spindle Poles ◽  
Meiotic Spindles ◽  
Spindle Microtubules ◽  
Anaphase B ◽  
Chromosome Motion

Spindle microtubules, whose dynamics vary over time and at different locations, cooperatively drive chromosome segregation. Measurements of microtubule dynamics and spindle ultrastructure can provide insight into the behaviors of microtubules, helping elucidate the mechanism of chromosome segregation. Much work has focused on the dynamics and organization of kinetochore microtubules, that is, on the region between chromosomes and poles. In comparison, microtubules in the central-spindle region, between segregating chromosomes, have been less thoroughly characterized. Here, we report measurements of the movement of central-spindle microtubules during chromosome segregation in human mitotic spindles and Caenorhabditis elegans mitotic and female meiotic spindles. We found that these central-spindle microtubules slide apart at the same speed as chromosomes, even as chromosomes move toward spindle poles. In these systems, damaging central-spindle microtubules by laser ablation caused an immediate and complete cessation of chromosome motion, suggesting a strong coupling between central-spindle microtubules and chromosomes. Electron tomographic reconstruction revealed that the analyzed anaphase spindles all contain microtubules with both ends between segregating chromosomes. Our results provide new dynamical, functional, and ultrastructural characterizations of central-spindle microtubules during chromosome segregation in diverse spindles and suggest that central-spindle microtubules and chromosomes are strongly coupled in anaphase.

scholarly journals Aster-free spindle poles in insect spermatocytes: evidence for chromosome-induced spindle formation?

1986 ◽  
Vol 102 (5) ◽  
pp. 1679-1687 ◽  
Author(s):  
W Steffen ◽  
H Fuge ◽  
R Dietz ◽  
M Bastmeyer ◽  
G Müller
Keyword(s):  
Spindle Pole ◽  
Serial Sections ◽  
Spindle Formation ◽  
Microtubule Polymerization ◽  
Spindle Poles ◽  
Pericentriolar Material ◽  
Lysis Buffer ◽  
Bipolar Spindles

Tipulid spermatocytes form normally functioning bipolar spindles after one of the centrosomes is experimentally dislocated from the nucleus in late diakinesis (Dietz, R., 1959, Z. Naturforsch., 14b:749-752; Dietz, R., 1963, Zool. Anz. Suppl., 23:131-138; Dietz, R., 1966, Heredity, 19:161-166). The possibility that dissociated pericentriolar material (PCM) is nevertheless responsible for the formation of the spindle in these cells cannot be ruled out based on live observation. In studying serial sections of complete cells and of lysed cells, it was found that centrosome-free spindle poles in the crane fly show neither pericentriolar-like material nor aster microtubules, whereas the displaced centrosomes appear complete, i.e., consist of a centriole pair, aster microtubules, and PCM. Exposure to a lysis buffer containing tubulin resulted in an increase of centrosomal asters due to aster microtubule polymerization. Aster-free spindle poles did not show any reaction, also indicating the absence of PCM at these poles. The results favor the hypothesis of chromosome-induced spindle pole formation at the onset of prometaphase and the dispensability of PCM in Pales.

scholarly journals Central spindle microtubules are strongly coupled to chromosomes during both anaphase A and anaphase B

2019 ◽  
Author(s):  
Che-Hang Yu ◽  
Stefanie Redemann ◽  
Hai-Yin Wu ◽  
Robert Kiewisz ◽  
Tae Yeon Yoo ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Tomographic Reconstruction ◽  
Mitotic Spindles ◽  
Strongly Coupled ◽  
Central Spindle ◽  
Spindle Poles ◽  
Meiotic Spindles ◽  
Spindle Microtubules ◽  
Anaphase B ◽  
Chromosome Motion

AbstractSpindle microtubules, whose dynamics vary over time and at different locations, cooperatively drive chromosome segregation. Measurements of microtubule dynamics and spindle ultrastructure can provide insight into the behaviors of microtubules, helping elucidate the mechanism of chromosome segregation. Much work has focused on the dynamics and organization of kinetochore microtubules, i.e. on the region between chromosomes and poles. In comparison, microtubules in the central spindle region, between segregating chromosomes, have been less thoroughly characterized. Here, we report measurements of the movement of central spindle microtubules during chromosome segregation in human mitotic spindles, and Caenorhabditis elegans mitotic and female meiotic spindles. We found that these central spindle microtubules slide apart at the same speed as chromosomes, even as chromosomes move towards spindle poles. In these systems, damaging central spindle microtubules by laser ablation caused an immediate and complete cessation of chromosome motion, suggesting a strong coupling between central spindle microtubules and chromosomes. Electron tomographic reconstruction revealed that the analyzed anaphase spindles all contain microtubules with both ends between segregating chromosomes. Our results provide new dynamical, functional, and ultrastructural characterizations of central spindle microtubules during chromosome segregation in diverse spindles, and suggest that central spindle microtubules and chromosomes are strongly coupled in anaphase.

A requirement for the Abnormal Spindle protein to organise microtubules of the central spindle for cytokinesis inDrosophila

2002 ◽  
Vol 115 (5) ◽  
pp. 913-922 ◽  
Author(s):  
Maria Giovanna Riparbelli ◽  
Giuliano Callaini ◽  
David M. Glover ◽  
Maria do Carmo Avides
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Male Meiosis ◽  
Wild Type ◽  
Female Meiosis ◽  
Central Spindle ◽  
Spindle Poles ◽  
Late Anaphase ◽  
Mutant Cells ◽  
Sperm Aster

Drosophila abnormal spindle (asp) mutants exhibit a mitotic metaphase checkpoint arrest with abnormal spindle poles, which reflects a requirement for Asp for the integrity of microtubule organising centres (MTOCs). In male meiosis, the absence of a strong spindle integrity checkpoint enables asp mutant cells to proceed through anaphase and telophase. However, the central spindle region is not correctly organised and cells frequently fail to complete cytokinesis. This contrasts with meiosis in wild-type males where at late anaphase a dense array of microtubules forms in the central spindle region that has Asp localised at its border. We speculate that Asp is associated with the minus ends of microtubules that have been released from the spindle poles to form the central spindle. A parallel situation arises in female meiosis where Asp not only associates with the minus ends of microtubules at the acentriolar poles but also with the central spindle pole body that forms between the two tandem spindles of meiosis II. Upon fertilisation, Asp is also recruited to the MTOC that nucleates the sperm aster. Asp is required for growth of the microtubules of the sperm aster,which in asp mutants remains diminutive and so prevents migration of the pronuclei.

scholarly journals Chromosomal attachments set length and microtubule number in the Saccharomyces cerevisiae mitotic spindle

2014 ◽  
Vol 25 (25) ◽  
pp. 4034-4048 ◽  
Author(s):  
Natalie J. Nannas ◽  
Eileen T. O’Toole ◽  
Mark Winey ◽  
Andrew W. Murray
Keyword(s):  
Electron Microscopy ◽  
Saccharomyces Cerevisiae ◽  
Simple Model ◽  
Mitotic Spindle ◽  
Cell Types ◽  
Yeast Saccharomyces Cerevisiae ◽  
Spindle Poles ◽  
Length Regulation ◽  
Spindle Microtubules ◽  
Different Cell Types

The length of the mitotic spindle varies among different cell types. A simple model for spindle length regulation requires balancing two forces: pulling, due to micro­tubules that attach to the chromosomes at their kinetochores, and pushing, due to interactions between microtubules that emanate from opposite spindle poles. In the budding yeast Saccharomyces cerevisiae, we show that spindle length scales with kinetochore number, increasing when kinetochores are inactivated and shortening on addition of synthetic or natural kinetochores, showing that kinetochore–microtubule interactions generate an inward force to balance forces that elongate the spindle. Electron microscopy shows that manipulating kinetochore number alters the number of spindle microtubules: adding extra kinetochores increases the number of spindle microtubules, suggesting kinetochore-based regulation of microtubule number.

scholarly journals THE DISTRIBUTION OF SPINDLE MICROTUBULES DURING MITOSIS IN CULTURED HUMAN CELLS

1971 ◽  
Vol 49 (2) ◽  
pp. 468-497 ◽  
Author(s):  
J. Richard McIntosh ◽  
Story C. Landis
Keyword(s):  
Electron Microscopy ◽  
Hela Cells ◽  
Metaphase Plate ◽  
Human Cells ◽  
Late Anaphase ◽  
Monolayer Cultures ◽  
Spindle Axis ◽  
Early Anaphase ◽  
Cultured Human Cells ◽  
Spindle Microtubules

WI-38 and HeLa cells in mitosis have been selected from fixed monolayer cultures and serially sectioned for electron microscopy. Sections perpendicular to the spindle axis permit counting of the number of microtubules at each position on the spindle axis and hence the preparation of tubule distribution profiles. Errors intrinsic to this method are discussed. The changes in the tubule distributions from one mitotic stage to another provide evidence concerning the behavior of the spindle tubules during mitosis. The ratio of the number of tubules passing the chromosomes on the metaphase plate to the maximum number in each half spindle is about 1/2. This ratio changes little in early anaphase, and then decreases in late anaphase at about the same time that a zone of increased tubule number develops at the middle of the interzone. The region where the stem bodies form contains about 3/2 the number of tubules seen elsewhere in the interzone. This ratio is almost constant as the mid-body forms in telophase and then increases to 2/1 in early interphase before the final stages of cytokinesis occur.

scholarly journals Three-dimensional analysis and ultrastructural design of mitotic spindles from the cdc20 mutant of Saccharomyces cerevisiae.

1997 ◽  
Vol 8 (1) ◽  
pp. 1-11 ◽  
Author(s):  
E T O'Toole ◽  
D N Mastronarde ◽  
T H Giddings ◽  
M Winey ◽  
D J Burke ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Specific Interaction ◽  
Three Dimensional ◽  
Spindle Pole ◽  
Opposite Polarity ◽  
Computer Assisted ◽  
Wild Type ◽  
Spindle Microtubule ◽  
In The Wild ◽  
Spindle Microtubules

The three-dimensional organization of mitotic microtubules in a mutant strain of Saccharomyces cerevisiae has been studied by computer-assisted serial reconstruction. At the nonpermissive temperature, cdc20 cells arrested with a spindle length of approximately 2.5 microns. These spindles contained a mean of 81 microtubules (range, 56-100) compared with 23 in wild-type spindles of comparable length. This increase in spindle microtubule number resulted in a total polymer length up to four times that of wild-type spindles. The spindle pole bodies in the cdc20 cells were approximately 2.3 times the size of wild-type, thereby accommodating the abnormally large number of spindle microtubules. The cdc20 spindles contained a large number of interpolar microtubules organized in a "core bundle." A neighbor density analysis of this bundle at the spindle midzone showed a preferred spacing of approximately 35 nm center-to-center between microtubules of opposite polarity. Although this is evidence of specific interaction between antiparallel microtubules, mutant spindles were less ordered than the spindle of wild-type cells. The number of noncore microtubules was significantly higher than that reported for wild-type, and these microtubules did not display a characteristic metaphase configuration. cdc20 spindles showed significantly more cross-bridges between spindle microtubules than were seen in the wild type. The cross-bridge density was highest between antiparallel microtubules. These data suggest that spindle microtubules are stabilized in cdc20 cells and that the CDC20 gene product may be involved in cell cycle processes that promote spindle microtubule disassembly.

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