scholarly journals Astral and spindle forces in PtK2 cells during anaphase B: a laser microbeam study

1993 ◽  
Vol 104 (4) ◽  
pp. 1207-1216 ◽  
Author(s):  
J.R. Aist ◽  
H. Liang ◽  
M.W. Berns
Keyword(s):  
Spindle Pole ◽  
Uv Laser ◽  
Central Spindle ◽  
Laser Microbeam ◽  
Spindle Poles ◽  
Pulling Forces ◽  
Early Anaphase ◽  
Anaphase B

Rat kangaroo kidney epithelium (PtK2) cells develop prominent asters and spindles during anaphase B of mitosis. It has been shown that severing the spindle at early anaphase B in living PtK1 cells results in a dramatic increase in the rate of pole-pole separation. This result suggested that the asters pull on the spindle poles, putting tension on the spindle, while the spindle acts as a governor, limiting the rate of pole separation. To further test these inferences, we used a UV-laser microbeam to damage one of the two asters in living PtK2 cells at early anaphase B and monitored the effects on individual spindle pole movements, pole-pole separation rates and astral microtubules (MTs). Irradiation at the estimated position of a centrosome greatly reduced its array of astral MTs and nearly stopped the movement of the irradiated pole, whereas the sister pole retained its normal array of astral MTs and actually accelerated. Control irradiations, either close to the estimated position of the centrosome or beside the spindle at the equator, had little or no effect on either spindle pole movements or astral MTs. These results support the inferences that during anaphase B in living PtK cells, the central spindle is under tension generated by pulling forces in the asters (presumably MT-mediated) and that the spindle generates counterforces that limit the rate of pole separation. The results also suggest that the central spindle in living PtK cells may be able to generate a pushing force.

scholarly journals Evidence for anaphase pulling forces during C. elegans meiosis

2020 ◽  
Vol 219 (12) ◽  
Author(s):  
Brennan M. Danlasky ◽  
Michelle T. Panzica ◽  
Karen P. McNally ◽  
Elizabeth Vargas ◽  
Cynthia Bailey ◽  
...  
Keyword(s):  
Spindle Pole ◽  
Outer Face ◽  
Chromosome Movement ◽  
Female Meiosis ◽  
Homologous Chromosomes ◽  
C Elegans ◽  
Spindle Poles ◽  
Pulling Forces ◽  
Spindle Elongation ◽  
Anaphase B

Anaphase chromosome movement is thought to be mediated by pulling forces generated by end-on attachment of microtubules to the outer face of kinetochores. However, it has been suggested that during C. elegans female meiosis, anaphase is mediated by a kinetochore-independent pushing mechanism with microtubules only attached to the inner face of segregating chromosomes. We found that the kinetochore proteins KNL-1 and KNL-3 are required for preanaphase chromosome stretching, suggesting a role in pulling forces. In the absence of KNL-1,3, pairs of homologous chromosomes did not separate and did not move toward a spindle pole. Instead, each homolog pair moved together with the same spindle pole during anaphase B spindle elongation. Two masses of chromatin thus ended up at opposite spindle poles, giving the appearance of successful anaphase.

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 Sld5 Ensures Centrosomal Resistance to Congression Forces by Preserving Centriolar Satellites

2017 ◽  
Vol 38 (2) ◽  
Author(s):  
Manpreet Kaur ◽  
Raksha Devi ◽  
Tanushree Ghosh ◽  
Md Muntaz Khan ◽  
Praveen Kumar ◽  
...  
Keyword(s):  
Dna Replication ◽  
Unknown Function ◽  
Motor Protein ◽  
Spindle Pole ◽  
Replication Protein ◽  
Traction Forces ◽  
Centrosomal Protein ◽  
Spindle Poles ◽  
Chromosome Congression ◽  
Pulling Forces

ABSTRACT The migration of chromosomes during mitosis is mediated primarily by kinesins that bind to the chromosomes and move along the microtubules, exerting pulling and pushing forces on the centrosomes. We report that a DNA replication protein, Sld5, localizes to the centrosomes, resisting the microtubular pulling forces experienced during chromosome congression. In the absence of Sld5, centriolar satellites, which normally cluster around the centrosomes, are dissipated throughout the cytoplasm, resulting in the loss of their known function of recruiting the centrosomal protein, pericentrin. We observed that Sld5-deficient centrosomes lacking pericentrin were unable to endure the CENP-E- and Kid-mediated microtubular forces that converge on the centrosomes during chromosome congression, resulting in monocentriolar and acentriolar spindle poles. The minus-end-directed kinesin-14 motor protein, HSET, sustains the traction forces that mediate centrosomal fragmentation in Sld5-depleted cells. Thus, we report that a DNA replication protein has an as yet unknown function of ensuring spindle pole resistance to traction forces exerted during chromosome congression.

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.

Structure-function analysis of anaphase spindle elongation using isolated diatom spindles

1991 ◽  
Vol 49 ◽  
pp. 206-207
Author(s):  
W. Z. Cande ◽  
C.J. Hogan ◽  
M. Lee
Keyword(s):  
Morphological Changes ◽  
Function Analysis ◽  
Light And Electron Microscopy ◽  
Near Neighbor ◽  
Model Systems ◽  
Central Spindle ◽  
Spindle Poles ◽  
Spindle Elongation ◽  
Anaphase B

Diatom spindles are important model systems for describing the morphological changes associated with anaphase chromosome movement because the fibrous systems responsible for anaphase A (chromosome-to-pole movement) and anaphase B (spindle elongation) are spatially separate and the central spindle is a paracrystalline array of microtubules. The diatom central spindle, which is responsible for anaphase B, is constructed of two sets of interdigiting microtubules that originate from plate-like spindle poles and display specific near-neighbor interactions in the zone of microtubule overlap. The microtubules of each half-spindle are of relatively unifrom length such that the plus ends are clustered together in narrow zones at each edge of the zone of microtubule overlap. This has allowed us to monitor changes in extent of microtubule overlap in the light microscope with polarization optics. We have isolated spindles from synchronized populations of several species of dividing diatom cells to study the mechanochemistry of anaphase spindle elongation in vitro and to analyze the rearrangement of spindle components by light and electron microscopy during reactivation.

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.

Assembly and dynamics of an anastral:astral spindle: the meiosis II spindle of Drosophila oocytes

1998 ◽  
Vol 111 (17) ◽  
pp. 2487-2495 ◽  
Author(s):  
S.A. Endow ◽  
D.J. Komma
Keyword(s):  
De Novo ◽  
Spindle Pole Body ◽  
Spindle Pole ◽  
The Body ◽  
Central Spindle ◽  
Spindle Poles ◽  
Pole Body ◽  
Microtubule Motor ◽  
Gamma Tubulin ◽  
Meiosis I

The meiosis II spindle of Drosophila oocytes is distinctive in structure, consisting of two tandem spindles with anastral distal poles and an aster-associated spindle pole body between the central poles. Assembly of the anastral:astral meiosis II spindle occurs by reorganization of the meiosis I spindle, without breakdown of the meiosis I spindle. The unusual disk- or ring-shaped central spindle pole body forms de novo in the center of the elongated meiosis I spindle, followed by formation of the central spindle poles. gamma-Tubulin transiently localizes to the central spindle pole body, implying that the body acts as a microtubule nucleating center for assembly of the central poles. Localization of gamma-tubulin to the meiosis II spindle is dependent on the microtubule motor protein, Nonclaret disjunctional (Ncd). Absence of Ncd results in loss of gamma-tubulin localization to the spindle and destabilization of microtubules in the central region of the spindle. Assembly of the anastral:astral meiosis II spindle probably involves rapid reassortment of microtubule plus and minus ends in the center of the meiosis I spindle - this can be accounted for by a model that also accounts for the loss of gamma-tubulin localization to the spindle and destabilization of microtubules in the absence of Ncd.

A cytoplasmic dynein required for mitotic aster formation in vivo

1998 ◽  
Vol 111 (17) ◽  
pp. 2607-2614 ◽  
Author(s):  
S. Inoue ◽  
O.C. Yoder ◽  
B.G. Turgeon ◽  
J.R. Aist
Keyword(s):  
Spindle Pole Body ◽  
Cytoplasmic Dynein ◽  
Spindle Pole ◽  
Mitotic Spindles ◽  
Laser Microbeam ◽  
Filamentous Ascomycete ◽  
Spindle Elongation ◽  
Pulling Force ◽  
Anaphase B

An astral pulling force helps to elongate the mitotic spindle in the filamentous ascomycete, Nectria haematococca. Evidence is mounting that dynein is required for the formation of mitotic spindles and asters. Obviously, this would be an important mitotic function of dynein, since it would be a prerequisite for astral force to be applied to a spindle pole. Missing from the evidence for such a role of dynein in aster formation, however, has been a dynein mutant lacking mitotic asters. To determine whether or not cytoplasmic dynein is involved in mitotic aster formation in N. haematococca, a dynein-deficient mutant was made. Immunocytochemistry visualized few or no mitotic astral microtubules in the mutant cells, and studies of living cells confirmed the veracity of this result by revealing the absence of mitotic aster functions in vivo: intra-astral motility of membranous organelles was not apparent; the rate and extent of spindle elongation during anaphase B were reduced; and spindle pole body separation almost stopped when the anaphase B spindle in the mutant was cut by a laser microbeam, demonstrating unequivocally that no astral pulling force was present. These unique results not only provide a demonstration that cytoplasmic dynein is required for the formation of mitotic asters in N. haematococca; they also represent the first report of mitotic phenotypes in a dynein mutant of any filamentous fungus and the first cytoplasmic dynein mutant of any organism whose mitotic phenotypes demonstrate the requirement of cytoplasmic dynein for aster formation in vivo.

scholarly journals Kinetochore Fiber Maturation in PtK1 Cells and Its Implications for the Mechanisms of Chromosome Congression and Anaphase Onset

1997 ◽  
Vol 137 (7) ◽  
pp. 1567-1580 ◽  
Author(s):  
Bruce F. McEwen ◽  
Amy B. Heagle ◽  
Grisel O. Cassels ◽  
Karolyn F. Buttle ◽  
Conly L. Rieder
Keyword(s):  
Time Course ◽  
Spindle Pole ◽  
Metaphase Chromosomes ◽  
Spindle Poles ◽  
Anaphase Onset ◽  
Chromosome Congression ◽  
Early Anaphase ◽  
Full Complement ◽  
Spindle Microtubules ◽  
Chromosome Motion

Kinetochore microtubules (kMts) are a subset of spindle microtubules that bind directly to the kinetochore to form the kinetochore fiber (K-fiber). The K-fiber in turn interacts with the kinetochore to produce chromosome motion toward the attached spindle pole. We have examined K-fiber maturation in PtK1 cells using same-cell video light microscopy/serial section EM. During congression, the kinetochore moving away from its spindle pole (i.e., the trailing kinetochore) and its leading, poleward moving sister both have variable numbers of kMts, but the trailing kinetochore always has at least twice as many kMts as the leading kinetochore. A comparison of Mt numbers on sister kinetochores of congressing chromosomes with their direction of motion, as well as distance from their associated spindle poles, reveals that the direction of motion is not determined by kMt number or total kMt length. The same result was observed for oscillating metaphase chromosomes. These data demonstrate that the tendency of a kinetochore to move poleward is not positively correlated with the kMt number. At late prometaphase, the average number of Mts on fully congressed kinetochores is 19.7 ± 6.7 (n = 94), at late metaphase 24.3 ± 4.9 (n = 62), and at early anaphase 27.8 ± 6.3 (n = 65). Differences between these distributions are statistically significant. The increased kMt number during early anaphase, relative to late metaphase, reflects the increased kMt stability at anaphase onset. Treatment of late metaphase cells with 1 μM taxol inhibits anaphase onset, but produces the same kMt distribution as in early anaphase: 28.7 ± 7.4 (n = 54). Thus, a full complement of kMts is not sufficient to induce anaphase onset. We also measured the time course for kMt acquisition and determined an initial rate of 1.9 kMts/min. This rate accelerates up to 10-fold during the course of K-fiber maturation, suggesting an increased concentration of Mt plus ends in the vicinity of the kinetochore at late metaphase and/or cooperativity for kMt acquisition.

Sign in / Sign up

Export Citation Format

Share Document