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 A novel chromosome segregation mechanism during female meiosis

2016 ◽  
Vol 27 (16) ◽  
pp. 2576-2589 ◽  
Author(s):  
Karen Perry McNally ◽  
Michelle T. Panzica ◽  
Taekyung Kim ◽  
Daniel B. Cortes ◽  
Francis J. McNally
Keyword(s):  
Chromosome Segregation ◽  
Meiotic Chromosome ◽  
Spindle Pole ◽  
Chromosome Movement ◽  
Female Meiosis ◽  
Spindle Poles ◽  
Wide Range ◽  
Chromosome Separation ◽  
Meiotic Spindles ◽  
Anaphase B

In a wide range of eukaryotes, chromosome segregation occurs through anaphase A, in which chromosomes move toward stationary spindle poles, anaphase B, in which chromosomes move at the same velocity as outwardly moving spindle poles, or both. In contrast, Caenorhabditis elegans female meiotic spindles initially shorten in the pole-to-pole axis such that spindle poles contact the outer kinetochore before the start of anaphase chromosome separation. Once the spindle pole-to-kinetochore contact has been made, the homologues of a 4-μm-long bivalent begin to separate. The spindle shortens an additional 0.5 μm until the chromosomes are embedded in the spindle poles. Chromosomes then separate at the same velocity as the spindle poles in an anaphase B–like movement. We conclude that the majority of meiotic chromosome movement is caused by shortening of the spindle to bring poles in contact with the chromosomes, followed by separation of chromosome-bound poles by outward sliding.

scholarly journals Anaphase A: Melting Microtubules Move Chromosomes toward Spindle Poles

2017 ◽  
Author(s):  
Charles L. Asbury
Keyword(s):  
Fluorescence Microscopy ◽  
Mechanistic Models ◽  
Chromosome Movement ◽  
Load Bearing ◽  
Spindle Poles ◽  
Sister Chromatids ◽  
Spindle Elongation ◽  
Anaphase B ◽  
Chromosome Movements ◽  
Cellular Movement

The separation of sister chromatids during anaphase is the culmination of mitosis and one of the most strikingly beautiful examples of cellular movement. It consists of two distinct processes: Anaphase A, the movement of chromosomes toward spindle poles via shortening of the connecting fibers, and anaphase B, separation of the two poles from one another via spindle elongation. I focus here on anaphase A chromosome-to-pole movement. The chapter begins by summarizing classical observations of chromosome movements, which support the current understanding of anaphase mechanisms. Live cell fluorescence microscopy studies showed that poleward chromosome movement is associated with disassembly, or ‘melting’ of the kinetochore-attached microtubule fibers that link chromosomes to poles. Microtubule-marking techniques established that kinetochore-fiber disassembly often occurs through a ‘pac-man’ mechanism, where tubulin subunits are lost from kinetochore-attached plus ends and the kinetochore appears to consume its microtubule track as it moves poleward. In addition, kinetochore-fiber disassembly in many cells occurs partly through ‘flux’, where the microtubules flow continuously toward the poles and tubulin subunits are lost from minus ends. Molecular mechanistic models for how load-bearing attachments are maintained to disassembling microtubule ends, and how the forces are generated to drive pac-man and flux-based movements, are discussed.

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 LET-99 inhibits lateral posterior pulling forces during asymmetric spindle elongation in C. elegans embryos

2010 ◽  
Vol 189 (3) ◽  
pp. 481-495 ◽  
Author(s):  
Lori E. Krueger ◽  
Jui-Ching Wu ◽  
Meng-Fu Bryan Tsou ◽  
Lesilee S. Rose
Keyword(s):  
Spindle Pole ◽  
G Protein Signaling ◽  
Protein Signaling ◽  
Posterior Cortex ◽  
C Elegans ◽  
Pulling Forces ◽  
Lateral Posterior ◽  
Spindle Elongation ◽  
Pulling Force ◽  
Precise Distribution

Cortical pulling on astral microtubules positions the mitotic spindle in response to PAR polarity cues and G protein signaling in many systems. In Caenorhabditis elegans single-cell embryos, posterior spindle displacement depends on Gα and its regulators GPR-1/2 and LIN-5. GPR-1/2 and LIN-5 are necessary for cortical pulling forces and become enriched at the posterior cortex, which suggests that higher forces act on the posterior spindle pole compared with the anterior pole. However, the precise distribution of cortical forces and how they are regulated remains to be determined. Using spindle severing, single centrosome assays, and centrosome fragmentation, we show that both the anterior and posterior cortices generate more pulling force than the lateral–posterior region. Lateral inhibition depends on LET-99, which inhibits GPR-1/2 localization to produce a bipolar GPR-1/2 pattern. Thus, rather than two domains of cortical force, there are three. We propose that the attenuation of lateral forces prevents counterproductive pulling, resulting in a higher net force toward the posterior that contributes to spindle elongation and displacement.

scholarly journals Spindle dynamics and cell cycle regulation of dynein in the budding yeast, Saccharomyces cerevisiae.

1995 ◽  
Vol 130 (3) ◽  
pp. 687-700 ◽  
Author(s):  
E Yeh ◽  
R V Skibbens ◽  
J W Cheng ◽  
E D Salmon ◽  
K Bloom
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Translocation ◽  
Spindle Pole ◽  
Cell Cortex ◽  
Wild Type ◽  
Immunofluorescent Localization ◽  
Yeast Saccharomyces Cerevisiae ◽  
Spindle Dynamics ◽  
Spindle Elongation ◽  
Anaphase B

We have used time-lapse digital- and video-enhanced differential interference contrast (DE-DIC, VE-DIC) microscopy to study the role of dynein in spindle and nuclear dynamics in the yeast Saccharomyces cerevisiae. The real-time analysis reveals six stages in the spindle cycle. Anaphase B onset appears marked by a rapid phase of spindle elongation, simultaneous with nuclear migration into the daughter cell. The onset and kinetics of rapid spindle elongation are identical in wild type and dynein mutants. In the absence of dynein the nucleus does not migrate as close to the neck as in wild-type cells and initial spindle elongation is confined primarily to the mother cell. Rapid oscillations of the elongating spindle between the mother and bud are observed in wild-type cells, followed by a slower growth phase until the spindle reaches its maximal length. This stage is protracted in the dynein mutants and devoid of oscillatory motion. Thus dynein is required for rapid penetration of the nucleus into the bud and anaphase B spindle dynamics. Genetic analysis reveals that in the absence of a functional central spindle (ndcl), dynein is essential for chromosome movement into the bud. Immunofluorescent localization of dynein-beta-galactosidase fusion proteins reveals that dynein is associated with spindle pole bodies and the cell cortex: with spindle pole body localization dependent on intact microtubules. A kinetic analysis of nuclear movement also revealed that cytokinesis is delayed until nuclear translocation is completed, indicative of a surveillance pathway monitoring nuclear transit into the bud.

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 Mixing and Matching Chromosomes during Female Meiosis

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 696
Author(s):  
Thomas Rubin ◽  
Nicolas Macaisne ◽  
Jean-René Huynh
Keyword(s):  
Female Meiosis ◽  
Homologous Chromosomes ◽  
C Elegans ◽  
Similarities And Differences ◽  
Segregation Of Chromosomes

Meiosis is a key event in the manufacturing of an oocyte. During this process, the oocyte creates a set of unique chromosomes by recombining paternal and maternal copies of homologous chromosomes, and by eliminating one set of chromosomes to become haploid. While meiosis is conserved among sexually reproducing eukaryotes, there is a bewildering diversity of strategies among species, and sometimes within sexes of the same species, to achieve proper segregation of chromosomes. Here, we review the very first steps of meiosis in females, when the maternal and paternal copies of each homologous chromosomes have to move, find each other and pair. We explore the similarities and differences observed in C. elegans, Drosophila, zebrafish and mouse females.

The regulation of mitotic spindle function

1988 ◽  
Vol 66 (6) ◽  
pp. 490-514 ◽  
Author(s):  
Stephen M. Wolniak
Keyword(s):  
Morphological Changes ◽  
Cytosolic Calcium ◽  
Spindle Pole ◽  
Chromosome Movement ◽  
Mitotic Apparatus ◽  
Physiological Regulation ◽  
New Findings ◽  
Controlling Elements ◽  
Spindle Elongation ◽  
Spindle Function

The process of mitosis includes a series of morphological changes in the cell in which the directional movements of chromosomes are the most prominent. The presence of a microtubular array, known as the spindle or mitotic apparatus, provides at least a scaffold upon which these movements take place. The precise mechanism for chromosome movement remains obscure, but new findings suggest that the kinetochore may play a key role in chromosome movement toward the spindle pole, and that sliding interactions between or among adjacent microtubules may provide the mechanochemical basis for spindle elongation. The physiological regulation of the anaphase motors and of spindle operation either before or after anaphase remains equally elusive. Elicitors that may serve as controlling elements in spindle function include shifts in cytosolic calcium activity and perhaps the activation or inactivation of protein kinases, which in turn produce changes in the state of phosphorylation of specific spindle components.

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 Cytoplasmic Dynein's Mitotic Spindle Pole Localization Requires a Functional Anaphase-promoting Complex, γ-Tubulin, and NUDF/LIS1 in Aspergillus nidulans

2005 ◽  
Vol 16 (8) ◽  
pp. 3591-3605 ◽  
Author(s):  
Shihe Li ◽  
C. Elizabeth Oakley ◽  
Guifang Chen ◽  
Xiaoyan Han ◽  
Berl R. Oakley ◽  
...  
Keyword(s):  
Aspergillus Nidulans ◽  
Cytoplasmic Dynein ◽  
Spindle Pole ◽  
Chromosome Loss ◽  
Anaphase Promoting Complex ◽  
Mitotic Progression ◽  
Spindle Poles ◽  
Dynein Motor ◽  
Chromosome Separation ◽  
Spindle Elongation

In Aspergillus nidulans, cytoplasmic dynein and NUDF/LIS1 are found at the spindle poles during mitosis, but they seem to be targeted to this location via different mechanisms. The spindle pole localization of cytoplasmic dynein requires the function of the anaphase-promoting complex (APC), whereas that of NUDF does not. Moreover, although NUDF's localization to the spindle poles does not require a fully functional dynein motor, the function of NUDF is important for cytoplasmic dynein's targeting to the spindle poles. Interestingly, a γ-tubulin mutation, mipAR63, nearly eliminates the localization of cytoplasmic dynein to the spindle poles, but it has no apparent effect on NUDF's spindle pole localization. Live cell analysis of the mipAR63 mutant revealed a defect in chromosome separation accompanied by unscheduled spindle elongation before the completion of anaphase A, suggesting that γ-tubulin may recruit regulatory proteins to the spindle poles for mitotic progression. In A. nidulans, dynein is not apparently required for mitotic progression. In the presence of a low amount of benomyl, a microtubule-depolymerizing agent, however, a dynein mutant diploid strain exhibits a more pronounced chromosome loss phenotype than the control, indicating that cytoplasmic dynein plays a role in chromosome segregation.

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