The Chirality of the Mitotic Spindle Provides a Mechanical Response to Forces and Depends on Microtubule Motors and Crosslinkers

2021 ◽  
Author(s):  
Monika Trupinić ◽  
Barbara Kokanović ◽  
Ivana Ponjavić ◽  
Ivan Barišić ◽  
Siniša Šegvić ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Mechanical Response ◽  
Microtubule Motors

scholarly journals Motile kinetochores and polar ejection forces dictate chromosome position on the vertebrate mitotic spindle

1994 ◽  
Vol 124 (3) ◽  
pp. 223-233 ◽  
Author(s):  
CL Rieder ◽  
ED Salmon
Keyword(s):  
Mitotic Spindle ◽  
Constant Velocity ◽  
Molecular Mechanisms ◽  
Dynamic Instability ◽  
Microtubule Dynamic ◽  
Pole Motion ◽  
Microtubule Motors ◽  
Chromosome Position ◽  
Pulling Forces

We argue that hypotheses for how chromosomes achieve a metaphase alignment, that are based solely on a tug-of-war between poleward pulling forces produced along the length of opposing kinetochore fibers, are no longer tenable for vertebrates. Instead, kinetochores move themselves and their attached chromosomes, poleward and away from the pole, on the ends of relatively stationary but shortening/elongating kinetochore fiber microtubules. Kinetochores are also "smart" in that they switch between persistent constant-velocity phases of poleward and away from the pole motion, both autonomously and in response to information within the spindle. Several molecular mechanisms may contribute to this directional instability including kinetochore-associated microtubule motors and kinetochore microtubule dynamic instability. The control of kinetochore directional instability, to allow for congression and anaphase, is likely mediated by a vectorial mechanism whose magnitude and orientation depend on the density and orientation or growth of polar microtubules. Polar microtubule arrays have been shown to resist chromosome poleward motion and to push chromosomes away from the pole. These "polar ejection forces" appear to play a key role in regulating kinetochore directional instability, and hence, positions achieved by chromosomes on the spindle.

scholarly journals The nuclear-mitotic apparatus protein is important in the establishment and maintenance of the bipolar mitotic spindle apparatus.

1992 ◽  
Vol 3 (11) ◽  
pp. 1259-1267 ◽  
Author(s):  
C H Yang ◽  
M Snyder
Keyword(s):  
Mitotic Spindle ◽  
Polar Regions ◽  
Mitotic Apparatus ◽  
Structural Support ◽  
Microtubule Motors ◽  
Interphase Cells ◽  
Spindle Apparatus ◽  
Nuclear Mitotic Apparatus ◽  
Multicellular Organisms ◽  
First Time

The formation and maintenance of the bipolar mitotic spindle apparatus require a complex and balanced interplay of several mechanisms, including the stabilization and separation of polar microtubules and the action of various microtubule motors. Nonmicrotubule elements are also present throughout the spindle apparatus and have been proposed to provide a structural support for the spindle. The Nuclear-Mitotic Apparatus protein (NuMA) is an abundant 240 kD protein that is present in the nucleus of interphase cells and concentrates in the polar regions of the spindle apparatus during mitosis. Sequence analysis indicates that NuMA possesses an unusually long alpha-helical central region characteristic of many filament forming proteins. In this report we demonstrate that microinjection of anti-NuMA antibodies into interphase and prophase cells results in a failure to form a mitotic spindle apparatus. Furthermore, injection of metaphase cells results in the collapse of the spindle apparatus into a monopolar microtubule array. These results identify for the first time a nontubulin component important for both the establishment and stabilization of the mitotic spindle apparatus in multicellular organisms. We suggest that nonmicrotubule structural components may be important for these processes.

scholarly journals Twist of the mitotic spindle culminates at anaphase onset and depends on microtubule-associated proteins along with external forces

2020 ◽  
Author(s):  
Monika Trupinić ◽  
Ivana Ponjavić ◽  
Barbara Kokanović ◽  
Ivan Barišić ◽  
Siniša Šegvić ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Molecular Mechanisms ◽  
Mechanical Response ◽  
Torsional Rigidity ◽  
Physiological Role ◽  
Cancer Cell Line ◽  
Left Handed ◽  
Associated Proteins ◽  
Bridging Fibers ◽  
External Forces

ABSTRACTMechanical forces produced by motor proteins and microtubule dynamics within the mitotic spindle are crucial for the movement of chromosomes and their segregation into the emerging daughter cells. In addition to linear forces, rotational forces are present in the spindle, reflected in the left-handed twisted shapes of microtubule bundles that make the spindle chiral. However, the molecular origins of spindle chirality are unknown. Here we show that spindles are most twisted at the beginning of anaphase, and reveal multiple molecular players involved in spindle chirality. Inhibition of Eg5/kinesin-5 in a non-cancer cell line abolished spindle twist and depletion of Kif18A/kinesin-8 resulted in a right-handed twist, implying that these motors regulate twist likely by rotating the microtubules around one another within the antiparallel overlaps of bridging fibers. Depletion of the crosslinker PRC1 resulted in a right-handed twist, indicating that PRC1 may contribute to the twist by constraining free rotation of microtubules. Overexpression of PRC1 abolished twist, possibly due to increased torsional rigidity of the bundles. Depletion of augmin led to a right-handed twist, suggesting that twist depends on the geometry of microtubule nucleation. Round spindles were more twisted than elongated ones, a notion that we directly tested by compressing the spindle along its axis, which resulted in stronger left-handed twist, indicating a correlation between bending moments and twist. We conclude that spindle twist is controlled by multiple molecular mechanisms acting at different locations within the spindle as well as forces, and propose a potential physiological role of twist in promoting passive mechanical response of the spindle to forces during metaphase.

Microtubule motors associated with kinetochores in mitotic cells

1993 ◽  
Vol 51 ◽  
pp. 76-77
Author(s):  
Linda Wordeman
Keyword(s):  
Mitotic Spindle ◽  
Centromere Region ◽  
Mitotic Chromosomes ◽  
Directed Movement ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
Microtubule Motors ◽  
Double Label ◽  
Spindle Microtubules ◽  
Kinetochore Region

Chromosomes in dividing tissue culture cells exhibit three types of movement along mitotic spindle microtubules: l)Fast minus-end directed movement (prometaphase), 2)Plus-end directed movement, and 3) Slow minus-end directed movement (anaphase) . In all cases these movements are mediated by the kinetochore region of the centromere of mitotic chromosomes. This region consists of three domains based on both immunocytochemistry and electron microscopy. The outermost or kinetochore domain is composed of the distal fibrous corona and trilamminar plate. The central and pairing domains are located in the chromatin beneath the kinetochore. Both plus- and minus-end directed microtubule motors have been localized to the kinetochore region of mitotic CHO chromosomes. I have used double-label immunocytochemistry to map the location of these motors within the centromere region at the level of the light microscope. Furthermore, I have cloned and expressed a number of novel kinesin-related motors, two of which (Clone 26 and Clone 14) are localized to kinetochores and kinetochore microtubules, respectively.

scholarly journals The LGN:Insc tetramer stabilises the apical site in asymmetric cell divisions

2014 ◽  
Vol 70 (a1) ◽  
pp. C1057-C1057
Author(s):  
Simone Culurgioni ◽  
Sara Mari ◽  
Sara Gallini ◽  
Greta Bonetto ◽  
Marina Mapelli
Keyword(s):  
Mitotic Spindle ◽  
Crystallographic Structure ◽  
Binding Assays ◽  
Asymmetric Cell Divisions ◽  
Daughter Cells ◽  
Cell Divisions ◽  
Microtubule Motors ◽  
Apical Site ◽  
Polarity Proteins

Asymmetric cell divisions regulate the position and the fate choice of daughter cells, with impact on developmental programs and tissue homeostasis. The asymmetric outcome of a stem cell division relies on the coordination between cortical polarity and the orientation of the mitotic spindle. To date the adaptor Inscuteable (Insc) is considered the molecular bridge between cortical polarity proteins and the spindle tethering machinery assembled on NuMA:LGN:Gαi. Insc interacts with the polarity protein Par3, and competes with NuMA for the binding to LGN [1]. I will present the crystallographic structure of Drosophila LGN in complex with the asymmetric domain of Insc. The structure reveals a tetrameric arrangement of intertwined molecules, and is compatible with the concomitant binding of Insc to LGN and Par3. Binding assays indicate that Insc interacts directly with the PDZ region of Par3. The finding that LGN enters a stable tetrameric complex with Insc and Par3 suggests a novel function for LGN in stabilizing the apical site, where polarity proteins enrich during asymmetric cell divisions. I will propose a revised model for mitotic spindle coupling to polarity cues based on the dual role of LGN in organizing microtubule motors when in complex with NuMA and Dynein, and securing their cortical attachment when bound to Insc and Par3.

scholarly journals Lesions in Many Different Spindle Components Activate the Spindle Checkpoint in the Budding Yeast Saccharomyces cerevisiae

Genetics ◽  
1999 ◽  
Vol 152 (2) ◽  
pp. 509-518 ◽  
Author(s):  
Kevin G Hardwick ◽  
Rong Li ◽  
Cathy Mistrot ◽  
Rey-Huei Chen ◽  
Phoebe Dann ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Spindle Pole Body ◽  
Spindle Checkpoint ◽  
Spindle Pole ◽  
Structural Components ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cycle Arrest ◽  
Microtubule Polymerization ◽  
Microtubule Motors ◽  
Chromosome Alignment

Abstract The spindle checkpoint arrests cells in mitosis in response to defects in the assembly of the mitotic spindle or errors in chromosome alignment. We determined which spindle defects the checkpoint can detect by examining the interaction of mutations that compromise the checkpoint (mad1, mad2, and mad3) with those that damage various structural components of the spindle. Defects in microtubule polymerization, spindle pole body duplication, microtubule motors, and kinetochore components all activate the MAD-dependent checkpoint. In contrast, the cell cycle arrest caused by mutations that induce DNA damage (cdc13), inactivate the cyclin proteolysis machinery (cdc16 and cdc23), or arrest cells in anaphase (cdc15) is independent of the spindle checkpoint.

scholarly journals Mitotic kinesins in action: diffusive searching, directional switching, and ensemble coordination

2018 ◽  
Vol 29 (10) ◽  
pp. 1153-1156 ◽  
Author(s):  
Allison M. Gicking ◽  
Weihong Qiu ◽  
William O. Hancock
Keyword(s):  
Single Molecule ◽  
Mitotic Spindle ◽  
Cell Biology ◽  
Motor Systems ◽  
Microtubule Motors ◽  
Biophysical Studies ◽  
Cellular Behaviors ◽  
Mitotic Spindle Assembly

Mitotic spindle assembly requires the collective action of multiple microtubule motors that coordinate their activities in ensembles. However, despite significant advances in our understanding of mitotic kinesins at the single-motor level, multi-motor systems are challenging to reconstitute in vitro and thus less well understood. Recent findings highlighted in this perspective demonstrate how various properties of kinesin-5 and -14 motors—diffusive searching, directional switching, and multivalent interactions—allow them to achieve their physiological roles of cross-linking parallel microtubules and sliding antiparallel ones during cell division. Additionally, we highlight new experimental techniques that will help bridge the gap between in vitro biophysical studies and in vivo cell biology investigations and provide new insights into how specific single-molecule mechanisms generate complex cellular behaviors.

scholarly journals Alzheimer Aβ disrupts the mitotic spindle and directly inhibits mitotic microtubule motors

Cell Cycle ◽  
2011 ◽  
Vol 10 (9) ◽  
pp. 1397-1410 ◽  
Author(s):  
Sergiy I. Borysov ◽  
Antoneta Granic ◽  
Jaya Padmanabhan ◽  
Claire E. Walczak ◽  
Huntington Potter
Keyword(s):  
Mitotic Spindle ◽  
Microtubule Motors

Structural Studies on Mitotic Spindle Fibres

1978 ◽  
Vol 36 (3) ◽  
pp. 615-626
Author(s):  
J.R. Mcintosh
Keyword(s):  
Chemical Composition ◽  
Mitotic Spindle ◽  
Structural Studies ◽  
Mitotic Apparatus ◽  
Chemical Studies ◽  
Medical Interest ◽  
Spindle Fibres

The mitotic apparatus is a structure of obvious biological and medical interest, but it has proved to be a difficult cellular machine to understand. The chemical composition of the spindle is only slightly elucidated, largely because of the difficulties in preparing useful isolates of the structure. Chemical studies of the mitotic spindle have been reviewed elsewhere (Mcintosh, 1977), and will not be discussed further here. One would think that structural studies on the mitotic apparatus (MA) in situ would be straightforward, but even with this approach there is some disagreement in the results obtained with various methods and by different investigators. In this paper I will review briefly the approaches which have been used in structural studies of the MA, pointing out the strengths and problems of each approach. I will summarize the principal findings of the different methods, and identify what seem to be fruitful avenues for further work.

Filaments and membranes in the mitotic apparatus

1983 ◽  
Vol 41 ◽  
pp. 544-547
Author(s):  
Kent McDonald
Keyword(s):  
Intermediate Filaments ◽  
Mitotic Spindle ◽  
Mitotic Apparatus ◽  
Light Microscope Level ◽  
Microtubule Associated Proteins ◽  
Recent Developments ◽  
Associated Proteins ◽  
Force Generator ◽  
Spindle Function ◽  
Antibody Technology

At the light microscope level the recent developments and interest in antibody technology have permitted the localization of certain non-microtubule proteins within the mitotic spindle, e.g., calmodulin, actin, intermediate filaments, protein kinases and various microtubule associated proteins. Also, the use of fluorescent probes like chlorotetracycline suggest the presence of membranes in the spindle. Localization of non-microtubule structures in the spindle at the EM level has been less rewarding. Some mitosis researchers, e.g., Rarer, have maintained that actin is involved in mitosis movements though the bulk of evidence argues against this interpretation. Others suggest that a microtrabecular network such as found in chromatophore granule movement might be a possible force generator but there is little evidence for or against this view. At the level of regulation of spindle function, Harris and more recently Hepler have argued for the importance of studying spindle membranes. Hepler also believes that membranes might play a structural or mechanical role in moving chromosomes.

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