scholarly journals Optogenetic control of PRC1 reveals that bridging fibers promote chromosome alignment by overlap length-dependent forces

2019 ◽  
Author(s):  
Mihaela Jagrić ◽  
Patrik Risteski ◽  
Jelena Martinčić ◽  
Ana Milas ◽  
Iva M. Tolić
Keyword(s):  
Metaphase Chromosome ◽  
Mechanical Coupling ◽  
Chromosome Position ◽  
Sister Kinetochore ◽  
Chromosome Alignment ◽  
Bridging Fibers ◽  
Optogenetic Control

AbstractDuring metaphase, chromosome position at the spindle equator is regulated by the forces exerted by kinetochore microtubules and polar ejection forces. However, the role of forces arising from mechanical coupling of sister kinetochore fibers with bridging fibers in chromosome alignment is unknown. Here we develop an optogenetic approach for acute removal of PRC1 to disassemble bridging fibers, and show that they promote chromosome alignment. Tracking of the plus-end protein EB3 revealed longer antiparallel overlaps of bridging microtubules upon PRC1 removal, which was accompanied by misaligned and lagging kinetochores. Kif4A/kinesin-4 and Kif18A/kinesin-8 were found within the bridging fiber and lost upon PRC1 removal, suggesting that these proteins regulate the overlap length of bridging microtubules. We propose that PRC1-mediated crosslinking of bridging microtubules and recruitment of kinesins to the bridging fiber promotes chromosome alignment by overlap length-dependent forces transmitted to the associated kinetochores fibers.

scholarly journals Optogenetic control of PRC1 reveals its role in chromosome alignment on the spindle by overlap length-dependent forces

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Mihaela Jagrić ◽  
Patrik Risteski ◽  
Jelena Martinčić ◽  
Ana Milas ◽  
Iva M Tolić
Keyword(s):  
Metaphase Chromosome ◽  
Mechanical Coupling ◽  
Chromosome Position ◽  
Sister Kinetochore ◽  
Chromosome Alignment ◽  
Bridging Fibers ◽  
Optogenetic Control

During metaphase, chromosome position at the spindle equator is regulated by the forces exerted by kinetochore microtubules and polar ejection forces. However, the role of forces arising from mechanical coupling of sister kinetochore fibers with bridging fibers in chromosome alignment is unknown. Here we develop an optogenetic approach for acute removal of PRC1 to partially disassemble bridging fibers and show that they promote chromosome alignment. Tracking of the plus-end protein EB3 revealed longer antiparallel overlaps of bridging microtubules upon PRC1 removal, which was accompanied by misaligned and lagging kinetochores. Kif4A/kinesin-4 and Kif18A/kinesin-8 were found within the bridging fiber and largely lost upon PRC1 removal, suggesting that these proteins regulate the overlap length of bridging microtubules. We propose that PRC1-mediated crosslinking of bridging microtubules and recruitment of kinesins to the bridging fiber promotes chromosome alignment by overlap length-dependent forces transmitted to the associated kinetochore fibers.

scholarly journals Sliding of kinetochore fibers along bridging fibers helps center the chromosomes on the spindle

2021 ◽  
Author(s):  
Patrik Risteski ◽  
Mihaela Jagrić ◽  
Iva M. Tolić
Keyword(s):  
Chromosome Segregation ◽  
Human Cells ◽  
Remarkable Feature ◽  
Mechanical Coupling ◽  
Chromosome Alignment ◽  
The Difference ◽  
Bridging Fibers ◽  
Lateral Length ◽  
Poleward Flux

ABSTRACTChromosome alignment at the spindle equator during metaphase is the most remarkable feature of mitosis, which promotes proper chromosome segregation and depends on the forces exerted at the plus end of kinetochore microtubules and polar ejection forces. However, forces arising from lateral mechanical coupling of kinetochore fibers with non-kinetochore microtubules play a role in chromosome alignment, but the mechanism is unclear. Here we develop a speckle microscopy assay to measure the poleward flux of individual microtubules in spindles of human cells and show that bridging microtubules slide apart and undergo poleward flux at a higher rate than kinetochore microtubules. Depletion of the microtubule coupler NuMa increased the difference in the flux velocity of kinetochore and bridging microtubules, suggesting that sliding forces from the bridging fiber are transmitted largely through NuMa onto the associated kinetochore fibers. Depletions of Kif18A/kinesin-8, Kif4A/kinesin-4, as well as double depletions of Kif18A together with Kif4A or Kif18A together with the crosslinker of antiparallel microtubules PRC1 increased the flux velocity of kinetochore fibers up to the velocity of bridging fibers, due to the increased coupling resulting from the extended antiparallel overlap regions. We found severe kinetochore misalignment after double Kif18A and Kif4A as well as Kif18A and PRC1 depletions compared to a single Kif18A depletion, suggesting that forces within the bridging fiber have a centering effect on the kinetochores. We propose that lateral length-dependent sliding forces that the bridging fiber exerts onto kinetochore fibers drive the movement of kinetochores towards the spindle center, thereby promoting chromosome alignment.

scholarly journals Augmin regulates kinetochore tension and spatial arrangement of spindle microtubules by nucleating bridging fibers

2020 ◽  
Author(s):  
Martina Manenica ◽  
Valentina Štimac ◽  
Isabella Koprivec ◽  
Juraj Simunić ◽  
Iva M. Tolić
Keyword(s):  
Critical Role ◽  
Spatial Arrangement ◽  
Knock Out ◽  
Daughter Cells ◽  
Sister Kinetochore ◽  
Division Spindle ◽  
Spindle Microtubules ◽  
Bridging Fibers ◽  
Poleward Flux

ABSTRACTThe mitotic spindle functions as a molecular micromachine that evenly distributes chromosomes into two daughter cells during cell division. Spindle microtubules in human cells are mainly nucleated at the centrosome and on the lateral surface of existing microtubules by the augmin complex. However, it is unknown how the augmin-mediated nucleation affects functionally distinct microtubule bundles and consequently the forces within the spindle. Here we show, by using siRNA depletion and CRISPR knock-out of the augmin complex subunits HAUS6 or HAUS8, that augmin is crucial for the nucleation of bridging microtubules, which laterally link sister kinetochore fibers. Augmin depletion resulted in a reduction in the number of microtubules within bridging fibers by around 80% and in kinetochore fibers by 40%, suggesting that the bridging microtubules are mainly nucleated at the surface of present microtubules. In augmin-depleted cells, the interkinetochore distance decreased preferentially for kinetochores that lack a bridging fiber, independently of the thickness of their k-fibers, implying that augmin affects forces on kinetochores largely via bridging fibers. Without augmin the number of bridging fibers decreased, with the remaining ones mostly confined to the spindle periphery with an increased overlap length. A slower poleward flux of microtubules after augmin depletion is indicative of slower sliding within the bridging fiber. Our results demonstrate a critical role of augmin in the formation of bridging microtubules and proper architecture of the metaphase spindle, suggesting a model where sliding of augmin-nucleated bridging microtubules promotes poleward flux of k-fibers and thus tension on kinetochores.

EB1 Is Essential for Spindle Formation and Chromosome Alignment During Oocyte Meiotic Maturation in Mice

2021 ◽  
pp. 1-7
Author(s):  
Dongjie Zhou ◽  
Zheng-Wen Nie ◽  
Xiang-Shun Cui
Keyword(s):  
Cell Shape ◽  
Control Cell ◽  
Meiotic Maturation ◽  
Junctional Complex ◽  
Spindle Formation ◽  
Oocyte Meiosis ◽  
Polarized Cell Growth ◽  
Chromosome Alignment ◽  
Oocyte Meiotic Maturation

The cytoskeleton plays an orchestrating role in polarized cell growth. Microtubules (MTs) not only play critical roles in chromosome alignment and segregation but also control cell shape, division, and motility. A member of the plus-end tracking proteins, end-binding protein 1 (EB1), regulates MT dynamics and plays vital roles in maintaining spindle symmetry and chromosome alignment during mitosis. However, the role of EB1 in mouse oocyte meiosis remains unknown. Here, we examined the localization patterns and expression levels of EB1 at different stages. EB1 protein level was found to be stable during meiosis. EB1 mainly localized along the spindle and had a similar localization pattern as that of α-tubulin. The EB1 protein was degraded with a Trim-Away method, and the results were further confirmed with western blotting and immunofluorescence. At 12 h of culture after EB1 knockdown (KD), a reduced number of mature MII oocytes were observed. EB1 KD led to spindle disorganization, chromosome misalignment, and missegregation; β-catenin protein binds to actin via the adherens junctional complex, which was significantly reduced in the EB1 KD oocytes. Collectively, we propose that the impairment of EB1 function manipulates spindle formation, thereby promoting chromosomal loss, which is expected to fuel aneuploidy and possibly fertilization failure.

Stochastic Aspects of Matrix Cracking in Brittle Matrix Composites

1993 ◽  
Vol 115 (3) ◽  
pp. 314-318 ◽  
Author(s):  
S. M. Spearing ◽  
F. W. Zok
Keyword(s):  
Matrix Cracking ◽  
Matrix Composites ◽  
Brittle Matrix ◽  
Tensile Response ◽  
Brittle Matrix Composites ◽  
Crack Interactions ◽  
The Matrix ◽  
Interface Slip ◽  
Bridging Fibers

A computer simulation of multiple cracking in fiber-reinforced brittle matrix composites has been conducted, with emphasis on the role of the matrix flaw distribution. The simulations incorporate the effect of bridging fibers on the stress required for cracking. Both short and long (steady-state) flaws are considered. Furthermore, the effects of crack interactions (through the overlap of interface slip lengths) are incorporated. The influence of the crack distribution on the tensile response of such composites is also examined.

scholarly journals Aurora B Regulates Formin mDia3 in Achieving Metaphase Chromosome Alignment

2011 ◽  
Vol 20 (3) ◽  
pp. 342-352 ◽  
Author(s):  
Lina Cheng ◽  
Jiayin Zhang ◽  
Sana Ahmad ◽  
Lorene Rozier ◽  
Haiqian Yu ◽  
...  
Keyword(s):  
Metaphase Chromosome ◽  
Aurora B ◽  
Chromosome Alignment

Metaphase Chromosome Structure: The Role of Nonhistone Proteins

1978 ◽  
Vol 42 (0) ◽  
pp. 351-360 ◽  
Author(s):  
U. K. Laemmli ◽  
S. M. Cheng ◽  
K. W. Adolph ◽  
J. R. Paulson ◽  
J. A. Brown ◽  
...  
Keyword(s):  
Metaphase Chromosome ◽  
Chromosome Structure ◽  
Nonhistone Proteins ◽  
Metaphase Chromosome Structure

scholarly journals BubR1 and APC/EB1 cooperate to maintain metaphase chromosome alignment

2007 ◽  
Vol 179 (2) ◽  
pp. 357-357
Author(s):  
Jiayin Zhang ◽  
Sana Ahmad ◽  
Yinghui Mao
Keyword(s):  
Metaphase Chromosome ◽  
Chromosome Alignment

The Effect of Nonlinear Piezoelectric Coupling on Vibration-Based Energy Harvesting

2008 ◽  
Author(s):  
Angela Triplett ◽  
D. Dane Quinn
Keyword(s):  
Energy Harvesting ◽  
Electrical Power ◽  
Original System ◽  
Constitutive Relationship ◽  
Ambient Vibration ◽  
Attractive Alternative ◽  
Maximum Output ◽  
Power Sources ◽  
Mechanical Coupling

Advances in electronic and consumer technology are increasing the need for smaller, more efficient energy sources. Thus vibration-based energy harvesting, the scavenging of energy from existing ambient vibration sources and its conversion to useful electrical power, is becoming an increasingly attractive alternative to traditional power sources such as batteries. Energy harvesting devices have been developed based on a number of electro-mechanical coupling mechanisms and their design must be optimized to produce the maximum output for given environmental conditions. While the role of nonlinearities in the components has been shown to be significant in terms of the overall device efficiency, few studies have systematically investigated their influence on the system performance. In this work the role of a nonlinear piezoelectric relationship is considered on the performance of a vibration-based energy harvester. Using a Poincare´-Lindstedt perturbation analysis the response of the harvesting system is approximated, including mechanical damping, stiffness nonlinearities, and the above mentioned nonlinear piezoelectric constitutive relationship. The predicted behavior is then compared against numerical simulations of the original system, focusing on the relationship between the power generated by the device, the ambient vibration characteristics, and the nonlinearities in the system.

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