scholarly journals The forces that position a mitotic spindle asymmetrically are tethered until after the time of spindle assembly

2004 ◽  
Vol 167 (2) ◽  
pp. 245-256 ◽  
Author(s):  
Jean-Claude Labbé ◽  
Erin K. McCarthy ◽  
Bob Goldstein
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Cell Cortex ◽  
Par Proteins ◽  
Temporal Regulation ◽  
C Elegans ◽  
Pulling Forces ◽  
Chromosome Separation ◽  
And Shifts ◽  
Early Phases

Regulation of the mitotic spindle's position is important for cells to divide asymmetrically. Here, we use Caenorhabditis elegans embryos to provide the first analysis of the temporal regulation of forces that asymmetrically position a mitotic spindle. We find that asymmetric pulling forces, regulated by cortical PAR proteins, begin to act as early as prophase and prometaphase, even before the spindle forms and shifts to a posterior position. The spindle does not shift asymmetrically during these early phases due to a tethering force, mediated by astral microtubules that reach the anterior cell cortex. We show that this tether is normally released after spindle assembly and independently of anaphase entry. Monitoring microtubule dynamics by photobleaching segments of microtubules during anaphase revealed that spindle microtubules do not undergo significant poleward flux in C. elegans. Together with the known absence of anaphase A, these data suggest that the major forces contributing to chromosome separation during anaphase originate outside the spindle. We propose that the forces positioning the mitotic spindle asymmetrically are tethered until after the time of spindle assembly and that these same forces are used later to drive chromosome segregation at anaphase.

scholarly journals Tumor suppressor APC is an attenuator of spindle-pulling forces during C. elegans asymmetric cell division

2018 ◽  
Vol 115 (5) ◽  
pp. E954-E963 ◽  
Author(s):  
Kenji Sugioka ◽  
Lars-Eric Fielmich ◽  
Kota Mizumoto ◽  
Bruce Bowerman ◽  
Sander van den Heuvel ◽  
...  
Keyword(s):  
Cell Division ◽  
Tumor Suppressor ◽  
Mitotic Spindle ◽  
Asymmetric Cell Division ◽  
Cell Cortex ◽  
Dependent Manner ◽  
C Elegans ◽  
Pulling Forces ◽  
Underlying Mechanisms ◽  
Pulling Force

The adenomatous polyposis coli (APC) tumor suppressor has dual functions in Wnt/β-catenin signaling and accurate chromosome segregation and is frequently mutated in colorectal cancers. Although APC contributes to proper cell division, the underlying mechanisms remain poorly understood. Here we show that Caenorhabditis elegans APR-1/APC is an attenuator of the pulling forces acting on the mitotic spindle. During asymmetric cell division of the C. elegans zygote, a LIN-5/NuMA protein complex localizes dynein to the cell cortex to generate pulling forces on astral microtubules that position the mitotic spindle. We found that APR-1 localizes to the anterior cell cortex in a Par–aPKC polarity-dependent manner and suppresses anterior centrosome movements. Our combined cell biological and mathematical analyses support the conclusion that cortical APR-1 reduces force generation by stabilizing microtubule plus-ends at the cell cortex. Furthermore, APR-1 functions in coordination with LIN-5 phosphorylation to attenuate spindle-pulling forces. Our results document a physical basis for the attenuation of spindle-pulling force, which may be generally used in asymmetric cell division and, when disrupted, potentially contributes to division defects in cancer.

scholarly journals The tumor suppressor APC is an attenuator of spindle-pulling forces during C. elegans asymmetric cell division

2017 ◽  
Author(s):  
Kenji Sugioka ◽  
Lars-Eric Fielmich ◽  
Kota Mizumoto ◽  
Bruce Bowerman ◽  
Sander van den Heuvel ◽  
...  
Keyword(s):  
Cell Division ◽  
Mitotic Spindle ◽  
Asymmetric Cell Division ◽  
Cell Cortex ◽  
Colorectal Cancers ◽  
Adenomatous Polyposis ◽  
Polyposis Coli ◽  
C Elegans ◽  
Pulling Forces ◽  
Pulling Force

AbstractThe adenomatous polyposis coli (APC) tumor suppressor has dual functions in Wnt/ß-catenin signaling and accurate chromosome segregation, and is frequently mutated in colorectal cancers. Although APC contributes to proper cell division, the underlying mechanisms remain poorly understood. Here we show that C. elegans APR-1/APC is an attenuator of the pulling forces acting on the mitotic spindle. During asymmetric cell division of the C. elegans zygote, a LIN-5/NuMA protein complex localizes dynein to the cell cortex to generate pulling forces on astral microtubules that position the mitotic spindle. We found that APR-1 localizes to the anterior cell cortex in a Par-aPKC polarity-dependent manner and suppresses anterior centrosome movements. Our combined cell biological and mathematical analyses support the conclusion that cortical APR-1 reduces force generation by stabilizing microtubule plus ends at the cell cortex. Furthermore, APR-1 functions in coordination with LIN-5 phosphorylation to attenuate spindle pulling forces. Our results document a physical basis for spindle-pulling force attenuation, which may be generally used in asymmetric cell division, and when disrupted potentially contributes to division defects in cancer.Significance StatementAPC (adenomatous polyposis coli) is a Wnt signaling component as well as a microtubule-associated protein, and its mutations are frequently associated with colorectal cancers in humans. Although APC stabilizes microtubules (MTs), its mechanical role during cell division is largely unknown. Here we show that APC is an attenuator of forces acting on the mitotic spindle during asymmetric cell division of the C. elegans zygote. We performed live-imaging, laser-microsurgery, and numerical simulation to show how APC suppresses spindle pulling force generation by stabilizing microtubule plus-ends and reducing microtubule catastrophe frequency at the cell cortex. Our study is the first to document a mechanical role for the APC protein, and provides a physical basis for spindle-pulling force attenuation.

scholarly journals Cortical microtubule pulling forces contribute to the union of the parental genomes in the C. elegans zygote

2021 ◽  
Author(s):  
Griselda VELEZ-AGUILERA ◽  
Batool OSSAREH-NAZARI ◽  
Lucie VAN HOVE ◽  
Nicolas Joly ◽  
Lionel Pintard
Keyword(s):  
Mitotic Spindle ◽  
Cortical Microtubule ◽  
Temporal Coordination ◽  
C Elegans ◽  
Astral Microtubule ◽  
Pulling Forces ◽  
Single Nucleus ◽  
Spindle Elongation

Previously, we reported that the Polo-like kinase PLK-1 phosphorylates the single C. elegans lamin (LMN-1) to trigger lamina depolymerization during mitosis. We showed that this event is required for the formation of a pronuclear envelopes scission event that removes membranes on the juxtaposed oocyte and sperm pronuclear envelopes in the zygote, allowing the parental chromosomes to merge in a single nucleus after segregation (Velez-Aguilera, 2020). Here we show that cortical microtubule pulling forces contribute to pronuclear envelopes scission by promoting mitotic spindle elongation. We also demonstrate that weakening of the pronuclear envelopes, via PLK-1-mediated lamina depolymerization, is a prerequisite for the astral microtubule pulling forces to trigger pronuclear membranes scission. Finally, we provide evidence that PLK-1 mainly acts via lamina depolymerization in this process. These observations thus indicate that temporal coordination between lamina depolymerization and mitotic spindle elongation facilitates pronuclear envelopes scission and parental genomes unification.

scholarly journals Dynein light chain 1 and a spindle-associated adaptor promote dynein asymmetry and spindle orientation

2012 ◽  
Vol 198 (6) ◽  
pp. 1039-1054 ◽  
Author(s):  
Anja K. Dunsch ◽  
Dean Hammond ◽  
Jennifer Lloyd ◽  
Lothar Schermelleh ◽  
Ulrike Gruneberg ◽  
...  
Keyword(s):  
Light Chain ◽  
Mitotic Spindle ◽  
Regulatory System ◽  
Cytoplasmic Dynein ◽  
Spindle Orientation ◽  
Growth Surface ◽  
Cell Cortex ◽  
Dynein Light Chain ◽  
Dynein Motor ◽  
Pulling Forces

The cytoplasmic dynein motor generates pulling forces to center and orient the mitotic spindle within the cell. During this positioning process, dynein oscillates from one pole of the cell cortex to the other but only accumulates at the pole farthest from the spindle. Here, we show that dynein light chain 1 (DYNLL1) is required for this asymmetric cortical localization of dynein and has a specific function defining spindle orientation. DYNLL1 interacted with a spindle-microtubule–associated adaptor formed by CHICA and HMMR via TQT motifs in CHICA. In cells depleted of CHICA or HMMR, the mitotic spindle failed to orient correctly in relation to the growth surface. Furthermore, CHICA TQT motif mutants localized to the mitotic spindle but failed to recruit DYNLL1 to spindle microtubules and did not correct the spindle orientation or dynein localization defects. These findings support a model where DYNLL1 and CHICA-HMMR form part of the regulatory system feeding back spindle position to dynein at the cell cortex.

scholarly journals Centrosome Maturation and Mitotic Spindle Assembly in C. elegans Require SPD-5, a Protein with Multiple Coiled-Coil Domains

2002 ◽  
Vol 3 (5) ◽  
pp. 673-684 ◽  
Author(s):  
Danielle R. Hamill ◽  
Aaron F. Severson ◽  
J.Clayton Carter ◽  
Bruce Bowerman
Keyword(s):  
Mitotic Spindle ◽  
Coiled Coil ◽  
Spindle Assembly ◽  
C Elegans ◽  
Mitotic Spindle Assembly

scholarly journals The C. elegans RSA Complex Localizes Protein Phosphatase 2A to Centrosomes and Regulates Mitotic Spindle Assembly

Cell ◽  
2007 ◽  
Vol 128 (1) ◽  
pp. 115-127 ◽  
Author(s):  
Anne-Lore Schlaitz ◽  
Martin Srayko ◽  
Alexander Dammermann ◽  
Sophie Quintin ◽  
Natalie Wielsch ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Spindle Assembly ◽  
C Elegans ◽  
Phosphatase 2A ◽  
Mitotic Spindle Assembly

scholarly journals The APC/C targets the Cep152-Cep63 complex at the centrosome to regulate mitotic spindle assembly

2021 ◽  
Author(s):  
Thomas Tischer ◽  
Jing Yang ◽  
David Barford
Keyword(s):  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Protein Abundance ◽  
Anaphase Promoting Complex ◽  
Mitotic Progression ◽  
Centrosomal Protein ◽  
Temporal Regulation ◽  
Spindle Poles ◽  
Main Protein ◽  
Mitotic Spindle Assembly

The control of protein abundance is a fundamental regulatory mechanism during mitosis. The anaphase promoting complex/cyclosome (APC/C) is the main protein ubiquitin ligase responsible for the temporal regulation of mitotic progression. It has been proposed that the APC/C might fulfil other functions including assembly of the mitotic spindle. Here, we show that the APC/C localizes to centrosomes, the organizers of the eukaryotic microtubule cytoskeleton, specifically during mitosis. Recruitment of the APC/C to spindle poles requires the centrosomal protein Cep152, and we identified Cep152 as both an APC/C interaction partner and as an APC/C substrate. Previous studies showed that Cep152 forms a complex with Cep57 and Cep63. The APC/C-mediated ubiquitination of Cep152 at the centrosome releases Cep57 from this inhibitory complex and enables its interaction with pericentrin, a critical step in promoting microtubule nucleation. Thus, our study extends the function of the APC/C from being a regulator of mitosis to also acting as a positive governor of spindle assembly. The APC/C thereby integrates control of these two important processes in a temporal manner.

scholarly journals Control of nuclear centration in the C. elegans zygote by receptor-independent Gα signaling and myosin II

2007 ◽  
Vol 178 (7) ◽  
pp. 1177-1191 ◽  
Author(s):  
Morgan B. Goulding ◽  
Julie C. Canman ◽  
Eric N. Senning ◽  
Andrew H. Marcus ◽  
Bruce Bowerman
Keyword(s):  
Mitotic Spindle ◽  
Myosin Ii ◽  
Nonmuscle Myosin ◽  
Wild Type ◽  
Spindle Positioning ◽  
C Elegans ◽  
Nonmuscle Myosin Ii ◽  
Pulling Forces ◽  
Actomyosin Contraction

Mitotic spindle positioning in the Caenorhabditis elegans zygote involves microtubule-dependent pulling forces applied to centrosomes. In this study, we investigate the role of actomyosin in centration, the movement of the nucleus–centrosome complex (NCC) to the cell center. We find that the rate of wild-type centration depends equally on the nonmuscle myosin II NMY-2 and the Gα proteins GOA-1/GPA-16. In centration- defective let-99(−) mutant zygotes, GOA-1/GPA-16 and NMY-2 act abnormally to oppose centration. This suggests that LET-99 determines the direction of a force on the NCC that is promoted by Gα signaling and actomyosin. During wild-type centration, NMY-2–GFP aggregates anterior to the NCC tend to move further anterior, suggesting that actomyosin contraction could pull the NCC. In GOA-1/GPA-16–depleted zygotes, NMY-2 aggregate displacement is reduced and largely randomized, whereas in a let-99(−) mutant, NMY-2 aggregates tend to make large posterior displacements. These results suggest that Gα signaling and LET-99 control centration by regulating polarized actomyosin contraction.

scholarly journals A two-step mechanism for the inactivation of microtubule organizing center function at the centrosome

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Jérémy Magescas ◽  
Jenny C Zonka ◽  
Jessica L Feldman
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Outer Sphere ◽  
Microtubule Organizing Center ◽  
C Elegans ◽  
Mitotic Kinases ◽  
Pulling Forces ◽  
Organizing Center ◽  
Pericentriolar Material ◽  
Step Mechanism

The centrosome acts as a microtubule organizing center (MTOC), orchestrating microtubules into the mitotic spindle through its pericentriolar material (PCM). This activity is biphasic, cycling through assembly and disassembly during the cell cycle. Although hyperactive centrosomal MTOC activity is a hallmark of some cancers, little is known about how the centrosome is inactivated as an MTOC. Analysis of endogenous PCM proteins in C. elegans revealed that the PCM is composed of partially overlapping territories organized into an inner and outer sphere that are removed from the centrosome at different rates and using different behaviors. We found that phosphatases oppose the addition of PCM by mitotic kinases, ultimately catalyzing the dissolution of inner sphere PCM proteins at the end of mitosis. The nature of the PCM appears to change such that the remaining aging PCM outer sphere is mechanically ruptured by cortical pulling forces, ultimately inactivating MTOC function at the centrosome.

scholarly journals Optogenetic dissection of mitotic spindle positioning in vivo

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Lars-Eric Fielmich ◽  
Ruben Schmidt ◽  
Daniel J Dickinson ◽  
Bob Goldstein ◽  
Anna Akhmanova ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Membrane Anchor ◽  
Spindle Positioning ◽  
C Elegans ◽  
Cell Cleavage ◽  
Evolutionarily Conserved ◽  
Pulling Forces ◽  
Endogenous Proteins ◽  
Pulling Force

The position of the mitotic spindle determines the plane of cell cleavage, and thereby daughter cell location, size, and content. Spindle positioning is driven by dynein-mediated pulling forces exerted on astral microtubules, which requires an evolutionarily conserved complex of Gα∙GDP, GPR-1/2Pins/LGN, and LIN-5Mud/NuMA proteins. To examine individual functions of the complex components, we developed a genetic strategy for light-controlled localization of endogenous proteins in C. elegans embryos. By replacing Gα and GPR-1/2 with a light-inducible membrane anchor, we demonstrate that Gα∙GDP, Gα∙GTP, and GPR-1/2 are not required for pulling-force generation. In the absence of Gα and GPR-1/2, cortical recruitment of LIN-5, but not dynein itself, induced high pulling forces. The light-controlled localization of LIN-5 overruled normal cell-cycle and polarity regulation and provided experimental control over the spindle and cell-cleavage plane. Our results define Gα∙GDP–GPR-1/2Pins/LGN as a regulatable membrane anchor, and LIN-5Mud/NuMA as a potent activator of dynein-dependent spindle-positioning forces.

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