scholarly journals TPX2 activation by GM130 controls astral microtubule formation and spindle orientation

2020 ◽  
Author(s):  
Haijing Guo ◽  
Jen-Hsuan Wei ◽  
Joachim Seemann
Keyword(s):  
Cell Fate ◽  
Spindle Pole ◽  
Substrate Preference ◽  
Spindle Orientation ◽  
Microtubule Network ◽  
Correct Orientation ◽  
Astral Microtubule ◽  
Importin Α ◽  
Microtubule Formation ◽  
Microtubule Growth

AbstractSpindle orientation is important in multiple developmental processes as it determines cell fate and function. The correct orientation of the mitotic spindle depends on the assembly of a proper astral microtubule network. Here, we report that the spindle assembly factor TPX2 regulates the astral microtubule network. TPX2 in the spindle pole area is activated by GM130 on mitotic Golgi membranes to promote astral microtubule growth. GM130 relieves TPX2 inhibition by competing for importin α binding. During mitosis, phosphorylation of importin α at Serine 62 by Cdk1 switches its substrate preference from TPX2 to GM130, thereby enabling competition-based activation. Importin α S62A impedes local TPX2 activation and compromises astral microtubule formation, ultimately resulting in misoriented spindles. Blocking the GM130-importin α-TPX2 pathway impairs astral microtubule growth. Our results reveal a novel role for TPX2 in the organization of astral microtubules. Furthermore, we show that the substrate preference of the important mitotic modulator importin α is regulated by Cdk1 phosphorylation.

scholarly journals Importin α phosphorylation promotes TPX2 activation by GM130 to control astral microtubules and spindle orientation

2021 ◽  
Vol 134 (4) ◽  
pp. jcs258356
Author(s):  
Haijing Guo ◽  
Jen-Hsuan Wei ◽  
Yijun Zhang ◽  
Joachim Seemann
Keyword(s):  
Cell Fate ◽  
Spindle Pole ◽  
Substrate Preference ◽  
Spindle Orientation ◽  
Microtubule Network ◽  
Astral Microtubule ◽  
Assembly Factor ◽  
Importin Α ◽  
Microtubule Growth ◽  
And Function

ABSTRACTSpindle orientation is important in multiple developmental processes as it determines cell fate and function. The orientation of the spindle depends on the assembly of a proper astral microtubule network. Here, we report that the spindle assembly factor TPX2 regulates astral microtubules. TPX2 in the spindle pole area is activated by GM130 (GOLGA2) on Golgi membranes to promote astral microtubule growth. GM130 relieves TPX2 inhibition by competing for importin α1 (KPNA2) binding. Mitotic phosphorylation of importin α at serine 62 (S62) by CDK1 switches its substrate preference from TPX2 to GM130, thereby enabling competition-based activation. Importin α S62A mutation impedes local TPX2 activation and compromises astral microtubule formation, ultimately resulting in misoriented spindles. Blocking the GM130–importin α–TPX2 pathway impairs astral microtubule growth. Our results reveal a novel role for TPX2 in the organization of astral microtubules. Furthermore, we show that the substrate preference of the important mitotic modulator importin α is regulated by CDK1-mediated phosphorylation.

scholarly journals Reorientation of Mispositioned Spindles in Short Astral Microtubule Mutantspc72Δ Is Dependent on Spindle Pole Body Outer Plaque and Kar3 Motor Protein

2002 ◽  
Vol 13 (4) ◽  
pp. 1366-1380 ◽  
Author(s):  
Dominic Hoepfner ◽  
Florian Schaerer ◽  
Arndt Brachat ◽  
Achim Wach ◽  
Peter Philippsen
Keyword(s):  
Spindle Pole Body ◽  
Time Lapse ◽  
Nuclear Migration ◽  
Spindle Pole ◽  
Astral Microtubule ◽  
Spindle Pole Bodies ◽  
Microtubule Motor ◽  
Microtubule Formation ◽  
Mother Cells

Nuclear migration and positioning in Saccharomyces cerevisiae depend on long astral microtubules emanating from the spindle pole bodies (SPBs). Herein, we show by in vivo fluorescence microscopy that cells lacking Spc72, the SPB receptor of the cytoplasmic γ-tubulin complex, can only generate very short (<1 μm) and unstable astral microtubules. Consequently, nuclear migration to the bud neck and orientation of the anaphase spindle along the mother-bud axis are absent in these cells. However,SPC72 deletion is not lethal because elongated but misaligned spindles can frequently reorient in mother cells, permitting delayed but otherwise correct nuclear segregation. High-resolution time-lapse sequences revealed that this spindle reorientation was most likely accomplished by cortex interactions of the very short astral microtubules. In addition, a set of double mutants suggested that reorientation was dependent on the SPB outer plaque and the astral microtubule motor function of Kar3 but not Kip2/Kip3/Dhc1, or the cortex components Kar9/Num1. Our observations suggest that Spc72 is required for astral microtubule formation at the SPB half-bridge and for stabilization of astral microtubules at the SPB outer plaque. In addition, our data exclude involvement of Spc72 in spindle formation and elongation functions.

scholarly journals Dynamic Positioning of Mitotic Spindles in Yeast:

2000 ◽  
Vol 11 (11) ◽  
pp. 3949-3961 ◽  
Author(s):  
Elaine Yeh ◽  
Charlie Yang ◽  
Elaine Chin ◽  
Paul Maddox ◽  
E. D. Salmon ◽  
...  
Keyword(s):  
Spindle Pole Body ◽  
Cytoplasmic Dynein ◽  
Spindle Pole ◽  
Nuclear Movement ◽  
Yeast Saccharomyces Cerevisiae ◽  
Anaphase Onset ◽  
Astral Microtubule ◽  
Bud Neck ◽  
Microtubule Growth ◽  
Spindle Elongation

In the budding yeast Saccharomyces cerevisiae, movement of the mitotic spindle to a predetermined cleavage plane at the bud neck is essential for partitioning chromosomes into the mother and daughter cells. Astral microtubule dynamics are critical to the mechanism that ensures nuclear migration to the bud neck. The nucleus moves in the opposite direction of astral microtubule growth in the mother cell, apparently being “pushed” by microtubule contacts at the cortex. In contrast, microtubules growing toward the neck and within the bud promote nuclear movement in the same direction of microtubule growth, thus “pulling” the nucleus toward the bud neck. Failure of “pulling” is evident in cells lacking Bud6p, Bni1p, Kar9p, or the kinesin homolog, Kip3p. As a consequence, there is a loss of asymmetry in spindle pole body segregation into the bud. The cytoplasmic motor protein, dynein, is not required for nuclear movement to the neck; rather, it has been postulated to contribute to spindle elongation through the neck. In the absence of KAR9,dynein-dependent spindle oscillations are evident before anaphase onset, as are postanaphase dynein-dependent pulling forces that exceed the velocity of wild-type spindle elongation threefold. In addition, dynein-mediated forces on astral microtubules are sufficient to segregate a 2N chromosome set through the neck in the absence of spindle elongation, but cytoplasmic kinesins are not. These observations support a model in which spindle polarity determinants (BUD6, BNI1, KAR9) and cytoplasmic kinesin (KIP3) provide directional cues for spindle orientation to the bud while restraining the spindle to the neck. Cytoplasmic dynein is attenuated by these spindle polarity determinants and kinesin until anaphase onset, when dynein directs spindle elongation to distal points in the mother and bud.

scholarly journals NuMA-microtubule interactions are critical for spindle orientation and the morphogenesis of diverse epidermal structures

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Lindsey Seldin ◽  
Andrew Muroyama ◽  
Terry Lechler
Keyword(s):  
Cell Fate ◽  
Mitotic Spindle ◽  
Cell Types ◽  
Epidermal Differentiation ◽  
Spindle Orientation ◽  
Direct Function ◽  
Spindle Positioning ◽  
Adult Mice ◽  
Neonatal Lethality ◽  
The Matrix

Mitotic spindle orientation is used to generate cell fate diversity and drive proper tissue morphogenesis. A complex of NuMA and dynein/dynactin is required for robust spindle orientation in a number of cell types. Previous research proposed that cortical dynein/dynactin was sufficient to generate forces on astral microtubules (MTs) to orient the spindle, with NuMA acting as a passive tether. In this study, we demonstrate that dynein/dynactin is insufficient for spindle orientation establishment in keratinocytes and that NuMA’s MT-binding domain, which targets MT tips, is also required. Loss of NuMA-MT interactions in skin caused defects in spindle orientation and epidermal differentiation, leading to neonatal lethality. In addition, we show that NuMA-MT interactions are also required in adult mice for hair follicle morphogenesis and spindle orientation within the transit-amplifying cells of the matrix. Loss of spindle orientation in matrix cells results in defective differentiation of matrix-derived lineages. Our results reveal an additional and direct function of NuMA during mitotic spindle positioning, as well as a reiterative use of spindle orientation in the skin to build diverse structures.

scholarly journals A Unique Set of Centrosome Proteins Requires Pericentrin for Spindle-Pole Localization and Spindle Orientation

2014 ◽  
Vol 24 (19) ◽  
pp. 2354
Author(s):  
Chun-Ting Chen ◽  
Heidi Hehnly ◽  
Qing Yu ◽  
Debby Farkas ◽  
Guoqiang Zheng ◽  
...  
Keyword(s):  
Spindle Pole ◽  
Spindle Orientation ◽  
Centrosome Proteins

scholarly journals The Rap1–Rgl–Ral signaling network regulates neuroblast cortical polarity and spindle orientation

2011 ◽  
Vol 195 (4) ◽  
pp. 553-562 ◽  
Author(s):  
Ana Carmena ◽  
Aljona Makarova ◽  
Stephan Speicher
Keyword(s):  
Cell Fate ◽  
Asymmetric Cell Division ◽  
Signaling Network ◽  
Spindle Orientation ◽  
Nucleotide Exchange ◽  
Loss Of Function ◽  
Axis Orientation ◽  
Division Axis ◽  
Guanosine Triphosphatase

A crucial first step in asymmetric cell division is to establish an axis of cell polarity along which the mitotic spindle aligns. Drosophila melanogaster neural stem cells, called neuroblasts (NBs), divide asymmetrically through intrinsic polarity cues, which regulate spindle orientation and cortical polarity. In this paper, we show that the Ras-like small guanosine triphosphatase Rap1 signals through the Ral guanine nucleotide exchange factor Rgl and the PDZ protein Canoe (Cno; AF-6/Afadin in vertebrates) to modulate the NB division axis and its apicobasal cortical polarity. Rap1 is slightly enriched at the apical pole of metaphase/anaphase NBs and was found in a complex with atypical protein kinase C and Par6 in vivo. Loss of function and gain of function of Rap1, Rgl, and Ral proteins disrupt the mitotic axis orientation, the localization of Cno and Mushroom body defect, and the localization of cell fate determinants. We propose that the Rap1–Rgl–Ral signaling network is a novel mechanism that cooperates with other intrinsic polarity cues to modulate asymmetric NB division.

The Kar3p and Kip2p motors function antagonistically at the spindle poles to influence cytoplasmic microtubule numbers

1998 ◽  
Vol 111 (3) ◽  
pp. 295-301 ◽  
Author(s):  
A. Huyett ◽  
J. Kahana ◽  
P. Silver ◽  
X. Zeng ◽  
W.S. Saunders
Keyword(s):  
Molecular Motors ◽  
Motor Proteins ◽  
Single Gene ◽  
Intermediate Phenotype ◽  
Microtubule Network ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cytoplasmic Microtubule ◽  
Spindle Poles ◽  
Microtubule Motors ◽  
Microtubule Growth

Microtubules provide the substrate for intracellular trafficking by association with molecular motors of the kinesin and dynein superfamilies. Motor proteins are generally thought to function as force generating units for transport of various cargoes along the microtubule polymer. Recent work suggests additional roles for motor proteins in changing the structure of the microtubule network itself. We report here that in the budding yeast Saccharomyces cerevisiae microtubule motors have antagonistic effects on microtubule numbers and lengths. As shown previously, loss of the Kar3p motor stimulates cytoplasmic microtubule growth while loss of Kip2p leads to a sharp reduction in cytoplasmic microtubule numbers. Loss of both the Kip2p and Kar3p motors together in the same cell produces an intermediate phenotype, suggesting that these two motors act in opposition to control cytoplasmic microtubule density. A Kip2p-GFP fusion from single gene expression is most concentrated at the spindle poles, as shown previously for an epitope tagged Kar3p-HA, suggesting both of these motors act from the minus ends of the microtubules to influence microtubule numbers.

scholarly journals Cell shape and intercellular adhesion regulate mitotic spindle orientation

2019 ◽  
Vol 30 (19) ◽  
pp. 2458-2468 ◽  
Author(s):  
Jingchen Li ◽  
Longcan Cheng ◽  
Hongyuan Jiang
Keyword(s):  
Cell Division ◽  
Epithelial Cells ◽  
Cell Fate ◽  
Cell Shape ◽  
Intercellular Adhesion ◽  
Shape Anisotropy ◽  
Spindle Orientation ◽  
Mitotic Spindles ◽  
Strong Adhesion ◽  
Fate Decision

Cell division orientation plays an essential role in tissue morphogenesis and cell fate decision. Recent studies showed that either cell shape or adhesion geometry can regulate the orientation of mitotic spindles and thereby the cell division orientation. However, how they together regulate the spindle orientation remains largely unclear. In this work, we use a general computational model to investigate the competitive mechanism of determining the spindle orientation between cell shape and intercellular adhesion in epithelial cells. We find the spindle orientation is dominated by the intercellular adhesion when the cell shape anisotropy is small, but dominated by the cell shape when the shape anisotropy is large. A strong adhesion and moderate adhesive size can ensure the planar division of epithelial cells with large apico-basal elongation. We also find the spindle orientation could be perpendicular to the adhesive region when only one side of the cell is adhered to an E-cadherin–coated matrix. But after the cell is compressed, the spindle orientation is governed by the cell shape and the spindle will be parallel to the adhesive region when the cell shape anisotropy is large. Finally, we demonstrate the competition between cell shape and tricellular junctions can also effectively regulate the spindle orientation.

scholarly journals Cytokine receptor-Eb1 interaction couples cell polarity and fate during asymmetric cell division

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Cuie Chen ◽  
Ryan Cummings ◽  
Aghapi Mordovanakis ◽  
Alan J Hunt ◽  
Michael Mayer ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cell Division ◽  
Cell Fate ◽  
Cell Polarity ◽  
Adult Stem Cells ◽  
Asymmetric Cell Division ◽  
Cytokine Receptor ◽  
Spindle Orientation ◽  
Germline Stem Cells ◽  
Self Renewal

Asymmetric stem cell division is a critical mechanism for balancing self-renewal and differentiation. Adult stem cells often orient their mitotic spindle to place one daughter inside the niche and the other outside of it to achieve asymmetric division. It remains unknown whether and how the niche may direct division orientation. Here we discover a novel and evolutionary conserved mechanism that couples cell polarity to cell fate. We show that the cytokine receptor homolog Dome, acting downstream of the niche-derived ligand Upd, directly binds to the microtubule-binding protein Eb1 to regulate spindle orientation in Drosophila male germline stem cells (GSCs). Dome’s role in spindle orientation is entirely separable from its known function in self-renewal mediated by the JAK-STAT pathway. We propose that integration of two functions (cell polarity and fate) in a single receptor is a key mechanism to ensure an asymmetric outcome following cell division.

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