Loss of aMTOCs disrupts spindle pole Aurora A and assembly of the liquid-like meiotic spindle domain (LISD) in oocytes

Oocyte-specific Pericentrin (PCNT) knockdown in transgenic (Tg) mice disrupts acentriolar microtubule organizing center (aMTOC) formation, leading to spindle instability and error-prone meiotic division. Here, we show that PCNT-depleted oocytes lack phosphorylated Aurora A (pAURKA) at spindle poles, while overall levels are unaltered. To test aMTOC-associated AURKA function, MII control (WT) and Tg oocytes were briefly exposed to a specific inhibitor (MLN8237). Similar defects were observed in Tg and MLN8237-treated WT oocytes, including altered spindle structure, increased chromosome misalignment and impaired microtubule regrowth. Yet, AURKA inhibition had a limited effect on Tg oocytes, revealing a critical role for aMTOC-associated AURKA in regulating spindle stability. Notably, spindle instability was associated with disrupted γ-tubulin and lack of the liquid-like meiotic spindle domain (LISD) in Tg oocytes. Analysis of this Tg model provides the first evidence that LISD assembly depends expressly on aMTOC-associated AURKA, and that Ran-mediated spindle formation ensues without the LISD. These data support that loss of aMTOC-associated AURKA and failure of LISD assembly contribute to error-prone meiotic division in PCNT-depleted oocytes, underscoring the essential role of aMTOCs for spindle stability.

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A novel mitotic spindle pole component that originates from the cytoplasm during prophase.

The Journal of Cell Biology ◽

10.1083/jcb.103.5.1863 ◽

1986 ◽

Vol 103 (5) ◽

pp. 1863-1872 ◽

Cited By ~ 25

Author(s):

P R Sager ◽

N L Rothfield ◽

J M Oliver ◽

R D Berlin

Keyword(s):

Mitotic Spindle ◽

Spindle Pole ◽

Early Prophase ◽

Microtubule Organizing Center ◽

Spindle Poles ◽

Interphase Cells ◽

Organizing Center ◽

Mitotic Spindle Pole ◽

Pole Component

Several unique aspects of mitotic spindle formation have been revealed by investigation of an autoantibody present in the serum of a patient with the CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, schlerodacytyly, and telangiectasias) syndrome. This antibody was previously shown to label at the spindle poles of metaphase and anaphase cells and to be absent from interphase cells. We show here that the serum stained discrete cytoplasmic foci in early prophase cells and only later localized to the spindle poles. The cytoplasmic distribution of the antigen was also seen in nocodazole-arrested cells and prophase cells in populations treated with taxol. In normal and taxol-treated cells, the microtubules appeared to emanate from the cytoplasmic foci and polar stain, and in cells released from nocodazole block, microtubules regrew from antigen-containing centers. This characteristic distribution suggests that the antigen is part of a microtubule organizing center. Thus, we propose that a prophase originating polar antigen functions in spindle pole organization as a coalescing microtubule organizing center that is present only during mitosis. Characterization of the serum showed reactions with multiple proteins at 115, 110, 50, 36, 30, and 28 kD. However, affinity-eluted antibody from the 115/110-kD bands was shown to specifically label the spindle pole and cytosolic foci in prophase cells.

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subito Encodes a Kinesin-like Protein Required for Meiotic Spindle Pole Formation in Drosophila melanogaster

Genetics ◽

10.1093/genetics/160.4.1489 ◽

2002 ◽

Vol 160 (4) ◽

pp. 1489-1501 ◽

Cited By ~ 2

Author(s):

Kelly L Giunta ◽

Janet K Jang ◽

Elizabeth A Manheim ◽

Gayathri Subramanian ◽

Kim S McKim

Keyword(s):

Drosophila Melanogaster ◽

Spindle Pole ◽

Meiotic Spindle ◽

Microtubule Organizing Center ◽

Bipolar Spindle ◽

Microtubule Associated Proteins ◽

Organizing Center ◽

Associated Proteins ◽

Similar Phenotype ◽

Meiosis I

Abstract The female meiotic spindle lacks a centrosome or microtubule-organizing center in many organisms. During cell division, these spindles are organized by the chromosomes and microtubule-associated proteins. Previous studies in Drosophila melanogaster implicated at least one kinesin motor protein, NCD, in tapering the microtubules into a bipolar spindle. We have identified a second Drosophila kinesin-like protein, SUB, that is required for meiotic spindle function. At meiosis I in males and females, sub mutations affect only the segregation of homologous chromosomes. In female meiosis, sub mutations have a similar phenotype to ncd; even though chromosomes are joined by chiasmata they fail to segregate at meiosis I. Cytological analyses have revealed that sub is required for bipolar spindle formation. In sub mutations, we observed spindles that were unipolar, multipolar, or frayed with no defined poles. On the basis of these phenotypes and the observation that sub mutations genetically interact with ncd, we propose that SUB is one member of a group of microtubule-associated proteins required for bipolar spindle assembly in the absence of the centrosomes. sub is also required for the early embryonic divisions but is otherwise dispensable for most mitotic divisions.

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Meiotic Spindle Stability in Oocytes Is Dependent on Pericentrin, a Key Microtubule Organizing Center (MTOC)-Associated Protein.

Biology of Reproduction ◽

10.1093/biolreprod/81.s1.274 ◽

2009 ◽

Vol 81 (Suppl_1) ◽

pp. 274-274

Author(s):

Wei Ma ◽

Maria M. Viveiras

Keyword(s):

Meiotic Spindle ◽

Microtubule Organizing Center ◽

Organizing Center ◽

Spindle Stability

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The Msd1–Wdr8–Pkl1 complex anchors microtubule minus ends to fission yeast spindle pole bodies

The Journal of Cell Biology ◽

10.1083/jcb.201412111 ◽

2015 ◽

Vol 209 (4) ◽

pp. 549-562 ◽

Cited By ~ 30

Author(s):

Masashi Yukawa ◽

Chiho Ikebe ◽

Takashi Toda

Keyword(s):

Fission Yeast ◽

Critical Role ◽

Spindle Pole Body ◽

Spindle Pole ◽

Microtubule Organizing Center ◽

Spatiotemporal Regulation ◽

Spindle Pole Bodies ◽

Organizing Center ◽

Spindle Microtubules ◽

Insight Into

The minus ends of spindle microtubules are anchored to a microtubule-organizing center. The conserved Msd1/SSX2IP proteins are localized to the spindle pole body (SPB) and the centrosome in fission yeast and humans, respectively, and play a critical role in microtubule anchoring. In this paper, we show that fission yeast Msd1 forms a ternary complex with another conserved protein, Wdr8, and the minus end–directed Pkl1/kinesin-14. Individual deletion mutants displayed the identical spindle-protrusion phenotypes. Msd1 and Wdr8 were delivered by Pkl1 to mitotic SPBs, where Pkl1 was tethered through Msd1–Wdr8. The spindle-anchoring defect imposed by msd1/wdr8/pkl1 deletions was suppressed by a mutation of the plus end–directed Cut7/kinesin-5, which was shown to be mutual. Intriguingly, Pkl1 motor activity was not required for its anchoring role once targeted to the SPB. Therefore, spindle anchoring through Msd1–Wdr8–Pkl1 is crucial for balancing the Cut7/kinesin-5–mediated outward force at the SPB. Our analysis provides mechanistic insight into the spatiotemporal regulation of two opposing kinesins to ensure mitotic spindle bipolarity.

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Genetic interactions between CDC31 and KAR1, two genes required for duplication of the microtubule organizing center in Saccharomyces cerevisiae.

Genetics ◽

10.1093/genetics/137.2.407 ◽

1994 ◽

Vol 137 (2) ◽

pp. 407-422 ◽

Cited By ~ 8

Author(s):

E A Vallen ◽

W Ho ◽

M Winey ◽

M D Rose

Keyword(s):

Copy Number ◽

Gene Dosage ◽

Spindle Pole Body ◽

Direct Interaction ◽

Spindle Pole ◽

High Copy Number ◽

Temperature Sensitive ◽

Microtubule Organizing Center ◽

Recessive Mutations ◽

Organizing Center

Abstract KAR1 encodes an essential component of the yeast spindle pole body (SPB) that is required for karyogamy and SPB duplication. A temperature-sensitive mutation, kar1-delta 17, mapped to a region required for SPB duplication and for localization to the SPB. To identify interacting SPB proteins, we isolated 13 dominant mutations and 3 high copy number plasmids that suppressed the temperature sensitivity of kar1-delta 17. Eleven extragenic suppressor mutations mapped to two linkage groups, DSK1 and DSK2. The extragenic suppressors were specific for SPB duplication and did not suppress karyogamy-defective alleles. The major class, DSK1, consisted of mutations in CDC31. CDC31 is required for SPB duplication and encodes a calmodulin-like protein that is most closely related to caltractin/centrin, a protein associated with the Chlamydomonas basal body. The high copy number suppressor plasmids contained the wild-type CDC31 gene. One CDC31 suppressor allele conferred a temperature-sensitive defect in SPB duplication, which was counter-suppressed by recessive mutations in KAR1. In spite of the evidence for a direct interaction, the strongest CDC31 alleles, as well as both DSK2 alleles, suppressed a complete deletion of KAR1. However, the CDC31 alleles also made the cell supersensitive to KAR1 gene dosage, arguing against a simple bypass mechanism of suppression. We propose a model in which Kar1p helps localize Cdc31p to the SPB and that Cdc31p then initiates SPB duplication via interaction with a downstream effector.

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Mobility, Microtubule Nucleation and Structure of Microtubule-organizing Centers in Multinucleated Hyphae ofAshbya gossypii

Molecular Biology of the Cell ◽

10.1091/mbc.e09-01-0063 ◽

2010 ◽

Vol 21 (1) ◽

pp. 18-28 ◽

Cited By ~ 29

Author(s):

Claudia Lang ◽

Sandrine Grava ◽

Tineke van den Hoorn ◽

Rhonda Trimble ◽

Peter Philippsen ◽

...

Keyword(s):

Spindle Pole Body ◽

Hyphal Growth ◽

Spindle Pole ◽

Microtubule Organizing Center ◽

Microtubule Nucleation ◽

Cytoplasmic Microtubule ◽

Organizing Center ◽

Cytoplasmic Side ◽

Independent Mode

We investigated the migration of multiple nuclei in hyphae of the filamentous fungus Ashbya gossypii. Three types of cytoplasmic microtubule (cMT)-dependent nuclear movements were characterized using live cell imaging: short-range oscillations (up to 4.5 μm/min), rotations (up to 180° in 30 s), and long-range nuclear bypassing (up to 9 μm/min). These movements were superimposed on a cMT-independent mode of nuclear migration, cotransport with the cytoplasmic stream. This latter mode is sufficient to support wild-type-like hyphal growth speeds. cMT-dependent nuclear movements were led by a nuclear-associated microtubule-organizing center, the spindle pole body (SPB), which is the sole site of microtubule nucleation in A. gossypii. Analysis of A. gossypii SPBs by electron microscopy revealed an overall laminar structure similar to the budding yeast SPB but with distinct differences at the cytoplasmic side. Up to six perpendicular and tangential cMTs emanated from a more spherical outer plaque. The perpendicular and tangential cMTs most likely correspond to short, often cortex-associated cMTs and to long, hyphal growth-axis–oriented cMTs, respectively, seen by in vivo imaging. Each SPB nucleates its own array of cMTs, and the lack of overlapping cMT arrays between neighboring nuclei explains the autonomous nuclear oscillations and bypassing observed in A. gossypii hyphae.

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The role of Aspergillus nidulans polo-like kinase PlkA in microtubule-organizing center control

Journal of Cell Science ◽

10.1242/jcs.256537 ◽

2021 ◽

Author(s):

Xiaolei Gao ◽

Saturnino Herrero ◽

Valentin Wernet ◽

Sylvia Erhardt ◽

Oliver Valerius ◽

...

Keyword(s):

Aspergillus Nidulans ◽

Cell Types ◽

Spindle Pole ◽

Receptor Protein ◽

Animal Cells ◽

Microtubule Organizing Center ◽

Spindle Pole Bodies ◽

Organizing Center ◽

Ring Complex ◽

Core Components

Centrosomes are important microtubule-organizing centers (MTOC) in animal cells. In addition, non-centrosomal MTOCs (ncMTOCs) were described in many cell types. Functional analogs of centrosomes in fungi are the spindle pole bodies (SPBs). In Aspergillus nidulans additional MTOCs were discovered at septa (sMTOC). Although the core components are conserved in both MTOCs, their composition and organization are different and dynamic. Here, we show that the polo-like kinase PlkA binds the γ-tubulin ring complex (γ-TuRC) receptor protein ApsB and contributes to targeting ApsB to both MTOCs. PlkA coordinates SPB outer plaque with sMTOC activities. PlkA kinase activity was required for astral MT formation involving ApsB recruitment. PlkA also interacted with the γ-TuRC inner plaque receptor protein PcpA. Mitosis was delayed without PlkA, and the PlkA protein was required for proper mitotic spindle morphology, although this function was independent of its catalytic activity. Our results suggest polo-like kinase as a regulator of MTOC activities and as a scaffolding unit through interaction with γ-tubulin ring complex receptors.

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