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

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

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

2021 ◽  
Author(s):  
Xiaotian Wang ◽  
Claudia Baumann ◽  
Rabindranath De La Fuente ◽  
Maria M. Viveiros
Keyword(s):  
Meiotic Division ◽  
Critical Role ◽  
Specific Inhibitor ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Aurora A ◽  
Microtubule Organizing Center ◽  
Spindle Poles ◽  
Organizing Center ◽  
Spindle Stability

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.

scholarly journals Reorganization of actin filaments by ADF/cofilin is involved in formation of microtubule structures during Xenopus oocyte maturation

2015 ◽  
Vol 26 (24) ◽  
pp. 4387-4400 ◽  
Author(s):  
Yuka Yamagishi ◽  
Hiroshi Abe
Keyword(s):  
Oocyte Maturation ◽  
Actin Filament ◽  
Actin Filaments ◽  
Xenopus Oocyte ◽  
Germinal Vesicle ◽  
Meiotic Spindle ◽  
Base Region ◽  
Microtubule Organizing Center ◽  
Cytoplasmic Actin ◽  
Organizing Center

We examined the reorganization of actin filaments and microtubules during Xenopus oocyte maturation. Surrounding the germinal vesicle (GV) in immature oocytes, the cytoplasmic actin filaments reorganized to accumulate beneath the vegetal side of the GV, where the microtubule-organizing center and transient microtubule array (MTOC-TMA) assembled, just before GV breakdown (GVBD). Immediately after GVBD, both Xenopus ADF/cofilin (XAC) and its phosphatase Slingshot (XSSH) accumulated into the nuclei and intranuclear actin filaments disassembled from the vegetal side with the shrinkage of the GV. As the MTOC-TMA developed well, cytoplasmic actin filaments were retained at the MTOC-TMA base region. Suppression of XAC dephosphorylation by anti-XSSH antibody injection inhibited both actin filament reorganization and proper formation and localization of both the MTOC-TMA and meiotic spindles. Stabilization of actin filaments by phalloidin also inhibited formation of the MTOC-TMA and disassembly of intranuclear actin filaments without affecting nuclear shrinkage. Nocodazole also caused the MTOC-TMA and the cytoplasmic actin filaments at its base region to disappear, which further impeded disassembly of intranuclear actin filaments from the vegetal side. XAC appears to reorganize cytoplasmic actin filaments required for precise assembly of the MTOC and, together with the MTOC-TMA, regulate the intranuclear actin filament disassembly essential for meiotic spindle formation.

scholarly journals Multiple pools of Protein Phosphatase 2A-B56 function to antagonize spindle assembly, promote kinetochore attachments and maintain cohesion in Drosophila Oocytes

2020 ◽  
Author(s):  
Janet K. Jang ◽  
Amy C. Gladstein ◽  
Arunika Das ◽  
Zachary L. Sisco ◽  
Kim S. McKim
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 2A ◽  
Spindle Assembly ◽  
Meiotic Spindle ◽  
Aurora B ◽  
Microtubule Organizing Center ◽  
Chromosomal Passenger ◽  
Organizing Center ◽  
Phosphatase 2A ◽  
Meiosis I

AbstractMeiosis in female oocytes lack centrosomes, the major microtubule-organizing center, which makes them especially vulnerable to aneuploidy. In the acentrosomal oocytes of Drosophila, meiotic spindle assembly depends on the chromosomal passenger complex (CPC). Aurora B is the catalytic component of the CPC while the remaining subunits regulate its localization. Using an inhibitor of Aurora B activity, Binucleine 2, we found that continuous Aurora B activity is required to maintain the oocyte spindle during meiosis I, and this activity is antagonized by phosphatases acting on spindle associated proteins such as kinesins. Protein Phosphatase 2A (PP2A) exists in two varieties, B55 and B56. While both antagonize Aurora B, B55 has only minor roles in meiosis I spindle function. The B56 subunit is encoded by two partially redundant paralogs in the Drosophila genome, wdb and wrd. Knocking down both paralogs showed that the B56 subunit is critical for maintaining sister chromatid cohesion, establishing end-on microtubule attachments, and the metaphase I arrest in oocytes. We found that WDB recruitment to the centromeres depends on BUBR1, MEI-S332, and kinetochore protein SPC105R. While BUBR1 has been shown previously to stabilize microtubule attachments in Drosophila oocytes, only SPC105R is required for cohesion maintenance during meiosis I. We propose that SPC105R promotes cohesion maintenance by recruiting two proteins that recruit PP2A, MEI-S332, and the Soronin homolog Dalmatian.

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

Genetics ◽  
2002 ◽  
Vol 160 (4) ◽  
pp. 1489-1501 ◽  
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.

scholarly journals Multiple pools of PP2A regulate spindle assembly, kinetochore attachments, and cohesion in Drosophila oocytes

2021 ◽  
Author(s):  
Janet K. Jang ◽  
Amy C. Gladstein ◽  
Arunika Das ◽  
Joanatta G. Shapiro ◽  
Zachary L. Sisco ◽  
...  
Keyword(s):  
Spindle Assembly ◽  
Meiotic Spindle ◽  
Aurora B ◽  
Microtubule Organizing Center ◽  
Oocyte Meiosis ◽  
Chromatid Cohesion ◽  
Chromosomal Passenger ◽  
Organizing Center ◽  
Phosphatase 2A ◽  
Meiosis I

Meiosis in female oocytes lacks centrosomes, the microtubule-organizing center. In Drosophila oocytes, meiotic spindle assembly depends on the chromosomal passenger complex (CPC). To investigate the mechanisms that regulate Aurora B activity, we examined the role of Protein Phosphatase 2A (PP2A) in oocyte meiosis. We found that both forms of PP2A, B55 and B56, antagonize the Aurora B spindle assembly function, suggesting that a balance between Aurora B and PP2A activity maintains the oocyte spindle during meiosis I. PP2A-B56, which is encoded by two partially redundant paralogs, wdb and wrd, is also required for maintaining sister chromatid cohesion, establishing end-on microtubule attachments, and the metaphase I arrest in oocytes. WDB recruitment to the centromeres depends on BUBR1, MEI-S332, and kinetochore protein SPC105R. While BUBR1 stabilizes microtubule attachments in Drosophila oocytes, it is not required for cohesion maintenance during meiosis I. We propose at least three populations of PP2A-B56 regulate meiosis, two of which depend on SPC105R and a third that is associated with the spindle.

Three-Dimensional reconstruction of isolated centrosomes by automated electron tomography

1994 ◽  
Vol 52 ◽  
pp. 310-311
Author(s):  
M.B. Braunfeld ◽  
M. Moritz ◽  
B.M. Alberts ◽  
J.W. Sedat ◽  
D.A. Agard
Keyword(s):  
Electron Tomography ◽  
Three Dimensional ◽  
Vital Role ◽  
Complex Nature ◽  
Animal Cells ◽  
Microtubule Organizing Center ◽  
Nucleation Sites ◽  
Dimensional Reconstruction ◽  
Organizing Center ◽  
Resolution Model

In animal cells, the centrosome functions as the primary microtubule organizing center (MTOC). As such the centrosome plays a vital role in determining a cell's shape, migration, and perhaps most importantly, its division. Despite the obvious importance of this organelle little is known about centrosomal regulation, duplication, or how it nucleates microtubules. Furthermore, no high resolution model for centrosomal structure exists.We have used automated electron tomography, and reconstruction techniques in an attempt to better understand the complex nature of the centrosome. Additionally we hope to identify nucleation sites for microtubule growth.Centrosomes were isolated from early Drosophila embryos. Briefly, after large organelles and debris from homogenized embryos were pelleted, the resulting supernatant was separated on a sucrose velocity gradient. Fractions were collected and assayed for centrosome-mediated microtubule -nucleating activity by incubating with fluorescently-labeled tubulin subunits. The resulting microtubule asters were then spun onto coverslips and viewed by fluorescence microscopy.

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