Kinetochore Fibers Are Not Involved in the Formation of the First Meiotic Spindle in Mouse Oocytes, but Control the Exit from the First Meiotic M Phase

1999 ◽  
Vol 146 (999) ◽  
pp. 999-12
Author(s):  
S. Brunet
Keyword(s):  
Meiotic Spindle ◽  
Mouse Oocytes ◽  
M Phase

scholarly journals Kinetochore Fibers Are Not Involved in the Formation of the First Meiotic Spindle in Mouse Oocytes, but Control the Exit from the First Meiotic M Phase

1999 ◽  
Vol 146 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Stéphane Brunet ◽  
Angélica Santa Maria ◽  
Philippe Guillaud ◽  
Denis Dujardin ◽  
Jacek Z. Kubiak ◽  
...  
Keyword(s):  
Polar Body ◽  
Meiotic Spindle ◽  
Homologous Chromosomes ◽  
Mouse Oocytes ◽  
Sister Chromatids ◽  
M Phase ◽  
Continuous Presence ◽  
Set Up ◽  
Polar Body Extrusion ◽  
Reductional Division

During meiosis, two successive divisions occur without any intermediate S phase to produce haploid gametes. The first meiotic division is unique in that homologous chromosomes are segregated while the cohesion between sister chromatids is maintained, resulting in a reductional division. Moreover, the duration of the first meiotic M phase is usually prolonged when compared with mitotic M phases lasting 8 h in mouse oocytes. We investigated the spindle assembly pathway and its role in the progression of the first meiotic M phase in mouse oocytes. During the first 4 h, a bipolar spindle forms and the chromosomes congress near the equatorial plane of the spindle without stable kinetochore– microtubule end interactions. This late prometaphase spindle is then maintained for 4 h with chromosomes oscillating in the central region of the spindle. The kinetochore–microtubule end interactions are set up at the end of the first meiotic M phase (8 h after entry into M phase). This event allows the final alignment of the chromosomes and exit from metaphase. The continuous presence of the prometaphase spindle is not required for progression of the first meiotic M phase. Finally, the ability of kinetochores to interact with microtubules is acquired at the end of the first meiotic M phase and determines the timing of polar body extrusion.

scholarly journals APCFZR1 prevents nondisjunction in mouse oocytes by controlling meiotic spindle assembly timing

2012 ◽  
Vol 23 (20) ◽  
pp. 3970-3981 ◽  
Author(s):  
Janet E. Holt ◽  
Simon I. R. Lane ◽  
Phoebe Jennings ◽  
Irene García-Higuera ◽  
Sergio Moreno ◽  
...  
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Cell ◽  
Meiotic Spindle ◽  
Genome Integrity ◽  
Mitotic Cell Cycle ◽  
Anaphase Promoting Complex ◽  
Mouse Oocytes ◽  
M Phase ◽  
Chromosome Nondisjunction

FZR1 is an anaphase-promoting complex (APC) activator best known for its role in the mitotic cell cycle at M-phase exit, in G1, and in maintaining genome integrity. Previous studies also established that it prevents meiotic resumption, equivalent to the G2/M transition. Here we report that mouse oocytes lacking FZR1 undergo passage through meiosis I that is accelerated by ∼1 h, and this is due to an earlier onset of spindle assembly checkpoint (SAC) satisfaction and APCCDC20 activity. However, loss of FZR1 did not compromise SAC functionality; instead, earlier SAC satisfaction was achieved because the bipolar meiotic spindle was assembled more quickly in the absence of FZR1. This novel regulation of spindle assembly by FZR1 led to premature bivalent attachment to microtubules and loss of kinetochore-bound MAD2. Bivalents, however, were observed to congress poorly, leading to nondisjunction rates of 25%. We conclude that in mouse oocytes FZR1 controls the timing of assembly of the bipolar spindle and in so doing the timing of SAC satisfaction and APCCDC20 activity. This study implicates FZR1 as a major regulator of prometaphase whose activity helps to prevent chromosome nondisjunction.

scholarly journals Cell cycle modification during the transitions between meiotic M-phases in mouse oocytes

1992 ◽  
Vol 102 (3) ◽  
pp. 457-467 ◽  
Author(s):  
J.Z. Kubiak ◽  
M. Weber ◽  
G. Geraud ◽  
B. Maro
Keyword(s):  
Kinase Activity ◽  
Polar Body ◽  
Metaphase Arrest ◽  
Phosphorylated Proteins ◽  
Mouse Oocytes ◽  
Sequence Of Events ◽  
M Phase ◽  
Second Polar Body ◽  
Polar Body Extrusion ◽  
Centrosomal Proteins

When metaphase II-arrested mouse oocytes (M II) are activated very soon after ovulation, they respond abortively by second polar body extrusion followed by another metaphase arrest (metaphase III, M III; Kubiak, 1989). The M II/M III transition resembles the natural transition between the first and second meiotic metaphases (M I/M II). We observed that a similar sequence of events takes place during these two transitions: after anaphase, a polar body is extruded, the microtubules of the midbody disappear rapidly and a new metaphase spindle forms. The MPM-2 monoclonal antibody (which reacts with phosphorylated proteins associated with the centrosome during M-phase) stains discrete foci of peri-centriolar material only in metaphase arrested oocytes; during both transitional periods, a diffuse staining is observed, suggesting that these centrosomal proteins are dephosphorylated, as in a normal interphase. However, the chromosomes always remain condensed and an interphase network of microtubules is never observed during the transitional periods. Incorporation of 32P into proteins increases specifically during the transitional periods. Pulse-chase experiments, after labeling of the oocytes in M phase with 32P, showed that a 62 kDa phosphoprotein band disappears at the time of polar body extrusion. Histone H1 kinase activity (which reflects the activity of the maturation promoting factor) drops during both transitional periods to the level characteristic of interphase and then increases when the new spindle forms. Both the M I/M II and M II/M III transitions require protein synthesis as demonstrated by the effect of puromycin. These results suggest that the two M-phase/M-phase transitions are probably driven by the same molecular mechanism.

scholarly journals Meiotic spindle morphogenesis in in vivo and in vitro matured mouse oocytes: insights into the relationship between nuclear and cytoplasmic quality

2004 ◽  
Vol 19 (12) ◽  
pp. 2889-2899 ◽  
Author(s):  
Alexandra Sanfins ◽  
Carlos E. Plancha ◽  
Eric W. Overstrom ◽  
David F. Albertini
Keyword(s):  
Meiotic Spindle ◽  
Mouse Oocytes ◽  
The Relationship

WHAMM is required for meiotic spindle migration and asymmetric cytokinesis in mouse oocytes

2012 ◽  
Vol 139 (4) ◽  
pp. 525-534 ◽  
Author(s):  
Xin Huang ◽  
Lu Ding ◽  
Rui Pan ◽  
Peng-Fei Ma ◽  
Pan-Pan Cheng ◽  
...  
Keyword(s):  
Meiotic Spindle ◽  
Mouse Oocytes ◽  
Asymmetric Cytokinesis

Sulphydryl reagent iodoacetamide inhibits progression of meiosis and sperm transformation in mouse oocytes fertilised in vitro

Zygote ◽  
1995 ◽  
Vol 3 (1) ◽  
pp. 75-79
Author(s):  
Marek Maleszewski
Keyword(s):  
Early Stage ◽  
Blocking Agent ◽  
Sperm Nucleus ◽  
Meiotic Spindle ◽  
Thiol Groups ◽  
Mouse Oocytes

SummaryThe effect of iodoacetamide (IA), a sulphydryl blocking agent, on fertilisation in the mouse was examined by transferring zona-free oocytes into IA (500 μM)-containing medium at various times after insemination. When inseminated oocytes were transferred into IA medium 10 min after insemination, the oocyte chromosomes remained aggregated in one or two masses and the sperm nucleus failed to decondense. When oocytes were transferred during the second meiosis, oocytes meiosis was more or less arrested. The sperm nucleus decondensed but remained blocked at an early stage of decondensation. These observations suggest that thiol groups in the oocyte's cytoplasm and perhaps microtubules of the meiotic spindle play crucial roles in the completion of meiosis and the transformation of sperm nucleus into pronucleus.

scholarly journals Cdc4 phospho-degrons allow differential regulation of Ame1CENP-U protein stability across the cell cycle

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Miriam Böhm ◽  
Kerstin Killinger ◽  
Alexander Dudziak ◽  
Pradeep Pant ◽  
Karolin Jänen ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Building Blocks ◽  
Meiotic Spindle ◽  
Dependent Manner ◽  
Physiological Importance ◽  
Kinetochore Assembly ◽  
Ubiquitin Ligase Complex ◽  
M Phase ◽  
Novel Strategy ◽  
Cycle Dependent

Kinetochores are multi-subunit protein assemblies that link chromosomes to microtubules of the mitotic and meiotic spindle. It is still poorly understood how efficient, centromere-dependent kinetochore assembly is accomplished from hundreds of individual protein building blocks in a cell cycle dependent manner. Here, by combining comprehensive phosphorylation analysis of native Ctf19CCAN subunits with biochemical and functional assays in the model system budding yeast, we demonstrate that Cdk1 phosphorylation activates phospho-degrons on the essential subunit Ame1CENP-U which are recognized by the E3 ubiquitin ligase complex SCF-Cdc4. Gradual phosphorylation of degron motifs culminates in M-Phase and targets the protein for degradation. Binding of the Mtw1Mis12 complex shields the proximal phospho-degron, protecting kinetochore-bound Ame1 from the degradation machinery. Artificially increasing degron strength partially suppresses the temperature-sensitivity of a cdc4 mutant, while overexpression of Ame1-Okp1 is toxic in SCF mutants, demonstrating the physiological importance of this mechanism. We propose that phospho-regulated clearance of excess CCAN subunits facilitates efficient centromere-dependent kinetochore assembly. Our results suggest a novel strategy for how phospho-degrons can be used to regulate the assembly of multi-subunit complexes.

scholarly journals CEP215 and AURKA regulate spindle pole focusing and aMTOC organization in mouse oocytes

Reproduction ◽  
2020 ◽  
Vol 159 (3) ◽  
pp. 261-274
Author(s):  
Xiaotian Wang ◽  
Claudia Baumann ◽  
Rabindranath De La Fuente ◽  
Maria M Viveiros
Keyword(s):  
Critical Role ◽  
Super Resolution ◽  
Aurora Kinase ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Dependent Manner ◽  
Aurora Kinase A ◽  
Mouse Oocytes ◽  
Kinase A

Acentriolar microtubule-organizing centers (aMTOCs) play a critical role in stable meiotic spindle assembly in oocytes, necessary for accurate chromosome segregation. Yet, there is a limited understanding of the essential regulatory components of these unique MTOCs. In somatic cells, CEP215 (Centrosomal Protein 215) serves as an important regulator of centrosome maturation and spindle organization. Here, we assessed whether it has a similar function in mouse oocytes. CEP215 was detected in oocyte lysates and specifically localized to aMTOCs throughout the progression of meiosis in a pericentrin-dependent manner. Super-resolution microscopy revealed CEP215 co-localization with pericentrin and a unique pore/ring-like structural organization of aMTOCs. Interestingly, inhibition of Aurora Kinase A in either MI or MII-stage oocytes resulted in a striking loss of the ring-like aMTOC organization and pronounced CEP215 clustering at spindle poles, as well as shorter spindles with highly focused poles. In vitro siRNA-mediated transcript knockdown effectively reduced CEP215 in approximately 85% of the oocytes. Maturation rates to MII were similar in the Cep215 siRNA and injected controls; however, a high percentage (~40%) of the Cep215-knockdown oocytes showed notable variations in spindle pole focusing. Surprisingly, pericentrin and γ-tubulin localization and fluorescence intensity at aMTOCs were unaltered in knockdown oocytes, contrasting with mitotic cells where CEP215 depletion reduced γ-tubulin at centrosomes. Our results demonstrate that CEP215 is a functional component of oocyte aMTOCs and participates in the regulation of meiotic spindle pole focusing. Moreover, these studies reveal a vital role for Aurora Kinase A activity in the maintenance of aMTOC organization in oocytes.

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