scholarly journals Assembly and Positioning of the Oocyte Meiotic Spindle

2018 ◽  
Vol 34 (1) ◽  
pp. 381-403 ◽  
Author(s):  
Binyam Mogessie ◽  
Kathleen Scheffler ◽  
Melina Schuh
Keyword(s):  
Menstrual Cycle ◽  
Recent Work ◽  
Meiotic Division ◽  
Polar Body ◽  
Mitotic Division ◽  
Model System ◽  
Small Cell ◽  
Meiotic Spindle ◽  
Polar Body Extrusion ◽  
Shed Light

Fertilizable eggs develop from diploid precursor cells termed oocytes. Once every menstrual cycle, an oocyte matures into a fertilizable egg in the ovary. To this end, the oocyte eliminates half of its chromosomes into a small cell termed a polar body. The egg is then released into the Fallopian tube, where it can be fertilized. Upon fertilization, the egg completes the second meiotic division, and the mitotic division of the embryo starts. This review highlights recent work that has shed light on the cytoskeletal structures that drive the meiotic divisions of the oocyte in mammals. In particular, we focus on how mammalian oocytes assemble a microtubule spindle in the absence of centrosomes, how they position the spindle in preparation for polar body extrusion, and how the spindle segregates the chromosomes. We primarily focus on mouse oocytes as a model system but also highlight recent insights from human oocytes.

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 Sequential actin-based pushing forces drive meiosis I chromosome migration and symmetry breaking in oocytes

2013 ◽  
Vol 200 (5) ◽  
pp. 567-576 ◽  
Author(s):  
Kexi Yi ◽  
Boris Rubinstein ◽  
Jay R. Unruh ◽  
Fengli Guo ◽  
Brian D. Slaughter ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Cytoplasmic Streaming ◽  
Feedback Loop ◽  
Polar Body ◽  
Meiotic Spindle ◽  
Directed Motion ◽  
Family Protein ◽  
Polar Body Extrusion ◽  
Spindle Position ◽  
Meiosis I

Polar body extrusion during oocyte maturation is critically dependent on asymmetric positioning of the meiotic spindle, which is established through migration of the meiosis I (MI) spindle/chromosomes from the oocyte interior to a subcortical location. In this study, we show that MI chromosome migration is biphasic and driven by consecutive actin-based pushing forces regulated by two actin nucleators, Fmn2, a formin family protein, and the Arp2/3 complex. Fmn2 was recruited to endoplasmic reticulum structures surrounding the MI spindle, where it nucleated actin filaments to initiate an initially slow and poorly directed motion of the spindle away from the cell center. A fast and highly directed second migration phase was driven by actin-mediated cytoplasmic streaming and occurred as the chromosomes reach a sufficient proximity to the cortex to activate the Arp2/3 complex. We propose that decisive symmetry breaking in mouse oocytes results from Fmn2-mediated perturbation of spindle position and the positive feedback loop between chromosome signal-induced Arp2/3 activation and Arp2/3-orchestrated cytoplasmic streaming that transports the chromosomes.

Participation of the ubiquitin-proteasome pathway in rat oocyte activation

Zygote ◽  
2005 ◽  
Vol 13 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Xin Tan ◽  
An Peng ◽  
Yong-Chao Wang ◽  
Yue Wang ◽  
Qing-Yuan Sun
Keyword(s):  
Meiotic Division ◽  
Polar Body ◽  
Meiotic Spindle ◽  
Oocyte Activation ◽  
Parthenogenetic Activation ◽  
Ubiquitin Proteasome Pathway ◽  
Ubiquitin Proteasome ◽  
Proteasome Pathway ◽  
Second Polar Body

The role of the ubiquitin-proteasome pathway (UPP) in mitosis is well known. However, its role in meiotic division is still poorly documented, especially in the activation of mammalian oocytes. In this study, the role of proteasome in the spontaneous and parthenogenetic activation of rat oocytes was investigated. We found that ALLN, an inhibitor of proteasome, when applied to metaphase II oocytes, inhibited spontaneous activation, blocked extrusion of the second polar body (PB) and caused the withdrawal of the partially extruded second PB. ALLN also inhibited the parthenogenetic activation induced by cycloheximide, but had no effect on the formation of pronuclei in activated eggs. In metaphase and anaphase, ubiquitin and proteasome localized to the meiotic spindle, concentrating on both sides of the oocyte–second PB boundary during PB extrusion. This pattern of cellular distribution suggests that UPP may have a role in regulating nuclear division and cytokinesis. Ubiquitin was seen to form a ring around the pronucleus, whereas proteasome was evenly distributed in the pronuclear region. Taken together, our results indicate that (1) UPP is required for the transitions of oocytes from metaphase II to anaphase II and from anaphase II to the end of meiosis; and (2) the UPP plays a role in cytokinesis of the second meiotic division.

scholarly journals AIR-2: An Aurora/Ipl1-related Protein Kinase Associated with Chromosomes and Midbody Microtubules Is Required for Polar Body Extrusion and Cytokinesis in Caenorhabditis elegans Embryos

1998 ◽  
Vol 143 (6) ◽  
pp. 1635-1646 ◽  
Author(s):  
Jill M. Schumacher ◽  
Andy Golden ◽  
Peter J. Donovan
Keyword(s):  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Polar Body ◽  
Mitotic Division ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Cell Cycles ◽  
Polar Bodies ◽  
Multiple Cell ◽  
Polar Body Extrusion

An emerging family of kinases related to the Drosophila Aurora and budding yeast Ipl1 proteins has been implicated in chromosome segregation and mitotic spindle formation in a number of organisms. Unlike other Aurora/Ipl1-related kinases, the Caenorhabditis elegans orthologue, AIR-2, is associated with meiotic and mitotic chromosomes. AIR-2 is initially localized to the chromosomes of the most mature prophase I–arrested oocyte residing next to the spermatheca. This localization is dependent on the presence of sperm in the spermatheca. After fertilization, AIR-2 remains associated with chromosomes during each meiotic division. However, during both meiotic anaphases, AIR-2 is present between the separating chromosomes. AIR-2 also remains associated with both extruded polar bodies. In the embryo, AIR-2 is found on metaphase chromosomes, moves to midbody microtubules at anaphase, and then persists at the cytokinesis remnant. Disruption of AIR-2 expression by RNA- mediated interference produces entire broods of one-cell embryos that have executed multiple cell cycles in the complete absence of cytokinesis. The embryos accumulate large amounts of DNA and microtubule asters. Polar bodies are not extruded, but remain in the embryo where they continue to replicate. The cytokinesis defect appears to be late in the cell cycle because transient cleavage furrows initiate at the proper location, but regress before the division is complete. Additionally, staining with a marker of midbody microtubules revealed that at least some of the components of the midbody are not well localized in the absence of AIR-2 activity. Our results suggest that during each meiotic and mitotic division, AIR-2 may coordinate the congression of metaphase chromosomes with the subsequent events of polar body extrusion and cytokinesis.

scholarly journals Cytoplasmic Microtubule Organizing Centers Regulate Meiotic Spindle Positioning in Mouse Oocyte

2020 ◽  
Author(s):  
Daniela Londono Vasquez ◽  
Katherine Rodriguez-Lukey ◽  
Susanta K. Behura ◽  
Ahmed Z. Balboula
Keyword(s):  
Polar Body ◽  
Spindle Pole ◽  
Meiotic Spindle ◽  
Cytoplasmic Microtubule ◽  
Spindle Positioning ◽  
Nuclear Envelope Breakdown ◽  
Oocyte Meiosis ◽  
Polar Bodies ◽  
Polar Body Extrusion

ABSTRACTDuring oocyte meiosis, migration of the spindle and its positioning must be tightly regulated to ensure elimination of the polar bodies and provide developmentally competent euploid eggs. Although the role of F-actin in regulating these critical processes has been studied extensively, little is known whether microtubules (MTs) participate in regulating these processes. Here, we characterize a pool of MTOCs in the oocyte that does not contribute to spindle assembly but instead remains free in the cytoplasm during metaphase I (metaphase cytoplasmic MTOCs; mcMTOCs). In contrast to spindle pole MTOCs, which primarily originate from the perinuclear region in prophase I, the mcMTOCs are found near the cortex of the oocyte. At nuclear envelope breakdown, they exhibit robust nucleation of MTs, which diminishes during polar body extrusion before returning robustly during metaphase II. The asymmetric positioning of the mcMTOCs provides the spindle with a MT-based anchor line to the cortex opposite the site of polar body extrusion. Depletion of mcMTOCs, by laser ablation, or manipulating their numbers, through autophagy inhibition, revealed that the mcMTOCs are required to regulate the timely migration and positioning of the spindle in meiosis. We discuss how forces exerted by F-actin in mediating movement of the spindle to the oocyte cortex are balanced by MT-mediated forces from the mcMTOCs to ensure spindle positioning and timely spindle migration.

scholarly journals C. elegans CLASP/CLS-2 negatively regulates membrane ingression throughout the oocyte cortex and is required for polar body extrusion

2020 ◽  
Author(s):  
Aleesa J. Schlientz ◽  
Bruce Bowerman
Keyword(s):  
Polar Body ◽  
Spindle Assembly ◽  
Meiotic Spindle ◽  
Contractile Apparatus ◽  
Contractile Ring ◽  
C Elegans ◽  
Cell Divisions ◽  
Polar Bodies ◽  
Polar Body Extrusion ◽  
The Relationship

AbstractThe requirements for oocyte meiotic cytokinesis during polar body extrusion are not well understood. In particular, the relationship between the oocyte meiotic spindle and polar body contractile ring dynamics remains largely unknown. We have used live cell imaging and spindle assembly defective mutants lacking the function of CLASP/CLS-2, kinesin-12/KLP-18, or katanin/MEI-1 to investigate the relationship between meiotic spindle structure and polar body extrusion in C. elegans oocytes. We show that spindle bipolarity and chromosome segregation are not required for polar body contractile ring formation and chromosome extrusion in klp-18 mutants, but oocytes with severe spindle assembly defects due to loss of CLS-2 or MEI-1 have penetrant and distinct polar body extrusion defects: CLS-2 is required early for contractile ring assembly or stability, while MEI-1 is required later for contractile ring constriction. We also show that CLS-2 negatively regulates membrane ingression throughout the oocyte cortex during meiosis I, and we explore the relationship between global cortical dynamics and oocyte meiotic cytokinesis.Author SummaryThe precursor cells that produce gametes—sperm and eggs in animals—have two copies of each chromosome, one from each parent. These precursors undergo specialized cell divisions that leave each gamete with only one copy of each chromosome; defects that produce incorrect chromosome number cause severe developmental abnormalities. In oocytes, these cell divisions are highly asymmetric, with extra chromosomes discarded into small membrane bound polar bodies, leaving one chromosome set within the much larger oocyte. How oocytes assemble the contractile apparatus that pinches off polar bodies remains poorly understood. To better understand this process, we have used the nematode Caenorhabditis elegans to investigate the relationship between the bipolar structure that separates oocyte chromosomes, called the spindle, and assembly of the contractile apparatus that pinches off polar bodies. We used a comparative approach, examining this relationship in three spindle assembly defective mutants. Bipolar spindle assembly and chromosome separation were not required for polar body extrusion, as it occurred normally in mutants lacking a protein called KLP-18. However, mutants lacking the protein CLS-2 failed to assemble the contractile apparatus, while mutants lacking the protein MEI-1 assembled a contractile apparatus that failed to fully constrict. We also found that CLS-2 down-regulates membrane ingression throughout the oocyte surface, and we explored the relationship between oocyte membrane dynamics and polar body extrusion.

Genetically identical parthenogenetic mouse embryos produced by inhibition of the first meiotic cleavage with cytochalasin D

Development ◽  
1991 ◽  
Vol 111 (3) ◽  
pp. 763-769 ◽  
Author(s):  
J. Kubiak ◽  
A. Paldi ◽  
M. Weber ◽  
B. Maro
Keyword(s):  
Meiotic Division ◽  
Polar Body ◽  
Blastocyst Stage ◽  
Cytochalasin D ◽  
Meiotic Spindle ◽  
Glucose Phosphate ◽  
First Polar Body ◽  
Histone Kinase ◽  
Parthenogenetic Mouse Embryos ◽  
Parthenogenetic Embryos

The microfilament inhibitor cytochalasin D inhibits extrusion of the first polar body when present during the first meiotic division of mouse oocytes; however, it does not interfere with anaphase movement of chromosomes, and thus induces the formation of tetraploid oocytes. After the separation of chromosomes in anaphase, two spindles start to assemble. However, they merge rapidly and a single meiotic spindle forms. During the transition between metaphase I and metaphase II, in the presence of cytochalasin D, a drop in histone kinase activity takes place demonstrating a transitional decrease in the activity of the maturation promoting factor. These oocytes can be activated parthenogenetically a few hours after washing out the inhibitor. After completion of the second meiotic division and extrusion of a polar body, they contain a diploid number of chromosomes. They are genetically identical to each other and to their mother. Such eggs develop to the blastocyst stage and can implant in the uteri of foster mothers. Most of these fetuses die before the 9th day of gestation, as do diploid control fetuses treated with cytochalasin D during the second meiotic division. The heterozygous state of the experimental embryos obtained after activation of eggs recovered from heterozygous females and treated with cytochalasin D during the first meiotic division was confirmed using a glucose-phosphate isomerase assay. This technique allows the production of genetic clones of parthenogenetic embryos by simple means.

scholarly journals Mitochondrial activity and cytoskeleton organization in three pronuclei oocytes after intracytoplasmic sperm injection

Zygote ◽  
2018 ◽  
Vol 26 (4) ◽  
pp. 319-325
Author(s):  
Tuğba Kotil ◽  
M. Ertan Kervancıoğlu ◽  
Gülçin Ekter Kanten ◽  
Gülden Tunalı ◽  
Seyhun Solakoğlu
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Intracytoplasmic Sperm Injection ◽  
Mitochondrial Membrane ◽  
Polar Body ◽  
Meiotic Spindle ◽  
Mitochondrial Activity ◽  
Electron Microscopic ◽  
Second Polar Body ◽  
Polar Body Extrusion

SummaryDigyny, the presence of a third pronucleus due to the failure of second polar body extrusion, is problematic after intracytoplasmic sperm injection (ICSI) practices. Mitochondria have critical roles such as production of adenosine triphosphate (ATP) and regulation of Ca2+ homeostasis during oocyte maturation, fertilization and the following development, while the regulation of meiotic spindle formation, chromosome segregation, pronuclear apposition and cytokinesis is closely associated with the cytoskeleton. In this study, mitochondrial membrane potential, distribution of F-actin and γ-tubulin, and the ultrastructure of three pronuclear (3PN) oocytes were investigated. 3PN oocytes after ICSI procedure were taken from patients who were enrolled in assisted reproduction programmes. For mitochondrial membrane potential analysis, fresh oocytes stained with the mitochondrial membrane potential probe JC-1, were evaluated under fluorescence microscopy. The mitochondrial membrane potential of three pronuclear oocytes showed similar results to normal zygotes. γ-Tubulin was stained strongly at the subplasmalemmal domain and microfilaments were localized at the cortical, but not the perinuclear, area. Cytoplasmic halos were moderately or not detected by electron microscopy; lipofuscin granules, degenerated mitochondria, and multilamellated bodies were seen in the ooplasm. Immunohistochemistry and electron microscopic findings suggested that mitochondrial membrane potential has no direct effect on second polar body extrusion. This abnormality can be associated with an altered cytoskeleton due to poor oocyte quality.

RAB35 depletion affects spindle formation and actin-based spindle migration in mouse oocyte meiosis

2019 ◽  
Vol 25 (7) ◽  
pp. 359-372 ◽  
Author(s):  
Yu Zhang ◽  
Xiang Wan ◽  
Hong-Hui Wang ◽  
Meng-Hao Pan ◽  
Zhen-Nan Pan ◽  
...  
Keyword(s):  
Asymmetric Cell Division ◽  
Polar Body ◽  
Asymmetric Division ◽  
Mouse Oocyte ◽  
Meiotic Spindle ◽  
Spindle Formation ◽  
Oocyte Meiosis ◽  
Spindle Stability ◽  
Polar Body Extrusion ◽  
Cytoskeleton Dynamics

Abstract Mammalian oocyte maturation involves a unique asymmetric cell division, in which meiotic spindle formation and actin filament-mediated spindle migration to the oocyte cortex are key processes. Here, we report that the vesicle trafficking regulator, RAB35 GTPase, is involved in regulating cytoskeleton dynamics in mouse oocytes. RAB35 GTPase mainly accumulated at the meiotic spindle periphery and cortex during oocyte meiosis. Depletion of RAB35 by morpholino microinjection led to aberrant polar body extrusion and asymmetric division defects in almost half the treated oocytes. We also found that RAB35 affected SIRT2 and αTAT for tubulin acetylation, which further modulated microtubule stability and meiotic spindle formation. Additionally, we found that RAB35 associated with RHOA in oocytes and modulated the ROCK–cofilin pathway for actin assembly, which further facilitated spindle migration for oocyte asymmetric division. Importantly, microinjection of Myc-Rab35 cRNA into RAB35-depleted oocytes could significantly rescue these defects. In summary, our results suggest that RAB35 GTPase has multiple roles in spindle stability and actin-mediated spindle migration in mouse oocyte meiosis.

scholarly journals Ral GTPase is essential for actin dynamics and Golgi apparatus distribution in mouse oocyte maturation

Cell Division ◽  
2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Ming-Hong Sun ◽  
Lin-Lin Hu ◽  
Chao-Ying Zhao ◽  
Xiang Lu ◽  
Yan-Ping Ren ◽  
...  
Keyword(s):  
Golgi Apparatus ◽  
Oocyte Maturation ◽  
Polar Body ◽  
Mouse Oocyte ◽  
Actin Dynamics ◽  
Mouse Oocytes ◽  
Oocyte Meiosis ◽  
Ral Gtpase ◽  
Polar Body Extrusion ◽  
Cytoskeleton Dynamics

Abstract Background Ral family is a member of Ras-like GTPase superfamily, which includes RalA and RalB. RalA/B play important roles in many cell biological functions, including cytoskeleton dynamics, cell division, membrane transport, gene expression and signal transduction. However, whether RalA/B involve into the mammalian oocyte meiosis is still unclear. This study aimed to explore the roles of RalA/B during mouse oocyte maturation. Results Our results showed that RalA/B expressed at all stages of oocyte maturation, and they were enriched at the spindle periphery area after meiosis resumption. The injection of RalA/B siRNAs into the oocytes significantly disturbed the polar body extrusion, indicating the essential roles of RalA/B for oocyte maturation. We observed that in the RalA/B knockdown oocytes the actin filament fluorescence intensity was significantly increased at the both cortex and cytoplasm, and the chromosomes were failed to locate near the cortex, indicating that RalA/B regulate actin dynamics for spindle migration in mouse oocytes. Moreover, we also found that the Golgi apparatus distribution at the spindle periphery was disturbed after RalA/B depletion. Conclusions In summary, our results indicated that RalA/B affect actin dynamics for chromosome positioning and Golgi apparatus distribution in mouse oocytes.

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