Pleiotropic effect of okadaic acid on maturing mouse oocytes

Development ◽  
1991 ◽  
Vol 112 (4) ◽  
pp. 971-980 ◽  
Author(s):  
H. Alexandre ◽  
A. Van Cauwenberge ◽  
Y. Tsukitani ◽  
J. Mulnard
Keyword(s):  
Protein Kinase ◽  
Okadaic Acid ◽  
Protein Phosphatases ◽  
Chromatin Condensation ◽  
Polar Body ◽  
Germinal Vesicle ◽  
Inhibitory Effect ◽  
Negative Control ◽  
Germinal Vesicle Breakdown ◽  
Mouse Oocytes

Okadaic acid (OA), a potent inhibitor of types 1 and 2A protein phosphatases, was shown recently to induce chromatin condensation and germinal vesicle breakdown (GVBD) in mouse oocytes arrested at the dictyate stage by dibutyryl cAMP (dbcAMP), isobutyl methylxanthine (IBMX) and 12,13-phorbol dibutyrate (PDBu). We confirm these results using IBMX and another phorbol diester, 12-O-tetradecanoylphorbol-13-acetate (TPA) and show that OA also bypasses the inhibitory effect of 6-dimethylaminopurine (6-DMAP). It has been concluded that protein phosphatases 1 and/or 2A (PP1, 2A), involved in the negative control of MPF activation, are thus operating downstream from both the protein kinase A and protein kinase C catalysed phosphorylation steps that prevent the breakdown of GV. Similar enzymatic activities are also able to counteract the general inhibition of protein phosphorylation. However, PP1 and/or PP2A are positively involved in the activation of pericentriolar material (PCM) into microtubule organizing centres (MTOCs). This explains the inhibitory effect of OA on spindle assembly. Finally, OA interferes with the integrity and/or function of actomyosin filaments. This results in a dramatic ruffling of the plasma membrane leading to the internalization of large vacuoles, the inhibition of chromosome centrifugal displacement and, consequently, the prevention of polar body extrusion.

Effects of protein kinase C activators on germinal vesicle breakdown and polar body emission of mouse oocytes

1986 ◽  
Vol 165 (2) ◽  
pp. 507-517 ◽  
Author(s):  
Elayne A. Bornslaeger ◽  
William T. Poueymirou ◽  
Peter Mattei ◽  
Richard M. Schultz
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Polar Body ◽  
Germinal Vesicle ◽  
Germinal Vesicle Breakdown ◽  
Mouse Oocytes ◽  
Kinase C ◽  
Protein Kinase C Activators

scholarly journals Involvement of protein phosphatases 1 and 2A in the control of M phase-promoting factor activity in starfish.

1989 ◽  
Vol 109 (6) ◽  
pp. 3347-3354 ◽  
Author(s):  
A Picard ◽  
J P Capony ◽  
D L Brautigan ◽  
M Dorée
Keyword(s):  
Okadaic Acid ◽  
Protein Phosphatases ◽  
Germinal Vesicle ◽  
Histone H1 ◽  
Specific Inhibition ◽  
Factor Activity ◽  
Microtubule Network ◽  
Germinal Vesicle Breakdown ◽  
M Phase

Specific inhibition of types 1 and 2A protein phosphatases by microinjection of okadaic acid (OA) into starfish oocytes induced germinal vesicle breakdown and activation of M phase-promoting factor (MPF) and histone H1 kinase. The effects were evident in immature oocytes arrested at first meiotic prophase as well as in fully mature oocytes arrested at the pronucleus stage. In addition, MPF and histone H1 kinase were stabilized for several hours and protected from inactivation by inhibition of type 1 protein phosphatases with either OA or specific anti-phosphatase antibodies. Microinjection of okadaic acid was associated with unusual changes of the microtubule network, including the disappearance of spindles and extension of the cytoplasmic array of microtubules. MPF activation after OA injection was associated with dephosphorylation of phosphothreonine and phosphoserine residues in cdc2, showing that neither type 1 nor 2A protein phosphatases catalyzes these dephosphorylations. The effects of OA on MPF activation and inactivation appeared to involve the cyclin subunit. OA did not induce MPF activation in the absence of protein synthesis and it prevented degradation of cyclin. Therefore protein phosphatases types 1 and 2A appear to be involved in activation and inactivation of MPF involving mechanisms that operate after cyclin synthesis and before its degradation.

scholarly journals Translocation of phospho-protein kinase Cs implies their roles in meiotic-spindle organization, polar-body emission and nuclear activity in mouse eggs

Reproduction ◽  
2005 ◽  
Vol 129 (2) ◽  
pp. 229-234 ◽  
Author(s):  
Zhen-Yu Zheng ◽  
Qing-Zhang Li ◽  
Da-Yuan Chen ◽  
Heide Schatten ◽  
Qing-Yuan Sun
Keyword(s):  
Protein Kinase ◽  
Polar Body ◽  
Germinal Vesicle ◽  
Mouse Oocyte ◽  
Meiotic Spindle ◽  
Germinal Vesicle Breakdown ◽  
Nuclear Activity ◽  
Spindle Poles ◽  
Oocyte Meiosis ◽  
First Polar Body

The protein kinase Cs (PKCs) are a family of Ser/Thr protein kinases categorized into three subfamilies: classical, novel, and atypical. The phosphorylation of PKC in germ cells is not well defined. In this study, we described the subcellular localization of phopho-PKC in the process of mouse oocyte maturation, fertilization, and early embryonic mitosis. Confocal microscopy revealed that phospho-PKC (pan) was distributed abundantly in the nucleus at the germinal vesicle stage. After germinal vesicle breakdown, phospho-PKC was localized in the vicinity of the condensed chromosomes, distributed in the whole meiotic spindle, and concentrated at the spindle poles. After metaphase I, phospho-PKC was translocated gradually to the spindle mid-zone during emission of the first polar body. After sperm penetration and electrical activation, the distribution of phospho-PKC was moved from the spindle poles to the spindle mid-zone. After the extrusion of the second polar body (PB2) phospho-PKC was localized in the area between the oocyte and the PB2. In fertilized eggs, phospho-PKC was concentrated in the pronuclei except for the nucleolus. Phospho-PKC was dispersed after pronuclear envelope breakdown, but distributed on the entire spindle at mitotic metaphase. The results suggest that PKC activation may play important roles in regulating spindle organization and stabilization, polar-body extrusion, and nuclear activity during mouse oocyte meiosis, fertilization, and early embryonic mitosis.

scholarly journals Mitochondrial Ca2+ Overload Leads to Mitochondrial Oxidative Stress and Delayed Meiotic Resumption in Mouse Oocytes

2020 ◽  
Vol 8 ◽  
Author(s):  
Luyao Zhang ◽  
Zichuan Wang ◽  
Tengfei Lu ◽  
Lin Meng ◽  
Yan Luo ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mitochondrial Function ◽  
Maternal Obesity ◽  
Polar Body ◽  
Germinal Vesicle ◽  
Oocyte Quality ◽  
Obese Women ◽  
Germinal Vesicle Breakdown ◽  
Mouse Oocytes ◽  
First Polar Body

Overweight or obese women seeking pregnancy is becoming increasingly common. Human maternal obesity gives rise to detrimental effects during reproduction. Emerging evidence has shown that these abnormities are likely attributed to oocyte quality. Oxidative stress induces poor oocyte conditions, but whether mitochondrial calcium homeostasis plays a key role in oocyte status remains unresolved. Here, we established a mitochondrial Ca2+ overload model in mouse oocytes. Knockdown gatekeepers of the mitochondrial Ca2+ uniporters Micu1 and Micu2 as well as the mitochondrial sodium calcium exchanger NCLX in oocytes both increased oocytes mitochondrial Ca2+ concentration. The overload of mitochondria Ca2+ in oocytes impaired mitochondrial function, leaded to oxidative stress, and changed protein kinase A (PKA) signaling associated gene expression as well as delayed meiotic resumption. Using this model, we aimed to determine the mechanism of delayed meiosis caused by mitochondrial Ca2+ overload, and whether oocyte-specific inhibition of mitochondrial Ca2+ influx could improve the reproductive abnormalities seen within obesity. Germinal vesicle breakdown stage (GVBD) and extrusion of first polar body (PB1) are two indicators of meiosis maturation. As expected, the percentage of oocytes that successfully progress to the germinal vesicle breakdown stage and extrude the first polar body during in vitro culture was increased significantly, and the expression of PKA signaling genes and mitochondrial function recovered after appropriate mitochondrial Ca2+ regulation. Additionally, some indicators of mitochondrial performance—such as adenosine triphosphate (ATP) and reactive oxygen species (ROS) levels and mitochondrial membrane potential—recovered to normal. These results suggest that the regulation of mitochondrial Ca2+ uptake in mouse oocytes has a significant role during oocyte maturation as well as PKA signaling and that proper mitochondrial Ca2+ reductions in obese oocytes can recover mitochondrial performance and improve obesity-associated oocyte quality.

Meiotic maturation of mouse oocytes in vitro: inhibition of maturation at specific stages of nuclear progression

1976 ◽  
Vol 22 (3) ◽  
pp. 531-545
Author(s):  
P.M. Wassarman ◽  
W.J. Josefowicz ◽  
G.E. Letourneau
Keyword(s):  
Cyclic Amp ◽  
Cytochalasin B ◽  
Polar Body ◽  
Germinal Vesicle ◽  
Meiotic Maturation ◽  
Dibutyryl Cyclic Amp ◽  
Germinal Vesicle Breakdown ◽  
Mouse Oocytes ◽  
First Polar Body

In vitro studies of meiotic maturation of mouse oocytes have been carried out in the presence of several drugs. The individual steps of nuclear progression, including dissolution of the nuclear (germinal vesicle) membrane, condensation of dictyate chromatin into compact bivalents, formation of the first metaphase spindle, and extrusion of the first polar body, are each susceptible to one or more of these drugs. Germinal vesicle breakdown, the initial morphological feature characteristic of meiotic maturation, is inhibited by dibutyryl cyclic AMP. However, even in the presence of dibutyryl cyclic AMP, the nuclear membrane becomes extremely convoluted and condensation of chromatin is initiated but aborts at a stage short of compact bivalents. Germinal vesicle breakdown and chromatin condensation take place in an apparently normal manner in the presence of puromycin, Colcemid, or cytochalasin B. Nuclear progression is blocked at the circular bivalent stage when oocytes are cultured continuously in the presence of puromycin or Colcemid, whereas oocytes cultured in the presence of cytochalasin B proceed to the first meiotic metaphase, form an apparently normal spindle, and arrest. Emission of a polar body is inhibited by all of these drugs. The inhibitory effects of these drugs on meiotic maturation are reversible to varying degrees dependent upon the duration of exposure to the drug and upon the nature of the drug. These studies suggest that dissolution of the mouse oocyte's germinal vesicle and condensation of chromatin are not dependent upon concomitant protein synthesis or upon microtubules. On the other hand, the complete condensation of chromatin into compact bivalents apparently requires breakdown of the germinal vesicle. Failure of homologous chromosomes to separate after normal alignment on the meiotic spindle in the presence of cytochalasin B suggest that microfilaments may be involved in nuclear progression at this stage of maturation. Cytokinesis, in the form of polar body formation, is blocked when any one of the earlier events of maturation fails to take place.

Capacity of mouse oocytes to become activated depends on completion of cytoplasmic but not nuclear meiotic maturation

Zygote ◽  
1995 ◽  
Vol 3 (1) ◽  
pp. 45-55 ◽  
Author(s):  
Joise M.L. McConnell ◽  
Liz Campbell ◽  
Caroline Vincent
Keyword(s):  
Chromosomal Rearrangements ◽  
Polar Body ◽  
Calcium Ionophore ◽  
Germinal Vesicle ◽  
Calcium Ionophore A23187 ◽  
Meiotic Maturation ◽  
Ionophore A23187 ◽  
Germinal Vesicle Breakdown ◽  
Mouse Oocytes ◽  
Polar Body Extrusion

SummaryThe ability of mouse oocytes to become activated after exposure too the calcium ionophore A23187 has been investigated at different stages of meiotic maturation. The potential to respond to ionophore has been studied in relation to the time since resumption of meiotic maturation, the chromosomal conformation of the DNA within each cell and the protein synthetic profile of the maturing oocyte. Our studies demonstrate that when maturing oocytes from an MF1 strain of mice were treated with A23187 activation occured only in oocytes which had reached second meiotic metaphase (MII). However, development of the ability to respond to ionophore was not dependent on an orderly progression through normal chromosomal rearrangements such as separation at metaphase I (MI) and subsequent polar body extrusion, since there process could be prevented and the capacity to be activated became apparent in such oocytes at a time when control cells had reached MII. These data suggest that the ability to respond to ionophore depends on the development of a cytoplasmic or complex capable of monitoring the time since initiation of germinal vesicle breakdown. Metabolic radiolabelling of oocytes which were able to respond to calcium ionophore, even though they had been prevented from undergoing normal chromosomal rearrangements, showed them to be synthesising a group of proteins known as the 35 kDa complex.

scholarly journals Perturbing microtubule integrity blocks AMP-activated protein kinase-induced meiotic resumption in cultured mouse oocytes

Zygote ◽  
2012 ◽  
Vol 22 (1) ◽  
pp. 91-102 ◽  
Author(s):  
Ru Ya ◽  
Stephen M. Downs
Keyword(s):  
Protein Kinase ◽  
Polar Body ◽  
Cumulus Cell ◽  
Metaphase Plate ◽  
Germinal Vesicle ◽  
Meiotic Spindle ◽  
Marginal Effect ◽  
Dependent Manner ◽  
Germinal Vesicle Breakdown ◽  
Amp Activated Protein Kinase

SummaryThe oocyte meiotic spindle is comprised of microtubules (MT) that bind chromatin and regulate both metaphase plate formation and karyokinesis during meiotic maturation; however, little information is known about their role in meiosis reinitiation. This study was conducted to determine if microtubule integrity is required for meiotic induction and to ascertain how it affects activation of AMP-activated protein kinase (AMPK), an important participant in the meiotic induction process. Treatment with microtubule-disrupting agents nocodazole and vinblastine suppressed meiotic resumption in a dose-dependent manner in both arrested cumulus cell-enclosed oocytes (CEO) stimulated with follicle-stimulating hormone (FSH) and arrested denuded oocytes (DO) stimulated with the AMPK activator, 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR). This effect coincided with suppression of AMPK activation as determined by western blotting and germinal vesicle immunostaining. Treatment with the MT stabilizer paclitaxel also suppressed meiotic induction. Targeting actin filament polymerization had only a marginal effect on meiotic induction. Immunolocalization experiments revealed that active AMPK colocalized with γ-tubulin during metaphase I and II stages, while it localized at the spindle midzone during anaphase. This discrete localization pattern was dependent on MT integrity. Treatment with nocodazole led to disruption of proper spindle pole localization of active AMPK, while paclitaxel induced excessive polymerization of spindle MT and formation of ectopic asters with accentuated AMPK colocalization. Although stimulation of AMPK increased the rate of germinal vesicle breakdown (GVB), spindle formation and polar body (PB) extrusion, the kinase had no effect on peripheral movement of the spindle. These data suggest that the meiosis-inducing action and localization of AMPK are regulated by MT spindle integrity during mouse oocyte maturation.

331. INVESTIGATING THE ROLE OF CYCLIN A2 DURING OOCYTE MEIOSIS

2010 ◽  
Vol 22 (9) ◽  
pp. 131
Author(s):  
P. C. Jennings ◽  
K. T. Jones
Keyword(s):  
Polar Body ◽  
Germinal Vesicle ◽  
Cyclin B1 ◽  
Negative Control ◽  
Early Embryo ◽  
Female Meiosis ◽  
Germinal Vesicle Breakdown ◽  
Molecular Control ◽  
First Polar Body ◽  
Cyclin A2

Aneuploidy is often derived from chromosomal segregation errors in oocytes, leading to Down Syndrome and early embryo loss. Thus it is important to understand the molecular control of female meiosis. Cyclins and cyclin-dependent kinases (CDKs), particular those contributing to Maturation Promoting Factor (MPF, or CDK1) activity, play key roles in regulating meiosis. While cyclin B1 is classically regarded as the regulatory component of MPF, cyclin A2 can also bind and activate CDK1, and in mammalian somatic cells it is known to promote both G1/S and G2/M transitions. There is an absolute requirement for cyclin A2 during development and differentiation as its deficiency results in early embryonic lethality. As such, cyclin A2 has not been extensively studied, particularly as to its role in meiosis. To examine the role cyclin A2 plays during mammalian female meiosis, we carried out knockdown experiments. Microinjection into mouse oocytes of cyclin A2 siRNA induced a ~70% knockdown. Cyclin A2 knockdown did not inhibit germinal vesicle breakdown but did act to delay it. Extrusion of the first polar body was significantly reduced (P = 0.002) in comparison to non-injected controls and those injected with a negative control siRNA. Furthermore, microinjection of cyclin A2 can stimulate entry into meiosis. Thus it seems possible that cyclin A2/CDK can exhibit MPF activity. In conclusion, our data suggest that cyclin A2 can regulate meiotic entry in oocytes and also plays an important role in successful passage through the first meiotic division.

scholarly journals Activation of mitogen-activated protein kinase during meiotic maturation in porcine oocytes

Zygote ◽  
1995 ◽  
Vol 3 (3) ◽  
pp. 265-271 ◽  
Author(s):  
Maki Inoue ◽  
Kunihiko Naito ◽  
Fugaku Aoki ◽  
Yutaka Toyoda ◽  
Eimei Sato
Keyword(s):  
Protein Kinase ◽  
Map Kinase ◽  
Kinase Activity ◽  
Polar Body ◽  
Germinal Vesicle ◽  
Mitogen Activated Protein Kinase ◽  
Meiotic Maturation ◽  
Germinal Vesicle Breakdown ◽  
First Polar Body ◽  
Mitogen Activated Protein

SummaryTo investigate the involvement of mitogen-activated protein kinase(MAP kinase) in meiotic maturation of porcine oocytes, we assayed MAP kinase activity using basic protein(MBP) as a substrate. MAP kinase activity was low during the germinal vesicle stage, 0–20 h of culture. An abrupt increase was observed at metaphase I(30 h of culture), and activity remained significantly higher than that at 0 h until 50 h of culture, with a transient slight decrease at the time of first polar body extrusion (40 h). Detection of the kinase activity by an in-gel phosphorylation assay confirmed that the 42 and 44 kDa MAP kinases were significantly activated in 45 h cultured oocytes but not in 0 h oocytes, and just slightly in 20 h oocytes. In immunoblotting, however, the 42 and 44 kDa bands were detected in 0, 20 and 45 h cultured oocytes. Furthermore, the signal strength of the two bands did not change during the period of culture, but shifted up to 45 h, indicating that the activation of MAP kinase depended not on the synthesis but on the phosphorylation of this enzyme. These results suggest that the activation of MAP kinase is involved in the regulation of meiotic maturation of porcine oocytes, and especially in the regulation after germinal vesicle breakdown.

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