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Microtubule rearrangement during in vitro maturation of pig oocytes. Effect of cycloheximide
J Rozinek1, J Petr, R Grocholová
1Department of Reproductive Biology and Molecular Genetics, Research Institute of Animal Production, Prague, Uhrínĕves, Czech Republic.
Abstract:
In freshly isolated fully grown pig oocytes at the germinal vesicle (GV) stage, the cytoplasmic microtubules are arranged in a meshwork. This microtubule arrangement is also maintained during the initial phases of meiotic maturation in vitro. A perinuclear array of microtubules is formed immediately before germinal vesicle breakdown (GVBD). Short-term treatment of oocytes with taxol when oocytes are at metaphase I stage induced formation of cytoplasmic asters. The oocyte cytoplasm is unable to respond to the taxol treatment at the earlier stages of meiotic maturation. In oocytes cultured with the proteosynthesis inhibitor cycloheximide, meiotic maturation is blocked. Condensation of chromatin occurs but the nuclear envelope is preserved and the microtubule arrangement is unchanged. A perinuclear array of microtubules does not appear and oocyte cytoplasm does not respond to short-term taxol treatment by the formation of cytoplasmic asters. We can conclude that the microtubule rearrangement and the acquisition of competence for tubulin assembly are blocked by cycloheximide and are thus dependent on de novo proteosynthesis.
Insights
Pig oocyte maturation involves microtubule rearrangement, forming a perinuclear array before germinal vesicle breakdown (GVBD). This process requires new protein synthesis, as cycloheximide blocks microtubule changes and taxol response.
Area of Science:
- Cell Biology
- Developmental Biology
- Reproductive Biology
Background:
- Cytoplasmic microtubules in pig oocytes exhibit a meshwork arrangement at the germinal vesicle (GV) stage.
- This arrangement is maintained during early meiotic maturation, with a perinuclear array forming before germinal vesicle breakdown (GVBD).
Purpose of the Study:
- To investigate the role of de novo proteosynthesis in microtubule rearrangement during pig oocyte meiotic maturation.
- To determine the stage-specific response of oocyte microtubules to taxol treatment.
Main Methods:
- Oocytes were cultured in vitro with and without the proteosynthesis inhibitor cycloheximide.
- Taxol treatment was applied at different meiotic maturation stages to assess microtubule assembly competence.
Main Results:
- Cycloheximide treatment blocked meiotic maturation, nuclear envelope breakdown, and microtubule rearrangement, preventing perinuclear array formation.
- Oocyte cytoplasm did not respond to taxol at early maturation stages but formed cytoplasmic asters at metaphase I.
- Cycloheximide-treated oocytes failed to form cytoplasmic asters upon taxol exposure.
Conclusions:
- Microtubule rearrangement and the ability to assemble tubulin are dependent on de novo proteosynthesis during pig oocyte maturation.
- The acquisition of competence for microtubule reorganization and response to external stimuli like taxol is regulated by protein synthesis.