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Activity of maturation promoting factor in pig oocytes after microinjection and serial transfer of maturing cytoplasm
R Procházka1, J Motlík, J Fulka
1Czechoslovak Academy of Sciences, Institute of Animal Physiology and Genetics, Department of Genetics, Libĕchov.
Abstract:
Microinjection of 120 pl homologous or heterologous (mouse) maturing cytoplasm into immature pig oocytes resulted in germinal vesicle breakdown (GVBD) and chromosome condensation (CC) after 8 h of culture. In contrast, nearly all control oocytes remained at the germinal vesicle stage. Immature cytoplasm did not induce nuclear maturation of recipient oocytes when injected. The cytoplasm of the oocytes injected with maturing cytoplasm preserved the capacity to cause GVBD in the second recipients. These results suggest that the level of injected maturation promoting factor (MPF) must rise before GVBD can occur. When the pig oocytes injected with 120 pl of mouse maturing cytoplasm were cultured in cycloheximide for 8 h, the presence of GVBD was dramatically reduced. Thus, in pig oocytes the increase in active MPF up to the effective concentration requires protein synthesis.
Insights
Maturing cytoplasm, but not immature cytoplasm, triggers pig oocyte maturation, indicated by germinal vesicle breakdown (GVBD). This process requires protein synthesis to increase maturation promoting factor (MPF) levels.
Area of Science:
- Reproductive Biology
- Cell Biology
- Developmental Biology
Background:
- Oocyte maturation is a critical process for successful reproduction.
- Understanding the molecular mechanisms that regulate oocyte maturation is essential for improving assisted reproductive technologies.
Purpose of the Study:
- To investigate the role of cytoplasm in inducing nuclear maturation of immature pig oocytes.
- To determine the requirement of protein synthesis for the maturation promoting factor (MPF) activity.
Main Methods:
- Microinjection of maturing or immature cytoplasm (homologous or heterologous) into immature pig oocytes.
- Culture of injected oocytes and assessment of nuclear maturation (germinal vesicle breakdown and chromosome condensation).
- Culture in cycloheximide to inhibit protein synthesis and assess its effect on maturation.
Main Results:
- Microinjection of maturing cytoplasm induced germinal vesicle breakdown (GVBD) and chromosome condensation (CC) in immature pig oocytes.
- Immature cytoplasm failed to induce nuclear maturation.
- The capacity to induce GVBD was maintained in the cytoplasm of oocytes that underwent maturation.
- Inhibition of protein synthesis significantly reduced GVBD, indicating its necessity for maturation.
Conclusions:
- Maturing cytoplasm contains factors that promote oocyte nuclear maturation.
- The increase in maturation promoting factor (MPF) activity required for GVBD is dependent on protein synthesis in pig oocytes.