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Does autocatalytic amplification of maturation-promoting factor (MPF) exist in mammalian oocytes?
J Fulka1, J E Fléchon, J Motlík
1Institute of Animal Production, Uhrinĕves, Czechoslovakia.
Abstract:
The method of polyethylene-glycol-induced fusion of mammalian oocytes was applied to study maturation-promoting factor (MPF) activity. After homologous fusions of one maturing--late diakinesis (LD), metaphase I (MI)--pig or mouse oocyte to one, two, or three immature-germinal vesicle (GV)--oocytes, giant cells were cultured in control or cycloheximide supplemented medium for 3 hours. The occurrence of germinal vesicle breakdown (GVBD) and premature chromosome condensation (PCC) served as a control of MPF activity. In giant cells composed of one maturing and one, two or three immature oocytes, GVBD and PCC were observed in all cases after cultivation in the control medium. In the presence of cycloheximide, the completion of GVBD and PCC remained high when one maturing and one immature oocyte were fused (83.7% and 95.7% of GVBD in pig and mouse, respectively). However, in giant cells composed of one maturing and up to three immature oocytes, all GVs were broken down only occasionally (4.8% and 11.7% in pig and mouse, respectively). These results suggest that in pig and mouse oocytes MPF does not amplify autocatalytically, but requires active protein synthesis for its production.
Insights
Maturation-promoting factor (MPF) activity in pig and mouse oocytes does not amplify itself. Active protein synthesis is required for MPF production, as demonstrated by oocyte fusion experiments.
Area of Science:
- Reproductive Biology
- Cellular Biology
- Developmental Biology
Background:
- Maturation-promoting factor (MPF) is crucial for oocyte maturation.
- Understanding MPF regulation is key to comprehending early developmental processes.
Purpose of the Study:
- To investigate the amplification and production mechanisms of MPF in mammalian oocytes.
- To determine if MPF activity is dependent on protein synthesis.
Main Methods:
- Polyethylene-glycol-induced fusion of mammalian oocytes (pig and mouse).
- Fusion of maturing oocytes with immature oocytes in varying ratios.
- Culture of fused 'giant' cells in control and cycloheximide-supplemented media.
- Assessment of germinal vesicle breakdown (GVBD) and premature chromosome condensation (PCC) as indicators of MPF activity.
Main Results:
- GVBD and PCC occurred in all fused oocytes in control medium.
- In cycloheximide, GVBD and PCC completion remained high when one maturing oocyte fused with one immature oocyte.
- Fusion of one maturing oocyte with multiple immature oocytes in cycloheximide resulted in significantly reduced GVBD and PCC.
- These findings indicate MPF does not amplify autocatalytically.
Conclusions:
- MPF production in pig and mouse oocytes requires active protein synthesis.
- MPF activity is not amplified autocatalytically but depends on ongoing protein synthesis for its maintenance and progression.