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Demonstration of maturation-promoting and -inhibiting activities in mouse oocytes
1Department of Obstetrics and Gynecology, Keio University School of Medicine, Tokyo, Japan.
Abstract:
The microinjection of cytoplasm from mature mouse oocytes into immature mouse oocytes induced the resumption of meiosis in the presence of 100 micrograms/ml dibutyryl cyclic AMP or 100 microM 3-isobutyl-1-methylxanthine. The volume of cytoplasm injected was critical to bringing about this maturation-promoting activity in mouse oocytes, and 20 pl of cytoplasm seems to be required to overcome the inhibitory effect of cyclic AMP on oocyte maturation. Furthermore, it was demonstrated that the microinjection of cytoplasm from immature mouse oocytes into immature mouse oocytes augmented the inhibitory effect of cyclic AMP on the resumption of meiosis. These results suggest that the appearance and disappearance of maturation-promoting and -inhibiting activities appear to be dependent on the meiotic stages in the mouse oocytes.
Insights
Cytoplasm microinjection into mouse oocytes can resume meiosis, overcoming inhibitory cyclic AMP. The volume of injected cytoplasm and its source (mature vs. immature oocytes) are critical for regulating oocyte maturation.
Area of Science:
- Developmental Biology
- Cell Biology
- Reproductive Biology
Background:
- Oocyte maturation is a complex process regulated by intracellular factors.
- Cyclic AMP (cAMP) is known to inhibit meiosis resumption in oocytes.
- The role of cytoplasmic factors in regulating meiotic progression requires further elucidation.
Purpose of the Study:
- To investigate the role of cytoplasm microinjection in inducing meiotic resumption in mouse oocytes.
- To determine the effect of cytoplasm volume and source on meiotic maturation.
- To understand the interplay between cytoplasmic factors and cyclic AMP in oocyte meiotic regulation.
Main Methods:
- Microinjection of cytoplasm from mature and immature mouse oocytes into immature oocytes.
- Culture of oocytes in the presence of dibutyryl cyclic AMP or 3-isobutyl-1-methylxanthine.
- Assessment of meiotic resumption following microinjection and chemical treatment.
Main Results:
- Microinjection of mature oocyte cytoplasm induced meiotic resumption, overcoming cAMP inhibition.
- A critical volume of 20 pl of mature oocyte cytoplasm was required to overcome cAMP's inhibitory effect.
- Microinjection of immature oocyte cytoplasm augmented cAMP's inhibitory effect on meiosis.
Conclusions:
- Maturation-promoting activity resides in the cytoplasm of mature oocytes.
- Maturation-inhibiting activity is present in the cytoplasm of immature oocytes.
- The stage-dependent appearance and disappearance of these cytoplasmic activities regulate mouse oocyte maturation.