Cell cycle dynamics of maturation-promoting factor during mouse oocyte maturation

Area of Science:

• Cell Biology
• Developmental Biology
• Reproductive Biology

Background:

• Cytoplasmic maturation-promoting factor (MPF) regulates meiosis resumption.
• Understanding MPF dynamics is crucial for comprehending oocyte maturation.
• Mouse oocyte maturation involves complex cell cycle events.

Purpose of the Study:

• To investigate the changes in MPF activity during mouse oocyte maturation.
• To determine the correlation between MPF activity and meiotic progression.
• To elucidate the role of MPF in the transition from metaphase to subsequent meiotic events.

Main Methods:

• Injection of starfish oocyte MPF into mouse oocytes.
• Observation of MPF activity during the meiotic cycle.
• Treatment of oocytes with cytochalasin D and cycloheximide.
• Microscopic analysis of chromosomes and meiotic spindles.

Main Results:

• MPF activity appeared at germinal vesicle breakdown (GVBD), peaked at metaphase I and II, and decreased at polar body emission.
• A strong correlation was observed between MPF activity and meiotic metaphase.
• Cytochalasin D treatment maintained metaphase and elevated MPF activity.
• Cycloheximide addition reduced MPF activity, leading to chromosome decondensation and nuclear structure formation.
• Only monovalent chromosomes decondensed in response to MPF activity decrease.

Conclusions:

• MPF activity is tightly regulated throughout mouse oocyte meiosis.
• The disappearance of MPF activity is a critical trigger for metaphase-to-anaphase transition and subsequent meiotic events.
• Chromosome decondensation requires both MPF downregulation and dissociation of synapsis.