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Updated: Apr 20, 2026
Evaluation of the Spindle Assembly Checkpoint Integrity in Mouse Oocytes
Published on: September 13, 2022
Role of Greatwall kinase in release of mouse oocytes from diplotene arrest
Xiangyu Zhao1, Dahai Yu, Chen Feng
1Department of Biochemical and Molecular Biology, China Medical University, Shenyang, Liaoning Province, China.
Abstract:
In eukaryotes, mitosis entry is induced by activation of maturation-promoting factor (MPF), which is regulated by a network of kinases and phosphatases. It has been suggested that Greatwall (GWL) kinase was crucial for the M-phase entry and could maintain cyclin B-Cdc2 activity through regulation of protein phosphatase 2A (PP2A), a counteracting phosphatase of MPF. Here, the role of GWL was assessed during release of mouse oocytes from prophase I arrest. GWL was crucial for meiotic maturation in mouse oocytes. As a positive regulator for meiosis resumption, GWL was continually expressed in germinal vesicle (GV) and MII stage oocytes and two-cell stage embryos. Additionally, GWL localized to the nucleus and dispersed into cytoplasm during GV breakdown (GVBD). Furthermore, downregulation of GWL or overexpression of catalytically-inactive GWL inhibited partial meiotic maturation. This prophase I arrest induced by GWL depletion could be rescued by the PP2A inhibition. However, both GWL-depleted and rescued oocytes had severe spindle defects that hardly reached MII. In contrast, oocytes overexpressing wild-type GWL resumed meiosis and progressed to MII stage. Thus, our data demonstrate that GWL acts in a pathway with PP2A which is essential for prophase I exit and metaphase I microtubule assembly in mouse oocytes.
Insights
Greatwall (GWL) kinase is vital for mouse oocyte maturation, regulating entry into meiosis by controlling protein phosphatase 2A (PP2A) activity. Its proper function ensures correct spindle assembly for successful progression to MII stage.
Area of Science:
- Cell Biology
- Developmental Biology
- Reproductive Biology
Background:
- Mitosis entry in eukaryotes is regulated by maturation-promoting factor (MPF).
- Greatwall (GWL) kinase is proposed to regulate MPF activity via protein phosphatase 2A (PP2A).
Purpose of the Study:
- To investigate the role of GWL in the release of mouse oocytes from prophase I arrest.
- To elucidate the mechanism by which GWL influences meiotic maturation and spindle assembly.
Main Methods:
- Assessment of GWL expression and localization in mouse oocytes at various meiotic stages.
- Manipulation of GWL levels (downregulation, overexpression of wild-type and inactive forms) in oocytes.
- Inhibition of PP2A activity in GWL-depleted oocytes.
- Analysis of meiotic progression and spindle morphology.
Main Results:
- GWL is crucial for meiotic maturation, continuously expressed from germinal vesicle to MII stage.
- GWL depletion or overexpression of inactive GWL partially inhibited maturation and caused spindle defects.
- PP2A inhibition rescued prophase I arrest in GWL-depleted oocytes but did not fully restore spindle function.
- Overexpression of wild-type GWL promoted normal meiosis resumption and MII progression.
Conclusions:
- GWL is essential for meiotic resumption and exit from prophase I arrest in mouse oocytes.
- GWL functions in a pathway with PP2A, critical for metaphase I spindle assembly.
- GWL plays a key role in ensuring proper microtubule organization during oocyte maturation.
