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Updated: Jul 17, 2026
Multi-Photon Laser Ablation of Cytoplasmic Microtubule Organizing Centers in Mouse Oocytes
Published on: November 11, 2022
Inactivation of MAPK affects centrosome assembly, but not actin filament assembly, in mouse oocytes maturing in vitro
Seung-Eun Lee1, Ji-Hoi Kim, Nam-Hyung Kim
1National Research Laboratory of Molecular Embryology, Department of Animal Sciences, Chungbuk National University, Cheongju, Korea.
Abstract:
Mitogen-activated protein kinase (MAPK) plays a crucial role in meiotic maturation of mouse oocytes. In order to understand the mechanism by which MAPK regulates meiotic maturation, we examined the effects of the MAPK pathway inhibitor U0126 on microtubule organization, gamma-tubulin and nuclear mitotic apparatus protein (NuMA) distribution, and actin filament assembly in mouse oocytes maturing in vitro. Western blotting with antibodies that detect active, phosphorylated MAPK revealed that MAPK was inactive in fully grown germinal vesicle (GV) oocytes. Phosphorylated MAPK was first detected 3 hr after the initiation of maturation cultures, was fully active at 6 hr, and remained active until metaphase II. Treatment of GV stage oocytes with 20 microM U0126 completely blocked MAPK phosphorylation, but did not affect GV breakdown (GVBD). However, the oocytes did not progress to the Metaphase I stage, which would normally occur after 9 hr in the maturation cultures. The inhibition of MAPK resulted in abnormal spindles and abnormal distributions of gamma-tubulin and NuMA, but did not affect actin filament assembly. In oocytes treated with U0126 after GVBD, polar body extrusion was normal, but the organization of the metaphase plate and chromosome segregation were abnormal. In conclusion, the meiotic abnormalities caused by U0126, a specific inhibitor of MAPK signaling, indicate that MAPK plays an important regulatory role in microtubule and centrosome assembly, but not actin filament assembly.
Insights
Mitogen-activated protein kinase (MAPK) is vital for mouse oocyte meiotic maturation. Inhibiting MAPK disrupts microtubule and centrosome assembly, leading to meiotic abnormalities.
Area of Science:
- Cell Biology
- Developmental Biology
- Reproductive Biology
Background:
- Mitogen-activated protein kinase (MAPK) signaling is essential for oocyte meiotic maturation.
- Understanding MAPK's regulatory mechanisms in oogenesis is crucial for reproductive biology.
Purpose of the Study:
- To investigate the role of MAPK in regulating microtubule organization, protein distribution (gamma-tubulin, NuMA), and actin assembly during mouse oocyte meiotic maturation.
- To elucidate the specific functions of the MAPK pathway in key meiotic events.
Main Methods:
- In vitro maturation of mouse oocytes.
- Inhibition of the MAPK pathway using U0126.
- Western blotting to detect phosphorylated MAPK.
- Microscopic analysis of microtubule, gamma-tubulin, NuMA, and actin organization.
Main Results:
- MAPK is inactive in germinal vesicle (GV) oocytes and becomes active during maturation, peaking at 6 hours and persisting until metaphase II.
- U0126 treatment blocked MAPK phosphorylation, preventing progression to Metaphase I and causing abnormal spindle and centrosome (gamma-tubulin, NuMA) organization.
- Actin filament assembly remained unaffected by MAPK inhibition, but metaphase plate organization and chromosome segregation were abnormal after GV breakdown.
Conclusions:
- MAPK signaling is critical for proper microtubule and centrosome assembly during mouse oocyte meiosis.
- MAPK does not appear to regulate actin filament assembly during this process.
- Disruption of MAPK signaling leads to significant meiotic abnormalities, highlighting its regulatory role in oocyte development.
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