Related Experiment Videos
MAP kinase, a universal suppressor of sperm centrosomes during meiosis?
1Instituto de Biología Celular y Molecular, Universidad Autónoma de Baja California, Ensenada, Baja California, 22800, Mexico.
Abstract:
We reported previously that inhibition of MAP kinase during meiosis in Urechis caupo eggs caused premature sperm aster formation and we reviewed indirect evidence that the suppression of sperm asters by MAPK during meiosis might be a universal mechanism (M. C. Gould and J. L. Stephano, 1999, Dev. Biol. 216, 348-358). We tested this proposition with oyster (Crassostrea gigas) and starfish (Asterina miniata) eggs, utilizing the MEK inhibitors U0126 and PD98059. Centrosomes, asters, and meiotic spindles were visualized by normal epifluorescence and confocal microscopy following indirect immunocytochemical staining for anti-beta-tubulin. When MAPK activation was inhibited, sperm asters in both species developed prematurely and tended to move toward the egg centrosomes, sometimes even fusing with the egg spindle or centrosomes. Meiotic spindles and polar body formation were also abnormal when MAPK was inhibited.
Insights
Inhibition of MAP kinase (MAPK) in oyster and starfish eggs caused premature sperm aster formation, suggesting a universal role for MAPK in suppressing sperm asters during meiosis.
Area of Science:
- Cell Biology
- Developmental Biology
- Molecular Biology
Background:
- Previous studies indicated that inhibiting MAP kinase (MAPK) during meiosis in Urechis caupo eggs leads to premature sperm aster formation.
- Indirect evidence suggested this suppression of sperm asters by MAPK during meiosis might be a universal biological mechanism.
Purpose of the Study:
- To test the universality of MAPK's role in suppressing sperm aster formation during meiosis.
- To investigate the effects of MAPK inhibition on sperm aster development and meiotic spindle organization in oyster and starfish eggs.
Main Methods:
- Utilized MEK inhibitors U0126 and PD98059 to block MAPK activation in oyster (Crassostrea gigas) and starfish (Asterina miniata) eggs.
- Visualized centrosomes, asters, and meiotic spindles using epifluorescence and confocal microscopy.
- Employed indirect immunocytochemical staining with anti-beta-tubulin for detailed structural analysis.
Main Results:
- Inhibition of MAPK activation resulted in premature sperm aster development in both oyster and starfish eggs.
- Prematurely formed sperm asters exhibited aberrant movement, often migrating towards egg centrosomes and occasionally fusing with the meiotic spindle or centrosomes.
- Abnormalities were also observed in meiotic spindle formation and polar body extrusion upon MAPK inhibition.
Conclusions:
- MAPK plays a crucial role in regulating sperm aster formation during meiosis in marine invertebrates.
- The findings support the hypothesis that MAPK-mediated suppression of sperm asters is a conserved mechanism across different species.
- Disruption of MAPK signaling impacts key events in fertilization and early embryonic development, including spindle organization and cytokinesis.