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Okadaic acid-sensitive phosphatase is related to MII/G1 transition in mouse oocytes

Naoko Moride1, Akira Kuwahara, Ayako Sutoh

  • 1Department of Obstetrics and Gynecology, University of Tokushima, Institute for Health Biosciences, 3-18-15 Kuramoto Tokushima 770-8503, Japan.

Zygote (Cambridge, England)
|February 11, 2011
PubMed

Insights

Okadaic acid (OA) inhibits phosphatases, preventing mouse oocyte maturation by maintaining high M phase-promoting factor (MPF) and MAPK activity and blocking cdc25c dephosphorylation during the MII/G1 transition.

Area of Science:

  • Cell Biology
  • Reproductive Biology
  • Molecular Biology

Background:

  • Okadaic acid (OA)-sensitive phosphatases are linked to MAPK/p90rsk activation in mammalian oocytes.
  • OA influences the MPF and cdc25c feedback loop in Xenopus oocyte maturation.
  • The role of OA-sensitive phosphatase inhibition in MPF and MAPK activity during the MII/G1 transition in oocytes is unclear.

Purpose of the Study:

  • To investigate the relationship between OA-sensitive phosphatase and the MII/G1 transition in mouse oocytes.
  • To determine the effect of OA on MPF and MAPK activities during oocyte maturation.

Main Methods:

  • Mouse oocytes were cultured in the presence or absence of OA (2.5 μM).
  • MPF and p42 MAPK activities were assessed by measuring Histone H1 and myelin basic protein kinase activities, respectively.
  • cdc25c phosphorylation was analyzed using western blotting.

Main Results:

  • OA treatment prevented pronucleus formation, indicating blocked MII/G1 transition.
  • OA significantly inhibited the decrease in MPF and MAPK activities observed in control oocytes.
  • OA addition blocked cdc25c dephosphorylation at 7 hours post-insemination.

Conclusions:

  • OA-sensitive phosphatase activity is crucial for the inactivation of MPF and MAPK during the MII/G1 transition in mouse oocytes.
  • Inhibition of OA-sensitive phosphatases disrupts oocyte maturation by maintaining key cell cycle regulators in their active states.

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