Function of the Mos/MAPK pathway during oocyte maturation in the Japanese brown frog Rana japonica

Area of Science:

• Cell Biology
• Developmental Biology
• Molecular Biology

Background:

• Oocyte maturation is crucial for fertilization and involves meiotic maturation, driven by maturation-promoting factor (MPF).
• The Mos/mitogen-activated protein kinase (MAPK) pathway is activated during vertebrate oocyte maturation, but its specific role varies across species.

Purpose of the Study:

• To investigate the function of the Mos/MAPK pathway in the oocyte maturation of the frog Rana japonica.
• To determine the pathway's necessity for maturation-promoting factor (MPF) activation and germinal vesicle breakdown (GVBD).

Main Methods:

• Injection of c-mos mRNA to activate the Mos/MAPK pathway in immature oocytes.
• Inhibition of Mos synthesis using c-mos antisense RNA.
• Inactivation of MAPK using CL100 phosphatase.
• Progesterone induction of oocyte maturation.

Main Results:

• MAPK activation occurred concurrently with MPF activation, but did not initiate MPF activation or GVBD when artificially activated in immature oocytes.
• Inhibiting Mos synthesis or MAPK activity did not prevent progesterone-induced MPF activation and GVBD.
• Continuous MAPK activation accelerated MPF activation, while MAPK inhibition delayed it.
• Mos induced cyclin B protein synthesis independently of MAPK, and MAPK stabilized cyclin B protein.

Conclusions:

• The Mos/MAPK pathway is not essential for initiating MPF activation and GVBD in Rana oocytes.
• The pathway's primary role is to enhance cyclin B translation via Mos and stabilize cyclin B protein through MAPK activity during oocyte maturation.