Fyn and argonaute 2 participate in maternal-mRNA degradation during mouse oocyte maturation

Area of Science:

• Reproductive Biology
• Molecular and Cellular Biology
• Genetics and Genomics

Background:

• Fertilization initiates maternal mRNA degradation, replaced by embryonic transcripts.
• Argonaute 2 (AGO2) is implicated in post-fertilization maternal mRNA decay, but its role during oocyte maturation is unclear.
• Fyn, a Src family kinase (SFK), is crucial for oocyte maturation and inhibits AGO2 in other cell types.

Purpose of the Study:

• To investigate the roles of Fyn and AGO2 in maternal mRNA degradation during mouse oocyte maturation.
• To determine if Fyn/SFKs stabilize maternal mRNAs at the germinal vesicle (GV) stage.
• To elucidate the involvement of Fyn and AGO2 in promoting physiological maternal mRNA degradation during oocyte maturation.

Main Methods:

• Mouse oocytes at the germinal vesicle (GV) stage were treated with SU6656 (SFKs inhibitor), DN-Fyn RNA, or BCl-137 (AGO2 inhibitor).
• Quantitative PCR (qPCR) was used to measure the expression levels of nine key maternal mRNAs.
• Analysis was performed on oocytes at the GV stage and following *in vivo* maturation.

Main Results:

• Fyn/SFKs maintain the stability of at least four maternal mRNAs at the GV stage; AGO2 has no role at this stage.
• During *in vivo* oocyte maturation, eight maternal mRNAs were significantly degraded.
• AGO2 inhibition prevented the degradation of at least five maternal mRNAs.
• Fyn/SFK inhibition prevented the degradation of at least five Fyn maternal mRNAs and two SFKs maternal mRNAs, indicating their role in promoting degradation.

Conclusions:

• Fyn/SFKs are involved in stabilizing maternal mRNAs in oocytes at the GV stage.
• Fyn, SFKs, and AGO2 collectively participate in the physiological degradation of maternal mRNAs during oocyte maturation.
• These findings highlight the dynamic regulation of maternal mRNA turnover essential for successful oogenesis and early embryogenesis.