Timely translation during the mouse oocyte-to-embryo transition

Area of Science:

• Developmental Biology
• Molecular Biology
• Genetics

Background:

• Oocyte maturation and early embryonic development in mice are transcriptionally silent.
• These processes rely on maternal messenger RNAs (mRNAs) stored during oocyte growth.
• The 3' untranslated regions (UTRs) of these maternal mRNAs play a critical role in regulating their translation and stability.

Purpose of the Study:

• To investigate the role of Spin gene 3'UTRs in regulating transcript polyadenylation and translation during the oocyte-to-embryo transition.
• To determine how differential transcript stability and translational control contribute to the initiation of development.

Main Methods:

• Injection of beta-galactosidase-tagged reporter transcripts with different Spin 3'UTRs into mouse oocytes and zygotes.
• Monitoring beta-galactosidase activity to assess translation.
• Northern blot analysis to monitor the stability and polyadenylation of maternal transcripts.
• Bioinformatic survey of 3'UTRs for cytoplasmic polyadenylation elements (CPEs).

Main Results:

• Differential polyadenylation and translation of Spin transcripts occur at oocyte maturation and fertilization, dependent on 3'UTR sequences.
• Maternal transcripts exhibit varying stability, and polyadenylation correlates with the presence of CPEs near the nuclear polyadenylation signal.
• Approximately one-third of mouse 2-cell stage cDNAs contain CPEs in their 3'UTRs.

Conclusions:

• Sequences within the 3'UTR are critical for regulating maternal mRNA fate during early development.
• Differential transcript stability and a translational control program involving CPEs provide the necessary protein diversity for oocyte maturation and embryonic development initiation.
• This regulatory mechanism ensures successful progression from oocyte to embryo without new transcription.