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Updated: Jun 16, 2026
Meiotic Spindle Assessment in Mouse Oocytes by siRNA-mediated Silencing
Published on: October 11, 2015
MicroRNA activity is suppressed in mouse oocytes
Jun Ma1, Matyas Flemr, Paula Stein
1Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018, USA.
Abstract:
MicroRNAs (miRNAs) are small endogenous RNAs that typically imperfectly base pair with 3' untranslated regions (3'UTRs) and mediate translational repression and mRNA degradation. Dicer, which generates small RNAs in the miRNA and RNA interference (RNAi) pathways, is essential for meiotic maturation of mouse oocytes. We found that 3'UTRs of transcripts upregulated in Dicer1(-/-) oocytes are not enriched in miRNA binding sites, implicating a weak impact of miRNAs on the maternal transcriptome. Therefore, we tested the ability of endogenous miRNAs to mediate RNA-like cleavage or translational repression of reporter mRNAs. In contrast to somatic cells, endogenous miRNAs in oocytes poorly repressed translation of mRNA reporters, whereas their RNAi-like activity was much less affected. Reporter mRNA carrying let-7-binding sites failed to localize to P body-like structures in oocytes. Our data suggest that miRNA function is downregulated during oocyte development, an idea supported by normal meiotic maturation of oocytes lacking Dgcr8, which is required for the miRNA but not the RNAi pathway (Suh et al. [1], this issue of Current Biology). Suppressing miRNA function during oocyte growth is likely an early event in reprogramming gene expression during the transition of a differentiated oocyte into pluripotent blastomeres of the embryo.
Insights
MicroRNA (miRNA) function is downregulated in mouse oocytes, with impaired translational repression but retained RNA interference-like activity. This suggests a crucial role in early embryonic development and reprogramming gene expression.
Area of Science:
- Developmental Biology
- Molecular Biology
- Genetics
Background:
- MicroRNAs (miRNAs) are key regulators of gene expression, mediating translational repression and mRNA degradation.
- Dicer is essential for miRNA biogenesis and meiotic maturation in mouse oocytes.
- The impact of miRNAs on the maternal transcriptome during oocyte development is not fully understood.
Purpose of the Study:
- To investigate the functional activity of endogenous miRNAs in mouse oocytes.
- To determine whether miRNAs regulate the maternal transcriptome through translational repression or mRNA degradation.
- To explore the role of miRNA downregulation in oocyte development and early embryogenesis.
Main Methods:
- Analysis of 3'UTRs in Dicer1(-/-) oocytes to assess miRNA binding site enrichment.
- Use of reporter mRNAs to test endogenous miRNA activity (translational repression and RNAi-like cleavage) in oocytes.
- Localization studies of reporter mRNAs in P body-like structures within oocytes.
Main Results:
- 3'UTRs of upregulated transcripts in Dicer1(-/-) oocytes showed no enrichment of miRNA binding sites.
- Endogenous miRNAs in oocytes exhibited poor translational repression of reporter mRNAs compared to somatic cells.
- RNA interference-like activity of miRNAs was less affected in oocytes.
- Reporter mRNAs with let-7 binding sites failed to localize to P body-like structures in oocytes.
- Oocytes lacking Dgcr8, essential for miRNA biogenesis, underwent normal meiotic maturation.
Conclusions:
- miRNA function, particularly translational repression, is significantly downregulated during mouse oocyte development.
- This downregulation is likely an early event in the reprogramming of gene expression from differentiated oocytes to pluripotent blastomeres.
- The findings support a model where suppressed miRNA activity facilitates the transition to embryonic pluripotency.
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