Embryonic microRNAs are essential for bovine preimplantation embryo development

Area of Science:

• Reproductive Biology
• Developmental Biology
• Molecular Biology

Background:

• MicroRNAs (miRNAs) are small, noncoding RNAs regulating gene expression post-transcriptionally.
• miRNAs are present in oocytes and early embryos but their function in preimplantation development is unknown.
• Low levels of transcription occur before embryonic genome activation in preimplantation embryos.

Purpose of the Study:

• To determine the temporal expression pattern of miRNAs during bovine preimplantation development.
• To investigate the role of miRNAs in the transition from morula to blastocyst stages.
• To identify specific molecular mechanisms involving miRNAs in early embryonic development.

Main Methods:

• Small RNA sequencing was performed on bovine oocytes and preimplantation embryos at various stages (1-cell to blastocyst).
• α-amanitin was used to differentiate between maternal and embryonic miRNA expression.
• Gene silencing of DGCR8 using small-interfering RNA/morpholino was employed to assess miRNA function.

Main Results:

• Embryonic miRNA expression was first detected at the two-cell stage, increasing significantly by the morula and blastocyst stages.
• Knockdown of DGCR8 inhibited embryonic miRNA expression and impaired the morula-to-blastocyst transition.
• DGCR8 knockdown led to an increased abundance of potential miRNA target messenger RNAs.

Conclusions:

• Embryonic miRNAs are essential for successful bovine preimplantation development.
• miRNAs, particularly those regulated by DGCR8, play a critical role in the morula-to-blastocyst transition.
• These findings highlight the importance of post-transcriptional gene regulation by miRNAs in early embryogenesis.