Role of miRNAs in Bovine Oocyte Maturation and Reproductive Regulation

Abstract

MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs that regulate target gene expression in many eukaryotes. MiRNAs are essential for post-transcriptional regulation, influencing various biological functions, including oocyte growth and maturation, fertilization, early embryo development, and implantation. In recent decades, numerous studies have identified a substantial number of miRNAs associated with mammalian oocyte maturation and early embryo development, utilizing methods such as small RNA sequencing and modulating miRNA expression through overexpression or inhibition. In this review, we introduce the biosynthesis of miRNAs and their regulatory roles in germ cells, summarizing the expression patterns and post-transcriptional regulation of miRNAs during bovine oocyte maturation and early embryo development, as well as their potential application in bovine assisted reproductive technology (ART).

Keywords: ART; bovine; embryo development; miRNA; oocyte maturation.

Figure 1

Canonical pathway of miRNAs biosynthesis. Within the nucleus, miRNAs are initially transcribed by RNA polymerase II into pri-miRNAs. The enzyme Drosha forms microprocessor complexes with DGCR8, cleaving pri-miRNA to produce pre-miRNAs. The complexes cleave the pri-miRNA into pre-miRNAs, which are transported to the cytoplasm by Exportin-5. In the cytoplasm, the Dicer complex cleaves the pre-miRNAs, leading to mature miRNAs. The mature miRNAs then interfere with the translation mechanisms by binding to complementary target sequences in the 3′-untranslated region (3′-UTR) of the mRNA, leading to translation inhibition or mRNA degradation.

Figure 2

MiRNAs regulate bovine oocyte maturation and preimplantation embryo development. GV: germinal vesicle; MI: metaphase I; MII: metaphase II.