Dynamics of the human oocyte microrna transcriptome during maturation

Abstract

OBJECTIVE: One of the major functions of micro ribonucleic acid (miRNA) is to negatively regulate gene expression through messenger RNA (mRNA) degradation. Since mRNA degradation is one of the hallmarks of oocyte maturation, it is logical to hypothesize that miRNAs play an important role in this process. Therefore, this study sought to characterize expression of miRNAs in human germinal vesicle (GV), meiosis I (MI), and meiosis II (MII) oocytes for the first time. DESIGN: Descriptive study. MATERIALS AND METHODS: Eight GV, MI, and MII oocytes were evaluated. TaqMan real time PCR arrays were used to study expression levels of 667 miRNAs, representing the entire Sanger miRNA database (miRBase version 10.0). GV oocytes were used as the reference sample to identify miRNAs with significant (p<0.05) differential expression in MI and MII oocytes using a Student's t-test for each group. RESULTS: Seven miRNAs were significantly differentially expressed in the MI oocyte and 32 were significant in the MII oocyte relative to the GV stage. Two miRNAs were significantly downregulated in both MI and MII stage oocytes; hsa-miR-339-3p (-22 and -15 fold), and hsa-miR-744 (-140 and -40 fold), respectively. CONCLUSIONS: Analysis of the miRNA transcriptome has revealed novel miRNA expression patterns with significant regulation during oocyte maturation. Evaluation of their association with reproductive potential and expression at post-fertilization stages is ongoing. This report represents the first comprehensive analysis of miRNA expression in the human oocyte.