Regulation of gene expression during oocyte maturation and early embryo development

Abstract

Mammalian oocytes and embryos rely exclusively on maternal mRNAs to accomplish early developmental processes. Since oocytes and early embryos are transcriptionally silent after meiotic resumption, most of the synthesized maternal mRNA does not undergo immediate translation but is instead stored in the oocyte. Quantitative RT-PCR is commonly used to quantify mRNA levels, and correct quantification relies on reverse transcription and the choice of reference genes. Different methods for reverse transcription may affect gene expression determination in oocytes. In this study, we examined the suitability of either random or oligo(dT) primers for reverse transcription to be used for quantitative RT-PCR. We further looked for changes in poly(A) length of the maternal mRNAs during oocyte maturation. Our data indicated that depending on the method of reverse transcription, the optimal combination of reference genes for normalization differed. Surprisingly, we observed a shortening of the poly(A) tail lengths of maternal mRNA as oocytes progressed from GV to MII. Overall, our findings suggest dynamic maternal regulation of mRNA structure and gene expression during oocyte maturation and early embryo development.