Expression of peroxiredoxins in bovine oocytes and embryos produced in vitro

Peroxiredoxins (PRDXs) form a family of peroxidases involved in antioxidant protection and cell signaling. Due to their peroxide reductase activity, these enzymes might be involved in fine-tuning peroxide levels in embryos during in vitro production. In this study, RT-PCR was used to examine the expression of the six PRDX isoforms (PRDX1 to PRDX6) in bovine oocytes and embryos. PRDXs were detected in oocytes both before and after in vitro maturation. Besides, PRDX6 was up-regulated after maturation. Single embryos were analyzed from the two-cell to the blastocyst stages. PRDX1 and PRDX5 transcripts were detected throughout development. PRDX2, PRDX3, and PRDX6 were not expressed around the 9- to 16-cell stage. PRDX4 transcripts were weakly detected in pools of embryos from the 9- to 16-cell stage onwards. In situ immunodetection of PRDX5, which was previously reported to exhibit the widest subcellular distribution among PRDXs in adult mammalian cells, showed a mitochondrial distribution pattern in the bovine embryo. Finally, the potential modulation by oxidative stress of PRDX expression around the major embryonic genome activation was evaluated by culturing embryos under 20% O2 instead of 5%. No significant difference in the pattern of PRDX expression was observed under 20% O2. In conclusion, our data show for the first time that PRDXs are expressed in mammalian oocytes and early embryos. Moreover, the bovine transcripts exhibit various patterns of expression that might be related to the potential role of PRDXs in oocyte maturation and embryo development.