MicroRNA-27a activity is not suppressed in porcine oocytes.

MicroRNAs (miRNAs) are a class of small noncoding RNAs involved in multiple cellular processes. Recent findings indicate that miRNA activity is globally suppressed in mouse oocytes. However, whether miRNAs are expressed and function in porcine oocytes remains unknown. In this study, our aims were to ascertain if miRNA biogenesis occurs and whether miRNA activity is globally suppressed during porcine oocyte maturation. First, to identify if miRNA biogenesis occurred, a TaqMan low-density array containing 365 mature human miRNAs was used to examine miRNA expression. This analysis revealed dynamic changes in miRNA expression, suggesting miRNA biogenesis during porcine oocyte maturation. Then, to identify if miRNA activity was globally suppressed in porcine oocytes, we focused on miR-27a, which functions in the cell cycle. miR-27a was found to facilitate the first cleavage and repress the translation of its messenger RNA target (MAP2K4), suggesting that miR-27a activity was not suppressed in porcine oocytes. Taken together, our results suggest that miRNA activity was not globally suppressed in porcine oocytes, at least for miR-27a. However, because we only investigated the activity of miR-27a, further experiments are definitely required to ascertain this point.