Comparison of RNA extraction and microRNA detection protocols for a small amount of germinal vesicle oocytes in bovine

RT-qPCR is a widely used method to detect miRNA expression. Compared with mRNA, miRNA has a shorter length and lower abundance which hinders the acquisition of reliable results. Thus, miRNA detection requires a method with high sensitivity and accuracy. Collecting large amounts of material is particularly difficult for oocytes and pre-implantation embryos of domestic animals. Establishing a set of miRNA detection methods that are suitable to detect trace amounts of such materials is urgently needed. In this study, the total RNA in 50 germinal vesicle (GV) oocytes was isolated through direct lysis and by using mirVana miRNA Isolation Kit and miRNeasy Micro Kit. The OD260/280 values and concentrations of the RNA in these three groups were compared to identify a superior RNA isolation method. In addition, the specificity and sensitivity of common DNA and LNA primers were compared by real-time quantitative polymerase chain reaction for miRNA detection. Results show that the RNA concentration of in the direct lysis group was significantly higher than that in the other two groups. The specificity between the DNA primers and LNA primers was identical, whereas the sensitivity of LNA primers was superior to that of DNA primers. These results suggest that direct lysis combined with LNA primers might be a suitable protocol for the miRNA detection of a small amounts of GV oocytes and pre-implantation embryos in cattle.