Transcript expression of mitochondria related genes is correlated with bovine oocyte selection by BCB test

This study was conducted in order to determine whether the level of G6PDH activity in immature bovine oocytes is correlated with the transcript expression of the mtDNA replication related genes, POLG, TFAM, NRF1 and mtDNA, encoded COX1 in immature and mature oocytes. G6PDH activity was assessed by the BCB test. Transcript level was assessed by real-time PCR. In immature oocytes, significant differences were noted in mRNA expression of three out of four of the genes analysed: TFAM mRNA expression differed (P<0.01) between BCB-, BCB+, and the control group; COX1 expression differed (P<0.05) between all analysed groups, and NRF1 transcript levels differed (P<0.01) between BCB- and BCB+, and between BCB- and the control group (P<0.05). No significant difference in transcript level of POLG gene between the analysed groups was noted. In mature oocytes, a significant difference (P<0.05) was noted only for mRNA level of TFAM gene between BCB- and BCB+, and between BCB- and the control group. The results suggest that immature BCB- oocytes do have significantly lower transcript level of genes involved in mitochondrial biogenesis, suggesting that this may be one of the reasons for their low developmental competence compared to BCB+ and control oocytes. Interestingly, we did not find significant differences in blastocyst rate between BCB+ and control oocytes. However, excluding BCB- oocytes from procedures relying on single oocyte can help in increasing the efficacy of the experiment. Our results showed a correlation between transcript level of mtDNA replication factors and G6PDH activity assessed by BCB staining in bovine oocytes.