Gene Expression of Monocarboxylate Transporters and Oocyte‐secreted Factors in Bovine Cumulus‐oocyte Complexes Selected by Brilliant Cresyl Blue

Abstract

Oocyte selection based on the brilliant cresyl blue (BCB) staining test has been successfully used to differentiate between competent and incompetent bovine oocytes. Here, the expression of genes involved in transport of monocarboxylates (Mct1-4) and oogenesis specific genes (Bmp15, Gdf9 and Has2) in BCB+ and BCB- selected immature and mature bovine cumulus-oocyte complexes (COC) was evaluated. In order to find specific molecular markers to characterize successful oocyte maturation, our study was also aimed at identifying the expression of Mcts and oogenesis specific genes in denuded oocytes and cumulus cells. Immature COCs morphological appropriate were (i) stained with 26 mm BCB for 90 min before IVM, (ii) exposed to same incubation conditions as stained COCs, but without BCB (holding group) or (iii) transferred into a maturation medium immediately after morphological selection (control group). mRNA expression was investigated by RT-PCR in COCs before and after IVM. No relationship was observed in the relative expression of Has2, Gdf9, Bmp15 or Mct1, 2 and 4 transcripts between BCB+ and BCB- COCs. Transcripts analysis showed that Gdf9 and Bmp15 in BCB+, BCB- and holding groups were up-regulated (p < 0.05) before IVM, while Has2 was up-regulated (p < 0.01) after IVM in the control group. Other genes remained stable during maturation (Mct1, 2 and 4). Our results showed, for the first time, Mct1, 2 and 4 expression in bovine COCs. Mct1 and Mct4 transcripts were present in denuded oocytes and cumulus cell, while Mct2 was detected only in cumulus cells. These differences between the three isoforms in localization suggest unique roles for each in monocarboxylate transport during maturation.

Effects of glucose metabolism pathways on nuclear and cytoplasmic maturation of pig oocytes

“…However, how lactate is metabolized in DOs and how pyruvate and lactate are utilized in CCs to support oocyte maturation was not observed in previous studies. Although expression of MCT has been observed in human and mouse 31 , bovine 32 and Xenopus www.nature.com/scientificreports www.nature.com/scientificreports/ oocytes 33 , and it is recently established that MPC is located in the inner mitochondrial membrane and plays an essential role in mitochondrial pyruvate uptake in somatic cells 34 , the function of MCT and MPC during oocyte maturation had not been systematically studied before our studies. Furthermore, studies on ETC in oocytes of different species are few [35][36][37] , and the role of NDUFV1, the first complex in ETC that accepts electrons from NADH and is critical for ATP generation, has not been observed in oocytes.…”