GREM1, EGFR, and HAS2; the oocyte competence markers for improved buffalo embryo production in vitro

Selection of competent oocytes is crucial for successful in vitro embryo production and correlating expression profile of oocyte competence markers in cumulus cells with oocyte quality is an important preamble. In the present study, expression profile of oocyte competence markers (GREM1, EGFR, HAS2, and TNFAIP6) was correlated through brilliant cresyl blue (BCB) staining and subsequently with in vitro embryo production. Excellent to good quality buffalo, cumulus oocyte complexes (COCs) were stained with BCB (26 μM) and based on the blue coloration of cytoplasm COCs were divided in two groups as BCB(+ve) and BCB(-ve). Mean percentage of BCB(+ve) oocytes was significantly higher (P < 0.05) than BCB(-ve) oocytes (56.79 ± 1.22 vs. 43.20 ± 1.22), the mean oocyte diameter was also significantly larger (P < 0.05) for the BCB(+ve) group than that of BCB(-ve) group (145.7 ± 1.8 μm vs. 132.7 ± 1.9 μm). The cleavage rate (%), blastocyst rate (%), and total cell number was significantly (P < 0.05) higher in BCB(+ve) than BCB(-ve) group (71.15 ± 2.17 vs. 52.89 ± 2.65; 31.58 ± 1.11 vs. 7.73 ± 0.97, and 93.14 ± 2.42 vs. 71.42 ± 2.09, respectively). Relative mRNA expression of marker genes in cumulus cells increased significantly (P < 0.05) after maturation viz. GREM1 (10.13 folds), EGFR (9.04 folds), HAS2 (27.91 folds), and TNFAIP6 (64.81 folds). Brilliant cresyl blue positive oocytes showed significantly higher (P < 0.05) expression of GREM1, EGFR, and HAS2 transcripts than BCB(-ve) oocytes, however, no significant change in the expression of TNFAIP6 gene was observed. It is concluded from the study that GREM1, EGFR, and HAS2 could be used as molecular markers of oocyte competence for an improved buffalo embryo production in vitro.