Transcription profile of candidate genes for the acquisition of competence during oocyte growth in cattle.

The aim of this study was to investigate the expression profile of candidate genes involved in competence during oocyte growth. The candidate genes (BMP15, OOSP1, H1FOO, H2A, H3A, H4, SLBP, DNMT1, DNMT3B, HAT1, HDAC2 and SUV39H1) were selected because of their possible involvement in determining oocyte developmental competence. Pre-antral and antral follicles were isolated from the ovaries of Zebu (Bos indicus) cows, measured and classified into the following categories according to their diameter: (i) oocytes from primordial follicles: diameter <20 μm, (ii) oocytes from primary follicles: 25-35 μm, (iii) oocytes from small secondary follicles: 40-60 μm, (iv) oocytes from large secondary follicles: 65-85 μm, (v) oocytes from small antral follicles: 100-120 μm, and (vi) oocytes from large antral follicles: >128 μm. Total RNA was extracted from four pools of 25 oocytes for each category of follicles, and the genes were quantified by qPCR. Target gene expression was normalized using the gene PPIA. The results suggest that stocks of the studied transcript genes accumulate before the final phase of folliculogenesis. The HDAC2 gene was the only gene in which a differential expression was observed at stage associated with competence acquisition.