Genes regulating programmed cell death are significantly upregulated in porcine immature oocytes

Correct maturation of the oocyte is crucial for further fertilization and embryogenesis. It comprises of both nuclear and cytoplasmic maturation, during which the proteins, nutrients and mRNAs are assembled. Cumulus cells are connected with the oocyte via gap-junctions, which enable bi-directional transfer of molecules, forming cumulus-oocyte complex (COC). The expression pattern in CCs is thought to resemble the genes expressed in the oocyte. The CCs surrounding the gamete of high developmental competence have an increased expression of apoptotic markers. Therefore, our aim in this study was to determine whether any apoptosis-related genes are upregulated in porcine oocytes before or after IVM. We isolated COCs from 45 pubertal crossbred gilts, performed brilliant cresyl blue (BCB) staining and analyzed the gene expression pattern in oocytes before and after IVM with the use of microarray analysis. The results include 419 differentially expressed transcripts, 25 of which belong to „regulation of apoptosis” and „regulation of cell death” GO BP terms. This set of genes includes BCLAF1, EIF2AK3, KLF10, MIF, MAP3K1, NOTCH2, TXNIP and APP, all of which have been upregulated in immature porcine oocytes. Our results suggest that they play part in porcine oocyte maturation and could be used as potential markers of female gamete’s developmental competence. This knowledge could serve as a basis to improve ART in pigs.