Fas expression and mediated activation of an apoptosis programme in bovine follicular granulosa cells in vitro

The Fas antigen is a transmembrane receptor that can trigger apoptosis in a variety of somatic cells. Ovarian follicular atresia and luteolysis are thought to occur by apoptosis. To reveal the intracellular signal transduction molecules involved in the process of follicular development in the bovine ovary, Fas gene without the stop codon was amplified in the present study using RT-PCR and directly cloned into the eukaryotic expression vector pAcGFP-N1. The resultant recombinant plasmid pAcGFP-bFas was then transfected into bovine follicular granulosa cells. Expression of AcGFP was observed under fluorescent microscopy, and the transcription and translation of Fas were detected by RT-PCR and western blot analysis. The methyl-tetrazolium (MTT) assay, Hoechst33342 staining and DNA ladder method were performed to determine the growth inhibition and apoptosis of the cells. The results showed that GFP expression was detected as early as 24 h after transfection. The Fas fusion gene was successfully expressed in granulosa cells as evidenced by the detection of a 994-bp fragment corresponding to the Fas mRNA by RT-PCR and a 64.5-kD band corresponding to the Fas fusion protein by western blot. Granulosa cell viability decreased significantly at 72 h after transfection, and the apoptosis rate of the cells transfected with pAcGFP-Fas was significantly higher than that of the control group. Cells in the Fas transfection group showed ladder patterns characteristic of apoptosis, and the nuclei were shrunken and densely hyperchromatic or fragmented, suggesting that Fas is capable of inhibiting the proliferation of bovine follicular granulosa cells and inducing cell apoptosis when over-expressed. This study will aid in further understanding the mechanism of regulation of Fas on bovine oocyte formation and development.