Expression of Fas and Fas ligand mRNA in rat and human preimplantation embryos

The Fas-Fas ligand (L) system is one of the major signalling pathways to in duce apoptosis in various cells and tissues, The aim of this study was to i nvestigate the expression of the Fas-Fas L system in rat and human oocytes and preimplantation embryos. We determined the expression of Fas and Fas L mRNA of rat oocytes and embryos up to the blastocyst stage, and of human em bryos at the 2- or 4-cell stage, using reverse transcription polymerase cha in reaction (PCR) and nested PCR techniques, Moreover, we investigated the expression of Fas mRNA in human fragmented embryos. In rat embryos, Fas mRN A was expressed at the 2-cell stage only, whereas Fas L mRNA was expressed in oocytes, and at the pronuclear (1-cell) and 2-cell stages, In human embr yos, Fas mRNA was expressed at the 4-cell stage only, whereas Fas L mRNA wa s expressed at both 2- and 4-cell stages, Human fragmented embryos expresse d both Fas and Fas L mRNA, Because simultaneous expression of Fas and Fas L mRNA occurred in 2-cell rat embryos and in 4-cell human embryos, the Fas-F as L system might be involved in the apoptotic pathway in the early embryos of these species.