Biological studies on expression and function of Ig related molecules and zona pellucida in mammalian gametes

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We have found that MHC classII antigen and CD4/p561ck complex were expressed on sperm posterior membrane and egg plasma membrane respectively. Furthermore, we generated the CD4 proteins on Sf9 cells transfected with AcNPV-CD4 cDNA.Then, the intercellular interactions between Sf9-CD4 cells and sperm cells demonstrated the adhesive reactions in the species specific manner.On the other hand, we have demonstrated the expression of Fas-Fas ligand (FasL) system and revealed its roles for the formation of atresia in murine ovary. By means of in situ hybridization and RT-PCR,the expression of Fas was mainly detected at transcriptional levels on oocytes, hyperovulated eggs and some granulosa cells, whereas, that of FasL was localized on granulosa cells. These results were further confirmed at translational levels by IIF,EIA and immunoprecipitation method. The expression of Fas-FasL system in ovary was regulated by gonadotropins. We also constructed the transfectants of AcNPV-FasL cDNA to Sf9 (Sf9-FasL) cells. The interaction between granulosa/Sf9-FasL cells and ZP free eggs in vitro resulted in the induction of apoptosis in eggs detecting by TUNEL method. In contrast, the apoptosis in ZP intact eggs in this system did not occur. Taken together with our experimental results and other investigator's reports, the formation of ovarian atresia was strongly suggested to be induced by the interaction between FasL positive granulosa cells and Fas expressing oocytes/eggs during oogenesis until the accomplishment of ZP.