Identification of Fas antigen associated with apoptotic cell death in murine ovary.

The majority of ovarian follicles including oocytes undergo atresia through a mechanism involving apoptotic cell death. The mechanisms underlying atresia remain to be clarified. In the present study, we detected the expression of the Fas antigen (Fas), which is a cell-surface protein to modulate apoptosis, in murine ovarian oocytes and hyperovulated eggs as well as in several control tissues. Substantial decline in Fas mRNA was found in atretic follicles which were injected with pregnant mare's serum gonadotropin (PMSG) on day 3. The observed decreases in mRNA of Fas could not be attributed to a generalized degradation of cellular RNA during atresia, as evidenced by the presence of intact 18S and 28S ribosomal RNA as well as constitutive expression of EF-1 alpha mRNA in atretic follicles. The data obtained indicate that apoptotic cell death of oocytes seemed to be associated with internucleosomal DNA fragmentation regulated by Fas molecule expressed in atretic ovarian follicles.