Early meiotic-specific protein expression in post-natal rat ovaries

Recent studies in mice challenged the basic doctrine that most mammalian females lose neo-oogenesis in post-natal ovaries. In order to provide more information in other species, we examined post-natal rat ovaries by histological sections and detected the germline cell marker protein RVLG (rat vasa-like gene), BrdU (5-bromodeoxyuridine) incorporation in RVLG-expressing cells, for identification of germline cells undergoing mitosis and meiosis in the ovarian surface epithelium (OSE). We also detected the expression of early meiotic-specific proteins disruption of meiotic control 1 (DMC1), stimulated by retinoic acid gene 8 (STRA8) and synaptonemal complex protein 3 (SCP3) by immunohistochemical analysis and Western blotting, and the transcript of SCP1, SCP3 and Sporulation-specific protein 11 (SPO11) by RT-PCR in the post-natal ovarian cortex. However we failed in detecting large ovoid cells in the OSE, which may represent the putative germline stem cells (GSCs) that are supposed to sustain neo-oogenesis, and the transcription of the meiotic-specific genes SCP1, SCP3 and SPO11 by RT-PCR as well as the translation of DMC1, STRA8 and SCP3 by Western blotting. Our data support the postulation that there is no neo-oogenesis occurring in the OSE of rat post-natal ovary through meiosis of GSCs.