Expression And Localization Of Meiosis-associated Protein In Gonads Of Female And Male Rats At Different Stages

Objective: There was a critical process in the development of eukaryotic gonads that the germ cells entered into meiosis.Meiosis was a unique way of cell division in germ cells,and was closely related to the expression of many genes and proteins during the process,the stimulated by retinoic acid gene 8(STRA8),the Synaptonemal Complex Protein(SCP3)and the deleted in azoospermia-like(DAZL)played critical role of regulation in the differentiation of mammalian germ cells,however,the regulatory mechanism was different for different species or the same species at different developmental stages.Studies from model animal mice suggested that the germ cells entered meiosis at different times in male and female mice,germ cells in the mouse ovary entered meiotic prophase during embryogenesis,whereas germ cells in the embryonic testis arrested mitotic cell cycle and did not enter meiosis until after birth,but the same response signal of RA-STRA8 was used when female and male mice entered meiosis.whether STRA8,SCP3 and DAZL had the similar expression characteristics during the meiosis initiation process in common animal rats of reproductive biology had not been reported.The purpose of this study was to investigate the expression and localization of STRA8,SCP3 and DAZL in the gonads of male and female rats at different stages,and to understand the molecular mechanism of meiosis initiation of germ cells in male and female mammals.Methods: In this study,female and male SD rats were selected,the SD rats were divided into two developmental phases: the embryonic gonads and the gonads after birth.To establish timed mating,female rats were caged with males overnight,the rats who were pregnant for 12.5 dpc to 16.5 dpc were anesthetized,and the rat embryonic gonads were placed,the one side tissues were fixed in Bouin's solution to make paraffin sections,and other side was placed in cryopreservation tube of liquid nitrogen to extract total RNA and total protein.Similarly,the ovaries and testes on both sides of 1 d,2 d,5 d and 7 d after birth were collected.The expression and localization of STRA8,SCP3 and DAZL was detected by q RT-PCR,Western Blot and immunohistochemistry.Results:1.Immunohistochemistry results showed that STRA8 was mainly expressed in the cytoplasm of embryonic germ cells in female SD rats,and it was also expressed in the cytoplasm and nucleus of the the postnatal day of 2 in ovary.SCP3 protein was mainly expressed in the nucleus of embryonic germ cells.And DAZL was expressed in female germ cells,which was feeble in the embryonic stage and significantly increased after birth.In male rats,STRA8 and SCP3 were mainly expressed after birth,DAZL,STRA8 and SCP3 were all expressed in germ cells,and DAZL was expressed at low levels in embryonic germ cells,STRA8 was expressed in spermatogonia and SCP3 was expressed in spermatocytes after birth.2.qRT-PCR results showed that the mRNA levels of STRA8 and SCP3 were mainly increased during the embryonic period in female rats,and the mRNA levels of STRA8 and SCP3 increased after birth compared to the embryonic stage in male rats.The mRNA level of DAZL increased after birth in male and female rats,and the expression of DAZL was expressed at low levels from 12.5 dpc to 16.5 dpc in the embryonic stage.3.Western Blot results showed that the protein levels of STRA8 and SCP3 were mainly increased during the embryonic period in female rats,and the protein levels of STRA8 and SCP3 increased after birth compared to the embryonic stage in male rats.The protein level of DAZL increased after birth in male and female rats,and the expression of DAZL was expressed at low levels from 12.5 dpc to 16.5 dpc in the embryonic stage.Conclusion: The expression of STRA8 and SCP3 indicated germ cells enter meiosis in female rats embryo,and STRA8 and SCP3 could serve as molecular markers for the meiosis in rats.And the localization of STRA8 in the nucleus increased the possibility that STRA8 might act as transcription factor or activate transcription to function after birth.The localization and expression of STRA8 and SCP3 in male rats proved that germ cells meiosis in the embryonic testis arrested and meiosis was restored after birth.The expression of DAZL on germ cells of male and female rats suggested that DAZL could be used as a marker gene for germ cells.This study provided differences in the onset of meiosis between males and females,and provided morphological basis for enriching related meiotic regulation mechanisms.