Mechanism Of Oogonia Meiotic Entry And Lhx8Regulated Follicle Formation In Mice

One of the basic life processes for eucaryotes is the formation sperm and eggs from primoridial germ cells (PGCs) through the process of meiosis. And primary oocytes formation by meiotic entry of primodial germ cells is of vital importance and prior to subsequent follile formation and development as well as oocyte maturation processes in female mammalian. Studies shown that Brefeldin A, a protein transport inhibitor, could affect meiosis of oocyte. In the present study, we isolated fetal genital ridge from11.5dpc embryos and cultured them based on our in vitro system for fetal gonad after BFA treatment. Results of synaptonemal complex analysis and quantitative PCR showed that BFA can facilitate the process of oocytes meiosis. After renal capsule transplantation, normal oocytes within growing follicles were observed in BFA treated ovaries. In conclution, our study proved that BFA could induce the meiotic initiation of mouse oogonium, and provided a in vitro model for further study of the mechanism of meiotic entry.The spatial and temporal specific activation and inhibition of numerous genes are required for successful oogenesis which are precisely regulated by germ cell related transcription factors, and appropriate epigenetic modifications which closely regulates the functional exertion of these transcription factors. In this study, we characterized the relativity between the expression and epigenetic dynamics of Lhx8, a germ cell specific transcription factor during mouse oogenesis. Immunohistochemistry, quantitative PCR and western blots were peformed to localize and quantify the expressional characteristics of Lhx8in oocytes of13.5dpc (day post coitum),17.5dpc,0dpp (day post partum),3dpp,7dpp and14dpp. The results showed that LHX8protein located in the nucleus of oocytes is increasingly expressed during primordial follicle activation. Sequencing of bisulfite-converted genomic DNAs revealed that the methylation dynamics of Lhx8-3’ was highly changeable but almost no change took place in Lhx8-5’. ChIP-QPCR analysis depicted histone H3acetylation of Lhx8also increased during primordial follicle assembly and activation. In conclusion, peak Lhx8expression alluded its role in the activation of primordial follicles, which highly correlated with the demethylation of Lhx8-3’ untranslated region and the high acetylation level of histone H3.