Dual Regulation In Expression Of Germ Cell Specific Genes By DNA Methylation And Transcription Factors

Only a few genes were identified for primodial germ cell (PGC) early specification, including Blimpl, Stella, Vasa and Dazl. In additon, it is difficult to obtain enough PGCs for research purpose. On the contrary, embryonic stem cells (ESCs) in vitro differentiation system provides an efficient model for PGC formation.The thesis includes two parts:in the first part, we screened candidate genes, including Sohlhl,Sohlh2,Fgd1and Fkbp3using ESC in vitro differentiation system, and found that Sohlh2,Fgd1and Fkbp3had no effect on the ES differentiation into PGC, while Sohlhl promoted ESCs to differentiate into PGCs. In the second part of this study, we sought to investigate how the expression germ cell specific genes was regulated by transcription factors and DNA methylation. We found that the transcription factor. Nrf1(nuclear respiratory factor1) bound to the promoter of a germ cell specific gene, Aszl and modulated its expression, confirmed by luciferase assay. In addition, the promoter of Aszl was enriched in CpG in Nrf1binding sites. We further confirmed that Aszl expression was modulated by DNA methylation. Furthermore, we analysed the promoters of several other germ cell specific genes and found that there were also Nrfl binding sites in genes Ddx25and Lin28promoters. We observed that Nrf1promoted the expression of gene Ddx25and Lin28by luciferase assay. When Ddx25promoter was methylated in vitro, the increase disappeared. The same phenomena were observed in promoter of Vasa regulated transcription factor Oct1. We therefore concluded that Nrf1and Oct1likely had an important effect on germ cell genes. Our study will shed light on the epigenetic modification of germ cell gene expression.