EED is required for Mouse Primordial Germ Cell Differentiation in the Embryonic Gonad

Development of Primordial germ cells (PGCs) is required for reproduction. During PGC development in mammals, major epigenetic remodeling occurs which is hypothesized to establish an epigenetic landscape for sex-specific germ cell differentiation and gametogenesis. In order to address the role of Embryonic Ectoderm Development (EED) and Histone 3 lysine 27 trimethylation (H3K27me3) in this process, we created a conditional deletion in EED and show that EED is essential for regulating the timing of sex-specific PGC differentiation in both ovaries and testes, as well as X chromosome dosage decompensation in testes. Integrating chromatin and whole genome bisulfite sequencing of epiblast and PGCs, we identified a poised repressive signature of H3K27me3/DNA methylation which we propose is established in the epiblast where EED and DNMT1 interact. Thus, EED joins DNMT1 in regulating the timing of sex-specific PGC differentiation during the critical window when the gonadal niche cells specialize into an ovary or testis. Overall design: Examination of Transcription and DNA methylation in control and PGC-specific EED conditional knockout primordial germ cells