Polycomb protein EED is required for silencing of pluripotency genes upon ESC differentiation.

Eed (embryonic ectoderm development) is a core component of the Polycomb Repressive Complex 2 (PRC2) which catalyzes the methylation of histone H3 lysine 27 (H3K27). Trimethylated H3K27 (H3K27me3) can act as a signal for PRC1 recruitment in the process of gene silencing and chromatin condensation. Previous studies with Eed KO ESCs revealed a failure to down-regulate a limited list of pluripotency factors in differentiating ESCs. Our aim was to analyze the consequences of Eed KO for ESC differentiation. To this end we first analyzed ESC differentiation in the absence of Eed and employed in silico data to assess pluripotency gene expression and H3K27me3 patterns. We linked these data to expression analyses of wildtype and Eed KO ESCs. We observed that in wildtype ESCs a subset of pluripotency genes including Oct4, Nanog, Sox2 and Oct4 target genes progressively gain H3K27me3 during differentiation. These genes remain expressed in differentiating Eed KO ESCs. This suggests that the deregulation of a limited set of pluripotency factors impedes ESC differentiation. Global analyses of H3K27me3 and Oct4 ChIP-seq data indicate that in ESCs the binding of Oct4 to promoter regions is not a general predictor for PRC2-mediated silencing during differentiation. However, motif analyses suggest a binding of Oct4 together with Sox2 and Nanog at promoters of genes that are PRC2-dependently silenced during differentiation. In summary, our data further characterize Eed function in ESCs by showing that Eed/PRC2 is essential for the onset of ESC differentiation.

Androgenetic embryonic stem cells form neural progenitor cells in vivo and in vitro.

Uniparental zygotes with two paternal (androgenetic [AG]) or two maternal (gynogenetic [GG]; parthenogenetic [PG]) genomes are not able to develop into viable offspring but can form blastocysts from which embryonic stem cells (ESCs) can be derived. Although some aspects of the in vitro and in vivo differentiation potential of PG and GG ESCs of several species have been studied, the developmental capacity of AG ESCs is much less clear. Here, we investigate the potential of murine AG ESCs to undergo neural differentiation. We observed that AG ESCs differentiate in vitro into pan-neural progenitor cells (pnPCs) that further give rise to cells that express neuronal- and astroglial-specific markers. Neural progeny of in vitro-differentiated AG ESCs exhibited fidelity of expression of six imprinted genes analyzed, with the exception of Ube3a. Bisulfite sequencing for two imprinting control regions suggested that pnPCs predominantly maintained their methylation pattern. Following blastocyst injection of AG and biparental (normal fertilized [N]) ESCs, we found widespread and evenly distributed contribution of ESC-derived cells in both AG and N chimeric early fetal brains. AG and N ESC-derived cells isolated from chimeric fetal brains by fluorescence-activated cell sorting exhibited similar neurosphere-initiating cell frequencies and neural multilineage differentiation potential. Our results indicate that AG ESC-derived neural progenitor/stem cells do not differ from N neural progenitor/stem cells in their self-renewal and neural multilineage differentiation potential. Disclosure of potential conflicts of interest is found at the end of this article.