Geminin cooperates with Polycomb to restrain multi-lineage commitment in the early embryo

Abstract

SUMMARYTransient maintenance of a pluripotent embryonic cell population followed by the onset of multi-lineage commitment is a fundamental aspect of development. However, molecular regulation of this transition is not well characterized in vivo. Here, we demonstrate that the nuclear protein Geminin is required to restrain commitment and spatially restrict mesoderm, endoderm and non-neural ectoderm to their proper locations in the Xenopus embryo. We used microarray analyses to demonstrate that Geminin overexpression represses many genes associated with cell commitment and differentiation, while elevating expression levels of genes that maintain pluripotent early and immature neurectodermal cell states. We characterized the relationship of Geminin to cell signaling and found that Geminin broadly represses Activin-, FGF-and BMP-mediated cell commitment. Conversely, Geminin knockdown enhances commitment responses to growth factor signaling and causes ectopic mesodermal, endodermal and epidermal fate commitment in the embryo. We also characterized the functional relationship of Geminin with transcription factors that had similar activities and found that Geminin represses commitment independent of Oct4 ortholog (Oct25/60) activities, but depends upon intact Polycomb repressor function. Consistent with this, chromatin immunoprecipitation assays directed at mesodermal genes demonstrate that Geminin promotes Polycomb binding and Polycomb-mediated repressive histone modifications, while inhibiting modifications associated with gene activation. This work defines Geminin as an essential regulator of the embryonic transition from pluripotency through early multi-lineage commitment, and demonstrates that functional cooperativity between Geminin and Polycomb contributes to this process.

Snail2/Slug cooperates with Polycomb repressive complex 2 (PRC2) to regulate neural crest development

“…Disruption of PRC2 genes results in defects in mesendoderm differentiation in both mouse embryonic stem cells and in mouse embryos and leads to postimplantation lethality [reviewed by Vastenhouw and Schier (2012); Aloia et al (2013)]. Similarly, PRC2 is shown to regulate mesendodermal formation in Xenopus (Lim et al, 2011). Because of theses early phenotypes, the functions of PRC2 in late vertebrate development have not been studied in detail.…”

“…Previous studies have shown that PRC2 modulates mesendodermal formation in collaboration with the nuclear factor Geminin (Lim et al, 2011), but whether it also plays roles in neural and/or neural crest development is not clear. To address this issue, we performed targeted injection of PRC2 RNAs or translational blocking antisense morpholino oligos (MOs) specifically into the animal region of early Xenopus embryos.…”

“…RNAs were synthesized using a mMessage mMachine transcription kit (Ambion). Snail2-MO and SUZ12-MO were used as described (Zhang et al, 2006;Lim et al, 2011). EED-MO and EZH2-MO sequences were: 5′-AGCTTCCGACATGTTCCACCGCC-3′ and 5′-TTCCCCGTCTGGCCCATGATTATCC-3′, respectively.…”

Distinct activities of the anaphase-promoting complex/cyclosome (APC/C) in mouse embryonic cells

“…36 Geminin directly interacts with the chromatin remodeler Brg1, 37 an association that has clear implications for terminal differentiation. 9,38 By maintaining chromatin in an accessible hyperacetylated state, 39 the abundance of geminin Geminin is also present at high levels in both the nucleus and cytoplasm of malignant trophoblast cells of choriocarcinomas with enlarged nuclei. total DNa, blue.…”

Emerging Role of the Peroxisome Proliferator-Activated Receptors in Hepatocellular Carcinoma

“…Geminin was initially characterized as a nuclear protein that could regulate the expansion of the neural plate in early Xenopus embryos and inhibit DNA replication origin licensing [53,54]. It was recently revealed that Gemini is involved in restraining the mesodermal and endodermal lineage commitment in the early Xenopus embryo by recruiting the Polycomb-group protein Ezh2 is necessary [55]. However, during development of the ectoderm, Geminin promotes the neural fate acquisition of mouse ESCs by maintaining the chromatin of lineage-specific genes in an accessible and hyper acetylated state [56].…”