Chambers, I. et al. Nanog safeguards pluripotency and mediates germline development. Nature 450, 1230-1234
MRC Centre Development in Stem Cell Biology, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh EH9 3JQ, UK. Nature
(Impact Factor: 41.46).
01/2008; 450(7173):1230-4. DOI: 10.1038/nature06403
Nanog is a divergent homeodomain protein found in mammalian pluripotent cells and developing germ cells. Deletion of Nanog causes early embryonic lethality, whereas constitutive expression enables autonomous self-renewal of embryonic stem cells. Nanog is accordingly considered a core element of the pluripotent transcriptional network. However, here we report that Nanog fluctuates in mouse embryonic stem cells. Transient downregulation of Nanog appears to predispose cells towards differentiation but does not mark commitment. By genetic deletion we show that, although they are prone to differentiate, embryonic stem cells can self-renew indefinitely in the permanent absence of Nanog. Expanded Nanog null cells colonize embryonic germ layers and exhibit multilineage differentiation both in fetal and adult chimaeras. Although they are also recruited to the germ line, primordial germ cells lacking Nanog fail to mature on reaching the genital ridge. This defect is rescued by repair of the mutant allele. Thus Nanog is dispensible for expression of somatic pluripotency but is specifically required for formation of germ cells. Nanog therefore acts primarily in construction of inner cell mass and germ cell states rather than in the housekeeping machinery of pluripotency. We surmise that Nanog stabilizes embryonic stem cells in culture by resisting or reversing alternative gene expression states.
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- "Additionally, cell fusion experiments demonstrate that Nanog promotes the formation of pluripotent hybrids as Nanog stimulates pluripotent gene activation in neural stem cells, thymocytes and fibroblasts in a dose-dependent manner (Silva et al., 2006). Knockout studies revealed that Nanog is dispensable for the housekeeping machinery of pluripotency since the conditional deletion of Nanog in ES cells does unexpectedly not result in loss of pluripotency (Chambers et al., 2007). During development in vivo, pluripotency is not established without Nanog and inner cell mass cells are trapped in an intermediate stage (Silva et al., 2009) assigning Nanog an Journal of Cell Science @BULLET Advance article essential role for the natural acquisition but not the maintenance of pluripotency (Pan and Thomson, 2007;Saunders et al., 2013). "
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ABSTRACT: A comprehensive analysis of the molecular network of cellular factors establishing and maintaining pluripotency as well as self renewal of pluripotent stem cells is key for further progress in understanding basic stem cell biology. Nanog is necessary for the natural induction of pluripotency in early mammalian development but dispensable for both, its maintenance as well as its artificial induction. To gain further insight into the molecular activity of Nanog we analyzed the gain-of-function of Nanog in various cell models employing a recently developed biologically active recombinant cell-permeant protein, Nanog-TAT. We found that Nanog enhances proliferation of both, NIH 3T3 as well as primary fibroblast cells. Nanog transduction into primary fibroblasts results in suppression of senescence‑associated β‑galactosidase activity. Investigation of cell cycle factors revealed that transient activation of Nanog correlates with consistent down-regulation of cell cycle inhibitor p27(KIP1). By chromatin immunoprecipitation analysis we confirmed bona fide Nanog binding sites upstream to the p27(KIP1) gene, establishing a direct link between physical occupancy and functional regulation. Our data demonstrates that Nanog enhances proliferation of fibroblasts via transcriptional regulation of cell cycle inhibitor p27 gene.
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- "Cellular heterogeneity has been accepted as a hallmark of both embryonic and adult stem cells (Graf and Stadtfeld, 2008;Chambers et al., 2007). It has been proposed that variation in gene expression arises from transcriptional noise and network fluctuation and that associated heterogeneity accounts for stochasticity of cell fate decisions in stem and progenitor cells (Chang et al., 2008). "
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ABSTRACT: Variation in gene expression is an important feature of mouse embryonic stem cells (ESCs). However, the mechanisms responsible for global gene expression variation in ESCs are not fully understood. We performed single-cell mRNA-seq analysis of mouse ESCs and uncovered significant heterogeneity in ESCs cultured in serum. We define highly variable gene clusters with distinct chromatin states and show that bivalent genes are prone to expression variation. At the same time, we identify an ESC-priming pathway that initiates the exit from the naive ESC state. Finally, we provide evidence that a large proportion of intracellular network variability is due to the extracellular culture environment. Serum-free culture reduces cellular heterogeneity and transcriptome variation in ESCs.
Available from: msb.embopress.org
- "The two miR-142 states are indistinguishable by pluripotency markers Previous reports of mESC heterogeneity found a metastable coexistence of a pluripotent state and a state prone to differentiate and already expressing lower levels of the pluripotency markers Nanog and Rex1 (Chambers et al, 2007; Singh et al, 2007; Toyooka et al, 2008; Singer et al, 2014). To test if miR-142 heterogeneity is upstream of expression changes in pluripotency markers, we analyzed FACS-purified " high " and " low " miR-142 mESC populations . "
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