Chambers, I. et al. Nanog safeguards pluripotency and mediates germline development. Nature 450, 1230-1234
ABSTRACT 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.
[Show abstract] [Hide abstract]
- "As no second (attracting) stable state exists, cells rapidly return to their origin and, thus, exhibit pulsing Nanog dynamics (Fig. 3A, bottom). This model predicted that excursions from the NH state are transient, providing a very short window of opportunity in which perturbations can become consolidated into a lineage commitment decision (Chambers et al., 2007). "
ABSTRACT: The maintenance of pluripotency in embryonic stem cells (ESCs), its loss during lineage specification or its re-induction to generate induced pluripotent stem cells are central topics in stem cell biology. To uncover the molecular basis and the design principles of pluripotency control, a multitude of experimental, but also an increasing number of computational, studies have been published. Here, we consider recent reports that apply computational or mathematical modelling approaches to describe the regulatory processes that underlie cell fate decisions in mouse ESCs. We summarise the principles, the strengths and potentials but also the limitations of different computational strategies. © 2015. Published by The Company of Biologists Ltd.Development 07/2015; 142(13):2250-60. DOI:10.1242/dev.116343 · 6.27 Impact Factor
[Show abstract] [Hide abstract]
- "(Fig EV2, Table EV1). As expected, the transcription factors Rex1 and Nanog appeared variably expressed in the ESC-FCS population (Chambers et al, 2007; Toyooka et al, 2008), but not in the ESC-2i population, for which a more homogeneous signaling state is expected (Wray et al, 2010). In ESC-FCS, the extent of expression variability for several other development-related genes was even higher; examples included the body-axis specifying signaling molecule Lefty1 and the DNA methyltransferase regulator Dnmt3l. "
ABSTRACT: Cell-to-cell variability in gene expression is important for many processes in biology, including embryonic development and stem cell homeostasis. While heterogeneity of gene expression levels has been extensively studied, less attention has been paid to mRNA polyadenylation isoform choice. 3' untranslated regions regulate mRNA fate, and their choice is tightly controlled during development, but how 3' isoform usage varies within genetically and developmentally homogeneous cell populations has not been explored. Here, we perform genome-wide quantification of polyadenylation site usage in single mouse embryonic and neural stem cells using a novel single-cell transcriptomic method, BATSeq. By applying BATBayes, a statistical framework for analyzing single-cell isoform data, we find that while the developmental state of the cell globally determines isoform usage, single cells from the same state differ in the choice of isoforms. Notably this variation exceeds random selection with equal preference in all cells, a finding that was confirmed by RNA FISH data. Variability in 3' isoform choice has potential implications on functional cell-to-cell heterogeneity as well as utility in resolving cell populations. © 2015 The Authors. Published under the terms of the CC BY 4.0 license.Molecular Systems Biology 06/2015; 11(6). DOI:10.15252/msb.20156198 · 14.10 Impact Factor
[Show abstract] [Hide abstract]
- "Single-cell quantitative image analyses of immunostained Nanog:H2B-GFP Tg/+ ESCs maintained under different conditions further validated reporter efficacy (Figures 1B, S1E, and S1F). Moreover, we observed an increased correlation of reporter activity with NANOG protein for the Nanog:H2B- GFP transgene, compared to the targeted Nanog transcriptional reporter in the heterozygous TNGA ESCs (Chambers et al., 2007) (Figures S1E and S1F). These data suggest that the BAC transgenic reporters we constructed faithfully marked the pluripotent state in ESC cultures and could be used to probe Nanog expression dynamics at single-cell resolution. "
ABSTRACT: The pluripotent epiblast (EPI) is the founder tissue of almost all somatic cells. EPI and primitive endoderm (PrE) progenitors arise from the inner cell mass (ICM) of the blastocyst-stage embryo. The EPI lineage is distinctly identified by its expression of pluripotency-associated factors. Many of these factors have been reported to exhibit dynamic fluctuations of expression in embryonic stem cell cultures. Whether these fluctuations correlating with ICM fate choice occur in vivo remains an open question. Using single-cell resolution quantitative imaging of a Nanog transcriptional reporter, we noted an irreversible commitment to EPI/PrE lineages in vivo. A period of apoptosis occurred concomitantly with ICM cell-fate choice, followed by a burst of EPI-specific cell proliferation. Transitions were occasionally observed from PrE-to-EPI, but not vice versa, suggesting that they might be regulated and not stochastic. We propose that the rapid timescale of early mammalian embryonic development prevents fluctuations in cell fate. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.Cell Reports 03/2015; 10(9). DOI:10.1016/j.celrep.2015.02.010 · 8.36 Impact Factor