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.
"In vitro, it has repeatedly been observed that mESCs are heterogeneous for expression of Nanog (Chambers et al., 2007). Although mPSCs can flux between Nanog + and Nanog – states in vitro, this is not reflected in the embryo in vivo, where, once epiblast cells become specified, they no longer move backwards in developmental time to give rise to primitive endoderm (Xenopoulos et al., 2015). "
[Show abstract][Hide abstract] ABSTRACT: In the mouse, naïve pluripotent stem cells (PSCs) are thought to represent the cell culture equivalent of the late epiblast in the pre-implantation embryo, with which they share a unique defining set of features. Recent studies have focused on the identification and propagation of a similar cell state in human. Although the capture of an exact human equivalent of the mouse naïve PSC remains an elusive goal, comparative studies spurred on by this quest are lighting the path to a deeper understanding of pluripotent state regulation in early mammalian development.
Development 09/2015; 142:30910-3099. DOI:10.1242/dev.116061 · 6.46 Impact Factor
"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). "
"(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. "
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