The developmental dismantling of pluripotency is reversed by ectopic Oct4 expression

Abstract

SUMMARYThe transcription factors Nanog and Oct4 regulate pluripotency in the pre-implantation epiblast and in derivative embryonic stem cells. During post-implantation development, the precise timing and mechanism of the loss of pluripotency is unknown. Here, we show that in the mouse, pluripotency is extinguished at the onset of somitogenesis, coincident with reduced expression and chromatin accessibility of Oct4 and Nanog regulatory regions. Prior to somitogenesis expression of both Nanog and Oct4 is regionalized. We show that pluripotency tracks the in vivo level of Oct4 and not Nanog by assessing the ability to reactivate or maintain Nanog expression in cell culture. Enforced Oct4 expression in somitogenesis-stage tissue provokes rapid reopening of Oct4 and Nanog chromatin, Nanog re-expression and resuscitates moribund pluripotency. Our data suggest that decreasing Oct4 expression is converted to a sudden drop in competence to maintain pluripotency gene regulatory network activity that is subsequently stabilized by epigenetic locks.

From blastocyst to gastrula: gene regulatory networks of embryonic stem cells and early mouse embryogenesis

“…Somewhat paradoxically, Oct4 expression persists throughout the Epi until its elimination during somitogenesis, though this elimination begins in the anterior Epi [124]. However, this observation is concordant with the findings that Wnt/b-catenin-mediated primitive rstb.royalsocietypublishing.org Phil.…”

“…Central members of the core pluripotency circuitry, including Oct4, Sox2 and Nanog, appear to be among the common components, while regionalized changes in the balance of the circuit result in activation and repression of their respective targets. Such changes are mediated in part by a gradual extinction of their expression as the accessibility of their cisregulatory elements is decreased by nucleosome invasion [124], which alters the effect of peripheral components such as Tcf3 and Tbx3 on this circuitry, and initiates their switch to roles as lineage-specifying genes. At present, it is unclear how region-specific changes initiate this process, but alterations in cell contacts, signalling and morphogenetic events are likely to be significant.…”

Esrrb extinction triggers dismantling of naïve pluripotency and marks commitment to differentiation

“…The period of loss of NANOG expression occurring at peri‐implantation (Chambers et al , 2003; Acampora et al , 2013) may enable cells of the epiblast to downregulate a number of pivotal naïve pluripotency determinants, including ESRRB (Adachi et al , 2013). In the post‐implantation epiblast, NANOG is re‐expressed (Hart et al , 2004; Osorno et al , 2012; Hoffman et al , 2013) but ESRRB is not (Adachi et al , 2013), likely due to differences in signaling environments between pre‐ and post‐implantation epiblasts. It is noteworthy that subpopulations of ESC cultures have been proposed to bear a similar character to primed pluripotent cells and vice versa (Hayashi et al , 2008; Han et al , 2010).…”

Smad2 Is Essential for Maintenance of the Human and Mouse Primed Pluripotent Stem Cell State

“…Suppression of BMP-induced Differentiation by Smad2-While promoting pluripotency in mouse and human ES cells, Nanog was shown to be dispensable for maintaining EpiSC pluripotency (21). We thus surmised that Smad2 might have additional critical roles in maintaining pluripotency.…”

“…Accordingly, elevated Nanog expression in mESCs results in clonal expansion and resistance to differentiation (16) and, in hESCs, promotes cell proliferation (17). However, Nanog expression is heterogeneous in ESC colonies (18,19) and the inner cell mass of the mouse blastocyst (20) and was shown to be dispensable for mEpiSC pluripotency (21), suggesting more prominent roles of Oct4 and Sox2 in primed pluripotency.…”