E-cadherin is required for the proper activation of the Lifr/Gp130 signaling pathway in mouse embryonic stem cells

Abstract

SUMMARYThe leukemia inhibitory factor (Lif) signaling pathway is a crucial determinant for mouse embryonic stem (mES) cell self-renewal and pluripotency. One of the hallmarks of mES cells, their compact growth morphology, results from tight cell adhesion mediated through E-cadherin, β-catenin (Ctnnb1) and α-catenin with the actin cytoskeleton. β-catenin is also involved in canonical Wnt signaling, which has also been suggested to control mES cell stemness. Here, we analyze Ctnnb1 −/− mES cells in which cell adhesion is preserved by anEα mES cells), and show that mimicking only the adhesive function of β-catenin is necessary and sufficient to maintain the mES cell state, making β-catenin/Wnt signaling obsolete in this process. Furthermore, we propose a role for E-cadherin in promoting the Lif signaling cascade, showing an association of E-cadherin with the Lifr-Gp130 receptor complex, which is most likely facilitated by the extracellular domain of E-cadherin. Without Eα, and thus without maintained cell adhesion, Ctnnb1 −/− mES cells downregulate components of the Lif signaling pathway, such as Lifr, Gp130 and activated Stat3, as well as pluripotency-associated markers. From these observations, we hypothesize that the changes in gene expression accompanying the loss of pluripotency are a direct consequence of dysfunctional cell adhesion. Supporting this view, we find that the requirement for intact adhesion can be circumvented by the forced expression of constitutively active Stat3. In summary, we put forward a model in which mES cells can be propagated in culture in the absence of Ctnnb1, as long as E-cadherin-mediated cell adhesion is preserved.

Porcn-dependent Wnt signaling is not required prior to mouse gastrulation

“…Consistent with other recent studies (del Valle et al, 2013;Faunes et al, 2013;Rudloff and Kemler, 2012), however, our data do not preclude a non-transcriptional role for β-catenin in the maintenance of pluripotency in vitro.…”

“…Zygotic deletion of Porcn has been reported but not investigated in detail . Porcn functions in the preimplantation embryo are of particular interest, as canonical Wnt signaling and β-catenin have been implicated in the maintenance of pluripotent mouse embryonic stem cells (ESCs) (ten Berge et al, 2011;del Valle et al, 2013;Faunes et al, 2013;Habib et al, 2013), which are derived from the inner cell mass (ICM) of the mouse blastocyst.…”

Role of cell–cell adhesion complexes in embryonic stem cell biology

“…1). In ICMderived mESCs, loss of E-cadherin function due to inhibition using extracellular peptides, RNA interference or gene ablation abrogates the compact growth morphology of mESCs (del Valle et al, 2013;Larue et al, 1994;Soncin et al, 2009) (Fig. 3A).…”

“…stemness. This was addressed by using Cdh1 2/2 or b-catenin knockout (Ctnnb1 2/2 ) mESCs (del Valle et al, 2013;Hawkins et al, 2012;Soncin et al, 2011). The results indicate that complex mechanisms exist, with different genotypes of the mESCs becoming dependent on different growth factors that influence their stemness.…”

“…Constitutive activation of STAT3 in mESCs is sufficient to keep cells undifferentiated when LIF is absent (Matsuda et al, 1999). Cdh1 2/2 mESCs fail to respond to LIF signaling (del Valle et al, 2013;Soncin et al, 2009;Soncin et al, 2011) and STAT3 is not activated (del Valle et al, 2013;Hawkins et al, 2012). Nonetheless, Cdh1 2/2 mESCs sustain selfrenewal in the absence of LIF (Soncin et al, 2009;Soncin et al, 2011).…”