Wnt Signaling Mediates Self-Organization and Axis Formation in Embryoid Bodies

Abstract

Summary Embryonic stem cells form descendants of all three germ layers when differentiated as aggregates, termed embryoid bodies. In vivo, differentiation of cells depends on signals and morphogen gradients that provide instructive and positional cues, but do such gradients exist in embryoid bodies? We report here the establishment of anteroposterior polarity and the formation of a primitive streak-like region in the embryoid body, dependent on local activation of the Wnt pathway. In this region, cells undergo an epithelial-to-mesenchymal transition and differentiate into mesendodermal progenitors. Exogenous Wnt3a protein posteriorizes the embryoid body, resulting in predominantly mesendodermal differentiation. Conversely, inhibiting Wnt signaling promotes anterior character and results in neurectodermal differentiation. The activation of Wnt signaling and primitive streak formation requires external signals but is self-reinforcing after initiation. Our findings show that the Wnt pathway mediates the local execution of a gastrulation-like process in the embryoid body, which displays an unexpected degree of self-organization.

Wnt Pathway Regulation of Embryonic Stem Cell Self-Renewal

“…1) (Brons et al 2007;Tesar et al 2007). Instead of stimulating self-renewal, Wnt signaling effectively stimulated differentiation of mESCs after they have been primed either by growth at a high density (Otero et al 2004) or by initial commitment in EB assays (Lindsley et al 2006;ten Berge et al 2008). Similar to hESCs, EpiSCs responded to inhibiting GSK3 by differentiating .…”

Wnt5a uses CD146 as a receptor to regulate cell motility and convergent extension

“…We have previously reported that CD146 induces the epithelial-mesenchymal transition by downregulating the expression of E-cadherin in breast cancer cell lines 16 . E-cadherin, an adhesion molecule anchoring b-catenin to the cell membrane, has been identified as a canonical Wnt target gene and is positively regulated by Wnt 41,42 . In this study, we demonstrate that CD146 is the negative regulator of canonical Wnt signalling.…”

A Functional Assay for Putative Mouse and Human Definitive Endoderm using Chick Whole-Embryo Cultures

“…Wnt3a is added to the human cells in order to accelerate transition through the PS [21,40] but not to the mESCs. The activation of Wnt signaling and induction of PS formation requires external signals but is self-reinforcing after initiation [40].…”

“…Wnt3a is added to the human cells in order to accelerate transition through the PS [21,40] but not to the mESCs. The activation of Wnt signaling and induction of PS formation requires external signals but is self-reinforcing after initiation [40]. Wnt3a is coexpressed with Brachyury, which is a direct target of Wnt3a signaling [41] in the PS during gastrulation [42,43].…”