Fibroblast Growth Factor Signaling and Basement Membrane Assembly Are Connected during Epithelial Morphogenesis of the Embryoid Body

Abstract

Fibroblast growth factors and receptors are intimately connected to the extracellular matrix by their affinity to heparan sulfate proteoglycans. They mediate multiple processes during embryonic development and adult life. In this study, embryonic stem cell–derived embryoid bodies were used to model fibroblast growth factor signaling during early epithelial morphogenesis. To avoid redundancy caused by multiple receptors, we employed a dominant negative mutation of Fgfr2. Mutant-derived embryoid bodies failed to form endoderm, ectoderm, and basement membrane and did not cavitate. However, in mixed cultures they displayed complete differentiation induced by extracellular products of the normal cell. Evidence will be presented here that at least one of these products is the basement membrane or factors connected to it. It will be shown that in the mutant, collagen IV and laminin-1 synthesis is coordinately suppressed. We will demonstrate that the basement membrane is required for embryoid body differentiation by rescuing columnar ectoderm differentiation and cavitation in the mutant by externally added basement membrane proteins. This treatment induced transcription of Eomesodermin, an early developmental gene, suggesting that purified basement membrane proteins can activate inherent developmental programs. Our results provide a new paradigm for the role of fibroblast growth factor signaling in basement membrane formation and epithelial differentiation.

RETRACTED: Contribution of the PI3K/Akt/PKB signal pathway to maintenance of self‐renewal in human embryonic stem cells

“…Cumulative evidence on mESCs consistently revealed that the interaction between FGFs and their receptors led to the upregulation of ECM molecules through the activation of PI3K/Akt/PKB [27,28], and that this promoted basement …”

Cell and molecular regulation of the mouse blastocyst

“…Mice lacking either Fgf4 or Fgf receptor2 (Fgfr2) do not form PE in vivo or in vitro (Feldman et al, 1995;Wilder et al, 1997;Arman et al, 1998). Overexpression of a dominant-negative form of the Fgf receptor prevents formation of PE in vitro in embryoid bodies (Li et al, 2001). Importantly, this phenotype can be rescued by overexpression of Gata6 and Gata4 (Li et al, 2004).…”

The topographical regulation of embryonic stem cell differentiation

“…Clearly, the surface cells are unique in having a free surface that is not involved in the E-cadherin-dependent adhesion responsible for the clustering of ES cells into developing embryoid bodies (Larue et al 1996). It has been reported that E-cadherin-mediated cell adhesion can stimulate phosphorylation of the docking protein Gab-1 involved in activation of Ras/MAPK and PI3-kinase/Akt cascades (Shinohara et al 2001), both of which have been implicated in endodermal cell differentiation (Cheng et al 1998;Li et al 2001). Thus, the surface location of ES cells may regulate the function of the FGF-dependent signalling pathways, shown above to be necessary for endodermal cell differentiation.…”

“…While the proliferation of FGF-4Ϫ/Ϫ ES cells is apparently normal (Rappolee et al 1994;Wilder et al 1997), ablation of the FGF4 gene demonstrated that it is necessary for the development of extraembryonic endoderm in vivo. Analysis of FGF signalling after blockade with dominantnegative FGF receptor constructs has provided evidence that the phosphoinositide 3Ј-kinase (PI3-kinase) and Akt/protein kinase B pathway downstream of the FGF receptor is necessary for endodermal cell differentiation (C. S. Li et al 2001). Additionally, it has been demonstrated that Grb-2, acting upstream of the Ras-MAPK pathway is required for the appearance of endodermal cells (Cheng et al 1998).…”