Interaction of the IP3-Ca2+ and the FGF-MAPK signaling pathways in the Xenopus laevis embryo:: a qualitative approach to the mesodermal induction problem

In this work we propose that the animal-vegetal gradient spatial distribution of the IP3 receptors observed in the Xenopus embryo can effect a uniform FGF inducting input signal, allowing for different modes of transcription of the Xbra gene, producing the differentiation of the cells of the marginal zone. We analyze this hypothesis with a model for the interaction of the calcium signaling system with the MAPK cascade during the FGF mesodermal induction process, consisting of five non-linear coupled differential equations. A numerical treatment of a one- and two-cell system shows that the calcium flux between cells enhances the Raf activity levels, leading to oscillatory behavior. This qualitative result may be of consequence for the expression of the ventralizing characteristics of the FGF inducting signal. (C) 2002 Elsevier Science B.V. All rights reserved.