Characterisation of the Fibroblast Growth Factor Dependent Transcriptome in Early Development

Peter A Branney,Mary Elizabeth Pownall,Harry V Isaacs,Laura Faas,Sarah E Steane,Bernadette Breant

doi:10.1371/journal.pone.0004951

Abstract

BackgroundFGF signaling has multiple roles in regulating processes in animal development, including the specification and patterning of the mesoderm. In addition, FGF signaling supports self renewal of human embryonic stem cells and is required for differentiation of murine embryonic stem cells into a number of lineages.Methodology/Principal FindingsGiven the importance of FGF signaling in regulating development and stem cell behaviour, we aimed to identify the transcriptional targets of FGF signalling during early development in the vertebrate model Xenopus laevis. We analysed the effects on gene expression in embryos in which FGF signaling was inhibited by dominant negative FGF receptors. 67 genes positively regulated by FGF signaling and 16 genes negatively regulated by FGF signaling were identified. FGF target genes are expressed in distinct waves during the late blastula to early gastrula phase. Many of these genes are expressed in the early mesoderm and dorsal ectoderm. A widespread requirement for FGF in regulating genes expressed in the Spemann organizer is revealed. The FGF targets MKP1 and DUSP5 are shown to be negative regulators of FGF signaling in early Xenopus tissues. FoxD3 and Lin28, which are involved in regulating pluripotency in ES cells are shown to be down regulated when FGF signaling is blocked.ConclusionsWe have undertaken a detailed analysis of FGF target genes which has generated a robust, well validated data set. We have found a widespread role for FGF signaling in regulating the expression of genes mediating the function of the Spemann organizer. In addition, we have found that the FGF targets MKP1 and DUSP5 are likely to contribute to the complex feedback loops involved in modulating responses to FGF signaling. We also find a link between FGF signaling and the expression of known regulators of pluripotency.

Highlights

Fibroblast growth factors (FGFs) are small polypeptides that have multiple functions in early development and homeostasis of the adult organism
We have found a widespread role for FGF signaling in regulating the expression of genes mediating the function of the Spemann organizer
We have found that the FGF targets MAP kinase phosphatase 1 (MKP1) and Dual Specificity Phosphatase 5 (DUSP5) are likely to contribute to the complex feedback loops involved in modulating responses to FGF signaling

Summary

Introduction

Fibroblast growth factors (FGFs) are small polypeptides that have multiple functions in early development and homeostasis of the adult organism. FGFs are present in all animal groups and are one of relatively few families of extracellular signaling molecules that are involved in regulating animal development. FGF signaling has a key role in specifying the primary germ layers that give rise to all the tissues of the adult organism. Experiments initially carried out in amphibians, and later supported by studies in mammals, birds and fish, demonstrated that FGF signaling is required to regulate gene expression within the early vertebrate mesoderm, which is the germ layer giving rise to muscle, skeleton, connective tissue, blood and organs such as the kidney [2,3,4,5,6]. FGF signaling has multiple roles in regulating processes in animal development, including the specification and patterning of the mesoderm. FGF signaling supports self renewal of human embryonic stem cells and is required for differentiation of murine embryonic stem cells into a number of lineages

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