FGF signalling modulates transcriptional repression by Xenopus groucho‐related‐4

Abstract

Background information . Developmental cell signals co‐operate in the processes of cell specification and tissue patterning during embryogenesis. Interactions between the FGF (fibroblast growth factor) and Wnt signalling pathways have been demonstrated in a number of developmental processes, including mesoderm formation in amphibian embryos. However, the mechanism underlying the interactions between these key signalling pathways remains unclear. Results . In the present study, we find that the ability of TLE4/Xgrg4 (transducin‐like enhancer of split 4/ Xenopus groucho‐related gene 4) to inhibit a transcriptional target of canonical Wnt signalling is reduced in the presence of FGF and that this is partially dependent on a consensus site for MAPK (mitogen‐activated protein kinase) phosphorylation in TLE4/Xgrg4. Conclusions . These data suggest to us a novel molecular mechanism where FGF and Wnt signalling pathways interact at the level of the co‐repressor TLE4/Xgrg4: the weakening of TLE4/Xgrg4 repression by FGF signalling, combined with the stabilization of β‐catenin by Wnt signals, enhances expression of Wnt target genes.