Nutt et al (2001a)

Xenopus Sprouty2 inhibits FGF mediated gastrulation movements but does not affect mesoderm induction and patterning

S.L. Nutt, K.S. Dingwell, C. E. Holt and E. Amaya

Genes and Development. 15:1152-1166 (2001). Full Article (824K)

Abstract

Signal transduction through the FGF receptor is essential for the specification of the vertebrate body plan.

Blocking the FGF pathway in early Xenopus embryos inhibits mesoderm induction and results in

truncation of the anterior-posterior axis. The Drosophila gene sprouty encodes an antagonist of FGF

signalling, which is transcriptionally induced by the pathway, but whose molecular functions are poorly

characterised. We have cloned Xenopus sprouty2 and show that it is expressed in a similar pattern to

known FGFs and is dependent on the FGF/Ras/MAPK pathway for its expression. Over-expression of

Xsprouty2 in both embryos and explant assays results in the inhibition of the cell movements of

convergent extension. While blocking FGF/Ras/MAPK signalling leads to an inhibition of mesodermal

gene expression, these markers are unaffected by Xsprouty2, indicating that mesoderm induction and

patterning occurs normally in these embryos. Finally using Xenopus oocytes we show that Xsprouty2 is

an intracellular antagonist of FGF-dependent calcium signalling. These results provide evidence for at

least two distinct FGF-dependent signal transduction pathways: a Sprouty insensitive Ras/MAPK

pathway required for the transcription of most mesodermal genes, and a Sprouty sensitive pathway

required for co-ordination of cellular morphogenesis.