Spatial response to fibroblast growth factor signalling in Xenopus embryos.
We have examined the spatial pattern of activation of the extracellular signal-regulated protein kinase (ERK) during Xenopus development, and show that it closely resembles the expression of various fibroblast growth factors (FGFs). Until the tailbud stage of development, all ERK activation domains are sensitive to the dominant negative FGF receptor, showing that activation is generated by endogenous FGF signalling. ERK is not activated by application of other growth factors like BMP4 or activin, nor is endogenous activation blocked by the respective dominant negative receptors. This shows that various domains of FGF expression, including the periblastoporal region and the midbrain-hindbrain boundary, are also sites of FGF signalling in vivo. Wounding induces a transient (<60 minutes) activation of ERK which is not significantly reduced by the dominant negative FGF receptor. An artificial FGF source, created by injection of eFGF mRNA into cleavage stage embryos, provokes ERK activation outside of its injection site over a range of several cell diameters. The range and extent of ERK activation outside the source region is unchanged by co-injection of a dominant negative form of Ras, which blocks ERK-activation within the source. This suggests that FGF protein can diffuse over several cell diameters.
Christen
B
B
Developmental Biology Programme, Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
Slack
J M
JM
D000199:Actins / Q000378:metabolism; D030301:Activin Receptors, Type II; D000818:Animals; D001755:Blastocyst / Q000378:metabolism; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D004789:Enzyme Activation; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000378:metabolism; D015398:Signal Transduction; D013194:Staining and Labeling / Q000379:methods; D014947:Wounds and Injuries / Q000378:metabolism; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology*; D015053:Zygote
D000199:Actins; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D017978:Receptors, Growth Factor; D029867:Xenopus Proteins; C525812:bmp4 protein, Xenopus; D005346:Fibroblast Growth Factors; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D030301:Activin Receptors, Type II