Negative feedback regulation of FGF signaling levels by Pyst1/MKP3 in chick embryos.
BACKGROUND
The importance of endogenous antagonists in intracellular signal transduction pathways is becoming increasingly recognized. There is evidence in cultured mammalian cells that Pyst1/MKP3, a dual specificity protein phosphatase, specifically binds to and inactivates ERK1/2 mitogen-activated protein kinases (MAPKs). High-level Pyst1/Mkp3 expression has recently been found at many sites of known FGF signaling in mouse embryos, but the significance of this association and its function are not known.


RESULTS
We have cloned chicken Pyst1/Mkp3 and show that high-level expression in neural plate correlates with active MAPK. We show that FGF signaling regulates Pyst1 expression in developing neural plate and limb bud by ablating and/or transplanting tissue sources of FGFs and by applying FGF protein or a specific FGFR inhibitor (SU5402). We further show by applying a specific MAP kinase kinase inhibitor (PD184352) that Pyst1 expression is regulated via the MAPK cascade. Overexpression of Pyst1 in chick embryos reduces levels of activated MAPK in neural plate and alters its morphology and retards limb bud outgrowth.


CONCLUSIONS
Pyst1 is an inducible antagonist of FGF signaling in embryos and acts in a negative feedback loop to regulate the activity of MAPK. Our results demonstrate both the importance of MAPK signaling in neural induction and limb bud outgrowth and the critical role played by dual specificity MAP kinase phosphatases in regulating developmental outcomes in vertebrates.
Eblaghie
Maxwell C
MC
Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dow Street, United Kingdom.
Lunn
J Simon
JS
Dickinson
Robin J
RJ
Münsterberg
Andrea E
AE
Sanz-Ezquerro
Juan Jose
JJ
Farrell
Elizabeth R
ER
Mathers
Joanne
J
Keyse
Stephen M
SM
Storey
Kate
K
Tickle
Cheryll
C
D000818:Animals; D015153:Blotting, Western; D002642:Chick Embryo; D017931:DNA Primers; D054642:Dual Specificity Phosphatase 6; D018274:Electroporation; D025461:Feedback, Physiological; D005346:Fibroblast Growth Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006493:Heparin; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D018878:Limb Buds; D020935:MAP Kinase Signaling System / Q000502:physiology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011758:Pyrroles / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
D017931:DNA Primers; D011758:Pyrroles; C105686:SU 5402; D005346:Fibroblast Growth Factors; D006493:Heparin; D020929:Mitogen-Activated Protein Kinase Kinases; D054642:Dual Specificity Phosphatase 6; C517036:Dusp6 protein, mouse; D017027:Protein Tyrosine Phosphatases