title: Control of the segmentation process by graded MAPK/ERK activation in the chick embryo.
abstract: The regular spacing of somites during vertebrate embryogenesis involves a dynamic gradient of FGF signaling that controls the timing of maturation of cells in the presomitic mesoderm (PSM). How the FGF signal is transduced by PSM cells is unclear. Here, we first show that the FGF gradient is translated into graded activation of the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway along the PSM in the chicken embryo. Using in ovo electroporation of PSM cells, we demonstrate that constitutive activation of ERK signaling in the PSM blocks segmentation by preventing maturation of PSM cells, thus phenocopying the overexpression of FGF8. Conversely, inhibition of ERK phosphorylation mimics a loss of function of FGF signaling in the PSM. Interestingly, video microscopy analysis of cell movements shows that ERK regulates the motility of PSM cells, suggesting that the decrease of cell movements along the PSM enables mesenchymal PSM cells to undergo proper segmentation. Together, our data demonstrate that ERK is the effector of the gradient of FGF in the PSM that controls the segmentation process.
authors.affiliation: Stowers Institute for Medical Research, 1000 East 50th Street, Kansas City, MO 64110, USA.
authors.forename: Marie-Claire
authors.initials: MC
authors.lastname: Delfini
authors.forename: Julien
authors.initials: J
authors.lastname: Dubrulle
authors.forename: Pascale
authors.initials: P
authors.lastname: Malapert
authors.forename: Jérome
authors.initials: J
authors.lastname: Chal
authors.forename: Olivier
authors.initials: O
authors.lastname: Pourquié
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002465:Cell Movement / Q000502:physiology; D002642:Chick Embryo; D018274:Electroporation; D047108:Embryonic Development / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism* / Q000502:physiology; D005346:Fibroblast Growth Factors / Q000378:metabolism* / Q000502:physiology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008648:Mesoderm / Q000502:physiology*; D018715:Microscopy, Video; D008863:Microspheres; D010766:Phosphorylation; D015398:Signal Transduction / Q000502:physiology*; D019170:Somites / Q000378:metabolism* / Q000502:physiology
chemical_list: D005346:Fibroblast Growth Factors; D048049:Extracellular Signal-Regulated MAP Kinases