Affiliation:
1. Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON,Canada
2. Department of Molecular and Medical Genetics, University of Toronto, ON,Canada
Abstract
Signaling between tissues is essential to form the complex,three-dimensional organization of an embryo. Because many receptor tyrosine kinases signal through the RAS-MAPK pathway, phosphorylated ERK can be used as an indicator of when and where signaling is active during development. Using whole-mount immunohistochemistry with antibodies specific to phosphorylated ERK1 and ERK2, we analyzed the location, timing, distribution, duration and intensity of ERK signaling during mouse embryogenesis (5-10.5 days postcoitum). Spatial and temporal domains of ERK activation were discrete with well-defined boundaries, indicating specific regulation of signaling in vivo. Prominent, sustained domains of ERK activation were seen in the ectoplacental cone, extra-embryonic ectoderm, limb buds, branchial arches, frontonasal process, forebrain, midbrain-hindbrain boundary, tailbud, foregut and liver. Transient activation was seen in neural crest, peripheral nervous system,nascent blood vessels, and anlagen of the eye, ear and heart. In the contiguous domains of ERK signaling, phospho-ERK staining was cytoplasmic with no sign of nuclear translocation. With few exceptions, the strongest domains of ERK activation correlated with regions of known or suspected fibroblast growth factor (FGF) signaling, and brief incubation with an inhibitor of the fibroblast growth factor receptor (FGFR) specifically diminished the phospho-ERK staining in these regions. Although many domains of ERK activation were FGFR-dependent, not all domains of FGF signaling were phospho-ERK positive. These studies identify key domains of sustained ERK signaling in the intact mouse embryo, give significant insight into the regulation of this signaling in vivo and pinpoint regions where downstream target genes can be sought.
Publisher
The Company of Biologists
Subject
Developmental Biology,Molecular Biology
Reference63 articles.
1. Alsan, B. H. and Schultheiss, T. M. (2002). Regulation of avian cardiogenesis by Fgf8 signaling. Development129,1935-1943.
2. Belcheva, M. M. and Coscia, C. J. (2002). Diversity of G protein-coupled receptor signaling pathways to ERK/MAP kinase. Neurosignals11,34-44.
3. Camps, M., Chabert, C., Muda, M., Boschert, U., Gillieron, C. and Arkinstall, S. (1998). Induction of the mitogen-activated protein kinase phosphatase MKP3 by nerve growth factor in differentiating PC12. FEBS Lett.425,271-276.
4. Chambers, D., Medhurst, A. D., Walsh, F. S., Price, J. and Mason, I. (2000). Differential display of genes expressed at the midbrain - hindbrain junction identifies sprouty2: an FGF8-inducible member of a family of intracellular FGF antagonists. Mol. Cell Neurosci.15,22-35.
5. Christen, B. and Slack, J. M. (1999). Spatial response to fibroblast growth factor signalling in Xenopus embryos. Development126,119-125.