IN-SITU ACTIVATION PATTERN OF DROSOPHILA EGF RECEPTOR PATHWAY DURING DEVELOPMENT

Signaling cascades triggered by receptor tyrosine kinases (RTKs) parti cipate in diverse developmental processes. The active state of these s ignaling pathways was monitored by examination of the in situ distribu tion of the active, dual phosphorylated form of mitogen-activated prot ein kinase (ERK) with a specific monoclonal antibody. Detection of the active state of the Drosophila epidermal growth factor receptor (DER) pathway allowed the visualization of gradients and boundaries of rece ptor activation, assessment of the distribution of activating ligands, and analysis of interplay with the inhibitory ligand Argos. This in s itu approach can be used to monitor other receptor-triggered pathways in a wide range of organisms.