Mitogen-activated protein kinase (MAPK) cascades are evolutionary conserved 
transduction pathways involved in many cellular processes. Kinase modules are 
associated with scaffold proteins that regulate signaling by providing critical 
spatial and temporal specificities. Some of these scaffold proteins have been 
shown to be conserved, both in sequence and function. In mouse, the scaffold MP1 
(MEK Partner 1) forms a signaling complex with MEK1 and ERK1. In this work, we 
focus on Drosophila MP1 (dMP1). We show that dMP1 is expressed ubiquitously 
during embryonic and larval development. By in vitro and in vivo experiments, we 
show that dMP1 is located in the cytoplasm and the nuclei, and that it interacts 
with MEK and ERK. Genetic studies with transgenic Drosophila lines allowing 
either dMP1 over-expression or dMP1 down-regulation by RNA interference 
highlight dMP1 function in the control of cell differentiation during 
development of the Drosophila wing.