Long Range Dpp Gradient Formation
Decapentaplegic (Dpp) is a key morphogen which is expressed in a stripe of cells along the anteriorposterior (A-P) boundary of the Drosophila wing imaginal discs and diffuses along the A-P axis forming, at steady-state, a "quasi exponential" profile. The mechanisms by which this profile is formed has however long been controversal and two distinct mechanisms involving Dpp receptors have been proposed: Receptor-Mediated Transcytosis (RMT) and Restricted Extracellular Diffusion (RED).
In a recent paper (for more details click here), we developed a rigorous theoretical model which involves three Dpp components: extracellular Dpp, receptor-bound Dpp and internalized Dpp. Providing a different parameter choice, this model allows to describe both the RMT and RED mechanism. Comparing our analytical model to wild-type and receptor mutant clone experimental data, we conclude that (1) the RMT mechanism is not consistent with our experimental data (2) a RED mechanism where most of the Dpp is unbound to the receptor leads to the expected Dpp profiles.