Spatial regulation of BMP signaling by patterned receptor expression.

Local delivery of TGF-beta/BMP ligands is commonly used as a tissue engineering strategy for the spatial regulation of cell growth and differentiation. While the location and the dose of ligand are the only parameters that influence the spatial distribution and biological effects of the ligand in vitro, in vivo genetic studies of development reveal that spatial control of TGF-beta/BMP signaling can be accomplished at multiple levels, from ligand release to signal interpretation. Here we focus on spatial control of BMP signaling by patterned receptor expression. Motivated by our recent experimental analysis of the two-dimensional BMP signaling patterns in the developing Drosophila egg, we formulate one- and two-dimensional models of ligand diffusion and internalization in the presence of patterned receptor expression. Our analysis of these models shows that they can capture the quantitative features of the experimentally observed pattern of phosphorylated SMAD in Drosophila oogenesis and shows that patterned receptor expression provides versatile control of BMP signaling in developing tissues. Quantitative understanding of the mechanisms of spatiotemporal control of signaling pathways in development is essential for successful harnessing of these pathways in tissue engineering.