  Development in multi-cellular organisms is marked by a high degree of spatial
organization of the cells attaining distinct fates in the embryo. We show that
receptor-ligand interaction between cells in close physical proximity
adaptively regulates the local process of selective gene expression in the
presence of a global field set up by a diffusing morphogen that provides
positional cues. This allows information from the cellular neighborhood to be
incorporated into the emergent thresholds of morphogen concentration that
dictate cell fate, consistent with recent experiments.
