Extracellular matrix and growth factors in branching morphogenesis. 
The unifying hypothesis of the NSCORT in gravitational biology postulates that the ECM and growth factors are key interrelated components of a macromolecular regulatory system.  The ECM is known to be important in growth and branching morphogenesis of embryonic organs.  Growth factors have been detected in the developing embryo, and often the pattern of localization is associated with areas undergoing epithelial-mesenchymal interactions.  Causal relationships between these components may be of fundamental importance in control of branching morphogenesis.