Figure 1.

Mechanisms by which the extracellular matrix (ECM) affects cell movements and both morphogen binding and diffusion. MMPs are important enzymes in remodeling the ECM for these various purposes. (A) Morphogens can bind to the extracellular matrix via proteins, such as glypican heparan sulfate proteoglycans (HSPGs) and cell receptors. (B) Areas of thick ECM restrict cell movement, whereas a thin ECM allows for tissue expansion necessary in processes like branching morphogenesis. (C) The ECM can modify morphogen diffusion rates by either facilitating or limiting morphogen diffusion through the ECM. Modified from References [17,19].