Picking up the threads: extracellular matrix signals in epithelial morphogenesis.

Basal adhesion signals are the main driver of epithelial polarization and differentiation. Recent advances are starting to expose a novel and remarkable complexity in extracellular matrix control of epithelial morphogenesis. Mechanical properties such as matrix stiffness and cell confinement are emerging as key regulators of epithelial behavior, modulating cytoskeletal dynamics, which transduce into nuclear signals that regulate differentiation. Moreover, coherent cell migration behaviors, such as organ rotation, control basement membrane secretion and reorganization, and matrix degradation and remodeling are now proposed to be required for proper polarity maintenance and acquisition of organ shape. Furthermore, planar cell polarity components orient all these activities, thus, providing a reasonable explanation for the generation of morphogenetic axes during morphogenesis.