Fig. 4. A schematic showing how local changes in ECM mechanics may guide tissue patterning. The local thinning in the ECM produced by accelerated ECM turnover will increase ECM compliance and result in local cell distortion through the action of tractional forces exerted by surrounding cells. Increased tension transfer across cell surface ECM receptors (integrins) will result in coordinated changes in cell and cytoskeletal form and, thereby, produce changes in cellular biochemistry that result in the localized growth and motility that drive tissue morphogenesis. Thus, in this view, cell growth and migration are constrained to the small group of cells (red) that is underlined by the thinned region of the basement membrane (green). Outward budding results when red cells extend and grow because neighboring cells along the same basement membrane do not experience the stress and, hence, remain quiescent (white cells).