A genetic strategy for the dynamic and graded control of cell mechanics, motility, and matrix remodeling.

Cellular mechanical properties have emerged as central regulators of many critical cell behaviors, including proliferation, motility, and differentiation. Although investigators have developed numerous techniques to influence these properties indirectly by engineering the extracellular matrix (ECM), relatively few tools are available to directly engineer the cells themselves. Here we present a genetic strategy for obtaining graded, dynamic control over cellular mechanical properties by regulating the expression of mutant mechanotransductive proteins from a single copy of a gene placed under a repressible promoter. With the use of constitutively active mutants of RhoA GTPase and myosin light chain kinase, we show that varying the expression level of either protein produces graded changes in stress fiber assembly, traction force generation, cellular stiffness, and migration speed. Using this approach, we demonstrate that soft ECMs render cells maximally sensitive to changes in RhoA activity, and that by modulating the ability of cells to engage and contract soft ECMs, we can dynamically control cell spreading, migration, and matrix remodeling. Thus, in addition to providing quantitative relationships between mechanotransductive signaling, cellular mechanical properties, and dynamic cell behaviors, this strategy enables us to control the physical interactions between cells and the ECM and thereby dictate how cells respond to matrix properties.