Fig. 6. A proposed model for the effects of high-curvature cell shape regions on FA-actin organization, nuclear deformability, and lineage commitment of MSCs.

MSCs plated on circular and square micropatterns form circular cells (71) and square cells (2), respectively. FAs sense substrate topography, which in turn changes the protein composition of the FAs and guide the orientation of the radial fibers. The radial fibers are bound to the ends of the transverse fibers, which predominantly contain myosin-II motor proteins to generate contractile forces. In circular (3) and square cells (4), actomyosin contractility causes a centripetal motion of the transverse fibers, which pull the radial fibers and transmit the forces to the FAs; this creates a global centripetal flow within the actin system. The radial configuration of the actin system in circular (5) and square cells (6) brings about nuclear deformation in the latter case and this regulates YAP nuclear translocation, which in turn dictates MSC lineage commitment.