Demonstration of the physical integration of microtubule and actin cytoskeletons. (a) Experimental design. A localized force was generated in the actin meshwork a short distance from a microtubule. The force was expected to induce a deformation of the nearby microtubule by propagating through the actin meshwork. (b) Snapshots of microtubule (green), actin (magenta), and a phalloidin-coated magnetic bead (cyan) before and during the force application. Arrowhead indicates the analyzed microtubule. Scale bar is 2 μm. (c) Local displacement field of actin meshwork. The black arrow and color indicate the vector and amplitude of the displacements, respectively. Scales are 0.2 μm (arrow, for the displacement vector) and 10 μm (bar, for confocal image). Right: An enlarged plot highlighting the position of the bead and the direction of the force (white circle and arrow). Scales are 0.2 μm (arrow, for the displacement vector) and 2 μm (bar, for confocal image). (d) Time evolution of the microtubule shape (solid lines) and the bead position (dots). The black circle indicates the outline of the bead at the initial frame. Time is color coded. (e) The displacement of actin meshwork (magenta) along the direction of the force is plotted as a function of the distance from the load position. Green circle indicates the displacement of the microtubule. Shaded area and error bar indicate the standard deviation. (f and g) Statistics. (f) Remote force-induced deformation of single microtubules. The deformation was defined as the local displacement of microtubules during the force application. Solid black line indicates the mean and the standard deviation. (g) The maximum displacement of microtubules is plotted as a function of the displacement of actin meshwork at the same position. n = 20 measurements from 19 cells.