Upon treatment with blebbistatin, a potent inhibitor of myosin II, 3T3 fibroblasts start to develop a slender morphology that extends over much of the ring surface, suggesting that myosin II dependent contractile forces are responsible for maintaining a compact shape, similar to the constraint of liquid shape by surface tension (upper video, recording time, 480 min). Inhibition of Rho-dependent kinase, which activates myosin II, induces a similar effect (lower video, recording time, 210 min). |