Fig. 3. Formation of peripheral protrusions is mediated by actin polymerization and is not caused by stabilization of cortical F-actin. (A) Preformed Caco-2 cysts were treated for 12 hours with either blebbistatin alone (100 µM) or with a combination of blebbistatin and latrunculin B (1 µM) to inhibit actin polymerization. Inhibition of actin polymerization prevented the formation of peripheral protrusions in blebbistatin-treated Caco-2 cysts (^*P<0.001). (B) Preformed Caco-2 cysts were treated for 12 hours with either vehicle, a cortical flow inhibitor (WGA; 500 µg/ml) or an F-actin-stabilizing drug (jasplakinolide; 0.5 µM). The formation of protrusions on the cyst surface was not induced by any treatment.