Fig. 6. Myosin II contributes to traction stresses under the tips of retracting pseudopodia in wild-type cells. (A,B) Fluorescence of GFP-ABD120k (left) and stress maps (right) under two typical pseudopodia from five migrating wild-type cells. Large traction stresses were observed under the tips of retracting pseudopodia where F-actin accumulated. (A',B') Time-courses of traction stresses (red lines) under the tips of each pseudopod (A,B) and pseudopod lengths (blue lines). (C-F) Fluorescence of GFP-ABD120k (left) and stress maps (right) under four typical pseudopodia from three migrating myosin-II-null cells. Large traction stresses were not observed under the tips of retracting pseudopodia where F-actin accumulated. (C'-F') The time-courses of pseudopod lengths and traction stresses just under the tip of each pseudopod. Blue and red lines indicate pseudopod lengths and stresses, respectively. Although a small rise in stress took place under the tip of a large pseudopod (arrow in F'), stresses under the pseudopod tips were unchanged typically between the elongation and retraction. (G) The average periods of elongation and retraction of pseudopodia in wild-type (n=5 in three cells) and myosin-II-null cells (n=7 in three cells). Although there was no significant difference in elongation time between wild-type and myosin-II-null cells, the retraction time of pseudopodia in wild-type cells was significantly shorter than in myosin-II-null cells. Bars, 1.5 µm. The look-up table (LUT) of A and B is indicated at the right side of B, and the LUT of C-F is at the right side of D.