Figure 2
Formation of the actin cap is induced more rapidly and at lower shear stresses than formation of basal actin.
(A). Schematic of an adherent cell subjected to flow of controlled shear stress for a controlled duration. Status of actin organization at the apical (green) and basal (purple) surface is examined by fluorescence microscopy. (B–K). Typical actin organization on top of the nucleus (B–F) and at the basal surface (G–K) before shear (0 min), after 1 or 30 min of low shear stress (0.05 dyn/cm2) and after 30 min of higher shear stress (5 dyn/cm2). White and yellow text corresponds to the percentage of cells with disrupted and organized actin, respectively, after shear. Insets show the whole cell, with inner boxes framing the zoomed regions shown in the main panels. (L) and (M). Fold increase in the number of cells showing organized actin caps (L) or basal actin (M) as a function of time for shear stresses of 0.05 dyn/cm2 (solid) and 5 dyn/cm2 (dashed), as compared to cells in no-shear conditions (0 min). Stars indicate statistically significant differences in the percentages of cells between the time of shear considered and the condition at time 0 using two-way ANOVA tests. (N). Percentage of cells with organized actin caps (green) or basal actin (purple) as a function of shear stress for a duration of shear that corresponded to a steady state of actin cap or basal actin organization. Stars indicate statistically significant differences for the level of shear stress considered and the previous lower value of shear stress, unless otherwise indicated, using a one-way ANOVA test. (O). Percentages of cells showing various combinations of basal actin and actin cap organization before shear (far left) and either after low shear stress (middle) or higher shear stress applications (far right). The remaining percentages exhibited both disrupted basal actin and disrupted apical actin caps. For all data shown, ***, **,* and ns indicate p value <0.001, <0.01, <0.05 and >0.05, respectively. α = 0.05 was used for all significance tests. Three independent experiments were conducted to quantify a total of 150 cells per condition.
