Loss of CIP4 reduces cortical tension in CHRF cells. (A) Photomicrograph of micropipette aspiration of a CHRF-288-11 cell. The pressure in buffer (P₀), the suction pressure inside the pipette (P_p), the inner radius of the pipette (R_p), the radius of the spherical portion of the cell outside the pipette (R_c), and the length of the cell tongue aspirated inside the pipette (L_p) are indicated. Aspiration could cause polarization of cytoplasmic contents. The image shows the condensed region stays away from the pipette orifice where a transparent region is formed nearby. (B) Decreased cortical tension in CHRF cells after reduced levels of CIP4 or WASP either at baseline or after treatment with either PMA or fibronectin. **P ≤ .01; ***P ≤ .001. (C-D) Representative images of micropipette aspiration of an untreated cell without (C) with (D) CIP4 knockdown. Without CIP4 knockdown, the transparent region was aspirated furthest into the pipette and blebbing was rare. With CIP4 knockdown, cell swelling was observed under the isotonic condition. Repeated blebbing was observed in the inner transparent region inside the pipette. (E-F) Blebbing of CHRF cells. (E) Initiation of membrane blebbing. The near-orifice transparent region was pinched off and transformed into a bubble-like protrusion. The dynamic process was driven by the sucking pressure. (F) Repeated blebbing. The protruded bleb was snitched out, followed by a newly-extruded immature bleb. (Magnification 40×; bar represents 5 um). Images were obtained with an inverted microscope with 40× dry lens (Nikon TiE, Nikon, Tokyo, Japan) through a camera (GC1290, Prosilica, Allied Vision Technologies, Augusta Technologie, Munich, Germany) that has a standard video rate (30 frames per second). The acquisition program was home-made.