Figure 6.

Inducible expression of 7th mutant caldesmon stabilizes microfilaments during mitosis. Wild-type or mutant caldesmon was inducibly expressed before thymidine treatment and cells were fixed after 3 h of nocodazole treatment. Rounded cells were examined by staining with myc antibody (A, D, G, J, M, and P), rhodamine phalloidin (B, E, H, K, N, and Q), and DAPI (C, F, I, L, O, and R). Images were deconvolved using VayTek Microtome software. (A–C) Mock-transfection. Arrows indicate mitotic rounded cells. (D–I) Rounded cells expressing wild-type caldesmon (indicated by arrow). A mitotic rounded cell expressing wild-type caldesmon (D–F) showed a slightly higher cortex staining with phalloidin (E), whereas myc-staining (D) was diffuse. Nonmitotic rounded cells (arrow in G–I), on the other hand, exhibited actin bundles inside the cell or cortex that were stained both with myc antibody (G) and phalloidin (H). (J–R) Rounded cells expressing 7th mutant caldesmon. A mitotic cell (arrow in J–L) retained actin bundles that were stained both with myc antibody (J) and phalloidin (K). A nonmitotic rounded cell (indicated by arrow in M–O) showed stress fibers stained with both myc antibody and phalloidin. (P–R) Dumbbell-shaped mitotic cells expressing 7th mutant. Bar, 10 μm.