An amorphous cluster of actin filaments revolves along the cell cortex. (A) Time-lapse images of HeLa cells expressing GFP-UtrCH and DsRed-histone H1 during metaphase. GFP-UtrCH images were taken every 5 s, and images are shown at 30-s intervals. (B) Staining with anti-actin antibody (left) or Alexa Fluor 546–phalloidin (right) of HeLa cells expressing GFP-UtrCH. (C) Staining with anti-actin antibody (left) or Alexa Fluor 546–phalloidin (right) of HeLa cells. Arrowheads indicate an amorphous cluster of actin filaments. (D) Direction of the revolving movement of the amorphous actin cluster (n = 146). (E) Spatiotemporal representation of the revolving movement of the amorphous actin cluster of A. Intensities of GFP-UtrCH signals in areas between the 0.70–0.75 radius away from the center of the cell were averaged and plotted. (F) Fourier transformation of E. (G) Histogram of the period of the revolving movement of the cluster (n = 57). (H) Relationship between the radius of cells and the period of the revolving movement of the actin cluster (n = 57). Bars: (A) 10 µm; (B and C) 5 µm.