Fig. 6. Dividing cells attach to the substratum at MiDAS regions. A representative dividing multinucleated HS1 cell simultaneously observed by fluorescence microscopy and interference reflection microscopy (IRM). Left panels show fluorescence images of GFP-actin, and right panels show IRM images. (A) IRM images represent a darker tone (arrowheads) at MiDAS regions compared with that present at other ventral membrane regions. Therefore, the cell membrane at MiDAS regions is closer to the substratum than the other ventral cell membrane regions. (B,C) Cell bodies blown away by a jet of buffer from a pipette under confocal microscopy. Left panels show a half of dividing cells before blowing, and right panels show the same areas after blowing away the cell bodies, as revealed by fluorescence microscopy for GFP actin and phase-contrast microscopy. The figures are representative results from 20 cells. Note that only MiDAS regions remained attached to the substratum, indicating that dividing cells strongly attach to the substratum mainly at the MiDAS regions. Bar, 5 µm.