Fig. 4. Evidence for AQP4-faciliated water transport at the leading edge of migrating cells. (A) Cultured astroglia at the edge of a wound (left) immunostained for AQP4 (green) and the plasma membrane marker WGA (red), with nuclei counterstained with DAPI. Arrow indicates direction of migration. Green:red fluorescence ratios (right) are shown for each of the corresponding pairs of squares shown on the left. Squares were placed at the leading edge (yellow, front) and away from the wound (purple, back). (B) Phase-contrast micrographs (top) and outline (bottom) of the leading end of a migrating wild-type and AQP4-null astroglial cell. Arrows indicate direction of migration. (Numbers are fractal dimensions.) (C) Experimental set-up (top) used for studying the effect of extracellular osmotic gradient on cell migration. Percentage of astroglia that migrated to the bottom surface of the Transwell within 10 hours (bottom), as a function of the difference in osmolality (top chamber minus bottom chamber). Data are mean±s.e.m.; *P<0.005 front vs back. Bar, 25 µm (A); 10 µm (B).