M1–AQP4, but not M23–AQP4, localizes to the leading edge of migrating astrocytes and glioma cells. (A) Schematic showing predicted distribution of M1– or M23–AQP4 and F-actin labeling in migrating cells and TIRF images showing F-actin and AQP4 distribution in M1- and M23-transfected AQP4^−/− astrocytes during migration into a scratch wound. White dashed line demarcates the cell leading edge. (B) AQP4 staining intensity as a function of distance from the leading edge for cells labeled as in A (mean ± SE, 10 cells; *, P < 0.05 between M1 and M23 by t test at the indicated distance). (C) F-actin, AQP4, and wheat germ agglutinin (WGA) labeling in randomly migrating U87-MG cells transfected with M1– or M23–AQP4. (D) Ratio of mean AQP4 staining intensity in F-actin–rich lamellipodial (outlined) and somatic (rest of image) regions normalized to the ratio of WGA staining intensity in the same regions (mean ± SE, 10 cells; *, P < 0.001).