FIGURE 2. PTP-PEST is required for tail retraction.

A, to visualize the development of tails, control or PTP-PEST −/− cells were videotaped using differential interference contrast microscopy. Cells were plated for 1 h on FN-coated dishes in serum-containing medium, then filmed for 3 h. Frames were captured every 90 s. Control fibroblasts (top panel, supplemental video 1) show little change in shape or movement; however, PTP-PEST −/− fibroblasts (bottom panel, supplemental video 2) exhibit increased membrane activity. After 2 h of plating, tails develop and continue to elongate as the cell body moves forward (supplemental video 2). B, by 4 h tails have formed in the PTP-PEST null cells, but they are unable to retract (see arrows and video 3). C, PTP-PEST −/− cells are partially able to migrate in a haptotaxis migration assay but are unable to move through a transwell filter coated on the top and bottom side, indicating an ability to form protrusions but an inability to release adhesions formed at the cell rear. D, control or PTP-PEST −/− cells were scored over a time course of plating on FN for the percentage of cells that developed tails. Although the re-expressers do not develop tails, 60–70% of the −/− cells form tails within 90 min after plating.