WASp-null immature DCs expressing a GFP-WASp fusion protein.

WASp-null immature DCs microinjected with a GFP-WASp fusion protein form podosomes and lamellipodia. Confocal images are shown in horizontal (panels A-D) and vertical (panels E-F) planes. TRITC-phalloidin staining of microinjected WASp-null DCs is shown in left-hand panels (panels A, C, E). Right-hand panels show expression of EGFP (panel B) or EGFP-WASp (panels D, F). Confocal images are shown in horizontal (panels A-D) and vertical (panels E-F) planes. Expression of EGFP in WASp-null DCs shows a diffuse distribution within the cytoplasm (panel B). In contrast, expression of EGFP-WASp fusion protein results in the appearance of podosomes at the substratum interface (panels C-F). In addition, EGFP-WASp–expressing cells are capable of forming broad lamellipodia (arrowhead in panel D), behind which the podosomes are located. A normal DC morphology is therefore reconstituted.