Fig. 4. DFer is required for normal leading edge morphology and normal rates of closure. (A,B) Late stage 16 wild-type embryos (A) have been dorsally closed for approximately three hours, whereas late stage 16 dfer¹ embryos (B) are dorsally open (white, anti-phospho-tyrosine). (C) DFerRB rescues dorsal closure (late stage 16 UAS-DFerRB/+;daGAL4,dfer¹/dfer¹). (D) At stage 14, leading edge cells elongate dorsoventrally (arrow), develop a thick F-actin cable (up arrowhead), and extend filopodial and lamellipodial protrusions (down arrowheads). (E) In dfer¹ embryos, the F-actin cable is greatly reduced (up arrowhead), but filopodia are still present (down arrowheads). (F) DFerRB expression largely restores the F-actin cable (arrowhead; white, Alexa568-Phalloidin; UAS-DFerRB/+;daGAL4,dfer¹/dfer¹ embryos). (G) At stage 14, the leading edge is enriched for P-Tyr, particularly at the contact points between adjacent leading edge cells (arrowhead). (H) In dfer¹ embryos, P-Tyr staining is reduced (arrowhead). (I) In rescued embryos, P-Tyr staining is restored (arrowhead).