rDrm interaction with endothelial cells. (A) rDrm induces MAE-cell sprouting in fibrin gel (▨), MAE-cell migration in a Boyden chamber (⊡), and BAE-cell invasion in type I collagen gel (▪) (data expressed as mean ± SD); inset, tyrosine phosphorylation of focal adhesion contacts (arrows) in SIE cells stimulated for 10 minutes with 100 ng/mL rDrm. Cell analysis was performed using a Zeiss Axiovert 200M microscope equipped with a Plan-Apochromat 63×/1.4 NA oil objective. (B) Binding of ¹²⁵I-rDrm to SIE cells; inset, cross-linking of unlabeled rDrm to SIE cells followed by immunoprecipitation and Western blotting with anti-Drm antibody. (C) Cross-linking of ¹²⁵I-rDrm to SIE cells with or without a 100-fold molar excess of unlabeled rDrm or BMP4. ¹²⁵I-rDrm complexes were visualized by autoradiography of the SDS-PAGE gel.