Endothelial Shc is required for tube assembly and sprouting in vivo. (A) The fibrin gel bead assay was performed using MLECs isolated from the same mice used in Figure 2. On day 3 after seeding the cell-covered beads in gel, cultures were fixed and stained for phalloidin (green) and DRAQ5 (blue). Quantifications (bottom) were performed by counting at least 15 beads per genotype and are expressed as means ± SEM of n = 2 independent experiments at 4 replicates per experiment. *P < .05.