δ-Catenin regulates endothelial cell motility and vascular tubule formation in vitro in a gene dosage–sensitive manner. (A) Microvascular endothelial cells were isolated and pooled from lungs (5 mice per group) of wild-type littermates, δ-catenin heterozygous-null, and homozygous-null mice. The endothelial cells were sorted with a CD31 antibody with a FACStarPlus flow cytometer. The percentage of CD31 positive cells was indicated in each graph. (B) The levels of δ-catenin in wild-type, δ-catenin^+/−, and δ-catenin^−/− endothelial cells were evaluated in cell lysates by Western blot. Endothelial cell migration and vascular tubule formation were measured in Transwell assay or Matrigel assay, respectively. (C) Migrated cells were counted after a 5-h incubation in 10 randomly selected high-power fields under microscopy. The data were collected from three independent experiments. Mean and SE were plotted. *, P < 0.01. (D) Vascular tubule formation was measured 18 h after cell plating. Vascular cross points were counted from 10 randomly selected high-power fields under microscopy. The data were collected from three independent experiments. *, P < 0.01. (E) Cell proliferation was measured by BrdU incorporation. The experiment was done in duplicate and repeated three times.