Cell extracts were prepared [9 (link), 32 (link)], electrophoresed by sodium dodecyl sulfate– polyacrylamide gel electrophoresis (SDS-PAGE), transferred to nitrocellulose, and probed with anti-human PlexinD (R&D Systems), anti- αTubulin (EMD Millipore), anti-JAGGED1( Cell Signaling Technology, Danvers, MA), anti-human Calponin (Dako, Carpinteria, CA), anti-human CD31 (Santa Cruz Biotechnology, Inc., Dallas, Texas), anti-human sm22α (Abcam, Cambridge, MA) and anti-human β-actin (Abcam) antibodies. All signals detected by enhanced chemiluminescence.