TuJ1 (class III β-tubulin) as phenotypic marker of lymphatic and venous valves

Lymphatic and venous valves are essential for unidirectional circulation; however, no specific marker has been described for these valves. Here, we show that TuJ1 (class III β-tubulin) is expressed strongly in valve endothelium but not in nonvalvular endothelium lining of lymphatics. TuJ1 is also expressed in venous valves mainly at the tip of leaflets. In contrast, endothelial markers CD31, CD34, and factor 8-related antigen did not distinguish valves from vascular endothelium. TuJ1 is also expressed irregularly in the vascular endothelium of hemangiomas. The data suggest that TuJ1 may be a phenotypic marker of lymphatic and venous valves, discriminating lymphatic and venous valvular endothelial cells from nonvalve lymphatic and vascular endothelial cells.