Clec14a is a member of the thrombomodulin (TM) family, but its function has not yet been determined. Here, we report that Clec14a is a plasma membrane protein of endothelial cells (ECs) expressed specifically in the vasculature of mice. Deletion mutant analysis revealed that Clec14a mediates cell-cell adhesion through its C-type lectin-like domain. Knockdown of Clec14a in ECs suppressed cell migratory activity and filopodial protrusion, and delayed formation of tube-like structures. These findings demonstrate that Clec14a is a novel EC-specific protein that appears to play a role in cell-cell adhesion and angiogenesis. (C) 2010 Elsevier Inc. All rights reserved.