{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Claudin-5 is a member of the claudin family. Claudins are integral membrane proteins and components of tight junction strands. Tight junction strands serve as a physical barrier to prevent solutes and water from passing freely through the paracellular space between epithelial or endothelial cell sheets. Claudin-5 is an endothelial cell-specific component of tight junction strands. Mutations in claudin-5 have been found in patients with velocardiofacial syndrome. Claudin-5 labels endothelial cells as well as bronchial and lung epithelial cells. In tumors, claudin-5 expression has been found in lung adenocarcinoma and squamous carcinoma. In serous ovarian adenocarcinoma, increased claudin-5 expression is associated with aggressive behavior."}]}]}