In stroke, vascular endothelial cell (EC) dysfunction at the compromised BBB involves paracellular leakage, as evidenced by the degradation of tight junction (TJ) proteins including claudin-5 (CLDN5), occludin (OCLN), and zonula occludens-1 (ZO-1/TJP1) [13,14]. The gene discussed is CLDN5; the disease is stroke disorder.