Although BEC junctional strands are stable in the healthy brain [11, 12], we have shown using green fluorescent protein (GFP)-tagged Claudin-5 that BBB TJs in the cortical penumbra that succumbs later to infarct become highly dynamic and exhibit structural abnormalities between 24 and 58 h after transient middle cerebral artery occlusion (t-MCAO), a rodent model for ischemic stroke [11]. The gene discussed is CLDN5; the disease is ischemic stroke.