In several models of neurological diseases, especially stroke or cerebral ischemia-reperfusion injury and Alzheimer's disease a link was established between decreased expression, disrupted organization or redistribution of claudin-5 and occludin and increased BBB permeability (Willis et al., 2010; Jiao et al., 2011; Yang and Rosenberg, 2011; Hartz et al., 2012). The gene discussed is OCLN; the disease is early-onset autosomal dominant Alzheimer disease.