AGRN and Alzheimer disease: In contrast, the loss of agrin expression has been shown to be correlated with the loss of expression of junctional proteins in brain vessels of human glioblastoma specimens or with the enhanced BBB leakiness to blood-borne molecules in brains of patients with Alzheimer’s disease (Rascher et al. 2002; Berzin et al. 2000), or after global cerebral ischemia (Baumann et al. 2009) supporting a potential role of agrin in BBB maintenance.