Histological analyses of human AD sections from the hippocampus have shown that the AQP1 expression appears to be localized in multipolar fibrillary astrocytes surrounding neurons, whereas AQP4 expression appears to be more diffusely distributed in astrocytes (34), suggesting that some of the spatiotemporal changes in AQP expression noted here might reflect changes in the regional status of astrocyte populations. This evidence concerns the gene AQP1 and Alzheimer disease.