AQP4 and neuromyelitis optica: Expression and distribution changes of AQP4 were reported in reactive astrocyte migration (upregulated and polarized towards the leading edge of migration), brain edema (both up- and downregulation reported), brain tumor (upregulated), epilepsy (upregulated and localized towards the neutrophil) and mediating immunologic injury in neuromyelitis optica (decreased AQP4) [51,53,226,245,258,259,260,261,262,263].