With respect to cytotoxic edema, where ionic imbalance results in water influx into the cell within minutes after ischemia onset, AQP4 - deficiency seems to promote edema reduction: AQP4 knock-out mice with ischemic stroke showed improved neurological outcome and reduced cerebral edema within the first 24 h after MCAO. The gene discussed is AQP4; the disease is ischemic stroke.