AQP4 and amyotrophic lateral sclerosis: With regard to the role of astrocytic AQP4 on the BBB in ALS, Watanabe-Matsumoto et al. (2018) not only demonstrated the overexpression of AQP4 in astrocytes of mice and patients with ALS, but also found an improvement in the permeability of the BBB in ALS mice deficient in AQP4.