Using global or astrocyte conditional (GFAP promoter) AQP4‐knockout mice, AQP4 gene deletion was associated with a 35% and 31% decrease in cytotoxic oedema following stroke and systemic hypo‐osmotic stress, respectively (Haj‐Yasein et al., 2011; Manley et al., 2000). The gene discussed is AQP4; the disease is Stroke.