GFAP and central nervous system disorder: Astrocytes express high levels of GFAP, which is also upregulated in reactive astrocytes and is often associated with the severity of CNS disorders (Escartin et al., 2019), though this correlation may be impacted by the regional differences in basal GFAP expression (Griemsmann et al., 2015; Ben Haim and Rowitch, 2017).