Hence, GFAP expression might not capture the widespread phenotype of astrocyte dysfunction in post-mortem studies of MDD, including morphometric differences in cortical fibrous astrocytes (25), reduced vascular coverage (26), differential methylation patterns for genes enriched in astrocytes (27), and abnormally low expression levels of astrocytic glutamate transporters (18, 27, 28), and gap junction proteins (29–31). The gene discussed is GFAP; the disease is major depressive disorder.