GAD1 and glioblastoma: In line with this result, a comprehensive study on GBM databases showed that expression of three GABA related genes—glutamate decarboxylase 1 (GAD1) and 2 (GAD2) and 4-aminobutyrate aminotransferase (ABAT)—are lower in mesenchymal GBM, indicating that a decreased production and possibly an increased catabolism may be linked to poor outcome [188].