virtually 100% viability of both the control and MeCP2-null astrocytes after 24 h incubation with 10 mM Glu. Glu-induced gliotoxic effects have been previously reported by Chen et al., and are probably due to distinct differences in culture conditions, specifically the presence of glucose. These results showed that H2O2 and NH4Cl had a similar effect in both strains of astrocytes. There was no significant difference in viability between the control and MeCP2-null astrocyte cultures, indicating that MeCP2 deficiency did not affect astrocyte viability upon treatment with H2O2 and NH4Cl. Effects of glutamate on glutamate transporters and glutamine synthetase transcripts in MeCP2-null astrocytes High extracellular Glu interferes with the expression of the astrocyte transporter subtypes, excitatory amino acid transporter 1/glutamate/aspartate transporter and EAAT2/glutamate transporter-1 . To explore the effects of Glu on the expression of Glu transporter genes in cultured astrocytes from wild-type and MeCP2-null mouse brains, we asked whether treatment with 1.0 mM Glu altered expression of EAAT1 and EAAT2 mRNA, using a semi-quantitative RTPCR assay. EAAT1 and EAAT2 mRNA were expressed in both wild-type and MeCP2-null astrocytes, and were slightly higher in controls than in MeCP2-null astrocytes. Both EAAT1 and EAAT2 mRNA levels were altered in the control astrocytes after treatment with 1.0 mM Glu. EAAT1 mRNA levels decreased significantly in the wild-type astrocytes, both 12 h and 24 h after treatment with Glu. In contrast, EAAT1 decreased significantly in the MeCP2-null astrocytes, at 12 h but not 24 h after treatment. As with EAAT1, EAAT2 mRNA levels also decreased significantly in the control astrocytes, both 12 h and 24 h after treatment. However, EAAT2 decreased significantly in MeCP2-null astrocytes, 24 h but not 12 h after treatment. In addition, the effects of Glu on EAAT1 and EAAT2 relative fold expression at 12 h were altered in 23416332” the MeCP2-null astrocytes. These results suggest that the loss of MeCP2 leads to transcriptional dysregulation of these genes, either directly or indirectly. One important enzyme that plays a role in the Glu metabolic pathway is glutamine synthetase . GS is mainly located in astrocytes; cultured astrocytes response to Glu with increased GS expression. Consistent with this, 1.0 mM Glu treatment stimulated GS mRNA expression in both the wildtype and MeCP2-null astrocytes about 1.2-fold after 12 h but not 24 h. In addition, MeCP2 deficiency did not modify the Results 10460232” Characterization of MeCP2-null astrocytes It was recently reported that MeCP2 is normally present not only in neurons but also in glia, including astrocytes, oligodenrocytes, and microglia. To determine the roles of MeCP2 in astrocytes, we cultured cerebral cortex astrocytes from both wild-type and MeCP2-null mouse brains. MeCP2-null astrocytes exhibited a large, flattened, polygonal shape identical to that of the wild-type astrocytes, suggesting that normal patterns of cellular recognition and contact were present. Semi-quantitative RT-PCR using primer sets that specifically amplify two splice variants, Mecp2 e1 and e2, showed that control astrocytes expressed Mecp2 e1 and e2, whereas neither Mecp2 variant was detectable in MeCP2-null astrocytes. We further confirmed expression of MeCP2 by immunocytochemical staining of astrocytes. In control samples, almost all Scopoletin web GFAP-positive cells exhibited clear nuclear MeCP2 immunoreactivity in astrocytes,