Figure 1. MeCP2 is a transcriptional repressor of SNAT1 in microglia. A, ChIP-seq analysis revealed enrichment of MeCP2 binding sites within the gene body of SLC38A1, coding for the glutamine transporter SNAT1. a, The locations of uniquely mapped reads are shown as a series of peaks in the custom University of California Santa Cruz genome browser track. b, As a control, an intergenic region telomeric to SLC38A1 reveals very low levels of MeCP2 binding. B, Representative Western blots of lysates of primary neurons [14 d in vitro (DIV)], astrocytes (14 DIV), and microglia (11–12 DIV) cultured from neonatal mice of the indicated genotype. SNAT1 migrated as triplet bands ∼50 kDa. The band intensity of microglial SNAT1 was rather weak compared with that of neurons or astrocytes, and therefore the blots for microglial SNAT1 were developed longer. C, The bar graph shows mean ± SEM of microglial SNAT1 band intensities, normalized by those of β-actin, from six independent experiments. D, Cultured primary microglia of the indicated genotype were immunofluorescently costained for Iba-1 (red) and SNAT1 (green) and counterstained with DAPI (blue). Representative photomicrographs are shown. The insets show magnified images of the same cells indicated by the arrows. E, Sections of hippocampus of 8-week-old mice were immunofluorescently costained for Iba-1 (red) and SNAT1 (green) and imaged under a confocal microscope. Arrows point to representative Iba-1-positive microglia. F, The bar graph shows mean ± SEM of IntDen values of microglial SNAT1 immunoreactivity in sections, which were quantified in Iba-1-positive areas as described in Materials and Methods. Five 8-week-old mice per group were studied. G, Sections consecutive to those used in E were coimmunostained for GFAP (green)/SNAT1 (red) or NeuN (green)/SNAT1 (red). H, Western blot analysis of SNAT1 in brain homogenates from four Mecp2+/y and four Mecp2−/y (8-week-old) mice. I, Mecp2 knockdown in BV-2 microglial cells by two siRNAs increased the level of SNAT1, but not SNAT2, transcript, which is shown by qPCR (n = 6). J, Western blot analysis of the indicated proteins in BV-2 cells with Mecp2 knockdown by the two siRNAs.