Project description:Background. Rett syndrome (RTT) is a complex neurodevelopmental disorder that is one of the most frequent causes of mental retardation in women. A great landmark in research in this field was the discovery of a relationship between the disease and the presence of mutations in the gene that codes for the methyl-CpG binding protein 2 (MeCP2). Currently, MeCP2 is thought to act as a transcriptional repressor that couples DNA methylation and transcriptional silencing. The present study aimed to identify new target genes directly regulated by Mecp2 in a mouse model of RTT. Methodology. We have compared the gene expression profiles of wild type (WT) and Mecp2-null (KO) mice in three regions of the brain (cortex, midbrain, and cerebellum) by using cDNA microarrays. The results obtained were confirmed by quantitative real-time PCR. Subsequent chromatin immunoprecipitation assays revealed seven direct target genes of Mecp2 bound in vivo (Dlk1, Mobp, Plagl1, Ddc, Mllt2h, Eya2, and S100a9), and two overexpressed genes due to an indirect effect of a lack of Mecp2 (Irak1 and Prodh). Bisulfite sequencing analysis of the methylation patterns of promoters of the described genes showed no differences between WT and KO mice, demonstrating that methylation differences were not the cause of the observed expression changes. Moreover, the regions bound by Mecp2 were always methylated, suggesting the involvement of the methyl-CpG binding domain of the protein in the mechanism of interaction. Conclusions. We identified new genes that are overexpressed in KO mice and are excellent candidate genes for involvement in various features of the neurodevelopmental disease. Our results demonstrate new targets of MeCP2 and provide us with a better understanding of the underlying mechanisms of RTT. Comparative experiment: Mecp2-null (KO) mice vs. their corresponding age-mated wild type (WT) littermates (CONTROLS). Four couples of KO-WT animals are used and three different brain regions are studied from each couple; cortex, midbrain, and cerebellum.

Project description:MicroRNAs (miRNAs) are a class of small non-coding RNAs that function as post-transcriptional regulators of gene expression. Many miRNAs are expressed in the developing brain and regulate multiple aspects of neural development including neurogenesis, dendritogenesis and synapse formation. Rett syndrome (RTT) is a progressive neurodevelopmental disorder caused by mutations in the gene encoding Methyl-CpG binding protein 2 (MECP2). While Mecp2 is known to act as a global transcriptional regulator, miRNAs that are directly regulated by Mecp2 in the brain are not known. Using massively parallel sequencing methods, we have identified miRNAs whose expression is altered in cerebella of Mecp2-null mice before and after the onset of severe neurological symptoms. In vivo genome-wide analyses indicate that promoter regions of a significant fraction of dys-regulated miRNA transcripts, including a large polycistronic cluster of brain-specific miRNAs, are DNA methylated and directly bound by Mecp2. Functional analysis demonstrates that the 3’ untranslated region (UTR) of messenger RNA encoding Brain-derived neurotrophic factor (Bdnf) can be targeted by multiple miRNAs aberrantly up-regulated in absence of Mecp2. Taken together, these results suggest that dys-regulation of miRNAs may contribute to RTT pathoetiology, and also provide a valuable resource to further investigate the role of miRNAs in RTT. Chromatin extracted from postnatal 6-8 week old cerebellar (CB) tissues of wild-type (WT) or Mecp2-null (KO) male mice was immunoprecipitated with indicated antibodies and analyzed by NimbleGen custom mouse 385K promoter tiling microarrays (a 2-array set covering the promoter regions of all Refseq protein-coding genes and miRNA transcripts with predicted transcription start sites). Whole cell extract (WCE) was used as input controls in all experiments. DNA methylation profiles in WT CB were also analyzed by methylated DNA immunoprecipitation (MeDIP) followed by hybridization to the same promoter tiling microarrays (MeDIP-chip).

Project description:Mutations in methyl-CpG-binding protein 2 (MeCP2), a major epigenetic regulator, are the predominant cause of Rett syndrome, an X-linked neurodevelopmental disorder. We previously found that Mecp2-null microglia are functionally impaired, and that engraftment of wild-type monocytes into the brain of Mecp2-deficient mice attenuates pathology. In this study we show that Mecp2 is expressed in macrophage and monocyte populations throughout the body, and is indispensable for their transcriptional regulation in multiple contexts. We demonstrate that Mecp2-null mice progressively lose or are chronically deficient in several macrophage populations and resident monocytes. Postnatal re-expression of Mecp2 driven by a tamoxifen-inducible CX3CR1 promoter significantly increased the lifespan of otherwise Mecp2-null mice, suggesting that epigenetic regulation of macrophage function by Mecp2 significantly contributes to pathology. RNA-Seq of acutely isolated microglia and peritoneal macrophages (to our knowledge, the first cell-specific RNA-Seq analysis comparing Mecp2-null and wild type cells of any kind) revealed significantly increased transcription of glucocorticoid- and hypoxia-signaling genes in Mecp2-null cells compared to that in their wild-type counterparts, suggesting that Mecp2 functions as a repressor of these pathways. Furthermore, in-vitro and in vivo validation studies demonstrated that the absence of Mecp2 is associated with cell-intrinsic dysfunction of signaling underlying inflammatory activation, suggesting that Mecp2 is important for regulation of specific macrophage gene-expression programs in response to stimuli and stressors. Our findings demonstrate a fundamental role for Mecp2 in the regulation of macrophage functions, which may provide a link to pathologies in Rett syndrome across multiple organs. Mecp2-null microglia and resident peritoneal macrophages from 10-12 week old mice were acutely isolated via AutoMACS, total RNA collected, and analyzed via RNA-Seq to compare for transcriptional differences in microglia and macrophages in the absence of Mecp2.

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