Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Gene expression profiles of wild type and Mecp2-null mice in three different regions of the brain

ABSTRACT: 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.

ORGANISM(S): Mus musculus

SUBMITTER: Rocio Urdinguio

PROVIDER: E-GEOD-11596 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Mecp2-null mice provide new neuronal targets for Rett syndrome.

Urdinguio Rocio G RG Lopez-Serra Lidia L Lopez-Nieva Pilar P Alaminos Miguel M Diaz-Uriarte Ramon R Fernandez Agustin F AF Esteller Manel M

PloS one 20081107 11

<h4>Background</h4>Rett syndrome (RTT) is a complex neurological 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 ide ...[more]

PMID: 18989361

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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 a NimbleGen mouse 385K genomic tiling microarray (the array set26 of a 37-array set, which covers the mouse chromosome 12 that includes the entire Dlk1-Gtl2 imprinting domain). Whole cell extract (WCE) was used as input controls for ChIP or MeDIP/WCE experiments. For ChIP/ChIP experiments, immunoprecipitated DNA from WT and KO CB was directly compared on the same microarrays. DNA methylation profiles in WT CB were also analyzed by methylated DNA immunoprecipitation (MeDIP) followed by hybridization to the same genomic tiling microarrays (MeDIP-chip).

Project description:Rett syndrome (RTT) is a neurodevelopmental disorder characterized by developmental regression around 6-18 months after birth, followed by a lifetime of intellectual disability, stereotyped behaviors, and motor deficits. RTT is caused by mutations in MeCP2, a methyl-CpG binding protein that was traditionally believed to repress gene expression. Gene expression studies of individual brain regions, however, have revealed that MeCP2 loss-of-function leads to the subtle activation and repression of its gene targets. However, these results may be confounded by the extensive neuronal cell heterogeneity inherent in these brain structures. To minimalize this issue of heterogeneity, we assessed whether Mecp2-null mice exhibited alterations in gene expression patterns in the striatum, a brain nucleus with relatively homogenous neuronal types and is highly relevant to the motor deficits observed in RTT. Despite the homogeneity of the tissue, the fold-change of the 127 differentially expressed genes we identified remained low with a mean change consistent with other studies. However, many of those genes differentially expressed in the striatum have not been previously identified in gene expression analyses of other brain regions. This suggests therefore that the differential expression of genes following loss of MeCP2 occurs in a tissue, or cell-type specific manner and thus MeCP2 function should be understood in a cellular context. In initiating this study, we reasoned that reducing the number of cell types in a microarray experiment may reveal transcriptional changes that are masked in a whole tissue analysis. We therefore focused on tissues more homogeneous in regards to the diversity of neuronal cell types they contain in order to discern gene expression changes in the absence of MeCP2. We chose to isolate the striatum, a tissue composed predominantly of GABAergic medium spiny neurons (MSNs). The striatum was resected from five symptomatic Mecp2-null (KO) male mice bearing the Bird allele and five wild-type (WT) littermates in a C57BL/6 background. We also isolated liver from the same individuals to serve as a non-neuronal control. RNA was isolated from these tissues, converted to cDNA, and hybridized to a single-channel Affymetrix GeneChip Mouse Exon 1.0 ST array for a total of 20 individual arrays.

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).

Dataset Information

Gene expression profiles of wild type and Mecp2-null mice in three different regions of the brain

Publications

Mecp2-null mice provide new neuronal targets for Rett syndrome.

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