Project description:Background MeCP2, methyl-CpG-binding protein 2, binds to methylated cytosines at CpG dinucleotides, as well as to unmethylated DNA, and affects chromatin condensation. MECP2 mutations in females lead to Rett syndrome, a neurological disorder characterized by developmental stagnation and regression, loss of purposeful hand use and speech, stereotypic hand movements, deceleration of brain growth, autonomic dysfunction and seizures. Most mutations occur de novo during spermatogenesis. Located at Xq28, MECP2 is subject to X inactivation, and affected females are mosaic. Rare hemizygous males suffer from a severe congenital encephalopathy. Methods To identify pathways mis-regulated by MeCP2 deficiency, microarray-based global gene expression studies were carried out on cerebellum of Mecp2 mutant mice. We compared transcript levels in mutant/wildtype male sibs of two different MeCP2-deficient mouse models at 2, 4 and 8 weeks of age. Increased transcript levels were evaluated by real-time quantitative RT-PCR. Chromatin immunoprecipitation assays were used to document in vivo MeCP2 binding to promoter regions of candidate target genes. Results In the mutants, several hundred genes showed altered expression levels. Twice as many were increased than decreased, and only 27 genes were differentially expressed at more than one time point. The number of misregulated genes was 30% lower in mice with an exon 3 deletion (Mecp2tm1.1Jae) than in mice with a larger deletion (Mecp2tm1.1Bird). Between the mutants, few misregulated genes overlapped at each time point. Real-time quantitative RT-PCR assays validated increased transcript levels for four genes: Irak1, interleukin-1 receptor-associated kinase 1; Fxyd1, phospholemman, associated with Na, K-ATPase; Reln, encoding reelin, an extracellular signaling molecule essential for neuronal lamination and synaptic plasticity; and Gtl2/Meg3, an imprinted maternally expressed non-translated RNA that serves as a host gene for C/D box snoRNAs and microRNAs. Chromatin immunoprecipitation assays documented in vivo MeCP2 binding to promoter regions of Fxyd1, Reln, and Gtl2. Conclusions Transcriptional profiling of cerebellum failed to detect significant global changes in Mecp2-mutant mice. Increased transcript levels of Irak1, Fxyd1, Reln, and Gtl2 may contribute to the neuronal dysfunction in MeCP2-deficient mice and individuals with Rett syndrome. Our data provide testable hypotheses for future studies of the regulatory or signaling pathways that these genes act on.

Project description:Background MeCP2, methyl-CpG-binding protein 2, binds to methylated cytosines at CpG dinucleotides, as well as to unmethylated DNA, and affects chromatin condensation. MECP2 mutations in females lead to Rett syndrome, a neurological disorder characterized by developmental stagnation and regression, loss of purposeful hand use and speech, stereotypic hand movements, deceleration of brain growth, autonomic dysfunction and seizures. Most mutations occur de novo during spermatogenesis. Located at Xq28, MECP2 is subject to X inactivation, and affected females are mosaic. Rare hemizygous males suffer from a severe congenital encephalopathy. Methods To identify pathways mis-regulated by MeCP2 deficiency, microarray-based global gene expression studies were carried out on cerebellum of Mecp2 mutant mice. We compared transcript levels in mutant/wildtype male sibs of two different MeCP2-deficient mouse models at 2, 4 and 8 weeks of age. Increased transcript levels were evaluated by real-time quantitative RT-PCR. Chromatin immunoprecipitation assays were used to document in vivo MeCP2 binding to promoter regions of candidate target genes. Results In the mutants, several hundred genes showed altered expression levels. Twice as many were increased than decreased, and only 27 genes were differentially expressed at more than one time point. The number of misregulated genes was 30% lower in mice with an exon 3 deletion (Mecp2tm1.1Jae) than in mice with a larger deletion (Mecp2tm1.1Bird). Between the mutants, few misregulated genes overlapped at each time point. Real-time quantitative RT-PCR assays validated increased transcript levels for four genes: Irak1, interleukin-1 receptor-associated kinase 1; Fxyd1, phospholemman, associated with Na, K-ATPase; Reln, encoding reelin, an extracellular signaling molecule essential for neuronal lamination and synaptic plasticity; and Gtl2/Meg3, an imprinted maternally expressed non-translated RNA that serves as a host gene for C/D box snoRNAs and microRNAs. Chromatin immunoprecipitation assays documented in vivo MeCP2 binding to promoter regions of Fxyd1, Reln, and Gtl2. Conclusions Transcriptional profiling of cerebellum failed to detect significant global changes in Mecp2-mutant mice. Increased transcript levels of Irak1, Fxyd1, Reln, and Gtl2 may contribute to the neuronal dysfunction in MeCP2-deficient mice and individuals with Rett syndrome. Our data provide testable hypotheses for future studies of the regulatory or signaling pathways that these genes act on. A genetic modification design type is where an organism(s) has had genetic material removed, rearranged, mutagenized or added, such as knock out. Computed

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.

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Cerebellar gene expression profiles of mouse models for Rett Syndrome reveal MeCP2 targets

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