Sequence Features Accurately Predict Genome-wide MeCP2 Binding in vivo
Ontology highlight
ABSTRACT: MECP2 is critical for proper brain development and expressed at near-histone levels in neurons, but the mechanism of its genomic localization remains poorly understood. Using high-resolution MeCP2 binding data, we show that genetic features alone can predict binding with 88% accuracy. Integrating MeCP2 binding and DNA methylation in a probabilistic graphical model, we demonstrate that previously reported methylation preferences may be due to MeCP2âs affinity to GC-rich chromatin, a result replicated using published data. Furthermore, MeCP2 co-localized with nucleosomes, and Mecp2 deletion led to nucleosome repositioning. Finally, MeCP2 binding downstream of promoters correlated with increased expression in Mecp2 deficient neurons. Study of genetic and epigenetic determinants of MeCP2 binding using MeCP2 ChIP-seq, MNase-seq, Bisulfite-seq and RNA-seq. Please see individual sample record for details on experimental design.
Project description:A unique signature of neuronal transcriptomes is the high expression of the longest genes in the genome (e.g. >100 kilobases). These genes encode proteins with essential functions in neuronal physiology, and disruption of long gene expression has been implicated in neurological disorders. DNA topoisomerases resolve topological constraints that arise on DNA and facilitate the expression of long genes in neurons. Conversely, methyl-CpG binding protein 2 (MeCP2), which is disrupted in Rett syndrome, can act as a transcriptional repressor to downregulate the expression of long genes. The molecular mechanisms underlying the regulation of long genes by these factors are not fully understood, however, and whether or not they directly influence each other is not known. Here, we identify a functional interaction between MeCP2 and Topoisomerase II-beta (TOP2β) in neurons. We show that MeCP2 and TOP2β physically interact in vivo and map protein sequences sufficient for their physical interaction in vitro. We profile TOP2β activity genome-wide in neurons and detect enrichment at regulatory regions and gene bodies of long neuronal genes, including long genes regulated by MeCP2. Further, we find that knockdown and overexpression of MeCP2 leads to altered TOP2β activity at MeCP2-regulated genes. Our findings uncover a mechanism by which MeCP2 inhibits the activity of TOP2β at long genes in neurons and suggest that this mechanism is disrupted in neurodevelopment disorders caused by mutation of MeCP2.
Project description:Rett syndrome (RTT) is one of the most prevalent female mental disorders. De novo mutations in methyl CpG binding protein 2 (MeCP2) are a major cause of RTT. MeCP2 regulates gene expression as a transcription regulator as well as through long-range chromatin interaction. Because MeCP2 is present on the X chromosome, RTT is manifested in a X-linked dominant manner. Investigation using murine MeCP2 null models and post-mortem human brain tissues has contributed to understanding the molecular and physiological function of MeCP2. In addition, RTT models using human induced pluripotent stem cells derived from RTT patients (RTT-iPSCs) provide novel resources to elucidate the regulatory mechanism of MeCP2. Previously, we obtained clones of female RTT-iPSCs that express either wild type or mutant MECP2 due to the inactivation of one X chromosome. Reactivation of the X chromosome also allowed us to have RTT-iPSCs that express both wild type and mutant MECP2. Using these unique pluripotent stem cells, we investigated the regulation of gene expression by MeCP2 in pluripotent stem cells by transcriptome analysis. We found that MeCP2 regulates genes encoding mitochondrial membrane proteins. In addition, loss of function in MeCP2 results in de-repression of genes on the inactive X chromosome. Furthermore, we showed that each mutation in MECP2 affects a partly different set of genes. These studies suggest that fundamental cellular physiology is affected by mutations in MECP2 from very early fetal development and that a therapeutic approach targeting to unique forms of mutant MeCP2 is needed. RNA samples from normal ESCs/iPSCs, RTT-iPSCs and MeCP2 KD iPSCs were obtained. Gene expression of those cells were analyzed.
Project description:Rett syndrome is a human intellectual disability disorder that is associated with mutations in the X-linked MECP2 gene. Theepigenetic reader MeCP2 binds to methylated cytosines on the DNA and regulates chromatin organization. We have shownpreviously that MECP2 Rett syndrome missense mutations are impaired in chromatin binding and heterochromatinreorganization. Here, we performed a proteomics analysis of post-translational modifications of MeCP2 isolated from adult mousebrain. We show that MeCP2 carries various post-translational modifications, among them phosphorylation on S80 and S421, whichlead to minor changes in either heterochromatin binding kinetics or clustering. We found that MeCP2 is (di)methylated on severalarginines and that this modification alters heterochromatin organization. Interestingly, we identified the Rett syndrome mutationsite R106 as a dimethylation site. In addition, co-expression of protein arginine methyltransferases 1 and 6 lead to a decrease ofheterochromatin clustering. Altogether, we identified and validated novel modifications of MeCP2 in the brain and show that thesecan modulate its ability to bind as well as reorganize heterochromatin, which may play a role in the pathology of Rett syndrome.
Project description:MECP2-R270X transgenic mice (TG) and MECP2-G273X TG mice were generated in the Zoghbi Lab. These mice express the respective truncated form of MeCP2 tagged with GFP at the C-terminus from a transgenic human PAC containing all known regulatory sequences. These transgenes were maintained on a wild-type pure FVB background. For experiments each transgenic line was crossed by Mecp2 null mice (Mecp2 tm1.1Bird) on a pure 129SvEv background and the resulting male F1 hybrid progeny (FVB;129SvEv) that lacked endogenous MeCP2 expression but expressed either transgene (Mecp2 -/y; MECP2-R270X TG or Mecp2-/y; MECP2-G273X TG) were used for ChIP-Seq analysis. Whole brain from either the R270X mice (Mecp2 -/y; MECP2-R270X TG) or the G273X mice (Mecp2 -/y; MECP2-G273X TG) was formaldehyde crosslinked and purified chromatin was immunoprecipitated with anti-GFP antibody (Abcam ab6556). 2 samples: R270X (Mecp2 -/y; MECP2-R270X TG) and G273X (Mecp2 -/y; MECP2-G273X TG) both on an F1 (FVB;129SvEv) hybrid background
Project description:We have performed gene expression profiling of the MECP2 transgenic monkey, taking advantage of recently completed genome sequencing for the cynomolgus monkey. We found interesting changes in the pattern of alternative splicing of many genes, including genes coding synaptic proteins (e.g., neurexin-3 and Shank-3) and metabolism-related proteins, as compared to the wild-type monkey. This study provides important information for understanding the impact of disease-related gene on brain development. Examination of transcriptome in brain tissues of wild-type and MECP2 transgenic monkeys.
Project description:Although the function of DNA methylation in gene promoter regions is well established in transcriptional repression, the function of the evolutionarily conserved widespread distribution of DNA methylation in gene body regions remains incompletely understood. Here, we show that DNA methylation is enriched in included alternatively spliced exons (ASEs) and inhibiting DNA methylation results in aberrant splicing of ASEs. The methyl-CpG binding protein MeCP2 is enriched in included ASEs, particularly those that are also highly DNA methylated, and inhibition of DNA methylation disrupts specific targeting of MeCP2 to exons. Interestingly, ablation of MeCP2 results in increased nucleosome acetylation and aberrant skipping events of ASEs. We further show that inhibition of histone deacetylases leads to a highly significant overlap of exon skipping events caused by knocking-down MeCP2. Together, our data indicate that intragenic DNA methylation operates in exon definition to modulate alternative splicing and can enhance exon recognition via recruitment of the multifunctional protein MeCP2, which thereby maintains local histone hypoacetylation through its established interaction with HDACs. MeCP2 ChIP-Seq in IMR90 and HCT116 cells
Project description:The goal of this study was to characterize a novel Mecp2 allele in the laboratory rat, a distinct rodent species from the laboratory mouse with unique features. The allele was created by zinc finger-nuclease (ZFN) targeting (SAGE/Horizon) of the X-linked gene, Methyl-CpG-Binding Protein 2 (Mecp2), resulting in normal Mecp2 RNA abundance, but absent protein in male rats as expected due to the presence of only one copy of mutant Mecp2, and an approximate 50% reduction in female rats as expected from animals that harbor one wild-type copy and one mutant copy of Mecp2. Behavioral characterization of female rats with the Mecp2 ZFN allele and wild-type littermates was conducted, and Mecp2 ZFN/+ female rats showed behavioral phenotypes that were consistent with disease-like features present during the early stages of disease onset in the neurological disorder Rett syndrome. The goal of conducting RNAseq studies was to compare existing gene expression alterations in the Mecp2 rat with one of the most widely studied Mecp2 mouse model. Hypothalami were obtained from males with complete loss of MeCP2 (ZFN/y) and wild-type littermate male rats for RNA-seq studies. Common and unique gene expression alterations among the Mecp2 rodents that were then tested in human Rett and control postmortem brain revealed the benefit of combining findings from both models, suggesting the predictive validity of this approach for future studies for the identification of potential preclinical outcome measures. QPCR validation in an independent set of rats was conducted with a subset of genes from the Mecp2 ZFN rat RNA-seq data as an additional control measure. Taken together, these findings demonstrate that the Mecp2 rat model is a complementary tool with unique features for the study of RTT and highlight the potential benefit of cross-species analyses in identifying potential disease-relevant preclinical outcome measures. Transcriptional profiles of hypothalamic samples obtained from male rats haboring a novel zinc-finger nuclease Mecp2 loss-of-function allele and corresponding wild-type littermate rats were generated using RNA-seq
Project description:Rett syndrome (RTT; OMIM#312750) is a rare devastating neurodevelopmental disorder that represents the most common genetic cause of severe intellectual disability in girls. Mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene have been reported in over 95% cases of classical forms of RTT. Although initial studies supported a role for MeCP2 exclusively in neurons, recent data indicate a function also in astrocytes, which emerged as critical players involved in RTT pathogenesis through non-cell autonomous effects. Indeed, Mecp2 knock-out (KO) astrocytes cannot properly support neuronal maturation of wilt-type (WT) neurons and our data demonstrated a detrimental effect also on synaptogenesis and synaptic maintainence. Nevertheless, the molecular mechanisms by which RTT astrocytes can impact on neuronal health remains unknown. In comparison to previous studies exploring the transcriptomic and proteomic profiles of KO astrocytes per se, we used an indirect strategy to unveil the molecular mechanisms responsible for their negative action on neurons. We thus analysed the molecular pathways deregulated in WT neurons cultivated under the influence of KO (n=8) versus WT (n=7) astrocytes, in a transwell-based co-culture system, that allows the exchange of paracrine signals preventing cell-to-cell contact. Astrocytes were seeded on transwell inserts and transferred on neurons at Div0; the co-cultures were maintained until Div14. WT cortical neurons cultivated alone were also included (n=5).
Project description:Rett syndrome (RTT) is an X-linked dominant neurodevelopmental disorder caused by mutations in MECP2, encoding methyl-CpG-binding protein 2. MeCP2 is a transcriptional repressor elevated in mature neurons and is predicted to be required for neuronal maturation by regulating multiple target genes. Identifying primary gene targets in either Mecp2-deficient mice or human RTT brain has proven to be difficult, perhaps because of the transient requirement for MeCP2 during neuronal maturation. In order to experimentally control the timing of MeCP2 expression and deficiency during neuronal maturation, human SH-SY5Y cells undergoing mature neuronal differentiation were transfected with methylated MeCP2 oligonucleotide decoy to disrupt the binding of MeCP2 to endogenous targets. Genome-wide expression microarray analysis identified all four known members of the inhibitors of differentiation or inhibitors of DNA-binding (ID1, ID2, ID3 and ID4) subfamily of helix-loop-helix genes as novel neuronal targets of MeCP2. Chromatin immunoprecipitation analysis confirmed binding of MeCP2 near or within the promoters of ID1, ID2 and ID3, and quantitative RT-PCR confirmed increased expression of all four Id genes in Mecp2-deficient mouse brain. All four ID proteins were significantly increased in Mecp2-deficient mouse and human RTT brain using immunofluorescence and laser scanning cytometric analyses. Because of their involvement in cell differentiation and neural development, ID genes are ideal primary targets for MeCP2 regulation of neuronal maturation that may explain the molecular pathogenesis of RTT.
Project description:This SuperSeries is composed of the following subset Series: GSE24285: Genome-wide Analysis Reveals Mecp2-dependent Regulation of MicroRNAs in a Mouse Model of Rett Syndrome (mm8 chromosomal tiling arrays) GSE24286: Genome-wide Analysis Reveals Mecp2-dependent Regulation of MicroRNAs in a Mouse Model of Rett Syndrome (mm8 promoter tiling arrays) GSE24320: Genome-wide Analysis Reveals Mecp2-dependent Regulation of MicroRNAs in a Mouse Model of Rett Syndrome (high-throughput small RNA sequencing) Refer to individual Series