Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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MeCP2 binds to 5hmC enriched within active genes and accessible chromatin in the nervous system

ABSTRACT: The high level of 5-hydroxymethylcytosine (5hmC) present in neuronal genomes suggests that mechanisms interpreting 5hmC in the central nervous system (CNS) may differ from those present in embryonic stem cells. Here we present quantitative, genome-wide analysis of 5hmC, 5- methylcytosine (5mC) and gene expression in differentiated CNS cell types in vivo. We report that 5hmC is enriched in active genes, and that surprisingly strong depletion of 5mC is observed over these regions. The contribution of these epigenetic marks to gene expression depends critically on cell type. We identify methyl-CpG binding protein 2 (MeCP2) as the major 5hmC binding protein in the brain, and demonstrate that MeCP2 binds 5hmC and 5mC containing DNA with similar high affinities. The Rett Syndromecausing mutation R133C preferentially inhibits 5hmC binding. These findings support a model in which 5hmC and MeCP2 constitute a cell specific epigenetic mechanism for regulation of chromatin structure and gene expression. Isolation and sorting was performed as described in (Kriaucionis and Heintz, 2009). Briefly, cerebella were dissected as described above and homogenized in homogenization medium (0.25 M sucrose, 150 mM KCl, 5 mM MgCl2, 20 mM Tricine pH 7.8, 0.15 mM spermine, 0.5 mM spermidine, EDTA-free protease inhibitor cocktail (Roche) using loose (A) and tight (B) glassglass dounce.Homogenate was supplemented with 50% iodixanol (OptiPrep, Axis-Shield, Scotland), 150 mM KCl, 5 mM MgCl2, 20 mM Tricine pH 7.8; and laid on a 29% iodixanol cushion. GC nuclei from WT and Mecp2-null mice were sorted by selecting a specific FSC/SSC population identified from GC EGFP+ mice. We observed that this FSC/SSC gated population in GC EGFP+ animals resulted >92% of the sorted nuclei being EGFP positive. Thus, the gate selected allows us to enrich the sample from 65-70% to 92-96% on GC cells. 5hmC was pulled down as described (Song et al., 2010). After purification DNA was amplified as described in TruSeq DNA Sample kit. 1-0.5 M-NM-

ORGANISM(S): Mus musculus

SUBMITTER: Marian Mellen

PROVIDER: E-GEOD-42880 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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MeCP2 binds to 5hmC enriched within active genes and accessible chromatin in the nervous system.

Mellén Marian M Ayata Pinar P Dewell Scott S Kriaucionis Skirmantas S Heintz Nathaniel N

Cell 20121201 7

The high level of 5-hydroxymethylcytosine (5hmC) present in neuronal genomes suggests that mechanisms interpreting 5hmC in the CNS may differ from those present in embryonic stem cells. Here, we present quantitative, genome-wide analysis of 5hmC, 5-methylcytosine (5mC), and gene expression in differentiated CNS cell types in vivo. We report that 5hmC is enriched in active genes and that, surprisingly, strong depletion of 5mC is observed over these regions. The contribution of these epigenetic ma ...[more]

PMID: 23260135

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Project description:Samples were purchased from Clontech as mRNA. Hybridization material was generated through a random-priming amplification procedure (RP-AMP) using primers with a random sequence at the 3' end and a fixed motif at the 5' end. shDNP256 (first strand synthesis): 5'- TAG ATG CTG TTG NNN NNN NNN -3' shT7N9 (second strand synthesis): 5'- ACT ATA GGG AGA NNN NNN NNN -3' 1.5 g of mRNA was reverse-transcribed with Superscript II and the DP256 random primer for 20 minutes at 42 C (10 mM DTT, 50 mM Tris-HCl pH 8.3, 75 mM KCl, 8 mM MgCl2, 0.5 mM dNTPs, 5 U/ l Superscript II). The RNA was degraded with the addition of 20 l volume of 0.5N sodium hydroxide and 0.25 M EDTA for 20 minutes at 65 C. The single stranded cDNA was purified using a commercial kit (Qiagen Qiaquick). The resulting product of single stranded cDNA was placed in its entirety in a second strand reaction. Second strand synthesis reactions utilized shT7N9 random primer and the Klenow fragment of DNA polymerase utilizing standard reaction conditions (37 C for 60 minutes, 0.2 mM DTT, 2.1 mM Tris-HCl pH 7.9, 2.1 mM MgCl2, 10.7 mM NaCl, 1.07 mM dNTPs, 0.1U/ l Klenow), followed by another Qiaquick purification. Multiple polymerase chain reactions were run using 0.15 g of double stranded DNA and standard reaction conditions. Amplification was achieved using 10 cycles of PCR with the DP256 and T7 primers (20 mM Tris-HCl pH 8.4, 50 mM KCl, 0.01 mM dNTPs, 1.5 mM MgCl2, 0.01 U/ l Taq Polymerase) DP256: 5'- GTT CGA GAC CTC TAG ATG CTG TTG -3' T7: 5'- AA TTA ATA CGA CTC ACT ATA GGG AGA -3' followed by Qiaquick purification. Further amplification was achieved using in vitro transcription reactions with X0.5 g dsDNA and T7 RNA Polymerase (7.5 mM DTT, 40 mM Tris-HCl pH 7.5, 14.25 mM MgCl2, 10 mM NaCl, 2 mM Spermidine, 125 U/ml RNAguard, 2.5 mM dNTPs, 15 U/ml IPPase, 25kU/ml T7 Polymerase) for 16 hours at 42 C. The cRNA was purified (RNeasy) and reverse transcribed using Superscript and random 9-mers and amino-allyl dUTP (42 C for 20 minutes, 10 mM DTT, 50mM Tris-HCl pH 8.3, 75 mM KCl, 8 mM MgCl2, 0.5 mM dNTPs, 0.5 mM aa-dUTP, 5 U/ l Superscript II). The cDNA for each channel was covalently coupled separately with Cy5 and Cy3 monoreactive fluors, respectively, in 1M sodium bicarbonate, pH 9.0, followed by quenching with 4.0 M hydroxylamine. The Cy5 and Cy3 labelled cDNAs were purified with a QIAquick PCR purification kit and the percentage dye incorporation and total cDNA yield was determined spectrophotometrically. Cy5 and Cy3 labelled cDNAs were combined and added to 2 mls 30% formamide with Herring Sperm DNA for hybridization to the microarray. Further details can be found in Castle et al., Genome Biol 2003;4(10):R66, http://genomebiology.com/2003/4/10/R66 , Roberts CJ et al., Science 2000, 287:873-880, and Schadt, Edwards, et al., unpublished. Normalization of single channel data is described in Ying, et al., "Identification of Chromosomal Regions Containing Transcribed Sequences Using Microarrays and Computational Methods" , 2003 Proceedings of the American Statistical Association, Biopharmaceutical Section [CD-ROM], Alexandria, VA: American Statistical Association, 2003. Briefly, an invariant set of probes was selected based on their intensity ranks. Then, a LOESS regression model was fit for Cy5 vs. Cy3 intensities for all probes in the invariant set. Finally, for all probes on the array the Cy5 intensities were normalized to the corresponding Cy3 intensities using prediction values from the regression model. Note that the normalized intensity values given here were used for all analyses reported in the accompanying paper. The ratio values reported here were not used for the analysis described in the manuscript and are not calculated from the normalized intensity values given below. Keywords: other

Project description:During differentiation of embryonic stem cells, chromatin reorganizes to establish cell type specific expression programs. Here, we have dissected the linkages between DNA methylation (5mC), hydroxymethylation (5hmC), nucleosome repositioning and binding of the transcription factor CTCF during this process. By integrating MNase-seq and ChIP-seq experiments in mouse embryonic stem cells (ESC) and their differentiated counterparts with biophysical modeling, we find that the interplay between these factors depends on their large-scale genomic context. The mostly unmethylated CpG islands have a reduced nucleosome occupancy and are enriched in cell type-independent binding sites for CTCF. The few remaining methylated CpG dinucleotides are preferentially associated with nucleosomes. In contrast, outside of CpG islands most CpGs are methylated and their average density oscillates so that it is highest in the linker region between nucleosomes. Outside CpG islands binding of TET1, an enzyme that converts 5mC to 5hmC, is associated with labile, MNase-sensitive nucleosomes. Such nucleosomes are poised for eviction in ESCs and become stably bound in differentiated cells where the level of TET1 and 5hmCs goes down. In particular, this has a dramatic effect at variable CTCF sites enriched outside CpG islands, that are occupied by CTCF in ESCs but loose CTCF during differentiation. To rationalize this cell type dependent targeting of CTCF binding in competition with the histone octamer, we have developed a quantitative biophysical model, which allowed predicting differences in CTCF binding due to TET1/5hmC/5mC-dependent nucleosome repositioning. MNase-seq experiments for analysis of mononucleosomes were conducted as described previously (Teif et al. Nature Struct. Mol. Biol., 2012). In addition, a dinucleosome fraction also was gel purified and sequenced. Briefly, embryonic stem cells from 129P2/Ola mice were cultured in ESGRO complete medium (Millipore), harvested and resuspended in low salt buffer (10 mM Hepes, pH 8, 10 mM KCl, 0.5 mM DTT) at 4 M-BM-0C. After disruption of the cells with a douncer the nuclei were collected by centrifugation and washed once with the MNase Buffer (10 mM TrisM-bM-^@M-^SHCl, pH 7.5, 10 mM CaCl2), resuspended in the MNase Buffer and digested with 0.5 units MNase per microliter (Fermentas) and incubation for 6M-bM-^@M-^S11 minutes at 37 M-BM-0C. The MNase digestion was stopped by putting the samples on ice and adding EDTA to a concentration of 10 mM. After digestion with 0.1 M-BM-5g M-BM-5lM-bM-^@M-^S1 RNase A (Fermentas) and removal of protein by phenol and chloroform extraction, the DNA was ethanol precipitated and the resulting DNA pellet was dissolved in H2O. DNA fragments corresponding to mononucleosomes or dinucleosomes were separated on a 2 % agarose gel using an E-Gel electrophoresis system (Life Technologies). The libraries for sequencing were prepared according to the standard Illumina protocol. High-throughput paired-end sequencing of at least 50 bp read length was performed on the Illumina HiSeq 2000 platform at the DKFZ sequencing core facility in Heidelberg, Germany. We obtained about 150 million nucleosome positions per sequencing reaction. ChIP-seq experiments were conducted as described previously (Teif et al. 2012). For each sample, 1 x 106 cells were cross-linked with 1% PFA and cell nuclei were prepared using a swelling buffer (25 mM Hepes, pH 7.8, 1 mM MgCl2, 10 mM KCl, 0.1% NP-40, 1 mM DTT). Chromatin was sheared to mononucleosomal fragments. After IgG preclearance the sheared chromatin was incubated with 4 M-BM-5g of either H3K9me3 (Abcam ab8898) or H3K4me3 (Abcam ab8580) antibody over night. After washes with sonication (10 mM TrisM-bM-^@M-^SHCl, pH 8.0, 200 mM NaCl, 1 mM EDTA, 0.5% N-lauroylsarcosine, 0.1% NaM-bM-^@M-^Sdeoxycholate), high-salt-buffer (50 mM Hepes pH 7.9, 500 mM NaCl, 1mM EDTA, 1% Triton X-100, 0.1% NaM-bM-^@M-^Sdeoxycholate, 0.1% SDS), lithium buffer (20 mM TrisM-bM-^@M-^SHCl pH 8.0, 1 mM EDTA, 250 mM LiCl, 0.5% NP-40, 0.5% NaM-bM-^@M-^Sdeoxycholate) and 10 mM TrisM-bM-^@M-^SHCl, chromatin was eluted from the protein G magnetic beads and the crosslink was reversed over night. After RNase A and proteinase K digestion, DNA was purified and cloned in a barcoded sequencing library for the Illumina HiSeq 2000 sequencing platform (single reads of 50 bp length).

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MeCP2 binds to 5hmC enriched within active genes and accessible chromatin in the nervous system

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MeCP2 binds to 5hmC enriched within active genes and accessible chromatin in the nervous system.

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