In silico enhanced restriction enzyme based methylation analysis of the human glioblastoma genome
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ABSTRACT:
ORGANISM(S): Homo sapiens
SUBMITTER: Anh Tran
PROVIDER: E-GEOD-19363 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:Genome wide methylation profiling of gliomas is likely to provide important clues to improving treatment outcomes. Restriction enzyme based approaches have been widely utilized for methylation profiling of cancer genomes and will continue to have importance in combination with higher density microarrays. With the availability of the human genome sequence and microarray probe sequences, these approaches can be readily characterized and optimized via in silico modeling. We adapted the previously described HpaII/MspI based Methylation Sensitive Restriction Enzyme (MSRE) assay for use with two-color Agilent 244K CpG island microarrays. In this assay, fragmented genomic DNA is digested in separate reactions with isoschizomeric HpaII (methylation-sensitive) and MspI (methylation-insensitive) restriction enzymes. Using in silico hybridization, we found that genomic fragmentation with BfaI was superior to MseI, providing a maximum effective coverage of 22,362 CpG islands in the human genome. In addition, we confirmed the presence of an internal control group of fragments lacking HpaII/MspI sites which enable separation of methylated and unmethylated fragments. We used this method on genomic DNA isolated from normal brain, U87MG cells, and a glioblastoma patient tumor sample and confirmed selected differentially methylated CpG islands using bisulfite sequencing. Along with additional validation points, we performed a receiver operating characteristics (ROC) analysis to determine the optimal threshold (p ≤ 0.001). Based on this threshold, we identified ~2400 CpG islands common to all three samples and 145 CpG islands unique to glioblastoma. These data provide general guidance to individuals seeking to maximize effective coverage using restriction enzyme based methylation profiling approaches.
2009-12-08 | GSE19363 | GEO
Project description:This data was generated by ENCODE. If you have questions about the data, contact the submitting laboratory directly (Florencia Pauli mailto:fpauli@hudsonalpha.org). If you have questions about the Genome Browser track associated with this data, contact ENCODE (mailto:genome@soe.ucsc.edu). This track shows average methylation status in CpG islands. In general, methylation of CpG sites within a promoter causes silencing of the gene associated with that promoter For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf CpG regions were assayed via Methyl-seq, a method developed in the Myers laboratory to measure the methylation status at CpGs throughout the genome. It combines DNA digestion by a methyl-sensitive enzyme HpaII and its methyl-insensitive isoschizomer MspI with the Illumina DNA sequencing platform. The method was first applied in a collaboration with the laboratory of Dr. Julie Baker at Stanford University to study methylation and gene expression changes that occur in human embryonic stem cells before and after differentiation to definitive endoderm. A paper describing the results as well as the method has been submitted for publication [1]. This study profiled genomic DNA and mRNA samples derived from two human embryonic stem cell lines: H9 and BG02. These cells were differentiated into definitive endoderm, embryoid bodies, embryoid body-derived cells, and AFP+ (alpha-fetoprotein positive) hepatocytes. These in vitro samples were profiled with Methyl-seq and compared them with normal tissue samples from 11-week and 24-week fetal liver and adult liver. Methyl-seq assays more than 250,000 methyl-sensitive restriction enzyme cleavage sites, representing more than 90,000 genomic regions. These regions include 35,528 annotated CpG islands, while the remaining 55,084 non-CpG island regions are distributed across the genome in promoters, genes, and intergenic regions. Sequence tags present in MspI libraries but not in HpaII libraries are derived from methylated regions. Conversely, sequence tags that occur in HpaII libraries come from at least partially unmethylated regions. In vitro differentiation: Definitive endoderm precursor cells were generated from H9 hES cells by treating them with activin A. Embryoid bodies (EBs) were generated by growing undifferentitated H9 and BG02 hESCs in suspension. EB-derived cells were obtained by plating clumps of the cells from the EBs. AFP+ fetal hepatocytes were derived from EBs by plating EB cells with FgF, followed by fluorescence activated cell sorting (FACS) to isolate cells expressing the green fluorescent protein (GFP) reporter gene driven from the AFP promoter. Isolation of genomic DNA: Genomic DNA is isolated from biological replicates of each cell line by using the QIAGEN DNeasy Blood & Tissue Kit according to the instructions provided by the manufacturer. DNA concentrations and a level of quality of each preparation is determined by UV absorbance. HpaII and MspI digestions: Cleavage of DNA by restriction endonuclease HpaII is prevented by the presence of a 5-methyl group at the internal C residue of its recognition sequence CCGG. MspI, an isoschizomer of HpaII, cleaves DNA irrespective of the presence of a methyl group at this position. For the MspI library, 5 µg genomic DNA was digested in a 100 µl reaction with 1X NEB Buffer2 and 20 units MspI restriction enzyme and incubated for 18 hr at 37°C. For the HpaII library, 5 µg genomic DNA was digested in a 100 µl reaction with 1X NEB Buffer1 and 20 units HpaII restriction enzyme and incubated for 18 hr at 37°C. Note that in subsequent versions of the Methyl-seq protocol, which will be described later, much lower amounts of genomic DNA were used (1 µg and potentially lower). DNA library construction and sequencing: High-throughput sequencing libraries were generated from DNA fragments of the HpaII or MspI digested genomic DNA according to the protocol posted at the website: http://myers.hudsonalpha.org/content/protocols.html. This approach was recently modified by removing the first PCR amplification step, just prior to the gel electrophoresis size-selection step, which was found to reduce a fragment-size bias in the sequencing libraries. These libraries were sequenced with an Illumina Genome Analyzer (GA2) according to the manufacturer's recommendations. Data analysis: For this analyis, reads that align to human genome sequence version hg19 and contain the 5'-CGG-3' HpaII-cut signature on their 5' end were used. These aligned sequence reads were mapped to CCGG sites predicted in silico on hg19. Sites with four or more Msp1 tags occurring in either the forward or reverse direction were retained for analysis. These "assayable" sites were then grouped with neighboring sites that are within 35-75 bp of each other. Thus, a "region" can be comprised of between 2 and 18 digestion sites that are each within 35-75 bp of another site. Methylated and non-methylated calls were made by using HpaII tag data from all assayable cut sites. For each site across each region, the larger of either the forward read count or reverse read count was used. Regions that have an average of 0 or 1 read per cut site are called methylated, and regions with more than one sequence read per site are called unmethylated.
2012-10-03 | E-GEOD-41304 | biostudies-arrayexpress
Project description:DNA methylation is a major epigenetic modification important for regulating gene expression and suppressing spurious transcription. Most methods to scan the genome in different tissues for differentially methylated sites have focused on the methylation of CpGs in CpG islands, which are concentrations of CpGs often associated with gene promoters. Here, we use a methylation-profiling strategy that is predominantly responsive to methylation differences outside of CpG islands. The method compares the yield from two samples of size-selected fragments generated by a methylation-sensitive restriction enzyme. We profile eight different normal tissues relative to spleen for each of two human donors using a custom array of genomic clones covering the euchromatic portion of human chromosome 1 and representing 8% of the human genome. We observe gross regional differences in methylation states across chromosome 1 between tissues from the same individual, with the most striking differences detected in the comparison of cerebellum and spleen. Profiles of the same tissue from different donors are strikingly similar, as are the profiles of different lobes of the brain. Using DNMT1-deficient cells as a test case, we show that much finer-scale fluctuations in relative fragment yield can be detected when the methylation profiling is performed using a high-resolution oligomer array for chromosome 1. The varied patterns of methylation differences detected between tissues by this method reinforce the potential functional significance of regional differences in methylation levels outside of CpG islands. DNA digested with methylation-sensitive restriction enzyme (HpaII) and size-selected. Eleven human tissue types studied, most from two human individuals, each in triplicate, and one cell line. Two control hybrizations consisting of DNA prepared independently from the same tissue.
2010-05-18 | E-GEOD-12925 | biostudies-arrayexpress
Project description:5-hydroxymethylcytosine (5-hmC), a derivative of 5-methylcytosine (5-mC), is abundant in the brain for unknown reasons. We mapped the genomic distribution of 5-hmC and 5-mC in human and mouse tissues using glucosylation of 5-hmC coupled with restriction enzyme digestion, and interrogation on microarrays. We detected 5-hmC enrichment in genes with synapse-related functions in the brain. We also identified significant, tissue-specific differential distributions of these DNA modifications at the exon-intron boundary, in both human and mouse. This boundary change was mainly due to 5-hmC in the brain, but due to 5-mC in non-neural contexts. This pattern was replicated in multiple independent datasets, and the brain-specific change in 5-hmC was validated using single-molecule sequencing. Moreover, in the brain, constitutive exons contained higher levels of 5-hmC, relative to alternatively-spliced exons. Our study suggests a novel role for 5-hmC in RNA splicing and synaptic function in the brain The M-NM-2-glucosyltransferase (BGT) enzyme transfers a glucose molecule specifically to the hydroxymethyl group of 5-hmC, thus rendering it resistant to digestion by the methylation insensitive MspI enzyme at the ChmCGG target site; 5-hmC is thus detected by differential resistance to MspI-digestion with and without glucosylation of genomic DNA (gDNA). HpaII (targets the same site, CCGG) cannot cut CmCGG or ChmCGG, and conceptually its difference with MspI digestion is a measure of both 5-mC and 5-hmC. Subtraction of 5-hmC from the HpaII-based estimate therefore measures 5-mC. These estimates were measured on respective Affymetrix whole-genome tiling arrays (2.0 R ) MspI - APRIL_fc1.ch02_coverage.bed Undigested DNA - APRIL_fc1.ch01_coverage.bed GluMspI - APRIL_fc1.ch04_coverage_NONTARGET.bed GluMspI - APRIL_fc1.ch04_coverage.bed MspI - APRIL_fc1.ch02_coverage_NONTARGET.bed Undigested DNA - APRIL_fc1.ch01_coverage_NONTARGET.bed MspI - MARCH_fc1.ch02_coverage_NONTARGET.bed Undigested DNA - MARCH_fc1.ch01_coverage_NONTARGET.bed GluMspI - MARCH_fc1.ch04_coverage_NONTARGET.bed GluMspI - MARCH_fc1.ch04_coverage.bed MspI - MARCH_fc1.ch02_coverage.bed Undigested DNA - MARCH_fc1.ch01_coverage.bed MspI - MAY_fc1.ch02_coverage.bed GluMspI - MAY_fc1.ch04_coverage_NONTARGET.bed GluMspI - MAY_fc1.ch04_coverage.bed Undigested DNA - MAY_fc1.ch01_coverage.bed MspI - MAY_fc1.ch02_coverage_NONTARGET.bed Undigested DNA - MAY_fc1.ch01_coverage_NONTARGET.bed
2012-08-24 | E-GEOD-40158 | biostudies-arrayexpress
Project description:Background: To perform epigenome-wide association studies in human disease, assays need to be comprehensive and quantitative while remaining cost-effective. We explored how the strengths of prior tag-based cytosine methylation assays based on massively-parallel sequencing can be maximised analytically. Results: We find that the use of the EcoP15I restriction enzyme to generate long tags and the normalisation of methylation-sensitive by methylation-insensitive restriction enzyme representations greatly improve assay performance. When exploring sources of bias, we find that the length of the restriction fragment has moderate effects on EcoP15I digestion, while base composition exerts minimal effects. We detail the analytical workflow that maximises the quantitative capabilities of this modified assay. Also revealed are polymorphic sequences in the genome that could confound microarray, bisulphite sequencing or mass spectrometry-based assays, and a position effect causing hypomethylation of transposable elements near gene promoters. Conclusions: The new combined assay, referred to as HELP-tagging, interrogates over 1.8 million loci in the human genome quantitatively with a single lane of Illumina sequencing. When the goal is to study not only CG-dense sequence but also the CG-depleted majority of the genome, this assay system should be suitable. Three MspI reference, one HpaII test
2010-04-12 | E-GEOD-19937 | biostudies-arrayexpress
Project description:Intergenerational genomic DNA methylation patterns in mouse hybrid strains Reduced representation bisulfite sequencing from mouse liver, using MspI restriction enzyme, and selecting ~100-300bp size fraction.
2013-12-30 | E-GEOD-53714 | biostudies-arrayexpress
Project description:CG Methylation of Col, Van and reciprocal hybrids using HpaII and MspI digestion followed by bioprime random labeling, and hybridization to AtTILE1 forward array. Study on constitutive and ploymorphic CG methylation between arabidopsis thaliana accessions Col-0 and Van-0. Study on the inheritance of CG methylation in reciprocal hybrids. Keywords: genomic hybridization
2008-04-11 | GSE8890 | GEO
Project description:The marrow microenvironment contributes to the pathogenesis of ineffective hematopoiesis in Myelodysplastic Syndromes (MDS). Since mutations and cytogenetic alterations are generally not present in marrow stromal cells, we hypothesized that epigenetic alterations may be responsible for altered stroma functionin MDS. Global DNA methylation of MDS marrow-derived stroma was analyzed by HELP assay and compared to healthy controls. MDS stroma showed aberrant hypermethylation that preferentially occurred outside of CpG islands and involved important signaling pathways.Comparison with stroma derived from 5-Azacytidine (5-Aza) treated MDS patients revealed abrogation of aberrant methylation in treated samples. Integrative expression analysis revealed that the WNT pathway was epigenetically dysregulated in MDS stroma, and the WNT antagonists FRZB and SFRP1 were aberrantly hypermethylated and underexpressed. These epigenetic changes were validated ina co-culture model of stroma and leukemic cells and in an independent set of MDS samples. Importantly, 5-Aza treatment of MDS stroma enhanced hematopoietic activity and erythroid differentiationfrom co-cultured healthy CD34+ cells. These results reveal widespread aberrant epigenetic changes in the MDS marrow microenvironment and demonstrate that DNA methyl transferase inhibitors alter the epigenomic profiles of stromal cells, potentiallycontributing to theirtherapeutic efficacy. The study population consisted of 6 MDS patients and 3 healthy controls. Individual HpaII restriction digest profiles were compared to an internal MspI digest control, to yield differentially methylated fragments for every sample.
2015-05-20 | E-GEOD-60233 | biostudies-arrayexpress
Project description:In lung cancer, hypermethylation of specific gene promoters has been found during the progressive carcinogenesis. The identification of common methylation events will aid in the understanding of molecular events during neoplastic transformation and help develop biomarkers for cancer with high predictive and diagnostic value. To explore common methylation events on a genome-wide scale in lung cancer, we analyzed the methylation profiles of paired NSCLC tumor and far adjacent non-tumor samples using the HELP-microarray assay, which yields information on 1.2 million fragments throughout the genome. In this study, 24 pairs of tumor and adjacent non-tumor samples were analyzed using the HELP assay. At p = 5E-6, we identified 26,138 differentially methylated fragments (corresponding to 2 CpG sites each) in tumor versus non-tumor. The overall trend was consistent with genome-wide hypomethylation and locus specific hypermethylation (localized to CG-island containing promoters). We could identify both known and novel regions of the genome as well as specific gene-promoters that are hypermethylated in tumor versus non-tumor. The HELPassay: HpaII tiny fragment enrichment by ligation-mediated polymerase chain reaction [PCR] assay 24 pairs of NSCLC subjects, tumor and paired non-tumor samples from each subject were analyzed. Individual HpaII restriction digest profiles were compared to an internal MspI digest control, to yield differentially methylated fragments for every sample. Samples were compared intra-subject between tumor and adjacent non-tumor for these differential methylation profiles and the overall significant changes across 24 subjects were identified.
2012-03-31 | E-GEOD-35520 | biostudies-arrayexpress
Project description:We describe a simple method, Digital Restriction Enzyme Analysis of Methylation (DREAM), based on sequential DNA digestion with a pair of methylation-blocked and methylation-tolerant neoschizomeric restriction enzymes SmaI/XmaI followed by end repair and ultra-deep sequencing. DREAM provides information on 160,000 unique CpG sites of which 39,000 are in CpG islands, and 33,000 are at transcription start sites (-1 kb to +1 kb) of 13,139 RefSeq genes. We compared DNA methylation values in white blood cells from 4 healthy individuals and found them to be remarkably uniform. Interindividual differences >30% were observed only at 227 of 28,331 (0.8%) of autosomal CCCGGG sites covered by 100+ sequencing reads. Similarly, differences at only 59 sites were observed between the cord and adult blood. Conserved methylation patterns in healthy blood cells contrasted with extensive changes affecting 18-40% of CpG sites in leukemia. The method is cost effective, quantitative (r2=0.93 when compared to bisulfite pyrosequencing), reproducible (r2=0.997), and can detect differences >25% with false positive rate <0.001. Accurate analysis of changes in DNA methylation will be useful in quantifying epigenetic effects of environment and nutrition, correlating developmental epigenetic variation with phenotypes, understanding epigenetics of cancer and chronic diseases, measuring the effects of drugs on DNA methylation or deriving new biological insights into mammalian genomes. Digital restriction enzyme analysis of methylation (DREAM) was performed to determine the DNA methylation profiles of healthy white blood cells from cord blood and adult blood, acute myeloid leukemia bone marrow, and two leukemia cell lines (HEL and K562). In this approach, genomic DNA is sequentially cut at CCCGGG sites with the methylation-sensitive enzyme SmaI (blunt ends) and its methylation-tolerant neoschizomer XmaI (5'CCGG overhangs), creating different end sequences that represent methylation status of the CCCGGG sites. These end sequences are analyzed by next-generation sequencing, and thereafter the methylation status at individual CCCGGG sites across the genome can be determined.
2012-11-08 | E-GEOD-39787 | biostudies-arrayexpress