Dataset Information

Shotgun bisulphite sequencing of the Arabidopsis genome reveals DNA methylation patterning.

ABSTRACT: Cytosine DNA methylation is important in regulating gene expression and in silencing transposons and other repetitive sequences. Recent genomic studies in Arabidopsis thaliana have revealed that many endogenous genes are methylated either within their promoters or within their transcribed regions, and that gene methylation is highly correlated with transcription levels. However, plants have different types of methylation controlled by different genetic pathways, and detailed information on the methylation status of each cytosine in any given genome is lacking. To this end, we generated a map at single-base-pair resolution of methylated cytosines for Arabidopsis, by combining bisulphite treatment of genomic DNA with ultra-high-throughput sequencing using the Illumina 1G Genome Analyser and Solexa sequencing technology. This approach, termed BS-Seq, unlike previous microarray-based methods, allows one to sensitively measure cytosine methylation on a genome-wide scale within specific sequence contexts. Here we describe methylation on previously inaccessible components of the genome and analyse the DNA methylation sequence composition and distribution. We also describe the effect of various DNA methylation mutants on genome-wide methylation patterns, and demonstrate that our newly developed library construction and computational methods can be applied to large genomes such as that of mouse.

SUBMITTER: Cokus SJ

PROVIDER: S-EPMC2377394 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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Shotgun bisulphite sequencing of the Arabidopsis genome reveals DNA methylation patterning.

Cokus Shawn J SJ Feng Suhua S Zhang Xiaoyu X Chen Zugen Z Merriman Barry B Haudenschild Christian D CD Pradhan Sriharsa S Nelson Stanley F SF Pellegrini Matteo M Jacobsen Steven E SE

Nature 20080217 7184

Cytosine DNA methylation is important in regulating gene expression and in silencing transposons and other repetitive sequences. Recent genomic studies in Arabidopsis thaliana have revealed that many endogenous genes are methylated either within their promoters or within their transcribed regions, and that gene methylation is highly correlated with transcription levels. However, plants have different types of methylation controlled by different genetic pathways, and detailed information on the m ...[more]

PMID: 18278030

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Project description:BackgroundDNA methylation is a well-studied epigenetic mark that is frequently altered in diseases such as cancer, where specific changes are known to reflect the type and severity of the disease. Therefore, there is a growing interest in assessing the clinical utility of DNA methylation as a biomarker for diagnosing disease and guiding treatment. The development of an accurate loci-specific methylation assay, suitable for use on low-input clinical material, is crucial for advancing DNA methylation biomarkers into a clinical setting. A targeted multiplex bisulphite PCR sequencing approach meets these needs by allowing multiple DNA methylated regions to be interrogated simultaneously in one experiment on limited clinical material.ResultsHere, we provide an updated protocol and recommendations for multiplex bisulphite PCR sequencing (MBPS) assays for target DNA methylation analysis. We describe additional steps to improve performance and reliability: (1) pre-sequencing PCR optimisation which includes assessing the optimal PCR cycling temperature and primer concentration and (2) post-sequencing PCR optimisation to achieve uniform coverage of each amplicon. We use a gradient of methylated controls to demonstrate how PCR bias can be assessed and corrected. Methylated controls also allow assessment of the sensitivity of methylation detection for each amplicon. Here, we show that the MBPS assay can amplify as little as 0.625 ng starting DNA and can detect methylation differences of 1% with a sequencing coverage of 1000 reads. Furthermore, the multiplex bisulphite PCR assay can comprehensively interrogate multiple regions on 1-5 ng of formalin-fixed paraffin-embedded DNA or circulating cell-free DNA.ConclusionsThe MBPS assay is a valuable approach for assessing methylated DNA regions in clinical samples with limited material. The optimisation and additional quality control steps described here improve the performance and reliability of this method, advancing it towards potential clinical applications in biomarker studies.

Project description:DNA methylation is one of the key epigenetic modifications involved in gene regulation. While whole-genome bisulfite sequencing (WGBS) allows the genome-wide quantification of DNA methylation at the single-base pair resolution, the contribution of DNA methylation in disease susceptibility remains to be fully understood. Here, we present a novel Bayesian smoothing approach (called ABBA) to accurately detect differentially methylated regions (DMRs) from WGBS data, and employ ABBA to map DNA methylation changes in disease. ABBA enables the genome-wide modeling of single-base resolution DNA methylation data, automatically adapting to different correlation structures in CpG methylation across the genome without requiring user-defined parameters and accounts for covariates and non-genetic confounding factors. First, we demonstrate the approach by an extensive simulation study and benchmarked ABBA against recently proposed alternative methods. We show the better performance of ABBA across a range of relevant parameters, including sequencing depth, number of replicates and noise level originating from incomplete bisulfite conversion. Second, we generated WGBS data from primary macrophages derived from an experimental rat model of glomerulonephritis and control rats, and employed ABBA to identify DMRs (>1,000 at 5% FDR) genome-wide that were associated with disease susceptibility. Investigation of the DMRs revealed differential DNA methylation localized to the promoter of the Ifitm3 gene and comparisons with existing DMR detection methods shows the enhanced interpretability of the results provided by ABBA. Additional ChIP-seq and RNA-seq analyses in the same experimental system showed differential transcription factor binding at the Ifitm3 promoter by JunD (an established determinant of glomerulonephritis) and consistent differential expression of Ifitm3. Taken together, these data suggest a role for DNA methylation alteration of the Ifitm3 gene in the pathogenesis of glomerulonephritis, and provide a proof of concept of using ABBA for differential methylation analysis of WGBS data.

Project description:BACKGROUND:Comprehensive genome-wide DNA methylation profiling is critical to gain insights into epigenetic reprogramming during development and disease processes. Among the different genome-wide DNA methylation technologies, whole genome bisulphite sequencing (WGBS) is considered the gold standard for assaying genome-wide DNA methylation at single base resolution. However, the high sequencing cost to achieve the optimal depth of coverage limits its application in both basic and clinical research. To achieve 15×?coverage of the human methylome, using WGBS, requires approximately three lanes of 100-bp-paired-end Illumina HiSeq 2500 sequencing. It is important, therefore, for advances in sequencing technologies to be developed to enable cost-effective high-coverage sequencing. RESULTS:In this study, we provide an optimised WGBS methodology, from library preparation to sequencing and data processing, to enable 16-20× genome-wide coverage per single lane of HiSeq X Ten, HCS 3.3.76. To process and analyse the data, we developed a WGBS pipeline (METH10X) that is fast and can call SNPs. We performed WGBS on both high-quality intact DNA and degraded DNA from formalin-fixed paraffin-embedded tissue. First, we compared different library preparation methods on the HiSeq 2500 platform to identify the best method for sequencing on the HiSeq X Ten. Second, we optimised the PhiX and genome spike-ins to achieve higher quality and coverage of WGBS data on the HiSeq X Ten. Third, we performed integrated whole genome sequencing (WGS) and WGBS of the same DNA sample in a single lane of HiSeq X Ten to improve data output. Finally, we compared methylation data from the HiSeq 2500 and HiSeq X Ten and found high concordance (Pearson r?>?0.9×). CONCLUSIONS:Together we provide a systematic, efficient and complete approach to perform and analyse WGBS on the HiSeq X Ten. Our protocol allows for large-scale WGBS studies at reasonable processing time and cost on the HiSeq X Ten platform.

Dataset Information

Shotgun bisulphite sequencing of the Arabidopsis genome reveals DNA methylation patterning.

Publications

Shotgun bisulphite sequencing of the Arabidopsis genome reveals DNA methylation patterning.

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