Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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âSame Differenceâ: Comprehensive evaluation of four DNA methylation measurement platforms

ABSTRACT: DNA methylation in CpG context is fundamental to the epigenetic regulation of gene expression in high eukaryotes. Disorganization of methylation status is implicated in many diseases, cellular differentiation, imprinting, and other biological processes. Techniques that enrich for biologically relevant CpG-rich genomic regions are desired since, depending on the size of an oragnism's methylome, the depth of sequencing required to cover all CpGs can be prohibitively expensive. Currently, restriction-enzyme based Reduced Representation Bisulfite Sequencing and its modified protocols are widely used to study methylation differences. Recently, Agilent Technologies and Roche NimbleGen have aimed to both reduce sequencing costs and capture CpGs of known biological relevance by marketing in-solution custom-capture hybridization platforms. These three methods target approximately 10-13% of the human methylome. For each platform - restriction-enzyme based enhanced reduced representation (ERRBS), capture based Agilent SureSelect Methyl-seq (SSMethylseq), and capture based Roche NimbleGen SeqCap Epi CpGiant (CpGiant) - we used human lung fibroblast cell line IMR90 DNA to make libraries according to each protocol and sequenced to equivalent depth. Overall, SSMethylSeq and CpGiant covered >95% of their designed capture regions whereas ERRBS covered 70% of its expected MspI regions. Methylation levels were concordant across the platforms. The concordance of annotations of CpG units for genomic features, displayed roughly the same proportions of genomic features. SSMethylSeq and CpGiant are most similar and cover marginally more annotated regions than ERRBS. However, the number of CpG units shared by all methods was low, ~26% of any platform. We conclude that captured based methods are largely consistent in terms of covered CpG loci although ERRBS provides comparable data at a significantly reduced price. Furthermore, library preparation for ERRBS can be performed with as little as 75ngs of starting material, whereas micrograms are needed for the capture hybridization techniques. Libraries were made from human lung fibroblast cell line IMR90 DNA for each protocol of ERRBS, Agilent SureSelect Methyl-seq, Roche NimbleGen SeqCap Epi CpGiant, and WGBS, then sequenced as paired-end 100bp on an Illumina HiSeq 2500.

ORGANISM(S): Homo sapiens

SUBMITTER: Thadeous Kacmarczyk

PROVIDER: E-GEOD-83595 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Pathologic differentiation of tissue of origin in tumors found in the lung can be challenging, with differentiation of mesothelioma and lung adenocarcinoma emblematic of this problem. Indeed, proper classification is essential for determination of treatment regimen for these diseases, making accurate and early diagnosis critical. Here we investigate the potential of epigenetic profiles of lung adenocarcinoma, mesothelioma, and non-malignant pulmonary tissues (n=285) as differentiation markers in an analysis of DNA methylation at 1413 autosomal CpG loci associated with 773 cancer-related genes. Using an unsupervised recursively-partitioned mixture modeling technique for all samples, the derived methylation profile classes were significantly associated with sample type (P < 0.0001). In a similar analysis restricted to tumors, methylation profile classes significantly predicted tumor type (P < 0.0001). Random forests classification of CpG methylation of tumors - which splits the data into training and test sets - accurately differentiated MPM from lung adenocarcinoma over 99% of the time (P < 0.0001). In a locus-by-locus comparison of CpG methylation between tumor types, 1266 CpG loci had significantly different methylation between tumors following correction for multiple comparisons (Q < 0.05); 61% had higher methylation in adenocarcinoma. Using the CpG loci with significant differential methylation in a pathways analysis revealed significant enrichment of methylated gene-loci in Cell Cycle Regulation, DNA Damage Response, PTEN Signaling, and Apoptosis Signaling pathways in lung adenocarcinoma when compared to mesothelioma. Methylation-profile-based differentiation of lung adenocarcinoma and mesothelioma is highly accurate, informs on the distinct etiologies of these diseases, and holds promise for clinical application. Mesotheliomas (n=158) and grossly non-tumorigenic parietal pleura (n=18) were obtained following surgical resection at Brigham and Womenâ??s Hospital through the International Mesothelioma Program from a pilot study conducted in 2002 (n=70) and an incident case series beginning in 2005 (n=88) with a participation rate of 85%. We used biopsy specimens from patients treated for NSCLC at the Massachusetts General Hospital from 1992 â?? 1996 (18) including lung adenocarcinomas (n=57) and non-malignant pulmonary tissues (n=48) (of which 22 (39%) were taken from the adenocarcinoma patients) (18). Additional normal lung tissues were obtained from the National Disease Research Interchange from donors free of lung malignancy (n=4).

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âSame Differenceâ: Comprehensive evaluation of four DNA methylation measurement platforms

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âSame Differenceâ: Comprehensive evaluation of four DNA methylation measurement platforms