Methods For DNA Methylation Analysis Research Articles

Methods of DNA methylation analysis

To provide guidance for investigators who are new to the field of DNA methylation analysis. Epigenetics is the study of mitotically heritable alterations in gene expression potential that are not mediated by changes in DNA sequence. Recently, it has become clear that nutrition can affect epigenetic mechanisms, causing long-term changes in gene expression. This review focuses on methods for studying the epigenetic mechanism DNA methylation. Recent advances include improvement in high-throughput methods to obtain quantitative data on locus-specific DNA methylation and development of various approaches to study DNA methylation on a genome-wide scale. No single method of DNA methylation analysis will be appropriate for every application. By understanding the type of information provided by, and the inherent potential for bias and artifact associated with, each method, investigators can select the method most appropriate for their specific research needs.

Genomic profiling of CpG methylation and allelic specificity using quantitative high-throughput mass spectrometry: critical evaluation and improvements

CpG methylation is a key component of the epigenome architecture that is associated with changes in gene expression without a change to the DNA sequence. Since the first reports on deregulation of DNA methylation, in diseases such as cancer, and the initiation of the Human Epigenome Project, an increasing need has arisen for a detailed, high-throughput and quantitative method of analysis to discover and validate normal and aberrant DNA methylation profiles in large sample cohorts. Here we present an improved protocol using base-specific fragmentation and MALDI-TOF mass spectrometry that enables a sensitive and high-throughput method of DNA methylation analysis, quantitative to 5% methylation for each informative CpG residue. We have determined the accuracy, variability and sensitivity of the protocol, implemented critical improvements in experimental design and interpretation of the data and developed a new formula to accurately measure CpG methylation. Key innovations now permit determination of differential and allele-specific methylation, such as in cancer and imprinting. The new protocol is ideally suitable for detailed DNA methylation analysis of multiple genomic regions and large sample cohorts that is critical for comprehensive profiling of normal and diseased human epigenomes.

A Profile of Current Methods for DNA Methylation Analysis

A Profile of Current Methods for DNA Methylation Analysis

Methylation analysis of hMLH1 gene promoter by a bisulfite-sensitive single-strand conformation polymorphism–capillary electrophoresis method

DNA methylation is an important epigenetic modification that alters transcription in those genes containing CpG islands. In this report, a novel DNA methylation analysis method was developed employing bisulfite-single strand conformation polymorphism combined with capillary electrophoresis (bisulfite-SSCP-CE). During the bisulfite treatment of genomic DNA, a high concentration of sodium bisulfite (4.8 mol/L) was preferred in order to shorten reaction time and minimize template degradation. The methylated and unmethylated ssDNA of hMLH1 promoter were simultaneously separated under the optimized CE conditions, including 6% SLPA with 10% glycerol as sieving medium, 25 degrees C as separation temperature and 12 kV as running voltage. The heterogeneous methylation of hMLH1 promoter was identified in 13 of 64 colorectal cancer patients. Moreover, hMLH1 promoter methylation had a significant relationship with protein expression loss and increased with the age of patients. Our results indicated that DNA methylation analysis for a large number of clinical samples would be facilitated by use of the bisulfite-SSCP-CE method.

Polymerase chain reaction-based methods of DNA methylation analysis

DNA methylation is the main epigenetic modification in humans, and changes in methylation patterns play an important role in tumorigenesis. Hypermethylation of normally unmethylated CpG islands in the promoter regions often occurs in important tumor suppressor genes, DNA repair genes, and metastasis inhibitor genes. The changes of methylation status of various gene promoters seem to be a common feature of malignant cells and these changes can occur early in the progression process. Therefore detection of aberrant promoter hypermethylation of cancer-related genes may be useful for cancer diagnosis or detection of cancer recurrence. The purpose of this review is to provide a summary of the most commonly used techniques for the study of DNA methylation. Current scientific literature involving methylation detection methods was reviewed with an emphasis on polymerase chain reaction (PCR)-based detection methods. The current methodologies may be broadly classed into PCR-based methylation assays and non-PCR-based methylation assays. The problems and advantages of the different methods for detecting aberrant methylation are discussed. As the number of genes known to be hypermethylated in cancer is growing, the detection of aberrant promoter region methylation will be a promising approach for using DNA-based markers for the early detection of human cancers. Many techniques, especially PCR-based methylation assay techniques, make it practical to use these new methylation biomarkers in early cancer diagnosis.

DHPLC-Based Method for DNA Methylation Analysis of Differential Methylated Regions from Imprinted Genes

The bisulfite genomic sequencing method is one of the most widely used techniques for methylation analysis in heterogeneous unbiased PCR, amplifying for both methylated and unmethylated alleles simultaneously. However, it requires labor-intensive and time-consuming cloning and sequencing steps. In the current study, we used a denaturing high-performance liquid chromatography (DHPLC) procedure in a complementary way with the bisulfite genomic sequencing to analyze the methylation of differentially methylated regions (DMRs) of imprinted genes. We showed reliable and reproducible results in distinguishing overall methylation profiles of DMRs regions of human SNRPN, H19, MEST/PEG1, LIT1, IGF2, TSSC5, WT1 antisense, and mouse H19, Mest/Peg1, Igf2R imprinted genes. These DHPLC profiles were in accordance with bisulfite genomic sequencing data and may serve as a type of "fingerprint," revealing the overall methylation status of DMRs associated with sample heterogeneity. We conclude that DHPLC analysis could be used to increase the throughput efficiency of methylation pattern analysis of imprinted genes after the bisulfite conversion of genomic DNA and unbiased PCR amplification.