ABSTRACT
According to the tissue-specific methylation database (doi: 10.1016/j.gene.2014.09.060), methylation at CpG locus cg03096975 in EML2 has been preliminarily proven to be specific to brain tissue. In this study, we enlarged sample size and developed a technique for identifying brain tissue in aged samples. Combined Bisulfite Restriction Analysis-for EML2 (COBRA-EML2) technique was established and validated in various organ samples obtained from 108 autopsies. In addition, this technique was also tested for its reliability, minimal DNA concentration detected, and use in aged samples and in samples obtained from specific brain compartments and spinal cord. COBRA-EML2 displayed 100% sensitivity and specificity for distinguishing brain tissue from other tissues, showed high reliability, was capable of detecting minimal DNA concentration (0.015ng/µl), could be used for identifying brain tissue in aged samples. In summary, COBRA-EML2 is a technique to identify brain tissue. This analysis is useful in criminal cases since it can identify the vital organ tissues from small samples acquired from criminal scenes. The results from this analysis can be counted as a medical and forensic marker supporting criminal investigations, and as one of the evidences in court rulings.
Subject(s)
Brain , DNA Methylation , Organ Specificity , Sequence Analysis, DNA/methods , Sulfites/chemistry , CpG Islands/genetics , Female , Genetic Markers , Humans , Male , Microtubule-Associated Proteins/genetics , Reproducibility of Results , Time FactorsABSTRACT
Adenocarcinoma is a type of cancer that occurs in the glandular cells throughout the body. There are several metastatic adenocarcinoma of unknown primary origin. Currently, there is no highly effective method to differentiate pancreatic ductal adenocarcinoma (PDAC) from other adenocarcinomas. Here, we identified pancreas tissue by site-specific methylation at FRY and found that it can also detect PDAC. The establishment of Combined Bisulphite Restriction Analysis (COBRA) and quantitative real-time PCR techniques of FRY revealed FRY hypermethylation in 21 out of 24 normal pancreatic tissue samples, whereas all other normal tissue samples from thirteen other organs (80 samples) remained totally unmethylated. Similarly in application to PDAC, this marker effectively indicated 25 PDAC among 151 other common adenocarcinomas with values of 100%, 98.7%, 92.6%, and 100% in sensitivity, specificity, positive predictive value and negative predictive value, respectively. In summary, we have demonstrated that this epigenetic site-specific marker has high potential for pancreatic tissue identification and can be applied in PDAC diagnosis.
Subject(s)
Adenocarcinoma/diagnosis , Adenocarcinoma/pathology , Carcinoma, Pancreatic Ductal/diagnosis , Carcinoma, Pancreatic Ductal/pathology , DNA Methylation , Pathology, Molecular/methods , DNA/chemistry , Diagnosis, Differential , Humans , Predictive Value of Tests , Sensitivity and SpecificityABSTRACT
The role of human DNA methylation has been extensively studied in genomic imprinting, X-inactivation, and disease. However, studies of tissue-specific methylation remain limited. In this study, we use bioinformatics methods to analyze methylation data and reveal loci that are exclusively methylated or unmethylated in individual tissues. We collect 39 previously published DNA methylation profiles using an Illumina® HumanMethylation 27 BeadChip Kit containing 22 common tissues and involving 27,578 CpG loci across the human genome. We found 86 positions of tissue specific methylation CpG (TSM) that encompass 34 hypermethylated TSMs (31 genes) and 52 hypomethylated TSMs (47 genes). Tissues were found to contain 1 to 25 TSM loci, with the majority in the liver (25), testis (18), and brain (16). Fewer TSM loci were found in the muscle (8), ovary (7), adrenal gland (3), pancreas (2-4), kidney, spleen, and stomach (1 each). TSMs are predominantly located 0-300 base pairs in the 3' direction after the transcription start site. Similar to known promoters of methylation, hypermethylated TSM genes suppress transcription, while hypomethylated TSMs allow gene transcription. The majority of hypermethylated TSM genes encode membrane proteins and receptors, while hypomethylated TSM genes primarily encode signal peptides and tissue-specific proteins. In summary, the database of TSM loci produced herein is useful for the selection of tissue-specific DNA markers as diagnostic tools, as well as for the further study of the mechanisms and roles of TSM.
