Project name: DNA methylation profiling of whole blood from Han Chinese individuals: identification of age-related CpG sites for forensic use

Description: Age-related CpG (AR-CpG) sites are currently the most promising molecular markers for age estimation. However, AR-CpG sites for the Han Chinese population have not yet been systematically identified. Besides, there may be high-performance AR-CpG sites beyond the coverage of the commonly used Illumina HumanMethylation450 BeadChip that covers over 450,000 CpG sites (450K), which accounts only 1.6% of CpG sites in the human genome. Therefore, we initiated a project to perform genome-wide methylation analysis on whole blood samples from 42 healthy Han Chinese individuals (21 males and 21 females, 18–62 years) using the newly developed Illumina Infinium MethylationEPIC array that assesses over 850,000 CpG sites (850K) to identify AR-CpG sites for forensic use systematically. The 850K methylation array contains > 90% of 450K CpG sites but adds 413,745 CpG sites. As expected, we not only replicated several high-performance AR-CpG sites previously discovered using the Illumina 450K BeadChip, such as cg16867656 (ELOVL2), cg22454769 (FHL2), and cg10501210 (C1orf132), but also identified 41 (60.3%), 34 (22.5%), and 382 (48.7%) novel AR-CpG sites from the methylation profiles of 21 males, 21 females, and all individuals, respectively.Overall design: DNA extraction, bisulfite conversion, microarray hybridization, and chip data analysis were performed by Genergy Inc. (Shanghai, China), with the experimental procedures following the respective manufacturers' instructions. Briefly, genomic DNA was extracted from whole blood using QIAamp DNA Blood Mini Kit (Qiagen, Hilden, Germany), quantified with Quant-iT PicoGreen dsDNA Assay Kit (Thermo Fisher Scientific, MA, USA), and tested for its integrity on agarose gels. DNA samples that passed the quality control were treated with bisulfite using EZ DNA Methylation Kit (Zymo Research, CA, USA). Bisulfite converted DNA from the 42 samples were hybridized to the Illumina Infinium MethylationEPIC Beadchip v1.0. Methylation arrays were imaged with an Illumina iScan using standard settings. The methylated and unmethylated intensities of the images were extracted using R package ChAMP v2.8.9. Methylation levels of CpG sites are expressed as beta values.

Data type: Epigenomics

Sample scope: Multiisolate

Relevance: Medical

Last updated: 2019-12-09