DNA methylation signatures of adolescent victimization: Analysis of a longitudinal monozygotic twin sample.

Genome-wide patterns of DNA methylation were quantified using the Illumina Infinium EPIC array (“EPIC array”) in DNA samples isolated from buccal swabs collected at ages 5, 10 and 18 and whole blood samples collected at age 18 from 118 Monozygotic twin pairs from the Environmental Risk (E-Risk) Longitudinal Twin Study. Comparison of DNA methylation profiles of 233 age 18 blood samples with data on EPIC and Illumina 450K methylation arrays. Bisulphite converted DNA from the 944 samples were hybridised to the Illumina Infinium HumanMethylation850 BeadChip; raw data (preQC folder->raw idats folder; Phenotype_file_944preQC.csv), processed files (betas_normalised.csv, pheno.csv). Overlapping samples (N=233) had methylation data on two DNA methylation arrays -EPIC and 450K, we compared the methylation profiles of these samples to assess the correlation between the two arrays using two strategies: -(1)When these samples were normalized together (raw files for EPIC array data are in preQC folder->raw idats folder; Overlaping_probes_normalised_together_450K_EPIC_pheno.csv, raw idats for 450K are in folder raw_idats_450k, processed betas for both arrays file (Overlaping_probes_normalised_together_450K_EPIC_betas.csv) (2) When these samples were normalized separately - only overlapping probes on both arrays for the common samples were analysed - processed betas file for 450K array (Overlaping_probes_normalised_seperately_450K_betas.csv, Overlaping_probes_normalised_seperately_450K_pheno.csv) and EPIC array (Overlaping_probes_normalised_seperately_EPIC_betas.csv, Overlaping_probes_normalised_seperately_EPIC_pheno.csv). Categories description: 1 - MZ discordant twins exposed to adolescence victimisation, 2 - MZ concordant twins unexposed to adolescence victimisation, and 3 - MZ concordant twins exposed to adolescent victimisation