In order to properly comprehend the epigenetic dysregulation that occurs during the course of disease, there is a need to characterize the epigenetic variability in healthy individuals that arises in response to aging and exposures, and to understand such variation within the biological context of the DNA sequence. We analyzed the methylation of 26,486 autosomal CpG loci in blood from 205 healthy subjects, using three complementary approaches to assess the association between methylation, age or exposures and local sequence features, such as CpG island status, repeat sequences, location within a polycomb target gene or proximity to a transcription factor binding site. We clustered CpGs (1) using unsupervised recursively partitioned mixture modeling (RPMM) and (2) bioinformatically-informed methods and (3) also employed a marginal model-based (non-clustering) approach. We observed associations between age and methylation and hair dye use and methylation, where the direction and magnitude was contingent on the local sequence features of the CpGs. Our results demonstrate that CpGs are differentially methylated dependent upon the genomic features of the sequence in which they are embedded, and that CpG methylation is associated with age and hair dye use in a CpG context-dependent manner in healthy individuals.
Bibliographical noteFunding Information:
Where Yij = sin-1(Bij1/2) is the variance-stabilized methylation value obtained by arcsine transformation of average βvalue,Bij, for subject This work was supported by the Flight Attendant Medical Research Institute grant YCSA 052341 to C.M.; and the National Institutes of Health (R01CA121147 to K.K., R01CA100679 to K.K., R01CA078609 to K.K., R01CA126939 to K.K., R01CA057494 to M.K., P42ES007373 to M.K., R01CA082354 to H.N.).
- Hair dye
- Methylation array