Retrotransposon-based profiling of mammalian epigenomes: DNA methylation of IAP LTRs in embryonic stem, somatic and cancer cells

In this study, we analyzed the DNA methylation levels of 4799 IAP LTRs in three murine cell types: AB2.2 ES cells, somatic cells and a neuroblastoma cell line Neuro2A. According to the results, half of the IAP LTR retrotransposons show constant methylation patterns between the three cell types whereas the remaining half display variable levels of methylation. About half of the variably methylated IAP LTRs tend to be hypomethylated in ES cells, and nearly all of this group are hypomethylated in Neuro2A cells. Interestingly, the observed hypomethylation in both cell types occur in a non-uniform, locus-specific manner and to various degrees of severity, with some of them being easily detectible by COBRA. Overall, this study demonstrates the feasibility of HT-TREBS to study alterations in DNA methylation at retrotransposons in a locus-specific manner in multiple cell types and further suggests the potential utility of this technique in developing epigenetic biomarkers for tracking disease progression. Overall design: HT-TREBS has been used with the Ion Torrent PGM platform to analyze the DNA methylation of 4799 IAP LTRs in a locus-specific manner in 3 cell types: somatic cells (previously submitted under GEO Accession GSE49222), AB2.2 ES cells and Neuro2A cells