Methylation profiling of differentially expressed regions between C57BL/6 and BALB/c in bone marrow derived macrophages

DNA-methylation is a vital epigenetic mark that participates in establishing and maintaining chromatin structures and in regulating gene transcription during mammalian development and cellular differentiation. Inter-individual differences in methylation patterns may represent a major source of phenotypic variation, however, the determinants, inheritance, extent, and consequences of such differences are poorly understood. Here we have analysed methylation profiles of immune cells from two inbreed mouse strains (C57BL/6 & BALB/c) that represent prototypic models for Th1- or Th2-dominated immune responses. Using a methyl-CpG immunoprecipitation approach, genomes were fractionated into methylated and unmethylated genome pools and separately analysed at 180 genomic regions (covering 28 Mb of the mouse genome) that were selected based on differential gene expression between both mouse strains. Differentially methylated regions are detected by analyzing array probes for diametrically opposed enrichment behaviour between both hybridizations (e.g. a region that is relatively enriched in the unmethylated pool of BALB/c and shows reverse enrichment behaviour in the methylated pool is considered hypomethylated in BALB/c). The integrated analysis of hypo and hypermethylation profiles allowed the identification of several hundred differentially methylated regions, but also uncovered regions that were duplicated in one strain, contained single nucleotide polymorphisms or micro- and macro-deletions. Keywords: MCIp-on-Chip; comparative genomic hybridization Methylation profiles of regions, harbouring differentially expressed genes in BMM, were compared between C57BL/6 and BALB/c. Two independently grown, harvested and MCIp treated gDNA preparations were used for each mouse strain (Two biological replicates; One replicate per array). Hypo- and hypermethylated pools serve as diametrically oposed technical replicates (mirror approach).