Project description:To understand what dictates the emerging patterns of de novo DNA methylation, we mapped DNA methylation, chromatin, and transcription changes in purified fetal mouse germ cells using MIRA-chip, ChIP-chip, and strand-specific RNA-seq, respectively. De novo methylation occurred without any apparent trigger from preexisting repressing chromatin marks but was preceded by broad, low-level transcription along the entire genome in prospermatogonia. Only distinct short sequences remained unmethylated, precisely aligned with constitutive or emerging peaks of H3K4me2. Establishment of methylation at differentially methylated regions (DMRs) of imprinted genes, CpG islands, and IAPs followed these same default rules. Transcription run-through occurred at paternal DMRs with no- or diminishing H3K4me2 peaks. Maternal DMRs remained unmethylated among highly methylated DNA at precisely aligned H3K4me2 peaks with transcription initiating at least in one strand. Our results suggest that the pattern of de novo DNA methylation in prospermatogonia is dictated by opposing actions of broad, low-level transcription and dynamic patterns of active chromatin. ChIP-chip and MIRA-chip were performed to map histone modifications and DNA methylation at different devlopmental time points in germ cells and somatic cells along known imprinted domains and control regions, using custom NimbleGen tiling arrays.
Project description:DNA methylation at cytosine residues is an essential event for the normal development of multicellular eukaryotes. In mammals, de novo DNA methylation is restored to normal levels by the time of implantation, while epigenetic states of plant genes are often inherited over generations. Keywords: Organ comparison in methylome and transcriptome
