Egr1 Recruits Tet1 to Shape the Brain Methylome during Early Postnatal Development

Early growth response gene-1 (Egr1) is a critical transcription factor involved in many important biological processes, including neuronal plasticity and memory formation. With a rapid increase in expression during the first few weeks after birth, Egr1 controls the selection, maturation and functional integration of newborn neurons. The regulation of Egr1-mediated gene expression has been shown to be under methylation control. However, Egr1 target sites and their epigenetic regulation in the nervous system remains largely unknown. In this study, we performed ChIP-seq for EGR1 in mouse frontal cortex and identified a large number of EGR1 binding sites with their cell-type specific methylation patterns established during postnatal frontal cortex development. More specifically, the CpG dinucleotides within these EGR1 binding sites become hypo-methylated in mature neurons but remain heavily methylated in glia. We further demonstrated that EGR1 recruits a DNA demethylase TET1 to remove DNA methylation at EGR1 binding sites and activate downstream genes. In addition, we found that the frontal cortexes from knockout mice with the loss of Egr1 or Tet1 share strikingly similar profiles in both gene expression and DNA methylation. In summary, our study reveals Egr1 as a key mediator for gene-environment interactions shaping brain methylome together with Tet1 during early postnatal development and provides an important new insight into how early life experience may shape the brain methylome. This SuperSeries is composed of the SubSeries listed below. Genome-wide profiles of EGR1 binding in prefrontal cortices of 6-week old male mice were generated in duplicate using Illumina HiSeq 2000 platform. Reduced Represented Bisulfite Sequencing (RRBS) and RNA-seq of mouse frontal cortex tissue from 6~8 week old Egr1-/- and Tet1-/- mice were performed