Rapid and Pervasive Changes in Genome-Wide Enhancer Usage During Mammalian Development

Here we used epigenomic profiling for H3K27ac, a mark of active enhancers to examine the genome-wide in vivo utilization of enhancers in three different mouse tissues across seven developmental stages, ranging from mid-gestation through adulthood. The majority of the ~90,000 enhancers identified exhibited tightly temporally restricted activity windows and were associated with stage-specific biological functions and regulatory pathways in individual tissues. Comparative genomic analysis revealed that evolutionary conservation of enhancers decreases following mid-gestation across all tissues examined. The dynamic enhancer activities uncovered in this study illuminate rapid and pervasive temporal in vivo changes in enhancer usage underlying developmental processes and demonstrate the value of time-course chromatin profiling of relevant tissues across development. Examination of H3K27ac in mouse forebrain, heart and liver tissues collected across developmental stages.