show Abstracthide AbstractWe characterized the trophoblast stem cell epigenome and gene expression profiles in rat and mouse. Overall design: We profiled 5 histone modifications (+ chromatin input) using ChIP-Seq, and digital expression profiles (3' RNA-Seq) for trophoblast stem cells derived from rat and mouse. Furthermore, for mouse, we profiled key trophoblast stem cell factors Elf5, Cdx2, and Eomes. We found that enhancer regions (defined as distal regions of H3K27ac/H3K4me1 enrichment) were enriched for species-specific endogenous retroviral elements.