GSE131624
Global identification of retinoic acid regulated enhancers and silencers
Retinoic acid (RA) is known to regulate many genes during development by acting as a ligand for nuclear RA receptors that bind RA response elements (RAREs). However, identification of RAREs required to activate or repress specific genes during development has been quite difficult. Here, we focused on identification of RAREs in the developing trunk of vertebrate embryos during the early stages of body axis extension when RA controls neuromesodermal progenitor differentiation, spinal cord neurogenesis, somitogenesis, and forelimb bud initiation. Trunks from wild-type and Aldh1a2-/- mutants lacking RA synthesis were compared using ChIP-seq analysis for H3K27ac (a marker of gene activation) and H3K27me3 (a marker of gene repression) as well as RNA-seq analysis.  We identified numerous RAREs, defined as elements displaying differential deposition of H3K27ac and/or H3K27me3 marks in Aldh1a2-/- vs wild-type that contain a canonical RARE sequence and are near genes that have altered expression when RA is missing.  Our findings were able to differentiate genes likely to be directly regulated by RA via a RARE versus genes regulated by another factor further downstream. We identified several RA-regulated genes associated with changes in both H3K27ac and H3K27me3 near a RARE, providing new insight into how RAREs function in vivo. Overall design: 10 samples were analyzed: 4 samples each with replicates plus two input controls.