Flame retardants (FRs) are a ubiquitous group of chemicals used in furniture, car seats, and children's products and can leach into indoor dust, resulting in chronic exposures. Epidemiological and experimental evidence shows that developmental FR exposures result in short- and long-term adverse health outcomes, but the knowledge gap remains- what targets do they attack and how do they drive adverse outcomes? Using zebrafish, our preliminary data on a brominated FR, tetrabromobisphenol A (TBBPA) shows that TBBPA exposures during early developmental windows (cleavage, blastula, early gastrula) results in developmental delays, mortality and downstream defects in dorsoventral patterning. These early windows are marked by a rapid maternal to zygotic transition (MZT) and zygotic genome activation (ZGA) when maternally loaded mRNA degrade, and zygotic genome is activated. Our mRNA-sequencing data reveals that TBBPA inhibits ZGA and targets chromatin remodeling. Since the latter process is regulated by histone acetylation H3K27ac and catalyzed by P300 protein, we used a P300 activator CfPB and showed that co-exposures with TBBPA and P300 activator mitigated the TBBPA-induced phenotypes. Molecular docking showed strong binding affinities between TBBPA and P300. Based on these, our overarching goal is to understand the diversity ofTBBPA-induced epigenetic and genetic modifications and how they modulate embryonic development. Our oldective is to determine how TBBPA disrupts ZGA through histone modifiers and the downstream consequences on chromatin remodeling and gene expression. The central hypothesis is that TBBPA inhibits P300 activity and limits zygotic transcription by inhibiting H3K27 acetylation and chromatin remodeling of zygotic genome. This hypothesis will be tested through two specific aims. Within aim 1, we will conduct P300 activity assays and quantify of global and genelevel H3K27ac using Western Blots and ChIP-seq. In aim 2, we will use ATAC-seq and nascent RNA-seq to examine chromatin accessibility and nascent RNA transcription. We will also integrate the multiome data from both aims into a gene regulatory model for systems level analyses of pathways that are impacted by TBBPA during ZGA. Based on the sequencing outcomes, we will select specific targets and use qPCR to quantify gene expression across environmentally relevant TBBPA concentrations. The grant is innovative, since it is the first work to systemically assess how an environmental toxicant impacts ZGA through histone modifications and leverages state of the art technologies, including nascent RNA seq, to describe a novel adverse outcome pathway (AOP) for TBBPA early life exposures that spans multiple biological levels from epigenetic regulation (acetylation), chromatin biology, co-regulated genes, signaling networks and organism development. The work is significant since it will reveal how TBBPA directly or indirectly targets proteins or gene products and their regulatory regions th...