GSE191030
Loss of Liver X Receptor alters the transcriptional landscape
The nuclear receptors LXRa and LXRb play a crucial role in regulating hepatic lipid metabolism. Many genes induced in response to pharmacologic LXR agonism in mouse liver have been defined; however, the transcriptional consequences of loss of LXR binding to its genomic targets are not well characterized. Here we addressed how deletion of both LXRa and LXRb from mouse liver (LXRDKO) affects the transcriptional regulatory landscape by integrating changes in LXR/RXR binding, chromatin accessibility, and gene expression. Many genes involved in fatty acid metabolism have reduced expression and chromatin accessibility at their intergenic and intronic regions in LXRDKO livers. Genes that were upregulated in LXRDKO livers have increased chromatin accessibility in their promoter regions and are enriched for those with functions not linked to lipid metabolism. We further showed that loss of LXR binding in liver reduces the activity of a broad set of hepatic transcription factors, inferred through motif accessibility. In contrast, accessibility at promoter NFY motifs is strongly increased in the absence of LXR. Surprisingly, we define small set of direct target genes for ligand-dependent LXR repression. These genes with LXR binding sites show increased expression in LXRDKO liver and reduced expression in response to LXR agonist treatment. In summary, while our results support the established roles for LXRs as ligand-dependent activators of genes linked to lipid metabolism, the binding of LXR/RXR heterodimers to the hepatic genome has broad effects on the transcriptional landscape that extend beyond its canonical function as an activator of lipid metabolic genes. Overall design: RNA-Seq and ATAC-Seq of LXRa-/- LXRb-/- double knockout mice compared to control (n=2).