FXR isoform selective DNA binding in mouse liver organoids

The farnesoid X receptor (FXR) is a nuclear receptor activated by bile acids that regulates metabolic processes. FXR is expressed as four isoforms (a1-4), and their relative abundance is specific to tissue and bio-energetic conditions (Correia JC et al. 2015). Depending on the FXR isoform expressed, there is a degree of selectivity in target-genes activation. However, there is currently no data on how isoform-linked target selectivity is achieved. In this study we investigate the DNA binding profile of FXR isoforms on mouse liver organoids treated briefly with the FXR agonist obeticholic acid (OCA). From this analysis we concluded that FXR isoforms a2 and a4 binds to additional DNA regions, enriched for a specific discriminating binding motif. This binding led to isoform-selective gene regulation. Therefore, DNA binding selectivity therefore plays a defining role in FXR isoform-specific effects. Overall design: FXR -/- mouse liver organoids were transduced with mouse FXR isoforms a1, a2, a3, a4 or H2b-NeonGreen(ko) using lentiviral vectors (pLV IRES PuroR). After selection, the organoids were differentiated into the hepatocyte lineage before fixation and processing