The nuclear receptor FXR (Nr1h4) is a bile acid–activated transcription factor,31–34 which is a key regulator of hepatocyte protective responses to cholestasis.7,35 Thus, FXR agonists have been used as treatment for human cholestatic liver diseases; however, the mechanisms by which these steroidal compounds elicit liver protection are poorly understood. This evidence concerns the gene NR1H4 and cholestasis.