Adenosine triphosphate-binding cassette subfamily B member 4 (Abcb4)−/− (ie, Mdr2: multiple drug resistance 2) mice are used as a model for sclerosing cholangitis because they reflect the progressive fibrosing cholangitis aspects of human PSC and also develop intrahepatic cholangiocarcinoma.19 The gene discussed is ABCB4; the disease is sclerosing cholangitis.