GPT and cholestasis: Consistent with the icteric appearance of the DKO liver, serum markers of cholestasis such as alkaline phosphatase (ALP), γ-glutamyltranspeptidase (γ-GTP), cholesterol, bilirubin, and bile acid, as well as markers of liver injury (alanine and asparatate aminotransferases; ALT, AST) were significantly increased in 4-week-old DKO mice (S4 Fig), suggesting that either impairment of the biliary system or hepatocyte death is the cause of the liver pathology.