Deleterious Variants in ABCC12 are Detected in Idiopathic Chronic Cholestasis and Cause Intrahepatic Bile Duct Loss in Model Organisms

Gastroenterology. 2021 Jul;161(1):287-300.e16. doi: 10.1053/j.gastro.2021.03.026. Epub 2021 Mar 23.


Background & aims: The etiology of cholestasis remains unknown in many children. We surveyed the genome of children with chronic cholestasis for variants in genes not previously associated with liver disease and validated their biological relevance in zebrafish and murine models.

Method: Whole-exome (n = 4) and candidate gene sequencing (n = 89) was completed on 93 children with cholestasis and normal serum γ-glutamyl transferase (GGT) levels without pathogenic variants in genes known to cause low GGT cholestasis such as ABCB11 or ATP8B1. CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 genome editing was used to induce frameshift pathogenic variants in the candidate gene in zebrafish and mice.

Results: In a 1-year-old female patient with normal GGT cholestasis and bile duct paucity, we identified a homozygous truncating pathogenic variant (c.198delA, p.Gly67Alafs∗6) in the ABCC12 gene (NM_033226). Five additional rare ABCC12 variants, including a pathogenic one, were detected in our cohort. ABCC12 encodes multidrug resistance-associated protein 9 (MRP9) that belongs to the adenosine 5'-triphosphate-binding cassette transporter C family with unknown function and no previous implication in liver disease. Immunohistochemistry and Western blotting revealed conserved MRP9 protein expression in the bile ducts in human, mouse, and zebrafish. Zebrafish abcc12-null mutants were prone to cholangiocyte apoptosis, which caused progressive bile duct loss during the juvenile stage. MRP9-deficient mice had fewer well-formed interlobular bile ducts and higher serum alkaline phosphatase levels compared with wild-type mice. They exhibited aggravated cholangiocyte apoptosis, hyperbilirubinemia, and liver fibrosis upon cholic acid challenge.

Conclusions: Our work connects MRP9 with bile duct homeostasis and cholestatic liver disease for the first time. It identifies a potential therapeutic target to attenuate bile acid-induced cholangiocyte injury.

Keywords: Bile Duct Paucity; Mouse; Progressive Familial Intrahepatic Cholestasis; Zebrafish.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / genetics*
  • ATP-Binding Cassette Transporters / metabolism
  • Animals
  • Apoptosis
  • Bile Ducts, Intrahepatic / metabolism
  • Bile Ducts, Intrahepatic / pathology*
  • Case-Control Studies
  • Cholestasis, Intrahepatic / genetics*
  • Cholestasis, Intrahepatic / metabolism
  • Cholestasis, Intrahepatic / pathology*
  • Chronic Disease
  • Exome Sequencing
  • Female
  • Gene Editing
  • Genetic Association Studies
  • Genetic Predisposition to Disease
  • Humans
  • Infant
  • Mice
  • Mice, Inbred C57BL
  • Mutation*
  • Phenotype
  • Zebrafish
  • Zebrafish Proteins / genetics*
  • Zebrafish Proteins / metabolism


  • ABCC12 protein, human
  • ATP-Binding Cassette Transporters
  • Abcc12 protein, mouse
  • Zebrafish Proteins