Complex Inheritance of Familial Hypercholanemia With Associated Mutations in TJP2 and BAAT

Nat Genet. 2003 May;34(1):91-6. doi: 10.1038/ng1147.

Abstract

Familial hypercholanemia (FHC) is characterized by elevated serum bile acid concentrations, itching, and fat malabsorption. We show here that FHC in Amish individuals is associated with mutations in tight junction protein 2 (encoded by TJP2, also known as ZO-2) and bile acid Coenzyme A: amino acid N-acyltransferase (encoded by BAAT). The mutation of TJP2, which occurs in the first PDZ domain, reduces domain stability and ligand binding in vitro. We noted a morphological change in hepatic tight junctions. The mutation of BAAT, a bile acid-conjugating enzyme, abrogates enzyme activity; serum of individuals homozygous with respect to this mutation contains only unconjugated bile acids. Mutations in both TJP2 and BAAT may disrupt bile acid transport and circulation. Inheritance seems to be oligogenic, with genotype at BAAT modifying penetrance in individuals homozygous with respect to the mutation in TJP2.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acyltransferases / genetics*
  • Bile Acids and Salts / blood*
  • Case-Control Studies
  • Ethnic Groups / genetics
  • Female
  • Genotype
  • Humans
  • Linkage Disequilibrium
  • Liver / pathology
  • Malabsorption Syndromes / blood*
  • Malabsorption Syndromes / genetics*
  • Malabsorption Syndromes / pathology
  • Male
  • Membrane Proteins / genetics*
  • Mutation*
  • Pedigree
  • Pennsylvania
  • Phenotype
  • Tight Junctions / pathology
  • Zonula Occludens-2 Protein

Substances

  • Bile Acids and Salts
  • Membrane Proteins
  • TJP2 protein, human
  • Zonula Occludens-2 Protein
  • Acyltransferases
  • bile acid-CoA amino acid N-acyltransferase