A comprehensive analysis of common genetic variation around six candidate loci for intrahepatic cholestasis of pregnancy

Am J Gastroenterol. 2014 Jan;109(1):76-84. doi: 10.1038/ajg.2013.406. Epub 2013 Dec 24.

Abstract

Objectives: Intrahepatic cholestasis of pregnancy (ICP) has a complex etiology with a significant genetic component. Heterozygous mutations of canalicular transporters occur in a subset of ICP cases and a population susceptibility allele (p.444A) has been identified in ABCB11. We sought to expand our knowledge of the detailed genetic contribution to ICP by investigation of common variation around candidate loci with biological plausibility for a role in ICP (ABCB4, ABCB11, ABCC2, ATP8B1, NR1H4, and FGF19).

Methods: ICP patients (n=563) of white western European origin and controls (n=642) were analyzed in a case-control design. Single-nucleotide polymorphism (SNP) markers (n=83) were selected from the HapMap data set (Tagger, Haploview 4.1 (build 22)). Genotyping was performed by allelic discrimination assay on a robotic platform. Following quality control, SNP data were analyzed by Armitage's trend test.

Results: Cochran-Armitage trend testing identified six SNPs in ABCB11 together with six SNPs in ABCB4 that showed significant evidence of association. The minimum Bonferroni corrected P value for trend testing ABCB11 was 5.81×10(-4) (rs3815676) and for ABCB4 it was 4.6×10(-7)(rs2109505). Conditional analysis of the two clusters of association signals suggested a single signal in ABCB4 but evidence for two independent signals in ABCB11. To confirm these findings, a second study was performed in a further 227 cases, which confirmed and strengthened the original findings.

Conclusions: Our analysis of a large cohort of ICP cases has identified a key role for common variation around the ABCB4 and ABCB11 loci, identified the core associations, and expanded our knowledge of ICP susceptibility.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B / genetics*
  • ATP Binding Cassette Transporter, Subfamily B, Member 11
  • ATP-Binding Cassette Transporters / genetics*
  • Case-Control Studies
  • Cholestasis, Intrahepatic / ethnology
  • Cholestasis, Intrahepatic / genetics*
  • Europe
  • Female
  • Genetic Association Studies
  • Genetic Predisposition to Disease
  • Heterozygote
  • Humans
  • Multidrug Resistance-Associated Protein 2
  • Mutation
  • Polymorphism, Single Nucleotide
  • Pregnancy
  • Pregnancy Complications / ethnology
  • Pregnancy Complications / genetics*
  • Whites / genetics

Substances

  • ABCB11 protein, human
  • ABCC2 protein, human
  • ATP Binding Cassette Transporter, Subfamily B
  • ATP Binding Cassette Transporter, Subfamily B, Member 11
  • ATP-Binding Cassette Transporters
  • Multidrug Resistance-Associated Protein 2
  • multidrug resistance protein 3