Regulatory polymorphism in vitamin K epoxide reductase complex subunit 1 (VKORC1) affects gene expression and warfarin dose requirement.
Warfarin dose requirements have been associated with 2 main haplotypes in VKORC1, but the responsible polymorphisms remain unknown. To search for regulatory polymorphisms, we measured allelic mRNA expression of VKORC1 in human liver, heart, and B lymphocytes. The observed 2-fold allelic mRNA expression imbalance narrowed possible candidate SNPs to -1639G>A and 1173C<T. This genotype effect was observed selectively in the liver but not in heart or lymphocytes. In vitro expression of VKORC1 gene constructs, including coding and promoter regions, failed to reveal any genotype effect on transcription and mRNA processing. Chromatin immunoprecipitation with antibodies against acetyl-histone3 and K4-trimethyl-histone3 revealed preferential association of the promoter -1639 G allele with active chromatin, consistent with enhanced mRNA expression. The minor -1639 A allele generates a suppressor E-box binding site, apparently regulating gene expression by a mechanism undetectable with reporter gene assays. A clinical association study demonstrated that promoter SNP -1639G>A, and the tightly linked intron1 SNP 1173C>T, predict warfarin dose more accurately than intron 2 SNP 1542G>C in blacks. Increased warfarin dose requirement in blacks was accounted for by lower frequency of the -1639 A allele. Therefore, -1639G>A is a suitable biomarker for warfarin dosing across ethnic populations.
Wang
Danxin
D
Department of Pharmacology, Program in Pharmacogenetics, College of Medicine, The Ohio State University, Columbus, Ohio 43210, USA. wang.808@osu.edu
Chen
Huizi
H
Momary
Kathryn M
KM
Cavallari
Larisa H
LH
Johnson
Julie A
JA
Sadée
Wolfgang
W
D001706:Biopsy; D044383:Black People; D002478:Cells, Cultured; D002843:Chromatin; D005006:Ethnicity / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D008099:Liver / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009928:Organ Specificity; D010597:Pharmacogenetics; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic; D021122:Protein Subunits; D012333:RNA, Messenger / Q000032:analysis; D064417:Vitamin K Epoxide Reductases; D014859:Warfarin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D044465:White People
D002843:Chromatin; D021122:Protein Subunits; D012333:RNA, Messenger; D014859:Warfarin; D006899:Mixed Function Oxygenases; C578523:VKORC1 protein, human; D064417:Vitamin K Epoxide Reductases