Differential effect of ABCB1 haplotypes on promoter activity

Jordan T. Speidel, Meixiang Xu, Sherif Z. Abdel-Rahman

    Research output: Contribution to journalArticle

    5 Scopus citations

    Abstract

    Objective Promoter single-nucleotide polymorphisms (SNPs) of the ABCB1 gene, encoding the placental efflux transporter P-glycoprotein, can affect its expression and alter xenobiotic transfer from the maternal to the fetal circulation. Because SNPs are arranged in specific combinations as defined haplotypes, the aims of this study were to: (i) determine the placental haplotype structure of the ABCB1 promoter and (ii) determine the differential effect of these haplotypes on placental ABCB1 promoter activity. Materials and methods DNA samples from 100 healthy placentas were PCR-amplified and sequenced to identify existing SNPs in the proximal ABCB1 promoter. The haplotype structure encompassing these SNPs was inferred by PHASE analysis. Luciferase reporter constructs representing these haplotypes were generated and transfected into human placental 3A cells and their effect on ABCB1 promoter activity was determined using a dual-luciferase assay. Results We identified 12 ABCB1 promoter SNPs. These SNPs were predicted by PHASE to segregate into 28 haplotypes with frequencies ranging between 0.019 and 0.88. We found 12 of these haplotypes in our population in addition to two haplotypes not predicted by PHASE. We also generated two haplotypes to determine individual SNP effects for a total of 16 studied. Compared with the ancestral haplotype, three haplotypes significantly up-regulated (107-266% increase; P<0.05), one significantly down-regulated (95.4% decrease; P<0.01), and 12 had no statistically significant effect on ABCB1 promoter activity. Discussion and conclusion Our data show that the effect of SNPs on promoter activity depends on their presence in a specific haplotype. This indicates that haplotypes, rather than individual SNPs, could play a significant role in regulating placental P-glycoprotein expression and affect placental transfer and fetal exposure to xenobiotics.

    Original languageEnglish (US)
    Pages (from-to)69-77
    Number of pages9
    JournalPharmacogenetics and Genomics
    Volume28
    Issue number3
    DOIs
    StatePublished - Jan 1 2018

    Keywords

    • ABCB1
    • P-glycoprotein
    • promoter haplotypes
    • single-nucleotide polymorphisms

    ASJC Scopus subject areas

    • Molecular Medicine
    • Molecular Biology
    • Genetics
    • Genetics(clinical)

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