Abstract
The flavin-containing monooxygenases (FMOs) are important for the disposition of a variety of toxicants, therapeutics, and dietary components. Although FMO1 is the dominant isoform in fetal liver and adult kidney and intestine and despite up to a 10-fold intersubject variation in expression, a paucity of information is available on FMO1 genetic variability. To address this issue, 24 samples from the Coriell DNA Polymorphism Discovery Resource Panel were sequenced revealing 10 common single nucleotide polymorphisms (SNPs): four located upstream of the structural gene; three within exonic sequences; one within the intron 1 splice donor site; and two with the 3′-untranslated region. Six of these variants are novel. Compared with other FMO loci within the chromosome 1q23-25 cluster, FMO1 seems more highly conserved. Of the identified FMO1 SNPs, only a C>A transversion 9,536 base pairs upstream of the exon 2 ATG start codon (g.-9,536C>A) would likely affect function, because it lies within the conserved core binding sequence for the yin yang 1 (YY1) transcription factor. Electrophoretic mobility shift assays demonstrated that the g.-9,536C>A transversion eliminated YY1 binding. Furthermore, data from transient expression assays in HepG2 cells suggested this SNP could account for a 2- to 3-fold loss of FMO1 promoter activity. Genotype analysis revealed a g.-9,536A allele (FMO1*6) frequency of 13 and 11% in African- and northern European-Americans, respectively, but a significantly higher frequency of 30% in Hispanic-Americans. Thus, the FMO1*6 variant may account for some of the observed interindividual variation in FMO1 expression.
Footnotes
-
↵1 Allele nomenclature follows the guidelines adopted for the human cytochrome P450 gene family (http://www.imm.ki.se/CYPalleles/criteria.htm).
-
↵2 Genetic variants (SNPs) are named based on the recommendations of the Nomenclature Working Group as outlined by den Dunnen and Antonarakis (2001). In brief, “g”. indicates a reference genomic sequence followed by a gene coordinate based on the A of the ATG-translation initiation codon being assigned +1, followed by the nucleotide variation, e.g., C>T where the first nucleotide is the dominant allele.
-
These studies were supported in part by U.S. Public Health Services Grant CA53106 from the National Cancer Institute and funds from the Children's Hospital Foundation of Wisconsin.
-
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
-
DOI: 10.1124/jpet.103.053686.
-
ABBREVIATIONS: FMO, flavin-containing monooxygenase; kbp, kilobase pair; HNF1, hepatocyte nuclear factor 1; YY1, yin yang 1; Oct1, octamer binding protein 1; SNP, single nucleotide polymorphism; bp(s), base pair(s); PCR, polymerase chain reaction; EMSA, electrophoretic mobility shift assay.
- Received April 30, 2003.
- Accepted June 6, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|