title: Genetic basis for a lower prevalence of deficient CYP2D6 oxidative drug metabolism phenotypes in black Americans.
abstract: Debrisoquin hydroxylase (CYP2D6) is a cytochrome P450 enzyme that catalyzes the metabolism of > 30 commonly prescribed medications. Deficiency in CYP2D6 activity, inherited as an autosomal recessive trait, was found to be significantly less common in American blacks (1.9%) than whites (7.7%). To determine the genetic basis for this difference, inactivating CYP2D6 mutations were assessed by allele-specific PCR amplification and RFLP analyses of genomic DNA from 126 unrelated whites and 127 unrelated blacks. Blacks had a twofold lower frequency (8.5 versus 23%, P = 0.001) of the CYP2D6(B) mutation (point mutation at intron 3/exon 4 splice site), while complete deletion of the CYP2D6 gene (5.5% blacks, 2.4% whites), and the CYP2D6(A) mutation (single nucleotide deletion in exon 5; 0.24% blacks, 1.4% whites) were not different between the two groups. The prevalence of heterozygous genotypes was significantly lower in blacks (25 versus 42% of extensive metabolizers, P = 0.009), consistent with the observed prevalence of the deficient trait in blacks and whites. We conclude that the same CYP2D6 mutations lead to a loss of functional expression in blacks and whites, but American blacks have a lower prevalence of the deficient trait due to a lower frequency of the CYP2D6(B) mutation. This could explain racial differences in drug effects and disease risk.
authors.affiliation: Pharmaceutical Department, St. Jude Children's Research Hospital, Memphis, Tennessee 38101.
authors.forename: W E
authors.initials: WE
authors.lastname: Evans
authors.forename: M V
authors.initials: MV
authors.lastname: Relling
authors.forename: A
authors.initials: A
authors.lastname: Rahman
authors.forename: H L
authors.initials: HL
authors.lastname: McLeod
authors.forename: E P
authors.initials: EP
authors.lastname: Scott
authors.forename: J S
authors.initials: JS
authors.lastname: Lin
mesh_terms: D001483:Base Sequence; D044383:Black People / Q000235:genetics*; D019389:Cytochrome P-450 CYP2D6; D003577:Cytochrome P-450 Enzyme System / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D004247:DNA / Q000097:blood / Q000235:genetics / Q000302:isolation & purification; D017353:Gene Deletion; D005838:Genotype; D006801:Humans; D007962:Leukocytes / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D014481:United States; D001741:Black or African American
chemical_list: D009838:Oligodeoxyribonucleotides; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D019389:Cytochrome P-450 CYP2D6