title: Haplotype-based study of the association of alcohol-metabolizing genes with alcohol dependence in four independent populations.
abstract: BACKGROUND
  Ethanol is metabolized by 2 rate-limiting reactions: alcohol dehydrogenases (ADH) convert ethanol to acetaldehyde that is subsequently metabolized to acetate by aldehyde dehydrogenases (ALDH). Approximately 50% of East Asians have genetic variants that significantly impair this pathway and influence alcohol dependence (AD) vulnerability. We investigated whether variation in alcohol metabolism genes might alter the AD risk in four non-East Asian populations by performing systematic haplotype association analyses to maximize the chances of capturing functional variation.
  
  
  METHODS
  Haplotype-tagging SNPs were genotyped using the Illumina GoldenGate platform. Genotypes were available for 40 SNPs across the ADH genes cluster and 24 SNPs across the two ALDH genes in four diverse samples that included cases (lifetime AD) and controls (no Axis 1 disorders). The case control sample sizes were the following: Finnish Caucasians: 232, 194; African Americans: 267, 422; Plains American Indians: 226, 110; and Southwestern American (SW) Indians: 317, 72.
  
  
  RESULTS
  In all four populations, as well as HapMap populations, 5 haplotype blocks were identified across the ADH gene cluster: (i) ADH5-ADH4; (ii) ADH6-ADH1A-ADH1B; (iii) ADH1C; (iv) intergenic; (v) ADH7. The ALDH1A1 gene was defined by 4 blocks and ALDH2 by 1 block. No haplotype or SNP association results were significant after correction for multiple comparisons; however, several results, particularly for ALDH1A1 and ADH4, replicated earlier findings. There was an ALDH1A1 block 1 and 2 (extending from intron 5 to the 3' UTR) yin yang haplotype (haplotypes that have opposite allelic configuration) association with AD in the Finns driven by SNPs rs3764435 and rs2303317, respectively, and an ALDH1A1 block 3 (including the promoter region) yin yang haplotype association in SW Indians driven by 5 SNPs, all in allelic identity. The ADH4 SNP rs3762894 was associated with AD in Plains Indians.
  
  
  CONCLUSIONS
  The systematic evaluation of alcohol-metabolizing genes in four non-East Asian populations has shown only modest associations with AD, largely for ALDH1A1 and ADH4. A concentration of signals for AD with ALDH1A1 yin yang haplotypes in several populations warrants further study.
authors.affiliation: From the Laboratory of Neurogenetics, National Institute on Alcohol Abuse and Alcoholism, NIH, Bethesda, Maryland 20892, USA. liujixia@mail.nih.gov
authors.forename: Jixia
authors.initials: J
authors.lastname: Liu
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Zhou
authors.forename: Colin A
authors.initials: CA
authors.lastname: Hodgkinson
authors.forename: Qiaoping
authors.initials: Q
authors.lastname: Yuan
authors.forename: Pei-Hong
authors.initials: PH
authors.lastname: Shen
authors.forename: Connie J
authors.initials: CJ
authors.lastname: Mulligan
authors.forename: Alex
authors.initials: A
authors.lastname: Wang
authors.forename: Rebecca R
authors.initials: RR
authors.lastname: Gray
authors.forename: Alec
authors.initials: A
authors.lastname: Roy
authors.forename: Matti
authors.initials: M
authors.lastname: Virkkunen
authors.forename: David
authors.initials: D
authors.lastname: Goldman
authors.forename: Mary-Anne
authors.initials: MA
authors.lastname: Enoch
mesh_terms: D001741:Black or African American / Q000235:genetics; D000426:Alcohol Dehydrogenase / Q000235:genetics*; D000437:Alcoholism / Q000235:genetics*; D000080924:Aldehyde Dehydrogenase 1 Family; D000483:Alleles; D000431:Ethanol / Q000378:metabolism*; D005260:Female; D005838:Genotype; D006239:Haplotypes; D006801:Humans; D007198:Indians, North American / Q000235:genetics; D007527:Isoenzymes / Q000235:genetics*; D008297:Male; D020641:Polymorphism, Single Nucleotide; D050697:Retinal Dehydrogenase / Q000235:genetics*; D044465:White People / Q000235:genetics
chemical_list: D007527:Isoenzymes; D000431:Ethanol; D000426:Alcohol Dehydrogenase; D000080924:Aldehyde Dehydrogenase 1 Family; C510223:ALDH1A1 protein, human; D050697:Retinal Dehydrogenase