SNP Association Analyses Of NCAM1, ADH And ALDH Genes With Alcohol Drinking Behavior

Alcohol dependence(AD)is a complex disease interacted by a number of micro-effect genes and environmental factors with high heritabitity.Currently,search for pathogenic genes has been widely given attention in the molecular genetics studies about AD with research strategies of population association and linkage analyses.Some typical candidate genes have been identified,such as alcohol dehydrogenase genes(ADH genes), aldehyde dehydrogenase genes(ALDH genes),dopamine receptor D2 gene(DRD2),gamma-aminobutyric-acid receptor alpha-2 gene (GABRA2),muscarinic acetylcholine receptor M2 gene(CHRM2), and so on.Regular drinking behaviors are essential for coming into alcohol dependence.We found alcohol drinking had a high heritabitity in Caucasian(h~2=50%～60%).In this reaseach, we identified the relationship of alcohol drinking phenotype and several important candidate genes-NCAM1,ADH genes and ALDH genes.The sample had 904 unrelated subjects,who were US Caucasians of European origin.With an isolation kit(Gentra systems,Minneapolis,MN,USA),genomic DNA was extracted from human blood.SNP genotyping was performed with the Affymetrix Mapping 250k Nsp1 and Affymetrix Mapping 250k Sty1 arrays. Statistical analysis was performed using allelic,genotype and haplotypic association tests in all the data with HelixTree 5.3.1(Golden Helix,Bozeman,MT,USA).We performed an association study by using high density SNPs micro-array(96 SNPs)to neural cell adhesion molecule 1 gene(NCAM1),which was located in chromosome 11q23.1.We found rs1975259,in intron 5 of NCAM1,was significantly associated to alcohol drinking by 5-SNP-haplotype sliding windows association study in the male(adjusted P=9.60E-05).Protein NCAM,encoded by NCAM1,participate several neural functions, and relate to dopamine in brain.Because the results in the entire and female group were not significant,so NCAM1 maybe related to the sex difference.We also performed an association study by using 88 SNPs to alcohol dehydrogenase genes and 356 SNPs to acetaldehyde dehydrogenase genes.The haplotype association researches indicated that ALDH1B1,located in chromosome 9p11.1,was significantly associated to alcohol drinking in the entire group(rs7856735,adjusted P=0.0056;rs12352894,adjusted P =0.0074)and in the female(rs12352894,adjusted P=0.0079) We found rs2585668,in upstream of ALDH1B1,had significantly association with alcohol drinking by genotype association study(adjusted P=0.0266).In previous researches,ALDH1B1 69val variances were related to nondrinking and decreased alcohol intake,while it was not identified ALDH1B1 arg901eu allele were related to alcohol dependence.Our study results indicacted that rs7856735,rs12352894 and rs2585668 loci, which located in upstream of ALDH1B1 gene and never been reported in alcohol dependence genetic stuties,associated to alcohol drinking,while 1a69val and arg901eu alleles polymorphisms did not associated to this phenotype.Some previous alcohol dependence research results with ADH and ALDH genes were not replicated in our present study.It was likely to be due to the lower density of SNPs not to overlap all loci in previous researches.For example,the SNPs of ADH1B gene were not set in the Affymetrix 5.0 SNP chips.Furthermore,the polymorphism differences of alcohol dependence candidate genes distributed in different ethnic population,as we know,there was no ALDH2*2 allele in the Caucasian.