Objectives: This study investigated the involvement of ADH4 gene polymorphisms in the susceptibility to alcohol use disorders.
Methods: Thirty-eight single-nucleotide polymorphisms (SNPs) in and around the ADH4 gene were investigated in 136 Italian alcoholics and 276 healthy controls. A new approach based on a bioinformatic method selected 26 SNPs that may affect the splicing sites, destroying or creating binding sites of splicing regulatory proteins.
Results: Case-control comparisons for allele and genotype frequencies showed that ADH4 SNPs were associated with alcohol dependence but not with alcohol abuse. The association signal was strongest for rs1009145, rs13148577 (both P=0.0008) and rs7689753 (P=0.0007), whose minor alleles were predicted to alter the target protein sequences involved in mRNA splicing. A pairwise linkage disequilibrium analysis showed that all SNPs except five were located in a single haplotype block. Six haplotype tag SNPs were selected to infer haplotypes and to estimate their frequency distributions. A logistic regression analysis confirmed the association between ADH4 variants and alcohol dependence when sex, age, years of education, marital status and the allele genotype, haplotype and diplotype data of the six haplotype tag SNP were considered. Haplotype ATAAAT, which contained the minor allele of rs10009145 and the major allele of rs7689753, increased the risk of alcohol dependence, whereas haplotype GGGGAT, bearing the major allele of rs10009145 and the minor allele of rs7689753, protected against it. Again, there was no evidence of an association with alcohol abuse.
Conclusion: These data suggest that ADH4 intronic variants play a role in alcohol dependence susceptibility in Italian populations. Functional studies are needed to establish the role of the genetic variations that seem to affect the splicing mechanism.