ACN9 and alcohol dependence: family-based association analysis in multiplex alcohol dependence families

A previous genome-wide linkage study of alcohol dependence (AD) in the Pittsburgh-based multiplex family study found suggestive evidence for linkage on Chromosome 7q, a region in which the ACN9 gene is located. Using the same two generation Pittsburgh family data in which linkage was found, data for a third generation was added. The expanded sample included 133 pedigrees with 995 individuals. Finer mapping was undertaken using six SNPs extending from rs1917939 to rs13475 with minor allele frequency (MAF) ≥0.15 and pair-wise linkage disequilibrium (LD) of r(2) <0.8 using the HapMap CEU population. Binary affection status, visual, and auditory P300 data were tested for family-based association. Family-based analyses found all six SNPs associated with affected status. Three SNPs are located upstream of the gene, two SNPs are within intron 1 and one is in Exon 4. FBAT P-values for the six SNPs ranged between 0.05 and 0.0005. Haplotype analysis revealed one four-SNP block formed by rs10499934, rs7794886, rs12056091, and rs13475 with an overall significant association at P = 0.0008. Analysis of visual P300 amplitude data, a known endophenotype of alcohol dependence risk, revealed a significant association for SNPs within intron 1 and exon 4 under a dominant model of transmission. Family-based association analysis shows the ACN9 gene significantly associated with alcohol dependence and P300 amplitude variation. The potential importance of the ACN9 gene for AD risk may be related to its role in gluconeogenesis which may be involved in the regulation of alcohol metabolism.