SEROTONIN TRANSPORTER GENE POLYMORPHISM IN ITALIAN ALCOHOLICS

Aims. The serotonin transporter gene (5-HTT) encodes a transmembrane protein that plays an important role in regulating serotonergic neurotransmission. Dysfunction in the serotonergic system is significantly involved in both the aetiology and maintenance of alcohol misuse. The regulatory region of the 5-HTT gene contains a series of repeated sequences; two common alleles in this region differ in length by 44 bp. A functional polymorphism in the promoter region of the 5-HTT gene has been identified and is known to be associated with altered serotonin activity, with the short (S) form of this polymorphism being associated with reduced transcriptional efficiency, compared to the long (L) form, thereby decreasing serotonin transporter expression and serotonin uptake. We genotyped the 5-HTT gene polymorphism in a set of alcohol-dependent Italian subjects and controls by PCR. Methods. Genomic DNA was extracted from 3 ml of peripheral blood by the salting out technique and amplified with the following oligonucleotide primers flanking the 5-HTT polymorphic region: 5-HTT F 5-GGCGTTGCCGCTCTGAATTGC- 3 and 5-HTT R 5-GAGGGACTGAGCTGGACAACCCAC- 3. PCR amplification was carried out in a final volume of 50 μl containing 100 ng DNA and 2.5 mM deoxyribonucleotides, 0.1 μg of sense and antisense primers, 10 mM Tris-HCl (pH 8.3), 50 mM KCl, 1.5 mM MgCl2, 5% DMSO, and 1 U of Promega Taq DNA polymerase. Annealing was carried out at 62◦C for 30 s, extension at 72◦C for 1 min for 35 cycles. Results. The frequency of the short allele of the 5-HTT gene is significantly higher among patients compared to control subjects (84% vs 43%). Conclusions. These results provide evidence that alcohol abuse disorders are associated with a genetic variant for 5-HT transmission.