Characterization of a functional polymorphism in the 3' UTR of SLC6A4 and its association with drinking intensity.
BACKGROUND
The propensity for severe drinking is hypothesized to be regulated by differential expression of serotonin transporter gene (SLC6A4) in the human brain. The SLC6A4 promoter region 5-HTTLPR has been examined previously as a candidate polymorphic variant associated with severe drinking. In this study, we investigated whether other SLC6A4 single nucleotide polymorphisms (SNPs) are associated with drinking intensity among treatment-seeking alcoholics and whether these polymorphic variants result in differential SLC6A4 expression levels.


METHODS
We analyzed associations of drinking intensity in 275 (78.5% male) treatment-seeking alcoholics of Caucasian and Hispanic origin, with 6 SLC6A4 polymorphisms. Next, to examine the functionality of the SNP that showed a significant association with drinking intensity, we transfected the 2 alleles of rs1042173 into HeLa cell cultures and measured serotonin transporter mRNA and protein expression levels by using qRT-PCR and western blotting techniques.


RESULTS
One of the 6 polymorphisms we examined, rs1042173 in the 3' untranslated region (3'-UTR) of SLC6A4, showed a significant association with drinking intensity. The G allele carriers for rs1042173 were associated with significantly lower drinking intensity (p = 0.0034) compared to T-allele homozygotes. In HeLa cell cultures, the cells transfected with G allele showed a significantly higher mRNA and protein levels than the T allele-transfected cells.


CONCLUSIONS
These findings suggest that the allelic variations of rs1042173 affect drinking intensity in alcoholics possibly by altering serotonin transporter expression levels. This provides additional support to the hypothesis that SLC6A4 polymorphisms play an important role in regulating propensity for severe drinking.
Seneviratne
Chamindi
C
Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, 1670 Discovery Drive, Charlottesville, VA 22911, USA.
Huang
Weihua
W
Ait-Daoud
Nassima
N
Li
Ming D
MD
Johnson
Bankole A
BA
D020413:3' Untranslated Regions / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000428:Alcohol Drinking / Q000235:genetics* / Q000523:psychology*; D000437:Alcoholism / Q000235:genetics* / Q000523:psychology*; D000483:Alleles; D015153:Blotting, Western; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D003720:Densitometry; D005260:Female; D005838:Genotype; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D050486:Serotonin Plasma Membrane Transport Proteins / Q000096:biosynthesis / Q000235:genetics*; D014162:Transfection; D055815:Young Adult
D020413:3' Untranslated Regions; D012333:RNA, Messenger; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; D004247:DNA