Genome-wide association data provide further support for an association between 5-HTTLPR and major depressive disorder

Abstract

Background: Dysfunctions of serotonergic neurotransmission are supposed to be involved in the pathogenesis of psychiatric disorders such as major depressive disorder (MDD). The concentration of serotonin (5-hydroxytryptamine, 5-HT) in the synaptic cleft is essentially regulated by the 5-HT transporter (5-HTT). A length polymorphism repeat in the 5-HTT promoter region, termed 5-HTTLPR, has been commonly investigated for an association with psychiatric disorders.

Methods: Genotyping of the 5-HTTLPR is time-consuming and technically challenging. Recently, a two-SNP haplotype was identified that tags the 5-HTTLPR at r(2)=0.775. This allows extraction of 5-HTTLPR genotype information from large genome-wide association study (GWAS) data sets. In the present study we performed haplotype analysis using a German GWAS case-control dataset to test for an association between MDD and the two-SNP tagging haplotype for 5-HTTLPR.

Results: We detected a significant association between the TA haplotype (tagging the S-allele of the 5-HTTLPR) and MDD. Our result is consistent with previous findings of an association between the 5-HTTLPR S-allele and MDD.

Limitations: Using the two-SNP tagging haplotype did not allow testing of the tri-allelic genotype (but only the two-allelic genotype). This and the fact that the haplotype tags the 5-HTTLPR with an imperfect linkage disequilibrium of r(2)=0.775 may lead to some loss of power.

Conclusions: Our results provide further support for an involvement of the 5-HTTLPR in MDD and represent the first example of demonstrating association between MDD and the S-allele of the length polymorphism repeat using common SNP information from SNP-array data.