The human serotonin transporter gene polymorphism--basic research and clinical implications.

Mood, emotion, and cognition are modulated by the serotonergic midbrain raphe system, which seems to be involved in the pathogenesis of psychiatric disorders like those of the affective spectrum. Since a dysregulation of serotonin transporter expression might be important in the course of those disorders, we isolated and cloned the 5'-regulatory region of the serotonin transporter gene, which is inducible by cAMP- and PKC-depended signal transduction pathways. Systematic screening for length variations and functional promoter analyses revealed a genetic polymorphism with allelic variation in transcriptional activity and protein expression. This 5-HTT gene polymorphism comprises a tandemly repeated sequence in the 5'-regulatory promoter region of the serotonin transporter gene. Recent population association studies demonstrated the 5-HTT gene promoter polymorphism accounting for 4-5% of population variation of anxiety-related behavioral traits.