Effect of tryptophan hydroxylase-2 gene polymorphism G-703 T on personality in a population representative sample

• The TPH2 G-703T polymorphism has an effect on personality traits in adolescents.
• TPH2 T/T homozygotes have lower Neuroticism, and higher Conscientiousness and Extraversion.
• The effect of TPH2 genotype on Conscientiousness is evident only in 5-HTTLPR S-allele carriers.

The tryptophan hydroxylase-2 gene (TPH2) is coding for the key enzyme of serotonin (5-HT) synthesis in the brain and has been associated with a number of psychiatric conditions. A functional variation in the TPH2 gene (G-703T, rs4570625) has been found to affect anxiety-related personality; however, information is very limited regarding the five factor model (FFM) personality traits. We have examined the association of the TPH2 G-703T polymorphism with FFM personality traits, and the possible modulation by the functional variation in the serotonin transporter gene (5-HTTLPR) in a large longitudinal population representative sample.The FFM personality traits were assessed in both birth cohorts of the Estonian Children Personality Behaviour and Health Study at ages 15 (n = 742) and 18 (n = 834).Significant association of the TPH2 genotype with Neuroticism and Conscientiousness was found at age 15, and with Extraversion and Conscientiousness at age 18. Participants with the T/T genotype scored significantly lower on Neuroticism and higher on Conscientiousness and Extraversion scales. In addition, a gene × gene interaction effect on Conscientiousness was revealed: the TPH2 genotype effect was evident only in the 5-HTTLPR S-allele carriers.These results provide further evidence on the possible role of genetic variations in 5-HT neurotransmission on development of personality traits, and suggest a functional interaction between two key proteins in the 5-HT-ergic system.