No association between a TPH2 promoter polymorphism and mood disorders or monoamine turnover

BACKGROUND: Tryptophan hydroxylase (TPH) is the rate-limiting enzyme in serotonin synthesis. TPH2 is a recently discovered isoform that is expressed predominantly in serotonin neurons. Associations are reported of TPH2 polymorphisms with MDD, bipolar disorder and suicidal behavior. This study examines a single nucleotide polymorphism in the putative promoter region of the TPH2 gene. METHODS: One hundred nine bipolar, 324 major depressive disorder, and 130 healthy volunteers were genotyped for the rs4131347 (-C8347G) promoter SNP. Association was assessed with diagnosis, suicide attempt status, severity of psychopathology and cerebrospinal fluid monoamine metabolite levels of 5-HIAA, HVA, and MHPG. General linear models and logistic regression tested the effect of genotype*childhood abuse interactions on psychopathology severity and suicide attempt. RESULTS: There was no association between genotype and either mood disorder, suicide attempt status, psychopathology severity or CSF monoamine metabolite levels. CONCLUSIONS: No association was detected between the rs4131347 (-C8347G) SNP in the promoter region of the TPH2 gene and mood disorders, suicidal behavior or monoamine function.