Association study of the TPH2 gene with major depressive disorder in the han Chinese population

Background and Objectives: Tryptophan hydroxylase 2 (TPH2) catalyzes the rate-limiting step in serotonin biosynthesis in the nervous system. Several variants of human TPH2 have been reported to be associated with a spectrum of neuropsychiatric disorders such as unipolar major depression, bipolar disorder and suicidality etc. Recent studies suggested that two variants (T212 and A375) in the exon 7 and exon 9 were associated with major depressive disorder (MDD). Methods: To replicate these findings, two polymorphisms located in exons 7 and 9 of TPH2 (rs7305115 and rs4290270, respectively) were analysed by DNA sequence in the case-control sample study in 191 MDD and 191 healthy volunteers. Statistical analyses were carried out using the program SPSS. The comparison of allele and genotype frequencies of each polymorphism between case and control groups was carried out on the online software SHEsis. All subjects were unrelated southern Han Chinese. Results: No difference was observed on the allelic or genotypic distribution of TPH2 gene polymorphisms between the groups. However, the two-marker haplotype covering components T212 (rs7305115) A and A375 (rs4290270) T were observed to have a significantly protective effect MDD in female (corrected p = 0.0032; OR = 0.241[95% CI = 0.099-0.587]). Conclusions: The results suggest that TPH2 might be associated with a lower risk of female MDD. However, confirmatory studies in independent samples are needed.