No Human Tryptophan Hydroxylase-2 Gene R441H Mutation in a Large Cohort of Psychiatric Patients and Control Subjects

Background It was recently reported that a rare functional variant, R441H, in the human tryptophan hydroxylase-2 gene (hTPH2) could represent an important risk factor for unipolar major depression (UP) since it was originally found in 10% of UP patients (vs. 1.4% in control subjects). Methods We explored the occurrence of this variation in patients with affective disorders (n = 646), autism spectrum disorders (n = 224), and obsessive-compulsive disorder (OCD) (n = 201); in healthy volunteers with no psychiatric disorders (n = 246); and in an ethnic panel of control individuals from North Africa, Sub-Saharan Africa, India, China, and Sweden (n = 277). Results Surprisingly, we did not observe the R441H variant in any of the individuals screened (3188 independent chromosomes). Conclusions Our results do not confirm the role of the R441H mutation of the hTPH2 gene in the susceptibility to UP. The absence of the variant from a large cohort of psychiatric patients and control subjects suggests that the findings reported in the original study could be due to a genotyping error or to stratification of the initial population reported. Additional data by other groups should contribute to the clarification of the discrepancy between our results and those previous published.