TPH gene may be associated with suicidal behavior, but not with schizophrenia in the Korean population

Tryptophan hydroxylase (TPH) is a rate-limiting enzyme in the biosynthesis of serotonin. This study was designed to examine whether A218C polymorphism, which has been identified in intron 7 of the TPH gene, may be associated with schizophrenia or the suicidal behavior of schizophrenics in the Korean population. TPH genotypes were determined in DNA samples from 217 schizophrenics and 236 healthy volunteers. Among the schizophrenic group, 27 patients had a history of suicidal behavior. Genomic DNA was amplified by a polymerase-chain-reaction-based method and restricted by Nhel. A218C polymorphism was associated with a history of suicidal behavior in schizophrenics. This finding suggests that the TPH gene or a gene in its vicinity may influence suicidal behavior in schizophrenics. However, genotypic and allelic distrubutions of this polymorphism did not significantly differ between schizophrenics and controls.