Variability of the tryptophan hydroxylase gene: Study in victims of violent suicide

University of Zagreb, Zagrabia, Grad Zagreb, Croatia
Psychiatry Research (Impact Factor: 2.47). 04/2005; 134(1):67-73. DOI: 10.1016/j.psychres.2004.04.011
Source: PubMed


Tryptophan hydroxylase (TPH), the enzyme controlling serotonin synthesis, is considered to be a potential contributor to the biological substrate of suicide. The association of the promoter (-7065CT) and intron 7 (218AC) polymorphisms, and the related haplotype, of the Tph1 gene with suicidal behavior was investigated in a sample of 160 victims of violent suicide and 284 healthy controls. All individuals were males of Croatian (Slavic) origin. Allele frequencies of both polymorphisms in Croatian controls were similar to control values reported for other European populations. Alleles at the two loci demonstrated highly significant linkage disequilibrium. No differences between controls and victims for the Tph1 genetic variation, either at single loci, or at a haplotypic level, were demonstrated, albeit there was a tendency, not reaching statistical significance, towards an increase of the intron 7CC genotype in the suicide group. Negative association results on the individual Tph1 loci, in accordance with the majority of previous reports, confirmed the lack of their major effect also in the Slavic ethnicity. Haplotypic results, on the other hand, opposing the previous positive finding, point to the possible influence of ethnicity (or gender) on the association between the Tph1 gene polymorphism and suicide.

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Available from: Jasminka Stefulj, Nov 20, 2014
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    • "Thus, variations in TPH genes have prompted several researchers to conduct association genetic studies on TPH single-nucleotide polymorphisms (SNPs) [15]. Of the several different polymorphisms studied, most researches have focused on two SNPs in TPH1 [16]. The first polymorphism, A779C (rs1799913), was identified by single strand conformational analysis and comes mainly in two alternative forms or alleles TPH 779A and TPH 779C, referred to as U and L, respectively [17]. "
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    ABSTRACT: Background It is widely acknowledged that suicidal behavior (SB) has a genetic influence. As a consequence, molecular genetic studies have been mostly conducted on serotonergic genes. One of the most promising candidate genes of this system is tryptophan hydroxylase (TPH). Although there have been several positive studies associating TPH genes and SB, the evidence is not entirely consistent. Therefore, we performed a meta-analysis to gain a better understanding into this issue. Methods The meta-analysis was conducted with 37 articles of genetic association studies of TPH-1 (A218C and A779C) and TPH2 (G-703 T, A-473 T and G19918A) genes. To analyze the association of these variants with SB we used the following models: allelic, additive, dominant and recessive. In addition, we performed a sub-group analysis by Caucasian and Asian populations using the same four models. Results TPH-1 gene variants showed a positive significant association with SB, but only in the fixed effects models. With regard to TPH-2 gene variants we could not find an association with SB. Conclusions The study provides evidence that A218C/A779C TPH-1 variants may be a risk factor to manifest SB at the clinical level, which is in agreement with previously reported meta-analyses. With regard to G-703 T/A-473 T/G19918A TPH-2 variants, our up-to-date meta-analysis could not detect any significant association between those genetic variants and SB. However, these results should be interpreted with caution since further studies need to be undertaken using larger sample sizes in different ethnic populations to confirm our findings.
    Full-text · Article · Jul 2014 · BMC Psychiatry
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    • "In a meta-analysis from 2006, an increased proportion of the A-allele was found in cases with suicidal behaviour compared with control individuals (Li and He, 2006). But several studies on completed suicides did not find a positive association to this marker (Bennett et al., 2000; Ohtani et al., 2004; Ono et al., 2000; Stefulj et al., 2005). In accordance with these studies, we did not observe any significant association between rs1800532 in TPH1 and completed suicide. "
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    ABSTRACT: INTRODUCTION: Strong evidence demonstrates a genetic susceptibility to suicidal behaviour and a relationship between suicide and mental disorders. The aim of this study was to test for association between suicide and five selected genetic variants, which had shown association with suicide in other populations. METHOD: We performed a nationwide case-control study on all suicide cases sent for autopsy in Denmark between the years 2000 and 2007. The study comprised 572 cases and 1049 controls and is one of the largest genetic studies in completed suicide to date. The analysed markers were located within the Serotonin Transporter (SLC6A4), Monoamine Oxidase-A (MAOA) and the Tryptophan Hydroxylase I and II (TPH1 and TPH2) genes. RESULTS: None of the genetic markers within SLC6A4, MAOA, TPH1 and TPH2 were significantly associated with completed suicide or suicide method in the basic association tests. Exploratory interaction test showed that the minor allele of rs1800532 in TPH1 has a protective effect for males younger than 35 years and females older than 50 years, whereas for the oldest male subjects, it tended to be a risk factor. We also observed a significant interaction between age-group and the 5-HTTLPR genotype (with and without rs25531) in SLC6A4. The long allele or high expression allele tends to have a protective effect in the middle age-group. LIMITATION: We only analysed a limited number of genetic variants. CONCLUSION: None of the analysed variants are strong risk factors. To reveal a better understanding of the genes involved in suicide, we suggest future studies should include both genetic and non-genetic factors.
    Full-text · Article · Jan 2013 · Journal of Affective Disorders
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    ABSTRACT: Untersuchung zu single-nucleotid-polymorphismen (SNPs) der Serotoninrezeptoren 5-HT2A, 5-HT3A, des Neurotrophins BDNF und des Enzyms Tryptophanhydroxlase auf deren Korrelation mit Migräne mit und ohne Aura. Correlation between single nucleotide polymorphisms in genes of serotonergic 5-HT2A and 5-HT3A-receptors, brain derived neurotropic factor and Tryptophanhydroxylase with migraine with and without aura phenomenon.
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