Stress Upregulates TPH1 but not TPH2 mRNA in the Rat Dorsal Raphe Nucleus: Identification of Two TPH2 mRNA Splice Variants
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Serotonin is implicated in stress-related psychopathologies. Two isoforms of the rate-limiting enzyme of serotonin biosynthesis, tryptophan hydroxylase, TPH1 and TPH2, are known. We show here that in the rat dorsal raphe nucleus (DRN), the nucleus that contains the highest number of 5-HT neurons in the brain, TPH1 mRNA reveals a low level of expression but is detectable both by quantitative real-time PCR and in situ hybridization whereas in the pineal gland (PiG), TPH1 mRNA is strongly expressed. To examine effects of stress on TPH expression we exposed male Wistar rats to daily restraint stress for 1 week. As shown by quantitative real-time PCR, TPH1 mRNA is 2.5-fold upregulated by the stress in DRN but not in PiG. Using 3′-RACE, we identified two TPH2 mRNA splice variants in the rat DRN which differ in the length of their 3′-untranslated regions (UTRs). TPH2b (with a short 3′-UTR) is the predominant variant in the DRN, whereas TPH2a (with a longer 3′-UTR) shows a low abundance in this nucleus. In the PiG, only TPH2b is detectable revealing a low level of expression. Expression of both TPH2 splice variants is not affected by stress, neither in DRN nor in the PiG. These data indicate that TPH1 in the serotonergic neurons of the DRN might be relevant for stress-induced psychopathologies.
KeywordsSerotonin Tryptophan hydroxylase Splice variant Stress Affective disorders Pineal gland
3′-Rapid amplification of cDNA ends
5-hydroxytryptamine or serotonin
Dorsal raphe nucleus
Nashat Abumaria was in part funded by the DFG-Research Center Molecular Physiology of the Brain (CMPB) at the University of Göttingen. Adema Ribic is supported by a European Community fellowship for Neuroscience Early Stage Research Training (NEUREST), Göttingen, and is enrolled in the MSc/PhD Program for Molecular Biology at the University of Göttingen. Christoph Anacker is a fellow and grant recipient of the MSc/PhD Program Neurosciences at the University of Göttingen. We are grateful to Dr. B. Czeh for helpful discussions and to the excellent technical assistance of A. Hoffmann.
- Brown SM, Peet E, Manuck SB, Williamson DE, Dahl RE, Ferrell RE, Hariri AR (2005) A regulatory variant of the human tryptophan hydroxylase-2 gene biases amygdala reactivity. Mol Psychiatry 10: 805, 884–888Google Scholar
- Clark JA, Flick RB, Pai LY et al (2007) Glucocorticoid modulation of tryptophan hydroxylase-2 protein in raphe nuclei and 5-hydroxytryptophan concentrations in frontal cortex of C57/Bl6 mice. Mol Psychiatry; doi: 10.1038/sj.mp.4002041
- Lowry CA, Rodda JE, Lightman SL, Ingram CD (2000) Corticotropin-releasing factor increases in vitro firing rates of serotonergic neurons in the rat dorsal raphe nucleus: evidence for activation of a topographically organized mesolimbocortical serotonergic system. J Neurosci 20:7728–7736PubMedGoogle Scholar
- Zhou Z, Roy A, Lipsky R, Kuchipudi K, Zhu G, Taubman J, Enoch MA, Virkkunen M, Goldman D (2005) Haplotype-based linkage of tryptophan hydroxylase 2 to suicide attempt, major depression, and cerebrospinal fluid 5-hydroxyindoleacetic acid in 4 populations. Arch Gen Psychiatry 62:1109–1118PubMedCrossRefGoogle Scholar