Stress Upregulates TPH1 but not TPH2 mRNA in the Rat Dorsal Raphe Nucleus: Identification of Two TPH2 mRNA Splice Variants

Abstract

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.

Differential lipopolysaccharide-induced immune alterations in the hippocampus of two mouse strains: Effects of stress

“…These alterations are interesting given the previous findings in relation to stress-induced alterations in Tph mRNA. Previously, it has been shown that Tph1 is upregulated in the brainstem following stress (Chamas and Sabban, 2002;Abumaria et al, 2008). Additionally, Tph1 and not Tph2 is the isoform associated with the onset of stressinduced depression (Gizatullin et al, 2008).…”

A Genetically Defined Morphologically and Functionally Unique Subset of 5-HT Neurons in the Mouse Raphe Nuclei

“…We examined which Tph isoforms are expressed. Tph2 is the dominant isoform in the brain, but Tph1 has also been found in a raphe subpopulation during postnatal development (Nakamura et al, 2006), or in adaptive pathological circumstances such as restraint stress in rats (Abumaria et al, 2008). Tph1 expression was detected with RT-PCR in the raphe in control and Pet1 knock-out mice.…”

Serotonin and Blood Pressure Regulation

“…TPH1 is expressed primarily in peripheral tissues, whereas TPH2 is expressed primarily in the central nervous system . Splice variants of TPH2 have been observed (Abumaria et al, 2008). This enzyme, dependent on the important cofactor tetrahydrobiopterin, commits tryptophan to the fate of 5-HT by converting tryptophan to 5-hydroxytryptophan (Kuhn 1999).…”