We report the discovery of a mutation in the THAP1 gene in three Amish-Mennonite families with mixed-onset primary torsion dystonia (also known as DYT6 dystonia). Another mutation in a German family with primary torsion dystonia suggests that THAP1 mutations also cause dystonia in other ancestry groups. We demonstrate that the missense mutation impairs DNA binding, suggesting that transcriptional dysregulation may contribute to the phenotype of DYT6 dystonia.

The 5-hydroxytryptamine type 2A (5-HT 2A ) receptor and the 5-HT 2C receptor are closely related members of the G-protein-coupled receptors activated by serotonin that share very similar pharmacological profiles and cellular signaling pathways. These receptors express a canonical class I PDZ ligand (SXV) at their C-terminal extremity. Here, we have identified proteins that interact with the PDZ ligand of the 5-HT 2A and 5-HT 2C receptors by a proteomic approach associating affinity chromatography using immobilized synthetic peptides encompassing the PDZ ligand and mass spectrometry. We report that both receptor C termini interact with specific sets of PDZ proteins in vitro. ) is a major neurotransmitter that is involved in numerous functions of the mammalian central nervous system. These functions are mediated by a large number of receptors. Except for the 5-HT 3 receptor, which is a ligand-gated channel, all 5-HT receptors belong to the Gprotein-coupled receptor (GPCR) superfamily. Among the GPCRs activated by 5-HT, the 5-HT 2 receptor family, namely the 5-HT 2A , the 5-HT 2B , and the 5-HT 2C receptors, continues to raise particular interest. Indeed, they are involved in multiple physiological functions such as the control of endocrine secretion, motor behavior, mood, pain, sleep, thermoregulation, and appetite (1). Moreover, a large number of psychoactive drugs, including non-classical antipsychotic drugs, hallucinogens, anxiolytics, and anti-depressants, mediate their action at least in part through activation of 5-HT 2 receptors (1-4).Among the 5-HT 2 receptor family, the 5-HT 2A and the 5-HT 2C receptor are widely distributed in the central nervous system, whereas the 5-HT 2B receptor is sparse. The 5-HT 2A and the 5-HT 2C receptors share the highest degree of sequence homology (about 50% overall sequence identity). Thus, it is not surprising that these receptors have very similar pharmacological profiles and that only a few selective ligands are available. Initial studies of 5-HT 2A and 5-HT 2C receptor signaling showed that both receptors activate phosphatidyl inositol hydrolysis. However, some differences in signal transduction characteristics of these receptors have been reported (5, 6). In NIH3T3 cells expressing the 5-HT 2C receptor, agonist-independent activity was much more elevated than that measured in cells expressing the same density of 5-HT 2A receptors (7). This indicates that the 5-HT 2A receptor has lower intrinsic ability to adopt an active conformation than does the 5-HT 2C receptor. Different mechanisms of desensitization for the 5-HT 2A and 5-HT 2C receptor systems have also been described. In Chinese hamster ovary cells, agonist-induced desensitization of the 5-HT 2A receptor-mediated phospholipase C activation is inhibited by inhibitors of protein kinase C and Ca 2ϩ -calmodulin-dependent protein kinase II (8). In contrast, the 5-HT 2C receptormediated response is insensitive to these inhibitors. Moreover, the desensitization of the 5-HT 2C receptor system but not that of the 5-HT 2A r...

Despite the importance of 5-hydroxytryptamine (5-HT) 2C (serotonin) receptors in the control of depressive states, actions of antidepressants at these receptors remain poorly characterized. This issue was addressed both in human embryonic kidney (HEK)-293 cells coexpressing unedited human 5-HT 2CINI receptors and G␣ q protein and in cultured mouse cortical neurons. Indicative of constitutive activity, the inverse agonist SB206,553 decreased basal inositol phosphate (IP) production in HEK-293 cells. The tetracyclic antidepressants mirtazapine and mianserin likewise suppressed basal IP formation. Conversely, the tricyclics amitriptyline and clomipramine, the m-chlorophenylpiperazine derivatives trazodone and nefazodone, and the 5-HT reuptake inhibitors fluoxetine and citalopram were inactive alone, although they blocked 5-HT-induced IP production. Inverse agonist actions of 5-methyl-1-(3-pyridylcarbamoyl)-1,2,3,5-tetrahydropyrrolo[2,3-f]indole (SB206,553) and mirtazapine were abolished by the neutral antagonist 6-chloro-5-methyl-1-[6-(2-methylpyridin-3-yloxy)pyridin-3-ylcarbamoyl]indoline (SB242,084), which was inactive alone. As assessed by confocal microscopy and enzyme-linked immunosorbent assay, prolonged treatment of HEK-293 cells with SB206,553, mirtazapine, or mianserin, but not the other antidepressants, enhanced cell surface expression of 5-HT 2C receptors: 5-HT-induced IP production was also increased, and both these actions were blocked by SB242,084. Cortical neurons were shown by reverse transcription-polymerase chain reaction to predominantly express constitutively active 5-HT 2C receptor isoforms. Prolonged pretreatment with SB206,553 or mirtazapine triggered an otherwise absent 5-HT-induced elevation in cytosolic Ca 2ϩ concentrations. SB242,084, which was inactive alone, abolished these effects of SB206,553 and mirtazapine. In conclusion, the tetracyclic antidepressants mirtazapine and mianserin, but not other clinically established antidepressants, suppress constitutive activity at recombinant and native 5-HT 2C receptors. The clinical significance of inverse agonist versus neutral antagonist properties both during and after drug administration will be of interest to elucidate.5-Hydroxytryptamine 2C (serotonin) receptors continue to attract considerable interest in view of their broad physiological role and implication in the actions of psychotropic agents (Giorgetti and Tecott, 2004;Millan, 2005Millan, , 2006. It is noteworthy that they show species-and tissue-specific patterns of adenosine-to-inosine mRNA editing, leading to amino acid substitutions within the intracellular loop 2 and the generation of numerous isoforms, ranging from unedited P.M. was supported by grants

Primary dystonia is a movement disorder characterized by sustained muscle contractions and in which dystonia is the only or predominant clinical feature. TOR1A (DYT1) and the transcription factor THAP1 (DYT6) are the only genes identified thus far for primary dystonia. Using electromobility shift assays and chromatin immunoprecipitation (ChIP)-qPCR, we demonstrate a physical interaction between THAP1 and the TOR1A promoter that is abolished by pathophysiologic mutations. Our findings provide the first evidence that causative genes for primary dystonia intersect in a common pathway and raise the possibility of developing novel therapies targeting this pathway.

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