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Much research has implicated the striatum in motor learning, but the underlying mechanisms have not been identified. Although NMDA receptor (NMDAR)-dependent long-term potentiation has been observed in the striatum, its involvement in motor learning remains unclear. To examine the role of striatal NMDAR in motor learning, we created striatum-specific NMDAR1 subunit knockout mice, analyzed the striatal anatomy and neuronal morphology of these mice, evaluated their performance on well established motor tasks, and performed electrophysiological recordings to assay striatal NMDAR function and long-term synaptic plasticity. Our results show that deleting the NMDAR1 subunit of the NMDAR specifically in the striatum, which virtually abolished NMDARmediated currents, resulted in only small changes in striatal neuronal morphology but severely impaired motor learning and disrupted dorsal striatal long-term potentiation and ventral striatal long-term depression.long-term potentiation ͉ NMDA receptor ͉ knockout ͉ RGS9-2

Mutations of epsilon-sarcoglycan gene (SGCE) have been implicated in myoclonus-dystonia (M-D), a movement disorder. To determine the pathophysiology of M-D, we produced Sgce knockout mice and found that the knockout mice exhibited myoclonus, motor impairments, hyperactivity, anxiety, depression, significantly higher levels of striatal dopamine and its metabolites, and an inverse correlation between the dopamine and serotonin metabolites. The results suggest that the diverse symptoms associated with M-D are indeed resulted from a single SGCE gene mutation that leads to alterations of dopaminergic and serotonergic systems. Therefore, antipsychotic agents and serotonin reuptake inhibitors may offer potential benefits for M-D patients.

DYT1 dystonia is a primary generalized early-onset torsion dystonia caused by mutations in DYT1 that codes for torsinA and has an autosomal dominant inheritance pattern with approximately 30% penetrance. Abnormal activity in the pallidal-thalamic-cortical circuit, especially in the globus pallidus internus, is the proposed cause of dystonic symptoms. However, recent neuroimaging studies suggest significant contribution of the cerebral cortex. To understand the contribution of the cerebral cortex to dystonia, we produced cerebral cortex-specific Dyt1 conditional knockout mice and analysed their behaviour. The conditional knockout mice exhibited motor deficits and hyperactivity that mimic the reported behavioural deficits in Dyt1 DeltaGAG knockin heterozygous and Dyt1 knockdown mice. Although the latter two mice exhibit lower levels of dopamine metabolites in the striatum, the conditional knockout mice did not show significant alterations in the striatal dopamine and its metabolites levels. The conditional knockout mice had well-developed whisker-related patterns in somatosensory cortex, suggesting formations of synapses and neural circuits were largely unaffected. The results suggest that the loss of torsinA function in the cerebral cortex alone is sufficient to induce behavioural deficits associated with Dyt1 DeltaGAG knockin mutation. Developing drugs targeting the cerebral cortex may produce novel medical treatments for DYT1 dystonia patients.

The DYT1 gene containing a trinucleotide deletion (ΔGAG) is linked to early-onset dystonia, a neurological movement disorder of involuntary muscle contractions. To understand Dyt1's contribution to dystonia, we produced and analyzed Dyt1 knockdown (KD) mice that expressed a reduced level of torsinA protein encoded by Dyt1. Knockdown mice exhibited deficits in motor control and a decreased trend in dopamine with a significant reduction in 3,4-dihydroxyphenylacetic acid. These alterations are similar to those displayed by previously reported Dyt1 ΔGAG knockin heterozygous mice, suggesting that the partial loss of torsinA function contributes to the pathology of the disease. KeywordsDyt1; torsinA; dystonia; knockdown; Tor1A; Dyt1 ΔGAG A trinucleotide deletion (ΔGAG) in the DYT1 gene is found in a majority of patients with Oppenheim's early-onset dystonia, a neurological disorder of uncontrollable muscle contractions (Ozelius et al., 1997). DYT1 codes for torsinA protein, and the ΔGAG deletion removes a glutamic acid (ΔE) from the protein. The role of mutant torsinA in the development of dystonia is unknown, but possible functions of normal torsinA were reported to include its involvement in cytoskeletal dynamics, nuclear membrane formation, and neuroprotection (Kuner et al., 2003;Bragg et al., 2004;Gonzalez-Alegre & Paulson, 2004;Goodchild & Dauer, 2004;Shashidharan et al., 2004;Hewett et al., 2006;Kock et al., 2006). Also unknown is the nature of the genetic mutation in torsinA, an important aspect of the pathophysiology of dystonia that may affect the development of genetic-based therapeutics.The ΔGAG mutation of DYT1 has been speculated to work through a toxic-gain-of-function mechanism by reports of protein aggregates caused by an overexpression of mutant torsinA in cultured cells and Drosophila (Hewett et al., 2000;Kustedjo et al., 2000;Koh et al., 2004). Also, in patient tissues and two mouse models, an overexpression transgenic and our Dyt1 ΔGAG knockin (Dyt1 ΔGAG) mouse lines, aggregates containing torsinA and ubiquitin were found primarily in the brainstem, even though torsinA is widely expressed throughout the brain Dang et al., 2005;Shashidharan et al., 2005). In contrast, other published findings have suggested that ΔGAG causes a loss of normal protein function (Torres et al., 2004;Goodchild et al., 2005). For example, nuclear envelope abnormalities were noted * To whom correspondence and proofs should be addressed. Yuqing Li, 3347 Beckman Institute, 405 N. Mathews Ave., Urbana, Illinois, 61801, Tel.:217-333-4002, Fax: 217-244-1726, E-mail: y-li4@uiuc.edu.. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all l...

DYT1 early-onset generalized torsion dystonia is an inherited movement disorder associated with mutations in DYT1 that codes for torsinA protein. The most common mutation seen in this gene is a trinucleotide deletion of GAG. We previously reported a motor control deficit on a beam-walking task in our Dyt1 ΔGAG knock-in heterozygous mice. In this report we show the reversal of this motor deficit with the anticholinergic trihexyphenidyl (THP), a drug commonly used to treat movement problems in dystonia patients. THP also restored the reduced corticostriatal long-term depression (LTD) observed in these mice. Corticostriatal LTD has long been known to be dependent on D2 receptor activation. In this mouse model, striatal D2 receptors were expressed at lower quantities in comparison to wild-type mice. Furthermore, the mice were also partially resistant to FPL64176, an agonist of L-type calcium channels that have been previously reported to cause severe dystonic-like symptoms in wild-type mice. Our findings collectively suggest that altered communication between cholinergic interneurons and medium spiny neurons is responsible for the LTD deficit and that this synaptic plasticity modification may be involved in the striatal motor control abnormalities in our mouse model of DYT1 dystonia.

DYT1 dystonia, a common and severe primary dystonia, is caused by a 3-bp deletion in TOR1A which encodes torsinA, a protein found in the endoplasmic reticulum. Several cellular functions are altered by the mutant protein, but at a systems level the link between these and the symptoms of the disease is unclear. The most effective known therapy for DYT1 dystonia is use of anticholinergic drugs. Previous studies have revealed that in mice, transgenic expression of human mutant torsinA under a non-selective promoter leads to abnormal function of striatal cholinergic neurons. To investigate what pathological role torsinA plays in cholinergic neurons, we created a mouse model in which the Dyt1 gene, the mouse homolog of TOR1A, is selectively deleted in cholinergic neurons (ChKO animals). These animals do not have overt dystonia, but do have subtle motor abnormalities. There is no change in the number or size of striatal cholinergic cells or striatal acetylcholine content, uptake, synthesis, or release in ChKO mice. There are, however, striking functional abnormalities of striatal cholinergic cells, with paradoxical excitation in response to D2 receptor activation and loss of muscarinic M2/M4 receptor inhibitory function. These effects are specific for cholinergic interneurons, as recordings from nigral dopaminergic neurons revealed normal responses. Amphetamine stimulated dopamine release was also unaltered. These results demonstrate a cell-autonomous effect of Dyt1 deletion on striatal cholinergic function. Therapies directed at modifying the function of cholinergic neurons may prove useful in the treatment of the human disorder.

Rapid-onset dystonia with parkinsonism (RDP) or DYT12 dystonia is a rare form of primary, generalized dystonia. Patients do not present with any symptoms until triggered by a physiological stressor. Within days, patients will show both dystonia and Parkinson's disease. Missense mutations resulting in a loss of function in the ATP1A3 gene have been identified as the cause of RDP. ATP1A3 encodes the α3 subunit of the Na + /K + -ATPase in neurons and cardiac cells. We have previously created a line of mice harboring a point mutation of the Atp1a3 gene (mouse homolog of the human ATP1A3 gene) that results in a loss of function of the α3 subunit. The Atp1a3 mutant mice showed hyperactivity, spatial learning and memory deficits, and increased locomotion induced by methamphetamine. However, the full spectrum of the motor phenotype has not been characterized in the Atp1a3 mutant mice and it is not known whether triggers such as restraint stress affect the motor phenotype. Here, we characterized the motor phenotype in normal heterozygous Atp1a3 mutant mice and heterozygous Atp1a3 mutant mice that have been exposed to a restraint stress. We found that this type of trigger induced significant deficits in motor coordination and balance in the mutant mice, characteristic of other genotypic dystonia mouse models. Furthermore, stressed mutant mice also had a decreased thermal sensitivity and alterations in monoamine metabolism. These results suggest that the Atp1a3 mutant mouse models several characteristics of RDP and further analysis of this mouse model will provide great insight into pathogenesis of RDP.