Purines are a class of ubiquitous molecules required for fundamental processes in all cells. Purines are derived from two major sources: de novo synthesis, and salvage of preformed purine bases. The current studies provide evidence that the relative contributions of these two pathways change substantially as human induced pluripotent stem cells (iPSCs) differentiate into neurons. Expression of all genes in the de novo synthesis pathway decreases as pluripotent cells differentiate into neurons, but expression of the salvage pathway gene HPRT1 increases. This selective rise in HPRT1 gene expression corresponds with increased activity of its associated enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt). Similar changes in the expression of genes for the de novo pathway genes and for HPRT1 were found in a public database of gene expression for human brain development. The consequences of eliminating HGprt-mediated recycling were also evaluated in human-derived iPSCs with null HPRT1 mutations and stock iPSC lines that have been gene-edited to contain a null HPRT1 mutation. The absence of HGprt had no apparent impact on early neuronal differentiation, through 60 days of in vitro differentiation. Biochemical studies of purine content showed that that the absence of HGprt had little impact on intracellular purines, although large amounts of its substrate (hypoxanthine) accumulated in the tissue culture medium. Neurons derived from iPSCs without HGprt appeared morphologically and neurochemically indistinguishable from neurons derived from iPSCs where HGprt was intact. Interrogation of the transcriptome using RNA sequencing (RNAseq) indicated that the absence of HGprt had no consistent impact on gene expression during differentiation. Overall, these results suggest HGprt does not have a large impact on early neuronal differentiation and may instead play a more important role in later neuronal differentiation or function.

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic (DA) neurons in the substantia nigra pars compacta, leading to dopamine depletion in the striatum and the hallmark motor symptoms of the disease. However, non-motor deficits, particularly sensory symptoms, often precede motor manifestations, offering a potential early diagnostic window. The impact of non-motor deficits on sensation behavior and the underlying mechanisms remain poorly understood. In this study, we examined changes in tactile sensation within a parkinsonian state by employing a mouse model of PD induced by 6-hydroxydopamine (6-OHDA) to deplete striatal DA. Leveraging the conserved mouse whisker system as a model for tactile-sensory stimulation, we conducted psychophysical experiments to assess sensory-driven behavioral performance during a tactile detection task in both the healthy and PD-like state. Our findings reveal a range of deficits across subjects following 6-OHDA lesion, including DA loss, motor asymmetry, weight loss, and varying levels of altered tactile sensation behavior. Behavioral changes ranged from no impairments in minor cases to isolated sensory-behavioral deficits in moderate cases and severe motor dysfunction in advanced stages. These results underscore the complex relationship between DA imbalance and sensory-motor processing, emphasizing the need for precise and multifaceted behavioral measurements to accurately capture the diverse manifestations of PD.

Defects in numerous aspects of purine metabolism are well-recognized causes for human diseases. The applicability of ultra performance liquid chromatography (UPLC) with photodiode array (PDA) detection for analysis of the most abundant biological relevant purines metabolites is described. This method was optimized to resolve and quantify 15 purine metabolites including ATP, ADP, AMP, adenosine, adenine, GTP, GDP, GMP, IMP, ZMP, guanosine, hypoxanthine, inosine, xanthine and uric acid in 33 min with a 5 μL injection volume. With purified standards, the detection was linear in a range from 0.1 to 100 μM. The within-run and between-run variances were <2% overall, indicating excellent reproducibility and reliability. Samples from cultured human cells were prepared to assess the applicability of the method in biological samples. When compared to normal cell lines, mutant cell lines in which purine salvage was absent showed small or no changes for most intracellular purines. Conditioned medium contained no detectable purines, except for hypoxanthine, which was elevated in the mutant lines as expected. Compared to previous methods, this new UPLC-PDA method provides better resolution of key purine metabolites, higher sensitivity with a smaller sample size and half the run time. Similar to prior methods, the new method appears well suited to the simultaneous analysis of the most abundant biologically relevant purines in biological samples.

Induced pluripotent stem cells (iPSCs) are commonly used to model human genetic diseases. Two main strategies are used. The first involves making iPSC lines from individual cases with a disease, and the second involves making disease-relevant gene edits in established iPSC lines. Because generating gene-edited lines is time consuming and expensive, most studies begin with one starting iPSC stock line and evaluate several gene-edited sublines. The current studies focus on gene-editing to model Lesch-Nyhan disease (LND), which is caused by mutations in the HPRT1 gene. The same pathogenic c.508C>T edit was made in four well-established stock lines, and three gene-edited lines were isolated from each. RNA sequencing (RNAseq) was, then, used to evaluate the impact of the gene edit. Gene-edited lines were compared to their corresponding stock lines, as well as to each other. An aggregate analysis of all lines combined was also conducted to determine the most robust findings across all lines. Results from gene editing were further compared with iPSC lines derived from individual cases with LND, to determine how closely findings from gene editing match results obtained with case-derived lines. There were two main findings. First, the same gene edit has a different impact on gene expression when starting with different starting stock lines. Second, the gene editing strategy does not produce the same results as the case-derived strategy. Potential explanations for these differences are addressed, along with the relevance of these two different strategies for disease modeling.

Abnormal dopamine neurotransmission and striatal dysfunction is implicated in many forms of dystonia, yet the underlying molecular processes remain unknown. Here, we identified thousands of dysregulated genes within striatal spiny projection neuron (SPN) subtypes in a genetic mouse model of DOPA-responsive dystonia (DRD), which is caused by gene defects that reduce dopamine neurotransmission. Although changes in mRNA expression were unique to each SPN subtype, abnormal glutamatergic signaling was implicated in each SPN subtype. Indeed, both AMPA and NMDA receptor-mediated currents were enhanced in direct SPNs but diminished in indirect SPNs in DRD mice. The pattern of mRNA dysregulation was distinct from parkinsonism where the dopamine deficit occurs in adults, suggesting that the phenotypic outcome is dependent on both the timing of the dopaminergic deficit and the SPN-specific adaptions. By leveraging these disease-specific molecular signatures, we identified LRRK2 inhibition, among other mechanisms, as a novel therapeutic target for dystonia.

Induced pluripotent stem cells (iPSCs) are widely used to model human genetic diseases. The most common strategy involves collecting cells from relevant individuals and then reprogramming them into iPSCs. This strategy is very powerful, but finding enough individuals with a specific genetic disease can be challenging, especially since most are rare. In addition, making numerous iPSC lines is time-consuming and expensive. As a result, most studies have included relatively small numbers of iPSC lines, sometimes from the same individual. Considering the experimental variability obtained using different iPSC lines, there has been great interest in delineating the most efficient number of lines needed to achieve a robust and reproducible result. Several recommendations have been published, although most conclusions have been based on methods where experimental variance from individual cases is difficult to separate from technical issues related to the preparation of iPSCs. The current study used gene expression profiles determined by RNA sequencing (RNAseq) to empirically evaluate the impact of the number of unique individuals and the number of replicate iPSC lines from each individual for modeling Lesch-Nyhan disease (LND). This disease is caused by mutations in the HPRT1 gene, which encodes the enzyme hypoxanthine-guanine phosphoribosyltransferase. Results for detecting disease-relevant changes in gene expression depended on the analytical method employed, and whether or not statistical procedures were used to address multiple iPSC lines from the same individual. In keeping with prior studies, the best results were obtained with iPSC lines from 3-4 unique individuals per group. In contrast to prior studies, results were improved with 2 lines per individual, without statistical corrections for duplicate lines from the same individual. In the current study where all lines were produced in parallel using the same methods, most variance in gene expression came from technical factors unrelated to the individual from whom the iPSC lines were prepared.

Dystonia is a neurological disorder characterized by involuntary repetitive movements and abnormal postures. Animal models have played a pivotal role in studying the pathophysiology of dystonia. However, many genetic models, e.g. the Tor1a + / Δ E (DYT1) mouse, lack an overt motor phenotype, despite significant underlying neuronal abnormalities within the striatum and other motor control regions. Because the striatum is implicated in action sequencing, it is possible that the behavioral defect arises as a disruption in the frequency and temporal ordering of behaviors, rather than execution, which cannot be captured using traditional behavioral assays, thus limiting drug discovery efforts. To address this challenge, we used MoSeq, an unsupervised behavioral segmentation framework, to compare the continuous free behavior of control Tor1a + / + mice and knockin Tor1a + / Δ E mutant mice in response to the anti-dystonia drug trihexyphenidyl. Although minimal baseline differences in behavioral organization were detected, both genotypes exhibited robust and consistent shifts in behavioral space structure after treatment with trihexyphenidyl. Further, we demonstrate differences in the behavioral space structure of male vs female mice after trihexyphenidyl challenge. The distinct behavioral signatures evoked by trihexyphenidyl and biological sex, a known risk factor for dystonia, suggest that the analysis of the temporal structure of continuous free behavior provides a sensitive and novel approach to the discovery of therapeutics for the treatment of dystonia.

BACKGROUND:Prior studies have indicated that female individuals outnumber male individuals for certain types of dystonia. Few studies have addressed factors impacting these sex differences or their potential biological mechanisms. OBJECTIVES:To evaluate factors underlying sex differences in the dystonias and explore potential mechanisms for these differences. METHODS:Data from individuals with various types of dystonia were analyzed in relation to sex. Data came from two different sources. One source was the Dystonia Coalition database, which contains predominantly idiopathic adult-onset focal and segmental dystonias. The second source was the MDSGene database, which contains predominantly early-onset monogenic dystonias. RESULTS:The 3222 individuals from the Dystonia Coalition included 71% female participants and 29% male participants for an overall female-to-male ratio (F:M) of 2.4. This ratio varied according to body region affected and whether dystonia was task-specific. The female predominance was age-dependent. Sex did not have a significant impact on co-existing tremor, geste antagoniste, depression or anxiety. In the 1377 individuals from the MDSGene database, female participants outnumbered male participants for some genes (GNAL, GCH1, and ANO3) but not for other genes (THAP1, TH, and TOR1A). CONCLUSIONS:These results are in keeping with prior studies that have indicated female individuals outnumber male individuals for both adult-onset idiopathic and early onset monogenic dystonias. These results extend prior observations by revealing that sex ratios depend on the type of dystonia, age, and underlying genetics.

The dorsal striatum is organized into functional territories defined by corticostriatal inputs onto both direct and indirect spiny projection neurons (SPNs), the major cell types within the striatum. In addition to circuit connectivity, striatal domains are likely defined by the spatially determined transcriptomes of SPNs themselves. To identify cell-type-specific spatiomolecular signatures of direct and indirect SPNs within dorsomedial, dorsolateral, and ventrolateral dorsal striatum, we used RNA profiling in situ hybridization with probes to >98% of protein coding genes. We demonstrate that the molecular identity of SPNs is mediated by hundreds of differentially expressed genes across territories of the striatum, revealing extraordinary heterogeneity in the expression of genes that mediate synaptic function in both direct and indirect SPNs. This deep insight into the complex spatiomolecular organization of the striatum provides a foundation for understanding both normal striatal function and for dissecting region-specific dysfunction in disorders of the striatum.

ObjectiveThe Pacific Lamprey Entosphenus tridentatus is valuable to tribal culture and to the ecosystem, but its abundance in the interior Columbia River has been highly variable and muted in recent years. Translocation programs have been adopted as a proactive strategy to restore Pacific Lamprey abundance to the interior Columbia River, including the Snake River basin, and these efforts have been largely successful in increasing larval and juvenile abundance in the recipient watersheds and further downstream. We address whether adult translocation offspring from three Columbia River Treaty Tribe programs return to Bonneville Dam in numbers that support previous model predictions; and whether Columbia River origin Pacific Lamprey contribute to adult production widely across the species range.MethodsWe used a genetic data set of unknown origin Pacific Lamprey that returned as adults to Bonneville Dam and broadly distributed locations within and outside of the Columbia River basin. We identified the natal origin of these adults via sibship or parentage to assign individuals to either a precise natal site of volitional production or a set of candidate parents from one of the translocation programs in the Columbia River.ResultWe showed that not only have Snake River translocation offspring returned as adults to Bonneville Dam in numbers that exceeded model projections, but offspring from two other tribal translocation programs in the Umatilla (northeast Oregon) and Yakima (south-central Washington) rivers were also detected in recent years. Offspring produced across all three translocation programs are estimated at approximately 1065 fish in 2021. Although Pacific Lamprey are known to lack precise natal homing, which may limit the benefits of translocations in the interior Columbia River basin, evidence from detections in this study supports a preference by interior Columbia River Pacific Lamprey to return home and migrate toward their natal basins. However, a portion of Snake River-origin Pacific Lamprey was estimated to deviate from main-stem routes into tributaries, including tribal ceded areas where tribal harvest occurs (e.g., Sherars Falls on the Deschutes River).ConclusionThese results indicate benefits from Pacific Lamprey translocation programs that will not only increase abundance to targeted areas but will also increase opportunities for tribal harvest of this culturally important species. Restoration actions employing human transportation of fish are able to increase adult numbers of a culturally important species, Pacific Lamprey, to areas where they can be harvested by Columbia River Treaty Tribes; evidenced by genetic analysis to determine natal origins of individuals through their lifetimes (10+ years).Impact statement

Dystonia is characterised as uncontrolled, often painful involuntary muscle contractions that cause abnormal postures and repetitive or twisting movements. These movements can be continuous or sporadic and affect different parts of the body and range in severity. Dystonia and its related conditions present a huge cause of neurological morbidity worldwide. Although therapies are available, achieving optimal symptom control without major unwanted effects remains a challenge. Most pharmacological treatments for dystonia aim to modulate the effects of one or more neurotransmitters in the central nervous system, but doing so effectively and with precision is far from straightforward. In this chapter we discuss the physiology of key neurotransmitters, including dopamine, noradrenaline, serotonin (5-hydroxytryptamine), acetylcholine, GABA, glutamate, adenosine and cannabinoids, and their role in dystonia. We explore the ways in which existing pharmaceuticals as well as novel agents, currently in clinical trial or preclinical development, target dystonia, and their respective advantages and disadvantages. Finally, we discuss current and emerging genetic therapies which may be used to treat genetic forms of dystonia.

DYT1 dystonia is associated with decreased striatal dopamine release. In this study, we examined the possibility that ultrastructural changes of nigrostriatal dopamine terminals could contribute to this neurochemical imbalance using a serial block face/scanning electron microscope (SBF/SEM) and three-dimensional reconstruction to analyse striatal tyrosine hydroxylase-immunoreactive (TH-IR) terminals and their synapses in a DYT1(ΔE) knockin (DYT1-KI) mouse model of DYT1 dystonia. Furthermore, to study possible changes in vesicle packaging capacity of dopamine, we used transmission electron microscopy to assess the synaptic vesicle size in striatal dopamine terminals. Quantitative comparative analysis of 80 fully reconstructed TH-IR terminals in the WT and DYT1-KI mice indicate (1) no significant difference in the volume of TH-IR terminals; (2) no major change in the proportion of axo-spinous versus axo-dendritic synapses; (3) no significant change in the post-synaptic density (PSD) area of axo-dendritic synapses, while the PSDs of axo-spinous synapses were significantly smaller in DYT1-KI mice; (4) no significant change in the contact area between TH-IR terminals and dendritic shafts or spines, while the ratio of PSD area/contact area decreased significantly for both axo-dendritic and axo-spinous synapses in DYT1-KI mice; (5) no significant difference in the mitochondria volume; and (6) no significant difference in the synaptic vesicle area between the two groups. Altogether, these findings suggest that abnormal morphometric changes of nigrostriatal dopamine terminals and their post-synaptic targets are unlikely to be a major source of reduced striatal dopamine release in DYT1 dystonia.

ObjectiveThe anadromous Pacific Lamprey Entosphenus tridentatus is an ecologically and culturally important fish that has experienced declines in abundance and distribution throughout large portions of its range. However, the lack of fundamental biological information, such as age and growth, impedes management and conservation efforts.MethodsWe used known-age hatchery and wild Pacific Lamprey to evaluate the potential of statoliths (apatite concretions found within the auditory capsules) to provide estimates of individual size and age throughout ontogeny. Statolith size and growth were assessed with comparisons of morphometrics (area, perimeter, length, and width) in relation to fish length. Traditional band-reading methods and random forest (RF) analysis were evaluated for their utility in estimating age.ResultWe observed a strong, positive relationship between statolith size and fish length for larvae that were hatchery reared. However, there were no positive relationships between statolith size and fish length for any of the postmetamorphic life stages, which indicates that statolith growth slows dramatically or ceases after metamorphosis. Band-reading methods of statoliths from known-age lamprey (1- and 2- to 9-year-olds) resulted in accurate age estimates for 28% of the fish, and 57% of mean age estimates fell within 1 year of the true age. While we found that the statolith was not very useful for traditional age estimation techniques, its inclusion in morphometric-based age classifications was promising. A RF model based on body length, collection river, and statolith area accurately assigned 76% of the larval and freshwater juveniles to their known age. Additionally, an RF model using only body length and river of origin correctly classified 70% of the known-age samples.ConclusionMultivariate approaches, including those that include lethal and nonlethal predictor variables, provide potential approaches to estimate age in larval and early juvenile Pacific Lamprey.

Although the mechanisms underlying dystonia are largely unknown, dystonia is often associated with abnormal dopamine neurotransmission. DOPA-responsive dystonia (DRD) is a prototype disorder for understanding dopamine dysfunction in dystonia because it is caused by mutations in genes necessary for the synthesis of dopamine and alleviated by the indirect-acting dopamine agonist l-DOPA. Although adaptations in striatal dopamine receptor-mediated intracellular signaling have been studied extensively in models of Parkinson’s disease, another movement disorders associated with dopamine deficiency, little is known about dopaminergic adaptations in dystonia. To identify the dopamine receptor-mediated intracellular signaling associated with dystonia, we used immunohistochemistry to quantify striatal protein kinase A activity and extracellular signal-related kinase (ERK) phosphorylation after dopaminergic challenges in a knockin mouse model of DRD. l-DOPA treatment induced the phosphorylation of both protein kinase A substrates and ERK largely in D1 dopamine receptor-expressing striatal neurons. As expected, this response was blocked by pretreatment with the D1 dopamine receptor antagonist SCH23390. The D2 dopamine receptor antagonist raclopride also significantly reduced the phosphorylation of ERK; this contrasts with models of parkinsonism in which l-DOPA-induced ERK phosphorylation is not mediated by D2 dopamine receptors. Further, the dysregulated signaling was dependent on striatal subdomains whereby ERK phosphorylation was largely confined to dorsomedial (associative) striatum while the dorsolateral (sensorimotor) striatum was unresponsive. This complex interaction between striatal functional domains and dysregulated dopamine-receptor mediated responses has not been observed in other models of dopamine deficiency, such as parkinsonism, suggesting that regional variation in dopamine-mediated neurotransmission may be a hallmark of dystonia.

Non‐selective antagonists of muscarinic acetylcholine receptors (mAChRs) that broadly inhibit all five mAChR subtypes provide an efficacious treatment for some movement disorders, including Parkinson’s disease and dystonia. Despite their efficacy in these and other central nervous system disorders, anti‐muscarinic therapy has limited utility due to severe adverse effects that often limit their tolerability by patients. Recent advances in understanding the roles that each mAChR subtype plays in disease pathology suggest that highly selective ligands for individual subtypes may underlie the anti‐parkinsonian and anti‐dystonic efficacy observed with the use of non‐selective anti‐muscarinic therapeutics. Our recent work has indicated that the M4 muscarinic acetylcholine receptor has several important roles in opposing aberrant neurotransmitter release, intracellular signaling pathways, and brain circuits associated with movement disorders. This raises the possibility that selective antagonists of M4 may recapitulate the efficacy of non‐selective anti‐muscarinic therapeutics and may decrease or eliminate the adverse effects associated with these non‐selective drugs. However, this hypothesis has not been directly tested due to lack of selective antagonists of M4. Here we utilize genetic mAChR knockout animals in combination with non‐selective mAChR antagonists to confirm that the M4 receptor underlies the locomotor‐stimulating and anti‐parkinsonian efficacy in rodent models. We also report the synthesis, discovery, and characterization of a series of first‐in‐class selective M4 antagonists. These novel compounds have ideal pharmacokinetic properties for in vivo evaluations, and we have confirmed that these optimized compounds have anti‐parkinsonian and anti‐dystonic efficacy in pharmacological and genetic models of movement disorders. These data provide critical pre‐clinical rationale for the development of M4 antagonists and represent a potential novel treatment mechanism to meet the unmet clinical need across several movement disorders.

Alcohol consumption affects motor behavior and motor control. Both acute and chronic alcohol abuse have been extensively investigated; however, the therapeutic efficacy of alcohol on some movement disorders, such as myoclonus‐dystonia or essential tremor, still does not have a plausible mechanistic explanation. Yet, there are surprisingly few systematic trials with known GABAergic drugs mimicking the effect of alcohol on neurotransmission. In this brief survey, we aim to summarize the effects of EtOH on striatal function, providing an overview of its cellular and synaptic actions in a ‘circuit‐centered’ view. In addition, we will review both experimental and clinical evidence, in the attempt to provide a plausible mechanistic explanation for alcohol‐responsive movement disorders, with particular emphasis on dystonia. Different hypotheses emerge, which may provide a rationale for the utilization of drugs that mimic alcohol effects, predicting potential drug repositioning.

This review provides an overview of the synaptic dysfunctions of neuronal circuits and underlying neurochemical alterations observed in the hyperkinetic movement disorders, dystonia and dyskinesia. These disorders exhibit similar changes in expression of synaptic plasticity and neuromodulation. This includes alterations in physical attributes of synapses, synaptic protein expression, and neurotransmitter systems, such as glutamate and gamma-aminobutyric acid (GABA), and neuromodulators, such as dopamine, acetylcholine, serotonin, adenosine, and endocannabinoids. A full understanding of the mechanisms and consequences of disruptions in synaptic function and plasticity will lend insight into the development of these disorders and new ways to combat maladaptive changes.

Trihexyphenidyl (THP), a non-selective muscarinic receptor (mAChR) antagonist, is commonly used for the treatment of dystonia associated with TOR1A, otherwise known as DYT1 dystonia. A better understanding of the mechanism of action of THP is a critical step in the development of better therapeutics with fewer side effects. We previously found that THP normalizes the deficit in striatal dopamine (DA) release in a mouse model of TOR1A dystonia (Tor1a+/ΔE knockin (KI) mice), revealing a plausible mechanism of action for this compound, considering that abnormal DA neurotransmission is consistently associated with many forms of dystonia. However, the mAChR subtype(s) that mediate the rescue of striatal dopamine release remain unclear. In this study we used a combination of pharmacological challenges and cell-type specific mAChR conditional knockout mice of either sex to determine which mAChR subtypes mediate the DA release-enhancing effects of THP. We determined that THP acts in part at M4 mAChR on striatal cholinergic interneurons to enhance DA release in both Tor1a+/+ and Tor1a+/ΔE KI mice. Further, we found that the subtype selective M4 antagonist VU6021625 recapitulates the effects of THP. These data implicate a principal role for M4 mAChR located on striatal cholinergic interneurons in the mechanism of action of THP and suggest that subtype selective M4 mAChR antagonists may be effective therapeutics with fewer side effects than THP for the treatment of TOR1A dystonia.

TOR1A-associated dystonia, otherwise known as DYT1 dystonia, is an inherited dystonia caused by a three base-pair deletion in the TOR1A gene (TOR1AΔE). Although the mechanisms underlying the dystonic movements are largely unknown, abnormalities in striatal dopamine and acetylcholine neurotransmission are consistently implicated whereby dopamine release is reduced while cholinergic tone is increased. Because striatal cholinergic neurotransmission mediates dopamine release, it is not known if the dopamine release deficit is mediated indirectly by abnormal acetylcholine neurotransmission or if Tor1a(ΔE) acts directly within dopaminergic neurons to attenuate release. To dissect the microcircuit that governs the deficit in dopamine release, we conditionally expressed Tor1a(ΔE) in either dopamine neurons or cholinergic interneurons in mice and assessed striatal dopamine release using ex vivo fast scan cyclic voltammetry or dopamine efflux using in vivo microdialysis. Conditional expression of Tor1a(ΔE) in cholinergic neurons did not affect striatal dopamine release. In contrast, conditional expression of Tor1a(ΔE) in dopamine neurons reduced dopamine release to 50% of normal, which is comparable to the deficit in Tor1a+/ΔE knockin mice that express the mutation ubiquitously. Despite the deficit in dopamine release, we found that the Tor1a(ΔE) mutation does not cause obvious nerve terminal dysfunction as other presynaptic mechanisms, including electrical excitability, vesicle recycling/refilling, Ca2+ signaling, D2 dopamine autoreceptor function and GABAB receptor function, are intact. Although the mechanistic link between Tor1a(ΔE) and dopamine release is unclear, these results clearly demonstrate that the defect in dopamine release is caused by the action of the Tor1a(ΔE) mutation within dopamine neurons.

Dystonia is characterized by involuntary muscle contractions that cause debilitating twisting movements and postures. Although dysfunction of the basal ganglia, a brain region that mediates movement, is implicated in many forms of dystonia, the underlying mechanisms are unclear. The inherited metabolic disorder DOPA-responsive dystonia is considered a prototype for understanding basal ganglia dysfunction in dystonia because it is caused by mutations in genes necessary for the synthesis of the neurotransmitter dopamine, which mediates the activity of the basal ganglia. Therefore, to reveal abnormal striatal cellular processes and pathways implicated in dystonia, we used an unbiased proteomic approach in a knockin mouse model of DOPA-responsive dystonia, a model in which the striatum is known to play a central role in the expression of dystonia. Fifty-seven of the 1805 proteins identified were differentially regulated in DOPA-responsive dystonia mice compared to control mice. Most differentially regulated proteins were associated with gene ontology terms that implicated either mitochondrial or synaptic dysfunction whereby proteins associated with mitochondrial function were generally over-represented and proteins associated with synaptic function were largely under-represented. Remarkably, nearly 20% of the differentially regulated striatal proteins identified in our screen are associated with pathogenic variants that cause inherited disorders with dystonia as a sign in humans suggesting shared mechanisms across many different forms of dystonia.