small molecules

2025-02-12 | Altered functional brain connectivity in Dyt1 knock-in mouse models

DYT1 dystonia is an early onset, generalized form of isolated dystonia characterized by sustained involuntary muscle co-contraction, leading to abnormal movements and postures. It is the most common hereditary form of primary dystonia, caused by a trinucleotide GAG deletion in the DYT1 gene, which encodes the TorsinA protein. Recent studies conceptualized dystonia as a functional network disorder involving basal ganglia, thalamus, cortex and cerebellum. However, how TorsinA dysfunction in specific cell types affects network connectivity and dystonia-related pathophysiology remains unclear. In this study, we aimed to elucidate the impact of the GAG TorsinA mutation present globally and when restricted to the cortical and hippocampal neurons. To accomplish this, we generated two distinct Dyt1 mouse models, one with Dyt1 dGAG knock-in throughout the body (dGAG) and another with a cerebral cortex-specific Dyt1 dGAG knock-in using Emx1 promoter (EMX). In both models, we performed in vivo neuroimaging at ultra-high field (11.1T). We employed functional magnetic resonance imaging (fMRI) to assess resting-state and sensory-evoked brain connectivity and activation, along with diffusion MRI (dMRI) to evaluate microstructural changes. We hypothesized that dGAG mice would exhibit widespread network disruptions compared to the cortex-specific EMX mice, due to broader TorsinA dysfunction across the basal ganglia and cerebellum. We also hypothesized that EMX mice would exhibit altered functional connectivity and activation patterns, supporting the idea that TorsinA dysfunction in the sensorimotor cortex alone can induce network abnormalities. In dGAG animals, we observed significantly lower functional connectivity between key sensorimotor nodes, such as the globus pallidus, somatosensory cortex, thalamus, and cerebellum. EMX mice, while showing less extensive network disruptions, exhibited increased functional connectivity between cerebellum and seeds in the striatum and brainstem. These functional connectivity alterations between nodes in the basal ganglia and the cerebellum in both dGAG, EMX models underscore the involvement of cerebellum in dystonia. No significant structural changes were observed in either model. Overall, these results strengthen the concept of dystonia as a network disorder where multiple nodes across the brain network contribute to pathophysiology, supporting the idea that therapeutic strategies in dystonia may benefit from consideration of network properties across multiple brain regions.

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2024-03-03 | Disturbed brain energy metabolism in a rodent model of DYT-TOR1A dystonia

DYT-TOR1A (DYT1) dystonia, characterized by reduced penetrance and suspected environmental triggers, is explored using a "second hit" DYT-TOR1A rat model. We aim to investigate the biological mechanisms driving the conversion into a dystonic phenotype, focusing on the striatum's role in dystonia pathophysiology. Sciatic nerve crush injury was induced in ∆ETorA rats, lacking spontaneous motor abnormalities, and wild-type (wt) rats. Twelve weeks post-injury, unbiased RNA-sequencing was performed on the striatum to identify differentially expressed genes (DEGs) and pathways. Fenofibrate, a PPARα agonist, was introduced to assess its effects on gene expression. 18F-FDG autoradiography explored metabolic alterations in brain networks. Low transcriptomic variability existed between naïve wt and ∆ETorA rats (17 DEGs). Sciatic nerve injury significantly impacted ∆ETorA rats (1009 DEGs) compared to wt rats (216 DEGs). Pathway analyses revealed disruptions in energy metabolism, specifically in fatty acid β-oxidation and glucose metabolism. Fenofibrate induced gene expression changes in wt rats but failed in ∆ETorA rats. Fenofibrate increased dystonia-like movements in wt rats but reduced them in ∆ETorA rats. 18F-FDG autoradiography indicated modified glucose metabolism in motor and somatosensory cortices and striatum in both ∆ETorA and wt rats post-injury. Our findings highlight perturbed energy metabolism pathways in DYT-TOR1A dystonia, emphasizing compromised PPARα agonist efficacy in the striatum. Furthermore, we identify impaired glucose metabolism in the brain network, suggesting a potential shift in energy substrate utilization in dystonic DYT-TOR1A rats. These results contribute to understanding the pathophysiology and potential therapeutic targets for DYT-TOR1A dystonia.

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2022-05-17 | p97/UBXD1 Generate Ubiquitylated Proteins That Are Sequestered into Nuclear Envelope Herniations in Torsin-Deficient Cells.

DYT1 dystonia is a debilitating neurological movement disorder that arises upon Torsin ATPase deficiency. Nuclear envelope (NE) blebs that contain FG-nucleoporins (FG-Nups) and K48-linked ubiquitin are the hallmark phenotype of Torsin manipulation across disease models of DYT1 dystonia. While the aberrant deposition of FG-Nups is caused by defective nuclear pore complex assembly, the source of K48-ubiquitylated proteins inside NE blebs is not known. Here, we demonstrate that the characteristic K48-ubiquitin accumulation inside blebs requires p97 activity. This activity is highly dependent on the p97 adaptor UBXD1. We show that p97 does not significantly depend on the Ufd1/Npl4 heterodimer to generate the K48-ubiquitylated proteins inside blebs, nor does inhibiting translation affect the ubiquitin sequestration in blebs. However, stimulating global ubiquitylation by heat shock greatly increases the amount of K48-ubiquitin sequestered inside blebs. These results suggest that blebs have an extraordinarily high capacity for sequestering ubiquitylated protein generated in a p97-dependent manner. The p97/UBXD1 axis is thus a major factor contributing to cellular DYT1 dystonia pathology and its modulation represents an unexplored potential for therapeutic development.

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2022-03-16 | Vesicular Acetylcholine Transporter Alters Cholinergic Tone and Synaptic Plasticity in DYT1 Dystonia.

Acetylcholine-mediated transmission plays a central role in the impairment of corticostriatal synaptic activity and plasticity in multiple DYT1 mouse models. However, the nature of such alteration remains unclear. The aim of the present work was to characterize the mechanistic basis of cholinergic dysfunction in DYT1 dystonia to identify potential targets for pharmacological intervention. We utilized electrophysiology recordings, immunohistochemistry, enzymatic activity assays, and Western blotting techniques to analyze in detail the cholinergic machinery in the dorsal striatum of the Tor1a+/- mouse model of DYT1 dystonia. We found a significant increase in the vesicular acetylcholine transporter (VAChT) protein level, the protein responsible for loading acetylcholine (ACh) from the cytosol into synaptic vesicles, which indicates an altered cholinergic tone. Accordingly, in Tor1a+/- mice we measured a robust elevation in basal ACh content coupled to a compensatory enhancement of acetylcholinesterase (AChE) enzymatic activity. Moreover, pharmacological activation of dopamine D2 receptors, which is expected to reduce ACh levels, caused an abnormal elevation in its content, as compared to controls. Patch-clamp recordings revealed a reduced effect of AChE inhibitors on cholinergic interneuron excitability, whereas muscarinic autoreceptor function was preserved. Finally, we tested the hypothesis that blockade of VAChT could restore corticostriatal long-term synaptic plasticity deficits. Vesamicol, a selective VAChT inhibitor, rescued a normal expression of synaptic plasticity. Overall, our findings indicate that VAChT is a key player in the alterations of striatal plasticity and a novel target to normalize cholinergic dysfunction observed in DYT1 dystonia. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

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2022-02-09 | Characterization of the direct pathway in Dyt1 ΔGAG heterozygous knock-in mice and dopamine receptor 1-expressing-cell-specific Dyt1 conditional knockout mice.

DYT1 dystonia is a movement disorder mainly caused by a trinucleotide deletion (ΔGAG) in DYT1 (TOR1A), coding for torsinA. DYT1 dystonia patients show trends of decreased striatal ligand-binding activities to dopamine receptors 1 (D1R) and 2 (D2R). Dyt1 ΔGAG knock-in (KI) mice, which have the corresponding ΔGAG deletion, similarly exhibit reduced striatal D1R and D2R-binding activities and their expression levels. While the consequences of D2R reduction have been well characterized, relatively little is known about the effect of D1R reduction. Here, locomotor responses to D1R and D2R antagonists were examined in Dyt1 KI mice. Dyt1 KI mice showed significantly less responsiveness to both D1R antagonist SCH 23390 and D2R antagonist raclopride. The electrophysiological recording indicated that Dyt1 KI mice showed a significantly increased paired-pulse ratio of the striatal D1R-expressing medium spiny neurons and altered miniature excitatory postsynaptic currents. To analyze the in vivo torsinA function in the D1R-expressing neurons further, Dyt1 conditional knockout (Dyt1 d1KO) mice in these neurons were generated. Dyt1 d1KO mice had decreased spontaneous locomotor activity and reduced numbers of slips in the beam-walking test. Dyt1 d1KO male mice showed abnormal gait. Dyt1 d1KO mice showed defective striatal D1R maturation. Moreover, the mutant striatal D1R-expressing medium spiny neurons had increased capacitance, decreased sEPSC frequency, and reduced intrinsic excitability. The results suggest that torsinA in the D1R-expressing cells plays an important role in the electrophysiological function and motor performance. Medical interventions to the direct pathway may affect the onset and symptoms of this disorder.

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proteins

2024-04-12 | RANBP17 Overexpression Restores Nucleocytoplasmic Transport and Ameliorates Neurodevelopment in Induced DYT1 Dystonia Motor Neurons.

DYT1 dystonia is a debilitating neurological movement disorder, and it represents the most frequent and severe form of hereditary primary dystonia. There is currently no cure for this disease due to its unclear pathogenesis. In our previous study utilizing patient-specific motor neurons (MNs), we identified distinct cellular deficits associated with the disease, including a deformed nucleus, disrupted neurodevelopment, and compromised nucleocytoplasmic transport (NCT) functions. However, the precise molecular mechanisms underlying these cellular impairments have remained elusive. In this study, we revealed the genome-wide changes in gene expression in DYT1 MNs through transcriptomic analysis. We found that those dysregulated genes are intricately involved in neurodevelopment and various biological processes. Interestingly, we identified that the expression level of RANBP17, a RAN-binding protein crucial for NCT regulation, exhibited a significant reduction in DYT1 MNs. By manipulating RANBP17 expression, we further demonstrated that RANBP17 plays an important role in facilitating the nuclear transport of both protein and transcript cargos in induced human neurons. Excitingly, the overexpression of RANBP17 emerged as a substantial mitigating factor, effectively restoring impaired NCT activity and rescuing neurodevelopmental deficits observed in DYT1 MNs. These findings shed light on the intricate molecular underpinnings of impaired NCT in DYT1 neurons and provide novel insights into the pathophysiology of DYT1 dystonia, potentially leading to the development of innovative treatment strategies.

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2023-04-20 | Atypical nuclear envelope condensates linked to neurological disorders reveal nucleoporin-directed chaperone activities.

DYT1 dystonia is a debilitating neurological movement disorder arising from mutation in the AAA+ ATPase TorsinA. The hallmark of Torsin dysfunction is nuclear envelope blebbing resulting from defects in nuclear pore complex biogenesis. Whether blebs actively contribute to disease manifestation is unknown. We report that FG-nucleoporins in the bleb lumen form aberrant condensates and contribute to DYT1 dystonia by provoking two proteotoxic insults. Short-lived ubiquitylated proteins that are normally rapidly degraded partition into the bleb lumen and become stabilized. In addition, blebs selectively sequester a specific HSP40-HSP70 chaperone network that is modulated by the bleb component MLF2. MLF2 suppresses the ectopic accumulation of FG-nucleoporins and modulates the selective properties and size of condensates in vitro. Our study identifies dual mechanisms of proteotoxicity in the context of condensate formation and establishes FG-nucleoporin-directed activities for a nuclear chaperone network.

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2019-09-30 | The mutation responsible for torsion dystonia type 1 shows the ability to stimulate intracellular aggregation of mutant huntingtin.

Introduction: Torsion dystonia type 1 is the most common form of early-onset primary dystonia. Previous reports have suggested that torsin 1A, a protein mutated in this disease, might function as a chaperone that prevents the toxic aggregation of misfolded polypeptides. The aim of the study: The aim of this study was to verify the chaperone function of torsin 1A by investigating its ability to prevent the aggregation of huntingtin model peptides. Materials and methods: N-terminal mutant huntingtin fragments of different length were co-expressed in neuronal HT-22 and non-neuronal HeLa cells with either the wild-type or mutant (ΔE302/303) torsin 1A protein. The transfected cells were immunostained and analyzed for the presence of huntingtin aggregates using fluorescence microscopy. Results: The immunofluorescence analysis of huntingtin subcellular distribution within the transfected cells showed no significant difference between the huntingtin aggregation levels in cells co-expressing the wild-type torsin 1A and in control cells co-transfected with an empty vector. Instead, it was the increased level of huntingtin aggregation in the presence of the torsion dystonia-causing ΔE302/303 mutant that reached statistical significance in both neuronal and non-neuronal cells. Conclusions: Either torsin 1A does not function as a chaperone protein or huntingtin is not an efficient substrate for such a hypothetical chaperone activity. However, the ability of mutant torsin 1A to stimulate the accumulation of aggregation-prone polypeptides might constitute an important source of ΔE302/303 pathogenicity and thus a potential target for future therapy. Dystonia torsyjna typu 1 jest najczęstszą postacią pierwotnej dystonii o wczesnym początku. Kilka wcześniejszych doniesień sugerowało, że torsyna 1A, białko zmutowane w tej chorobie, może pełnić funkcję białka opiekuńczego, zapobiegającego toksycznej agregacji nieprawidłowo zwiniętych polipeptydów. Celem niniejszej pracy było zweryfikowanie hipotezy o opiekuńczej funkcji torsyny 1A poprzez zbadanie zdolności tego białka do zapobiegania agregacji modelowych peptydów huntingtynowych. N-końcowe fragmenty zmutowanej huntingtyny o różnej długości były koeksprymowane z prawidłową lub zmutowaną (ΔE302/303) torsyną 1A w neuronalnych komórkach HT-22 i nieneuronalnych komórkach HeLa. Transfekowane komórki były poddawane immunobarwieniu i analizowane na obecność agregatów huntingtynowych przy użyciu mikroskopii fluorescencyjnej. Immunofluorescencyjna analiza subkomórkowej lokalizacji huntingtyny w transfekowanych komórkach wykazała brak znaczących różnic między poziomem agregacji huntingtyny w komórkach eksprymujących prawidłową torsynę 1A i w komórkach kontrolnych transfekowanych pustym wektorem, wskazując na brak znaczącej aktywności opiekuńczej torsyny 1A w badanych warunkach. Statystycznie znaczący okazał się natomiast wzrost poziomu agregacji huntingtyny w obecności patogennego wariantu ΔE302/303 torsyny 1 A, co dotyczyło zarówno komórek neuronalnych, jak i nieneuronalnych. Otrzymane wyniki wskazują, że torsyna 1A nie pełni funkcji białka opiekuńczego albo też huntingtyna nie jest wydajnym substratem dla owej hipotetycznej funkcji tego białka, jednakże zaobserwowana zdolność mutacji ΔE302/303 w torsynie 1A do stymulowania procesu akumulacji agregujących peptydów może stanowić istotne źródło jej patogenności, a tym samym potencjalny cel przyszłej terapii dla dystonii torsyjnej typu 1.

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2019-08-06 | RGS9-2 rescues dopamine D2 receptor levels and signaling in DYT1 dystonia mouse models.

Dopamine D2 receptor signaling is central for striatal function and movement, while abnormal activity is associated with neurological disorders including the severe early-onset DYT1 dystonia. Nevertheless, the mechanisms that regulate D2 receptor signaling in health and disease remain poorly understood. Here, we identify a reduced D2 receptor binding, paralleled by an abrupt reduction in receptor protein level, in the striatum of juvenile Dyt1 mice. This occurs through increased lysosomal degradation, controlled by competition between β-arrestin 2 and D2 receptor binding proteins. Accordingly, we found lower levels of striatal RGS9-2 and spinophilin. Further, we show that genetic depletion of RGS9-2 mimics the D2 receptor loss of DYT1 dystonia striatum, whereas RGS9-2 overexpression rescues both receptor levels and electrophysiological responses in Dyt1 striatal neurons. This work uncovers the molecular mechanism underlying D2 receptor downregulation in Dyt1 mice and in turn explains why dopaminergic drugs lack efficacy in DYT1 patients despite significant evidence for striatal D2 receptor dysfunction. Our data also open up novel avenues for disease-modifying therapeutics to this incurable neurological disorder.

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2017-08-03 | A novel high-throughput yeast genetic screen for factors modifying protein levels of the Early-Onset Torsion Dystonia-associated variant torsinAΔE

Dystonia is the third most common movement disorder, but its diagnosis and treatment remain challenging. One of the most severe types of Dystonia is Early-Onset Torsion Dystonia (EOTD). The best studied and validated EOTD-associated mutation, torsinAΔE, is a deletion of a C-terminal glutamate residue in the AAA+ ATPase, torsinA. TorsinA appears to be an Endoplasmic Reticulum (ER)/Nuclear Envelope chaperone with multiple roles in the secretory pathway and in determining subcellular architecture. Many functions are disabled in the torsinAΔE variant, and torsinAΔE is also less stable than wild-type torsinA and is a substrate for ER-associated degradation. Nevertheless, the molecular factors involved in torsinA and torsinAΔE's biogenesis and degradation have not been fully explored. To identify conserved cellular factors that can alter torsinAΔE protein levels, we designed a new high-throughput, automated, genome-wide screen utilizing our validated Saccharomyces cerevisiae torsinA expression system. By analyzing the non-essential yeast deletion collection, we identified 365 deletion strains with altered torsinAΔE steady-state levels. One notable hit was EUG1, which encodes a member of the protein disulfide isomerase family (PDIs). PDIs reside in the ER and catalyze the formation of disulfide bonds, mediate protein quality control, and aid in nascent protein folding. We validated the role of select human PDIs in torsinA biogenesis in mammalian cells and found that overexpression of PDIs reduced the levels of torsinA and torsinAΔE. Together, our data report the first genome-wide screen to identify cellular factors that reduce expression levels of the EOTD-associated protein torsinAΔE. More generally, the identified hits contribute to dissect the cellular machinery involved in folding and degrading a torsinA variant, and constitute potential therapeutic factors for EOTD. This screen can also be readily adapted to identify factors impacting the levels of any protein of interest, considerably expanding the applicability of yeast in both basic and applied research.

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gene therapies

2025-04-26 | Empirical Simulation and In Silico Evaluation of an Ethically Governed, AI-Enhanced CRISPR Prime Editing Framework for TOR1A Mutation Correction in Dystonia

Abstract Hereditary dystonia, particularly the isolated form of early onset, is often caused by a deletion of the GAG in the TOR1A gene, leading to a dysfunctional TorsinA protein and severe motor impairments. In this study, we investigate an AI-enhanced CRISPR prime editing framework designed for the precise correction of the TOR1A mutation. Our framework integrates the generation of candidate pegRNA with an empirical simulation of training data, enabling the tuning of a random forest model that predicts editing efficiency. This approach generates robust quantitative outputs (validation R 2 score of 0.701). SHapley Additive exPlanations (SHAP) revealed that GC content (mean SHAP = 0.22) and off-target risk (mean SHAP = 0.18) were the strongest drivers of predicted efficiency. The GC content showed strong positive correlations with melting temperature (r = 0.75) and guide efficiency (r = 0.82). By linking the simulated modeling work to the practical challenges of genetic neurosurgery in dystonia, a proof-of-concept framework is presented that is both ethically governed and clinically pertinent. This work looks toward a future of scalpel-less surgery by laying a foundation for future integration with empirical datasets and more advanced deep learning techniques.

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2023-07-24 | Cell-specific Dyt1 ∆GAG knock-in to basal ganglia and cerebellum reveal differential effects on motor behavior and sensorimotor network function.

Dystonia is a neurological movement disorder characterized by repetitive, unintentional movements and disabling postures that result from sustained or intermittent muscle contractions. The basal ganglia and cerebellum have received substantial focus in studying DYT1 dystonia. It remains unclear how cell-specific ∆GAG mutation of torsinA within specific cells of the basal ganglia or cerebellum affects motor performance, somatosensory network connectivity, and microstructure. In order to achieve this goal, we generated two genetically modified mouse models: in model 1 we performed Dyt1 ∆GAG conditional knock-in (KI) in neurons that express dopamine-2 receptors (D2-KI), and in model 2 we performed Dyt1 ∆GAG conditional KI in Purkinje cells of the cerebellum (Pcp2-KI). In both of these models, we used functional magnetic resonance imaging (fMRI) to assess sensory-evoked brain activation and resting-state functional connectivity, and diffusion MRI to assess brain microstructure. We found that D2-KI mutant mice had motor deficits, abnormal sensory-evoked brain activation in the somatosensory cortex, as well as increased functional connectivity of the anterior medulla with cortex. In contrast, we found that Pcp2-KI mice had improved motor performance, reduced sensory-evoked brain activation in the striatum and midbrain, as well as reduced functional connectivity of the striatum with the anterior medulla. These findings suggest that (1) D2 cell-specific Dyt1 ∆GAG mediated torsinA dysfunction in the basal ganglia results in detrimental effects on the sensorimotor network and motor output, and (2) Purkinje cell-specific Dyt1 ∆GAG mediated torsinA dysfunction in the cerebellum results in compensatory changes in the sensorimotor network that protect against dystonia-like motor deficits.

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2022-06-20 | Generation of gene-corrected isogenic control cell lines from a DYT1 dystonia patient iPSC line carrying a heterozygous GAG mutation in TOR1A gene.

Childhood-onset torsin dystonia (DYT1) is a rare hereditary movement disorder and usually caused by a heterozygous GAG deletion (c.907-909) in the TOR1A gene (ΔE, p.Glu303del). The neuronal functions of torsin proteins and the pathogenesis of ΔE mutation are not clear. Previously, we have generated a hiPSC line from DYT1 patient fibroblast cells. In this study, we genetically corrected GAG deletion and obtained two isogenic control lines. These hiPSC lines contain the wild-type TOR1A sequence, showed the normal stem cell morphology and karyotype, expressed pluripotency markers, and differentiated into three germ layers, providing a valuable resource in DYT1 research.

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2021-09-29 | TorsinA restoration in a mouse model identifies a critical therapeutic window for DYT1 dystonia.

In inherited neurodevelopmental diseases, pathogenic processes unique to critical periods during early brain development may preclude the effectiveness of gene modification therapies applied later in life. We explored this question in a mouse model of DYT1 dystonia, a neurodevelopmental disease caused by a loss-of-function mutation in the TOR1A gene encoding torsinA. To define the temporal requirements for torsinA in normal motor function and gene replacement therapy, we developed a mouse line enabling spatiotemporal control of the endogenous torsinA allele. Suppressing torsinA during embryogenesis caused dystonia-mimicking behavioral and neuropathological phenotypes. Suppressing torsinA during adulthood, however, elicited no discernible abnormalities, establishing an essential requirement for torsinA during a developmental critical period. The developing CNS exhibited a parallel "therapeutic critical period" for torsinA repletion. Although restoring torsinA in juvenile DYT1 mice rescued motor phenotypes, there was no benefit from adult torsinA repletion. These data establish a unique requirement for torsinA in the developing nervous system and demonstrate that the critical period genetic insult provokes permanent pathophysiology mechanistically delinked from torsinA function. These findings imply that to be effective, torsinA-based therapeutic strategies must be employed early in the course of DYT1 dystonia.

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2017-05-23 | Haploinsufficiency of KMT2B, Encoding the Lysine-Specific Histone Methyltransferase 2B, Results in Early-Onset Generalized Dystonia.

Early-onset generalized dystonia represents the severest form of dystonia, a hyperkinetic movement disorder defined by involuntary twisting postures. Although frequently transmitted as a single-gene trait, the molecular basis of dystonia remains largely obscure. By whole-exome sequencing a parent-offspring trio in an Austrian kindred affected by non-familial early-onset generalized dystonia, we identified a dominant de novo frameshift mutation, c.6406delC (p.Leu2136Serfs∗17), in KMT2B, encoding a lysine-specific methyltransferase involved in transcriptional regulation via post-translational modification of histones. Whole-exome-sequencing-based exploration of a further 30 German-Austrian individuals with early-onset generalized dystonia uncovered another three deleterious mutations in KMT2B-one de novo nonsense mutation (c.1633C>T [p.Arg545∗]), one de novo essential splice-site mutation (c.7050-2A>G [p.Phe2321Serfs∗93]), and one inherited nonsense mutation (c.2428C>T [p.Gln810∗]) co-segregating with dystonia in a three-generation kindred. Each of the four mutations was predicted to mediate a loss-of-function effect by introducing a premature termination codon. Suggestive of haploinsufficiency, we found significantly decreased total mRNA levels of KMT2B in mutant fibroblasts. The phenotype of individuals with KMT2B loss-of-function mutations was dominated by childhood lower-limb-onset generalized dystonia, and the family harboring c.2428C>T (p.Gln810∗) showed variable expressivity. In most cases, dystonic symptoms were accompanied by heterogeneous non-motor features. Independent support for pathogenicity of the mutations comes from the observation of high rates of dystonic presentations in KMT2B-involving microdeletion syndromes. Our findings thus establish generalized dystonia as the human phenotype associated with haploinsufficiency of KMT2B. Moreover, we provide evidence for a causative role of disordered histone modification, chromatin states, and transcriptional deregulation in dystonia pathogenesis.

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