RESUMEN
Abnormal involuntary movements, or dyskinesias, are seen in many neurologic diseases, including disorders where the brain appears grossly normal. This observation suggests that alterations in neural activity or connectivity may underlie dyskinesias. One influential model proposes that involuntary movements are driven by an imbalance in the activity of striatal direct and indirect pathway neurons (dMSNs and iMSNs, respectively). Indeed, in some animal models, there is evidence that dMSN hyperactivity contributes to dyskinesia. Given the many diseases associated with dyskinesia, it is unclear whether these findings generalize to all forms. Here, we used male and female mice in a mouse model of paroxysmal nonkinesigenic dyskinesia (PNKD) to assess whether involuntary movements are related to aberrant activity in the striatal direct and indirect pathways. In this model, as in the human disorder PNKD, animals experience dyskinetic attacks in response to caffeine or alcohol. Using optically identified striatal single-unit recordings in freely moving PNKD mice, we found a loss of iMSN firing during dyskinesia bouts. Further, chemogenetic inhibition of iMSNs triggered dyskinetic episodes in PNKD mice. Finally, we found that these decreases in iMSN firing are likely because of aberrant endocannabinoid-mediated suppression of glutamatergic inputs. These data show that striatal iMSN dysfunction contributes to the etiology of dyskinesia in PNKD, and suggest that indirect pathway hypoactivity may be a key mechanism for the generation of involuntary movements in other disorders.SIGNIFICANCE STATEMENT Involuntary movements, or dyskinesias, are part of many inherited and acquired neurologic syndromes. There are few effective treatments, most of which have significant side effects. Better understanding of which cells and patterns of activity cause dyskinetic movements might inform the development of new neuromodulatory treatments. In this study, we used a mouse model of an inherited human form of paroxysmal dyskinesia in combination with cell type-specific tools to monitor and manipulate striatal activity. We were able to narrow in on a specific group of neurons that causes dyskinesia in this model, and found alterations in a well-known form of plasticity in this cell type, endocannabinoid-dependent synaptic LTD. These findings point to new areas for therapeutic development.
Asunto(s)
Corea , Discinesias , Animales , Corea/inducido químicamente , Cuerpo Estriado , Modelos Animales de Enfermedad , Discinesias/etiología , Femenino , Levodopa/efectos adversos , Masculino , Ratones , NeuronasRESUMEN
As noted in the separate introduction to this special topic section, episodic and electrical disorders can appear quite different clinically and yet share many overlapping features, including attack precipitants, therapeutic responses, natural history, and the types of genes that cause many of the genetic forms (i.e., ion channel genes). Thus, as we mapped and attempted to clone genes causing other episodic disorders, ion channels were always outstanding candidates when they mapped to the critical region of linkage in such a family. However, some of these disorders do not result from mutations in channels. This realization has opened up large and exciting new areas for the pathogenesis of these disorders. In some cases, the mutations occur in genes of unknown function or without understanding of molecular pathogenesis. Recently, emerging insights into a fascinating group of episodic movement disorders, the paroxysmal dyskinesias, and study of the causative genes and proteins are leading to the emerging concept of episodic electric disorders resulting from synaptic dysfunction. Much work remains to be done, but the field is evolving rapidly. As it does, we have come to realize that the molecular pathogenesis of electrical and episodic disorders is more complex than a scenario in which such disorders are simply due to mutations in the primary determinants of membrane excitability (channels).
Asunto(s)
Mutación/genética , Enfermedades del Sistema Nervioso/genética , Enfermedades del Sistema Nervioso/fisiopatología , Sinapsis/genética , Sinapsis/fisiología , Animales , Proteínas Reguladoras de la Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/fisiología , Quinasa Idelta de la Caseína/genética , Quinasa Idelta de la Caseína/fisiología , Modelos Animales de Enfermedad , Transportador de Glucosa de Tipo 1/genética , Transportador de Glucosa de Tipo 1/fisiología , Humanos , Proteínas de la Membrana/genética , Proteínas de la Membrana/fisiología , Ratones , Proteínas Musculares/genética , Proteínas Musculares/fisiología , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/fisiología , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/fisiologíaRESUMEN
Paroxysmal nonkinesigenic dyskinesia (PNKD) is an autosomal dominant episodic movement disorder precipitated by coffee, alcohol, and stress. We previously identified the causative gene but the function of the encoded protein remains unknown. We also generated a PNKD mouse model that revealed dysregulated dopamine signaling in vivo. Here, we show that PNKD interacts with synaptic active zone proteins Rab3-interacting molecule (RIM)1 and RIM2, localizes to synapses, and modulates neurotransmitter release. Overexpressed PNKD protein suppresses release, and mutant PNKD protein is less effective than wild-type at inhibiting exocytosis. In PNKD KO mice, RIM1/2 protein levels are reduced and synaptic strength is impaired. Thus, PNKD is a novel synaptic protein with a regulatory role in neurotransmitter release.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/metabolismo , Corea/metabolismo , Exocitosis/fisiología , Proteínas Musculares/fisiología , Vesículas Sinápticas/metabolismo , Animales , Ratones , Ratones Noqueados , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Unión ProteicaRESUMEN
INTRODUCTION: Andersen-Tawil syndrome (ATS) is a potassium channelopathy affecting cardiac and skeletal muscle. Periodic paralysis is a presenting symptom in some patients, whereas, in others, symptomatic arrhythmias or prolongation of QT in echocardiographic recordings will lead to diagnosis of ATS. Striking intrafamilial variability of expression of KCNJ2 mutations and rarity of the syndrome may lead to misdiagnosis. METHODS: We report 15 patients from 8 Polish families with ATS, including 3 with novel KCNJ2 mutations. RESULTS: All patients had dysmorphic features; periodic paralysis affected males more frequently than females (80% vs. 20%), and most attacks were normokalemic. Two patients (with T75M and T309I mutations) had aborted sudden cardiac death. An implantable cardioverter-defibrillator was utilized in 40% of cases. CONCLUSIONS: KCNJ2 mutations cause a variable phenotype, with dysmorphic features seen in all patients studied, a high penetrance of periodic paralysis in males and ventricular arrhythmia with a risk of sudden cardiac death.
Asunto(s)
Síndrome de Andersen/complicaciones , Síndrome de Andersen/genética , Predisposición Genética a la Enfermedad/genética , Cardiopatías/etiología , Mutación/genética , Canales de Potasio de Rectificación Interna/genética , Adolescente , Adulto , Síndrome de Andersen/cirugía , Niño , Análisis Mutacional de ADN , Desfibriladores Implantables , Ecocardiografía , Femenino , Cardiopatías/genética , Cardiopatías/cirugía , Humanos , Estudios Longitudinales , Masculino , Parálisis Periódicas Familiares/etiología , Parálisis Periódicas Familiares/genética , Polonia , Estudios Retrospectivos , Adulto JovenRESUMEN
Paroxysmal non-kinesigenic dyskinesia (PNKD) is a rare autosomal dominant movement disorder triggered by stress, fatigue or consumption of either alcohol or caffeine. Attacks last 1-4 h and consist of dramatic dystonia and choreoathetosis in the limbs, trunk and face. The disease is associated with single amino acid changes (A7V or A9V) in PNKD, a protein of unknown function. Here we studied the stability, cellular localization and enzymatic activity of the PNKD protein in cultured cells and transgenic animals. The N-terminus of the wild-type (WT) long PNKD isoform (PNKD-L) undergoes a cleavage event in vitro, resistance to which is conferred by disease-associated mutations. Mutant PNKD-L protein is degraded faster than the WT protein. These results suggest that the disease mutations underlying PNKD may disrupt protein processing in vivo, a hypothesis supported by our observation of decreased cortical Pnkd-L levels in mutant transgenic mice. Pnkd is homologous to a superfamily of enzymes with conserved ß-lactamase domains. It shares highest homology with glyoxalase II but does not catalyze the same reaction. Lower glutathione levels were found in cortex lysates from Pnkd knockout mice versus WT littermates. Taken together, our results suggest an important role for the Pnkd protein in maintaining cellular redox status.
Asunto(s)
Corea/genética , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Animales , Western Blotting , Células Cultivadas , Drosophila , Técnica del Anticuerpo Fluorescente , Inmunoprecipitación , Luciferasas , Ratones , Ratones Transgénicos , Mutación Missense/genética , Estabilidad Proteica , Estructura Terciaria de Proteína , beta-Lactamasas/genéticaRESUMEN
OBJECTIVE: Myoclonus is characterized by sudden, brief involuntary movements, and its presence is debilitating. We identified a family suffering from adult onset, cortical myoclonus without associated seizures. We performed clinical, electrophysiological, and genetic studies to define this phenotype. METHODS: A large, 4-generation family with a history of myoclonus underwent careful questioning, examination, and electrophysiological testing. Thirty-five family members donated blood samples for genetic analysis, which included single nucleotide polymorphism mapping, microsatellite linkage, targeted massively parallel sequencing, and Sanger sequencing. In silico and in vitro experiments were performed to investigate functional significance of the mutation. RESULTS: We identified 11 members of a Canadian Mennonite family suffering from adult onset, slowly progressive, disabling, multifocal myoclonus. Somatosensory evoked potentials indicated a cortical origin of the myoclonus. There were no associated seizures. Some severely affected individuals developed signs of progressive cerebellar ataxia of variable severity late in the course of their illness. The phenotype was inherited in an autosomal dominant fashion. We demonstrated linkage to chromosome 16q21-22.1. We then sequenced all coding sequence in the critical region, identifying only a single cosegregating, novel, nonsynonymous mutation, which resides in the gene NOL3. Furthermore, this mutation was found to alter post-translational modification of NOL3 protein in vitro. INTERPRETATION: We propose that familial cortical myoclonus is a novel movement disorder that may be caused by mutation in NOL3. Further investigation of the role of NOL3 in neuronal physiology may shed light on neuronal membrane hyperexcitability and pathophysiology of myoclonus and related disorders.
Asunto(s)
Proteínas Reguladoras de la Apoptosis/genética , Salud de la Familia , Predisposición Genética a la Enfermedad/genética , Proteínas Musculares/genética , Mutación/genética , Mioclonía/genética , Adolescente , Adulto , Edad de Inicio , Animales , Canadá , Línea Celular Transformada , Mapeo Cromosómico , Cromosomas Humanos Par 16 , Electroencefalografía , Femenino , Ácido Glutámico/genética , Humanos , Masculino , Ratones , Persona de Mediana Edad , Mioclonía/diagnóstico , Fenotipo , Prolina/genética , TransfecciónRESUMEN
Paroxysmal non-kinesigenic dyskinesia (PNKD) is a clinical syndrome of sudden involuntary movements, mostly of dystonic type, which may be triggered by alcohol or coffee intake, stress and fatigue. The attacks of PNKD may consist of various combinations of dystonia, chorea, athetosis and balism. They can be partial and unilateral, but mostly the hyperkinetic movements are bilateral and generalized. We present a large Polish family with 7 symptomatic members of the family in 6 generations. In all affected persons, the onset of clinical symptoms was in early childhood. All male cases showed an increase in severity and frequency of the attacks with ageing, while the only living female patient noticed an improvement of PNKD during both her pregnancies and also after menopause. In addition, at the age of 55 years, she developed symptoms of Parkinson's disease with good response to levodopa treatment.
Asunto(s)
Corea/genética , Corea/fisiopatología , Proteínas Musculares/genética , Anciano , Corea/tratamiento farmacológico , Dopaminérgicos/uso terapéutico , Femenino , Humanos , Levodopa/uso terapéutico , Masculino , Menopausia , Linaje , Polonia , Embarazo , Población BlancaRESUMEN
Migraine is a common disabling disorder with a significant genetic component, characterized by severe headache and often accompanied by nausea, vomiting, and light sensitivity. We identified two families, each with a distinct missense mutation in the gene encoding casein kinase Iδ (CKIδ), in which the mutation cosegregated with both the presence of migraine and advanced sleep phase. The resulting alterations (T44A and H46R) occurred in the conserved catalytic domain of CKIδ, where they caused reduced enzyme activity. Mice engineered to carry the CKIδ-T44A allele were more sensitive to pain after treatment with the migraine trigger nitroglycerin. CKIδ-T44A mice also exhibited a reduced threshold for cortical spreading depression (believed to be the physiological analog of migraine aura) and greater arterial dilation during cortical spreading depression. Astrocytes from CKIδ-T44A mice showed increased spontaneous and evoked calcium signaling. These genetic, cellular, physiological, and behavioral analyses suggest that decreases in CKIδ activity can contribute to the pathogenesis of migraine.
Asunto(s)
Quinasa Idelta de la Caseína/genética , Trastornos Migrañosos/genética , Mutación/genética , Sueño/genética , Animales , Astrocitos/metabolismo , Señalización del Calcio , Quinasa Idelta de la Caseína/metabolismo , Depresión de Propagación Cortical , Femenino , Células HEK293 , Humanos , Hiperalgesia/genética , Masculino , Ratones , Trastornos Migrañosos/fisiopatología , Proteínas Mutantes/metabolismo , Nitroglicerina , Linaje , Fenotipo , Estimulación Física , Proteínas Proto-Oncogénicas c-fos/metabolismo , Umbral Sensorial , Fases del Sueño/genética , Médula Espinal/metabolismo , Médula Espinal/patología , Núcleos del Trigémino/metabolismo , Núcleos del Trigémino/fisiopatología , Vasoconstricción , VasodilataciónRESUMEN
Paroxysmal nonkinesigenic dyskinesia (PNKD) is an autosomal dominant episodic movement disorder. Patients have episodes that last 1 to 4 hours and are precipitated by alcohol, coffee, and stress. Previous research has shown that mutations in an uncharacterized gene on chromosome 2q33-q35 (which is termed PNKD) are responsible for PNKD. Here, we report the generation of antibodies specific for the PNKD protein and show that it is widely expressed in the mouse brain, exclusively in neurons. One PNKD isoform is a membrane-associated protein. Transgenic mice carrying mutations in the mouse Pnkd locus equivalent to those found in patients with PNKD recapitulated the human PNKD phenotype. Staining for c-fos demonstrated that administration of alcohol or caffeine induced neuronal activity in the basal ganglia in these mice. They also showed nigrostriatal neurotransmission deficits that were manifested by reduced extracellular dopamine levels in the striatum and a proportional increase of dopamine release in response to caffeine and ethanol treatment. These findings support the hypothesis that the PNKD protein functions to modulate striatal neuro-transmitter release in response to stress and other precipitating factors.
Asunto(s)
Corea/fisiopatología , Dopamina/metabolismo , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Secuencia de Aminoácidos , Animales , Corea/genética , Cuerpo Estriado/citología , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/fisiología , Inhibidores de Captación de Dopamina/farmacología , Células HEK293 , Humanos , Ratones , Ratones Transgénicos , Datos de Secuencia Molecular , Mutación , Nomifensina/farmacología , FenotipoRESUMEN
Paroxysmal kinesigenic dyskinesia with infantile convulsions (PKD/IC) is an episodic movement disorder with autosomal-dominant inheritance and high penetrance, but the causative genetic mutation is unknown. We have now identified four truncating mutations involving the gene PRRT2 in the vast majority (24/25) of well-characterized families with PKD/IC. PRRT2 truncating mutations were also detected in 28 of 78 additional families. PRRT2 encodes a proline-rich transmembrane protein of unknown function that has been reported to interact with the t-SNARE, SNAP25. PRRT2 localizes to axons but not to dendritic processes in primary neuronal culture, and mutants associated with PKD/IC lead to dramatically reduced PRRT2 levels, leading ultimately to neuronal hyperexcitability that manifests in vivo as PKD/IC.
Asunto(s)
Distonía/complicaciones , Distonía/genética , Proteínas de la Membrana/genética , Mutación/genética , Proteínas del Tejido Nervioso/genética , Convulsiones/complicaciones , Convulsiones/genética , Alelos , Secuencia de Aminoácidos , Animales , Sistema Nervioso Central/metabolismo , Segregación Cromosómica/genética , Variaciones en el Número de Copia de ADN/genética , Femenino , Genoma Humano/genética , Células HEK293 , Humanos , Masculino , Proteínas de la Membrana/química , Ratones , Datos de Secuencia Molecular , Proteínas Mutantes/metabolismo , Proteínas del Tejido Nervioso/química , Linaje , Fenotipo , Unión Proteica/genética , Ratas , Alineación de Secuencia , Análisis de Secuencia de ADN , Especificidad de la Especie , Proteína 25 Asociada a Sinaptosomas/metabolismoRESUMEN
Our laboratory demonstrated previously that spontaneously hypertensive rats (SHR) exhibited an elevated basal Fos expression in the nucleus tractus solitarii (NTS), the terminal site for primary baroreceptor afferents, and that Fos protein is required for the re-expression of angiotensin subtype 1 receptor (AT1R) mRNA in the NTS after baroreceptor activation. The present study evaluated the hypothesis that this re-expression of AT1R is augmented in SHR and is promoted by the heightened Fos expression. Reverse transcription-polymerase chain reaction analysis revealed that baroreceptor activation via sustained increase in systemic arterial pressure resulted in a discernible reduction in the expression of AT1R mRNA at the dorsomedial medulla of SHR and normotensive Wistar-Kyoto rats. However, SHR manifested an appreciably larger magnitude of decline, followed by a faster time course of re-expression in AT1R mRNA. Parallel findings were obtained from the pressor response induced by microinjection unilaterally of angiotensin II (40 pmol) into the NTS. Whereas the re-expression of AT1R at both transcriptional and functional expression levels after baroreceptor activation was discernibly blunted by prior bilateral application into the NTS of an antisense c-fos oligonucleotide (50 pmol), the suppression in SHR was again significantly more intense. Control pretreatment with the corresponding sense or scrambled c-fos oligonucleotide was ineffective. We conclude that the heightened Fos expression in SHR is causatively related to the augmented re-expression of AT1R in the NTS at both transcriptional and functional levels.
Asunto(s)
Hipertensión/metabolismo , Proteínas Proto-Oncogénicas c-fos/fisiología , Receptores de Angiotensina/biosíntesis , Núcleo Solitario/metabolismo , Regulación hacia Arriba , Angiotensina II/farmacología , Animales , Hipertensión/genética , Hipertensión/fisiopatología , Inmunohistoquímica , Masculino , Microinyecciones , Oligonucleótidos Antisentido/administración & dosificación , Oligonucleótidos Antisentido/farmacología , Presorreceptores/metabolismo , Proteínas Proto-Oncogénicas c-fos/análisis , Proteínas Proto-Oncogénicas c-fos/genética , ARN Mensajero/biosíntesis , Ratas , Ratas Endogámicas SHR , Ratas Endogámicas WKY , Receptor de Angiotensina Tipo 1 , Receptor de Angiotensina Tipo 2 , Receptores de Angiotensina/análisis , Receptores de Angiotensina/genética , Receptores de Angiotensina/inmunología , Núcleo Solitario/química , Activación Transcripcional , Vasoconstrictores/farmacologíaRESUMEN
Paroxysmal non-kinesigenic dyskinesia (PNKD) is characterized by spontaneous hyperkinetic attacks that are precipitated by alcohol, coffee, stress and fatigue. We report mutations in the myofibrillogenesis regulator 1 (MR-1) gene causing PNKD in 50 individuals from eight families. The mutations cause changes (Ala to Val) in the N-terminal region of two MR-1 isoforms. The MR-1L isoform is specifically expressed in brain and is localized to the cell membrane while the MR-1S isoform is ubiquitously expressed and shows diffuse cytoplasmic and nuclear localization. Bioinformatic analysis reveals that the MR-1 gene is homologous to the hydroxyacylglutathione hydrolase (HAGH) gene. HAGH functions in a pathway to detoxify methylglyoxal, a compound present in coffee and alcoholic beverages and produced as a by-product of oxidative stress. Our results suggest a mechanism whereby alcohol, coffee and stress may act as precipitants of attacks in PNKD. Stress response pathways will be important areas for elucidation of episodic disease genetics where stress is a common precipitant of many common disorders like epilepsy, migraine and cardiac arrhythmias.