Project description:Paroxysmal dyskinesias are episodic movement disorders that can be inherited or are sporadic in nature. The pathophysiology underlying these disorders remains largely unknown but may involve disrupted ion homeostasis due to defects in cell-surface channels or nutrient transporters. In this study, we describe a family with paroxysmal exertion-induced dyskinesia (PED) over 3 generations. Their PED was accompanied by epilepsy, mild developmental delay, reduced CSF glucose levels, hemolytic anemia with echinocytosis, and altered erythrocyte ion concentrations. Using a candidate gene approach, we identified a causative deletion of 4 highly conserved amino acids (Q282_S285del) in the pore region of the glucose transporter 1 (GLUT1). Functional studies in Xenopus oocytes and human erythrocytes revealed that this mutation decreased glucose transport and caused a cation leak that alters intracellular concentrations of sodium, potassium, and calcium. We screened 4 additional families, in which PED is combined with epilepsy, developmental delay, or migraine, but not with hemolysis or echinocytosis, and identified 2 additional GLUT1 mutations (A275T, G314S) that decreased glucose transport but did not affect cation permeability. Combining these data with brain imaging studies, we propose that the dyskinesias result from an exertion-induced energy deficit that may cause episodic dysfunction of the basal ganglia, and that the hemolysis with echinocytosis may result from alterations in intracellular electrolytes caused by a cation leak through mutant GLUT1.
Project description:BACKGROUND AND PURPOSE: Mutations in neuronal Kv7 (KCNQ) potassium channels can cause episodic neurological disorders. Paroxysmal dyskinesias with dystonia are a group of movement disorders which are regarded as ion channelopathies, but the role of Kv7 channels in the pathogenesis and as targets for the treatment have so far not been examined. EXPERIMENTAL APPROACH: In the present study, we therefore examined the effects of the activators of neuronal Kv7.2/7.3 channels retigabine (5, 7.5, 10 mg kg(-1) i.p. and 10, 20 mg kg(-1) p.o.) and flupirtine (10, 20 mg kg(-1) i.p.) and of the channel blocker 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991, 3 and 6 mg kg(-1) i.p.) in the dt sz mutant hamster, a model of paroxysmal dyskinesia in which dystonic episodes occur in response to stress. KEY RESULTS: Retigabine (10 mg kg(-1) i.p., 20 mg kg(-1) p.o.) and flupirtine (20 mg kg(-1) i.p.) significantly improved dystonia, while XE-991 caused a significant aggravation in the dt sz mutant. The antidystonic effect of retigabine (10 mg kg(-1) i.p.) was counteracted by XE-991 (3 mg kg(-1) i.p.). CONCLUSIONS AND IMPLICATIONS: These data indicate that dysfunctions of neuronal Kv7 channels deserve attention in dyskinesias. Since retigabine and flupirtine are well tolerated in humans, the present finding of pronounced antidystonic efficacy in the dt sz mutant suggests that neuronal Kv7 channel activators are interesting candidates for the treatment of dystonia-associated dyskinesias and probably of other types of dystonias. The established analgesic effects of Kv7 channel openers might contribute to improvement of these disorders which are often accompanied by painful muscle spasms.
Project description:View Supplementary Video Movement disorders are a major feature of Glut1 deficiency. As recently identified in adults with paroxysmal exercise-induced dystonia, similar events were reported in pediatric Glut1 deficiency. In a case series, parent videos of regular motor state and paroxysmal events were requested from children with Glut1 deficiency on clinical follow-up. A questionnaire was sent out to 60 families. Videos of nonparoxysmal/paroxysmal states in 3 children illustrated the ataxic-dystonic, choreatiform, and dyskinetic-dystonic nature of paroxysmal events. Fifty-six evaluated questionnaires confirmed this observation in 73% of patients. Events appeared to increase with age, were triggered by low ketosis, sleep deprivation, and physical exercise, and unrelated to sex, hypoglycorrhachia, SLC2A1 mutations, or type of ketogenic diet. We conclude that paroxysmal events are a major clinical feature in Glut1 deficieny, linking the pediatric disease to adult Glut1D-associated exercise-induced paroxysmal dyskinesias.
Project description:Dystonia is defined as a neurological syndrome characterized by involuntary sustained or intermittent muscle contractions causing twisting, often repetitive movements, and postures. Paroxysmal dyskinesias are episodic movement disorders encompassing dystonia, chorea, athetosis, and ballism in conscious individuals. Several decades of research have enhanced the understanding of the etiology of human dystonia and dyskinesias that are associated with dystonia, but the pathophysiology remains largely unknown. The spontaneous occurrence of hereditary dystonia and paroxysmal dyskinesia is well documented in rodents used as animal models in basic dystonia research. Several hyperkinetic movement disorders, described in dogs, horses and cattle, show similarities to these human movement disorders. Although dystonia is regarded as the third most common movement disorder in humans, it is often misdiagnosed because of the heterogeneity of etiology and clinical presentation. Since these conditions are poorly known in veterinary practice, their prevalence may be underestimated in veterinary medicine. In order to attract attention to these movement disorders, i.e., dystonia and paroxysmal dyskinesias associated with dystonia, and to enhance interest in translational research, this review gives a brief overview of the current literature regarding dystonia/paroxysmal dyskinesia in humans and summarizes similar hereditary movement disorders reported in domestic animals.
Project description:Genetic mechanisms explain the pathophysiology of many forms of epilepsy and other paroxysmal disorders, such as alternating hemiplegia of childhood, familial hemiplegic migraine, and paroxysmal dyskinesias. Epilepsy is a key feature of well-defined genetic syndromes including tuberous sclerosis complex, Rett syndrome, Angelman syndrome, and others. There is an increasing number of single-gene causes or susceptibility factors associated with several epilepsy syndromes, including the early-onset epileptic encephalopathies, benign neonatal/infantile seizures, progressive myoclonus epilepsies, genetic generalized and benign focal epilepsies, epileptic aphasias, and familial focal epilepsies. Molecular mechanisms are diverse, and a single gene can be associated with a broad range of phenotypes. Additional features, such as dysmorphisms, head size, movement disorders, and family history may provide clues to a genetic diagnosis. Genetic testing can impact medical care and counseling. We discuss genetic mechanisms of epilepsy and other paroxysmal disorders, tools and indications for genetic testing, known genotype-phenotype associations, the importance of genetic counseling, and a look toward the future of epilepsy genetics.
Project description:BACKGROUND:Paroxysmal kinesigenic dyskinesia (PKD) and epilepsy share common pathogenic mechanisms but their pathophysiological connections remain unknown. Our study reports an individual with both disorders as a consequence of pseudohypoparathyroidism (PHP). This observation suggests potential shared pathophysiological mechanisms between PKD and epilepsy. METHODS:We report the case of a 15-year-old male with pre-diagnosed PKD and symptomatic epilepsy. We recorded the symptoms and carried out comprehensive biochemical, genetic, imaging, and EEG analyses to examine the characteristics and potentially shared etiology of these conditions. RESULTS:In this case, the patient's PKD and symptomatic epilepsy were secondary to pseudohypoparathyroidism (PHP). The patient had a seven-year history of intermittent, involuntary paroxysmal episodic movements, and a six-year history of a loss of consciousness with convulsions. The electroencephalography results showed that the paroxysmal low and medium amplitude slow waves, isolated sharp waves, and sharp slow-wave release occurred in the right prefrontal temporal cortex. Serum analysis indicated a calcium concentration of 1.91 mmol/L, a phosphorus concentration of 2.68 mmol/L, an alkaline phosphatase concentration of 114 IU/L, and a parathyroid hormone concentration of 109 pg/ml. Computerized tomography and magnetic resonance imaging results showed multiple calcifications in the bilateral frontal and parietal lobe cortex, bilateral thalamus, basal ganglia, and centrum semiovale. Furthermore, GNAS methylation abnormalities were discovered during methylation testing. There was no recurrence of abnormal movements or epileptic seizures, and calcium concentrations returned to healthy levels, following the pharmacological treatment of PHP. CONCLUSION:In this case, PKD and symptomatic epilepsy were caused by PHP. This report underscores the importance of looking for biochemical abnormalities in PKD and symptomatic epilepsy patients. We suggest that all such intractable epilepsy seizure patients should be screened for PHP.
Project description:Paroxysmal dyskinesia can be subdivided into three clinical syndromes: paroxysmal kinesigenic dyskinesia or choreoathetosis, paroxysmal exercise-induced dyskinesia, and paroxysmal non-kinesigenic dyskinesia. Each subtype is associated with the known causative genes PRRT2, SLC2A1 and PNKD, respectively. Although separate screening studies have been carried out on each of the paroxysmal dyskinesia genes, to date there has been no large study across all genes in these disorders and little is known about the pathogenic mechanisms. We analysed all three genes (the whole coding regions of SLC2A1 and PRRT2 and exons one and two of PNKD) in a series of 145 families with paroxysmal dyskinesias as well as in a series of 53 patients with familial episodic ataxia and hemiplegic migraine to investigate the mutation frequency and type and the genetic and phenotypic spectrum. We examined the mRNA expression in brain regions to investigate how selective vulnerability could help explain the phenotypes and analysed the effect of mutations on patient-derived mRNA. Mutations in the PRRT2, SLC2A1 and PNKD genes were identified in 72 families in the entire study. In patients with paroxysmal movement disorders 68 families had mutations (47%) out of 145 patients. PRRT2 mutations were identified in 35% of patients, SLC2A1 mutations in 10%, PNKD in 2%. Two PRRT2 mutations were in familial hemiplegic migraine or episodic ataxia, one SLC2A1 family had episodic ataxia and one PNKD family had familial hemiplegic migraine alone. Several previously unreported mutations were identified. The phenotypes associated with PRRT2 mutations included a high frequency of migraine and hemiplegic migraine. SLC2A1 mutations were associated with variable phenotypes including paroxysmal kinesigenic dyskinesia, paroxysmal non-kinesigenic dyskinesia, episodic ataxia and myotonia and we identified a novel PNKD gene deletion in familial hemiplegic migraine. We found that some PRRT2 loss-of-function mutations cause nonsense mediated decay, except when in the last exon, whereas missense mutations do not affect mRNA. In the PNKD family with a novel deletion, mRNA was truncated losing the C-terminus of PNKD-L and still likely loss-of-function, leading to a reduction of the inhibition of exocytosis, and similar to PRRT2, an increase in vesicle release. This study highlights the frequency, novel mutations and clinical and molecular spectrum of PRRT2, SLC2A1 and PNKD mutations as well as the phenotype-genotype overlap among these paroxysmal movement disorders. The investigation of paroxysmal movement disorders should always include the analysis of all three genes, but around half of our paroxysmal series remain genetically undefined implying that additional genes are yet to be identified.
Project description:Paroxysmal kinesigenic dyskinesia (PKD), a rare paroxysmal movement disorder often misdiagnosed as epilepsy, is characterized by recurrent, brief dyskinesia attacks triggered by sudden voluntary movement. Pathophysiological mechanism of PKD remains not well understood. Ion channelopathy has been suggested, since the disease responds well to ion channel blockers. Mutations in proline-rich transmembrane protein 2 (PRRT2) were recently identified in patients with familial PKD. To extend these genetic reports, we studied a family with clinical manifestations of familial PKD responding well to low dose carbamazepine. Therapeutic dose ranged from 1.5 to 2.0 mg/ kg/day, below that in seizure control. One insertion mutation c.649_650insC (p.P217fsX7) was identified in three patients of the family. This study avers PRRT2's high sensitivity for PKD phenotype. Identification of genes underlying pathogenesis will enhance diagnosis and treatment. Function of PRRT2 and its role in PKD warrant further investigation.
Project description:OBJECTIVE:The proline-rich transmembrane protein (PRRT2) gene was recently identified using exome sequencing as the cause of autosomal dominant paroxysmal kinesigenic dyskinesia (PKD) with or without infantile convulsions (IC) (PKD/IC syndrome). Episodic neurologic disorders, such as epilepsy, migraine, and paroxysmal movement disorders, often coexist and are thought to have a shared channel-related etiology. To investigate further the frequency, spectrum, and phenotype of PRRT2 mutations, we analyzed this gene in 3 large series of episodic neurologic disorders with PKD/IC, episodic ataxia (EA), and hemiplegic migraine (HM). METHODS:The PRRT2 gene was sequenced in 58 family probands/sporadic individuals with PKD/IC, 182 with EA, 128 with HM, and 475 UK and 96 Asian controls. RESULTS:PRRT2 genetic mutations were identified in 28 out of 58 individuals with PKD/IC (48%), 1/182 individuals with EA, and 1/128 individuals with HM. A number of loss-of-function and coding missense mutations were identified; the most common mutation found was the p.R217Pfs*8 insertion. Males were more frequently affected than females (ratio 52:32). There was a high proportion of PRRT2 mutations found in families and sporadic cases with PKD associated with migraine or HM (10 out of 28). One family had EA with HM and another large family had typical HM alone. CONCLUSIONS:This work expands the phenotype of mutations in the PRRT2 gene to include the frequent occurrence of migraine and HM with PKD/IC, and the association of mutations with EA and HM and with familial HM alone. We have also extended the PRRT2 mutation type and frequency in PKD and other episodic neurologic disorders.
Project description:Paroxysmal movement disorders (PMDs) are rare neurological diseases typically manifesting with intermittent attacks of abnormal involuntary movements. Two main categories of PMDs are recognized based on the phenomenology: Paroxysmal dyskinesias (PxDs) are characterized by transient episodes hyperkinetic movement disorders, while attacks of cerebellar dysfunction are the hallmark of episodic ataxias (EAs). From an etiological point of view, both primary (genetic) and secondary (acquired) causes of PMDs are known. Recognition and diagnosis of PMDs is based on personal and familial medical history, physical examination, detailed reconstruction of ictal phenomenology, neuroimaging, and genetic analysis. Neurophysiological or laboratory tests are reserved for selected cases. Genetic knowledge of PMDs has been largely incremented by the advent of next generation sequencing (NGS) methodologies. The wide number of genes involved in the pathogenesis of PMDs reflects a high complexity of molecular bases of neurotransmission in cerebellar and basal ganglia circuits. In consideration of the broad genetic and phenotypic heterogeneity, a NGS approach by targeted panel for movement disorders, clinical or whole exome sequencing should be preferred, whenever possible, to a single gene approach, in order to increase diagnostic rate. This review is focused on clinical and genetic features of PMDs with the aim to (1) help clinicians to recognize, diagnose and treat patients with PMDs as well as to (2) provide an overview of genes and molecular mechanisms underlying these intriguing neurogenetic disorders.