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Dogra D, Meza-Santoscoy PL, Gavrilovici C, Rehak R, de la Hoz CLR, Ibhazehiebo K, Rho JM, Kurrasch DM. kcna1a mutant zebrafish model episodic ataxia type 1 (EA1) with epilepsy and show response to first-line therapy carbamazepine. Epilepsia 2023; 64:2186-2199. [PMID: 37209379 DOI: 10.1111/epi.17659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 05/18/2023] [Accepted: 05/18/2023] [Indexed: 05/22/2023]
Abstract
OBJECTIVE KCNA1 mutations are associated with a rare neurological movement disorder known as episodic ataxia type 1 (EA1), and epilepsy is a common comorbidity. Current medications provide only partial relief for ataxia and/or seizures, making new drugs needed. Here, we characterized zebrafish kcna1a-/- as a model of EA1 with epilepsy and compared the efficacy of the first-line therapy carbamazepine in kcna1a-/- zebrafish to Kcna1-/- rodents. METHODS CRISPR/Cas9 mutagenesis was used to introduce a mutation in the sixth transmembrane segment of the zebrafish Kcna1 protein. Behavioral and electrophysiological assays were performed on kcna1a-/- larvae to assess ataxia- and epilepsy-related phenotypes. Real-time quantitative polymerase chain reaction (qPCR) was conducted to measure mRNA levels of brain hyperexcitability markers in kcna1a-/- larvae, followed by bioenergetics profiling to evaluate metabolic function. Drug efficacies were tested using behavioral and electrophysiological assessments, as well as seizure frequency in kcna1a-/- zebrafish and Kcna1-/- mice, respectively. RESULTS Zebrafish kcna1a-/- larvae showed uncoordinated movements and locomotor deficits, along with scoliosis and increased mortality. The mutants also exhibited impaired startle responses when exposed to light-dark flashes and acoustic stimulation as well as hyperexcitability as measured by extracellular field recordings and upregulated fosab transcripts. Neural vglut2a and gad1b transcript levels were disrupted in kcna1a-/- larvae, indicative of a neuronal excitatory/inhibitory imbalance, as well as a significant reduction in cellular respiration in kcna1a-/- , consistent with dysregulation of neurometabolism. Notably, carbamazepine suppressed the impaired startle response and brain hyperexcitability in kcna1a-/- zebrafish but had no effect on the seizure frequency in Kcna1-/- mice, suggesting that this EA1 zebrafish model might better translate to humans than rodents. SIGNIFICANCE We conclude that zebrafish kcna1a-/- show ataxia and epilepsy-related phenotypes and are responsive to carbamazepine treatment, consistent with EA1 patients. These findings suggest that kcna1-/- zebrafish are a useful model for drug screening as well as studying the underlying disease biology.
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Affiliation(s)
- Deepika Dogra
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Paola L Meza-Santoscoy
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Cezar Gavrilovici
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
- Departments of Pediatrics, Clinical Neurosciences, Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Departments of Neurosciences, Pediatrics, and Pharmacology, Rady Children's Hospital San Diego, University of California San Diego, San Diego, California, USA
| | - Renata Rehak
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Cristiane L R de la Hoz
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Kingsley Ibhazehiebo
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Jong M Rho
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
- Departments of Pediatrics, Clinical Neurosciences, Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Departments of Neurosciences, Pediatrics, and Pharmacology, Rady Children's Hospital San Diego, University of California San Diego, San Diego, California, USA
| | - Deborah M Kurrasch
- Department of Medical Genetics, University of Calgary, Calgary, Alberta, Canada
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
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Paulhus K, Glasscock E. Novel Genetic Variants Expand the Functional, Molecular, and Pathological Diversity of KCNA1 Channelopathy. Int J Mol Sci 2023; 24:8826. [PMID: 37240170 PMCID: PMC10219020 DOI: 10.3390/ijms24108826] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 05/11/2023] [Accepted: 05/13/2023] [Indexed: 05/28/2023] Open
Abstract
The KCNA1 gene encodes Kv1.1 voltage-gated potassium channel α subunits, which are crucial for maintaining healthy neuronal firing and preventing hyperexcitability. Mutations in the KCNA1 gene can cause several neurological diseases and symptoms, such as episodic ataxia type 1 (EA1) and epilepsy, which may occur alone or in combination, making it challenging to establish simple genotype-phenotype correlations. Previous analyses of human KCNA1 variants have shown that epilepsy-linked mutations tend to cluster in regions critical for the channel's pore, whereas EA1-associated mutations are evenly distributed across the length of the protein. In this review, we examine 17 recently discovered pathogenic or likely pathogenic KCNA1 variants to gain new insights into the molecular genetic basis of KCNA1 channelopathy. We provide the first systematic breakdown of disease rates for KCNA1 variants in different protein domains, uncovering potential location biases that influence genotype-phenotype correlations. Our examination of the new mutations strengthens the proposed link between the pore region and epilepsy and reveals new connections between epilepsy-related variants, genetic modifiers, and respiratory dysfunction. Additionally, the new variants include the first two gain-of-function mutations ever discovered for KCNA1, the first frameshift mutation, and the first mutations located in the cytoplasmic N-terminal domain, broadening the functional and molecular scope of KCNA1 channelopathy. Moreover, the recently identified variants highlight emerging links between KCNA1 and musculoskeletal abnormalities and nystagmus, conditions not typically associated with KCNA1. These findings improve our understanding of KCNA1 channelopathy and promise to enhance personalized diagnosis and treatment for individuals with KCNA1-linked disorders.
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Affiliation(s)
| | - Edward Glasscock
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275, USA;
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Hassan A. Episodic Ataxias: Primary and Secondary Etiologies, Treatment, and Classification Approaches. Tremor Other Hyperkinet Mov (N Y) 2023; 13:9. [PMID: 37008993 PMCID: PMC10064912 DOI: 10.5334/tohm.747] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 03/03/2023] [Indexed: 03/30/2023] Open
Abstract
Background Episodic ataxia (EA), characterized by recurrent attacks of cerebellar dysfunction, is the manifestation of a group of rare autosomal dominant inherited disorders. EA1 and EA2 are most frequently encountered, caused by mutations in KCNA1 and CACNA1A. EA3-8 are reported in rare families. Advances in genetic testing have broadened the KCNA1 and CACNA1A phenotypes, and detected EA as an unusual presentation of several other genetic disorders. Additionally, there are various secondary causes of EA and mimicking disorders. Together, these can pose diagnostic challenges for neurologists. Methods A systematic literature review was performed in October 2022 for 'episodic ataxia' and 'paroxysmal ataxia', restricted to publications in the last 10 years to focus on recent clinical advances. Clinical, genetic, and treatment characteristics were summarized. Results EA1 and EA2 phenotypes have further broadened. In particular, EA2 may be accompanied by other paroxysmal disorders of childhood with chronic neuropsychiatric features. New treatments for EA2 include dalfampridine and fampridine, in addition to 4-aminopyridine and acetazolamide. There are recent proposals for EA9-10. EA may also be caused by gene mutations associated with chronic ataxias (SCA-14, SCA-27, SCA-42, AOA2, CAPOS), epilepsy syndromes (KCNA2, SCN2A, PRRT2), GLUT-1, mitochondrial disorders (PDHA1, PDHX, ACO2), metabolic disorders (Maple syrup urine disease, Hartnup disease, type I citrullinemia, thiamine and biotin metabolism defects), and others. Secondary causes of EA are more commonly encountered than primary EA (vascular, inflammatory, toxic-metabolic). EA can be misdiagnosed as migraine, peripheral vestibular disorders, anxiety, and functional symptoms. Primary and secondary EA are frequently treatable which should prompt a search for the cause. Discussion EA may be overlooked or misdiagnosed for a variety of reasons, including phenotype-genotype variability and clinical overlap between primary and secondary causes. EA is highly treatable, so it is important to consider in the differential diagnosis of paroxysmal disorders. Classical EA1 and EA2 phenotypes prompt single gene test and treatment pathways. For atypical phenotypes, next generation genetic testing can aid diagnosis and guide treatment. Updated classification systems for EA are discussed which may assist diagnosis and management.
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Choi HW. Fasciculations in Children. Pediatr Neurol 2021; 125:40-47. [PMID: 34628142 DOI: 10.1016/j.pediatrneurol.2021.08.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 08/19/2021] [Accepted: 08/28/2021] [Indexed: 11/26/2022]
Abstract
Fasciculations are the most common form of spontaneous muscle contraction. They frequently occur in healthy individuals. However, there are a minority of situations that fasciculations are observed in association with specific neurologic disorders. Publications concerning the evaluation of pediatric patients experiencing fasciculations are limited. These children may undergo invasive or expensive diagnostic investigations that are unnecessary. Moreover, without careful consideration of differential diagnoses, rare neuromuscular disorders that present with fasciculations in the pediatric age group can be under-recognized by pediatric neurologists. This review examines the most important pediatric disorders presenting with fasciculations and other spontaneous muscle contractions to guide pediatric neurologists in evaluating these children.
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Affiliation(s)
- Hyoung Won Choi
- Division of Pediatric Neurology, University of Pittsburgh Medical Center Children's Hospital of Pittsburgh, Lemoyne, Pennsylvania.
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Zhao J, Petitjean D, Haddad GA, Batulan Z, Blunck R. A Common Kinetic Property of Mutations Linked to Episodic Ataxia Type 1 Studied in the Shaker Kv Channel. Int J Mol Sci 2020; 21:E7602. [PMID: 33066705 DOI: 10.3390/ijms21207602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Revised: 10/09/2020] [Accepted: 10/12/2020] [Indexed: 12/21/2022] Open
Abstract
(1) Background: Episodic ataxia type 1 is caused by mutations in the KCNA1 gene encoding for the voltage-gated potassium channel Kv1.1. There have been many mutations in Kv1.1 linked to episodic ataxia reported and typically investigated by themselves or in small groups. The aim of this article is to determine whether we can define a functional parameter common to all Kv1.1 mutants that have been linked to episodic ataxia. (2) Methods: We introduced the disease mutations linked to episodic ataxia in the drosophila analog of Kv1.1, the Shaker Kv channel, and expressed the channels in Xenopus oocytes. Using the cut-open oocyte technique, we characterized the gating and ionic currents. (3) Results: We found that the episodic ataxia mutations variably altered the different gating mechanisms described for Kv channels. The common characteristic was a conductance voltage relationship and inactivation shifted to less polarized potentials. (4) Conclusions: We suggest that a combination of a prolonged action potential and slowed and incomplete inactivation leads to development of ataxia when Kv channels cannot follow or adapt to high firing rates.
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Yuan H, Yuan H, Wang Q, Ye W, Yao R, Xu W, Liu Y. Two novel KCNA1 variants identified in two unrelated Chinese families affected by episodic ataxia type 1 and neurodevelopmental disorders. Mol Genet Genomic Med 2020; 8:e1434. [PMID: 32705822 PMCID: PMC7549609 DOI: 10.1002/mgg3.1434] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 06/03/2020] [Accepted: 07/11/2020] [Indexed: 12/19/2022] Open
Abstract
Background Pathogenic KCNA1 variants have been linked to episodic ataxia type 1 (EA1), a rare neurological syndrome characterized by continuous myokymia and attacks of generalized ataxia that can be triggered by fever, abrupt movements, emotional stress, and fatigue. Currently, over 40 KCNA1 variants have been identified in individuals with EA1. Methods A male patient displayed partial seizures in addition to EA1 symptoms, often triggered by fever. A sibling presented with typical EA1 symptoms, seizures, and learning difficulties. In addition, the older brother displayed cognitive impairment, developmental delay, and slurred speech, which were absent in his younger sister. Whole‐exome sequencing was performed for the patients. Results A novel de novo missense variant in KCNA1 (p.Ala261Thr) was identified in the male patient, which is located in a base of the 3rd transmembrane domain (S3). The other novel KCNA1 variant (p.Gly376Ser) was identified in the sibling and was inherited from an unaffected father with low‐level mosaicism. The variant was located in the S5–S6 extracellular linker of the voltage sensor domain of the Kv channel. Next, we systematically reviewed the available clinical phenotypes of individuals with EA1 and observed that individuals with KCNA1 variants at the C‐terminus were more likely to suffer from seizures and neurodevelopmental disorders than those with variants at the N‐terminus. Conclusion Our study expands the mutation spectrum of KCNA1 and improves our understanding of the genotype–phenotype correlations of KCNA1. Definitive genetic diagnosis is beneficial for the genetic counseling and clinical management of individuals with EA1.
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Affiliation(s)
- Haiming Yuan
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Huihua Yuan
- Dongguan Maternal and Child Health Care HospitalDongguanChina
| | - Qingming Wang
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Wanhua Ye
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Ruixia Yao
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Wanfang Xu
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
| | - Yanhui Liu
- Dongguan Maternal and Child Health Care HospitalDongguanChina
- Dongguan Institute of Reproductive and Genetic ResearchDongguanChina
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D’Adamo MC, Liantonio A, Rolland JF, Pessia M, Imbrici P. Kv1.1 Channelopathies: Pathophysiological Mechanisms and Therapeutic Approaches. Int J Mol Sci 2020; 21:ijms21082935. [PMID: 32331416 PMCID: PMC7215777 DOI: 10.3390/ijms21082935] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 04/19/2020] [Accepted: 04/20/2020] [Indexed: 12/27/2022] Open
Abstract
Kv1.1 belongs to the Shaker subfamily of voltage-gated potassium channels and acts as a critical regulator of neuronal excitability in the central and peripheral nervous systems. KCNA1 is the only gene that has been associated with episodic ataxia type 1 (EA1), an autosomal dominant disorder characterized by ataxia and myokymia and for which different and variable phenotypes have now been reported. The iterative characterization of channel defects at the molecular, network, and organismal levels contributed to elucidating the functional consequences of KCNA1 mutations and to demonstrate that ataxic attacks and neuromyotonia result from cerebellum and motor nerve alterations. Dysfunctions of the Kv1.1 channel have been also associated with epilepsy and kcna1 knock-out mouse is considered a model of sudden unexpected death in epilepsy. The tissue-specific association of Kv1.1 with other Kv1 members, auxiliary and interacting subunits amplifies Kv1.1 physiological roles and expands the pathogenesis of Kv1.1-associated diseases. In line with the current knowledge, Kv1.1 has been proposed as a novel and promising target for the treatment of brain disorders characterized by hyperexcitability, in the attempt to overcome limited response and side effects of available therapies. This review recounts past and current studies clarifying the roles of Kv1.1 in and beyond the nervous system and its contribution to EA1 and seizure susceptibility as well as its wide pharmacological potential.
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Affiliation(s)
- Maria Cristina D’Adamo
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida MDS-2080, Malta; (M.C.D.); (M.P.)
| | - Antonella Liantonio
- Department of Pharmacy–Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy;
| | | | - Mauro Pessia
- Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida MDS-2080, Malta; (M.C.D.); (M.P.)
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain Po Box 17666, UAE
| | - Paola Imbrici
- Department of Pharmacy–Drug Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy;
- Correspondence:
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Paulhus K, Ammerman L, Glasscock E. Clinical Spectrum of KCNA1 Mutations: New Insights into Episodic Ataxia and Epilepsy Comorbidity. Int J Mol Sci 2020; 21:E2802. [PMID: 32316562 DOI: 10.3390/ijms21082802] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 12/13/2022] Open
Abstract
Mutations in the KCNA1 gene, which encodes voltage-gated Kv1.1 potassium channel α-subunits, cause a variety of human diseases, complicating simple genotype–phenotype correlations in patients. KCNA1 mutations are primarily associated with a rare neurological movement disorder known as episodic ataxia type 1 (EA1). However, some patients have EA1 in combination with epilepsy, whereas others have epilepsy alone. KCNA1 mutations can also cause hypomagnesemia and paroxysmal dyskinesia in rare cases. Why KCNA1 variants are associated with such phenotypic heterogeneity in patients is not yet understood. In this review, literature databases (PubMed) and public genetic archives (dbSNP and ClinVar) were mined for known pathogenic or likely pathogenic mutations in KCNA1 to examine whether patterns exist between mutation type and disease manifestation. Analyses of the 47 deleterious KCNA1 mutations that were identified revealed that epilepsy or seizure-related variants tend to cluster in the S1/S2 transmembrane domains and in the pore region of Kv1.1, whereas EA1-associated variants occur along the whole length of the protein. In addition, insights from animal models of KCNA1 channelopathy were considered, as well as the possible influence of genetic modifiers on disease expressivity and severity. Elucidation of the complex relationship between KCNA1 variants and disease will enable better diagnostic risk assessment and more personalized therapeutic strategies for KCNA1 channelopathy.
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Abstract
Essential tremor (ET) is a neurological movement disorder characterised by bilateral limb kinetic/postural tremor, with or without tremor in other body parts including head, voice and lower limbs. Since no causative genes for ET have been identified, it is likely that the disorder occurs as a result of complex genetic factors interacting with various cellular and environmental factors that can result in abnormal function of circuitry involving the cerebello-thalamo-cortical pathway. Genetic analyses have uncovered at least 14 loci and 11 genes that are related to ET, as well as various risk or protective genetic factors. Limitations in ET genetic analyses include inconsistent disease definition, small sample size, varied ethnic backgrounds and many other factors that may contribute to paucity of relevant genetic data in ET. Genetic analyses, coupled with functional and animal studies, have led to better insights into possible pathogenic mechanisms underlying ET. These genetic studies may guide the future development of genetic testing and counselling, and specific, pathogenesis-targeted, therapeutic strategies.
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10
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Abstract
Introduction: Paroxysmal dyskinesias and episodic ataxias are often caused by mutations in genes related to cell membrane and synaptic function. Despite the exponential increase in publications of genetically confirmed cases, management remains largely clinical based on non-systematic evidence. Areas covered: The authors provide a historical and clinical review of the main types of paroxysmal dyskinesias and episodic ataxias, with recommendations for diagnosis and management of patients suffering from these conditions. Expert opinion: After secondary paroxysmal dyskinesias, the most common paroxysmal movement disorders are likely to be PRRT2-associated paroxysmal kinesigenic dyskinesias, which respond well to small doses of carbamazepine, and episodic ataxia type 2, which often responds to acetazolamide. Familial paroxysmal non-kinesigenic dyskinesias are largely caused by mutations in PNKD and have poor response to therapy but improve with age. Exercise-induced dyskinesias are genetically heterogeneous, caused by disorders of glucose transport, mitochondrial function, dopaminergic pathways or neurodegenerative conditions amongst others. GNAO1 and ADCY5 mutations can also cause paroxysmal movement disorders, often in the context of ongoing motor symptoms. Although a therapeutic trial is justified for classic cases and in limited resource settings, genetic testing may help direct initial or rescue therapy. Deep brain stimulation may be an option for severe cases.
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Affiliation(s)
- Claudio M De Gusmao
- Department of Neurology, Harvard Medical School, Boston Children's Hospital , Boston , MA , USA.,Department of Neurology, Universidade Estadual de Campinas (UNICAMP) , São Paulo , Brazil
| | - Laura Silveira-Moriyama
- Department of Neurology, Universidade Estadual de Campinas (UNICAMP) , São Paulo , Brazil.,Education Unit, UCL Institute of Neurology, University College London , London , UK.,Department of Neurology, Hospital Bairral, Fundação Espírita Américo Bairral , Itapira , Brazil
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Yin XM, Lin JH, Cao L, Zhang TM, Zeng S, Zhang KL, Tian WT, Hu ZM, Li N, Wang JL, Guo JF, Wang RX, Xia K, Zhang ZH, Yin F, Peng J, Liao WP, Yi YH, Liu JY, Yang ZX, Chen Z, Mao X, Yan XX, Jiang H, Shen L, Chen SD, Zhang LM, Tang BS. Familial paroxysmal kinesigenic dyskinesia is associated with mutations in the KCNA1 gene. Hum Mol Genet 2019; 27:625-637. [PMID: 29294000 DOI: 10.1093/hmg/ddx430] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 12/15/2017] [Indexed: 12/23/2022] Open
Abstract
Paroxysmal kinesigenic dyskinesia (PKD) is a heterogeneous movement disorder characterized by recurrent dyskinesia attacks triggered by sudden movement. PRRT2 has been identified as the first causative gene of PKD. However, it is only responsible for approximately half of affected individuals, indicating that other loci are most likely involved in the etiology of this disorder. To explore the underlying causative gene of PRRT2-negative PKD, we used a combination strategy including linkage analysis, whole-exome sequencing and copy number variations analysis to detect the genetic variants within a family with PKD. We identified a linkage locus on chromosome 12 (12p13.32-12p12.3) and detected a novel heterozygous mutation c.956 T>G (p.319 L>R) in the potassium voltage-gated channel subfamily A member 1, KCNA1. Whole-exome sequencing in another 58 Chinese patients with PKD who lacked mutations in PRRT2 revealed another novel mutation in the KCNA1 gene [c.765 C>A (p.255 N>K)] within another family. Biochemical analysis revealed that the L319R mutant accelerated protein degradation via the proteasome pathway and disrupted membrane expression of the Kv1.1 channel. Electrophysiological examinations in transfected HEK293 cells showed that both the L319R and N255K mutants resulted in reduced potassium currents and respective altered gating properties, with a dominant negative effect on the Kv1.1 wild-type channel. Our study suggests that these mutations in KCNA1 cause the Kv1.1 channel dysfunction, which leads to familial PKD. The current study further extended the genotypic spectrum of this disorder, indicating that Kv1.1 channel dysfunction maybe one of the underlying defects in PKD.
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Affiliation(s)
- Xiao-Meng Yin
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Jing-Han Lin
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, China
| | - Li Cao
- Department of Neurology and Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Tong-Mei Zhang
- Department of Physiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.,The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Sheng Zeng
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Kai-Lin Zhang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Wo-Tu Tian
- Department of Neurology and Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Zheng-Mao Hu
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Nan Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Jun-Ling Wang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Ji-Feng Guo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Ruo-Xi Wang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,Institute of Precision Medicine, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Kun Xia
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China
| | - Zhuo-Hua Zhang
- Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,Institute of Precision Medicine, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Department of Neurosciences, School of Medicine, University of South China, Hengyang, Hunan 420001, China
| | - Fei Yin
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Hunan Intellectual and Development Disabilities Research Center, Changsha, Hunan 410008, China
| | - Jing Peng
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Hunan Intellectual and Development Disabilities Research Center, Changsha, Hunan 410008, China
| | - Wei-Ping Liao
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and Ministry of Education of China, Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Institute of Neuroscience, Guangzhou Medical University, Guangzhou 510260, China
| | - Yong-Hong Yi
- Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and Ministry of Education of China, Department of Neurology of the Second Affiliated Hospital of Guangzhou Medical University, Institute of Neuroscience, Guangzhou Medical University, Guangzhou 510260, China
| | - Jing-Yu Liu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology and Center for Human Genome Research, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhi-Xian Yang
- Department of Pediatrics, Peking University First Hospital, Beijing 100034, China
| | - Zhong Chen
- Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Department of Pharmacology, College of Pharmaceutical Sciences, School of Medicine, Zhejiang University, Hangzhou 310027, China.,Epilepsy Center, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310027, China
| | - Xiao Mao
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Xin-Xiang Yan
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - Hong Jiang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Lu Shen
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China
| | - Sheng-Di Chen
- Department of Neurology and Institute of Neurology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Li-Ming Zhang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, China
| | - Bei-Sha Tang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China.,Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410008, China.,National Clinical Research Center for Geriatric Disorders, Central South University, Changsha, Hunan 410008, China.,Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, Hunan 410008, China.,Collaborative Innovation Center for Brain Science, Shanghai 200032, China.,Collaborative Innovation Center for Genetics and Development, Shanghai 200433, China
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Mcgovern EM, Roze E, Counihan TJ. The expanding spectrum of paroxysmal movement disorders: update from clinical features to therapeutics. Curr Opin Neurol 2018; 31:491-7. [DOI: 10.1097/wco.0000000000000576] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Zima L, Ceulemans S, Reiner G, Galosi S, Chen D, Sahagian M, Haas RH, Hyland K, Friedman J. Paroxysmal motor disorders: expanding phenotypes lead to coalescing genotypes. Ann Clin Transl Neurol 2018; 5:996-1010. [PMID: 30128325 PMCID: PMC6093839 DOI: 10.1002/acn3.597] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 05/28/2018] [Accepted: 05/29/2018] [Indexed: 11/07/2022] Open
Abstract
Paroxysmal movement disorders encompass varied motor phenomena. Less recognized features and wide phenotypic and genotypic heterogeneity are impediments to straightforward molecular diagnosis. We describe a family with episodic ataxia type 1, initially mis‐characterized as paroxysmal dystonia to illustrate this diagnostic challenge. We summarize clinical features in affected individuals to highlight underappreciated aspects and provide comprehensive phenotypic description of the rare familial KCNA1 mutation. Delayed diagnosis in this family is emblematic of the broader challenge of diagnosing other paroxysmal motor disorders. We summarize genotypic and phenotypic overlap and provide a suggested diagnostic algorithm for approaching patients with these conditions.
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Affiliation(s)
- Laura Zima
- University of Nebraska Medical Center Omaha Nebraska
| | - Sophia Ceulemans
- Division of Neurology Rady Children's Hospital San Diego California
| | - Gail Reiner
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Neurosciences University of California San Diego San Diego California
| | - Serena Galosi
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Neurosciences University of California San Diego San Diego California.,Department of Human Neuroscience Child Neurology and Psychiatry Sapienza University Rome Italy
| | - Dillon Chen
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Neurosciences University of California San Diego San Diego California
| | - Michelle Sahagian
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Neurosciences University of California San Diego San Diego California
| | - Richard H Haas
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Pediatrics University of California San Diego San Diego California.,Department of Neurosciences University of California San Diego San Diego California
| | - Keith Hyland
- Medical Neurogenetics Laboratories Atlanta Georgia
| | - Jennifer Friedman
- Division of Neurology Rady Children's Hospital San Diego California.,Department of Pediatrics University of California San Diego San Diego California.,Department of Neurosciences University of California San Diego San Diego California.,Rady Children's Institute for Genomic Medicine San Diego California
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Smith P, Arias R, Sonti S, Odgerel Z, Santa-Maria I, McCabe BD, Tsaneva-Atanasova K, Louis ED, Hodge JJL, Clark LN. A Drosophila Model of Essential Tremor. Sci Rep 2018; 8:7664. [PMID: 29769701 DOI: 10.1038/s41598-018-25949-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 04/25/2018] [Indexed: 11/30/2022] Open
Abstract
Essential Tremor (ET) is one of the most common neurological diseases, with an estimated 7 million affected individuals in the US; the pathophysiology of the disorder is poorly understood. Recently, we identified a mutation (KCNS2 (Kv9.2), c.1137 T > A, p.(D379E) in an electrically silent voltage-gated K+ channel α-subunit, Kv9.2, in a family with ET, that modulates the activity of Kv2 channels. We have produced transgenic Drosophila lines that express either the human wild type Kv9.2 (hKv9.2) or the ET causing mutant Kv9.2 (hKv9.2-D379E) subunit in all neurons. We show that the hKv9.2 subunit modulates activity of endogenous Drosophila K+ channel Shab. The mutant hKv9.2-D379E subunit showed significantly higher levels of Shab inactivation and a higher frequency of spontaneous firing rate consistent with neuronal hyperexcitibility. We also observed behavioral manifestations of nervous system dysfunction including effects on night time activity and sleep. This functional data further supports the pathogenicity of the KCNS2 (p.D379E) mutation, consistent with our prior observations including co-segregation with ET in a family, a likely pathogenic change in the channel pore domain and absence from population databases. The Drosophila hKv9.2 transgenic model recapitulates several features of ET and may be employed to advance our understanding of ET disease pathogenesis.
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Abstract
The familial episodic ataxias (EAs) are prototypical channelopathies in the central nervous system clinically characterized by attacks of imbalance and incoordination variably associated with progressive ataxia and variable interictal features. EA1, EA2, and EA6 are caused by mutations in ion channel- and transporter-encoding genes that regulate neuronal excitability and neurotransmission.
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Affiliation(s)
- Joanna C Jen
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA, United States; Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, CA, United States.
| | - Jijun Wan
- Department of Neurology, David Geffen School of Medicine, University of California, Los Angeles, CA, United States
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Corbett MA, Bellows ST, Li M, Carroll R, Micallef S, Carvill GL, Myers CT, Howell KB, Maljevic S, Lerche H, Gazina EV, Mefford HC, Bahlo M, Berkovic SF, Petrou S, Scheffer IE, Gecz J. Dominant KCNA2 mutation causes episodic ataxia and pharmacoresponsive epilepsy. Neurology 2016; 87:1975-1984. [PMID: 27733563 DOI: 10.1212/wnl.0000000000003309] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 07/26/2016] [Indexed: 01/14/2023] Open
Abstract
OBJECTIVE To identify the genetic basis of a family segregating episodic ataxia, infantile seizures, and heterogeneous epilepsies and to study the phenotypic spectrum of KCNA2 mutations. METHODS A family with 7 affected individuals over 3 generations underwent detailed phenotyping. Whole genome sequencing was performed on a mildly affected grandmother and her grandson with epileptic encephalopathy (EE). Segregating variants were filtered and prioritized based on functional annotations. The effects of the mutation on channel function were analyzed in vitro by voltage clamp assay and in silico by molecular modeling. KCNA2 was sequenced in 35 probands with heterogeneous phenotypes. RESULTS The 7 family members had episodic ataxia (5), self-limited infantile seizures (5), evolving to genetic generalized epilepsy (4), focal seizures (2), and EE (1). They had a segregating novel mutation in the shaker type voltage-gated potassium channel KCNA2 (CCDS_827.1: c.765_773del; p.255_257del). A rare missense SCN2A (rs200884216) variant was also found in 2 affected siblings and their unaffected mother. The p.255_257del mutation caused dominant negative loss of channel function. Molecular modeling predicted repositioning of critical arginine residues in the voltage-sensing domain. KCNA2 sequencing revealed 1 de novo mutation (CCDS_827.1: c.890G>A; p.Arg297Gln) in a girl with EE, ataxia, and tremor. CONCLUSIONS A KCNA2 mutation caused dominantly inherited episodic ataxia, mild infantile-onset seizures, and later generalized and focal epilepsies in the setting of normal intellect. This observation expands the KCNA2 phenotypic spectrum from EE often associated with chronic ataxia, reflecting the marked variation in severity observed in many ion channel disorders.
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Affiliation(s)
- Mark A Corbett
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Susannah T Bellows
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Melody Li
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Renée Carroll
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Silvana Micallef
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Gemma L Carvill
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Candace T Myers
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Katherine B Howell
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Snezana Maljevic
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Holger Lerche
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Elena V Gazina
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Heather C Mefford
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Melanie Bahlo
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Samuel F Berkovic
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Steven Petrou
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia
| | - Ingrid E Scheffer
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia.
| | - Jozef Gecz
- From the School of Medicine and Robinson Research Institute (M.A.C., R.C., J.G.) and School of Biological Sciences (J.G.), The University of Adelaide; Epilepsy Research Centre, Department of Medicine (S.T.B., S. Micallef, S.F.B., I.E.S.), University of Melbourne, Austin Health, Heidelberg; Florey Institute of Neuroscience and Mental Health (M.L., S. Maljevic, E.V.G., S.P., I.E.S.), Melbourne; Division of Genetic Medicine, Department of Pediatrics (G.L.C., C.T.M., H.C.M.), University of Washington, Seattle; Department of Neurology (K.B.H., I.E.S.), Royal Children's Hospital; Neurosciences Group (K.B.H.), Murdoch Childrens Research Institute, Melbourne; Department of Paediatrics (K.B.H.), University of Melbourne, Royal Children's Hospital, Parkville, Australia; Department of Neurology and Epileptology (S. Maljevic, H.L.), Hertie Institute for Clinical Brain Research, University of Tübingen, Germany; The Walter and Eliza Hall Institute of Medical Research (M.B.); Department of Medical Biology (M.B.), The University of Melbourne, Parkville; and Department of Medicine, Royal Melbourne Hospital (S.P.), The University of Melbourne, Australia.
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17
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Liu X, Hernandez N, Kisselev S, Floratos A, Sawle A, Ionita-Laza I, Ottman R, Louis ED, Clark LN. Identification of candidate genes for familial early-onset essential tremor. Eur J Hum Genet 2016; 24:1009-15. [PMID: 26508575 PMCID: PMC5070884 DOI: 10.1038/ejhg.2015.228] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 09/23/2015] [Accepted: 09/24/2015] [Indexed: 12/17/2022] Open
Abstract
Essential tremor (ET) is one of the most common causes of tremor in humans. Despite its high heritability and prevalence, few susceptibility genes for ET have been identified. To identify ET genes, whole-exome sequencing was performed in 37 early-onset ET families with an autosomal-dominant inheritance pattern. We identified candidate genes for follow-up functional studies in five ET families. In two independent families, we identified variants predicted to affect function in the nitric oxide (NO) synthase 3 gene (NOS3) that cosegregated with disease. NOS3 is highly expressed in the central nervous system (including cerebellum), neurons and endothelial cells, and is one of three enzymes that converts l-arginine to the neurotransmitter NO. In one family, a heterozygous variant, c.46G>A (p.(Gly16Ser)), in NOS3, was identified in three affected ET cases and was absent in an unaffected family member; and in a second family, a heterozygous variant, c.164C>T (p.(Pro55Leu)), was identified in three affected ET cases (dizygotic twins and their mother). Both variants result in amino-acid substitutions of highly conserved amino-acid residues that are predicted to be deleterious and damaging by in silico analysis. In three independent families, variants predicted to affect function were also identified in other genes, including KCNS2 (KV9.2), HAPLN4 (BRAL2) and USP46. These genes are highly expressed in the cerebellum and Purkinje cells, and influence function of the gamma-amino butyric acid (GABA)-ergic system. This is in concordance with recent evidence that the pathophysiological process in ET involves cerebellar dysfunction and possibly cerebellar degeneration with a reduction in Purkinje cells, and a decrease in GABA-ergic tone.
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Affiliation(s)
- Xinmin Liu
- Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Nora Hernandez
- Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT, USA
- Department of Chronic Disease Epidemiology, Yale School of Public Health, New Haven, CT, USA
| | - Sergey Kisselev
- Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Aris Floratos
- Department of Biomedical Informatics, Columbia University, New York, NY, USA
- Center for Computational Biology and Bioinformatics, Columbia University, New York, NY, USA
| | - Ashley Sawle
- Department of Biomedical Informatics, Columbia University, New York, NY, USA
- Center for Computational Biology and Bioinformatics, Columbia University, New York, NY, USA
| | - Iuliana Ionita-Laza
- Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, NY, USA
| | - Ruth Ottman
- G.H Sergievsky Center, Columbia University, New York, NY, USA
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
- Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA
- Division of Epidemiology, New York State Psychiatric Institute, New York, NY, USA
| | - Elan D Louis
- Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT, USA
- Department of Chronic Disease Epidemiology, Yale School of Public Health, New Haven, CT, USA
| | - Lorraine N Clark
- Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY, USA
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18
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Mestre TA, Manole A, MacDonald H, Riazi S, Kraeva N, Hanna MG, Lang AE, Männikkö R, Yoon G. A novel KCNA1 mutation in a family with episodic ataxia and malignant hyperthermia. Neurogenetics 2016; 17:245-9. [PMID: 27271339 DOI: 10.1007/s10048-016-0486-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 05/26/2016] [Indexed: 10/21/2022]
Abstract
Episodic ataxia type 1 (EA1) is an autosomal dominant channelopathy caused by mutations in KCNA1, which encodes the voltage-gated potassium channel, Kv1.1. Eleven members of an EA family were evaluated with molecular and functional studies. A novel c.746T>G (p.Phe249Cys) missense mutation of KCNA1 segregated in the family members with episodic ataxia, myokymia, and malignant hyperthermia susceptibility. No mutations were found in the known malignant hyperthermia genes RYR1 or CACNA1S. The Phe249Cys-Kv1.1 channels did not show any currents upon functional expression, confirming a pathogenic role of the mutation. Malignant hyperthermia may be a presentation of KCNA1 mutations, which has significant implications for the clinical care of these patients and illustrates the phenotypic heterogeneity of KCNA1 mutations.
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19
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Chen SH, Fu SJ, Huang JJ, Tang CY. The episodic ataxia type 1 mutation I262T alters voltage-dependent gating and disrupts protein biosynthesis of human Kv1.1 potassium channels. Sci Rep 2016; 6:19378. [PMID: 26778656 PMCID: PMC4726062 DOI: 10.1038/srep19378] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 12/07/2015] [Indexed: 01/08/2023] Open
Abstract
Voltage-gated potassium (Kv) channels are essential for setting neuronal membrane excitability. Mutations in human Kv1.1 channels are linked to episodic ataxia type 1 (EA1). The EA1-associated mutation I262T was identified from a patient with atypical phenotypes. Although a previous report has characterized its suppression effect, several key questions regarding the impact of the I262T mutation on Kv1.1 as well as other members of the Kv1 subfamily remain unanswered. Herein we show that the dominant-negative effect of I262T on Kv1.1 current expression is not reversed by co-expression with Kvβ1.1 or Kvβ2 subunits. Biochemical examinations indicate that I262T displays enhanced protein degradation and impedes membrane trafficking of Kv1.1 wild-type subunits. I262T appears to be the first EA1 mutation directly associated with impaired protein stability. Further functional analyses demonstrate that I262T changes the voltage-dependent activation and Kvβ1.1-mediated inactivation, uncouples inactivation from activation gating, and decelerates the kinetics of cumulative inactivation of Kv1.1 channels. I262T also exerts similar dominant effects on the gating of Kv1.2 and Kv1.4 channels. Together our data suggest that I262T confers altered channel gating and reduced functional expression of Kv1 channels, which may account for some of the phenotypes of the EA1 patient.
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Affiliation(s)
- Szu-Han Chen
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ssu-Ju Fu
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Jing-Jia Huang
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chih-Yung Tang
- Department of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.,Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
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20
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D'Adamo MC, Hasan S, Guglielmi L, Servettini I, Cenciarini M, Catacuzzeno L, Franciolini F. New insights into the pathogenesis and therapeutics of episodic ataxia type 1. Front Cell Neurosci 2015; 9:317. [PMID: 26347608 PMCID: PMC4541215 DOI: 10.3389/fncel.2015.00317] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 07/30/2015] [Indexed: 11/13/2022] Open
Abstract
Episodic ataxia type 1 (EA1) is a K+channelopathy characterized by a broad spectrum of symptoms. Generally, patients may experience constant myokymia and dramatic episodes of spastic contractions of the skeletal muscles of the head, arms, and legs with loss of both motor coordination and balance. During attacks additional symptoms may be reported such as vertigo, blurred vision, diplopia, nausea, headache, diaphoresis, clumsiness, stiffening of the body, dysarthric speech, and difficulty in breathing. These episodes may be precipitated by anxiety, emotional stress, fatigue, startle response or sudden postural changes. Epilepsy is overrepresented in EA1. The disease is inherited in an autosomal dominant manner, and genetic analysis of several families has led to the discovery of a number of point mutations in the voltage-dependent K+ channel gene KCNA1 (Kv1.1), on chromosome 12p13. To date KCNA1 is the only gene known to be associated with EA1. Functional studies have shown that these mutations impair Kv1.1 channel function with variable effects on channel assembly, trafficking and biophysics. Despite the solid evidence obtained on the molecular mechanisms underlying EA1, how these cause dysfunctions within the central and peripheral nervous systems circuitries remains elusive. This review summarizes the main breakthrough findings in EA1, discusses the neurophysiological mechanisms underlying the disease, current therapies, future challenges and opens a window onto the role of Kv1.1 channels in central nervous system (CNS) and peripheral nervous system (PNS) functions.
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Affiliation(s)
- Maria Cristina D'Adamo
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Sonia Hasan
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Luca Guglielmi
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Ilenio Servettini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Marta Cenciarini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia Perugia, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
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21
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Syrbe S, Hedrich UB, Riesch E, Djémié T, Müller S, Møller RS, Maher B, Hernandez-Hernandez L, Synofzik M, Caglayan HS, Arslan M, Serratosa JM, Nothnagel M, May P, Krause R, Löffler H, Detert K, Dorn T, Vogt H, Krämer G, Schöls L, Mullis PE, Linnankivi T, Lehesjoki AE, Sterbova K, Craiu DC, Hoffman-Zacharska D, Korff CM, Weber YG, Steinlin M, Gallati S, Bertsche A, Bernhard MK, Merkenschlager A, Kiess W, Gonzalez M, Züchner S, Palotie A, Suls A, De Jonghe P, Helbig I, Biskup S, Wolff M, Maljevic S, Schüle R, Sisodiya SM, Weckhuysen S, Lerche H, Lemke JR. De novo loss- or gain-of-function mutations in KCNA2 cause epileptic encephalopathy. Nat Genet 2015; 47:393-399. [PMID: 25751627 PMCID: PMC4380508 DOI: 10.1038/ng.3239] [Citation(s) in RCA: 188] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 02/06/2015] [Indexed: 02/07/2023]
Abstract
Epileptic encephalopathies are a phenotypically and genetically heterogeneous group of severe epilepsies accompanied by intellectual disability and other neurodevelopmental features. Using next-generation sequencing, we identified four different de novo mutations in KCNA2, encoding the potassium channel KV1.2, in six isolated patients with epileptic encephalopathy (one mutation recurred three times independently). Four individuals presented with febrile and multiple afebrile, often focal seizure types, multifocal epileptiform discharges strongly activated by sleep, mild to moderate intellectual disability, delayed speech development and sometimes ataxia. Functional studies of the two mutations associated with this phenotype showed almost complete loss of function with a dominant-negative effect. Two further individuals presented with a different and more severe epileptic encephalopathy phenotype. They carried mutations inducing a drastic gain-of-function effect leading to permanently open channels. These results establish KCNA2 as a new gene involved in human neurodevelopmental disorders through two different mechanisms, predicting either hyperexcitability or electrical silencing of KV1.2-expressing neurons.
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Affiliation(s)
- Steffen Syrbe
- Department of Women and Child Health, Hospital for Children and Adolescents, University of Leipzig, Leipzig, Germany.
| | - Ulrike B.S. Hedrich
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
| | - Erik Riesch
- Center for Genomics and Transcriptomics (CeGaT) GmbH, Tübingen, Germany.
- Division of Human Genetics, University Children’s Hospital Inselspital, Bern, Switzerland.
- Swiss Epilepsy Center, Zürich, Switzerland.
| | - Tania Djémié
- Neurogenetics group, Department of Molecular Genetics, VIB, Antwerp, Belgium.
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium.
| | - Stephan Müller
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
| | - Rikke S. Møller
- Danish Epilepsy Center, Dianalund, Denmark
- Institute for Regional Health Services, University of Southern Denmark, Odense, Denmark.
| | - Bridget Maher
- Department of Clinical and Experimental Epilepsy, University College London Institute of Neurology, Queen Square, London, WC1N 3BG, UK
- Epilepsy Society, Chalfont-St-Peter, Bucks, SL9 0RJ, UK.
| | - Laura Hernandez-Hernandez
- Department of Clinical and Experimental Epilepsy, University College London Institute of Neurology, Queen Square, London, WC1N 3BG, UK
- Epilepsy Society, Chalfont-St-Peter, Bucks, SL9 0RJ, UK.
| | - Matthis Synofzik
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
- German Research Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Hande S. Caglayan
- Department of Molecular Biology and Genetics, Bogazici University, Istanbul, Turkey.
| | - Mutluay Arslan
- Gulhane Military Medical School, Division of Child Neurology, Ankara, Turkey.
| | - José M. Serratosa
- Neurology Lab and Epilepsy Unit, Department of Neurology, IIS — Fundación Jiménez Díaz, UAM, Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.
| | - Michael Nothnagel
- Cologne Center for Genomics, University of Colgone, Cologne, Germany
| | - Patrick May
- Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Roland Krause
- Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Heidrun Löffler
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
| | - Katja Detert
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
| | | | | | | | - Ludger Schöls
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
- German Research Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Primus E. Mullis
- Division of Pediatric Endocrinology, University Children’s Hospital Inselspital, Bern, Switzerland.
| | - Tarja Linnankivi
- Pediatric Neurology, Children’s Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
| | - Anna-Elina Lehesjoki
- Folkhälsan Institute of Genetics, Helsinki, Helsinki, Finland.
- Neuroscience Center, University of Helsinki, Helsinki, Finland
- Research Program’s Unit, Molecular Neurology, University of Helsinki, Helsinki, Finland
| | - Katalin Sterbova
- Child Neurology Department, 2nd Faculty of Medicine, Charles University, Motol Hospital, Prague, Czech Republic.
| | - Dana C. Craiu
- Pediatric Neurology Clinic II, Department of Neurology, Pediatric Neurology, Psychiatry, and Neurosurgery, “Carol Davila” University of Medicine, Sector 4, Bucharest, Romania.
- Pediatric Neurology Clinic, “Professor Doctor Alexandru Obregia” Clinical Hospital, Sector 4, Bucharest, Romania.
| | | | - Christian M. Korff
- Child and Adolescent Department, Pediatric Neurology, University Hospitals, Geneva, Switzerland.
| | - Yvonne G. Weber
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
| | - Maja Steinlin
- Division of Neuropediatrics, University Children’s Hospital Inselspital, Bern, Switzerland.
| | - Sabina Gallati
- Division of Human Genetics, University Children’s Hospital Inselspital, Bern, Switzerland.
| | - Astrid Bertsche
- Department of Women and Child Health, Hospital for Children and Adolescents, University of Leipzig, Leipzig, Germany.
| | - Matthias K. Bernhard
- Department of Women and Child Health, Hospital for Children and Adolescents, University of Leipzig, Leipzig, Germany.
| | - Andreas Merkenschlager
- Department of Women and Child Health, Hospital for Children and Adolescents, University of Leipzig, Leipzig, Germany.
| | - Wieland Kiess
- Department of Women and Child Health, Hospital for Children and Adolescents, University of Leipzig, Leipzig, Germany.
| | | | - Michael Gonzalez
- Dr. JT MacDonald Department for Human Genetics, Hussman Institute for Human Genomics, University of Miami, Miami, USA
| | - Stephan Züchner
- Dr. JT MacDonald Department for Human Genetics, Hussman Institute for Human Genomics, University of Miami, Miami, USA
| | - Aarno Palotie
- Institute for Molecular Medicine Finland, University of Helsinki, Helsinki, Finland
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, UK.
- Psychiatric & Neurodevelopmental Genetics Unit, Department of Psychiatry, Massachusetts General Hospital, Boston, MA, 02114, USA
| | - Arvid Suls
- Neurogenetics group, Department of Molecular Genetics, VIB, Antwerp, Belgium.
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium.
| | - Peter De Jonghe
- Neurogenetics group, Department of Molecular Genetics, VIB, Antwerp, Belgium.
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium.
- Department of Neurology, Antwerp University Hospital, University of Antwerp, Antwerp, Belgium
| | - Ingo Helbig
- Department of Neuropediatrics, Christian-Albrechts-University of Kiel, Germany.
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, USA
| | - Saskia Biskup
- Center for Genomics and Transcriptomics (CeGaT) GmbH, Tübingen, Germany.
| | - Markus Wolff
- Department of Neuropediatrics, University of Tübingen, Tübingen, Germany.
| | - Snezana Maljevic
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
| | - Rebecca Schüle
- Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
- German Research Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
- Division of Neuropediatrics, University Children’s Hospital Inselspital, Bern, Switzerland.
| | - Sanjay M. Sisodiya
- Department of Clinical and Experimental Epilepsy, University College London Institute of Neurology, Queen Square, London, WC1N 3BG, UK
- Epilepsy Society, Chalfont-St-Peter, Bucks, SL9 0RJ, UK.
| | - Sarah Weckhuysen
- Neurogenetics group, Department of Molecular Genetics, VIB, Antwerp, Belgium.
- Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium.
| | - Holger Lerche
- Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.
| | - Johannes R. Lemke
- Department of Women and Child Health, Hospital for Children and Adolescents, University of Leipzig, Leipzig, Germany.
- Division of Human Genetics, University Children’s Hospital Inselspital, Bern, Switzerland.
- Department of Diagnostics, Institute of Human Genetics, University of Leipzig, Leipzig, Germany.
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22
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Tacik P, Guthrie KJ, Strongosky AJ, Broderick DF, Riegert-Johnson DL, Tang S, El-Khechen D, Parker AS, Ross OA, Wszolek ZK. Whole-exome sequencing as a diagnostic tool in a family with episodic ataxia type 1. Mayo Clin Proc 2015; 90:366-71. [PMID: 25659636 PMCID: PMC4354704 DOI: 10.1016/j.mayocp.2015.01.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 12/18/2014] [Accepted: 01/02/2015] [Indexed: 11/23/2022]
Abstract
Complex neurologic phenotypes are inherently difficult to diagnose. Whole-exome sequencing (WES) is a new tool in the neurologist's diagnostic armamentarium. Whole-exome sequencing can be applied to investigate the "diagnostic odyssey" cases. These cases involve patients with rare diseases that likely have a genetic etiology but have failed to be diagnosed by clinical evaluation and targeted gene testing. We describe such a case, a 22-year-old man who had mild intellectual developmental disability and episodes of jerking ataxic movements that affected his whole body. He underwent numerous multidisciplinary and multicentric evaluations throughout his life that failed to establish a clear diagnosis. Following his visit to Mayo Clinic in Jacksonville, Florida, WES was applied for genetic determination of the unknown disorder in the proband and his biological parents and sister. Additional clinical evaluation, magnetic resonance neuroimaging, electromyography, and electroencephalography of the proband were performed to verify the phenotype after the WES results were available. To our knowledge, this is the first report of the application of WES to facilitate the diagnosis of episodic ataxia type 1. This case illustrates that WES supported by clinical data is a useful and time-saving tool in the evaluation of patients with rare and complex hereditary disorders.
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Affiliation(s)
- Pawel Tacik
- Department of Neurology, Mayo Clinic, Jacksonville, FL
| | | | | | | | | | - Sha Tang
- Ambry Genetics Corp, Aliso Viejo, CA
| | | | | | - Owen A Ross
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL
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23
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D'Adamo MC, Gallenmüller C, Servettini I, Hartl E, Tucker SJ, Arning L, Biskup S, Grottesi A, Guglielmi L, Imbrici P, Bernasconi P, Di Giovanni G, Franciolini F, Catacuzzeno L, Pessia M, Klopstock T. Novel phenotype associated with a mutation in the KCNA1(Kv1.1) gene. Front Physiol 2015; 5:525. [PMID: 25642194 PMCID: PMC4295438 DOI: 10.3389/fphys.2014.00525] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/20/2014] [Indexed: 11/13/2022] Open
Abstract
Episodic ataxia type 1 (EA1) is an autosomal dominant K(+) channelopathy which manifests with short attacks of cerebellar ataxia and dysarthria, and may also show interictal myokymia. Episodes can be triggered by emotional or physical stress, startle response, sudden postural change or fever. Here we describe a 31-year-old man displaying markedly atypical symptoms, including long-lasting attacks of jerking muscle contractions associated with hyperthermia, severe migraine, and a relatively short-sleep phenotype. A single nucleotide change in KCNA1 (c.555C>G) was identified that changes a highly conserved residue (p.C185W) in the first transmembrane segment of the voltage-gated K(+) channel Kv1.1. The patient is heterozygous and the mutation was inherited from his asymptomatic mother. Next generation sequencing revealed no variations in the CACNA1A, CACNB4, KCNC3, KCNJ10, PRRT2 or SCN8A genes of either the patient or mother, except for a benign variant in SLC1A3. Functional analysis of the p.C185W mutation in KCNA1 demonstrated a deleterious dominant-negative phenotype where the remaining current displayed slower activation kinetics, subtle changes in voltage-dependence and faster recovery from slow inactivation. Structural modeling also predicts the C185W mutation to be functionally deleterious. This description of novel clinical features, associated with a Kv1.1 mutation highlights a possibly unrecognized relationship between K(+) channel dysfunction, hyperthermia and migraine in EA1, and suggests that thorough assessments for these symptoms should be carefully considered for all patients affected by EA1.
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Affiliation(s)
- Maria C D'Adamo
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia Perugia, Italy ; Section of Neurophysiology and Biophysics, Istituto Euro-Mediterraneo di Scienza e Tecnologia Palermo, Italy
| | - Constanze Gallenmüller
- Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Germany ; German Network for Mitochondrial Disorders (mitoNET) Ludwigshafen, Germany ; DZNE - German Center for Neurodegenerative Diseases Munich, Germany
| | - Ilenio Servettini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia Perugia, Italy
| | - Elisabeth Hartl
- Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Germany
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford Oxford, UK
| | - Larissa Arning
- Department of Human Genetics, Ruhr-University Bochum Bochum, Germany
| | - Saskia Biskup
- Center for Genomics and Transcriptomics (CeGaT) GmbH Tübingen Tübingen, Germany
| | - Alessandro Grottesi
- Department of Supercomputing Applications and Innovation, CINECA (Consorzio Inter-Universitario per il Calcolo Automatico) Rome, Italy
| | - Luca Guglielmi
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia Perugia, Italy
| | - Paola Imbrici
- Department of Pharmacy, University of Bari Bari, Italy
| | - Pia Bernasconi
- Neurology IV - Neuromuscular Diseases and Neuroimmunology Unit, Foundation IRCCS Neurological Institute "Carlo Besta" Milan, Italy
| | - Giuseppe Di Giovanni
- Section of Neurophysiology and Biophysics, Istituto Euro-Mediterraneo di Scienza e Tecnologia Palermo, Italy ; Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta Msida, Malta
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia Perugia, Italy
| | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, School of Medicine, University of Perugia Perugia, Italy ; Section of Neurophysiology and Biophysics, Istituto Euro-Mediterraneo di Scienza e Tecnologia Palermo, Italy
| | - Thomas Klopstock
- Department of Neurology, Friedrich-Baur-Institute, Ludwig-Maximilians-University Munich, Germany ; German Network for Mitochondrial Disorders (mitoNET) Ludwigshafen, Germany ; DZNE - German Center for Neurodegenerative Diseases Munich, Germany ; German Center for Vertigo and Balance Disorders Munich, Germany
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Kumar D, Ambasta RK, Kumar P. Mutational Consequences of Aberrant Ion Channels in Neurological Disorders. J Membr Biol 2014; 247:1083-127. [DOI: 10.1007/s00232-014-9716-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Accepted: 07/25/2014] [Indexed: 12/25/2022]
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Kipfer S, Strupp M. The Clinical Spectrum of Autosomal-Dominant Episodic Ataxias. Mov Disord Clin Pract 2014; 1:285-290. [PMID: 30713867 DOI: 10.1002/mdc3.12075] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2014] [Revised: 06/16/2014] [Accepted: 06/20/2014] [Indexed: 11/06/2022] Open
Abstract
Autosomal-dominant episodic ataxias (EAs) represent a clinically and genetically heterogeneous group of disorders characterized by recurrent episodes of cerebellar ataxia (CA). Ataxia episodes are usually of short duration and often triggered by specific stimuli. There are currently seven classified subtypes of EA. EA types 1 and 2 have the highest prevalence and are therefore the clinically most relevant. Between attacks, EA 1 is associated with myokymia. In EA 2, often an interictal downbeat nystagmus with other cerebellar ocular dysfunctions is present; patients with EA 2 may display slowly progessive ataxia and vermian atrophy. EA 1 and 2 are both channelopathies, affecting the potassium channel gene, KCNA1, in EA 1 and the PQ calcium channel-encoding gene, CACNA1A, in EA 2. The types EA 3 to 7 are very rare and have to be further elucidated. Here, we review the historical, clinical, and genetic aspects of autosomal-dominant EAs and their current treatment, focusing on EA 1 and 2.
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Affiliation(s)
- Stefan Kipfer
- Department of Neurology Kantonsspital Olten Switzerland
| | - Michael Strupp
- Department of Neurology and German Center for Vertigo and Balance Disorders University Hospital Munich Munich Germany
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Graves TD, Cha YH, Hahn AF, Barohn R, Salajegheh MK, Griggs RC, Bundy BN, Jen JC, Baloh RW, Hanna MG. Episodic ataxia type 1: clinical characterization, quality of life and genotype-phenotype correlation. ACTA ACUST UNITED AC 2014; 137:1009-18. [PMID: 24578548 DOI: 10.1093/brain/awu012] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Episodic ataxia type 1 is considered a rare neuronal ion channel disorder characterized by brief attacks of unsteadiness and dizziness with persistent myokymia. To characterize the natural history, develop outcome measures for future clinical trials, and correlate genotype with phenotype, we undertook an international, prospective, cross-sectional study. Thirty-nine individuals (51% male) were enrolled: median age 37 years (range 15-65 years). We identified 10 different pathogenic point mutations in KCNA1 that accounted for the genetic basis of 85% of the cohort. Participants with KCNA1 mutations were more likely to have a positive family history. Analysis of the total cohort showed that the first episode of ataxia occurred before age 20 in all but one patient, with an average age of onset of 7.9 years. Physical exertion, emotional stress and environmental temperature were the most common triggers for attacks. Attack frequency ranged from daily to monthly, even with the same KCNA1 genotype. Average attack duration was in the order of minutes. Ten participants (26%) developed permanent cerebellar signs, which were related to disease duration. The average Scale for the Assessment and Rating of Ataxia score (SARA, a standardized measure of cerebellar dysfunction on clinical examination, scores range from 0-40) was an average of 3.15 for all participants (range 0-14), but was only 2 in those with isolated episodic ataxia compared with 7.7 in those with progressive cerebellar ataxia in addition to episodic ataxia. Thirty-seven participants completed the SF-36, a quality of life survey; all eight domain norm-based average scores (mean=50) were below normal with mental health being the lowest (41.3) in those with mutation positive episodic ataxia type 1. Scores on SF-36 correlated negatively with attack frequency. Of the 39 participants in the study, 33 harboured mutations in KCNA1 whereas the remaining six had no mutation identified. Episodic ataxia type 1 phenocopies have not been described previously and we report their clinical features, which appear to be different to those with a KCNA1 mutation. This large prospective study of both genetically confirmed episodic ataxia type 1 and episodic ataxia type 1 phenocopies provides detailed baseline characteristics of these disorders and their impact on participants. We found that attacks had a significant effect on quality of life. Unlike previous studies, we found that a significant number of individuals with genetically confirmed episodic ataxia type 1 (21%) had accumulated persistent cerebellar symptoms and signs. These data will enable the development of outcome measures for clinical trials of treatment.
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Affiliation(s)
- Tracey D Graves
- 1 MRC Centre for Neuromuscular Disease, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
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27
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Shah NH, Aizenman E. Voltage-gated potassium channels at the crossroads of neuronal function, ischemic tolerance, and neurodegeneration. Transl Stroke Res 2013; 5:38-58. [PMID: 24323720 DOI: 10.1007/s12975-013-0297-7] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/14/2013] [Accepted: 10/14/2013] [Indexed: 11/29/2022]
Abstract
Voltage-gated potassium (Kv) channels are widely expressed in the central and peripheral nervous system and are crucial mediators of neuronal excitability. Importantly, these channels also actively participate in cellular and molecular signaling pathways that regulate the life and death of neurons. Injury-mediated increased K(+) efflux through Kv2.1 channels promotes neuronal apoptosis, contributing to widespread neuronal loss in neurodegenerative disorders such as Alzheimer's disease and stroke. In contrast, some forms of neuronal activity can dramatically alter Kv2.1 channel phosphorylation levels and influence their localization. These changes are normally accompanied by modifications in channel voltage dependence, which may be neuroprotective within the context of ischemic injury. Kv1 and Kv7 channel dysfunction leads to neuronal hyperexcitability that critically contributes to the pathophysiology of human clinical disorders such as episodic ataxia and epilepsy. This review summarizes the neurotoxic, neuroprotective, and neuroregulatory roles of Kv channels and highlights the consequences of Kv channel dysfunction on neuronal physiology. The studies described in this review thus underscore the importance of normal Kv channel function in neurons and emphasize the therapeutic potential of targeting Kv channels in the treatment of a wide range of neurological diseases.
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Affiliation(s)
- Niyathi Hegde Shah
- Department of Neurobiology, University of Pittsburgh School of Medicine, 3500 Terrace Street, E1456 BST, Pittsburgh, PA, 15261, USA,
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28
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Tan SV, Wraige E, Lascelles K, Bostock H. Episodic ataxia type 1 without episodic ataxia: the diagnostic utility of nerve excitability studies in individuals with KCNA1 mutations. Dev Med Child Neurol 2013; 55:959-62. [PMID: 23909822 DOI: 10.1111/dmcn.12236] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/17/2013] [Indexed: 11/27/2022]
Abstract
Episodic ataxia type 1 (EA1) is caused by mutations in the KCNA1 gene encoding the fast potassium channel Kv1.1 and is characterized clinically by brief episodes of ataxia and continuous and spontaneous motor unit activity. Atypical presentations, in which the predominant manifestation is related to the peripheral nervous system, may lead to the diagnosis being missed or delayed, with the potential risk of individuals receiving inappropriate or unnecessary investigations and treatment. We present a case of a 15-year-old female with EA1 who had never had episodes of ataxia, and whose hand movements were initially thought to represent a tremor. Genetic screening for KCNA1 mutations was precipitated by the results of the nerve excitability studies (TROND protocol), which showed changes typical of reduced fast potassium channel conductance. This case highlights the utility of nerve excitability studies in identifying individuals with KCNA1 mutations.
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Affiliation(s)
- S Veronica Tan
- Department of Neurology and Neurophysiology, St Thomas' Hospital, Guy's and St Thomas' NHS Foundation Trust, King's Health Partners Academic Health Science Centre, London, UK; Institute of Neurology, University College London, Queen Square, London, UK
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29
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Zhu J, Alsaber R, Zhao J, Ribeiro-Hurley E, Thornhill WB. Characterization of the Kv1.1 I262T and S342I mutations associated with episodic ataxia 1 with distinct phenotypes. Arch Biochem Biophys 2012; 524:99-105. [PMID: 22609616 DOI: 10.1016/j.abb.2012.05.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 05/08/2012] [Accepted: 05/10/2012] [Indexed: 10/28/2022]
Abstract
Episodic ataxia type 1 (EA-1) is an autosomal dominant neurological disorder caused by mutations in the potassium channel Kv1.1. Two EA-1 mutations, I262T and S342I, have been identified with unique clinical phenotypes, but their functional and biochemical properties have not been fully investigated. Here we characterized these two mutations in transfected mammalian cells both electrophysiologically and biochemically. We found that the I262T mutation resulted in a ∼7-fold reduction in the K+ current amplitude compared with wild type channels, whereas the S342I mutation produced an apparent nonfunctional channel when expressed alone. Co-expression of wild type and mutant channels showed that both I262T and S342I exerted dominant-negative effects on wild type function. The protein expression analysis showed that I262T resulted in ∼2-fold decrease in surface protein levels of Kv1.1, which partially contributed to the decreased surface conductance density, whereas the S342I mutation showed no effects on surface protein expression. Conservative amino acid substitution experiments suggest that the wild type amino acids at these two positions are required for normal channel function. Our results broaden the knowledge of EA-1 mutations and the underlying mechanisms of the associated disorder.
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Affiliation(s)
- Jing Zhu
- Department of Biological Sciences and Center for Cancer, Genetic Diseases, and Gene Regulation, Fordham University, Bronx, NY 10458, USA
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30
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Abstract
The spinocerebellar ataxias (SCAs) are a group of neurodegenerative diseases characterised by progressive lack of motor coordination leading to major disability. SCAs show high clinical, genetic, molecular and epidemiological variability. In the last one decade, the intensive scientific research devoted to the SCAs is resulting in clear advances and a better understanding on the genetic and nongenetic factors contributing to their pathogenesis which are facilitating the diagnosis, prognosis and development of new therapies. The scope of this chapter is to provide an updated information on Machado-Joseph disease (MJD), the most frequent SCA subtype worldwide and other rare spinocerebellar ataxias including dentatorubral-pallidoluysian atrophy (DRPLA), the X-linked fragile X tremor and ataxia syndrome (FXTAS) and the nonprogressive episodic forms of inherited ataxias (EAs). Furthermore, the different therapeutic strategies that are currently being investigated to treat the ataxia and non-ataxia symptoms in SCAs are also described.
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Abstract
The episodic ataxias are autosomal dominant disorders usually beginning in the first two decades of life. Episodic ataxia type 1 (EA1) is characterized by brief episodes of ataxia, typically lasting seconds, and interictal myokymia, while episodic ataxia type 2 (EA2) is manifested by longer episodes of ataxia (hours) with interictal nystagmus. The EA1 gene (KCNA1) codes for the six transmembrane segments (S1 to S6) of the Kv1.1 potassium channel subunit and the EA2 gene (CACNA1A) encodes for the Ca(v)2.1 subunit of the P/Q calcium channel complex. EA1 mutations are always missense while most EA2 mutations disrupt the reading frame. Studies of the biophysical properties of the mutant Kv1.1 and Ca(v)2.1 channels in Xenopus oocytes and mammalian cell lines demonstrate clear physiologic consequences of the genetic mutations although no consistent pattern for genotype-phenotype correlation has emerged. Genetic testing for EA1 and EA2 is available, but since no single mutation is prominent for either KCNA1 or CACNA1A, all of the coding regions of the genes need to be screened for mutations. Acetazolamide can be dramatic in controlling episodes of ataxia with EA2 but is typically less beneficial with EA1.
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Affiliation(s)
- Robert W Baloh
- Department of Neurology, University of California, Los Angeles, CA 90095-1769, USA.
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Ishida S, Sakamoto Y, Nishio T, Baulac S, Kuwamura M, Ohno Y, Takizawa A, Kaneko S, Serikawa T, Mashimo T. Kcna1-mutant rats dominantly display myokymia, neuromyotonia and spontaneous epileptic seizures. Brain Res 2011; 1435:154-66. [PMID: 22206926 DOI: 10.1016/j.brainres.2011.11.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 11/04/2011] [Accepted: 11/08/2011] [Indexed: 11/30/2022]
Abstract
Mutations in the KCNA1 gene, which encodes for the α subunit of the voltage-gated potassium channel Kv1.1, cause episodic ataxia type 1 (EA1). EA1 is a dominant human neurological disorder characterized by variable phenotypes of brief episodes of ataxia, myokymia, neuromyotonia, and associated epilepsy. Animal models for EA1 include Kcna1-deficient mice, which recessively display severe seizures and die prematurely, and V408A-knock-in mice, which dominantly exhibit stress-induced loss of motor coordination. In the present study, we have identified an N-ethyl-N-nitrosourea-mutagenized rat, named autosomal dominant myokymia and seizures (ADMS), with a missense mutation (S309T) in the voltage-sensor domain, S4, of the Kcna1 gene. ADMS rats dominantly exhibited myokymia, neuromyotonia and generalized tonic-clonic seizures. They also showed cold stress-induced tremor, neuromyotonia, and motor incoordination. Expression studies of homomeric and heteromeric Kv1.1 channels in HEK cells and Xenopus oocytes, showed that, although S309T channels are transferred to the cell membrane surface, they remained non-functional in terms of their biophysical properties, suggesting a dominant-negative effect of the S309T mutation on potassium channel function. ADMS rats provide a new model, distinct from previously reported mouse models, for studying the diverse functions of Kv1.1 in vivo, as well as for understanding the pathology of EA1.
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Affiliation(s)
- Saeko Ishida
- Institute of Laboratory animals, Graduate School of Medicine, Kyoto University, Kyoto 606-8501, Japan
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34
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Abstract
Paroxysmal movement disorders are a relatively rare and heterogenous group of conditions manifesting as episodic dyskinesia lasting a brief duration. Three forms are clearly recognized, namely, paroxysmal kinesigenic (PKD), nonkinisegenic (PNKD), and exercise induced (PED). There have been major advances in the understanding of the pathophysiological mechanisms and the genetics of these disorders, leading to better clinical definitions based on genotype-phenotype correlations in the familial idiopathic forms. PKD is genetically heterogenous, but there is linkage to chromosome 16 in a number of families. PNKD is due to mutations of the MR-1 gene. PED is genetically heterogenous, but a number of familial and sporadic cases may be due to GLUT-1 gene mutations. The GLUT1 gene-related form of PED may respond to a ketogenic diet. Potassium and calcium channel mutations underlie the 2 main forms of episodic ataxia (EA1 and EA2), whereas benign torticollis of infancy may also be a calcium channel disorder.
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Affiliation(s)
- Kailash P Bhatia
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, Queen Square, London, United Kingdom.
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35
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Abstract
The spinocerebellar ataxias (SCA) are a large group of inherited disorders affecting the cerebellum and its afferent and efferent pathways. Their hallmark symptom is slowly progressive, symmetrical, midline, and appendicular ataxia. Some may also have associated hyperkinetic movements (chorea, dystonia, myoclonus, postural/action tremor, restless legs, rubral tremor, tics), which may aid in differential diagnosis and provide treatable targets to improve performance and quality of life in these progressive, incurable conditions. The typical dominant ataxias with associated hyperkinetic movements are SCA1-3, 6-8, 12, 14, 15, 17, 19-21, and 27. The common recessive ataxias with associated hyperkinetic movements are ataxia telangiectasia and Friedreich's ataxia. Fragile X tremor-ataxia syndrome (FXTAS) and multiple-system atrophy (a sporadic ataxia which is felt to have a genetic substrate) also have hyperkinetic features. A careful work-up should be done in all apparently sporadic cases, to rule out acquired causes of ataxia, some of which can cause hyperkinetic movements in addition to ataxia. Some testing should be done even in individuals with a confirmed genetic cause, as the presence of a secondary factor (nutritional deficiency, thyroid dysfunction) can contribute to the phenotype.
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Affiliation(s)
- Susan L Perlman
- David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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36
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Tomlinson SE, Tan SV, Kullmann DM, Griggs RC, Burke D, Hanna MG, Bostock H. Nerve excitability studies characterize Kv1.1 fast potassium channel dysfunction in patients with episodic ataxia type 1. ACTA ACUST UNITED AC 2010; 133:3530-40. [PMID: 21106501 DOI: 10.1093/brain/awq318] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Episodic ataxia type 1 is a neuronal channelopathy caused by mutations in the KCNA1 gene encoding the fast K(+) channel subunit K(v)1.1. Episodic ataxia type 1 presents with brief episodes of cerebellar dysfunction and persistent neuromyotonia and is associated with an increased incidence of epilepsy. In myelinated peripheral nerve, K(v)1.1 is highly expressed in the juxtaparanodal axon, where potassium channels limit the depolarizing afterpotential and the effects of depolarizing currents. Axonal excitability studies were performed on patients with genetically confirmed episodic ataxia type 1 to characterize the effects of K(v)1.1 dysfunction on motor axons in vivo. The median nerve was stimulated at the wrist and compound muscle action potentials were recorded from abductor pollicis brevis. Threshold tracking techniques were used to record strength-duration time constant, threshold electrotonus, current/threshold relationship and the recovery cycle. Recordings from 20 patients from eight kindreds with different KCNA1 point mutations were compared with those from 30 normal controls. All 20 patients had a history of episodic ataxia and 19 had neuromyotonia. All patients had similar, distinctive abnormalities: superexcitability was on average 100% higher in the patients than in controls (P < 0.00001) and, in threshold electrotonus, the increase in excitability due to a depolarizing current (20% of threshold) was 31% higher (P < 0.00001). Using these two parameters, the patients with episodic ataxia type 1 and controls could be clearly separated into two non-overlapping groups. Differences between the different KCNA1 mutations were not statistically significant. Studies of nerve excitability can identify K(v)1.1 dysfunction in patients with episodic ataxia type 1. The simple 15 min test may be useful in diagnosis, since it can differentiate patients with episodic ataxia type 1 from normal controls with high sensitivity and specificity.
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Affiliation(s)
- Susan E Tomlinson
- Institute of Neurology, University College London, London WC1N 3BG, UK
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van der Wijst J, Glaudemans B, Venselaar H, Nair AV, Forst AL, Hoenderop JGJ, Bindels RJM. Functional analysis of the Kv1.1 N255D mutation associated with autosomal dominant hypomagnesemia. J Biol Chem 2009; 285:171-8. [PMID: 19903818 DOI: 10.1074/jbc.m109.041517] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in the voltage-gated K(+) channel Kv1.1 have been linked with a mixed phenotype of episodic ataxia and/or myokymia. Recently, we presented autosomal dominant hypomagnesemia as a new phenotypic characteristic associated with a mutation in Kv1.1 (N255D) (Glaudemans, B., van der Wijst, J., Scola, R. H., Lorenzoni, P. J., Heister, A., van der Kemp, A. W., Knoers, N. V., Hoenderop, J. G., and Bindels, R. J. (2009) J. Clin. Invest. 119, 936-942). A conserved asparagine at position 255 in the third transmembrane segment was converted into an aspartic acid, resulting in a non-functional channel. In this study, we explored the functional consequence of this conserved residue by substitution with other hydrophobic, polar, or charged amino acids (N255E, N255Q, N255A, N255V, N255T, and N255H). Upon overexpression in human embryonic kidney (HEK293) cells, cell surface biotinylation revealed plasma membrane expression of all mutant channels. Next, we used the whole-cell patch clamp technique to demonstrate that the N255E and N255Q mutants were non-functional. Substitution of Asn-255 with other amino acids (N255A, N255V, N255T, and N255H) did not prevent ion conduction, and these mutant channels activated at more negative potentials when compared with wild-type channels, -41.5 +/- 1.6, -45.5 +/- 2.0, -50.5 +/- 1.9, and -33.8 +/- 1.3 mV to -29.4 +/- 1.1 mV, respectively. The time constant of activation was significantly faster for the two most hydrophobic mutations, N255A (6.2 +/- 0.2 ms) and N255V (5.2 +/- 0.3 ms), and the hydrophilic mutant N255T (9.8 +/- 0.4 ms) in comparison with wild type (13.0 +/- 0.9 ms). Furthermore, the voltage dependence of inactivation was shifted approximately 13 mV to more negative potentials in all mutant channels except for N255H. Taken together, our data showed that an asparagine at position 255 in Kv1.1 is required for normal voltage dependence and kinetics of channel gating.
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Affiliation(s)
- Jenny van der Wijst
- Department of Physiology, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen, The Netherlands
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Tomlinson SE, Hanna MG, Kullmann DM, Tan SV, Burke D. Clinical neurophysiology of the episodic ataxias: insights into ion channel dysfunction in vivo. Clin Neurophysiol 2009; 120:1768-76. [PMID: 19734086 DOI: 10.1016/j.clinph.2009.07.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 07/03/2009] [Accepted: 07/03/2009] [Indexed: 01/02/2023]
Abstract
Clinical neurophysiology has become an invaluable tool in the diagnosis of muscle channelopathies, but the situation is less clear cut with neuronal channelopathies. The genetic episodic ataxias are a group of disorders with heterogeneous phenotype and genotype, but share in common the feature of intermittent cerebellar dysfunction. Episodic ataxia (EA) types 1 and 2 are the most widely recognised of the autosomal dominant episodic ataxias and are caused by dysfunction of neuronal voltage-gated ion channels. There are central and peripheral nervous system manifestations in both conditions, and they are therefore good models of neuronal channelopathies to study neurophysiologically. To date most work has focussed upon characterising the electrophysiological properties of mutant channels in vitro. This review summarises the role of voltage-gated potassium and calcium channels, mutations of which underlie the main types of episodic ataxia types 1 and 2. The clinical, genetic and electrophysiological features of EA1 and EA2 are outlined, and a protocol for the assessment of these patients is proposed.
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Affiliation(s)
- Susan E Tomlinson
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and University of Sydney, Sydney, Australia.
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39
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Demos MK, Macri V, Farrell K, Nelson TN, Chapman K, Accili E, Armstrong L. A novel KCNA1 mutation associated with global delay and persistent cerebellar dysfunction. Mov Disord 2009; 24:778-82. [PMID: 19205071 DOI: 10.1002/mds.22467] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Episodic Ataxia Type 1 is an autosomal dominant disorder characterized by episodes of ataxia and myokymia. It is associated with mutations in the KCNA1 voltage-gated potassium channel gene. In the present study, we describe a family with novel clinical features including persistent cerebellar dysfunction, cerebellar atrophy, and cognitive delay. All affected family members have myokymia and epilepsy, but only one individual has episodes of vertigo. Additional features include postural abnormalities, episodic stiffness and weakness. A novel KCNA1 mutation (c.1222G>T) which replaces a highly conserved valine with leucine at position 408 (p.Val408Leu) was identified in affected family members, and was found to augment the ability of the channel to inactivate. Together, our data suggests that KCNA1 mutations are associated with a broader clinical phenotype, which may include persistent cerebellar dysfunction and cognitive delay.
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Affiliation(s)
- Michelle K Demos
- Department of Pediatric Neurology, British Columbia's Children's Hospital, Vancouver, British Columbia, Canada.
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40
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Barnwell LFS, Lugo JN, Lee WL, Willis SE, Gertz SJ, Hrachovy RA, Anderson AE. Kv4.2 knockout mice demonstrate increased susceptibility to convulsant stimulation. Epilepsia 2009; 50:1741-51. [PMID: 19453702 DOI: 10.1111/j.1528-1167.2009.02086.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE Kv4.2 subunits contribute to the pore-forming region of channels that express a transient, A-type K(+) current (A-current) in hippocampal CA1 pyramidal cell dendrites. Here, the A-current plays an important role in signal processing and synaptic integration. Kv4.2 knockout mice show a near elimination of the A-current in area CA1 dendrites, producing increased excitability in this region. In these studies, we evaluated young adult Kv4.2 knockout mice for spontaneous seizures and the response to convulsant stimulation in the whole animal in vivo and in hippocampal slices in vitro. METHODS Electroencephalogram electrode-implanted Kv4.2 knockout and wild-type mice were observed for spontaneous behavioral and electrographic seizures. The latency to seizure and status epilepticus onset in Kv4.2 knockout and wild-type mice was assessed following intraperitoneal injection of kainate. Extracellular field potential recordings were performed in hippocampal slices from Kv4.2 knockout and wild-type mice following the bath application of bicuculline. RESULTS No spontaneous behavioral or electrographic seizures were observed in Kv4.2 knockout mice. Following kainate, Kv4.2 knockout mice demonstrated a decreased seizure and status epilepticus latency as well as increased mortality compared to wild-type littermates. The background strain modified the seizure susceptibility phenotype in Kv4.2 knockout mice. In response to bicuculline, slices from Kv4.2 knockout mice exhibited an increase in epileptiform bursting in area CA1 as compared to wild-type littermates. DISCUSSION These studies show that loss of Kv4.2 channels is associated with enhanced susceptibility to convulsant stimulation, supporting the concept that Kv4.2 deficiency may contribute to aberrant network excitability and regulate seizure threshold.
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Glaudemans B, van der Wijst J, Scola RH, Lorenzoni PJ, Heister A, van der Kemp AW, Knoers NV, Hoenderop JG, Bindels RJ. A missense mutation in the Kv1.1 voltage-gated potassium channel-encoding gene KCNA1 is linked to human autosomal dominant hypomagnesemia. J Clin Invest 2009; 119:936-42. [PMID: 19307729 DOI: 10.1172/jci36948] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 01/07/2009] [Indexed: 02/04/2023] Open
Abstract
Primary hypomagnesemia is a heterogeneous group of disorders characterized by renal or intestinal magnesium (Mg2+) wasting, resulting in tetany, cardiac arrhythmias, and seizures. The kidney plays an essential role in maintaining blood Mg2+ levels, with a prominent function for the Mg2+-transporting channel transient receptor potential cation channel, subfamily M, member 6 (TRPM6) in the distal convoluted tubule (DCT). In the DCT, Mg2+ reabsorption is an active transport process primarily driven by the negative potential across the luminal membrane. Here, we studied a family with isolated autosomal dominant hypomagnesemia and used a positional cloning approach to identify an N255D mutation in KCNA1, a gene encoding the voltage-gated potassium (K+) channel Kv1.1. Kv1.1 was found to be expressed in the kidney, where it colocalized with TRPM6 along the luminal membrane of the DCT. Upon overexpression in a human kidney cell line, patch clamp analysis revealed that the KCNA1 N255D mutation resulted in a nonfunctional channel, with a dominant negative effect on wild-type Kv1.1 channel function. These data suggest that Kv1.1 is a renal K+ channel that establishes a favorable luminal membrane potential in DCT cells to control TRPM6-mediated Mg2+ reabsorption.
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Affiliation(s)
- Bob Glaudemans
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Imbrici P, Gualandi F, D'Adamo MC, Masieri MT, Cudia P, De Grandis D, Mannucci R, Nicoletti I, Tucker SJ, Ferlini A, Pessia M. A novel KCNA1 mutation identified in an Italian family affected by episodic ataxia type 1. Neuroscience 2008; 157:577-87. [PMID: 18926884 DOI: 10.1016/j.neuroscience.2008.09.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Revised: 09/11/2008] [Accepted: 09/11/2008] [Indexed: 10/21/2022]
Abstract
Episodic ataxia type 1 (EA1) is a rare human neurological syndrome characterized by continuous myokymia and attacks of generalized ataxia that can be triggered by abrupt movements, emotional stress and fatigue. An Italian family has been identified where related members displayed continuous myokymia, episodes of ataxia, attacks characterized by myokymia only, and neuromyotonia. A novel missense mutation (F414C), in the C-terminal region of the K(+) channel Kv1.1, was identified in the affected individuals. The mutant homotetrameric channels were non-functional in Xenopus laevis oocytes. In addition, heteromeric channels resulting from the co-expression of wild-type Kv1.1 and Kv1.1(F414C), or wild-type Kv1.2 and Kv1.1(F414C) subunits displayed reduced current amplitudes and altered gating properties. This indicates that the pathogenic effect of this KCNA1 mutation is likely to be related to the defective functional properties we have identified.
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Affiliation(s)
- P Imbrici
- Section of Human Physiology, Department of Internal Medicine, University of Perugia School of Medicine, Via del Giochetto, I-06126 Perugia, Italy
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Abstract
Episodic ataxia type 1 is a paroxysmal neurological disorder characterized by short-lived attacks of recurrent midline cerebellar dysfunction and continuous motor activity. Mutations in KCN1A, the gene encoding Kv1.1, a voltage-gated neuronal potassium channel, are associated with the disorder. Although rare, the syndrome highlights the fundamental features of genetic ion-channel diseases and serves as a useful model for understanding more common paroxysmal disorders, such as epilepsy and migraine. This review examines our current understanding of episodic ataxia type 1, focusing on its clinical and genetic features, pathophysiology, and treatment.
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Affiliation(s)
- Sanjeev Rajakulendran
- Department of Molecular Neuroscience, Centre for Neuromuscular Disease, Queen Square, London WC1N 3BG, United Kingdom
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Chen H, von Hehn C, Kaczmarek LK, Ment LR, Pober BR, Hisama FM. Functional analysis of a novel potassium channel (KCNA1) mutation in hereditary myokymia. Neurogenetics 2006; 8:131-5. [PMID: 17136396 PMCID: PMC1820748 DOI: 10.1007/s10048-006-0071-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2006] [Accepted: 10/27/2006] [Indexed: 10/25/2022]
Abstract
Myokymia is characterized by spontaneous, involuntary muscle fiber group contraction visible as vermiform movement of the overlying skin. Myokymia with episodic ataxia is a rare, autosomal dominant trait caused by mutations in KCNA1, encoding a voltage-gated potassium channel. In the present study, we report a family with four members affected with myokymia. Additional clinical features included motor delay initially diagnosed as cerebral palsy, worsening with febrile illness, persistent extensor plantar reflex, and absence of epilepsy or episodic ataxia. Mutation analysis revealed a novel c.676C>A substitution in the potassium channel gene KCNA1, resulting in a T226K nonconservative missense mutation in the Kv1.1 subunit in all affected individuals. Electrophysiological studies of the mutant channel expressed in Xenopus oocytes indicated a loss of function. Co-expression of WT and mutant cRNAs significantly reduced whole-oocyte current compared to expression of WT Kv1.1 alone.
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Affiliation(s)
- Haijun Chen
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT USA
| | - Christian von Hehn
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT USA
| | - Leonard K. Kaczmarek
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT USA
| | - Laura R. Ment
- Department of Pediatrics, Yale University School of Medicine, New Haven, CT USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT USA
| | | | - Fuki M. Hisama
- Division of Genetics, Harvard Medical School, Boston, MA USA
- Division of Genetics, Children’s Hospital Boston, 300 Longwood Avenue Fegan 10, Boston, MA 02115 USA
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