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Abbott PW, Hardie JB, Walsh KP, Nessler AJ, Farley SJ, Freeman JH, Wemmie JA, Wendt L, Kim YC, Sowers LP, Parker KL. Knockdown of the Non-canonical Wnt Gene Prickle2 Leads to Cerebellar Purkinje Cell Abnormalities While Cerebellar-Mediated Behaviors Remain Intact. CEREBELLUM (LONDON, ENGLAND) 2024:10.1007/s12311-023-01648-9. [PMID: 38165577 PMCID: PMC11217148 DOI: 10.1007/s12311-023-01648-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/08/2023] [Indexed: 01/04/2024]
Abstract
Autism spectrum disorders (ASD) involve brain wide abnormalities that contribute to a constellation of symptoms including behavioral inflexibility, cognitive dysfunction, learning impairments, altered social interactions, and perceptive time difficulties. Although a single genetic variation does not cause ASD, genetic variations such as one involving a non-canonical Wnt signaling gene, Prickle2, has been found in individuals with ASD. Previous work looking into phenotypes of Prickle2 knock-out (Prickle2-/-) and heterozygous mice (Prickle2-/+) suggest patterns of behavior similar to individuals with ASD including altered social interaction and behavioral inflexibility. Growing evidence implicates the cerebellum in ASD. As Prickle2 is expressed in the cerebellum, this animal model presents a unique opportunity to investigate the cerebellar contribution to autism-like phenotypes. Here, we explore cerebellar structural and physiological abnormalities in animals with Prickle2 knockdown using immunohistochemistry, whole-cell patch clamp electrophysiology, and several cerebellar-associated motor and timing tasks, including interval timing and eyeblink conditioning. Histologically, Prickle2-/- mice have significantly more empty spaces or gaps between Purkinje cells in the posterior lobules and a decreased propensity for Purkinje cells to fire action potentials. These structural cerebellar abnormalities did not impair cerebellar-associated behaviors as eyeblink conditioning and interval timing remained intact. Therefore, although Prickle-/- mice show classic phenotypes of ASD, they do not recapitulate the involvement of the adult cerebellum and may not represent the pathophysiological heterogeneity of the disorder.
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Affiliation(s)
- Parker W Abbott
- Department of Psychiatry, Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52242, USA
- Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52245, USA
| | - Jason B Hardie
- Department of Psychiatry, Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52242, USA
- Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52245, USA
| | - Kyle P Walsh
- Department of Psychiatry, Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52242, USA
- Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52245, USA
| | - Aaron J Nessler
- Department of Biochemistry, The University of Iowa, Iowa City, IA, 52245, USA
| | | | - John H Freeman
- Department of Psychiatry, Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52242, USA
- Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52245, USA
| | - John A Wemmie
- Department of Psychiatry, Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52242, USA
- Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52245, USA
| | - Linder Wendt
- Department of Biostatistics, The University of Iowa, Iowa City, IA, 52245, USA
| | - Young-Cho Kim
- Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52245, USA
- Department of Neurology, The University of Iowa, Iowa City, IA, 52245, USA
| | - Levi P Sowers
- Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52245, USA
- Department of Pediatrics, The University of Iowa, Iowa City, IA, 52245, USA
| | - Krystal L Parker
- Department of Psychiatry, Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52242, USA.
- Iowa Neuroscience Institute, The University of Iowa, Iowa City, IA, 52245, USA.
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Kapfhammer JP, Shimobayashi E. Viewpoint: spinocerebellar ataxias as diseases of Purkinje cell dysfunction rather than Purkinje cell loss. Front Mol Neurosci 2023; 16:1182431. [PMID: 37426070 PMCID: PMC10323145 DOI: 10.3389/fnmol.2023.1182431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 05/22/2023] [Indexed: 07/11/2023] Open
Abstract
Spinocerebellar ataxias (SCAs) are a group of hereditary neurodegenerative diseases mostly affecting cerebellar Purkinje cells caused by a wide variety of different mutations. One subtype, SCA14, is caused by mutations of Protein Kinase C gamma (PKCγ), the dominant PKC isoform present in Purkinje cells. Mutations in the pathway in which PKCγ is active, i.e., in the regulation of calcium levels and calcium signaling in Purkinje cells, are the cause of several other variants of SCA. In SCA14, many of the observed mutations in the PKCγ gene were shown to increase the basal activity of PKCγ, raising the possibility that increased activity of PKCγ might be the cause of most forms of SCA14 and might also be involved in the pathogenesis of SCA in related subtypes. In this viewpoint and review article we will discuss the evidence for and against such a major role of PKCγ basal activity and will suggest a hypothesis of how PKCγ activity and the calcium signaling pathway may be involved in the pathogenesis of SCAs despite the different and sometimes opposing effects of mutations affecting these pathways. We will then widen the scope and propose a concept of SCA pathogenesis which is not primarily driven by cell death and loss of Purkinje cells but rather by dysfunction of Purkinje cells which are still present and alive in the cerebellum.
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Huang H, Shakkottai VG. Targeting Ion Channels and Purkinje Neuron Intrinsic Membrane Excitability as a Therapeutic Strategy for Cerebellar Ataxia. Life (Basel) 2023; 13:1350. [PMID: 37374132 DOI: 10.3390/life13061350] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 06/03/2023] [Accepted: 06/06/2023] [Indexed: 06/29/2023] Open
Abstract
In degenerative neurological disorders such as Parkinson's disease, a convergence of widely varying insults results in a loss of dopaminergic neurons and, thus, the motor symptoms of the disease. Dopamine replacement therapy with agents such as levodopa is a mainstay of therapy. Cerebellar ataxias, a heterogeneous group of currently untreatable conditions, have not been identified to have a shared physiology that is a target of therapy. In this review, we propose that perturbations in cerebellar Purkinje neuron intrinsic membrane excitability, a result of ion channel dysregulation, is a common pathophysiologic mechanism that drives motor impairment and vulnerability to degeneration in cerebellar ataxias of widely differing genetic etiologies. We further propose that treatments aimed at restoring Purkinje neuron intrinsic membrane excitability have the potential to be a shared therapy in cerebellar ataxia akin to levodopa for Parkinson's disease.
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Affiliation(s)
- Haoran Huang
- Medical Scientist Training Program, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Vikram G Shakkottai
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Srinivasan SR. Targeting Circuit Abnormalities in Neurodegenerative Disease. Mol Pharmacol 2023; 103:38-44. [PMID: 36310030 DOI: 10.1124/molpharm.122.000563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 10/18/2022] [Accepted: 10/24/2022] [Indexed: 02/03/2023] Open
Abstract
Despite significant improvement in our ability to diagnose both common and rare neurodegenerative diseases and understand their underlying biologic mechanisms, there remains a disproportionate lack of effective treatments, reflecting the complexity of these disorders. Successfully advancing novel treatments for neurodegenerative disorders will require reconsideration of traditional approaches, which to date have focused largely on specific disease proteins or cells of origin. This article proposes reframing these diseases as conditions of dysfunctional circuitry as a complement to ongoing efforts. Specifically reviewed is how aberrant spiking is a common downstream mechanism in numerous neurodegenerative diseases, often driven by dysfunction in specific ion channels. Surgical modification of this electrical activity via deep brain stimulation is already an approved modality for many of these disorders. Therefore, restoring proper electrical activity by targeting these channels pharmacologically represents a viable strategy for intervention, not only for symptomatic management but also as a potential disease-modifying therapy. Such an approach is likely to be a promising route to treating these devastating disorders, either as monotherapy or in conjunction with current drugs. SIGNIFICANCE STATEMENT: Despite extensive research and improved understanding of the biology driving neurodegenerative disease, there has not been a concomitant increase in approved therapies. Accordingly, it is time to shift our perspective and recognize these diseases also as disorders of circuitry to further yield novel drug targets and new interventions. An approach focused on treating dysfunctional circuitry has the potential to reduce or reverse patient symptoms and potentially modify disease course.
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Sakamoto M, Iwama K, Sasaki M, Ishiyama A, Komaki H, Saito T, Takeshita E, Shimizu-Motohashi Y, Haginoya K, Kobayashi T, Goto T, Tsuyusaki Y, Iai M, Kurosawa K, Osaka H, Tohyama J, Kobayashi Y, Okamoto N, Suzuki Y, Kumada S, Inoue K, Mashimo H, Arisaka A, Kuki I, Saijo H, Yokochi K, Kato M, Inaba Y, Gomi Y, Saitoh S, Shirai K, Morimoto M, Izumi Y, Watanabe Y, Nagamitsu SI, Sakai Y, Fukumura S, Muramatsu K, Ogata T, Yamada K, Ishigaki K, Hirasawa K, Shimoda K, Akasaka M, Kohashi K, Sakakibara T, Ikuno M, Sugino N, Yonekawa T, Gürsoy S, Cinleti T, Kim CA, Teik KW, Yan CM, Haniffa M, Ohba C, Ito S, Saitsu H, Saida K, Tsuchida N, Uchiyama Y, Koshimizu E, Fujita A, Hamanaka K, Misawa K, Miyatake S, Mizuguchi T, Miyake N, Matsumoto N. Genetic and clinical landscape of childhood cerebellar hypoplasia and atrophy. Genet Med 2022; 24:2453-2463. [PMID: 36305856 DOI: 10.1016/j.gim.2022.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 08/15/2022] [Accepted: 08/15/2022] [Indexed: 11/06/2022] Open
Abstract
PURPOSE Cerebellar hypoplasia and atrophy (CBHA) in children is an extremely heterogeneous group of disorders, but few comprehensive genetic studies have been reported. Comprehensive genetic analysis of CBHA patients may help differentiating atrophy and hypoplasia and potentially improve their prognostic aspects. METHODS Patients with CBHA in 176 families were genetically examined using exome sequencing. Patients with disease-causing variants were clinically evaluated. RESULTS Disease-causing variants were identified in 96 of the 176 families (54.5%). After excluding 6 families, 48 patients from 42 families were categorized as having syndromic associations with CBHA, whereas the remaining 51 patients from 48 families had isolated CBHA. In 51 patients, 26 aberrant genes were identified, of which, 20 (76.9%) caused disease in 1 family each. The most prevalent genes were CACNA1A, ITPR1, and KIF1A. Of the 26 aberrant genes, 21 and 1 were functionally annotated to atrophy and hypoplasia, respectively. CBHA+S was more clinically severe than CBHA-S. Notably, ARG1 and FOLR1 variants were identified in 2 families, leading to medical treatments. CONCLUSION A wide genetic and clinical diversity of CBHA was revealed through exome sequencing in this cohort, which highlights the importance of comprehensive genetic analyses. Furthermore, molecular-based treatment was available for 2 families.
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Affiliation(s)
- Masamune Sakamoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Pediatrics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Kazuhiro Iwama
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Pediatrics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Masayuki Sasaki
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Akihiko Ishiyama
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Hirofumi Komaki
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Takashi Saito
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Eri Takeshita
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Yuko Shimizu-Motohashi
- Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Kazuhiro Haginoya
- Department of Pediatric Neurology, Miyagi Children's Hospital, Sendai, Japan
| | - Tomoko Kobayashi
- Department of Pediatrics, Tohoku University Hospital, Tohoku University, Sendai, Japan; Tohoku Medical Megabank Organization, Tohoku University, Sendai, Japan
| | - Tomohide Goto
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Yu Tsuyusaki
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Mizue Iai
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Kenji Kurosawa
- Division of Medical Genetics, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Hitoshi Osaka
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan; Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Jun Tohyama
- Department of Child Neurology, NHO Nishiniigata Chuo Hospital, Niigata, Japan
| | - Yu Kobayashi
- Department of Child Neurology, NHO Nishiniigata Chuo Hospital, Niigata, Japan
| | - Nobuhiko Okamoto
- Department of Medical Genetics, Osaka Women's and Children's Hospital, Izumi, Japan
| | - Yume Suzuki
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Satoko Kumada
- Department of Neuropediatrics, Tokyo Metropolitan Neurological Hospital, Tokyo, Japan
| | - Kenji Inoue
- Department of Neuropediatrics, Tokyo Metropolitan Neurological Hospital, Tokyo, Japan
| | - Hideaki Mashimo
- Department of Neuropediatrics, Tokyo Metropolitan Neurological Hospital, Tokyo, Japan
| | - Atsuko Arisaka
- Department of Neuropediatrics, Tokyo Metropolitan Neurological Hospital, Tokyo, Japan
| | - Ichiro Kuki
- Department of Pediatric Neurology, Children's Medical Center, Osaka City General Hospital, Osaka, Japan
| | - Harumi Saijo
- Department of Pediatrics, Tokyo Metropolitan Higashiyamato Medical Center for Developmental/Multiple Disabilities, Tokyo, Japan
| | - Kenji Yokochi
- Department of Pediatric Neurology, Seirei-Mikatahara General Hospital, Hamamatsu, Japan
| | - Mitsuhiro Kato
- Department of Pediatrics, Showa University School of Medicine, Tokyo, Japan
| | - Yuji Inaba
- Division of Neurology, Nagano Children's Hospital, Azumino, Nagano, Japan
| | - Yuko Gomi
- Division of Rehabilitation, Nagano Children's Hospital, Azumino, Nagano, Japan
| | - Shinji Saitoh
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Kentaro Shirai
- Department of Pediatrics, Tsuchiura Kyodo General Hospital, Ibaraki, Japan
| | - Masafumi Morimoto
- Department of Pediatrics, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Yuishin Izumi
- Department of Clinical Neuroscience, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, Japan
| | - Yoriko Watanabe
- Department of Pediatrics and Child Health, Kurume University School of Medicine, Kurume, Japan
| | | | - Yasunari Sakai
- Department of Pediatrics, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Shinobu Fukumura
- Department of Pediatrics, School of Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Kazuhiro Muramatsu
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan; Department of Pediatrics, Graduate School of Medicine, Gunma University, Gunma, Japan
| | - Tomomi Ogata
- Department of Pediatrics, Graduate School of Medicine, Gunma University, Gunma, Japan
| | - Keitaro Yamada
- Department of Pediatric Neurology, Aichi Developmental Disability Center Central Hospital, Aichi, Japan
| | - Keiko Ishigaki
- Department of Pediatrics, School of Medicine, Tokyo Women's Medical University, Tokyo, Japan
| | - Kyoko Hirasawa
- Department of Pediatrics, School of Medicine, Tokyo Women's Medical University, Tokyo, Japan
| | - Konomi Shimoda
- Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Manami Akasaka
- Department of Pediatrics, School of Medicine, Iwate Medical University, Iwate, Japan
| | - Kosuke Kohashi
- Department of Pediatrics, Matsudo City General Hospital, Matsudo, Japan
| | | | - Masashi Ikuno
- Department of Neurology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Noriko Sugino
- Department of Neonatology, Mie Chuo Medical Center, National Hospital Organization, Tsu, Japan
| | - Takahiro Yonekawa
- Department of Pediatrics, Mie University School of Medicine, Mie, Japan
| | - Semra Gürsoy
- Department of Pediatric Genetics, S.B.Ü. Dr. Behçet Uz Children's Education and Research Hospital, Izmir, Turkey
| | - Tayfun Cinleti
- Department of Pediatric Genetics, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey
| | - Chong Ae Kim
- Unidade de Genética Clínica, Instituto da Criança do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
| | - Keng Wee Teik
- Department of Genetics, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia
| | - Chan Mei Yan
- Department of Genetics, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia
| | - Muzhirah Haniffa
- Department of Genetics, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia
| | - Chihiro Ohba
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Shuuichi Ito
- Department of Pediatrics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Hirotomo Saitsu
- Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Ken Saida
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Naomi Tsuchida
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Rare Disease Genomics, Yokohama City University Hospital, Yokohama, Japan
| | - Yuri Uchiyama
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Rare Disease Genomics, Yokohama City University Hospital, Yokohama, Japan
| | - Eriko Koshimizu
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Atsushi Fujita
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Kohei Hamanaka
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Kazuharu Misawa
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; RIKEN Center for Advanced Intelligence Project, Tokyo, Japan
| | - Satoko Miyatake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Clinical Genetics, Yokohama City University Hospital, Yokohama, Japan
| | - Takeshi Mizuguchi
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Human Genetics, Research Institute, National Center for Global Health and Medicine, Tokyo, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan.
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Egorova PA, Bezprozvanny IB. Electrophysiological Studies Support Utility of Positive Modulators of SK Channels for the Treatment of Spinocerebellar Ataxia Type 2. CEREBELLUM (LONDON, ENGLAND) 2022; 21:742-749. [PMID: 34978024 DOI: 10.1007/s12311-021-01349-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/18/2021] [Indexed: 06/14/2023]
Abstract
Spinocerebellar ataxia type 2 (SCA2) is an incurable hereditary disorder accompanied by cerebellar degeneration following ataxic symptoms. The causative gene for SCA2 is ATXN2. The ataxin-2 protein is involved in RNA metabolism; the polyQ expansion may interrupt ataxin-2 interaction with its molecular targets, thus representing a loss-of-function mutation. However, mutant ataxin-2 protein also displays the features of gain-of-function mutation since it forms the aggregates in SCA2 cells and also enhances the IP3-induced calcium release in affected neurons. The cerebellar Purkinje cells (PCs) are primarily affected in SCA2. Their tonic pacemaker activity is crucial for the proper cerebellar functioning. Disturbances in PC pacemaking are observed in many ataxic disorders. The abnormal intrinsic pacemaking was reported in mouse models of episodic ataxia type 2 (EA2), SCA1, SCA2, SCA3, SCA6, Huntington's disease (HD), and in some other murine models of the disorders associated with the cerebellar degeneration. In our studies using SCA2-58Q transgenic mice via cerebellar slice recording and in vivo recording from urethane-anesthetized mice and awake head-fixed mice, we have demonstrated the impaired firing frequency and irregularity of PCs in these mice. PC pacemaker activity is regulated by SK channels. The pharmacological activation of SK channels has demonstrated some promising results in the electrophysiological experiments on EA2, SCA1, SCA2, SCA3, SCA6, HD mice, and also on mutant CACNA1A mice. In our studies, we have reported that the SK activators CyPPA and NS309 converted bursting activity into tonic, while oral treatment with CyPPA and NS13001 significantly improved motor performance and PC morphology in SCA2 mice. The i.p. injections of chlorzoxazone (CHZ) during in vivo recording sessions converted bursting cells into tonic in anesthetized SCA2 mice. And, finally, long-term injections of CHZ recovered the precision of PC pacemaking activity in awake SCA2 mice and alleviated their motor decline. Thus, the SK activation can be used as a potential way to treat SCA2 and other diseases accompanied by cerebellar degeneration.
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Affiliation(s)
- Polina A Egorova
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia.
| | - Ilya B Bezprozvanny
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russia.
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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Srinivasan SR, Huang H, Chang WC, Nasburg JA, Nguyen HM, Strassmaier T, Wulff H, Shakkottai VG. Discovery of Novel Activators of Large-Conductance Calcium-Activated Potassium Channels for the Treatment of Cerebellar Ataxia. Mol Pharmacol 2022; 102:438-449. [PMID: 35489717 PMCID: PMC9341255 DOI: 10.1124/molpharm.121.000478] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 04/07/2022] [Indexed: 01/11/2023] Open
Abstract
Impaired cerebellar Purkinje neuron firing resulting from reduced expression of large-conductance calcium-activated potassium (BK) channels is a consistent feature in models of inherited neurodegenerative spinocerebellar ataxia (SCA). Restoring BK channel expression improves motor function and delays cerebellar degeneration, indicating that BK channels are an attractive therapeutic target. Current BK channel activators lack specificity and potency and are therefore poor templates for future drug development. We implemented an automated patch clamp platform for high-throughput drug discovery of BK channel activators using the Nanion SyncroPatch 384PE system. We screened over 15,000 compounds for their ability to increase BK channel current amplitude under conditions of lower intracellular calcium that is present in disease. We identified several novel BK channel activators that were then retested on the SyncroPatch 384PE to generate concentration-response curves (CRCs). Compounds with favorable CRCs were subsequently tested for their ability to improve irregular cerebellar Purkinje neuron spiking, characteristic of BK channel dysfunction in SCA1 mice. We identified a novel BK channel activator, 4-chloro-N-(5-chloro-2-cyanophenyl)-3-(trifluoromethyl)benzene-1-sulfonamide (herein renamed BK-20), that exhibited a more potent half-maximal activation of BK current (pAC50 = 4.64) than NS-1619 (pAC50 = 3.7) at a free internal calcium concentration of 270 nM in a heterologous expression system and improved spiking regularity in SCA1 Purkinje neurons. BK-20 had no activity on small-conductance calcium-activated potassium (SK)1-3 channels but interestingly was a potent blocker of the T-type calcium channel, Cav3.1 (IC50 = 1.05 μM). Our work describes both a novel compound for further drug development in disorders with irregular Purkinje spiking and a unique platform for drug discovery in degenerative ataxias. SIGNIFICANCE STATEMENT: Motor impairment associated with altered Purkinje cell spiking due to dysregulation of large-conductance calcium-activated potassium (BK) channel expression and function is a shared feature of disease in many degenerative ataxias. BK channel activators represent an outstanding therapeutic agent for ataxia. We have developed a high-throughput platform to screen for BK channel activators and identified a novel compound that can serve as a template for future drug development for the treatment of these disabling disorders.
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Affiliation(s)
- Sharan R Srinivasan
- Brigham and Women's Hospital, Department of Neurology, Boston, Massachusetts (S.R.S.); University of Texas Southwestern Medical Center, Department of Neurology, Dallas, Texas (H.H., V.G.S.); University of Michigan, Department of Neurology, Ann Arbor, Michigan (S.R.S., W.-C.C.); University of California, Davis, Department of Pharmacology, Davis, California (J.A.N., H.M.N., H.W.); and Nanion Technologies, Munich, Germany (T.S.)
| | - Haoran Huang
- Brigham and Women's Hospital, Department of Neurology, Boston, Massachusetts (S.R.S.); University of Texas Southwestern Medical Center, Department of Neurology, Dallas, Texas (H.H., V.G.S.); University of Michigan, Department of Neurology, Ann Arbor, Michigan (S.R.S., W.-C.C.); University of California, Davis, Department of Pharmacology, Davis, California (J.A.N., H.M.N., H.W.); and Nanion Technologies, Munich, Germany (T.S.)
| | - Wei-Chih Chang
- Brigham and Women's Hospital, Department of Neurology, Boston, Massachusetts (S.R.S.); University of Texas Southwestern Medical Center, Department of Neurology, Dallas, Texas (H.H., V.G.S.); University of Michigan, Department of Neurology, Ann Arbor, Michigan (S.R.S., W.-C.C.); University of California, Davis, Department of Pharmacology, Davis, California (J.A.N., H.M.N., H.W.); and Nanion Technologies, Munich, Germany (T.S.)
| | - Joshua A Nasburg
- Brigham and Women's Hospital, Department of Neurology, Boston, Massachusetts (S.R.S.); University of Texas Southwestern Medical Center, Department of Neurology, Dallas, Texas (H.H., V.G.S.); University of Michigan, Department of Neurology, Ann Arbor, Michigan (S.R.S., W.-C.C.); University of California, Davis, Department of Pharmacology, Davis, California (J.A.N., H.M.N., H.W.); and Nanion Technologies, Munich, Germany (T.S.)
| | - Hai M Nguyen
- Brigham and Women's Hospital, Department of Neurology, Boston, Massachusetts (S.R.S.); University of Texas Southwestern Medical Center, Department of Neurology, Dallas, Texas (H.H., V.G.S.); University of Michigan, Department of Neurology, Ann Arbor, Michigan (S.R.S., W.-C.C.); University of California, Davis, Department of Pharmacology, Davis, California (J.A.N., H.M.N., H.W.); and Nanion Technologies, Munich, Germany (T.S.)
| | - Tim Strassmaier
- Brigham and Women's Hospital, Department of Neurology, Boston, Massachusetts (S.R.S.); University of Texas Southwestern Medical Center, Department of Neurology, Dallas, Texas (H.H., V.G.S.); University of Michigan, Department of Neurology, Ann Arbor, Michigan (S.R.S., W.-C.C.); University of California, Davis, Department of Pharmacology, Davis, California (J.A.N., H.M.N., H.W.); and Nanion Technologies, Munich, Germany (T.S.)
| | - Heike Wulff
- Brigham and Women's Hospital, Department of Neurology, Boston, Massachusetts (S.R.S.); University of Texas Southwestern Medical Center, Department of Neurology, Dallas, Texas (H.H., V.G.S.); University of Michigan, Department of Neurology, Ann Arbor, Michigan (S.R.S., W.-C.C.); University of California, Davis, Department of Pharmacology, Davis, California (J.A.N., H.M.N., H.W.); and Nanion Technologies, Munich, Germany (T.S.)
| | - Vikram G Shakkottai
- Brigham and Women's Hospital, Department of Neurology, Boston, Massachusetts (S.R.S.); University of Texas Southwestern Medical Center, Department of Neurology, Dallas, Texas (H.H., V.G.S.); University of Michigan, Department of Neurology, Ann Arbor, Michigan (S.R.S., W.-C.C.); University of California, Davis, Department of Pharmacology, Davis, California (J.A.N., H.M.N., H.W.); and Nanion Technologies, Munich, Germany (T.S.)
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8
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Li M, Liu F, Hao X, Fan Y, Li J, Hu Z, Shi J, Fan L, Zhang S, Ma D, Guo M, Xu Y, Shi C. Rare KCND3 Loss-of-Function Mutation Associated With the SCA19/22. Front Mol Neurosci 2022; 15:919199. [PMID: 35813061 PMCID: PMC9261871 DOI: 10.3389/fnmol.2022.919199] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 05/19/2022] [Indexed: 12/15/2022] Open
Abstract
Spinocerebellar ataxia 19/22 (SCA19/22) is a rare neurodegenerative disorder caused by mutations of the KCND3 gene, which encodes the Kv4. 3 protein. Currently, only 22 KCND3 single-nucleotide mutation sites of SCA19/22 have been reported worldwide, and detailed pathogenesis remains unclear. In this study, Sanger sequencing was used to screen 115 probands of cerebellar ataxia families in 67 patients with sporadic cerebellar ataxia and 200 healthy people to identify KCND3 mutations. Mutant gene products showed pathogenicity damage, and the polarity was changed. Next, we established induced pluripotent stem cells (iPSCs) derived from SCA19/22 patients. Using a transcriptome sequencing technique, we found that protein processing in the endoplasmic reticulum was significantly enriched in SCA19/22-iPS-derived neurons and was closely related to endoplasmic reticulum stress (ERS) and apoptosis. In addition, Western blotting of the SCA19/22-iPS-derived neurons showed a reduction in Kv4.3; but, activation of transcription factor 4 (ATF4) and C/EBP homologous protein was increased. Therefore, the c.1130 C>T (p.T377M) mutation of the KCND3 gene may mediate misfold and aggregation of Kv4.3, which activates the ERS and further induces neuron apoptosis involved in SCA19/22.
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Affiliation(s)
- Mengjie Li
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
| | - Fen Liu
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Academy of Medical Sciences of Zhengzhou University, Zhengzhou, China
| | - Xiaoyan Hao
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Academy of Medical Sciences of Zhengzhou University, Zhengzhou, China
| | - Yu Fan
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Academy of Medical Sciences of Zhengzhou University, Zhengzhou, China
| | - Jiadi Li
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Academy of Medical Sciences of Zhengzhou University, Zhengzhou, China
| | - Zhengwei Hu
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Academy of Medical Sciences of Zhengzhou University, Zhengzhou, China
| | - Jingjing Shi
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Department of Cell Biology and Medical Genetics, Basic Medical College of Zhengzhou University, Zhengzhou, China
| | - Liyuan Fan
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Academy of Medical Sciences of Zhengzhou University, Zhengzhou, China
| | - Shuo Zhang
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Academy of Medical Sciences of Zhengzhou University, Zhengzhou, China
| | - Dongrui Ma
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
| | - Mengnan Guo
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
| | - Yuming Xu
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Department of Cell Biology and Medical Genetics, Basic Medical College of Zhengzhou University, Zhengzhou, China
- Henan Key Laboratory of Cerebrovascular Diseases, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Institute of Neuroscience, Zhengzhou University, Zhengzhou, China
- The Henan Medical Key Laboratory of Hereditary Neurodegenerative Diseases, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- The Key Laboratory of Cerebrovascular Diseases Prevention and Treatment, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
| | - Changhe Shi
- Department of Neurology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Henan Key Laboratory of Cerebrovascular Diseases, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- Institute of Neuroscience, Zhengzhou University, Zhengzhou, China
- The Henan Medical Key Laboratory of Hereditary Neurodegenerative Diseases, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- The Key Laboratory of Cerebrovascular Diseases Prevention and Treatment, The First Affiliated Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
- *Correspondence: Changhe Shi
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9
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Bushart DD, Shakkottai VG. Vulnerability of Human Cerebellar Neurons to Degeneration in Ataxia-Causing Channelopathies. Front Syst Neurosci 2022; 16:908569. [PMID: 35757096 PMCID: PMC9219590 DOI: 10.3389/fnsys.2022.908569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 05/20/2022] [Indexed: 01/27/2023] Open
Abstract
Mutations in ion channel genes underlie a number of human neurological diseases. Historically, human mutations in ion channel genes, the so-called channelopathies, have been identified to cause episodic disorders. In the last decade, however, mutations in ion channel genes have been demonstrated to result in progressive neurodegenerative and neurodevelopmental disorders in humans, particularly with ion channels that are enriched in the cerebellum. This was unexpected given prior rodent ion channel knock-out models that almost never display neurodegeneration. Human ataxia-causing channelopathies that result in even haploinsufficiency can result in cerebellar atrophy and cerebellar Purkinje neuron loss. Rodent neurons with ion channel loss-of-function appear to, therefore, be significantly more resistant to neurodegeneration compared to human neurons. Fundamental differences in susceptibility of human and rodent cerebellar neurons in ataxia-causing channelopathies must therefore be present. In this review, we explore the properties of human neurons that may contribute to their vulnerability to cerebellar degeneration secondary to ion channel loss-of-function mutations. We present a model taking into account the known allometric scaling of neuronal ion channel density in humans and other mammals that may explain the preferential vulnerability of human cerebellar neurons to degeneration in ataxia-causing channelopathies. We also speculate on the vulnerability of cerebellar neurons to degeneration in mouse models of spinocerebellar ataxia (SCA) where ion channel transcript dysregulation has recently been implicated in disease pathogenesis.
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Affiliation(s)
- David D. Bushart
- Ohio State University College of Medicine, Columbus, OH, United States
| | - Vikram G. Shakkottai
- Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX, United States,*Correspondence: Vikram G. Shakkottai,
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10
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Kumar G, Asthana P, Yung WH, Kwan KM, Tin C, Ma CHE. Deep Brain Stimulation of the Interposed Nucleus Reverses Motor Deficits and Stimulates Production of Anti-inflammatory Cytokines in Ataxia Mice. Mol Neurobiol 2022; 59:4578-4592. [PMID: 35581519 DOI: 10.1007/s12035-022-02872-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 05/05/2022] [Indexed: 11/24/2022]
Abstract
Cerebellum is one of the major targets of autoimmunity and cerebellar damage that leads to ataxia characterized by the loss of fine motor coordination and balance, with no treatment available. Deep brain stimulation (DBS) could be a promising treatment for ataxia but has not been extensively investigated. Here, our study aims to investigate the use of interposed nucleus of deep cerebellar nuclei (IN-DCN) for ataxia. We first characterized ataxia-related motor symptom of a Purkinje cell (PC)-specific LIM homeobox (Lhx)1 and Lhx5 conditional double knockout mice by motor coordination tests, and spontaneous electromyogram (EMG) recording. To validate IN-DCN as a target for DBS, in vivo local field potential (LFP) multielectrode array recording of IN-DCN revealed abnormal LFP amplitude surges in PCs. By synchronizing the EMG and IN-DCN recordings (neurospike and LFP) with high-speed video recordings, ataxia mice showed poorly coordinated movements associated with low EMG amplitude and aberrant IN-DCN neural firing. To optimize IN-DCN-DBS for ataxia, we tested DBS parameters from low (30 Hz) to high stimulation frequency (130 or 150 Hz), and systematically varied pulse width values (60 or 80 µs) to maximize motor symptom control in ataxia mice. The optimal IN-DCN-DBS parameter reversed motor deficits in ataxia mice as detected by animal behavioral tests and EMG recording. Mechanistically, cytokine array analysis revealed that anti-inflammatory cytokines such as interleukin (IL)-13 and IL-4 were upregulated after IN-DCN-DBS, which play key roles in neural excitability. As such, we show that IN-DCN-DBS is a promising treatment for ataxia and possibly other movement disorders alike.
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Affiliation(s)
- Gajendra Kumar
- Department of Neuroscience, City University of Hong Kong, Tat Chee Avenue, Hong Kong SAR, China
| | - Pallavi Asthana
- Department of Neuroscience, City University of Hong Kong, Tat Chee Avenue, Hong Kong SAR, China
| | - Wing Ho Yung
- School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China
| | - Kin Ming Kwan
- School of Life Sciences, Center for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong, SAR, China
| | - Chung Tin
- Department of Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Hong Kong, SAR, China
| | - Chi Him Eddie Ma
- Department of Neuroscience, City University of Hong Kong, Tat Chee Avenue, Hong Kong SAR, China.
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11
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Acute Cerebellar Inflammation and Related Ataxia: Mechanisms and Pathophysiology. Brain Sci 2022; 12:brainsci12030367. [PMID: 35326323 PMCID: PMC8946185 DOI: 10.3390/brainsci12030367] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 03/07/2022] [Accepted: 03/08/2022] [Indexed: 12/11/2022] Open
Abstract
The cerebellum governs motor coordination and motor learning. Infection with external microorganisms, such as viruses, bacteria, and fungi, induces the release and production of inflammatory mediators, which drive acute cerebellar inflammation. The clinical observation of acute cerebellitis is associated with the emergence of cerebellar ataxia. In our animal model of the acute inflammation of the cerebellar cortex, animals did not show any ataxia but hyperexcitability in the cerebellar cortex and depression-like behaviors. In contrast, animal models with neurodegeneration of the cerebellar Purkinje cells and hypoexcitability of the neurons show cerebellar ataxia. The suppression of the Ca2+-activated K+ channels in vivo is associated with a type of ataxia. Therefore, there is a gap in our interpretation between the very early phase of cerebellar inflammation and the emergence of cerebellar ataxia. In this review, we discuss the hypothesized scenario concerning the emergence of cerebellar ataxia. First, compared with genetically induced cerebellar ataxias, we introduce infection and inflammation in the cerebellum via aberrant immunity and glial responses. Especially, we focus on infections with cytomegalovirus, influenza virus, dengue virus, and SARS-CoV-2, potential relevance to mitochondrial DNA, and autoimmunity in infection. Second, we review neurophysiological modulation (intrinsic excitability, excitatory, and inhibitory synaptic transmission) by inflammatory mediators and aberrant immunity. Next, we discuss the cerebellar circuit dysfunction (presumably, via maintaining the homeostatic property). Lastly, we propose the mechanism of the cerebellar ataxia and possible treatments for the ataxia in the cerebellar inflammation.
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12
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Gilles O. K + -independent Kir blockade by external Cs + and Ba 2. Physiol Rep 2022; 10:e15200. [PMID: 35274814 PMCID: PMC8915156 DOI: 10.14814/phy2.15200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 01/14/2022] [Accepted: 01/24/2022] [Indexed: 06/14/2023] Open
Abstract
Cations such as Cs+ and Ba2+ are known to block K+ currents by entering an open channel and binding to the selectivity filter, where they obstruct the pore and block diffusion of the permeant ion. This obstruction is voltage- and K+ -dependent and is relieved by the trans permeant ion flux. The present patch-clamp study on Xenopus muscle cells shows that, unlike the voltage-activated K+ (Kv) channels, blockade of the inward rectifier K+ (Kir) channels by external foreign cations results from the combination of pore obstruction with a new and independent mechanism. This new blockade is independent of the K+ concentrations and flux and acts indiscriminately on both the outward and the inward Kir components. External Cs+ and Ba2+ compete for this blockade with free access to common channel sites. These features suggest that the blocking cations do not need to enter the channel for this new mechanism, and should bind to the extracellular side of the channel. When K+ fluxes are flowing outward, the pore obstruction is relieved for both Kir and Kv currents, and the K+ -independent blockade here described is responsible for a selective Kir inhibition, justifying the use of these external cations as tools in cell physiology studies.
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Affiliation(s)
- Ouanounou Gilles
- Université Paris‐SaclayCNRSInstitut des Neurosciences Paris‐SaclaySaclayFrance
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13
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Bunting EL, Hamilton J, Tabrizi SJ. Polyglutamine diseases. Curr Opin Neurobiol 2022; 72:39-47. [PMID: 34488036 DOI: 10.1016/j.conb.2021.07.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/29/2021] [Accepted: 07/10/2021] [Indexed: 12/11/2022]
Abstract
Polyglutamine diseases are a collection of nine CAG trinucleotide expansion disorders, presenting with a spectrum of neurological and clinical phenotypes. Recent human, mouse and cell studies of Huntington's disease have highlighted the role of DNA repair genes in somatic expansion of the CAG repeat region, modifying disease pathogenesis. Incomplete splicing of the HTT gene has also been shown to occur in humans, with the resulting exon 1 fragment most probably contributing to the Huntington's disease phenotype. In the spinocerebellar ataxias, studies have converged on transcriptional dysregulation of ion channels as a key disease modifier. In addition, advances have been made in understanding how increased levels of toxic, polyglutamine-expanded proteins can arise in the spinocerebellar ataxias through post-transcriptional and -translational modifications and autophagic mechanisms. Recent studies in spinal and bulbar muscular atrophy implicate similar pathogenic pathways to the more common polyglutamine diseases, highlighting autophagy stimulation as a potential therapeutic target. Finally, the therapeutic use of antisense oligonucleotides in several polyglutamine diseases has shown preclinical benefits and serves as potential future therapies in humans.
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Affiliation(s)
- Emma L Bunting
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Joseph Hamilton
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London, WC1N 3BG, UK
| | - Sarah J Tabrizi
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease, UCL Queen Square Institute of Neurology, Queen Square, London, WC1N 3BG, UK; UK Dementia Research Institute, University College London, London, WC1N 3BG, UK.
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14
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Velázquez-Pérez L, Rodríguez-Labrada R. Riluzole and spinocerebellar ataxia type 2: the ATRIL trial. Lancet Neurol 2022; 21:204-205. [DOI: 10.1016/s1474-4422(22)00028-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/07/2022] [Accepted: 01/10/2022] [Indexed: 12/17/2022]
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15
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Benarroch E. What Is the Role of Potassium Channels in Ataxia? Neurology 2021; 97:938-941. [PMID: 34782409 DOI: 10.1212/wnl.0000000000012870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 08/26/2021] [Indexed: 11/15/2022] Open
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16
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Perez H, Abdallah MF, Chavira JI, Norris AS, Egeland MT, Vo KL, Buechsenschuetz CL, Sanghez V, Kim JL, Pind M, Nakamura K, Hicks GG, Gatti RA, Madrenas J, Iacovino M, McKinnon PJ, Mathews PJ. A novel, ataxic mouse model of ataxia telangiectasia caused by a clinically relevant nonsense mutation. eLife 2021; 10:64695. [PMID: 34723800 PMCID: PMC8601662 DOI: 10.7554/elife.64695] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Accepted: 10/29/2021] [Indexed: 12/14/2022] Open
Abstract
Ataxia Telangiectasia (A-T) and Ataxia with Ocular Apraxia Type 1 (AOA1) are devastating neurological disorders caused by null mutations in the genome stability genes, A-T mutated (ATM) and Aprataxin (APTX), respectively. Our mechanistic understanding and therapeutic repertoire for treating these disorders are severely lacking, in large part due to the failure of prior animal models with similar null mutations to recapitulate the characteristic loss of motor coordination (i.e., ataxia) and associated cerebellar defects. By increasing genotoxic stress through the insertion of null mutations in both the Atm (nonsense) and Aptx (knockout) genes in the same animal, we have generated a novel mouse model that for the first time develops a progressively severe ataxic phenotype associated with atrophy of the cerebellar molecular layer. We find biophysical properties of cerebellar Purkinje neurons (PNs) are significantly perturbed (e.g., reduced membrane capacitance, lower action potential [AP] thresholds, etc.), while properties of synaptic inputs remain largely unchanged. These perturbations significantly alter PN neural activity, including a progressive reduction in spontaneous AP firing frequency that correlates with both cerebellar atrophy and ataxia over the animal’s first year of life. Double mutant mice also exhibit a high predisposition to developing cancer (thymomas) and immune abnormalities (impaired early thymocyte development and T-cell maturation), symptoms characteristic of A-T. Finally, by inserting a clinically relevant nonsense-type null mutation in Atm, we demonstrate that Small Molecule Read-Through (SMRT) compounds can restore ATM production, indicating their potential as a future A-T therapeutic.
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Affiliation(s)
- Harvey Perez
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - May F Abdallah
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - Jose I Chavira
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - Angelina S Norris
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - Martin T Egeland
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - Karen L Vo
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - Callan L Buechsenschuetz
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - Valentina Sanghez
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - Jeannie L Kim
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States
| | - Molly Pind
- Department of Biochemistry and Medical Genetics,Max Rady College of Medicine, University of Manitoba, Manitoba, Canada
| | - Kotoka Nakamura
- Department of Pathology & Laboratory Medicine, David Geffen School of Medicine, Los Angeles, United States
| | - Geoffrey G Hicks
- Department of Biochemistry and Medical Genetics,Max Rady College of Medicine, University of Manitoba, Manitoba, Canada
| | - Richard A Gatti
- Department of Pathology & Laboratory Medicine, David Geffen School of Medicine, Los Angeles, United States
| | - Joaquin Madrenas
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States.,Department of Medicine, Harbor-UCLA Medical Center, Torrance, United States
| | - Michelina Iacovino
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States.,Department of Pediatrics, Harbor-UCLA Medical Center, Torrance, United States
| | - Peter J McKinnon
- Center for Pediatric Neurological Disease Research, St. Jude Pediatric Translational Neuroscience Initiative, St. Jude Children's Research Hospital, Memphis, United States
| | - Paul J Mathews
- The Lundquist Institute for Biomedical Innovation, Harbor-UCLA Medical Center, Torrance, United States.,Department of Neurology, Harbor-UCLA Medical Center, Torrance, United States
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17
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Clenbuterol-sensitive delayed outward potassium currents in a cell model of spinal and bulbar muscular atrophy. Pflugers Arch 2021; 473:1213-1227. [PMID: 34021780 DOI: 10.1007/s00424-021-02559-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/09/2021] [Accepted: 03/23/2021] [Indexed: 10/21/2022]
Abstract
Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by polyglutamine (polyQ) expansions in the androgen receptor (AR) gene. SBMA is characterized by selective dysfunction and degeneration of motor neurons in the brainstem and spinal cord through still unclear mechanisms in which ion channel modulation might play a central role as for other neurodegenerative diseases. The beta2-adrenergic agonist clenbuterol was observed to ameliorate the SBMA phenotype in mice and patient-derived myotubes. However, the underlying molecular mechanism has yet to be clarified. Here, we unveil that ionic current alterations induced by the expression of polyQ-expanded AR in motor neuron-derived MN-1 cells are attenuated by the administration of clenbuterol. Our combined electrophysiological and pharmacological approach allowed us to reveal that clenbuterol modifies delayed outward potassium currents. Overall, we demonstrated that the protection provided by clenbuterol restores the normal function through the modulation of KV2-type outward potassium currents, possibly contributing to the protective effect on motor neuron toxicity in SBMA.
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18
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Farini D, Cesari E, Weatheritt RJ, La Sala G, Naro C, Pagliarini V, Bonvissuto D, Medici V, Guerra M, Di Pietro C, Rizzo FR, Musella A, Carola V, Centonze D, Blencowe BJ, Marazziti D, Sette C. A Dynamic Splicing Program Ensures Proper Synaptic Connections in the Developing Cerebellum. Cell Rep 2021; 31:107703. [PMID: 32492419 DOI: 10.1016/j.celrep.2020.107703] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 03/13/2020] [Accepted: 05/07/2020] [Indexed: 12/14/2022] Open
Abstract
Tight coordination of gene expression in the developing cerebellum is crucial for establishment of neuronal circuits governing motor and cognitive function. However, transcriptional changes alone do not explain all of the switches underlying neuronal differentiation. Here we unveiled a widespread and highly dynamic splicing program that affects synaptic genes in cerebellar neurons. The motifs enriched in modulated exons implicated the splicing factor Sam68 as a regulator of this program. Sam68 controls splicing of exons with weak branchpoints by directly binding near the 3' splice site and competing with U2AF recruitment. Ablation of Sam68 disrupts splicing regulation of synaptic genes associated with neurodevelopmental diseases and impairs synaptic connections and firing of Purkinje cells, resulting in motor coordination defects, ataxia, and abnormal social behavior. These findings uncover an unexpectedly dynamic splicing regulatory network that shapes the synapse in early life and establishes motor and cognitive circuitry in the developing cerebellum.
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Affiliation(s)
- Donatella Farini
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy; Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Eleonora Cesari
- Department of Neuroscience, Section of Human Anatomy, Catholic University of the Sacred Heart, Rome, Italy; Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | - Robert J Weatheritt
- Donnelly Centre and Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada; EMBL Australia, Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
| | - Gina La Sala
- Institute of Cell Biology and Neurobiology, CNR, Monterotondo, Rome, Italy
| | - Chiara Naro
- Department of Neuroscience, Section of Human Anatomy, Catholic University of the Sacred Heart, Rome, Italy; Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | - Vittoria Pagliarini
- Department of Neuroscience, Section of Human Anatomy, Catholic University of the Sacred Heart, Rome, Italy; Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | - Davide Bonvissuto
- Department of Neuroscience, Section of Human Anatomy, Catholic University of the Sacred Heart, Rome, Italy
| | - Vanessa Medici
- Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy; Fondazione Santa Lucia, IRCCS, Rome, Italy
| | - Marika Guerra
- Department of Neuroscience, Section of Human Anatomy, Catholic University of the Sacred Heart, Rome, Italy; Fondazione Policlinico Universitario A. Gemelli, IRCCS, Rome, Italy
| | - Chiara Di Pietro
- Institute of Cell Biology and Neurobiology, CNR, Monterotondo, Rome, Italy
| | - Francesca Romana Rizzo
- Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy; San Raffaele Pisana and University San Raffaele, IRCCS, Rome, Italy
| | | | - Valeria Carola
- Fondazione Santa Lucia, IRCCS, Rome, Italy; Department of Dynamic and Clinical Psychology, University of Rome Sapienza, Rome, Italy
| | - Diego Centonze
- Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy; Unit of Neurology, IRCCS Neuromed, Pozzilli, Isernia, Italy
| | - Benjamin J Blencowe
- Donnelly Centre and Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Daniela Marazziti
- Institute of Cell Biology and Neurobiology, CNR, Monterotondo, Rome, Italy
| | - Claudio Sette
- Fondazione Santa Lucia, IRCCS, Rome, Italy; Department of Neuroscience, Section of Human Anatomy, Catholic University of the Sacred Heart, Rome, Italy.
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19
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Carpenter JC, Männikkö R, Heffner C, Heneine J, Sampedro‐Castañeda M, Lignani G, Schorge S. Progressive myoclonus epilepsy KCNC1 variant causes a developmental dendritopathy. Epilepsia 2021; 62:1256-1267. [PMID: 33735526 PMCID: PMC8436768 DOI: 10.1111/epi.16867] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 02/17/2021] [Accepted: 02/17/2021] [Indexed: 12/19/2022]
Abstract
OBJECTIVE Mutations in KCNC1 can cause severe neurological dysfunction, including intellectual disability, epilepsy, and ataxia. The Arg320His variant, which occurs in the voltage-sensing domain of the channel, causes a highly penetrant and specific form of progressive myoclonus epilepsy with severe ataxia, designated myoclonus epilepsy and ataxia due to potassium channel mutation (MEAK). KCNC1 encodes the voltage-gated potassium channel KV 3.1, a channel that is important for enabling high-frequency firing in interneurons, raising the possibility that MEAK is associated with reduced interneuronal function. METHODS To determine how this variant triggers MEAK, we expressed KV 3.1bR320H in cortical interneurons in vitro and investigated the effects on neuronal function and morphology. We also performed electrophysiological recordings of oocytes expressing KV 3.1b to determine whether the mutation introduces gating pore currents. RESULTS Expression of the KV 3.1bR320H variant profoundly reduced excitability of mature cortical interneurons, and cells expressing these channels were unable to support high-frequency firing. The mutant channel also had an unexpected effect on morphology, severely impairing neurite development and interneuron viability, an effect that could not be rescued by blocking KV 3 channels. Oocyte recordings confirmed that in the adult KV 3.1b isoform, R320H confers a dominant negative loss-of-function effect by slowing channel activation, but does not introduce potentially toxic gating pore currents. SIGNIFICANCE Overall, our data suggest that, in addition to the regulation of high-frequency firing, KV 3.1 channels play a hitherto unrecognized role in neuronal development. MEAK may be described as a developmental dendritopathy.
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Affiliation(s)
- Jenna C. Carpenter
- Department of Clinical and Experimental EpilepsyUniversity College London Queen Square Institute of NeurologyLondonUK
| | - Roope Männikkö
- Department of Neuromuscular DiseasesUniversity College London Queen Square Institute of NeurologyLondonUK
| | - Catherine Heffner
- Department of Clinical and Experimental EpilepsyUniversity College London Queen Square Institute of NeurologyLondonUK
| | - Jana Heneine
- Department of Clinical and Experimental EpilepsyUniversity College London Queen Square Institute of NeurologyLondonUK
| | - Marisol Sampedro‐Castañeda
- Department of Clinical and Experimental EpilepsyUniversity College London Queen Square Institute of NeurologyLondonUK
| | - Gabriele Lignani
- Department of Clinical and Experimental EpilepsyUniversity College London Queen Square Institute of NeurologyLondonUK
| | - Stephanie Schorge
- Department of PharmacologyUniversity College London School of PharmacyLondonUK
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20
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Bushart DD, Zalon AJ, Zhang H, Morrison LM, Guan Y, Paulson HL, Shakkottai VG, McLoughlin HS. Antisense Oligonucleotide Therapy Targeted Against ATXN3 Improves Potassium Channel-Mediated Purkinje Neuron Dysfunction in Spinocerebellar Ataxia Type 3. CEREBELLUM (LONDON, ENGLAND) 2021; 20:41-53. [PMID: 32789747 PMCID: PMC7930886 DOI: 10.1007/s12311-020-01179-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Spinocerebellar ataxia type 3 (SCA3) is the second-most common CAG repeat disease, caused by a glutamine-encoding expansion in the ATXN3 protein. SCA3 is characterized by spinocerebellar degeneration leading to progressive motor incoordination and early death. Previous studies suggest that potassium channel dysfunction underlies early abnormalities in cerebellar cortical Purkinje neuron firing in SCA3. However, cerebellar cortical degeneration is often modest both in the human disease and mouse models of SCA3, raising uncertainty about the role of cerebellar dysfunction in SCA3. Here, we address this question by investigating Purkinje neuron excitability in SCA3. In early-stage SCA3 mice, we confirm a previously identified increase in excitability of cerebellar Purkinje neurons and associate this excitability with reduced transcripts of two voltage-gated potassium (KV) channels, Kcna6 and Kcnc3, as well as motor impairment. Intracerebroventricular delivery of antisense oligonucleotides (ASO) to reduce mutant ATXN3 restores normal excitability to SCA3 Purkinje neurons and rescues transcript levels of Kcna6 and Kcnc3. Interestingly, while an even broader range of KV channel transcripts shows reduced levels in late-stage SCA3 mice, cerebellar Purkinje neuron physiology was not further altered despite continued worsening of motor impairment. These results suggest the progressive motor phenotype observed in SCA3 may not reflect ongoing changes in the cerebellar cortex but instead dysfunction of other neuronal structures within and beyond the cerebellum. Nevertheless, the early rescue of both KV channel expression and neuronal excitability by ASO treatment suggests that cerebellar cortical dysfunction contributes meaningfully to motor dysfunction in SCA3.
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Affiliation(s)
- David D. Bushart
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109
| | - Annie J. Zalon
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109
| | - Hongjiu Zhang
- Department of Computational Medicine & Bioinformatics, University of Michigan, Ann Arbor, MI 48109,Microsoft, Inc. Bellevue, WA 98004
| | - Logan M. Morrison
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109
| | - Yuanfang Guan
- Department of Computational Medicine & Bioinformatics, University of Michigan, Ann Arbor, MI 48109
| | - Henry L. Paulson
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109
| | - Vikram G. Shakkottai
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109,Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, MI 48109,Address correspondence to: Vikram G. Shakkottai, 4009 BSRB, 109 Zina Pitcher Pl., Ann Arbor, MI 48109, ; Hayley S. McLoughlin, 4017 BSRB, 109 Zina Pitcher Pl., Ann Arbor, MI 48109,
| | - Hayley S. McLoughlin
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109,Address correspondence to: Vikram G. Shakkottai, 4009 BSRB, 109 Zina Pitcher Pl., Ann Arbor, MI 48109, ; Hayley S. McLoughlin, 4017 BSRB, 109 Zina Pitcher Pl., Ann Arbor, MI 48109,
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21
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Chronic unpredictable stress induces depression-related behaviors by suppressing AgRP neuron activity. Mol Psychiatry 2021; 26:2299-2315. [PMID: 33432188 PMCID: PMC8272726 DOI: 10.1038/s41380-020-01004-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 12/13/2020] [Accepted: 12/15/2020] [Indexed: 02/06/2023]
Abstract
Previous studies have shown that AgRP neurons in the arcuate nucleus (ARC) respond to energy deficits and play a key role in the control of feeding behavior and metabolism. Here, we demonstrate that chronic unpredictable stress, an animal model of depression, decreases spontaneous firing rates, increases firing irregularity and alters the firing properties of AgRP neurons in both male and female mice. These changes are associated with enhanced inhibitory synaptic transmission and reduced intrinsic neuronal excitability. Chemogenetic inhibition of AgRP neurons increases susceptibility to subthreshold unpredictable stress. Conversely, chemogenetic activation of AgRP neurons completely reverses anhedonic and despair behaviors induced by chronic unpredictable stress. These results indicate that chronic stress induces maladaptive synaptic and intrinsic plasticity, leading to hypoactivity of AgRP neurons and subsequently causing behavioral changes. Our findings suggest that AgRP neurons in the ARC are a key component of neural circuitry involved in mediating depression-related behaviors and that increasing AgRP neuronal activity coule be a novel and effective treatment for depression.
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22
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Chopra R, Bushart DD, Cooper JP, Yellajoshyula D, Morrison LM, Huang H, Handler HP, Man LJ, Dansithong W, Scoles DR, Pulst SM, Orr HT, Shakkottai VG. Altered Capicua expression drives regional Purkinje neuron vulnerability through ion channel gene dysregulation in spinocerebellar ataxia type 1. Hum Mol Genet 2020; 29:3249-3265. [PMID: 32964235 PMCID: PMC7689299 DOI: 10.1093/hmg/ddaa212] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/19/2020] [Accepted: 09/17/2020] [Indexed: 12/22/2022] Open
Abstract
Selective neuronal vulnerability in neurodegenerative disease is poorly understood. Using the ATXN1[82Q] model of spinocerebellar ataxia type 1 (SCA1), we explored the hypothesis that regional differences in Purkinje neuron degeneration could provide novel insights into selective vulnerability. ATXN1[82Q] Purkinje neurons from the anterior cerebellum were found to degenerate earlier than those from the nodular zone, and this early degeneration was associated with selective dysregulation of ion channel transcripts and altered Purkinje neuron spiking. Efforts to understand the basis for selective dysregulation of channel transcripts revealed modestly increased expression of the ATXN1 co-repressor Capicua (Cic) in anterior cerebellar Purkinje neurons. Importantly, disrupting the association between ATXN1 and Cic rescued the levels of these ion channel transcripts, and lentiviral overexpression of Cic in the nodular zone accelerated both aberrant Purkinje neuron spiking and neurodegeneration. These findings reinforce the central role for Cic in SCA1 cerebellar pathophysiology and suggest that only modest reductions in Cic are needed to have profound therapeutic impact in SCA1.
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Affiliation(s)
- Ravi Chopra
- Medical Scientist Training Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Neurology, Washington University in St. Louis, Saint Louis, MO 63110, USA
| | - David D Bushart
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
- Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - John P Cooper
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Molecular Biosciences and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
| | | | - Logan M Morrison
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Haoran Huang
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Hillary P Handler
- Department of Laboratory Medicine and Pathology, Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Luke J Man
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Warunee Dansithong
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Daniel R Scoles
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Stefan M Pulst
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Harry T Orr
- Department of Laboratory Medicine and Pathology, Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Vikram G Shakkottai
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
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23
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Bushart DD, Huang H, Man LJ, Morrison LM, Shakkottai VG. A Chlorzoxazone-Baclofen Combination Improves Cerebellar Impairment in Spinocerebellar Ataxia Type 1. Mov Disord 2020; 36:622-631. [PMID: 33151010 DOI: 10.1002/mds.28355] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 09/29/2020] [Accepted: 10/12/2020] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND A combination of central muscle relaxants, chlorzoxazone and baclofen (chlorzoxazone-baclofen), has been proposed for treatment of cerebellar symptoms in human spinocerebellar ataxia. However, central muscle relaxants can worsen balance. The optimal dose for target engagement without toxicity remains unknown. Using the genetically precise Atxn1154Q/2Q model of spinocerebellar ataxia type 1, we aimed to determine the role of cerebellar dysfunction in motor impairment. We also aimed to identify appropriate concentrations of chlorzoxazone-baclofen needed for target engagement without toxicity to plan for human clinical trials. METHODS We use patch clamp electrophysiology in acute cerebellar slices and immunostaining to identify the specific ion channels targeted by chlorzoxazone-baclofen. Behavioral assays for coordination and grip strength are used to determine specificity of chlorzoxazone-baclofen for improving cerebellar dysfunction without off-target effects in Atxn1154Q/2Q mice. RESULTS We identify irregular Purkinje neuron firing in association with reduced expression of ion channels Kcnma1 and Cacna1g in Atxn1154Q/2Q mice. Using in vitro electrophysiology in brain slices, we identified concentrations of chlorzoxazone-baclofen that improve Purkinje neuron spike regularity without reducing firing frequency. At a disease stage in Atxn1154Q/2Q mice when motor impairment is due to cerebellar dysfunction, orally administered chlorzoxazone-baclofen improves motor performance without affecting muscle strength. CONCLUSION We identify a tight relationship between baclofen-chlorzoxazone concentrations needed to engage target and levels above which cerebellar function will be compromised. We propose to use this information for a novel clinical trial design, using sequential dose escalation within each subject, to identify dose levels that are likely to improve ataxia symptoms while minimizing toxicity. © 2020 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- David D Bushart
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, USA.,Ohio State University College of Medicine, Columbus, Ohio, USA
| | - Haoran Huang
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, USA
| | - Luke J Man
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, USA
| | - Logan M Morrison
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, Michigan, USA
| | - Vikram G Shakkottai
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, USA.,Department of Molecular & Integrative Physiology, University of Michigan, Ann Arbor, Michigan, USA
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24
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Martínez-Rojas VA, Jiménez-Garduño AM, Michelatti D, Tosatto L, Marchioretto M, Arosio D, Basso M, Pennuto M, Musio C. ClC-2-like Chloride Current Alterations in a Cell Model of Spinal and Bulbar Muscular Atrophy, a Polyglutamine Disease. J Mol Neurosci 2020; 71:662-674. [PMID: 32856205 DOI: 10.1007/s12031-020-01687-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 08/14/2020] [Indexed: 12/21/2022]
Abstract
Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by expansions of a polyglutamine (polyQ) tract in the androgen receptor (AR) gene. SBMA is associated with the progressive loss of lower motor neurons, together with muscle weakness and atrophy. PolyQ-AR is converted to a toxic species upon binding to its natural ligands, testosterone, and dihydrotestosterone (DHT). Our previous patch-clamp studies on a motor neuron-derived cell model of SBMA showed alterations in voltage-gated ion currents. Here, we identified and characterized chloride currents most likely belonging to the chloride channel-2 (ClC-2) subfamily, which showed significantly increased amplitudes in the SBMA cells. The treatment with the pituitary adenylyl cyclase-activating polypeptide (PACAP), a neuropeptide with a proven protective effect in a mouse model of SBMA, recovered chloride channel current alterations in SBMA cells. These observations suggest that the CIC-2 currents are affected in SBMA, an alteration that may contribute and potentially determine the pathophysiology of the disease.
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Affiliation(s)
- Vladimir A Martínez-Rojas
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) & LabSSAH, Bruno Kessler Foundation (FBK), Trento, Italy
| | - Aura M Jiménez-Garduño
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) & LabSSAH, Bruno Kessler Foundation (FBK), Trento, Italy.,Departamento de Ciencias de la Salud, Escuela de Ciencias, Universidad de las Américas Puebla (UDLAP), San Andrés Cholula, Puebla, Mexico
| | - Daniela Michelatti
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) & LabSSAH, Bruno Kessler Foundation (FBK), Trento, Italy.,CIBIO Department, Laboratory of Chromatin Biology and Epigenetics, University of Trento, Trento, Italy
| | - Laura Tosatto
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) & LabSSAH, Bruno Kessler Foundation (FBK), Trento, Italy
| | - Marta Marchioretto
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) & LabSSAH, Bruno Kessler Foundation (FBK), Trento, Italy
| | - Daniele Arosio
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) & LabSSAH, Bruno Kessler Foundation (FBK), Trento, Italy
| | - Manuela Basso
- CIBIO Department, Laboratory of Transcriptional Neurobiology, University of Trento, Trento, Italy
| | - Maria Pennuto
- Department of Biomedical Sciences, University of Padova, Padova, Italy.,Padova Neuroscience Center (PNC), University of Padova, Padova, Italy.,Veneto Institute of Molecular Medicine, Padova, Italy
| | - Carlo Musio
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) & LabSSAH, Bruno Kessler Foundation (FBK), Trento, Italy.
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25
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Robinson KJ, Watchon M, Laird AS. Aberrant Cerebellar Circuitry in the Spinocerebellar Ataxias. Front Neurosci 2020; 14:707. [PMID: 32765211 PMCID: PMC7378801 DOI: 10.3389/fnins.2020.00707] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 06/11/2020] [Indexed: 12/11/2022] Open
Abstract
The spinocerebellar ataxias (SCAs) are a heterogeneous group of neurodegenerative diseases that share convergent disease features. A common symptom of these diseases is development of ataxia, involving impaired balance and motor coordination, usually stemming from cerebellar dysfunction and neurodegeneration. For most spinocerebellar ataxias, pathology can be attributed to an underlying gene mutation and the impaired function of the encoded protein through loss or gain-of-function effects. Strikingly, despite vast heterogeneity in the structure and function of disease-causing genes across the SCAs and the cellular processes affected, the downstream effects have considerable overlap, including alterations in cerebellar circuitry. Interestingly, aberrant function and degeneration of Purkinje cells, the major output neuronal population present within the cerebellum, precedes abnormalities in other neuronal populations within many SCAs, suggesting that Purkinje cells have increased vulnerability to cellular perturbations. Factors that are known to contribute to perturbed Purkinje cell function in spinocerebellar ataxias include altered gene expression resulting in altered expression or functionality of proteins and channels that modulate membrane potential, downstream impairments in intracellular calcium homeostasis and changes in glutamatergic input received from synapsing climbing or parallel fibers. This review will explore this enhanced vulnerability and the aberrant cerebellar circuitry linked with it in many forms of SCA. It is critical to understand why Purkinje cells are vulnerable to such insults and what overlapping pathogenic mechanisms are occurring across multiple SCAs, despite different underlying genetic mutations. Enhanced understanding of disease mechanisms will facilitate the development of treatments to prevent or slow progression of the underlying neurodegenerative processes, cerebellar atrophy and ataxic symptoms.
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Affiliation(s)
| | | | - Angela S. Laird
- Centre for Motor Neuron Disease Research, Department of Biomedical Science, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, NSW, Australia
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26
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Cook AA, Fields E, Watt AJ. Losing the Beat: Contribution of Purkinje Cell Firing Dysfunction to Disease, and Its Reversal. Neuroscience 2020; 462:247-261. [PMID: 32554108 DOI: 10.1016/j.neuroscience.2020.06.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 06/01/2020] [Accepted: 06/05/2020] [Indexed: 02/06/2023]
Abstract
The cerebellum is a brain structure that is highly interconnected with other brain regions. There are many contributing factors to cerebellar-related brain disease, such as altered afferent input, local connectivity, and/or cerebellar output. Purkinje cells (PC) are the principle cells of the cerebellar cortex, and fire intrinsically; that is, they fire spontaneous action potentials at high frequencies. This review paper focuses on PC intrinsic firing activity, which is altered in multiple neurological diseases, including ataxia, Huntington Disease (HD) and autism spectrum disorder (ASD). Notably, there are several cases where interventions that restore or rescue PC intrinsic activity also improve impaired behavior in these mouse models of disease. These findings suggest that rescuing PC firing deficits themselves may be sufficient to improve impairment in cerebellar-related behavior in disease. We propose that restoring PC intrinsic firing represents a good target for drug development that might be of therapeutic use for several disorders.
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Affiliation(s)
- Anna A Cook
- Department of Biology, McGill University, Montreal, Canada
| | - Eviatar Fields
- Department of Biology, McGill University, Montreal, Canada; Integrated Program in Neuroscience, McGill University, Montreal, Canada
| | - Alanna J Watt
- Department of Biology, McGill University, Montreal, Canada.
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27
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Sui X, Yang J, Zhang G, Yuan X, Li W, Long J, Luo Y, Li Y, Wang Y. NLRP3 inflammasome inhibition attenuates subacute neurotoxicity induced by acrylamide in vitro and in vivo. Toxicology 2020; 432:152392. [PMID: 32014472 DOI: 10.1016/j.tox.2020.152392] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 01/29/2020] [Accepted: 01/30/2020] [Indexed: 02/07/2023]
Abstract
Acrylamide (AA) constitutes an important industrial chemical agent and well-known neurotoxin. However, the mechanism underlying AA-mediated neurotoxicity is extremely complicated and controversial. In this study, we found that activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome and its subsequent downstream inflammatory responses plays an important role in AA-induced neurotoxicity mechanisms. In vitro experiments revealed that AA (2.5 mM) induced BV2 microglial cytotoxicity and triggered NLRP3 inflammasome activation along with downstream proinflammatory cytokine interleukin-1β and interleukin-18 expression. Treatment with inhibitor or NLRP3 siRNA efficiently protected BV2 microglial cells against AA-induced cytotoxicity and reversed NLRP3 inflammasome activation and its mediated inflammatory reaction. Similarly, AA exposure (50 mg/kg) for 10 consecutive days caused significant activation of NLRP3 inflammasomes and neuroinflammation in C57BL/6 mice, whereas inhibiting these effects through specific NLRP3 inflammasome blocker MCC950 (5 mg/kg) intervention or NLRP3 knock-out significantly ameliorated AA-induced ataxia, cerebellar Purkinje cells degeneration, and apoptosis. Furthermore, we demonstrated that antagonism of NLRP3 could also up-regulate the Nrf2 signalling pathway and related antioxidant genes. In conclusion, our findings indicate that activation of the NLRP3 inflammasome pathway is involved in AA-induced neurotoxicity, whereas MCC950 treatment or NLRP3 knock-out could effectively protect against AA-induced neurotoxic injury through the inhibition of neuroinflammation and activation of the Nrf2 antioxidant pathway. Therefore, the NLRP3 inflammasome might serve as a promising therapeutic target, with drugs designed to specifically inhibit this pathway potentially providing new avenues for preventing or ameliorating AA poisoning.
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Affiliation(s)
- Xin Sui
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China
| | - Jun Yang
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China
| | - Guangzhou Zhang
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China
| | - XiaoFeng Yuan
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China
| | - WanHua Li
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China
| | - JianHai Long
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China
| | - Yuan Luo
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China.
| | - Yunfeng Li
- Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China.
| | - Yongan Wang
- State Key Laboratory of Toxicology and Medical Countermeasures, Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences, No 27, Taiping Road, Haidian District, Beijing, 100850, China.
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28
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Sathyanesan A, Zhou J, Scafidi J, Heck DH, Sillitoe RV, Gallo V. Emerging connections between cerebellar development, behaviour and complex brain disorders. Nat Rev Neurosci 2019; 20:298-313. [PMID: 30923348 DOI: 10.1038/s41583-019-0152-2] [Citation(s) in RCA: 144] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The human cerebellum has a protracted developmental timeline compared with the neocortex, expanding the window of vulnerability to neurological disorders. As the cerebellum is critical for motor behaviour, it is not surprising that most neurodevelopmental disorders share motor deficits as a common sequela. However, evidence gathered since the late 1980s suggests that the cerebellum is involved in motor and non-motor function, including cognition and emotion. More recently, evidence indicates that major neurodevelopmental disorders such as intellectual disability, autism spectrum disorder, attention-deficit hyperactivity disorder and Down syndrome have potential links to abnormal cerebellar development. Out of recent findings from clinical and preclinical studies, the concept of the 'cerebellar connectome' has emerged that can be used as a framework to link the role of cerebellar development to human behaviour, disease states and the design of better therapeutic strategies.
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Affiliation(s)
- Aaron Sathyanesan
- Center for Neuroscience Research, Children's Research Institute, Children's National Health System, Washington, DC, USA.
| | - Joy Zhou
- Department of Pathology and Immunology, Baylor College of Medicine, Jan and Dan Duncan Neurological Research Institute of Texas Children's Hospital, Houston, TX, USA.,Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA
| | - Joseph Scafidi
- Center for Neuroscience Research, Children's Research Institute, Children's National Health System, Washington, DC, USA.,George Washington University School of Medicine and Health Sciences, Washington, DC, USA
| | - Detlef H Heck
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, USA
| | - Roy V Sillitoe
- Department of Pathology and Immunology, Baylor College of Medicine, Jan and Dan Duncan Neurological Research Institute of Texas Children's Hospital, Houston, TX, USA.,Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA.,Program in Developmental Biology, Baylor College of Medicine, Houston, TX, USA
| | - Vittorio Gallo
- Center for Neuroscience Research, Children's Research Institute, Children's National Health System, Washington, DC, USA. .,George Washington University School of Medicine and Health Sciences, Washington, DC, USA.
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29
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Nicotinamide Pathway-Dependent Sirt1 Activation Restores Calcium Homeostasis to Achieve Neuroprotection in Spinocerebellar Ataxia Type 7. Neuron 2019; 105:630-644.e9. [PMID: 31859031 DOI: 10.1016/j.neuron.2019.11.019] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 09/18/2019] [Accepted: 11/12/2019] [Indexed: 12/22/2022]
Abstract
Sirtuin 1 (Sirt1) is a NAD+-dependent deacetylase capable of countering age-related neurodegeneration, but the basis of Sirt1 neuroprotection remains elusive. Spinocerebellar ataxia type 7 (SCA7) is an inherited CAG-polyglutamine repeat disorder. Transcriptome analysis of SCA7 mice revealed downregulation of calcium flux genes accompanied by abnormal calcium-dependent cerebellar membrane excitability. Transcription-factor binding-site analysis of downregulated genes yielded Sirt1 target sites, and we observed reduced Sirt1 activity in the SCA7 mouse cerebellum with NAD+ depletion. SCA7 patients displayed increased poly(ADP-ribose) in cerebellar neurons, supporting poly(ADP-ribose) polymerase-1 upregulation. We crossed Sirt1-overexpressing mice with SCA7 mice and noted rescue of neurodegeneration and calcium flux defects. NAD+ repletion via nicotinamide riboside ameliorated disease phenotypes in SCA7 mice and patient stem cell-derived neurons. Sirt1 thus achieves neuroprotection by promoting calcium regulation, and NAD+ dysregulation underlies Sirt1 dysfunction in SCA7, indicating that cerebellar ataxias exhibit altered calcium homeostasis because of metabolic dysregulation, suggesting shared therapy targets.
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Egorova PA, Bezprozvanny IB. Molecular Mechanisms and Therapeutics for Spinocerebellar Ataxia Type 2. Neurotherapeutics 2019; 16:1050-1073. [PMID: 31435879 PMCID: PMC6985344 DOI: 10.1007/s13311-019-00777-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The effective therapeutic treatment and the disease-modifying therapy for spinocerebellar ataxia type 2 (SCA2) (a progressive hereditary disease caused by an expansion of polyglutamine in the ataxin-2 protein) is not available yet. At present, only symptomatic treatment and methods of palliative care are prescribed to the patients. Many attempts were made to study the physiological, molecular, and biochemical changes in SCA2 patients and in a variety of the model systems to find new therapeutic targets for SCA2 treatment. A better understanding of the uncovered molecular mechanisms of the disease allowed the scientific community to develop strategies of potential therapy and helped to create some promising therapeutic approaches for SCA2 treatment. Recent progress in this field will be discussed in this review article.
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Affiliation(s)
- Polina A Egorova
- Laboratory of Molecular Neurodegeneration, Peter the Great St.Petersburg Polytechnic University, St. Petersburg, 195251, Russia
| | - Ilya B Bezprozvanny
- Laboratory of Molecular Neurodegeneration, Peter the Great St.Petersburg Polytechnic University, St. Petersburg, 195251, Russia.
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, ND12.200, Dallas, Texas, 75390, USA.
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31
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Srinivasan SR, Shakkottai VG. Moving Towards Therapy in SCA1: Insights from Molecular Mechanisms, Identification of Novel Targets, and Planning for Human Trials. Neurotherapeutics 2019; 16:999-1008. [PMID: 31338702 PMCID: PMC6985354 DOI: 10.1007/s13311-019-00763-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The spinocerebellar ataxias (SCAs) are a group of neurodegenerative disorders inherited in an autosomal dominant fashion. The SCAs result in progressive gait imbalance, incoordination of the limbs, speech changes, and oculomotor dysfunction, among other symptoms. Over the past few decades, significant strides have been made in understanding the pathogenic mechanisms underlying these diseases. Although multiple efforts using a combination of genetics and pharmacology with small molecules have been made towards developing new therapeutics, no FDA approved treatment currently exists. In this review, we focus on SCA1, a common SCA subtype, in which some of the greatest advances have been made in understanding disease biology, and consequently potential therapeutic targets. Understanding of the underlying basic biology and targets of therapy in SCA1 is likely to give insight into treatment strategies in other SCAs. The diversity of the biology in the SCAs, and insight from SCA1 suggests, however, that both shared treatment strategies and specific approaches tailored to treat distinct genetic causes of SCA are likely needed for this group of devastating neurological disorders.
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Affiliation(s)
| | - Vikram G Shakkottai
- Department of Neurology, University of Michigan, Ann Arbor, Michigan, USA.
- Department of Molecular and Integrative Physiology, University of Michigan, 4009 BSRB, 109 Zina Pitcher Place, Ann Arbor, Michigan, 48109, USA.
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Abstract
The spinocerebellar ataxias (SCAs) comprise more than 40 autosomal dominant neurodegenerative disorders that present principally with progressive ataxia. Within the past few years, studies of pathogenic mechanisms in the SCAs have led to the development of promising therapeutic strategies, especially for SCAs caused by polyglutamine-coding CAG repeats. Nucleotide-based gene-silencing approaches that target the first steps in the pathogenic cascade are one promising approach not only for polyglutamine SCAs but also for the many other SCAs caused by toxic mutant proteins or RNA. For these and other emerging therapeutic strategies, well-coordinated preparation is needed for fruitful clinical trials. To accomplish this goal, investigators from the United States and Europe are now collaborating to share data from their respective SCA cohorts. Increased knowledge of the natural history of SCAs, including of the premanifest and early symptomatic stages of disease, will improve the prospects for success in clinical trials of disease-modifying drugs. In addition, investigators are seeking validated clinical outcome measures that demonstrate responsiveness to changes in SCA populations. Findings suggest that MRI and magnetic resonance spectroscopy biomarkers will provide objective biological readouts of disease activity and progression, but more work is needed to establish disease-specific biomarkers that track target engagement in therapeutic trials. Together, these efforts suggest that the development of successful therapies for one or more SCAs is not far away.
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Sen NE, Canet-Pons J, Halbach MV, Arsovic A, Pilatus U, Chae WH, Kaya ZE, Seidel K, Rollmann E, Mittelbronn M, Meierhofer D, De Zeeuw CI, Bosman LWJ, Gispert S, Auburger G. Generation of an Atxn2-CAG100 knock-in mouse reveals N-acetylaspartate production deficit due to early Nat8l dysregulation. Neurobiol Dis 2019; 132:104559. [PMID: 31376479 DOI: 10.1016/j.nbd.2019.104559] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/16/2019] [Accepted: 07/30/2019] [Indexed: 12/13/2022] Open
Abstract
Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disorder caused by CAG-expansion mutations in the ATXN2 gene, mainly affecting motor neurons in the spinal cord and Purkinje neurons in the cerebellum. While the large expansions were shown to cause SCA2, the intermediate length expansions lead to increased risk for several atrophic processes including amyotrophic lateral sclerosis and Parkinson variants, e.g. progressive supranuclear palsy. Intense efforts to pioneer a neuroprotective therapy for SCA2 require longitudinal monitoring of patients and identification of crucial molecular pathways. The ataxin-2 (ATXN2) protein is mainly involved in RNA translation control and regulation of nutrient metabolism during stress periods. The preferential mRNA targets of ATXN2 are yet to be determined. In order to understand the molecular disease mechanism throughout different prognostic stages, we generated an Atxn2-CAG100-knock-in (KIN) mouse model of SCA2 with intact murine ATXN2 expression regulation. Its characterization revealed somatic mosaicism of the expansion, with shortened lifespan, a progressive spatio-temporal pattern of pathology with subsequent phenotypes, and anomalies of brain metabolites such as N-acetylaspartate (NAA), all of which mirror faithfully the findings in SCA2 patients. Novel molecular analyses from stages before the onset of motor deficits revealed a strong selective effect of ATXN2 on Nat8l mRNA which encodes the enzyme responsible for NAA synthesis. This metabolite is a prominent energy store of the brain and a well-established marker for neuronal health. Overall, we present a novel authentic rodent model of SCA2, where in vivo magnetic resonance imaging was feasible to monitor progression and where the definition of earliest transcriptional abnormalities was possible. We believe that this model will not only reveal crucial insights regarding the pathomechanism of SCA2 and other ATXN2-associated disorders, but will also aid in developing gene-targeted therapies and disease prevention.
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Affiliation(s)
- Nesli-Ece Sen
- Experimental Neurology, Goethe University Medical School, 60590 Frankfurt am Main, Germany
| | - Júlia Canet-Pons
- Experimental Neurology, Goethe University Medical School, 60590 Frankfurt am Main, Germany
| | - Melanie V Halbach
- Experimental Neurology, Goethe University Medical School, 60590 Frankfurt am Main, Germany
| | - Aleksandar Arsovic
- Experimental Neurology, Goethe University Medical School, 60590 Frankfurt am Main, Germany
| | - Ulrich Pilatus
- Institute of Neuroradiology, Goethe University Medical School, 60590 Frankfurt am Main, Germany
| | - Woon-Hyung Chae
- Georg-Speyer-Haus, Institute for Tumor Biology and Experimental Therapy, 60596 Frankfurt am Main, Germany
| | - Zeynep-Ece Kaya
- Experimental Neurology, Goethe University Medical School, 60590 Frankfurt am Main, Germany; Department of Neurology, Cerrahpasa School of Medicine, Istanbul University, 34098 Istanbul, Turkey
| | - Kay Seidel
- Department of Anatomy II, Institute of Clinical Neuroanatomy, Goethe University, 60590 Frankfurt am Main, Germany
| | - Ewa Rollmann
- Experimental Neurology, Goethe University Medical School, 60590 Frankfurt am Main, Germany
| | - Michel Mittelbronn
- Neurological Institute (Edinger Institute), Goethe University, 60590 Frankfurt am Main, Germany; Luxembourg Centre of Neuropathology (LCNP), Luxembourg; Department of Pathology, Laboratoire National de Santé (LNS), Dudelange, Luxembourg; Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Esch-sur-Alzette, Luxembourg; Department of Oncology, NORLUX Neuro-Oncology Laboratory, Luxembourg Institute of Health (LIH), Luxembourg
| | - David Meierhofer
- Max Planck Institute for Molecular Genetics, 14195 Berlin, Germany
| | - Chris I De Zeeuw
- Netherlands Institute for Neuroscience, Royal Academy of Arts and Sciences, 1105 BA Amsterdam, the Netherlands; Department of Neuroscience, Erasmus Medical Center, 3000 CA Rotterdam, the Netherlands
| | - Laurens W J Bosman
- Department of Neuroscience, Erasmus Medical Center, 3000 CA Rotterdam, the Netherlands
| | - Suzana Gispert
- Experimental Neurology, Goethe University Medical School, 60590 Frankfurt am Main, Germany
| | - Georg Auburger
- Experimental Neurology, Goethe University Medical School, 60590 Frankfurt am Main, Germany.
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Abstract
The spinocerebellar ataxias (SCAs) are a genetically heterogeneous group of autosomal dominantly inherited progressive disorders, the clinical hallmark of which is loss of balance and coordination accompanied by slurred speech; onset is most often in adult life. Genetically, SCAs are grouped as repeat expansion SCAs, such as SCA3/Machado-Joseph disease (MJD), and rare SCAs that are caused by non-repeat mutations, such as SCA5. Most SCA mutations cause prominent damage to cerebellar Purkinje neurons with consecutive cerebellar atrophy, although Purkinje neurons are only mildly affected in some SCAs. Furthermore, other parts of the nervous system, such as the spinal cord, basal ganglia and pontine nuclei in the brainstem, can be involved. As there is currently no treatment to slow or halt SCAs (many SCAs lead to premature death), the clinical care of patients with SCA focuses on managing the symptoms through physiotherapy, occupational therapy and speech therapy. Intense research has greatly expanded our understanding of the pathobiology of many SCAs, revealing that they occur via interrelated mechanisms (including proteotoxicity, RNA toxicity and ion channel dysfunction), and has led to the identification of new targets for treatment development. However, the development of effective therapies is hampered by the heterogeneity of the SCAs; specific therapeutic approaches may be required for each disease.
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Chopra R, Wasserman AH, Pulst SM, De Zeeuw CI, Shakkottai VG. Protein kinase C activity is a protective modifier of Purkinje neuron degeneration in cerebellar ataxia. Hum Mol Genet 2019; 27:1396-1410. [PMID: 29432535 DOI: 10.1093/hmg/ddy050] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 02/05/2018] [Indexed: 11/13/2022] Open
Abstract
Among the many types of neurons expressing protein kinase C (PKC) enzymes, cerebellar Purkinje neurons are particularly reliant on appropriate PKC activity for maintaining homeostasis. The importance of PKC enzymes in Purkinje neuron health is apparent as mutations in PRKCG (encoding PKCγ) cause cerebellar ataxia. PRKCG has also been identified as an important node in ataxia gene networks more broadly, but the functional role of PKC in other forms of ataxia remains unexplored, and the mechanisms by which PKC isozymes regulate Purkinje neuron health are not well understood. Here, we investigated how PKC activity influences neurodegeneration in inherited ataxia. Using mouse models of spinocerebellar ataxia type 1 (SCA1) and 2 (SCA2) we identify an increase in PKC-mediated substrate phosphorylation in two different forms of inherited cerebellar ataxia. Normalizing PKC substrate phosphorylation in SCA1 and SCA2 mice accelerates degeneration, suggesting that the increased activity observed in these models is neuroprotective. We also find that increased phosphorylation of PKC targets limits Purkinje neuron membrane excitability, suggesting that PKC activity may support Purkinje neuron health by moderating excitability. These data suggest a functional role for PKC enzymes in ataxia gene networks, and demonstrate that increased PKC activity is a protective modifier of degeneration in inherited cerebellar ataxia.
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Affiliation(s)
- Ravi Chopra
- Medical Scientist Training Program, University of Michigan Medical School, Ann Arbor, MI 48109, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA.,Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Aaron H Wasserman
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Stefan M Pulst
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
| | - Chris I De Zeeuw
- Netherlands Institute for Neuroscience, Amsterdam 1105 CA, The Netherlands.,Department of Neuroscience, Erasmus MC, Rotterdam 3015 GE, The Netherlands
| | - Vikram G Shakkottai
- Department of Neurology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.,Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
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36
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Corbin-Leftwich A, Small HE, Robinson HH, Villalba-Galea CA, Boland LM. A Xenopus oocyte model system to study action potentials. J Gen Physiol 2018; 150:1583-1593. [PMID: 30266757 PMCID: PMC6219683 DOI: 10.1085/jgp.201812146] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 09/10/2018] [Indexed: 12/23/2022] Open
Abstract
Voltage-gated Na+ and K+ channels are known to underlie the temporal characteristics of action potentials. Corbin-Leftwich et al. establish reliable action potential recordings from Xenopus oocytes coexpressing these channels and show how different K+ channel subtypes can modulate excitability. Action potentials (APs) are the functional units of fast electrical signaling in excitable cells. The upstroke and downstroke of an AP is generated by the competing and asynchronous action of Na+- and K+-selective voltage-gated conductances. Although a mixture of voltage-gated channels has been long recognized to contribute to the generation and temporal characteristics of the AP, understanding how each of these proteins function and are regulated during electrical signaling remains the subject of intense research. AP properties vary among different cellular types because of the expression diversity, subcellular location, and modulation of ion channels. These complexities, in addition to the functional coupling of these proteins by membrane potential, make it challenging to understand the roles of different channels in initiating and “temporally shaping” the AP. Here, to address this problem, we focus our efforts on finding conditions that allow reliable AP recordings from Xenopus laevis oocytes coexpressing Na+ and K+ channels. As a proof of principle, we show how the expression of a variety of K+ channel subtypes can modulate excitability in this minimal model system. This approach raises the prospect of studies on the modulation of APs by pharmacological or biological means with a controlled background of Na+ and K+ channel expression.
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Affiliation(s)
| | - Hannah E Small
- Department of Biology, University of Richmond, Richmond, VA
| | | | - Carlos A Villalba-Galea
- Department of Physiology and Biophysics, Virginia Commonwealth University, School of Medicine, Richmond, VA .,Department of Physiology and Pharmacology, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA
| | - Linda M Boland
- Department of Biology, University of Richmond, Richmond, VA
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Lieberman AP, Shakkottai VG, Albin RL. Polyglutamine Repeats in Neurodegenerative Diseases. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2018; 14:1-27. [PMID: 30089230 DOI: 10.1146/annurev-pathmechdis-012418-012857] [Citation(s) in RCA: 164] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Among the age-dependent protein aggregation disorders, nine neurodegenerative diseases are caused by expansions of CAG repeats encoding polyglutamine (polyQ) tracts. We review the clinical, pathological, and biological features of these inherited disorders. We discuss insights into pathogenesis gleaned from studies of model systems and patients, highlighting work that informs efforts to develop effective therapies. An important conclusion from these analyses is that expanded CAG/polyQ domains are the primary drivers of neurodegeneration, with the biology of carrier proteins influencing disease-specific manifestations. Additionally, it has become apparent that CAG/polyQ repeat expansions produce neurodegeneration via multiple downstream mechanisms, involving both gain- and loss-of-function effects. This conclusion indicates that the likelihood of developing effective therapies targeting single nodes is reduced. The evaluation of treatments for premanifest disease will likely require new investigational approaches. We highlight the opportunities and challenges underlying ongoing work and provide recommendations related to the development of symptomatic and disease-modifying therapies and biomarkers that could inform future research.
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Affiliation(s)
- Andrew P Lieberman
- Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA;
| | - Vikram G Shakkottai
- Department of Neurology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA; , .,Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
| | - Roger L Albin
- Department of Neurology, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA; , .,Neurology Service and the Geriatric Research, Education, and Clinical Center (GRECC), VA Ann Arbor Healthcare System, Ann Arbor, Michigan 48105, USA
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38
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McLoughlin HS, Moore LR, Chopra R, Komlo R, McKenzie M, Blumenstein KG, Zhao H, Kordasiewicz HB, Shakkottai VG, Paulson HL. Oligonucleotide therapy mitigates disease in spinocerebellar ataxia type 3 mice. Ann Neurol 2018; 84:64-77. [PMID: 29908063 PMCID: PMC6119475 DOI: 10.1002/ana.25264] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/16/2018] [Accepted: 05/21/2018] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is the most common dominantly inherited ataxia. Despite advances in understanding this CAG repeat/polyglutamine expansion disease, there are still no therapies to alter its progressive fatal course. Here, we investigate whether an antisense oligonucleotide (ASO) targeting the SCA3 disease gene, ATXN3, can prevent molecular, neuropathological, electrophysiological, and behavioral features of the disease in a mouse model of SCA3. METHODS The top ATXN3-targeting ASO from an in vivo screen was injected intracerebroventricularly into early symptomatic transgenic SCA3 mice that express the full human disease gene and recapitulate key disease features. Following a single ASO treatment at 8 weeks of age, mice were evaluated longitudinally for ATXN3 suppression and rescue of disease-associated pathological changes. Mice receiving an additional repeat injection at 21 weeks were evaluated longitudinally up to 29 weeks for motor performance. RESULTS The ATXN3-targeting ASO achieved sustained reduction of polyglutamine-expanded ATXN3 up to 8 weeks after treatment and prevented oligomeric and nuclear accumulation of ATXN3 up to at least 14 weeks after treatment. Longitudinal ASO therapy rescued motor impairment in SCA3 mice, and this rescue was associated with a recovery of defects in Purkinje neuron firing frequency and afterhyperpolarization. INTERPRETATION This preclinical study established efficacy of ATXN3-targeted ASOs as a disease-modifying therapeutic strategy for SCA3. These results support further efforts to develop ASOs for human clinical trials in this polyglutamine disease as well as in other dominantly inherited disorders caused by toxic gain of function. Ann Neurol 2018;83:64-77.
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Affiliation(s)
| | - Lauren R. Moore
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109-2200, USA
| | - Ravi Chopra
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109-2200, USA
| | - Robert Komlo
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109-2200, USA
| | - Megan McKenzie
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109-2200, USA
| | - Kate G. Blumenstein
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109-2200, USA
| | - Hien Zhao
- Ionis Pharmaceuticals, Carlsbad, CA 92008, USA
| | | | | | - Henry L. Paulson
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109-2200, USA
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Dendritic potassium channel dysfunction may contribute to dendrite degeneration in spinocerebellar ataxia type 1. PLoS One 2018; 13:e0198040. [PMID: 29847609 PMCID: PMC5976172 DOI: 10.1371/journal.pone.0198040] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 05/11/2018] [Indexed: 12/14/2022] Open
Abstract
Purkinje neuron dendritic degeneration precedes cell loss in cerebellar ataxia, but the basis for dendritic vulnerability in ataxia remains poorly understood. Recent work has suggested that potassium (K+) channel dysfunction and consequent spiking abnormalities contribute to Purkinje neuron degeneration, but little attention has been paid to how K+ channel dysfunction impacts dendritic excitability and the role this may play in the degenerative process. We examined the relationship between K+ channel dysfunction, dendritic excitability and dendritic degeneration in spinocerebellar ataxia type 1 (SCA1). Examination of published RNA sequencing data from SCA1 mice revealed reduced expression of several K+ channels that are important regulators of excitability in Purkinje neuron dendrites. Patch clamp recordings in Purkinje neurons from SCA1 mice identified increased dendritic excitability in the form of enhanced back-propagation of action potentials and an increased propensity to produce dendritic calcium spikes. Dendritic excitability could be rescued by restoring expression of large-conductance calcium-activated potassium (BK) channels and activating other K+ channels with baclofen. Importantly, this treatment combination improves motor performance and mitigates dendritic degeneration in SCA1 mice. These results suggest that reduced expression of K+ channels results in persistently increased dendritic excitability at all stages of disease in SCA1, which in turn may contribute to the dendritic degeneration that precedes cell loss.
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40
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Chen C, Fang X, Sun S. Diagnosis of polyglutamine spinocerebellar ataxias by polymerase chain reaction amplification and Sanger sequencing. Mol Med Rep 2018; 18:1037-1042. [PMID: 29845242 DOI: 10.3892/mmr.2018.9043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 05/09/2018] [Indexed: 11/06/2022] Open
Abstract
Spinocerebellar ataxia (SCA) is a group of genetic diseases of the nervous system with genetic and clinical heterogeneity. SCA is often caused by an expanded CAG repeat sequence in the encoding protein. Genetic testing is necessary to diagnose and classify the types of SCA. Next‑generation DNA sequencing usually generates a high error rate for insertion or deletion mutations, so it is unhelpful for classifying the types of SCA. In the present study, a Chinese SCA pedigree was preliminarily diagnosed with SCA1 using polymerase chain reaction (PCR) amplification. The propositus and his three younger siblings were diagnosed with SCA1 as a result of the identification of the length of the expanded CAG repeat sequence in the ATXN1 gene performed using Sanger sequencing. The current study presents a convenient and efficient method to identify causative mutations for polyglutamine SCA using PCR amplification followed by Sanger sequencing.
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Affiliation(s)
- Changqiang Chen
- Department of Laboratory Medicine, Ruijin Hospital North, Shanghai Jiao Tong University School of Medicine, Shanghai 201801, P.R. China
| | - Xuqian Fang
- Department of Laboratory Medicine, Ruijin Hospital North, Shanghai Jiao Tong University School of Medicine, Shanghai 201801, P.R. China
| | - Shunchang Sun
- Department of Laboratory Medicine, Ruijin Hospital North, Shanghai Jiao Tong University School of Medicine, Shanghai 201801, P.R. China
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41
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Bushart DD, Shakkottai VG. Ion channel dysfunction in cerebellar ataxia. Neurosci Lett 2018; 688:41-48. [PMID: 29421541 DOI: 10.1016/j.neulet.2018.02.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Accepted: 02/02/2018] [Indexed: 12/31/2022]
Abstract
Cerebellar ataxias constitute a heterogeneous group of disorders that result in impaired speech, uncoordinated limb movements, and impaired balance, often ultimately resulting in wheelchair confinement. Motor dysfunction in ataxia can be attributed to dysfunction and degeneration of neurons in the cerebellum and its associated pathways. Recent work has suggested the importance of cerebellar neuronal dysfunction resulting from mutations in specific ion-channels that regulate membrane excitability in the pathogenesis of cerebellar ataxia in humans. Importantly, even in ataxias not directly due to ion-channel mutations, transcriptional changes resulting in ion-channel dysfunction are tied to motor dysfunction and degeneration in models of disease. In this review, we describe the role that ion-channel dysfunction plays in a variety of cerebellar ataxias, and postulate that a potential therapeutic strategy that targets specific ion-channels exists for cerebellar ataxia.
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Affiliation(s)
- David D Bushart
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor MI, USA
| | - Vikram G Shakkottai
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor MI, USA; Department of Neurology, University of Michigan, 4009 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI, 48109, USA.
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42
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Bushart DD, Chopra R, Singh V, Murphy GG, Wulff H, Shakkottai VG. Targeting potassium channels to treat cerebellar ataxia. Ann Clin Transl Neurol 2018; 5:297-314. [PMID: 29560375 PMCID: PMC5846455 DOI: 10.1002/acn3.527] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 12/14/2017] [Accepted: 12/18/2017] [Indexed: 12/22/2022] Open
Abstract
Objective Purkinje neuron dysfunction is associated with cerebellar ataxia. In a mouse model of spinocerebellar ataxia type 1 (SCA1), reduced potassium channel function contributes to altered membrane excitability resulting in impaired Purkinje neuron spiking. We sought to determine the relationship between altered membrane excitability and motor dysfunction in SCA1 mice. Methods Patch-clamp recordings in acute cerebellar slices and motor phenotype testing were used to identify pharmacologic agents which improve Purkinje neuron physiology and motor performance in SCA1 mice. Additionally, we retrospectively reviewed records of patients with SCA1 and other autosomal-dominant SCAs with prominent Purkinje neuron involvement to determine whether currently approved potassium channel activators were tolerated. Results Activating calcium-activated and subthreshold-activated potassium channels improved Purkinje neuron spiking impairment in SCA1 mice (P < 0.05). Additionally, dendritic hyperexcitability was improved by activating subthreshold-activated potassium channels but not calcium-activated potassium channels (P < 0.01). Improving spiking and dendritic hyperexcitability through a combination of chlorzoxazone and baclofen produced sustained improvements in motor dysfunction in SCA1 mice (P < 0.01). Retrospective review of SCA patient records suggests that co-treatment with chlorzoxazone and baclofen is tolerated. Interpretation Targeting both altered spiking and dendritic membrane excitability is associated with sustained improvements in motor performance in SCA1 mice, while targeting altered spiking alone produces only short-term improvements in motor dysfunction. Potassium channel activators currently in clinical use are well tolerated and may provide benefit in SCA patients. Future clinical trials with potassium channel activators are warranted in cerebellar ataxia.
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Affiliation(s)
- David D Bushart
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor Michigan
| | - Ravi Chopra
- Department of Neurology University of Michigan Ann Arbor Michigan
| | - Vikrant Singh
- Department of Pharmacology University of California Davis California
| | - Geoffrey G Murphy
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor Michigan.,Molecular & Behavioral Neuroscience Institute University of Michigan Ann Arbor Michigan
| | - Heike Wulff
- Department of Pharmacology University of California Davis California
| | - Vikram G Shakkottai
- Department of Molecular & Integrative Physiology University of Michigan Ann Arbor Michigan.,Department of Neurology University of Michigan Ann Arbor Michigan
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43
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Abstract
The dominantly inherited spinocerebellar ataxias (SCAs) are a large and diverse group of neurodegenerative diseases. The most prevalent SCAs (SCA1, SCA2, SCA3, SCA6 and SCA7) are caused by expansion of a glutamine-encoding CAG repeat in the affected gene. These SCAs represent a substantial portion of the polyglutamine neurodegenerative disorders and provide insight into this class of diseases as a whole. Recent years have seen considerable progress in deciphering the clinical, pathological, physiological and molecular aspects of the polyglutamine SCAs, with these advances establishing a solid base from which to pursue potential therapeutic approaches.
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