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Dubey AA, Krygier M, Szulc NA, Rutkowska K, Kosińska J, Pollak A, Rydzanicz M, Kmieć T, Mazurkiewicz-Bełdzińska M, Pokrzywa W, Płoski R. A novel de novo FEM1C variant is linked to neurodevelopmental disorder with absent speech, pyramidal signs and limb ataxia. Hum Mol Genet 2023; 32:1152-1161. [PMID: 36336956 PMCID: PMC10026218 DOI: 10.1093/hmg/ddac276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 10/26/2022] [Accepted: 10/29/2022] [Indexed: 11/09/2022] Open
Abstract
The principal component of the protein homeostasis network is the ubiquitin-proteasome system. Ubiquitination is mediated by an enzymatic cascade involving, i.e. E3 ubiquitin ligases, many of which belong to the cullin-RING ligases family. Genetic defects in the ubiquitin-proteasome system components, including cullin-RING ligases, are known causes of neurodevelopmental disorders. Using exome sequencing to diagnose a pediatric patient with developmental delay, pyramidal signs and limb ataxia, we identified a de novo missense variant c.376G>C; p.(Asp126His) in the FEM1C gene encoding a cullin-RING ligase substrate receptor. This variant alters a conserved amino acid located within a highly constrained coding region and is predicted as pathogenic by most in silico tools. In addition, a de novo FEM1C mutation of the same residue p.(Asp126Val) was associated with an undiagnosed developmental disorder, and the relevant variant (FEM1CAsp126Ala) was found to be functionally compromised in vitro. Our computational analysis showed that FEM1CAsp126His hampers protein substrate binding. To further assess its pathogenicity, we used the nematode Caenorhabditis elegans. We found that the FEM-1Asp133His animals (expressing variant homologous to the FEM1C p.(Asp126Val)) had normal muscle architecture yet impaired mobility. Mutant worms were sensitive to the acetylcholinesterase inhibitor aldicarb but not levamisole (acetylcholine receptor agonist), showing that their disabled locomotion is caused by synaptic abnormalities and not muscle dysfunction. In conclusion, we provide the first evidence from an animal model suggesting that a mutation in the evolutionarily conserved FEM1C Asp126 position causes a neurodevelopmental disorder in humans.
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Affiliation(s)
- Abhishek Anil Dubey
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, 02-109 Warsaw, Poland
| | - Magdalena Krygier
- Department of Developmental Neurology, Medical University of Gdańsk, 80-952 Gdańsk, Poland
| | - Natalia A Szulc
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, 02-109 Warsaw, Poland
| | - Karolina Rutkowska
- Department of Medical Genetics, Medical University of Warsaw, 02-106 Warsaw, Poland
| | - Joanna Kosińska
- Department of Medical Genetics, Medical University of Warsaw, 02-106 Warsaw, Poland
| | - Agnieszka Pollak
- Department of Medical Genetics, Medical University of Warsaw, 02-106 Warsaw, Poland
| | - Małgorzata Rydzanicz
- Department of Medical Genetics, Medical University of Warsaw, 02-106 Warsaw, Poland
| | - Tomasz Kmieć
- Department of Neurology and Epileptology, The Children's Memorial Health Institute, 04-730 Warsaw, Poland
| | | | - Wojciech Pokrzywa
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, 02-109 Warsaw, Poland
| | - Rafał Płoski
- Department of Medical Genetics, Medical University of Warsaw, 02-106 Warsaw, Poland
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2
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Benarroch E. What Is the Role of Norepinephrine in Cerebellar Modulation and Stress-Induced Episodic Ataxia? Neurology 2023; 100:383-386. [PMID: 36806456 PMCID: PMC9984211 DOI: 10.1212/wnl.0000000000206882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 12/09/2022] [Indexed: 02/22/2023] Open
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3
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Martinez-Rojas VA, Juarez-Hernandez LJ, Musio C. Ion channels and neuronal excitability in polyglutamine neurodegenerative diseases. Biomol Concepts 2022; 13:183-199. [DOI: 10.1515/bmc-2022-0018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 03/14/2022] [Indexed: 11/15/2022] Open
Abstract
Abstract
Polyglutamine (polyQ) diseases are a family composed of nine neurodegenerative inherited disorders (NDDs) caused by pathological expansions of cytosine-adenine-guanine (CAG) trinucleotide repeats which encode a polyQ tract in the corresponding proteins. CAG polyQ repeat expansions produce neurodegeneration via multiple downstream mechanisms; among those the neuronal activity underlying the ion channels is affected directly by specific channelopathies or indirectly by secondary dysregulation. In both cases, the altered excitability underlies to gain- or loss-of-function pathological effects. Here we summarize the repertoire of ion channels in polyQ NDDs emphasizing the biophysical features of neuronal excitability and their pathogenic role. The aim of this review is to point out the value of a deeper understanding of those functional mechanisms and processes as crucial elements for the designing and targeting of novel therapeutic avenues.
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Affiliation(s)
- Vladimir A. Martinez-Rojas
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) , Via Sommarive 18 , 38123 Trento , Italy
| | - Leon J. Juarez-Hernandez
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) , Via Sommarive 18 , 38123 Trento , Italy
| | - Carlo Musio
- Institute of Biophysics (IBF), Trento Unit, National Research Council (CNR) , Via Sommarive 18 , 38123 Trento , Italy
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4
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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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5
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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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6
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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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7
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Rosini F, Pretegiani E, Battisti C, Dotti MT, Federico A, Rufa A. Eye movement changes in autosomal dominant spinocerebellar ataxias. Neurol Sci 2020; 41:1719-1734. [PMID: 32130555 DOI: 10.1007/s10072-020-04318-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Accepted: 02/24/2020] [Indexed: 12/15/2022]
Abstract
Oculomotor abnormalities are common findings in spinocerebellar ataxias (SCAs), a clinically heterogeneous group of neurodegenerative disorders with an autosomal dominant pattern of inheritance. Usually, cerebellar impairment accounts for most of the eye movement changes encountered; as the disease progresses, the involvement of extracerebellar structures typically seen in later stages may modify the oculomotor progression. However, ocular movement changes are rarely specific. In this regard, some important exceptions include the prominent slowing of horizontal eye movements in SCA2 and, to a lesser extent, in SCA3, SCA4, and SCA28, or the executive deficit in SCA2 and SCA17. Here, we report the eye movement abnormalities and neurological pictures of SCAs through a review of the literature. Genetic and neuropathological/neuroimaging aspects are also briefly discussed. Overall, the findings reported indicate that oculomotor analysis could be of help in differential diagnosis among SCAs and contribute to clarify the role of brain structures, particularly the cerebellum, in oculomotor control.
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Affiliation(s)
- Francesca Rosini
- Department of Medicine Surgery and Neuroscience, Eye Tracking& Visual Application Lab EVALAB, Neurology and Neurometabolic Unit, University of Siena, Viale Bracci 2, 53100, Siena, Italy
| | - Elena Pretegiani
- Department of Medicine Surgery and Neuroscience, Eye Tracking& Visual Application Lab EVALAB, Neurology and Neurometabolic Unit, University of Siena, Viale Bracci 2, 53100, Siena, Italy
| | - Carla Battisti
- Department of Medicine, Surgery and Neuroscience, Neurology and Neurometabolic Unit, University of Siena, Siena, Italy
| | - Maria Teresa Dotti
- Department of Medicine, Surgery and Neuroscience, Neurology and Neurometabolic Unit, University of Siena, Siena, Italy
| | - Antonio Federico
- Department of Medicine, Surgery and Neuroscience, Neurology and Neurometabolic Unit, University of Siena, Siena, Italy
| | - Alessandra Rufa
- Department of Medicine Surgery and Neuroscience, Eye Tracking& Visual Application Lab EVALAB, Neurology and Neurometabolic Unit, University of Siena, Viale Bracci 2, 53100, Siena, Italy.
- Department of Medicine, Surgery and Neuroscience, Neurology and Neurometabolic Unit, University of Siena, Siena, Italy.
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8
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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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9
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Groth CL, Berman BD. Spinocerebellar Ataxia 27: A Review and Characterization of an Evolving Phenotype. Tremor Other Hyperkinet Mov (N Y) 2018; 8:534. [PMID: 29416937 PMCID: PMC5801325 DOI: 10.7916/d80s0zjq] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 01/08/2018] [Indexed: 12/23/2022] Open
Abstract
Background Spinocerebellar ataxia (SCA) is an uncommon form of progressive cerebellar ataxia with multiple genetic causes and marked variability in phenotypic expression even across patients with identical genetic abnormalities. SCA27 is a recently identified SCA caused by mutations in the Fibroblast Growth Factor 14 gene, with a phenotypic expression that is only beginning to be fully appreciated. We report here a case of a 70-year-old male who presented with slowly worsening tremor and gait instability that began in his early adulthood along with additional features of parkinsonism on examination. Work-up revealed a novel pathogenic mutation in the Fibroblast Growth Factor 14 gene, and symptoms improved with amantadine and levodopa. We also provide a review of the literature in order to better characterize the phenotypic expression of this uncommon condition. Methods Case report and review of the literature. Results Review of the literature revealed a total of 32 previously reported clinical cases of SCA27. Including our case, we found that early-onset tremor (12.1 ± 10.5 years) was present in 95.8%, while gait ataxia tended to present later in life (23.7 ± 16.7 years) and was accompanied by limb ataxia, dysarthria, and nystagmus. Other features of SCA27 that may distinguish it from other SCAs include the potential for episodic ataxia, accompanying psychiatric symptoms, and cognitive impairment. Discussion Testing for SCA27 should be considered in individuals with ataxia who report tremor as an initial or early symptom, as well as those with additional findings of episodic ataxia, neuropsychiatric symptoms, or parkinsonism.
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Affiliation(s)
- Christopher L. Groth
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Brian D. Berman
- Department of Neurology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
- Neurology Section, Denver VA Medical Center, Denver, CO, USA
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10
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Abstract
Spinocerebellar ataxias (SCAs) are a genetically diverse group of dominantly inherited disorders that share clinical features that result from dysfunction and degeneration of the cerebellum and its associated pathways. Although nearly 40 genes are currently recognized to result in SCA, shared mechanisms for disease pathogenesis exist among subsets of the SCAs. The most common SCAs result from a glutamine-encoding CAG repeat in the respective disease genes. This chapter discusses the varied genetic etiology of SCA and attempts to categorize these disorders based on shared mechanisms of disease. We also summarize evaluation and management for the SCAs.
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Affiliation(s)
- Andrew Mundwiler
- Department of Neurosciences, Spectrum Health, Grand Rapids, MI, United States; College of Human Medicine, Michigan State University, Grand Rapids, MI, United States
| | - Vikram G Shakkottai
- Department of Neurology, University of Michigan, Ann Arbor, MI, United States.
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11
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Pablo JL, Pitt GS. Fibroblast Growth Factor Homologous Factors: New Roles in Neuronal Health and Disease. Neuroscientist 2014; 22:19-25. [PMID: 25492945 DOI: 10.1177/1073858414562217] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Fibroblast growth factor homologous factors (FHFs) are a noncanonical subset of intracellular fibroblast growth factors that have been implicated in a variety of neurobiological processes and in disease. They are most prominently regulators of voltage-gated Na(+) channels (NaVs). In this review, we discuss new insights into how FHFs modulate NaVs. This is followed by a summary of a growing body of evidence that FHFs operate in much broader fashion. Finally, we highlight unknown aspects of FHF function as areas of future interest.
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Affiliation(s)
- Juan L Pablo
- Ion Channel Research Unit, Duke University Medical Center, Durham, NC, USA Department of Neurobiology, Duke University Medical Center, Durham, NC, USA
| | - Geoffrey S Pitt
- Ion Channel Research Unit, Duke University Medical Center, Durham, NC, USA Department of Neurobiology, Duke University Medical Center, Durham, NC, USA Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, NC, USA
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12
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Abstract
The autosomal dominant spinocerebellar ataxias are a diverse and clinically heterogeneous group of disorders characterized by degeneration and dysfunction of the cerebellum and its associated pathways. Clinical and diagnostic evaluation can be challenging because of phenotypic overlap among causes, and a stratified and systematic approach is essential. Recent advances include the identification of additional genes causing dominant genetic ataxia, a better understanding of cellular pathogenesis in several disorders, the generation of new disease models that may stimulate development of new therapies, and the use of new DNA sequencing technologies, including whole-exome sequencing, to improve diagnosis.
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13
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Yan H, Pablo JL, Pitt GS. FGF14 regulates presynaptic Ca2+ channels and synaptic transmission. Cell Rep 2013; 4:66-75. [PMID: 23831029 DOI: 10.1016/j.celrep.2013.06.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 05/13/2013] [Accepted: 06/07/2013] [Indexed: 10/26/2022] Open
Abstract
Fibroblast growth factor homologous factors (FHFs) are not growth factors, but instead bind to voltage-gated Na+ channels (NaV) and regulate their function. Mutations in FGF14, an FHF that is the locus for spinocerebellar ataxia 27 (SCA27), are believed to be pathogenic because of a dominant-negative reduction of NaV currents in cerebellar granule cells. Here, we demonstrate that FGF14 also regulates members of the presynaptic CaV2 Ca2+ channel family. Knockdown of FGF14 in granule cells reduced Ca2+ currents and diminished vesicular recycling, a marker for presynaptic Ca2+ influx. As a consequence, excitatory postsynaptic currents (EPSCs) at the granule cell to Purkinje cell synapse were markedly diminished. Expression of the SCA27-causing FGF14 mutant in granule cells exerted a dominant-negative reduction in Ca2+ currents, vesicular recycling, and the resultant EPSCs in Purkinje cells. Thus, FHFs are multimodal, regulating several discrete neuronal signaling events. SCA27 most likely results at least in part from dysregulation of Ca2+ channel function.
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Affiliation(s)
- Haidun Yan
- Division of Cardiology, Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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14
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Dougherty SE, Reeves JL, Lesort M, Detloff PJ, Cowell RM. Purkinje cell dysfunction and loss in a knock-in mouse model of Huntington disease. Exp Neurol 2012. [PMID: 23195593 DOI: 10.1016/j.expneurol.2012.11.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Huntington Disease (HD) is an autosomal dominant neurological disorder characterized by motor, psychiatric and cognitive disturbances. Recent evidence indicates that the viability and function of cerebellar Purkinje cells (PCs) are compromised in an aggressive mouse model of HD. Here we investigate whether this is also the case in the HdhQ200 knock-in mouse model of HD. Using quantitative-real time-PCR and immunofluorescence, we observed a loss of the PC marker and calcium buffer calbindin in 50week-old symptomatic mice. Reductions were also observed in parvalbumin and glutamic acid decarboxylase protein expression, most markedly in the molecular cell layer. Stereological analysis revealed an overall reduction in the PC population in HdhQ200/Q200 mice by nearly 40%, and loose patch electrophysiology of remaining PCs indicated a reduction in firing rate in HD mice compared to control littermates. Taken together, these data demonstrate that PC survival and function are compromised in a mouse model of adult-onset HD and suggest that further experiments should investigate the contribution of PC death and dysfunction to HD-associated motor impairment.
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Affiliation(s)
- S E Dougherty
- Neuroscience Graduate Program, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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15
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Abstract
The past 25 years have seen enormous progress in the deciphering of the genetic and molecular basis of ataxias, resulting in improved understanding of their pathogenesis. The most significant milestones during this period were the cloning of the genes associated with the common spinocerebellar ataxias, ataxia telangiectasia, and Friedreich ataxia. To date, the causative mutations of more than 30 spinocerebellar ataxias and 20 recessive ataxias have been identified. In addition, there are numerous acquired ataxias with defined molecular causes, so that the entire number of distinct ataxia disorders exceeds 50 and possibly approaches 100. Despite this enormous heterogeneity, a few recurrent pathophysiological themes stand out. These include protein aggregation, failure of protein homeostasis, perturbations in ion channel function, defects in DNA repair, and mitochondrial dysfunction. The clinical phenotypes of the most common ataxia disorders have been firmly established, and their natural history is being studied in ongoing large observational trials. Effective therapies for ataxias are still lacking. However, novel drug targets are under investigation, and it is expected that there will be an increasing number of therapeutic trials in ataxia.
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16
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Shabani M, Hosseinmardi N, Haghani M, Shaibani V, Janahmadi M. Maternal exposure to the CB1 cannabinoid agonist WIN 55212-2 produces robust changes in motor function and intrinsic electrophysiological properties of cerebellar Purkinje neurons in rat offspring. Neuroscience 2010; 172:139-52. [PMID: 20969930 DOI: 10.1016/j.neuroscience.2010.10.031] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 10/07/2010] [Accepted: 10/09/2010] [Indexed: 01/18/2023]
Abstract
The cerebellum, which controls coordinated and rapid movements, is a potential target for the deleterious effects of drugs of abuse including cannabis (i.e. marijuana, cannabinoids). Prenatal exposure to cannabinoids has been documented to cause abnormalities in motor and cognitive development, but the exact mechanism of this effect at the cellular level has not been fully elucidated. Previous studies indicate that cannabinoids are capable of modulating synaptic neurotransmission. In addition to altering synaptic activity, cannabinoid exposure may also change intrinsic neuronal properties. In the present study several different approaches including behavioral assays, extracellular field potential recordings and whole-cell patch clamp recordings, were used to address whether maternal exposure to the CB1 cannabinoid receptor agonist WIN 55-212-2 (WIN) affects the intrinsic electrophysiological properties of Purkinje neurons. WIN treatment of pregnant rats produced a significant decrease in the rearing frequency, total distance moved and mobility of the offspring, but significantly increased the time of the righting reflex, the grooming frequency and immobility. Neuromotor function, as assessed in the grip test and balance beam test, was also significantly impaired in prenatally WIN-treated group. Prenatal exposure to WIN increased the amplitude of population spikes (PS) recorded from the cerebellar Purkinje cell layer of offspring following synaptic blockage. WIN treatment of pregnant rats also profoundly affected the intrinsic properties of Purkinje neurons in offspring. This treatment increased the firing regularity, firing frequency, amplitude of afterhyperpolarization (AHP), the peak amplitude of action potential and the first spike latency, but decreased significantly the time to peak and duration of action potentials, the instantaneous firing frequency, the rate of rebound action potential and the voltage "sag" ratio. These results raise the possibility that maternal exposure to cannabinoids may profoundly affect the intrinsic membrane properties of cerebellar Purkinje neurons of offspring by altering the membrane excitability through modulation of intrinsic ion channels.
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Affiliation(s)
- M Shabani
- Neuroscience Research Centre and Department of Physiology, Medical School, Shahid Beheshti University of Medical Sciences, Evin, Tehran, Islamic Republic of Iran
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Rajakulendran S, Schorge S, Kullmann DM, Hanna MG. Dysfunction of the Ca(V)2.1 calcium channel in cerebellar ataxias. F1000 BIOLOGY REPORTS 2010; 2. [PMID: 20948794 PMCID: PMC2948357 DOI: 10.3410/b2-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mutations in the CACNA1A gene are associated with episodic ataxia type 2 (EA2) and spinocerebellar ataxia type 6 (SCA6). CACNA1A encodes the α-subunit of the P/Q-type calcium channel or CaV2.1, which is highly enriched in the cerebellum. It is one of the main channels linked to synaptic transmission throughout the human central nervous system. Here, we compare recent advances in the understanding of the genetic changes that underlie EA2 and SCA6 and what these new findings suggest about the mechanism of the disease.
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Affiliation(s)
- Sanjeev Rajakulendran
- MRC Centre for Neuromuscular Diseases, Institute of Neurology, University College London Queen Square, London WC1N 3BG UK
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18
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Elrick MJ, Pacheco CD, Yu T, Dadgar N, Shakkottai VG, Ware C, Paulson HL, Lieberman AP. Conditional Niemann-Pick C mice demonstrate cell autonomous Purkinje cell neurodegeneration. Hum Mol Genet 2009; 19:837-47. [PMID: 20007718 DOI: 10.1093/hmg/ddp552] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Pathways regulating neuronal vulnerability are poorly understood, yet are central to identifying therapeutic targets for degenerative neurological diseases. Here, we characterize mechanisms underlying neurodegeneration in Niemann-Pick type C (NPC) disease, a lysosomal storage disorder characterized by impaired cholesterol trafficking. To date, the relative contributions of neuronal and glial defects to neuron loss are poorly defined. Using gene targeting, we generate Npc1 conditional null mutant mice. Deletion of Npc1 in mature cerebellar Purkinje cells leads to an age-dependent impairment in motor tasks, including rotarod and balance beam performance. Surprisingly, these mice did not show the early death or weight loss that are characteristic of global Npc1 null mice, suggesting that Purkinje cell degeneration does not underlie these phenotypes. Histological examination revealed the progressive loss of Purkinje cells in an anterior-to-posterior gradient. This cell autonomous neurodegeneration occurs in a spatiotemporal pattern similar to that of global knockout mice. A subpopulation of Purkinje cells in the posterior cerebellum exhibits marked resistance to cell death despite Npc1 deletion. To explore this selective response, we investigated the electrophysiological properties of vulnerable and susceptible Purkinje cell subpopulations. Unexpectedly, Purkinje cells in both subpopulations displayed no electrophysiological abnormalities prior to degeneration. Our data establish that Npc1 deficiency leads to cell autonomous, selective neurodegeneration and suggest that the ataxic symptoms of NPC disease arise from Purkinje cell death rather than cellular dysfunction.
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Affiliation(s)
- Matthew J Elrick
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109-0605, USA
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