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Rojas F, García RV, González J, Velázquez L, Becerra R, Valenzuela O, San Román B. Identification of saccadic components in spinocerebellar ataxia applying an independent component analysis algorithm. Neurocomputing 2013. [DOI: 10.1016/j.neucom.2012.11.048] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Drost J, Nonis D, Eich F, Leske O, Damrath E, Brunt ER, Lastres-Becker I, Heumann R, Nowock J, Auburger G. Ataxin-2 modulates the levels of Grb2 and SRC but not ras signaling. J Mol Neurosci 2013; 51:68-81. [PMID: 23335000 PMCID: PMC3739869 DOI: 10.1007/s12031-012-9949-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 12/28/2012] [Indexed: 12/13/2022]
Abstract
Ataxin-2 (ATXN2) is implicated mainly in mRNA processing. Some ATXN2 associates with receptor tyrosine kinases (RTK), inhibiting their endocytic internalization through interaction of proline-rich domains (PRD) in ATXN2 with SH3 motifs in Src. Gain of function of ATXN2 leads to neuronal atrophy in the diseases spinocerebellar ataxia type 2 (SCA2) and amyotrophic lateral sclerosis (ALS). Conversely, ATXN2 knockout (KO) mice show hypertrophy and insulin resistance. To elucidate the influence of ATXN2 on trophic regulation, we surveyed interactions of ATXN2 with SH3 motifs from numerous proteins and observed a novel interaction with Grb2. Direct binding in glutathione S-transferase (GST) pull-down assays and coimmunoprecipitation of the endogenous proteins indicated a physiologically relevant association. In SCA2 patient fibroblasts, Grb2 more than Src protein levels were diminished, with an upregulation of both transcripts suggesting enhanced protein turnover. In KO mouse embryonal fibroblasts (MEF), the protein levels of Grb2 and Src were decreased. ATXN2 absence by itself was insufficient to significantly change Grb2-dependent signaling for endogenous Ras levels, Ras-GTP levels, and kinetics as well as MEK1 phosphorylation, suggesting that other factors compensate for proliferation control. In KO tissue with postmitotic neurons, a significant decrease of Src protein levels is prominent rather than Grb2. ATXN2 mutations modulate the levels of several components of the RTK endocytosis complex and may thus contribute to alter cell proliferation as well as translation and growth.
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Affiliation(s)
- Jessica Drost
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - David Nonis
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
- Present Address: Department of Reproductive Medicine, University of California at San Diego, School of Medicine, 9500 Gilman Dr., La Jolla, CA 92093-0633 USA
| | - Florian Eich
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - Oliver Leske
- Department Molecular Neurobiochemistry, Faculty for Chemistry and Biochemistry, Ruhr-University Bochum, Universitätsstraβe 150, 44780 Bochum, Germany
| | - Ewa Damrath
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - Ewout R. Brunt
- Department of Neurology, University Medical Centre Groningen, University of Groningen, Hanzeplein 1, 9713 RB Groningen, The Netherlands
| | - Isabel Lastres-Becker
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
- Present Address: Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols”, and Centro de Investigación en Red en Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Rolf Heumann
- Department Molecular Neurobiochemistry, Faculty for Chemistry and Biochemistry, Ruhr-University Bochum, Universitätsstraβe 150, 44780 Bochum, Germany
| | - Joachim Nowock
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - Georg Auburger
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
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Ramachandran PS, Keiser MS, Davidson BL. Recent advances in RNA interference therapeutics for CNS diseases. Neurotherapeutics 2013; 10:473-85. [PMID: 23589092 PMCID: PMC3701762 DOI: 10.1007/s13311-013-0183-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Over the last decade, RNA interference technology has shown therapeutic promise in rodent models of dominantly inherited brain diseases, including those caused by polyglutamine repeat expansions in the coding region of the affected gene. For some of these diseases, proof-of concept studies in model organisms have transitioned to safety testing in larger animal models, such as the nonhuman primate. Here, we review recent progress on RNA interference-based therapies in various model systems. We also highlight outstanding questions or concerns that have emerged as a result of an improved (and ever advancing) understanding of the technologies employed.
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Affiliation(s)
| | - Megan S. Keiser
- />Interdisciplinary program in Neuroscience, University of Iowa, Iowa City, IA USA
| | - Beverly L. Davidson
- />Interdisciplinary program in Genetics, University of Iowa, Iowa City, IA 52242 USA
- />Interdisciplinary program in Neuroscience, University of Iowa, Iowa City, IA USA
- />Department of Internal Medicine, University of Iowa, Iowa City, USA
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Swarup V, Srivastava AK, Padma MV, Moganty RR. Quantitative Profiling and Identification of Plasma Proteins of Spinocerebellar Ataxia Type 2 Patients. NEURODEGENER DIS 2013; 12:199-206. [DOI: 10.1159/000346585] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 12/17/2012] [Indexed: 11/19/2022] Open
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Rüb U, Schöls L, Paulson H, Auburger G, Kermer P, Jen JC, Seidel K, Korf HW, Deller T. Clinical features, neurogenetics and neuropathology of the polyglutamine spinocerebellar ataxias type 1, 2, 3, 6 and 7. Prog Neurobiol 2013; 104:38-66. [PMID: 23438480 DOI: 10.1016/j.pneurobio.2013.01.001] [Citation(s) in RCA: 234] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 01/22/2013] [Accepted: 01/31/2013] [Indexed: 12/18/2022]
Abstract
The spinocerebellar ataxias type 1 (SCA1), 2 (SCA2), 3 (SCA3), 6 (SCA6) and 7 (SCA7) are genetically defined autosomal dominantly inherited progressive cerebellar ataxias (ADCAs). They belong to the group of CAG-repeat or polyglutamine diseases and share pathologically expanded and meiotically unstable glutamine-encoding CAG-repeats at distinct gene loci encoding elongated polyglutamine stretches in the disease proteins. In recent years, progress has been made in the understanding of the pathogenesis of these currently incurable diseases: Identification of underlying genetic mechanisms made it possible to classify the different ADCAs and to define their clinical and pathological features. Furthermore, advances in molecular biology yielded new insights into the physiological and pathophysiological role of the gene products of SCA1, SCA2, SCA3, SCA6 and SCA7 (i.e. ataxin-1, ataxin-2, ataxin-3, α-1A subunit of the P/Q type voltage-dependent calcium channel, ataxin-7). In the present review we summarize our current knowledge about the polyglutamine ataxias SCA1, SCA2, SCA3, SCA6 and SCA7 and compare their clinical and electrophysiological features, genetic and molecular biological background, as well as their brain pathologies. Furthermore, we provide an overview of the structure, interactions and functions of the different disease proteins. On the basis of these comprehensive data, similarities, differences and possible disease mechanisms are discussed.
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Affiliation(s)
- Udo Rüb
- Dr. Senckenberg Chronomedical Institute, Goethe-University, Theodor-Stern-Kai 7, D-60590 Frankfurt/Main, Germany.
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Xia G, Santostefano K, Hamazaki T, Liu J, Subramony SH, Terada N, Ashizawa T. Generation of human-induced pluripotent stem cells to model spinocerebellar ataxia type 2 in vitro. J Mol Neurosci 2012; 51:237-48. [PMID: 23224816 DOI: 10.1007/s12031-012-9930-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 11/21/2012] [Indexed: 12/27/2022]
Abstract
Spinocerebellar ataxia type 2 (SCA2) is caused by triple nucleotide repeat (CAG) expansion in the coding region of the ATAXN2 gene on chromosome 12, which produces an elongated, toxic polyglutamine tract, leading to Purkinje cell loss. There is currently no effective therapy. One of the main obstacles that hampers therapeutic development is lack of an ideal disease model. In this study, we have generated and characterized SCA2-induced pluripotent stem (iPS) cell lines as an in vitro cell model. Dermal fibroblasts (FBs) were harvested from primary cultures of skin explants obtained from a SCA2 subject and a healthy subject. For reprogramming, hOct4, hSox2, hKlf4, and hc-Myc were transduced to passage-3 FBs by retroviral infection. Both SCA2 iPS and control iPS cells were successfully generated and showed typical stem cell growth patterns with normal karyotype. All iPS cell lines expressed stem cell markers and differentiated in vitro into cells from three embryonic germ layers. Upon in vitro neural differentiation, SCA2 iPS cells showed abnormality in neural rosette formation but successfully differentiated into neural stem cells (NSCs) and subsequent neural cells. SCA2 and normal FBs showed a comparable level of ataxin-2 expression; whereas SCA2 NSCs showed less ataxin-2 expression than normal NSCs and SCA2 FBs. Within the neural lineage, neurons had the most abundant expression of ataxin-2. Time-lapsed neural growth assay indicated terminally differentiated SCA2 neural cells were short-lived compared with control neural cells. The expanded CAG repeats of SCA2 were stable throughout reprogramming and neural differentiation. In conclusion, we have established the first disease-specific human SCA2 iPS cell line. These mutant iPS cells have the potential for neural differentiation. These differentiated neural cells harboring mutations are invaluable for the study of SCA2 pathogenesis and therapeutic drug development.
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Affiliation(s)
- Guangbin Xia
- Department of Neurology, College of Medicine, University of Florida, Gainesville, FL, USA
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Damrath E, Heck MV, Gispert S, Azizov M, Nowock J, Seifried C, Rüb U, Walter M, Auburger G. ATXN2-CAG42 sequesters PABPC1 into insolubility and induces FBXW8 in cerebellum of old ataxic knock-in mice. PLoS Genet 2012; 8:e1002920. [PMID: 22956915 PMCID: PMC3431311 DOI: 10.1371/journal.pgen.1002920] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Accepted: 07/10/2012] [Indexed: 12/15/2022] Open
Abstract
Spinocerebellar Ataxia Type 2 (SCA2) is caused by expansion of a polyglutamine encoding triplet repeat in the human ATXN2 gene beyond (CAG)31. This is thought to mediate toxic gain-of-function by protein aggregation and to affect RNA processing, resulting in degenerative processes affecting preferentially cerebellar neurons. As a faithful animal model, we generated a knock-in mouse replacing the single CAG of murine Atxn2 with CAG42, a frequent patient genotype. This expansion size was inherited stably. The mice showed phenotypes with reduced weight and later motor incoordination. Although brain Atxn2 mRNA became elevated, soluble ATXN2 protein levels diminished over time, which might explain partial loss-of-function effects. Deficits in soluble ATXN2 protein correlated with the appearance of insoluble ATXN2, a progressive feature in cerebellum possibly reflecting toxic gains-of-function. Since in vitro ATXN2 overexpression was known to reduce levels of its protein interactor PABPC1, we studied expansion effects on PABPC1. In cortex, PABPC1 transcript and soluble and insoluble protein levels were increased. In the more vulnerable cerebellum, the progressive insolubility of PABPC1 was accompanied by decreased soluble protein levels, with PABPC1 mRNA showing no compensatory increase. The sequestration of PABPC1 into insolubility by ATXN2 function gains was validated in human cell culture. To understand consequences on mRNA processing, transcriptome profiles at medium and old age in three different tissues were studied and demonstrated a selective induction of Fbxw8 in the old cerebellum. Fbxw8 is encoded next to the Atxn2 locus and was shown in vitro to decrease the level of expanded insoluble ATXN2 protein. In conclusion, our data support the concept that expanded ATXN2 undergoes progressive insolubility and affects PABPC1 by a toxic gain-of-function mechanism with tissue-specific effects, which may be partially alleviated by the induction of FBXW8. Frequent age-associated neurodegenerative disorders like Alzheimer's, Parkinson's, and Lou Gehrig's disease are being elucidated molecularly by studying rare heritable variants. Various hereditary neurodegenerative disorders are caused by polyglutamine expansions in different proteins. In spite of this common pathogenesis and the pathological aggregation of most affected proteins, investigators were puzzled that the pattern of affected neuron population varies and that molecular mechanisms seem different between such disorders. The polyglutamine expansions in the Ataxin-2 (ATXN2) protein are exceptional in view of the lack of aggregate clumps in nuclei of affected Purkinje neurons and well documented alterations of RNA processing in the resulting disorders SCA2 and ALS. Here, as a faithful disease model and to overcome the unavailability of autopsied patient brain tissues, we generated and characterized an ATXN2-CAG42-knock-in mouse mutant. Our data show that the unspecific, chronically present mutation leads to progressive insolubility and to reduced soluble levels of the disease protein and of an interactor protein, which modulates RNA processing. Compensatory efforts are particularly weak in vulnerable tissue. They appear to include the increased degradation of the toxic disease protein by FBXW8. Thus the link between protein and RNA pathology becomes clear, and crucial molecular targets for preventive therapy are identified.
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Affiliation(s)
- Ewa Damrath
- Experimental Neurology, Department of Neurology, Goethe University Medical School, Frankfurt am Main, Germany
| | - Melanie V. Heck
- Experimental Neurology, Department of Neurology, Goethe University Medical School, Frankfurt am Main, Germany
| | - Suzana Gispert
- Experimental Neurology, Department of Neurology, Goethe University Medical School, Frankfurt am Main, Germany
| | - Mekhman Azizov
- Experimental Neurology, Department of Neurology, Goethe University Medical School, Frankfurt am Main, Germany
| | - Joachim Nowock
- Experimental Neurology, Department of Neurology, Goethe University Medical School, Frankfurt am Main, Germany
| | - Carola Seifried
- Experimental Neurology, Department of Neurology, Goethe University Medical School, Frankfurt am Main, Germany
| | - Udo Rüb
- Department of Clinical Neuroanatomy, Dr. Senckenbergisches Chronomedizinisches Institut, Goethe University Medical School, Frankfurt am Main, Germany
| | - Michael Walter
- Institute of Medical Genetics, Eberhard Karls University, Tübingen, Germany
| | - Georg Auburger
- Experimental Neurology, Department of Neurology, Goethe University Medical School, Frankfurt am Main, Germany
- * E-mail:
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Lahut S, Ömür Ö, Uyan Ö, Ağım ZS, Özoğuz A, Parman Y, Deymeer F, Oflazer P, Koç F, Özçelik H, Auburger G, Başak AN. ATXN2 and its neighbouring gene SH2B3 are associated with increased ALS risk in the Turkish population. PLoS One 2012; 7:e42956. [PMID: 22916186 PMCID: PMC3423429 DOI: 10.1371/journal.pone.0042956] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Accepted: 07/16/2012] [Indexed: 01/14/2023] Open
Abstract
Expansions of the polyglutamine (polyQ) domain (≥ 34) in Ataxin-2 (ATXN2) are the primary cause of spinocerebellar ataxia type 2 (SCA2). Recent studies reported that intermediate-length (27-33) expansions increase the risk of Amyotrophic Lateral Sclerosis (ALS) in 1-4% of cases in diverse populations. This study investigates the Turkish population with respect to ALS risk, genotyping 158 sporadic, 78 familial patients and 420 neurologically healthy controls. We re-assessed the effect of ATXN2 expansions and extended the analysis for the first time to cover the ATXN2 locus with 18 Single Nucleotide Polymorphisms (SNPs) and their haplotypes. In accordance with other studies, our results confirmed that 31-32 polyQ repeats in the ATXN2 gene are associated with risk of developing ALS in 1.7% of the Turkish ALS cohort (p=0.0172). Additionally, a significant association of a 136 kb haplotype block across the ATXN2 and SH2B3 genes was found in 19.4% of a subset of our ALS cohort and in 10.1% of the controls (p=0.0057, OR: 2.23). ATXN2 and SH2B3 encode proteins that both interact with growth receptor tyrosine kinases. Our novel observations suggest that genotyping of SNPs at this locus may be useful for the study of ALS risk in a high percentage of individuals and that ATXN2 and SH2B3 variants may interact in modulating the disease pathway.
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Affiliation(s)
- Suna Lahut
- Boğaziçi University, Molecular Biology and Genetics Department, Neurodegeneration Research Laboratory, Istanbul, Turkey
| | - Özgür Ömür
- Boğaziçi University, Molecular Biology and Genetics Department, Neurodegeneration Research Laboratory, Istanbul, Turkey
| | - Özgün Uyan
- Boğaziçi University, Molecular Biology and Genetics Department, Neurodegeneration Research Laboratory, Istanbul, Turkey
| | - Zeynep Sena Ağım
- Boğaziçi University, Molecular Biology and Genetics Department, Neurodegeneration Research Laboratory, Istanbul, Turkey
| | - Aslihan Özoğuz
- Boğaziçi University, Molecular Biology and Genetics Department, Neurodegeneration Research Laboratory, Istanbul, Turkey
| | - Yeşim Parman
- Istanbul University, Istanbul Medical School, Neurology Department, Istanbul, Turkey
| | - Feza Deymeer
- Istanbul University, Istanbul Medical School, Neurology Department, Istanbul, Turkey
| | - Piraye Oflazer
- Istanbul University, Istanbul Medical School, Neurology Department, Istanbul, Turkey
| | - Filiz Koç
- Çukurova University, Medical School, Neurology Department, Adana, Turkey
| | - Hilmi Özçelik
- University of Toronto, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Department of Laboratory Medicine and Pathobiology, Toronto, Ontario, Canada
| | - Georg Auburger
- Goethe University, Experimental Neurology, Frankfurt am Main, Germany
| | - A. Nazlı Başak
- Boğaziçi University, Molecular Biology and Genetics Department, Neurodegeneration Research Laboratory, Istanbul, Turkey
- * E-mail:
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