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Truant R, Raymond LA, Xia J, Pinchev D, Burtnik A, Atwal RS. Canadian Association of Neurosciences Review: Polyglutamine Expansion Neurodegenerative Diseases. Can J Neurol Sci 2014; 33:278-91. [PMID: 17001815 DOI: 10.1017/s031716710000514x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
ABSTRACT:Since the early 1990s, DNA triplet repeat expansions have been found to be the cause in an ever increasing number of genetic neurologic diseases. A subset of this large family of genetic diseases has the expansion of a CAG DNA triplet in the open reading frame of a coding exon. The result of this DNA expansion is the expression of expanded glutamine amino acid repeat tracts in the affected proteins, leading to the term, Polyglutamine Diseases, which is applied to this sub-family of diseases. To date, nine distinct genes are known to be linked to polyglutamine diseases, including Huntington's disease, Machado-Joseph Disease and spinobulbar muscular atrophy or Kennedy's disease. Most of the polyglutamine diseases are characterized clinically as spinocerebellar ataxias. Here we discuss recent successes and advancements in polyglutamine disease research, comparing these different diseases with a common genetic flaw at the level of molecular biology and early drug design for a family of diseases where many new research tools for these genetic disorders have been developed. Polyglutamine disease research has successfully used interdisciplinary collaborative efforts, informative multiple mouse genetic models and advanced tools of pharmaceutical industry research to potentially serve as the prototype model of therapeutic research and development for rare neurodegenerative diseases.
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Affiliation(s)
- Ray Truant
- Department of Biochemistry and Biomedical Sciences McMaster University, Hamilton, ON, Canada
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2
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McCormick MA, Mason AG, Guyenet SJ, Dang W, Garza RM, Ting MK, Moller RM, Berger SL, Kaeberlein M, Pillus L, La Spada AR, Kennedy BK. The SAGA histone deubiquitinase module controls yeast replicative lifespan via Sir2 interaction. Cell Rep 2014; 8:477-86. [PMID: 25043177 DOI: 10.1016/j.celrep.2014.06.037] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 05/20/2014] [Accepted: 06/19/2014] [Indexed: 11/19/2022] Open
Abstract
We have analyzed the yeast replicative lifespan of a large number of open reading frame (ORF) deletions. Here, we report that strains lacking genes SGF73, SGF11, and UBP8 encoding SAGA/SLIK complex histone deubiquitinase module (DUBm) components are exceptionally long lived. Strains lacking other SAGA/SALSA components, including the acetyltransferase encoded by GCN5, are not long lived; however, these genes are required for the lifespan extension observed in DUBm deletions. Moreover, the SIR2-encoded histone deacetylase is required, and we document both a genetic and physical interaction between DUBm and Sir2. A series of studies assessing Sir2-dependent functions lead us to propose that DUBm strains are exceptionally long lived because they promote multiple prolongevity events, including reduced rDNA recombination and altered silencing of telomere-proximal genes. Given that ataxin-7, the human Sgf73 ortholog, causes the neurodegenerative disease spinocerebellar ataxia type 7, our findings indicate that the genetic and epigenetic interactions between DUBm and SIR2 will be relevant to neurodegeneration and aging.
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Affiliation(s)
- Mark A McCormick
- Buck Institute for Research on Aging, Novato, CA 94945, USA; Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Amanda G Mason
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA; Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Stephan J Guyenet
- Department of Medical Genetics, University of Washington, Seattle, WA 98195, USA
| | - Weiwei Dang
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA; Huffington Center on Aging, Baylor College of Medicine, Houston, TX 76798, USA
| | - Renee M Garza
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA; University of California, San Diego, Moores Cancer Center, La Jolla, CA 92093, USA
| | - Marc K Ting
- Buck Institute for Research on Aging, Novato, CA 94945, USA
| | - Rick M Moller
- Department of Pathology, University of Washington, Seattle, WA 98195, USA
| | - Shelley L Berger
- Department of Cell and Developmental Biology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Matt Kaeberlein
- Department of Pathology, University of Washington, Seattle, WA 98195, USA
| | - Lorraine Pillus
- University of California, San Diego, Moores Cancer Center, La Jolla, CA 92093, USA; Department of Pathology, University of Washington, Seattle, WA 98195, USA
| | - Albert R La Spada
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA; Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA; Department of Medical Genetics, University of Washington, Seattle, WA 98195, USA; Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Department of Neuroscience, University of California, San Diego, La Jolla, CA 92093, USA; Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Sanford Consortium for Regenerative Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
| | - Brian K Kennedy
- Buck Institute for Research on Aging, Novato, CA 94945, USA; Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
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3
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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: 223] [Impact Index Per Article: 20.3] [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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Abstract
Spinocerebellar ataxia type 7 (SCA7) is associated with progressive blindness, dominant transmission, and marked anticipation. SCA7 represents one of the polyglutamine expansion diseases with increase of CAG repeats. The gene maps to chromosome 3p12-p21.1. Normal values of CAG repeats range from 4 to 18. The SCA7 gene encodes a protein of largely unknown function, called ataxin-7. SCA7 is reported in many countries and ethnic groups. Its phenotypic expression depends on the number of expanded repeats. The infantile phenotype is very severe, with more than 100 repeats. The classic type has 50 to 55 repeats and is characterized by a combination of visual and ataxic disturbances lasting for 20-40 years.When the number of CAG repeats is between 36 and 43, the evolution is much slower, with few or no retinal abnormalities. A CAG repeat number from 18 to 35 is asymptomatic but predisposes to the development of the disorder when expanding to the pathological range through transmission. The diagnosis is made by molecular genetics. The neuropathology of the disorder includes atrophy of the spinocerebellar pathways, pyramidal tracts, and motor nuclei in the brainstem and spinal cord, a cone-rod sytrophy of the retina, and ataxin-7 immunoreactive neuronal intranuclear inclusions. The neuropathological features vary as a function of the number of CAG repeats. Present research deals mainly with the study of ataxin-7 in transfected neural cells and transgenic mouse models.
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Kahle JJ, Gulbahce N, Shaw CA, Lim J, Hill DE, Barabási AL, Zoghbi HY. Comparison of an expanded ataxia interactome with patient medical records reveals a relationship between macular degeneration and ataxia. Hum Mol Genet 2010; 20:510-27. [PMID: 21078624 PMCID: PMC3016911 DOI: 10.1093/hmg/ddq496] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Spinocerebellar ataxias 6 and 7 (SCA6 and SCA7) are neurodegenerative disorders caused by expansion of CAG repeats encoding polyglutamine (polyQ) tracts in CACNA1A, the alpha1A subunit of the P/Q-type calcium channel, and ataxin-7 (ATXN7), a component of a chromatin-remodeling complex, respectively. We hypothesized that finding new protein partners for ATXN7 and CACNA1A would provide insight into the biology of their respective diseases and their relationship to other ataxia-causing proteins. We identified 118 protein interactions for CACNA1A and ATXN7 linking them to other ataxia-causing proteins and the ataxia network. To begin to understand the biological relevance of these protein interactions within the ataxia network, we used OMIM to identify diseases associated with the expanded ataxia network. We then used Medicare patient records to determine if any of these diseases co-occur with hereditary ataxia. We found that patients with ataxia are at 3.03-fold greater risk of these diseases than Medicare patients overall. One of the diseases comorbid with ataxia is macular degeneration (MD). The ataxia network is significantly (P= 7.37 × 10−5) enriched for proteins that interact with known MD-causing proteins, forming a MD subnetwork. We found that at least two of the proteins in the MD subnetwork have altered expression in the retina of Ataxin-7266Q/+ mice suggesting an in vivo functional relationship with ATXN7. Together these data reveal novel protein interactions and suggest potential pathways that can contribute to the pathophysiology of ataxia, MD, and diseases comorbid with ataxia.
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Affiliation(s)
- Juliette J Kahle
- Department of Cellular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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6
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Young JE, Gouw L, Propp S, Sopher BL, Taylor J, Lin A, Hermel E, Logvinova A, Chen SF, Chen S, Bredesen DE, Truant R, Ptacek LJ, La Spada AR, Ellerby LM. Proteolytic cleavage of ataxin-7 by caspase-7 modulates cellular toxicity and transcriptional dysregulation. J Biol Chem 2007; 282:30150-60. [PMID: 17646170 DOI: 10.1074/jbc.m705265200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spinocerebellar ataxia type 7 (SCA7) is a polyglutamine (polyQ) disorder characterized by specific degeneration of cerebellar, brainstem, and retinal neurons. Although they share little sequence homology, proteins implicated in polyQ disorders have common properties beyond their characteristic polyQ tract. These include the production of proteolytic fragments, nuclear accumulation, and processing by caspases. Here we report that ataxin-7 is cleaved by caspase-7, and we map two putative caspase-7 cleavage sites to Asp residues at positions 266 and 344 of the ataxin-7 protein. Site-directed mutagenesis of these two caspase-7 cleavage sites in the polyQ-expanded form of ataxin-7 produces an ataxin-7 D266N/D344N protein that is resistant to caspase cleavage. Although ataxin-7 displays toxicity, forms nuclear aggregates, and represses transcription in human embryonic kidney 293T cells in a polyQ length-dependent manner, expression of the non-cleavable D266N/D344N form of polyQ-expanded ataxin-7 attenuated cell death, aggregate formation, and transcriptional interference. Expression of the caspase-7 truncation product of ataxin-7-69Q or -92Q, which removes the putative nuclear export signal and nuclear localization signals of ataxin-7, showed increased cellular toxicity. We also detected N-terminal polyQ-expanded ataxin-7 cleavage products in SCA7 transgenic mice similar in size to those generated by caspase-7 cleavage. In a SCA7 transgenic mouse model, recruitment of caspase-7 into the nucleus by polyQ-expanded ataxin-7 correlated with its activation. Our results, thus, suggest that proteolytic processing of ataxin-7 by caspase-7 may contribute to SCA7 disease pathogenesis.
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Affiliation(s)
- Jessica E Young
- Buck Institute for Age Research, Novato, California, 94945, USA
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7
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Abstract
The arrestins are a small family of proteins that regulate the signaling and trafficking of G-protein-coupled receptors and also serve as ubiquitous signaling regulators in the cytoplasm and nucleus. In vertebrates, the arrestins are a family of four proteins that regulate the signaling and trafficking of hundreds of different G-protein-coupled receptors (GPCRs). Arrestin homologs are also found in insects, protochordates and nematodes. Fungi and protists have related proteins but do not have true arrestins. Structural information is available only for free (unbound) vertebrate arrestins, and shows that the conserved overall fold is elongated and composed of two domains, with the core of each domain consisting of a seven-stranded β-sandwich. Two main intramolecular interactions keep the two domains in the correct relative orientation, but both of these interactions are destabilized in the process of receptor binding, suggesting that the conformation of bound arrestin is quite different. As well as binding to hundreds of GPCR subtypes, arrestins interact with other classes of membrane receptors and more than 20 surprisingly diverse types of soluble signaling protein. Arrestins thus serve as ubiquitous signaling regulators in the cytoplasm and nucleus.
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Affiliation(s)
- Eugenia V Gurevich
- Department of Pharmacology, Vanderbilt University, 2200 Pierce Avenue, Preston Research Building, Nashville, TN 37232, USA
| | - Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University, 2200 Pierce Avenue, Preston Research Building, Nashville, TN 37232, USA
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Taylor J, Grote SK, Xia J, Vandelft M, Graczyk J, Ellerby LM, La Spada AR, Truant R. Ataxin-7 can export from the nucleus via a conserved exportin-dependent signal. J Biol Chem 2006; 281:2730-9. [PMID: 16314424 DOI: 10.1074/jbc.m506751200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Spinocerebellar ataxia type 7 is a progressive neurodegenerative disorder caused by a CAG DNA triplet repeat expansion leading to an expanded polyglutamine tract in the ataxin-7 protein. Ataxin-7 appears to be a transcription factor and a component of the STAGA transcription coactivator complex. Here, using live cell imaging and inverted fluorescence recovery after photobleaching, we demonstrate that ataxin-7 has the ability to export from the nucleus via the CRM-1/exportin pathway and that ataxin-7 contains a classic leucine-type nuclear export signal (NES). We have precisely defined the location of this NES in ataxin-7 and found it to be fully conserved in all vertebrate species. Polyglutamine expansion was seen to reduce the nuclear export rate of mutant ataxin-7 relative to wild-type ataxin-7. Subtle point mutation of the NES in polyglutamine expanded ataxin-7 increased toxicity in primary cerebellar neurons in a polyglutamine length-dependent manner in the context of full-length ataxin-7. Our results add ataxin-7 to a growing list of polyglutamine disease proteins that are capable of nuclear shuttling, and we define an activity of ataxin-7 in the STAGA complex of trafficking between the nucleus and cytoplasm.
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Affiliation(s)
- Jillian Taylor
- Department of Biochemistry and Biomedical Sciences, McMaster University, HSC4H45 Hamilton, Ontario L8N3Z5 Canada
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9
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Ström AL, Forsgren L, Holmberg M. A role for both wild-type and expanded ataxin-7 in transcriptional regulation. Neurobiol Dis 2005; 20:646-55. [PMID: 15936949 DOI: 10.1016/j.nbd.2005.04.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 04/04/2005] [Accepted: 04/19/2005] [Indexed: 11/19/2022] Open
Abstract
Spinocerebellar ataxia type 7 (SCA7) is a neurodegenerative disease primarily affecting the brainstem, retina and Purkinje cells of the cerebellum. The disease is caused by a polyglutamine expansion in ataxin-7, a protein found in two complexes TFTC and STAGA, involved in transcriptional regulation. Transcriptional dysregulation has been implicated in the pathology of several polyglutamine diseases. In this paper, we analyzed the effect of both wild-type and expanded ataxin-7 on transcription driven by the co-activator CBP and the Purkinje cell expressed nuclear receptor RORalpha1. We could show that transcription mediated by both CBP and RORalpha1 was repressed by expanded ataxin-7. Interestingly, repression of transcription could also be observed with wild-type full-length ataxin-7, not only on CBP- and RORalpha1-mediated transcription, but also on basal transcription. The repression could be counteracted by inhibition of deacetylation, suggesting that ataxin-7 may act as a repressor of transcription by inhibiting the acetylation activity of TFTC and STAGA.
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Affiliation(s)
- Anna-Lena Ström
- Department of Medical Biosciences, Unit of Medical and Clinical Genetics, Umeå University, SE-901 87 Umeå, Sweden
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10
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Michalik A, Martin JJ, Van Broeckhoven C. Spinocerebellar ataxia type 7 associated with pigmentary retinal dystrophy. Eur J Hum Genet 2003; 12:2-15. [PMID: 14571264 DOI: 10.1038/sj.ejhg.5201108] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Spinocerebellar ataxia type 7 (SCA7) is an autosomal-dominant, late-onset, slowly progressive disorder, primarily characterized by gradual loss of motor coordination, resulting from dysfunction and degeneration of the cerebellum and its connecting pathways. The disease is caused by expansion of a CAG trinucleotide repeat within the SCA7 gene, which encodes a polyglutamine tract within a novel protein, termed ataxin-7. The expansion of polyglutamine-encoding CAG repeats in dissimilar genes underlies eight neurodegenerative conditions besides SCA7, including a number of dominant ataxias related to SCA7. Although elongated polyglutamine itself can initiate neuronal dysfunction and death, its toxicity is modulated by the context of the disease proteins, as evidenced by the differing clinical and pathological presentation of the various disorders. In this respect, it is exciting that SCA7 constitutes the only polyglutamine disorder, in which the photoreceptors of the retina are also severely affected, leading to retinal degeneration and blindness. Since the discovery of the SCA7 mutation, numerous studies attempted to pinpoint the molecular mechanisms underlying the unique features of SCA7, particularly the retinal involvement. Here we summarize the clinical, pathological, and genetic aspects of SCA7, and review the current understanding of the pathogenesis of this disorder.
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Affiliation(s)
- A Michalik
- Department of Molecular Genetics, Neurogenetics Group, Flanders Interuniversity Institute for Biotechnology, Antwerpen, Belgium
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Lebre AS, Brice A. Spinocerebellar ataxia 7 (SCA7). Cytogenet Genome Res 2003; 100:154-63. [PMID: 14526176 DOI: 10.1159/000072850] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2002] [Accepted: 12/14/2002] [Indexed: 11/19/2022] Open
Abstract
Spinocerebellar ataxia 7 (SCA7) is a progressive autosomal dominant neurodegenerative disorder characterized clinically by cerebellar ataxia associated with progressive macular dystrophy. The disease affects primarily the cerebellum and the retina, but also many other CNS structures as the disease progresses. SCA7 is caused by expansion of an unstable trinucleotide CAG repeat encoding a polyglutamine tract in the corresponding protein, ataxin-7. Normal SCA7 alleles contain 4-35 CAG repeats, whereas pathological alleles contain from 36-306 CAG repeats. SCA7 has a number of features in common with other diseases with polyglutamine expansions: (i) the appearance of clinical symptoms above a threshold number of CAG repeats (>35); (ii) a correlation between the size of the expansion and the rate of progression of the disease: the larger the repeat, the faster the progression; (iii) instability of the repeat sequence (approximately 12 CAG/transmission) that accounts for the marked anticipation of approximately 20 years/generation. The CAG repeat sequence is particularly unstable and de novo mutations can occur during paternal transmissions of intermediate size alleles (28-35 CAG repeats). This can explain the persistence of the disease in spite of the anticipation that should have resulted in its extinction.
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Affiliation(s)
- A-S Lebre
- INSERM U289, Groupe hospitalier Pitié-Salpêtrière, Paris, France.
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12
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Stevanin G, Dürr A, Brice A. Spinocerebellar ataxias caused by polyglutamine expansions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 516:47-77. [PMID: 12611435 DOI: 10.1007/978-1-4615-0117-6_3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Giovanni Stevanin
- INSERM U289, Institut Fédératif di Recherche des Neurosciences, Groupe Hospitalier Pitié-Salpêtriére, Paris, France
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Aleman TS, Cideciyan AV, Volpe NJ, Stevanin G, Brice A, Jacobson SG. Spinocerebellar ataxia type 7 (SCA7) shows a cone-rod dystrophy phenotype. Exp Eye Res 2002; 74:737-45. [PMID: 12126946 DOI: 10.1006/exer.2002.1169] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Autosomal dominant spinocerebellar ataxia 7 is associated with retinal degeneration. SCA7, the causative gene, encodes ataxin-7, a ubiquitous 892 amino acid protein of variable sub-cellular localization, and the disease is due to expansion of an unstable CAG repeat in the coding region of the gene. Recent increases in understanding of the mechanisms ofSCA7 -related retinopathy from in vitro and murine model studies prompted us to perform a detailed study of the retinal phenotype of affected members of a family with SCA7 mutation (45-47 CAG repeats). There was a spectrum of severity from mild to severe dysfunction. Early functional abnormalities were at both photoreceptor and post-receptoral levels. When cone and rod photoreceptor dysfunction was present, it was approximately equal. Regional retinal dysfunction was evident: there was more dysfunction centrally than peripherally with least effect in the midperiphery. In vivo cross-sectional retinal images with optical coherence tomography showed an early disease stage of altered foveal lamination (abnormal area of low reflectivity splitting the outer retina-choroidal complex) accompanied in the parafovea by reduced retinal thickness. Later disease stages showed foveal and parafoveal retinal thinning. The phenotype in this family with SCA7 is that of a cone-rod dystrophy. These observations increase interest in a recent hypothesis that ataxin-7 may interfere with the function of CRX (cone-rod homeobox), a transcription factor regulating photoreceptor genes and a cause of a cone-rod dystrophy phenotype in man.
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Affiliation(s)
- Tomas S Aleman
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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14
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Ström AL, Jonasson J, Hart P, Brännström T, Forsgren L, Holmberg M. Cloning and expression analysis of the murine homolog of the spinocerebellar ataxia type 7 (SCA7) gene. Gene 2002; 285:91-9. [PMID: 12039035 DOI: 10.1016/s0378-1119(02)00399-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Spinocerebellar ataxia type 7 (SCA7) is a neurodegenerative disease caused by the expansion of a polyglutamine tract in the protein ataxin-7, a protein of unknown function. In order to analyze the expression pattern of wild type ataxin-7 in detail, the murine SCA7 gene homolog was cloned and the expression pattern in mice analyzed. The SCA7 mouse and human gene exhibit a high degree of identity at both DNA (88.2%) and protein (88.7%) level. The CAG repeat region, known to be polymorphic in man, is conserved in mouse but contained only five repeats in all mouse strains analyzed. The arrestin homology domain and the nuclear localization signal found in human ataxin-7 is also conserved in the murine homolog. Expression of ataxin-7 was detected during mouse embryonic development and in all adult mouse tissues examined by northern and western blots. In brain, immunohistological staining revealed an ataxin-7 expression pattern similar to that in human, with ataxin-7 expression in cerebellum, several brainstem nuclei, cerebral cortex and hippocampus. Our data show high conservation of ataxin-7 both structurally and at the level of expression, suggesting a conserved role for the protein in mice and humans.
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MESH Headings
- Amino Acid Sequence
- Animals
- Ataxin-7
- Blotting, Northern
- Blotting, Western
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Embryo, Mammalian/metabolism
- Gene Expression
- Gene Expression Regulation, Developmental
- Male
- Mice
- Mice, Inbred C57BL
- Molecular Sequence Data
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Nervous System/growth & development
- Nervous System/metabolism
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Testis/metabolism
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Affiliation(s)
- Anna Lena Ström
- Department of Molecular Biology, Umeå University, SE-901 87, Umeå, Sweden
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15
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Oh AK, Jacobson KM, Jen JC, Baloh RW. Slowing of voluntary and involuntary saccades: an early sign in spinocerebellar ataxia type 7. Ann Neurol 2001; 49:801-4. [PMID: 11409434 DOI: 10.1002/ana.1059] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We describe quantitative oculomotor findings in a patient with subclinical spinocerebellar ataxia type 7 (SCA7) and a borderline mutation of 38 CAG repeats and her daughter with SCA7 and 46 repeats. Both subjects demonstrated significant slowing of voluntary and involuntary saccades, but retinal examination was normal. Smooth pursuit and fixation suppression of VOR were mildly impaired. Slow saccades may be the earliest neurologic finding even in asymptomatic SCA7 patients with normal ocular fundi. The SCA7 mutation probably has an early impact on brainstem fast eye movement centers.
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Affiliation(s)
- A K Oh
- Department of Neurology, University of California Los Angeles School of Medicine, 90095-1769, USA
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16
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Biochemical Genetics. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50029-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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