2251
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Becher MW, Kotzuk JA, Sharp AH, Davies SW, Bates GP, Price DL, Ross CA. Intranuclear neuronal inclusions in Huntington's disease and dentatorubral and pallidoluysian atrophy: correlation between the density of inclusions and IT15 CAG triplet repeat length. Neurobiol Dis 1998; 4:387-97. [PMID: 9666478 DOI: 10.1006/nbdi.1998.0168] [Citation(s) in RCA: 314] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Huntington's disease (HD) is caused by CAG triplet repeat expansion in IT15 which leads to polyglutamine stretches in the HD protein product, huntingtin. The pathological hallmark of HD is the degeneration of subsets of neurons, primarily those in the striatum and neocortex. Specific morphological markers of affected cells have not been identified in patients with HD, although a unique itranuclear inclusion was recently reported in neurons of transgenic animals expressing a construct encoding the N-terminal part (including the glutamine repeat) of huntingtin (Davies et al., 1997). In order to understand the importance of this finding, we sought for comparable nuclear abnormalities in autopsy material from patients with HD. In all 20 HD cases examined, anti-ubiquitin and N-terminal huntingtin antibodies identified itranuclear inclusions in neurons and the frequency of these lesions correlated with the length of the CAG repeat in IT15. In addition, examination of material from the related HD-like triplet repeat disorder, dentatorubral and pallidoluysian atrophy, also revealed intranuclear neuronal inclusions. These findings suggest that intranuclear inclusions containing protein aggregates may be common feature of the pathogenesis of glutamine repeat neurodegenerative disorders.
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Affiliation(s)
- M W Becher
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2196, USA.
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2252
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Affiliation(s)
- A S Hackam
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, University of British Columbia, Vancouver, Canada
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2253
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Abstract
Huntingtin is the protein product of the gene for Huntington's disease (HD) and carries a polyglutamine repeat that is expanded in HD (>36 units). Huntingtin-associated protein (HAP1) is a neuronal protein and binds to huntingtin in association with the polyglutamine repeat. Like huntingtin, HAP1 has been found to be a cytoplasmic protein associated with membranous organelles, suggesting the existence of a protein complex including HAP1, huntingtin, and other proteins. Using the yeast two-hybrid system, we found that HAP1 also binds to dynactin P150(Glued) (P150), an accessory protein for cytoplasmic dynein that participates in microtubule-dependent retrograde transport of membranous organelles. An in vitro binding assay showed that both huntingtin and P150 selectively bound to a glutathione transferase (GST)-HAP1 fusion protein. An immunoprecipitation assay demonstrated that P150 and huntingtin coprecipitated with HAP1 from rat brain cytosol. Western blot analysis revealed that HAP1 was enriched in rat brain microtubules and comigrated with P150 and huntingtin in sucrose gradients. Immunofluorescence showed that transfected HAP1 colocalized with P150 and huntingtin in human embryonic kidney (HEK) 293 cells. We propose that HAP1, P150, and huntingtin are present in a protein complex that may participate in dynein-dynactin-associated intracellular transport.
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2254
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Kahlem P, Green H, Djian P. Transglutaminase action imitates Huntington's disease: selective polymerization of Huntingtin containing expanded polyglutamine. Mol Cell 1998; 1:595-601. [PMID: 9660943 DOI: 10.1016/s1097-2765(00)80059-3] [Citation(s) in RCA: 148] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Different proteins bearing polyglutamine of excessive length are lethal to neurons and cause human disease of the central nervous system. In parts of the brain affected by Huntington's disease, the amount of the huntingtin with expanded polyglutamine is reduced and there appear huntingtin-containing polymers of larger molecular weight. We show here that huntingtin is a substrate of transglutaminase in vitro and that the rate constant of the reaction increases with length of the polyglutamine over a range of an order of magnitude. As a result, huntingtin with expanded polyglutamine is preferentially incorporated into polymers. Both disappearance of the huntingtin with expanded polyglutamine and its replacement by polymeric forms are prevented by inhibitors of transglutaminase. The effect of transglutaminase therefore duplicates the changes in the affected parts of the brain.
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Affiliation(s)
- P Kahlem
- Centre National de la Recherche Scientifique, Centre de Recherche sur l'Endocrinologie Moléculaire et le Développement, Meudon-Bellevue, France
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2255
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Gacy AM, Goellner GM, Spiro C, Chen X, Gupta G, Bradbury EM, Dyer RB, Mikesell MJ, Yao JZ, Johnson AJ, Richter A, Melançon SB, McMurray CT. GAA instability in Friedreich's Ataxia shares a common, DNA-directed and intraallelic mechanism with other trinucleotide diseases. Mol Cell 1998; 1:583-93. [PMID: 9660942 DOI: 10.1016/s1097-2765(00)80058-1] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We show that GAA instability in Friedreich's Ataxia is a DNA-directed mutation caused by improper DNA structure at the repeat region. Unlike CAG or CGG repeats, which form hairpins, GAA repeats form a YRY triple helix containing non-Watson-Crick pairs. As with hairpins, triplex mediates intergenerational instability in 96% of transmissions. In families with Friedreich's Ataxia, the only recessive trinucleotide disease, GAA instability is not a function of the number of long alleles, ruling out homologous recombination or gene conversion as a major mechanism. The similarity of mutation pattern among triple repeat-related diseases indicates that all trinucleotide instability occurs by a common, intraallelic mechanism that depends on DNA structure. Secondary structure mediates instability by creating strong polymerase pause sites at or within the repeats, facilitating slippage or sister chromatid exchange.
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Affiliation(s)
- A M Gacy
- Department of Pharmacology, Mayo Foundation, Rochester, Minnesota 55905, USA
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2256
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Abstract
Twenty-five genes have been identified in which mutations cause epileptic seizures in mice. The gene for a Na+/H+ exchanger has recently been found to underlie the spontaneous mutant slow wave epilepsy. Studies of such mutants should help elucidate the mechanisms that control neuronal excitability.
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Affiliation(s)
- J O McNamara
- Department of Medicine, Duke University Medical Center, 401 Bryan Research Building, Research Drive, Durham, North Carolina 27710, USA
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2257
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Igarashi S, Koide R, Shimohata T, Yamada M, Hayashi Y, Takano H, Date H, Oyake M, Sato T, Sato A, Egawa S, Ikeuchi T, Tanaka H, Nakano R, Tanaka K, Hozumi I, Inuzuka T, Takahashi H, Tsuji S. Suppression of aggregate formation and apoptosis by transglutaminase inhibitors in cells expressing truncated DRPLA protein with an expanded polyglutamine stretch. Nat Genet 1998; 18:111-7. [PMID: 9462738 DOI: 10.1038/ng0298-111] [Citation(s) in RCA: 272] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To elucidate the molecular mechanisms whereby expanded polyglutamine stretches elicit a gain of toxic function, we expressed full-length and truncated DRPLA (dentatorubral-pallidoluysian atrophy) cDNAs with or without expanded CAG repeats in COS-7 cells. We found that truncated DRPLA proteins containing an expanded polyglutamine stretch form filamentous peri- and intranuclear aggregates and undergo apoptosis. The apoptotic cell death was partially suppressed by the transglutaminase inhibitors cystamine and monodansyl cadaverine (but not putrescine), suggesting involvement of a transglutaminase reaction and providing a potential basis for the development of therapeutic measures for CAG-repeat expansion diseases.
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Affiliation(s)
- S Igarashi
- Department of Neurology, Brain Research Institute, Niigata University, Asahimachi Niigata, Japan
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2258
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Martindale D, Hackam A, Wieczorek A, Ellerby L, Wellington C, McCutcheon K, Singaraja R, Kazemi-Esfarjani P, Devon R, Kim SU, Bredesen DE, Tufaro F, Hayden MR. Length of huntingtin and its polyglutamine tract influences localization and frequency of intracellular aggregates. Nat Genet 1998; 18:150-4. [PMID: 9462744 DOI: 10.1038/ng0298-150] [Citation(s) in RCA: 363] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
It is unclear how polyglutamine expansion is associated with the pathogenesis of Huntington disease (HD). Here, we provide evidence that polyglutamine expansion leads to the formation of large intracellular aggregates in vitro and in vivo. In vitro these huntingtin-containing aggregates disrupt normal cellular architecture and increase in frequency with polyglutamine length. Huntingtin truncated at nucleotide 1955, close to the caspase-3 cleavage site, forms perinuclear aggregates more readily than full-length huntingtin and increases the susceptibility of cells to death following apoptotic stimuli. Further truncation of huntingtin to nucleotide 436 results in both intranuclear and perinuclear aggregates. For a given protein size, increasing polyglutamine length is associated with increased cellular toxicity. Asymptomatic transgenic mice expressing full-length huntingtin with 138 polyglutamines form exclusively perinuclear aggregates in neurons. These data support the hypothesis that proteolytic cleavage of mutant huntingtin leads to the development of aggregates which compromise cell viability, and that their localization is influenced by protein length.
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Affiliation(s)
- D Martindale
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada
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2259
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Sahba S, Nechiporuk A, Figueroa KP, Nechiporuk T, Pulst SM. Genomic structure of the human gene for spinocerebellar ataxia type 2 (SCA2) on chromosome 12q24.1. Genomics 1998; 47:359-64. [PMID: 9480749 DOI: 10.1006/geno.1997.5131] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Spinocerebellar ataxia type 2 (SCA2) is a member of a group of neurodegenerative diseases that are caused by instability of a DNA CAG repeat. We report the genomic structure of the SCA2 gene. Its 25 exons, encompassing approximately 130 kb of genomic DNA, were mapped onto the physical map of the region. Exonic sizes varied from 37 to 890 bp, and intronic sizes ranged from 323 bp to more than 15 kb. The CAG repeat was contained in the 5' coding region of the gene in exon 1. Determination of the splice junction sequences indicated the presence of only one deviation from the GT-AG rule at the donor splice site of intron 9, which contained a GC instead of a GT dinucleotide. Exon 10, immediately downstream from this rare splice donor site, was alternatively spliced. Alternative splicing does not affect the reading frame and is predicted to encode an isoform containing 70 amino acids less.
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Affiliation(s)
- S Sahba
- Division of Neurology, Cedars-Sinai Medical Center, CSMC Burns and Allen Research Institute, Los Angeles, California, 90048, USA
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2260
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Davies SW, Beardsall K, Turmaine M, DiFiglia M, Aronin N, Bates GP. Are neuronal intranuclear inclusions the common neuropathology of triplet-repeat disorders with polyglutamine-repeat expansions? Lancet 1998; 351:131-3. [PMID: 9439509 DOI: 10.1016/s0140-6736(97)08360-8] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Neuronal intranuclear inclusions have been found in the brain of a transgenic mouse model of Huntington's disease and in necropsy brain tissue of patients with Huntington's disease. We suggest that neuronal intranuclear inclusions are the common neuropathology for all inherited diseases caused by expansion of polyglutamine repeats. We also suggest that patients with a pathological diagnosis of neuronal intranuclear hyaline inclusion disease may also have polyglutamine repeat expansions.
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Affiliation(s)
- S W Davies
- Department of Anatomy and Developmental Biology, University College London, UK
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2261
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Butler R, Leigh PN, McPhaul MJ, Gallo JM. Truncated forms of the androgen receptor are associated with polyglutamine expansion in X-linked spinal and bulbar muscular atrophy. Hum Mol Genet 1998; 7:121-7. [PMID: 9384612 DOI: 10.1093/hmg/7.1.121] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
X-linked spinal and bulbar muscular atrophy (SBMA) is a rare form of motor neuron degeneration linked to a CAG repeat expansion in the first exon of the androgen receptor gene coding for a polyglutamine tract. In order to investigate the properties of the SBMA androgen receptor in neuronal cells, cDNAs coding for a wild-type (19 CAG repeats) and a SBMA mutant androgen receptor (52 CAG repeats) were transfected into mouse neuroblastoma NB2a/d1 cells. The full length androgen receptor proteins, of 110-112 kDa and 114-116 kDa for the wild-type and mutant protein, respectively, were detected by Western blotting in transfected cells. In addition, the presence of an expanded polyglutamine tract in the SBMA androgen receptor appears to enhance the production of C-terminally truncated fragments of the protein. A 74 kDa fragment was particularly prominent in cells expressing the SBMA androgen receptor. From its size, it can be deduced that the 74 kDa fragment lacks the hormone binding domain but retains the DNA binding domain. The 74 kDa fragment may therefore be toxic to motor neurons by initiating the transcription of specific genes in the absence of hormonal control. Immunofluorescence microscopy on transfected NB2a/d1 cells showed that, after hormone activation, the wild-type androgen receptor translocated to the nucleus whereas the SBMA androgen receptor was mainly localized in the cytoplasm in the form of dense aggregates with very little androgen receptor protein in the nucleus. This could explain the reduction in transcriptional activity of the SBMA mutant as compared with wild-type androgen receptor.
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Affiliation(s)
- R Butler
- Department of Clinical Neurosciences, Institute of Psychiatry and King's College School of Medicine and Dentistry, De Crespigny Park, London SE5 8AF, UK
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2262
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Himmelbauer H, Wedemeyer N, Haaf T, Wanker EE, Schalkwyk LC, Lehrach H. IRS-PCR-based genetic mapping of the huntingtin interacting protein gene (HIP1) on mouse chromosome 5. Mamm Genome 1998; 9:26-31. [PMID: 9434941 DOI: 10.1007/s003359900674] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Huntington's disease (HD) is a devastating central nervous system disorder. Even though the gene responsible has been positionally cloned recently, its etiology has remained largely unclear. To investigate potential disease mechanisms, we conducted a search for binding partners of the HD-protein huntingtin. With the yeast two-hybrid system, one such interacting factor, the huntingtin interacting protein-1 (HIP-1), was identified (Wanker et al. 1997; Kalchman et al. 1997) and the human gene mapped to 7q11.2. In this paper we demonstrate the localization of the HIP1 mouse homologue (Hip1) into a previously identified region of human-mouse synteny on distal mouse Chromosome (Chr) 5, both employing an IRS-PCR-based mapping strategy and traditional fluorescent in situ hybridization (FISH) mapping.
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Affiliation(s)
- H Himmelbauer
- Max-Planck-Institute for Molecular Genetics, Berlin-Dahlem, Germany
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2263
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Cooper AJL, Sheu KFR, Burke JR, Onodera O, Strittmatter WJ, Roses AD, Blass JP. Inhibition of α-ketoglutarate-and pyruvate dehydrogenase complexes in E. coli by a glutathione S-transferase containing a pathological length poly-Q domain: A possible role of energy deficit in neurological diseases associated with poly-Q expansions? AGE 1998; 21:25-30. [PMID: 23604331 PMCID: PMC3455770 DOI: 10.1007/s11357-998-0004-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
At least seven adult-onset neurodegenerative diseases, including Huntington's disease (HD), are caused by genes containing expanded CAG triplets within their coding regions. The expanded CAG repeats give rise to extended stretches of polyglutamines (Qn) in the proteins expressed by the affected genes. Generally, n ≥40 in affected individuals and ≤36 in clinically unaffected individuals. The expansion has been proposed to confer a "toxic gain of function" to the mutated protein. Poly-Q domains have recently been shown to be excellent substrates of tissue transglutaminase. We investigated the effects of expression of glutathione S-transferase constructs containing poly-Q inserts of various lengths (GSTQn where n = 0, 10, 62 or 81) on the activity of some key metabolic enzymes in the host Escherischia coil-an organism not known to have transglutaminase activity. E. coil carrying the GSTQ62 construct exhibited statistically significant decreases in the specific activities of α-ketoglutarate dehydrogenase complex (KGDHC) and pyruvate dehydrogenase complex (PDHC). Previous work has shown that KGDHC and PDHC activities are reduced in the brains of Alzheimer's disease (AD) patients. Our results suggest that KGDHC and PDHC may be particularly susceptible to the effects of a number of disparate insults, including those associated with AD and HD.
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Affiliation(s)
- Arthur J. L. Cooper
- />Department of Biochemistry, Cornell University Medical College, New York, New York 10021 USA
- />Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021 USA
- />Burke Medical Research Institute, Cornell University Medical College, White Plains, New York 10605 USA
- />Burke Medical Research Institute, 785 Mamaroneck Avenue, White Plains, NY 10605
| | - K-F. Rex Sheu
- />Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021 USA
- />Burke Medical Research Institute, Cornell University Medical College, White Plains, New York 10605 USA
| | - James R. Burke
- />Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710 USA
- />Deane Laboratory, Duke University Medical Center, Durham, North Carolina 27710 USA
| | - Osamu Onodera
- />Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710 USA
- />Deane Laboratory, Duke University Medical Center, Durham, North Carolina 27710 USA
| | - Warren J. Strittmatter
- />Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710 USA
- />Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710 USA
- />Deane Laboratory, Duke University Medical Center, Durham, North Carolina 27710 USA
| | - Allen D. Roses
- />Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710 USA
- />Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710 USA
- />Deane Laboratory, Duke University Medical Center, Durham, North Carolina 27710 USA
| | - John P. Blass
- />Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021 USA
- />Department of Medicine, Cornell University Medical College, New York, New York 10021 USA
- />Burke Medical Research Institute, Cornell University Medical College, White Plains, New York 10605 USA
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2264
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Ordway JM, Tallaksen-Greene S, Gutekunst CA, Bernstein EM, Cearley JA, Wiener HW, Dure LS, Lindsey R, Hersch SM, Jope RS, Albin RL, Detloff PJ. Ectopically expressed CAG repeats cause intranuclear inclusions and a progressive late onset neurological phenotype in the mouse. Cell 1997; 91:753-63. [PMID: 9413985 DOI: 10.1016/s0092-8674(00)80464-x] [Citation(s) in RCA: 245] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mutations responsible for several human neurodegenerative disorders are expansions of translated CAG repeats beyond a normal size range. To address the role of repeat context, we have introduced a 146-unit CAG repeat into the mouse hypoxanthine phosphoribosyltransferase gene (Hprt). Mutant mice express a form of the HPRT protein that contains a long polyglutamine repeat. These mice develop a phenotype similar to the human translated CAG repeat disorders. Repeat containing mice show a late onset neurological phenotype that progresses to premature death. Neuronal intranuclear inclusions are present in affected mice. Our results show that CAG repeats do not need to be located within one of the classic repeat disorder genes to have a neurotoxic effect.
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Affiliation(s)
- J M Ordway
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, 35294, USA
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2265
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Nakamoto M, Takebayashi H, Kawaguchi Y, Narumiya S, Taniwaki M, Nakamura Y, Ishikawa Y, Akiguchi I, Kimura J, Kakizuka A. A CAG/CTG expansion in the normal population. Nat Genet 1997; 17:385-6. [PMID: 9398837 DOI: 10.1038/ng1297-385] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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2266
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Hofstetter JR, Zhang A, Mayeda AR, Guscar T, Nurnberger JI, Lahiri DK. Genomic DNA from mice: a comparison of recovery methods and tissue sources. BIOCHEMICAL AND MOLECULAR MEDICINE 1997; 62:197-202. [PMID: 9441873 DOI: 10.1006/bmme.1997.2637] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Our aim is to identify an extraction method and the source of mouse tissue(s) that could allow a high-resolution genomic scan from a living mouse. We compared and optimized two methods for yield, purity of DNA, and their use in the polymerase chain reaction (PCR) of DNA extracted from different mouse tissues. In addition to whole blood, tissue samples from the brain, liver, testis, and tail were included in this study. The Rapid Method (RM) is preferable for the whole blood samples and testis and brain tissue samples because it is quicker, less toxic, and more cost-effective than the proteinase K method (PM). For liver the PM produced higher yields of DNA with less degradation than the RM. For tail tip, the PM produced a higher yield of DNA, but the RM resulted in a higher yield of PCR product. From a living mouse, a tail snip generated a sufficient amount of DNA for several hundred PCRs but not a complete genomic scan. We suggest that the RM can be used to extract genomic DNA for a complete genomic scan which requires either testicular tissues or repeated blood samples from the suborbital sinus over several months without sacrificing the animal.
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Affiliation(s)
- J R Hofstetter
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis 46202, USA
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2267
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White JK, Auerbach W, Duyao MP, Vonsattel JP, Gusella JF, Joyner AL, MacDonald ME. Huntingtin is required for neurogenesis and is not impaired by the Huntington's disease CAG expansion. Nat Genet 1997; 17:404-10. [PMID: 9398841 DOI: 10.1038/ng1297-404] [Citation(s) in RCA: 384] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Huntington's disease (HD) is an autosomal-dominant neurodegenerative disorder caused by a CAG repeat expansion that lengthens a glutamine segment in the novel huntingtin protein. To elucidate the molecular basis of HD, we extended the polyglutamine tract of the mouse homologue, Hdh, by targetted introduction of an expanded human HD CAG repeat, creating mutant HdhneoQ50 and HdhQ50 alleles that express reduced and wild-type levels of altered huntingtin, respectively. Mice homozygous for reduced levels displayed characteristic aberrant brain development and perinatal lethality, indicating a critical function for Hdh in neurogenesis. However, mice with normal levels of mutant huntingtin did not display these abnormalities, indicating that the expanded CAG repeat does not eliminate or detectably impair huntingtin's neurogenic function. Thus, the HD defect in man does not mimic complete or partial Hdh inactivation and appears to cause neurodegenerative disease by a gain-of-function mechanism.
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Affiliation(s)
- J K White
- Molecular Neurogenetics Unit, Massachusetts General Hospital, Charlestown 02129, USA
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2268
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Schöls L, Amoiridis G, Büttner T, Przuntek H, Epplen JT, Riess O. Autosomal dominant cerebellar ataxia: phenotypic differences in genetically defined subtypes? Ann Neurol 1997; 42:924-32. [PMID: 9403486 DOI: 10.1002/ana.410420615] [Citation(s) in RCA: 236] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Seventy-seven families with autosomal dominant cerebellar ataxia were analyzed for the CAG repeat expansions causing spinocerebellar ataxia (SCA) types 1, 2, 3, and 6. The SCA1 mutation accounted for 9%, SCA2 for 10%, SCA3 for 42%, and SCA6 for 22% of German ataxia families. Seven of 27 SCA6 patients had no family history of ataxia. Age at onset correlated inversely with repeat length in all subtypes. Yet the average effect of one CAG unit on onset age was different for each SCA subtype. We compared clinical, electrophysiological, and magnetic resonance imaging (MRI) findings to identify phenotypic characteristics of genetically defined SCA subtypes. Slow saccades, hyporeflexia, myoclonus, and action tremor proposed SCA2. SCA3 patients frequently developed diplopia, severe spasticity or pronounced peripheral neuropathy, and impaired temperature discrimination, apart from ataxia. SCA6 presented with a predominantly cerebellar syndrome and patients often had onset after 55 years of age. SCA1 was characterized by markedly prolonged peripheral and central motor conduction times in motor evoked potentials. MRI scans showed pontine and cerebellar atrophy in SCA1 and SCA2. In SCA3, enlargement of the fourth ventricle was the main sequel of atrophy. SCA6 presented with pure cerebellar atrophy on MRI. However, overlap between the four SCA subtypes was broad.
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Affiliation(s)
- L Schöls
- Department of Neurology, St Josef Hospital, Ruhr-University, Bochum, Germany
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2269
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Cooper AJ, Sheu KR, Burke JR, Onodera O, Strittmatter WJ, Roses AD, Blass JP. Transglutaminase-catalyzed inactivation of glyceraldehyde 3-phosphate dehydrogenase and alpha-ketoglutarate dehydrogenase complex by polyglutamine domains of pathological length. Proc Natl Acad Sci U S A 1997; 94:12604-9. [PMID: 9356496 PMCID: PMC25053 DOI: 10.1073/pnas.94.23.12604] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Several adult-onset neurodegenerative diseases are caused by genes with expanded CAG triplet repeats within their coding regions and extended polyglutamine (Qn) domains within the expressed proteins. Generally, in clinically affected individuals n >/= 40. Glyceraldehyde 3-phosphate dehydrogenase binds tightly to four Qn disease proteins, but the significance of this interaction is unknown. We now report that purified glyceraldehyde 3-phosphate dehydrogenase is inactivated by tissue transglutaminase in the presence of glutathione S-transferase constructs containing a Qn domain of pathological length (n = 62 or 81). The dehydrogenase is less strongly inhibited by tissue transglutaminase in the presence of constructs containing shorter Qn domains (n = 0 or 10). Purified alpha-ketoglutarate dehydrogenase complex also is inactivated by tissue transglutaminase plus glutathione S-transferase constructs containing pathological-length Qn domains (n = 62 or 81). The results suggest that tissue transglutaminase-catalyzed covalent linkages involving the larger poly-Q domains may disrupt cerebral energy metabolism in CAG/Qn expansion diseases.
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Affiliation(s)
- A J Cooper
- Department of Biochemistry, Cornell University Medical College, New York, NY 10021, USA.
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2270
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Sathasivam K, Baxendale S, Mangiarini L, Bertaux F, Hetherington C, Kanazawa I, Lehrach H, Bates GP. Aberrant processing of the Fugu HD (FrHD) mRNA in mouse cells and in transgenic mice. Hum Mol Genet 1997; 6:2141-9. [PMID: 9328479 DOI: 10.1093/hmg/6.12.2141] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The puffer fish ( Fugu rubripes ) has a compact genome of 400 Mbp which is approximately 7.5-fold smaller than the human genome. It contains a similar number of genes but is deficient in intergenic, intronic and dispersed repetitive sequences. Fugu is becoming established as the model vertebrate genome for the identification and characterisation of novel human genes and conserved regulatory sequences. It has also been proposed that Fugu genes may provide natural mini-genes for the production of transgenic mice. We have used the Fugu homologue of the Huntington's disease (HD) gene to test this possibility. The human and Fugu HD genes cover 170 kb and 23 kb respectively and have previously been sequenced in their entirety. In Fugu tissue, the Fugu HD gene was found to be expressed as predicted from the gene sequence but three differentially spliced forms were also detected. Despite the absence of conserved promoter sequences, the Fugu promoter was found to be functional in mouse cells. We have generated mice transgenic for the Fugu HD gene and conducted a detailed expression analysis across the entire 10 kb transcript. This revealed the presence of many aberrant splice forms which would be incompatible with the production of the Fugu huntingtin protein. The Fugu HD gene is incorrectly processed in mouse cells both in vitro and in vivo which sheds doubt on the usefulness of Fugu genes for transgenesis.
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Affiliation(s)
- K Sathasivam
- Division of Medical and Molecular Genetics, UMDS, Guy's Hospital, London SE1 9RT, UK
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2271
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2272
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Abstract
Transgenic and knockout mice have been proposed as substitutes for one of the standard 2-yr rodent assays. The advantages of using genetically engineered mouse models is that fewer mice are needed, the time to develop disease is greatly reduced, and the mice are predisposed to developing cancer by virtue of gain or loss of functions. The models currently being used have yielded a large amount of data and have proved to be informative for risk assessment; however, they are still far from ideal. In fact, they inherently do not reflect the complexity of mutation and carcinogenesis in humans. Recent advances in technology and the creation of new knockout mice may produce more useful and more sensitive models. This review covers two recent advances in technology--inducible and regulatable gene expression and targeted genetic modifications in the genome--that will allow us to make better models. I also discuss new gene deletion and transgenic mouse models and their potential impact on risk-assessment assays. These models are presented in the context of four basic components or events that occur in the multistep process leading to cancer: maintenance of gene expression patterns, genome stability and DNA repair, cell-cell communication and signaling, and cell-cycle regulation. Finally, surrogate markers and utility in risk assessment are also discussed. This review is meant to stimulate further discussion in the field and to generate excitement about working toward the next generation of risk-assessment models.
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Affiliation(s)
- M P Rosenberg
- Department of Genomics, Glaxo Wellcome Research, Inc., Research Triangle Park, North Carolina
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2273
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Bates GP, Davies SW. Transgenic mouse models of neurodegenerative disease caused by CAG/polyglutamine expansions. MOLECULAR MEDICINE TODAY 1997; 3:508-15. [PMID: 9430787 DOI: 10.1016/s1357-4310(97)01142-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
CAG/polyglutamine expansion is the mutational mechanism that causes a number of late-onset neurodegenerative diseases. Expanded CAG repeats are unstable: they vary in size between tissues and change in size upon transmission from parent to offspring. These mutations are thought to impart a dominant gain of function to the proteins in which they are located. Recent reports describing the first mouse models of these diseases promise to shed light on the molecular mechanisms underlying CAG-repeat instability, the pathways by which polyglutamine expansion causes cell death and the factors that determine the specificity of the neurodegeneration.
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2274
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Affiliation(s)
- N D Mazarakis
- Neonatal Neurosciences Unit, Imperial College, School of Medicine, Hammersmith Hospital, London
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2275
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Purkinje cell expression of a mutant allele of SCA1 in transgenic mice leads to disparate effects on motor behaviors, followed by a progressive cerebellar dysfunction and histological alterations. J Neurosci 1997. [PMID: 9295384 DOI: 10.1523/jneurosci.17-19-07385.1997] [Citation(s) in RCA: 178] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurological disorder caused by the expansion of a CAG repeat encoding a polyglutamine tract. Work presented here describes the behavioral and neuropathological course seen in mutant SCA1 transgenic mice. Behavioral tests indicate that at 5 weeks of age mutant mice have an impaired performance on the rotating rod in the absence of deficits in balance and coordination. In contrast, these mutant SCA1 mice have an increased initial exploratory behavior. Thus, expression of the mutant SCA1 allele within cerebellar Purkinje cells has divergent effects on the motor behavior of juvenile animals: a compromise of rotating rod performance and a simultaneous enhancement of initial exploratory activity. With age, these animals develop incoordination with concomitant progressive Purkinje neuron dendritic and somatic atrophy but relatively little cell loss. Therefore, the eventual development of ataxia caused by the expression of a mutant SCA1 allele is not the result of cell death per se, but the result of cellular dysfunction and morphological alterations that occur before neuronal demise.
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2276
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Ross CA, Margolis RL, Rosenblatt A, Ranen NG, Becher MW, Aylward E. Huntington disease and the related disorder, dentatorubral-pallidoluysian atrophy (DRPLA). Medicine (Baltimore) 1997; 76:305-38. [PMID: 9352736 DOI: 10.1097/00005792-199709000-00001] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Affiliation(s)
- C A Ross
- Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2196, USA
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2277
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Affiliation(s)
- Frank M. Longo
- Department of Neurology, Veterans Administration Medical Center and University of California, San Francisco, School of Medicine, San Francisco, California
| | - Stephen M. Massa
- Department of Neurology, Veterans Administration Medical Center and University of California, San Francisco, School of Medicine, San Francisco, California
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2278
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Davies SW, Turmaine M, Cozens BA, DiFiglia M, Sharp AH, Ross CA, Scherzinger E, Wanker EE, Mangiarini L, Bates GP. Formation of neuronal intranuclear inclusions underlies the neurological dysfunction in mice transgenic for the HD mutation. Cell 1997; 90:537-48. [PMID: 9267033 DOI: 10.1016/s0092-8674(00)80513-9] [Citation(s) in RCA: 1606] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Huntington's disease (HD) is one of an increasing number of human neurodegenerative disorders caused by a CAG/polyglutamine-repeat expansion. The mutation occurs in a gene of unknown function that is expressed in a wide range of tissues. The molecular mechanism responsible for the delayed onset, selective pattern of neuropathology, and cell death observed in HD has not been described. We have observed that mice transgenic for exon 1 of the human HD gene carrying (CAG)115 to (CAG)156 repeat expansions develop pronounced neuronal intranuclear inclusions, containing the proteins huntingtin and ubiquitin, prior to developing a neurological phenotype. The appearance in transgenic mice of these inclusions, followed by characteristic morphological change within neuronal nuclei, is strikingly similar to nuclear abnormalities observed in biopsy material from HD patients.
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Affiliation(s)
- S W Davies
- Department of Anatomy and Developmental Biology, University College London, United Kingdom
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2279
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Scherzinger E, Lurz R, Turmaine M, Mangiarini L, Hollenbach B, Hasenbank R, Bates GP, Davies SW, Lehrach H, Wanker EE. Huntingtin-encoded polyglutamine expansions form amyloid-like protein aggregates in vitro and in vivo. Cell 1997; 90:549-58. [PMID: 9267034 DOI: 10.1016/s0092-8674(00)80514-0] [Citation(s) in RCA: 936] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mechanism by which an elongated polyglutamine sequence causes neurodegeneration in Huntington's disease (HD) is unknown. In this study, we show that the proteolytic cleavage of a GST-huntingtin fusion protein leads to the formation of insoluble high molecular weight protein aggregates only when the polyglutamine expansion is in the pathogenic range. Electron micrographs of these aggregates revealed a fibrillar or ribbon-like morphology, reminiscent of scrapie prions and beta-amyloid fibrils in Alzheimer's disease. Subcellular fractionation and ultrastructural techniques showed the in vivo presence of these structures in the brains of mice transgenic for the HD mutation. Our in vitro model will aid in an eventual understanding of the molecular pathology of HD and the development of preventative strategies.
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Affiliation(s)
- E Scherzinger
- Max-Planck-Institut für Molekulare Genetik, Berlin, Germany
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2280
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Sirover MA. Role of the glycolytic protein, glyceraldehyde-3-phosphate dehydrogenase, in normal cell function and in cell pathology. J Cell Biochem 1997. [DOI: 10.1002/(sici)1097-4644(19970801)66:2<133::aid-jcb1>3.0.co;2-r] [Citation(s) in RCA: 170] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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2281
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Paulson HL, Perez MK, Trottier Y, Trojanowski JQ, Subramony SH, Das SS, Vig P, Mandel JL, Fischbeck KH, Pittman RN. Intranuclear inclusions of expanded polyglutamine protein in spinocerebellar ataxia type 3. Neuron 1997; 19:333-44. [PMID: 9292723 DOI: 10.1016/s0896-6273(00)80943-5] [Citation(s) in RCA: 571] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mechanism of neurodegeneration in CAG/polyglutamine repeat expansion diseases is unknown but is thought to occur at the protein level. Here, in studies of spinocerebellar ataxia type 3, also known as Machado-Joseph disease (SCA3/MJD), we show that the disease protein ataxin-3 accumulates in ubiquitinated intranuclear inclusions selectively in neurons of affected brain regions. We further provide evidence in vitro for a model of disease in which an expanded polyglutamine-containing fragment recruits full-length protein into insoluble aggregates. Together with recent findings from transgenic models, our results suggest that intranuclear aggregation of the expanded protein is a unifying feature of CAG/polyglutamine diseases and may be initiated or catalyzed by a glutamine-containing fragment of the disease protein.
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Affiliation(s)
- H L Paulson
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104, USA
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2282
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Maier E, Meier-Ewert S, Bancroft D, Lehrach H. Automated array technologies for gene expression profiling. Drug Discov Today 1997. [DOI: 10.1016/s1359-6446(97)01054-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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2283
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Theuring F, Thunecke M, Kosciessa U, Turner JD. Transgenic animals as models of neurodegenerative diseases in humans. Trends Biotechnol 1997; 15:320-5. [PMID: 9263480 DOI: 10.1016/s0167-7799(97)01066-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Neurodegenerative diseases are of major socioeconomic importance and represent an enormous challenge for the scientific and medical communities. Advances in molecular genetics during the past decade have begun to provide approaches for the establishment of animal models for these disorders using transgenic technology. Their analysis will lead to better understanding of disease pathogenesis and will be invaluable for the identification of novel diagnostic and therapeutic agents. With the current pace of genomic research, the generation of transgenic animal models, reproducing in full the pathology and symptoms of even complex disorders such as Alzheimer's disease, must now be considered achievable.
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Affiliation(s)
- F Theuring
- Medizinische Fakultät, Humboldt Universität, Institut für Pharmakologie und Toxikologie, Berlin, Germany
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2284
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Wellington CL, Brinkman RR, O'Kusky JR, Hayden MR. Toward understanding the molecular pathology of Huntington's disease. Brain Pathol 1997; 7:979-1002. [PMID: 9217979 PMCID: PMC8098409 DOI: 10.1111/j.1750-3639.1997.tb00897.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Huntington's Disease (HD) is caused by expansion of a CAG trinucleotide beyond 35 repeats within the coding region of a novel gene. Recently, new insights into the relationship between CAG expansion in the HD gene and pathological mechanisms have emerged. Survival analysis of a large cohort of affected and at-risk individuals with CAG sizes between 39 and 50 repeats have yielded probability curves of developing HD symptoms and dying of HD by a certain age. Animals transgenic for the first exon of huntingtin with large CAG repeats lengths have been reported to have a complex neurological phenotype that bears interesting similarities and differences to HD. The repertoire of huntingtin-interacting proteins continues to expand with the identification of HIP1, a protein whose yeast homologues have known functions in regulating events associated with the cytoskeleton. The ability of huntingtin to interact with two of its four known protein partners appears to be influenced by CAG length. Caspase 3 (apopain), a key cysteine protease known to play a seminal role in neural apoptosis, has also been demonstrated to specifically cleave huntingtin in a CAG length-dependent manner. Many of these features are combined in a model suggesting mechanisms by which the pathogenesis of HD may be initiated. The development of appropriate in vitro and animal models for HD will allow the validity of these models to be tested.
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Affiliation(s)
- C L Wellington
- Centre for Molecular Medicine and Therapeutics, Vancouver, BC, Canada
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2285
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Abstract
Huntington disease is an inherited neurodegeneration, for which the associated mutation was isolated in 1993. The mutation is an expansion of a CAG trinucleotide repeat, which translates to give a polyglutamine tract at the N-terminus of a large protein, huntingtin. Neither the normal nor the pathogenic functions of this protein have been identified, but it is clear that pathogenesis is mediated through the expanded polyglutamine tract within the protein, and that polyglutamine is toxic to cells. A number of proteins which interact with the N-terminal region of huntingtin have been isolated, but this has not, so far, yielded a rationale for pathogenesis. Huntingtin is found in areas of the brain that degenerate in this disease but is also associated with pathogenic inclusions in Alzheimer disease and Pick disease. It is possible that Huntington disease has pathogenic mechanisms in common with these other neurodegenerative diseases, and that the mechanism may relate to the formation of abnormal, cytoskeletal-associated, inclusions within cells.
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Affiliation(s)
- A L Jones
- Institute of Medical Genetics, University of Wales College of Medicine, Heath Park, Cardiff, UK
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2286
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Abstract
A plethora of post-transcriptional mechanisms are involved in essential steps in the pathway of genetic information expression in eukaryotes. These processes are specified by cis-acting signals on RNAs and are mediated by specific trans-acting factors, including RNA-binding proteins and small complementary RNAs. Recent information has begun to define the molecular mechanisms by which RNA-binding proteins recognize specific RNA sequences and influence the processing and function of RNA molecules.
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Affiliation(s)
- H Siomi
- Howard Hughes Medical Institute, University of Pennsylvania School of Medicine Philadelphia 19104-6148, USA.
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2287
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Abstract
The expansion of trinucleotide repeat sequences has now been shown to be the underlying cause of at least ten human disorders. Unifying features among these diseases include the unstable behavior of the triplet repeat during germline transmission when the length of the repeat exceeds a critical value. However, the trinucleotide repeat disorders can be divided into two distinct groups. Type I disorders involve the expansion of CAG repeats, which encode an expanded polyglutamine, inserted into the open-reading frame of a gene that is usually quite broadly expressed. Recently, mouse models for type I disorders have been developed and the basis of pathology is under study, both in these models and through biochemical and cell biological approaches. The type II disorders involve repeat expansions in noncoding regions of genes. The mechanisms by which these repeat expansions lead to pathology may be quite diverse.
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Affiliation(s)
- P S Reddy
- Department of Biology and Center for Cancer Research, Room E17-541, Massachusetts Institute of Technology, 40 Ames Street, Cambridge, MA 02139, USA.
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2288
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2289
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2290
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Haque NS, Borghesani P, Isacson O. Therapeutic strategies for Huntington's disease based on a molecular understanding of the disorder. MOLECULAR MEDICINE TODAY 1997; 3:175-83. [PMID: 9134531 DOI: 10.1016/s1357-4310(97)01012-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A mutation on chromosome 4p16.3 with an expanded polyglutamine tract has been identified as the cause of Huntington's disease (HD). The neuroscience and clinical community now faces the formidable challenge of using this information to develop a treatment against this fatal and currently untreatable disease. This article reviews the recent literature pertaining to HD and presents an overview of possible intervention strategies against the neurodegenerative process of HD. Because little is known about the physiological function of the HD gene, there are four biological levels at which therapies could be devised. Identification and cloning of the gene might direct novel therapies for HD using the following strategies: interference (1) at the DNA or (2) at the RNA level; (3) blocking the deleterious effect of the protein; and (4) physiological intervention using pharmacological agents or neural cell transplants.
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Affiliation(s)
- N S Haque
- Neuroregeneration Laboratory, Harvard Medical School/McLean Hospital, Belmont, MA 02178, USA
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2291
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Labosky PA, Winnier GE, Jetton TL, Hargett L, Ryan AK, Rosenfeld MG, Parlow AF, Hogan BL. The winged helix gene, Mf3, is required for normal development of the diencephalon and midbrain, postnatal growth and the milk-ejection reflex. Development 1997; 124:1263-74. [PMID: 9118797 DOI: 10.1242/dev.124.7.1263] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The mouse Mf3 gene, also known as Fkh5 and HFH-e5.1, encodes a winged helix/forkhead transcription factor. In the early embryo, transcripts for Mf3 are restricted to the presomitic mesoderm and anterior neurectoderm and mesoderm. By 9.5 days post coitum, expression in the nervous system is predominantly in the diencephalon, midbrain and neural tube. After midgestation, the highest level of mRNA is in the mammillary bodies, the posterior-most part of the hypothalamus. Mice homozygous for a deletion of the mf3 locus on a [129 × Black Swiss] background display variable phenotypes consistent with a requirement for the gene at several stages of embryonic and postnatal development. Approximately six percent of the mf3−/− embryos show an open neural tube in the diencephalon and midbrain region, and another five percent show a severe reduction of the posterior body axis; both these classes of affected embryos die in utero. Surviving homozygotes have an apparently normal phenotype at birth. Postnatally, however, mf3−/− pups are severely growth retarded and approximately one third die before weaning. This growth defect is not a direct result of lack of circulating growth hormone or thyrotropin. Mice that survive to weaning are healthy, but they show an abnormal clasping of the hindfeet when suspended by the tail. Although much smaller than normal, the mice are fertile. However, mf3−/− females cannot eject their milk supply to feed their pups. This nursing defect can be corrected with interperitoneal injections of oxytocin. These results provide evidence that Mf3 is required for normal hypothalamus development and suggest that Mf3 may play a role in postnatal growth and lactation.
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Affiliation(s)
- P A Labosky
- Department of Cell Biology, Vanderbilt University Medical School, Nashville, Tennessee 37232, USA.
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2292
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Wanker EE, Rovira C, Scherzinger E, Hasenbank R, Wälter S, Tait D, Colicelli J, Lehrach H. HIP-I: a huntingtin interacting protein isolated by the yeast two-hybrid system. Hum Mol Genet 1997; 6:487-95. [PMID: 9147654 DOI: 10.1093/hmg/6.3.487] [Citation(s) in RCA: 253] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
We report the discovery of the huntingtin interacting protein I (HIP-I) which binds specifically to the N-terminus of human huntingtin, both in the two-hybrid screen and in in vitro binding experiments. For the interaction in vivo, a protein region downstream of the polyglutamine stretch in huntingtin is essential. The HIP1 cDNA isolated by the two-hybrid screen encodes a 55 kDa fragment of a novel protein. Using an affinity-purified polyclonal antibody raised against recombinant HIP-I, a protein of 116 kDa was detected in brain extracts by Western blot analysis. The predicted amino acid sequence of the HIP-I fragment exhibits significant similarity to cytoskeleton proteins, suggesting that HIP-I and huntingtin play a functional role in the cell filament networks. The HIP1 gene is ubiquitously expressed in different brain regions at low level. HIP-I is enriched in human brain but can also be detected in other human tissues as well as in mouse brain. HIP-I and huntingtin behave almost identically during subcellular fractionation and both proteins are enriched in the membrane containing fractions.
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Affiliation(s)
- E E Wanker
- Max Planck Institut für Molekulare Genetik, Berlin (Dahlem), Germany
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2293
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2294
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Mangiarini L, Sathasivam K, Mahal A, Mott R, Seller M, Bates GP. Instability of highly expanded CAG repeats in mice transgenic for the Huntington's disease mutation. Nat Genet 1997; 15:197-200. [PMID: 9020849 DOI: 10.1038/ng0297-197] [Citation(s) in RCA: 217] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Six inherited neurodegenerative diseases are caused by a CAG/polyglutamine expansion, including spinal and bulbar muscular atrophy (SBMA), Huntington's disease (HD), spinocerebellar ataxia type 1 (SCA1), dentatorubral pallidoluysian atrophy (DRPLA) Machado-Joseph disease (MJD or SCA3) and SCA2. Normal and expanded HD allele sizes of 6-39 and 35-121 repeats have been reported, and the allele distributions for the other diseases are comparable. Intergenerational instability has been described in all cases, and repeats tend to be more unstable on paternal transmission. This may present as larger increases on paternal inheritance as in HD, or as a tendency to increase on male and decrease on female transmission as in SCA1 (ref. 15). Somatic repeat instability is also apparent and appears most pronounced in the CNS. The major exception is the cerebellum, which in HD, DRPLA, SCA1 and MJD has a smaller repeat relative to the other brain regions tested. Of non-CNS tissues, instability was observed in blood, liver, kidney and colon. A mouse model of CAG repeat instability would be helpful in unravelling its molecular basis although an absence of CAG repeat instability in transgenic mice has so far been reported. These studies include (CAG) in the androgen receptor cDNA, (CAG) in the HD cDNA, (CAG) in the SCA1 cDNA, (CAG) in the SCA3 cDNA and as an isolated (CAG) tract.
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Affiliation(s)
- L Mangiarini
- Division of Medical and Molecular Genetics, Guy's Hospital, London, UK
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2295
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Abstract
Several dominantly inherited, late onset, neurodegenerative diseases are due to expansion of CAG repeats, leading to expansion of glutamine repeats in the affected proteins. These proteins are of very different sizes and, with one exception, show no sequence homology to known proteins or to each other; their functions are unknown. In some, the glutamine repeat starts near the N-terminus, in another near the middle and in another near the C-terminus, but regardless of these differences, no disease has been observed in individuals with fewer than 37 repeats, and absence of disease has never been found in those with more than 41 repeats. Protein constructs with more than 41 repeats are toxic to E. coli and to CHO cells in culture, and they elicit ataxia in transgenic mice. These observations argue in favour of a distinct change of structure associated with elongation beyond 37-41 glutamine repeats. The review describes experiments designed to find out what these structures might be and how they could influence the properties of the proteins of which they form part. Poly-L-glutamines form pleated sheets of beta-strands held together by hydrogen bonds between their amides. Incorporation of glutamine repeats into a small protein of known structure made it associate irreversibly into oligomers. That association took place during the folding of the protein molecules and led to their becoming firmly interlocked by either strand- or domain-swapping. Thermodynamic considerations suggest that elongation of glutamine repeats beyond a certain length may lead to a phase change from random coils to hydrogen-bonded hairpins. Possible mechanisms of expansion of CAG repeats are discussed in the light of looped DNA model structures.
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Affiliation(s)
- M F Perutz
- MRC Laboratory of Molecular Biology, Cambridge, UK
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