1
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Zhou C, Tang F, Dong T, Liu HB, Deng L, Margolis RL, Li PP. Role of Bβ1 overexpression in the pathogenesis of SCA12. Mov Disord 2024. [PMID: 38798069 DOI: 10.1002/mds.29839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 04/14/2024] [Accepted: 05/07/2024] [Indexed: 05/29/2024] Open
Abstract
BACKGROUND Spinocerebellar ataxia type 12 (SCA12) is a neurodegenerative disease caused by a CAG/CTG repeat expansion at the PPP2R2B locus. OBJECTIVE We investigated how the CAG repeat expansion within the PPP2R2B 7B7D transcript influences the expression of Bβ1 and a potential protein containing a long polyserine tract. METHODS Transcript and protein expression were measured using quantitative PCR (qPCR) Role of Bβ1 overexpression in the pathogenesis of SCA12 and Western blot, respectively, in an SK-N-MC cell model that overexpresses the full-length PPP2R2B 7B7D transcript. The apoptotic effect of a protein containing a long polyserine tract on SK-N-MC cells was evaluated using caspase 3/7 activity. RESULTS The CAG repeat expansion increases the expression of the PPP2R2B 7B7D transcript, as well as Bβ1 protein, in an SK-N-MC cell model in which the full-length PPP2R2B 7B7D transcript is overexpressed. The CAG repeat expansion within the 7B7D transcript is translated into a long polyserine tract that triggers apoptosis in SK-N-MC cells. CONCLUSIONS The SCA12 mutation leads to overexpression of PPP2R2B Bβ1 and to expression of a protein containing a long polyserine tract; both these effects potentially contribute to SCA12 pathogenesis. © 2024 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Chengqian Zhou
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Fan Tang
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Tao Dong
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Hans B Liu
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Leon Deng
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Russell L Margolis
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Pan P Li
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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2
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Landles C, Milton RE, Ali N, Flomen R, Flower M, Schindler F, Gomez-Paredes C, Bondulich MK, Osborne GF, Goodwin D, Salsbury G, Benn CL, Sathasivam K, Smith EJ, Tabrizi SJ, Wanker EE, Bates GP. Subcellular Localization And Formation Of Huntingtin Aggregates Correlates With Symptom Onset And Progression In A Huntington'S Disease Model. Brain Commun 2020; 2:fcaa066. [PMID: 32954323 PMCID: PMC7425396 DOI: 10.1093/braincomms/fcaa066] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 04/02/2020] [Accepted: 04/13/2020] [Indexed: 12/12/2022] Open
Abstract
Huntington's disease is caused by the expansion of a CAG repeat within exon 1 of the HTT gene, which is unstable, leading to further expansion, the extent of which is brain region and peripheral tissue specific. The identification of DNA repair genes as genetic modifiers of Huntington's disease, that were known to abrogate somatic instability in Huntington's disease mouse models, demonstrated that somatic CAG expansion is central to disease pathogenesis, and that the CAG repeat threshold for pathogenesis in specific brain cells might not be known. We have previously shown that the HTT gene is incompletely spliced generating a small transcript that encodes the highly pathogenic exon 1 HTT protein. The longer the CAG repeat, the more of this toxic fragment is generated, providing a pathogenic consequence for somatic expansion. Here, we have used the R6/2 mouse model to investigate the molecular and behavioural consequences of expressing exon 1 HTT with 90 CAGs, a mutation that causes juvenile Huntington's disease, compared to R6/2 mice carrying ∼200 CAGs, a repeat expansion of a size rarely found in Huntington's disease patient's blood, but which has been detected in post-mortem brains as a consequence of somatic CAG repeat expansion. We show that nuclear aggregation occurred earlier in R6/2(CAG)90 mice and that this correlated with the onset of transcriptional dysregulation. Whereas in R6/2(CAG)200 mice, cytoplasmic aggregates accumulated rapidly and closely tracked with the progression of behavioural phenotypes and with end-stage disease. We find that aggregate species formed in the R6/2(CAG)90 brains have different properties to those in the R6/2(CAG)200 mice. Within the nucleus, they retain a diffuse punctate appearance throughout the course of the disease, can be partially solubilized by detergents and have a greater seeding potential in young mice. In contrast, aggregates from R6/2(CAG)200 brains polymerize into larger structures that appear as inclusion bodies. These data emphasize that a subcellular analysis, using multiple complementary approaches, must be undertaken in order to draw any conclusions about the relationship between HTT aggregation and the onset and progression of disease phenotypes.
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Affiliation(s)
- Christian Landles
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Rebecca E Milton
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Nadira Ali
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Rachel Flomen
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Michael Flower
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Franziska Schindler
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany and Berlin Institute of Health (BIH), 10178 Berlin, Germany
| | - Casandra Gomez-Paredes
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Marie K Bondulich
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Georgina F Osborne
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Daniel Goodwin
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Grace Salsbury
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Caroline L Benn
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK.,LoQus23 Therapeutics, Babraham Research Campus, Cambridge, CB22 3AT, UK
| | - Kirupa Sathasivam
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Edward J Smith
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Sarah J Tabrizi
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
| | - Erich E Wanker
- Neuroproteomics, Max Delbrueck Center for Molecular Medicine, 13125 Berlin, Germany and Berlin Institute of Health (BIH), 10178 Berlin, Germany
| | - Gillian P Bates
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, UCL, Queen Square, WC1N 3BG, UK
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3
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Abstract
Trinucleotide repeats are a peculiar class of microsatellites involved in many neurological as well as developmental disorders. Their propensity to generate very large expansions over time is supposedly due to their capacity to form specific secondary structures, such as imperfect hairpins, triple helices, or G-quadruplexes. These unusual structures were proposed to trigger expansions in vivo. Here, I review known technical issues linked to these structures, such as slippage during polymerase chain reaction and aberrant migration of long trinucleotide repeats during agarose gel electrophoresis. Our current understanding of interactions between trinucleotide repeat secondary structures and the mismatch-repair machinery is also quickly reviewed, and critical questions relevant to these interactions are addressed.
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Affiliation(s)
- Guy-Franck Richard
- Department Genomes & Genetics, Institut Pasteur, CNRS UMR3525, Paris, France.
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4
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Kielar C, Morton AJ. Early Neurodegeneration in R6/2 Mice Carrying the Huntington's Disease Mutation with a Super-Expanded CAG Repeat, Despite Normal Lifespan. J Huntingtons Dis 2019; 7:61-76. [PMID: 29480204 DOI: 10.3233/jhd-170265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The threshold of CAG repeat expansion in the HTT gene that causes HD is 36 CAG repeats, although 'superlong' expansions are found in individual neurons in postmortem brains. Previously, we showed that, compared to mice with <250 CAG repeats, onset of disease in R6/2 mice carrying superlong (>440) CAG repeat expansions was delayed, and disease progression was slower. Inclusion pathology also differed from 250 CAG repeat mice, being dominated by a novel kind of extranuclear neuronal inclusion (nENNI) that resembles a class of aggregate seen in patients with the adult onset form of HD. Here, we characterised neuropathology in R6/2 mice with >400 CAG repeats using light and electron microscopy. nENNIs were found with increased frequency and wider distribution with age. Some nENNIs appear to 'mature' as the disease develops, developing a multi-layered cored structure. Mice with superlong CAG repeats do not develop clinical signs until they are around 30-40 weeks of age, and they attain a normal life span (>2 years). Nevertheless, they show brain atrophy and unequivocal neuron loss from the striatum and cortex by 22 weeks of age, an age at which similar pathology is seen in 250 CAG repeat mice. Since this time-point is 'end stage' for a 250 CAG mouse, but very far (at least 18 months) from end stage for a > 440 CAG repeat mouse, our data confirm that the appearance of clinical signs, the formation of inclusions, and neurodegeneration are processes that progress independently. A better understanding of the relationship between CAG repeat length, neurodegenerative pathways, and clinical behavioural signs is essential, if we are to find strategies to delay or reverse the course of this disease.
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Affiliation(s)
- Catherine Kielar
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - A Jennifer Morton
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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5
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Morton AJ, Skillings EA, Wood NI, Zheng Z. Antagonistic pleiotropy in mice carrying a CAG repeat expansion in the range causing Huntington's disease. Sci Rep 2019; 9:37. [PMID: 30631090 PMCID: PMC6328633 DOI: 10.1038/s41598-018-37102-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 11/28/2018] [Indexed: 02/06/2023] Open
Abstract
Antagonist pleiotropy, where a gene exerts a beneficial effect at early stages and a deleterious effect later on in an animal’s life, may explain the evolutionary persistence of devastating genetic diseases such as Huntington’s disease (HD). To date, however, there is little direct experimental evidence to support this theory. Here, we studied a transgenic mouse carrying the HD mutation with a repeat of 50 CAGs (R6/2_50) that is within the pathological range of repeats causing adult-onset disease in humans. R6/2_50 mice develop characteristic HD brain aggregate pathology, with aggregates appearing predominantly in the striatum and cortex. However, they show few signs of disease in their lifetime. On the contrary, R6/2_50 mice appear to benefit from carrying the mutation. They have extended lifespans compared to wildtype (WT) mice, and male mice show enhanced fecundity. Furthermore, R6/2_50 mice outperform WT mice on the rotarod and show equal or better performance in the two choice discrimination task than WT mice. This novel mouse line provides direct experimental evidence that, although the HD mutation causes a fatal neurodegenerative disorder, there may be premorbid benefits of carrying the mutation.
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Affiliation(s)
- A J Morton
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, United Kingdom.
| | - E A Skillings
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, United Kingdom
| | - N I Wood
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, United Kingdom
| | - Z Zheng
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3DY, United Kingdom
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6
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Polyzos AA, Wood NI, Williams P, Wipf P, Morton AJ, McMurray CT. XJB-5-131-mediated improvement in physiology and behaviour of the R6/2 mouse model of Huntington's disease is age- and sex- dependent. PLoS One 2018; 13:e0194580. [PMID: 29630611 PMCID: PMC5890981 DOI: 10.1371/journal.pone.0194580] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 03/06/2018] [Indexed: 11/18/2022] Open
Abstract
We have reported that the radical scavenger XJB-5-131 attenuates or reverses progression of the disease phenotype in the HdhQ(150/150) mouse, a slow onset model of HD. Here, we tested whether XJB-5-131 has beneficial effects in R6/2 mice, a severe early onset model of HD. We found that XJB-5-131 has beneficial effects in R6/2 mice, by delaying features of the motor and histological phenotype. The impact was sex-dependent, with a stronger effect in male mice. XJB-5-131 treatment improved some locomotor deficits in female R6/2 mice, but the effects were, in general, greater in male mice. Chronic treatment of male R6/2 mice with XJB-5-1-131 reduced weight loss, and improved the motor and temperature regulation deficits, especially in male mice. Treatment with XJB-5-131 had no effect on the lifespan of R6/2 mice. Nevertheless, it significantly slowed somatic expansion at 90 days, and reduced the density of inclusions. Our data show that while treatment with XJB-5-131 had complex effects on the phenotype of R6/2 mice, it produced a number of significant improvements in this severe model of HD.
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Affiliation(s)
- Aris A. Polyzos
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States of America
| | - Nigel I. Wood
- Department of Physiology, Development, and Neuroscience, Anatomy Building, University of Cambridge, Cambridge, United Kingdom
| | - Paul Williams
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States of America
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - A. Jennifer Morton
- Department of Physiology, Development, and Neuroscience, Anatomy Building, University of Cambridge, Cambridge, United Kingdom
| | - Cynthia T. McMurray
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, United States of America
- * E-mail:
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7
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Cao JK, Detloff PJ, Gardner RG, Stella N. Sex-dependent behavioral impairments in the HdhQ350/+ mouse line. Behav Brain Res 2018; 337:34-45. [PMID: 28927719 PMCID: PMC5659761 DOI: 10.1016/j.bbr.2017.09.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 08/08/2017] [Accepted: 09/13/2017] [Indexed: 11/29/2022]
Abstract
Huntington's Disease (HD) is an autosomal dominant neurodegenerative disease characterized by gradual deterioration of motor and cognitive functions and development of psychiatric deficits. Animal models provide powerful means to study the pathological processes, molecular dysfunctions and symptoms associated with HD. We performed a longitudinal behavioral study of the newly developed HdhQ350/+ mouse line, a knock-in model that expresses a repeat of 350 glutamines. We found remarkable sex-dependent differences on symptom onset and severity. While both sexes lose weight and grip strength, only HdhQ350/+ males have impaired motor coordination as measured by the rotarod and alterations in gait as measured by the catwalk assay. While HdhQ350/+ females do not exhibit impairment in motor coordination, we found a reduction in dark phase locomotor activity. Male and female HdhQ350/+ mice do not show anxiety as measured by the elevated plus maze or changes in exploration as measured by the open field test. To investigate these sex-dependent differences, we performed western blot analyses of striatal tissue. We measured equal mutant huntingtin protein expression in both sexes and found evidence of aggregation. We found the expected decrease of DARPP-32 expression only in female HdhQ350/+ mice. Remarkably, we found no evidence of reduction in synaptophysin or CB1 receptors in HdhQ350/+ tissue of either sex. Our study indicates that male and female HdhQ350/+ mice differentially recapitulate select behavioral impairments commonly measured in other HD mouse models with limited sex-dependent changes in recognized histopathological markers. We conclude that expanded polyglutamine repeats influence HD pathogenesis in a sex-dependent manner.
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Affiliation(s)
- Jessica K Cao
- Department of Pharmacology, University of Washington, Seattle, WA, 98195, United States
| | - Peter J Detloff
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - Richard G Gardner
- Department of Pharmacology, University of Washington, Seattle, WA, 98195, United States
| | - Nephi Stella
- Department of Pharmacology, University of Washington, Seattle, WA, 98195, United States; Department of Psychiatry & Behavioral Sciences, University of Washington, Seattle, WA, 98195, United States.
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8
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Sawiak SJ, Wood NI, Morton AJ. Similar Progression of Morphological and Metabolic Phenotype in R6/2 Mice with Different CAG Repeats Revealed by In Vivo Magnetic Resonance Imaging and Spectroscopy. J Huntingtons Dis 2017; 5:271-283. [PMID: 27662335 DOI: 10.3233/jhd-160208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Huntington's disease (HD) is caused by an unstable polyglutamine (CAG) repeat in the HD gene, whereby a CAG repeat length greater than ∼36 leads to the disease. In HD patients, longer repeats correlate with more severe disease and earlier death. This is also seen in R6/2 mice carrying repeat lengths up to ∼200. Paradoxically, R6/2 mice with repeat lengths >300 have a less aggressive phenotype and longer lifespan than those with shorter repeats. The mechanism underlying this phenomenon is unknown. OBJECTIVE To investigate the consequences of longer repeat lengths on structural changes in the brains of R6/2 mice, especially with regard to progressive atrophy. METHODS We used longitudinal in vivo magnetic resonance imaging (MRI) and spectroscopy (MRS) to compare pathological changes in two strains of R6/2 mice, one with a rapidly progressing disease (250 CAG repeats), and the other with a less aggressive phenotype (350 CAG repeats). RESULTS We found significant progressive brain atrophy in both 250 and 350 CAG repeat mice, as well as changes in metabolites (glutamine/glutamate, choline and aspartate). Although similar in magnitude, atrophy in the brains of 350 CAG R6/2 mice progressed more slowly than that seen in 250 CAG mice, in line with the milder phenotype and longer lifespan. Interestingly, significant atrophy was detectable in 350 CAG mice as early as 8-12 weeks of age, although behavioural abnormalities in these mice are not apparent before 25-30 weeks. This finding fits well with human data from the PREDICT-HD and TRACK-HD project, where reductions in brain volume were found 10 years in advance of the onset of symptoms. CONCLUSIONS The similar brain atrophy with a mismatch between onset of brain atrophy and behavioural phenotype in HD mice with 350 repeats will make this mouse particularly useful for modelling early stages of HD pathology.
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Affiliation(s)
- Stephen J Sawiak
- Wolfson Brain Imaging Centre, University of Cambridge, Box 65 Addenbrooke's Hospital, Cambridge, UK.,Behavioural and Clinical Neuroscience Institute, University of Cambridge, Cambridge, UK
| | - Nigel I Wood
- Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - A Jennifer Morton
- Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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9
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Zaghloul EM, Gissberg O, Moreno PMD, Siggens L, Hällbrink M, Jørgensen AS, Ekwall K, Zain R, Wengel J, Lundin KE, Smith CIE. CTG repeat-targeting oligonucleotides for down-regulating Huntingtin expression. Nucleic Acids Res 2017; 45:5153-5169. [PMID: 28334749 PMCID: PMC5435994 DOI: 10.1093/nar/gkx111] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 02/06/2017] [Indexed: 12/12/2022] Open
Abstract
Huntington's disease (HD) is a fatal, neurodegenerative disorder in which patients suffer from mobility, psychological and cognitive impairments. Existing therapeutics are only symptomatic and do not significantly alter the disease progression or increase life expectancy. HD is caused by expansion of the CAG trinucleotide repeat region in exon 1 of the Huntingtin gene (HTT), leading to the formation of mutant HTT transcripts (muHTT). The toxic gain-of-function of muHTT protein is a major cause of the disease. In addition, it has been suggested that the muHTT transcript contributes to the toxicity. Thus, reduction of both muHTT mRNA and protein levels would ideally be the most useful therapeutic option. We herein present a novel strategy for HD treatment using oligonucleotides (ONs) directly targeting the HTT trinucleotide repeat DNA. A partial, but significant and potentially long-term, HTT knock-down of both mRNA and protein was successfully achieved. Diminished phosphorylation of HTT gene-associated RNA-polymerase II is demonstrated, suggestive of reduced transcription downstream the ON-targeted repeat. Different backbone chemistries were found to have a strong impact on the ON efficiency. We also successfully use different delivery vehicles as well as naked uptake of the ONs, demonstrating versatility and possibly providing insights for in vivo applications.
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Affiliation(s)
- Eman M Zaghloul
- Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, SE-141 86 Huddinge, Stockholm, Sweden.,Department of Pharmaceutics, Faculty of Pharmacy, Alexandria University, El-Khartoum square, Azareeta, 21 521 Alexandria, Egypt
| | - Olof Gissberg
- Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, SE-141 86 Huddinge, Stockholm, Sweden
| | - Pedro M D Moreno
- Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, SE-141 86 Huddinge, Stockholm, Sweden.,Instituto de Engenharia Biomédica, Universidade do Porto, 4200-135 Porto, Portugal.,Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135, Porto, Portugal
| | - Lee Siggens
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden, SE-141 86, Huddinge, Stockholm, Sweden
| | - Mattias Hällbrink
- Department of Neurochemistry, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Anna S Jørgensen
- Department of Physics and Chemistry, Nucleic Acid Centre University of Southern Denmark, DK-5230 Odense, Denmark
| | - Karl Ekwall
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden, SE-141 86, Huddinge, Stockholm, Sweden
| | - Rula Zain
- Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, SE-141 86 Huddinge, Stockholm, Sweden.,Department of Clinical Genetics, Centre for Rare Diseases, Karolinska University Hospital, SE-171 76 Stockholm, Sweden
| | - Jesper Wengel
- Department of Physics and Chemistry, Nucleic Acid Centre University of Southern Denmark, DK-5230 Odense, Denmark
| | - Karin E Lundin
- Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, SE-141 86 Huddinge, Stockholm, Sweden
| | - C I Edvard Smith
- Department of Laboratory Medicine, Clinical Research Center, Karolinska Institutet, SE-141 86 Huddinge, Stockholm, Sweden
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10
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Jacobsen JC, Erdin S, Chiang C, Hanscom C, Handley RR, Barker DD, Stortchevoi A, Blumenthal I, Reid SJ, Snell RG, MacDonald ME, Morton AJ, Ernst C, Gusella JF, Talkowski ME. Potential molecular consequences of transgene integration: The R6/2 mouse example. Sci Rep 2017; 7:41120. [PMID: 28120936 PMCID: PMC5264158 DOI: 10.1038/srep41120] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 11/11/2016] [Indexed: 01/09/2023] Open
Abstract
Integration of exogenous DNA into a host genome represents an important route to generate animal and cellular models for exploration into human disease and therapeutic development. In most models, little is known concerning structural integrity of the transgene, precise site of integration, or its impact on the host genome. We previously used whole-genome and targeted sequencing approaches to reconstruct transgene structure and integration sites in models of Huntington’s disease, revealing complex structural rearrangements that can result from transgenesis. Here, we demonstrate in the R6/2 mouse, a widely used Huntington’s disease model, that integration of a rearranged transgene with coincident deletion of 5,444 bp of host genome within the gene Gm12695 has striking molecular consequences. Gm12695, the function of which is unknown, is normally expressed at negligible levels in mouse brain, but transgene integration has resulted in cortical expression of a partial fragment (exons 8–11) 3’ to the transgene integration site in R6/2. This transcript shows significant expression among the extensive network of differentially expressed genes associated with this model, including synaptic transmission, cell signalling and transcription. These data illustrate the value of sequence-level resolution of transgene insertions and transcription analysis to inform phenotypic characterization of transgenic models utilized in therapeutic research.
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Affiliation(s)
- Jessie C Jacobsen
- Centre for Brain Research, School of Biological Sciences, The University of Auckland 1010, New Zealand
| | - Serkan Erdin
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Program in Medical and Population Genetics, Broad Institute of M.I.T and Harvard, Cambridge, Massachusetts 02143, USA
| | - Colby Chiang
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Carrie Hanscom
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Renee R Handley
- Centre for Brain Research, School of Biological Sciences, The University of Auckland 1010, New Zealand
| | - Douglas D Barker
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Alex Stortchevoi
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Ian Blumenthal
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Suzanne J Reid
- Centre for Brain Research, School of Biological Sciences, The University of Auckland 1010, New Zealand
| | - Russell G Snell
- Centre for Brain Research, School of Biological Sciences, The University of Auckland 1010, New Zealand
| | - Marcy E MacDonald
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Program in Medical and Population Genetics, Broad Institute of M.I.T and Harvard, Cambridge, Massachusetts 02143, USA.,Department of Neurology, Harvard Medical School, Boston, Massachusetts 02115 USA
| | - A Jennifer Morton
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, United Kingdom
| | - Carl Ernst
- Department of Psychiatry, McGill University, Montreal, Quebec ON H4H 1R3, Canada
| | - James F Gusella
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Program in Medical and Population Genetics, Broad Institute of M.I.T and Harvard, Cambridge, Massachusetts 02143, USA.,Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115 USA
| | - Michael E Talkowski
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.,Program in Medical and Population Genetics, Broad Institute of M.I.T and Harvard, Cambridge, Massachusetts 02143, USA.,Department of Neurology, Harvard Medical School, Boston, Massachusetts 02115 USA.,Psychiatric and Neurodevelopmental Genetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, 02114 USA
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11
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Kane AD, Niu Y, Herrera EA, Morton AJ, Giussani DA. Impaired Nitric Oxide Mediated Vasodilation In The Peripheral Circulation In The R6/2 Mouse Model Of Huntington's Disease. Sci Rep 2016; 6:25979. [PMID: 27181166 PMCID: PMC4867587 DOI: 10.1038/srep25979] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 04/26/2016] [Indexed: 02/05/2023] Open
Abstract
Recent evidence shows that the Huntington's disease (HD) extends beyond the nervous system to other sites, including the cardiovascular system. Further, the cardiovascular pathology pre-dates neurological decline, however the mechanisms involved remain unclear. We investigated in the R6/2 mouse model of HD nitric oxide (NO) dependent and independent endothelial mechanisms. Femoral artery reactivity was determined by wire myography in wild type (WT) and R6/2 mice at 12 and 16 weeks of adulthood. WT mice showed increased endothelial relaxation between 12 and 16 weeks (Rmax: 72 ± 7% vs. 97 ± 13%, P < 0.05). In contrast, R6/2 mice showed enhanced endothelial relaxation already by 12 weeks (Rmax at 12w: 72 ± 7% vs. 94 ± 5%, WT vs. R6/2, P < 0.05) that declined by 16 weeks compared with WT mice (Rmax at 16w: 97 ± 13% vs. 68 ± 7%, WT vs. R6/2, P < 0.05). In WT mice, the increase in femoral relaxation between 12 and 16 weeks was due to enhanced NO dependent mechanisms. By 16 weeks of adult age, the R6/2 mouse developed overt endothelial dysfunction due to an inability to increase NO dependent vasodilation. The data add to the growing literature of non-neural manifestations of HD and implicate NO depletion as a key mechanism underlying the HD pathophysiology in the peripheral vasculature.
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Affiliation(s)
- Andrew D. Kane
- Department of Physiology, Development & Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
| | - Youguo Niu
- Department of Physiology, Development & Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
| | - Emilio A. Herrera
- Department of Physiology, Development & Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
| | - A. Jennifer Morton
- Department of Physiology, Development & Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
| | - Dino A. Giussani
- Department of Physiology, Development & Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, UK
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Wood NI, Sawiak SJ, Buonincontri G, Niu Y, Kane AD, Carpenter TA, Giussani DA, Morton AJ. Direct evidence of progressive cardiac dysfunction in a transgenic mouse model of Huntington's disease. J Huntingtons Dis 2016; 1:57-64. [PMID: 24339845 DOI: 10.3233/jhd-2012-120004] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
HD is a progressive genetic neurological disorder, characterized by motor as well as cognitive impairments. The gene carrying the mutation causing Huntington's disease (HD) is not brain specific, and there is increasing evidence for peripheral, as well as brain pathology in this disorder. Here, we used in vivo and ex vivo techniques to assess the cardiac function of mice transgenic for the HD mutation. Using magnetic resonance imaging (MRI) of the beating heart, we show that abnormalities previously reported in end-stage mice are present by mid-stages of the disease. We also found abnormalities that have not been hitherto reported, including changes in cardiac efficiency and a mechanical distortion of the beating heart. Using the Langendorff preparation, we show reduced coronary blood flow, impaired myocardial contractility and reduced left ventricular developed pressure in HD mouse hearts. Together, our findings suggest that there is significant pathology of the HD mouse heart, even by mid stages of disease. Previous clinical research has demonstrated that the risk of cognitive symptoms increases markedly in patients with heart failure. R6/2 mice show significant progressive cognitive abnormalities, so we hypothesize that cardiac pathology in the R6/2 mouse may contribute, not only to their progressive decline and death, but also to their cognitive dysfunction. We suggest that closer attention should be paid to cardiovascular symptoms in HD patients.
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Affiliation(s)
- Nigel I Wood
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UNITED KINGDOM
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13
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Buonincontri G, Wood NI, Puttick SG, Ward AO, Carpenter TA, Sawiak SJ, Morton AJ. Right ventricular dysfunction in the R6/2 transgenic mouse model of Huntington's disease is unmasked by dobutamine. J Huntingtons Dis 2014; 3:25-32. [PMID: 24744818 DOI: 10.3233/jhd-130083] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND Increasingly, evidence from studies in both animal models and patients suggests that cardiovascular dysfunction is important in HD. Previous studies measuring function of the left ventricle (LV) in the R6/2 model have found a clear cardiac abnormality, albeit with preserved LV systolic function. It was hypothesized that an impairment of RV function might play a role in this condition via mechanisms of ventricular interdependence. OBJECTIVE To investigate RV function in the R6/2 mouse model of Huntington's disease (HD). METHODS Cardiac cine-magnetic resonance imaging (MRI) was used to determine functional parameters in R6/2 mice. In a first experiment, these parameters were derived longitudinally to determine deterioration of cardiac function with disease progression. A second experiment compared the response to a stress test (using dobutamine) of wildtype and early-symptomatic R6/2 mice. RESULTS There was progressive deterioration of RV systolic function with age in R6/2 mice. Furthermore, beta-adrenergic stimulation with dobutamine revealed RV dysfunction in R6/2 mice before any overt symptoms of the disease were apparent. CONCLUSIONS This work adds to accumulating evidence of cardiovascular dysfunction in R6/2 mice, describing for the first time the involvement of the right ventricle. Cardiovascular dysfunction should be considered, both when treatment strategies are being designed, and when searching for biomarkers for HD.
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Affiliation(s)
- Guido Buonincontri
- Wolfson Brain Imaging Centre, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK, CB2 0QQ
| | - Nigel I Wood
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge, UK, CB2 3DY
| | - Simon G Puttick
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge, UK, CB2 3DY
| | - Alex O Ward
- Wolfson Brain Imaging Centre, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK, CB2 0QQ
| | - T Adrian Carpenter
- Wolfson Brain Imaging Centre, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK, CB2 0QQ
| | - Stephen J Sawiak
- Wolfson Brain Imaging Centre, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK, CB2 0QQ ; Behavioural and Clinical Neuroscience Institute, Department of Experimental Psychology, University of Cambridge, Downing Site, Cambridge, UK, CB2 3EB
| | - A Jennifer Morton
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Site, Cambridge, UK, CB2 3DY
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14
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Macdonald D, Tessari MA, Boogaard I, Smith M, Pulli K, Szynol A, Albertus F, Lamers MBAC, Dijkstra S, Kordt D, Reindl W, Herrmann F, McAllister G, Fischer DF, Munoz-Sanjuan I. Quantification assays for total and polyglutamine-expanded huntingtin proteins. PLoS One 2014; 9:e96854. [PMID: 24816435 PMCID: PMC4016121 DOI: 10.1371/journal.pone.0096854] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 04/12/2014] [Indexed: 11/18/2022] Open
Abstract
The expansion of a CAG trinucleotide repeat in the huntingtin gene, which produces huntingtin protein with an expanded polyglutamine tract, is the cause of Huntington's disease (HD). Recent studies have reported that RNAi suppression of polyglutamine-expanded huntingtin (mutant HTT) in HD animal models can ameliorate disease phenotypes. A key requirement for such preclinical studies, as well as eventual clinical trials, aimed to reduce mutant HTT exposure is a robust method to measure HTT protein levels in select tissues. We have developed several sensitive and selective assays that measure either total human HTT or polyglutamine-expanded human HTT proteins on the electrochemiluminescence Meso Scale Discovery detection platform with an increased dynamic range over other methods. In addition, we have developed an assay to detect endogenous mouse and rat HTT proteins in pre-clinical models of HD to monitor effects on the wild type protein of both allele selective and non-selective interventions. We demonstrate the application of these assays to measure HTT protein in several HD in vitro cellular and in vivo animal model systems as well as in HD patient biosamples. Furthermore, we used purified recombinant HTT proteins as standards to quantitate the absolute amount of HTT protein in such biosamples.
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Affiliation(s)
- Douglas Macdonald
- CHDI Management/CHDI Foundation, Los Angeles, California, United States of America
- * E-mail:
| | | | | | - Melanie Smith
- BioFocus, a Charles River company, Saffron Walden, United Kingdom
| | | | | | | | | | - Sipke Dijkstra
- BioFocus, a Charles River company, Leiden, The Netherlands
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Mason AG, Tomé S, Simard JP, Libby RT, Bammler TK, Beyer RP, Morton AJ, Pearson CE, La Spada AR. Expression levels of DNA replication and repair genes predict regional somatic repeat instability in the brain but are not altered by polyglutamine disease protein expression or age. Hum Mol Genet 2013; 23:1606-18. [PMID: 24191263 DOI: 10.1093/hmg/ddt551] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Expansion of CAG/CTG trinucleotide repeats causes numerous inherited neurological disorders, including Huntington's disease (HD), several spinocerebellar ataxias and myotonic dystrophy type 1. Expanded repeats are genetically unstable with a propensity to further expand when transmitted from parents to offspring. For many alleles with expanded repeats, extensive somatic mosaicism has been documented. For CAG repeat diseases, dramatic instability has been documented in the striatum, with larger expansions noted with advancing age. In contrast, only modest instability occurs in the cerebellum. Using microarray expression analysis, we sought to identify the genetic basis of these regional instability differences by comparing gene expression in the striatum and cerebellum of aged wild-type C57BL/6J mice. We identified eight candidate genes enriched in cerebellum, and validated four--Pcna, Rpa1, Msh6 and Fen1--along with a highly associated interactor, Lig1. We also explored whether expression levels of mismatch repair (MMR) proteins are altered in a line of HD transgenic mice, R6/2, that is known to show pronounced regional repeat instability. Compared with wild-type littermates, MMR expression levels were not significantly altered in R6/2 mice regardless of age. Interestingly, expression levels of these candidates were significantly increased in the cerebellum of control and HD human samples in comparison to striatum. Together, our data suggest that elevated expression levels of DNA replication and repair proteins in cerebellum may act as a safeguard against repeat instability, and may account for the dramatically reduced somatic instability present in this brain region, compared with the marked instability observed in the striatum.
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Ma L, Chen K, Clarke DJ, Nortcliffe CP, Wilson GG, Edwardson JM, Morton AJ, Jones AC, Dryden DTF. Restriction endonuclease TseI cleaves A:A and T:T mismatches in CAG and CTG repeats. Nucleic Acids Res 2013; 41:4999-5009. [PMID: 23525471 PMCID: PMC3643589 DOI: 10.1093/nar/gkt176] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The type II restriction endonuclease TseI recognizes the DNA target sequence 5′-G^CWGC-3′ (where W = A or T) and cleaves after the first G to produce fragments with three-base 5′-overhangs. We have determined that it is a dimeric protein capable of cleaving not only its target sequence but also one containing A:A or T:T mismatches at the central base pair in the target sequence. The cleavage of targets containing these mismatches is as efficient as cleavage of the correct target sequence containing a central A:T base pair. The cleavage mechanism does not apparently use a base flipping mechanism as found for some other type II restriction endonuclease recognizing similarly degenerate target sequences. The ability of TseI to cleave targets with mismatches means that it can cleave the unusual DNA hairpin structures containing A:A or T:T mismatches formed by the repetitive DNA sequences associated with Huntington’s disease (CAG repeats) and myotonic dystrophy type 1 (CTG repeats).
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Affiliation(s)
- Long Ma
- EaStChem School of Chemistry, University of Edinburgh, The King's Buildings, Edinburgh EH9 3JJ, UK
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17
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Single-stranded DNA loops as fiducial markers for exploring DNA-protein interactions in single molecule imaging. Methods 2013; 60:122-30. [PMID: 23500656 DOI: 10.1016/j.ymeth.2013.03.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 02/20/2013] [Accepted: 03/01/2013] [Indexed: 11/21/2022] Open
Abstract
A polymerase chain reaction (PCR) based method of adding a single-stranded DNA (ssDNA) hairpin loop to one end of linear double-stranded (ds) DNA templates was developed. The loop structure serves as a fiducial marker in single molecule imaging by atomic force microscopy (AFM) and can be applied to study DNA-protein interactions. The nucleic acid end-labels allow discrimination of the polarity of the DNA template in the AFM while limiting non-specific interactions which might occur from non-nucleic acid labels. Homo-polynucleotide ssDNA loops made up of 20 base-pairs (bp) for each of the four bases (A, T, G, C) were investigated to determine the effects of sequence on template labelling. The products were produced with high efficiency and high yield with the loop readily distinguished from the dsDNA template by height and diameter in the AFM. The application of the method to study DNA transcription was investigated by firing Escherichia Coli RNA polymerase (RNAP) from a λPR promoter in the direction of the loop-labelled end. The ssDNA loops captured elongating complexes of RNAP, arresting transcription and preventing dissociation. The dual role of the loop as a polarity marker and retainer of previously active RNAP will allow mechanisms of gene expression to be studied with single molecule sensitivity by AFM. This will enable insight into molecular interactions of RNAP on single DNA templates in convergent or tandem transcription configurations.
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Giles P, Elliston L, Higgs GV, Brooks SP, Dunnett SB, Jones L. Longitudinal analysis of gene expression and behaviour in the HdhQ150 mouse model of Huntington's disease. Brain Res Bull 2011; 88:199-209. [PMID: 22001697 DOI: 10.1016/j.brainresbull.2011.10.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Revised: 09/28/2011] [Accepted: 10/01/2011] [Indexed: 12/17/2022]
Abstract
Substantial transcriptional changes are seen in Huntington's disease (HD) brain and parallel early changes in gene expression are observed in mouse models of HD. Analysis of behaviour in such models also shows substantial deficits in motor, learning and memory tasks. We examined the changes in the transcriptional profile in the HdhQ150 mouse model of HD at 6, 12 and 18 months and correlated these changes with the behavioural tasks the animals had undertaken. Changes in gene expression over time showed a significant enrichment of RNAs altered in abundance that related to cognition in both HdhQ150 and wild-type animals. The most significantly down-regulated mRNA between genotypes over the whole time-course was Htt itself. Other changes between genotypes identified at 6 months related to chromatin organization and structure, whilst at 18 months changes related mainly to intracellular signalling. Correlation of the changes in gene product abundance with phenotypic changes revealed that weight and detection of the opposite position of the platform in the water maze seemed to correlate with the chromatin alterations whereas changes in the rotarod performance related mainly to intracellular signalling and homeostasis. These results implicate alterations in specific molecular pathways that may underpin changes in different behavioural tasks.
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Affiliation(s)
- Peter Giles
- MRC Centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Cardiff University, UK
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