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Jiang A, Handley RR, Lehnert K, Snell RG. From Pathogenesis to Therapeutics: A Review of 150 Years of Huntington's Disease Research. Int J Mol Sci 2023; 24:13021. [PMID: 37629202 PMCID: PMC10455900 DOI: 10.3390/ijms241613021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Revised: 08/15/2023] [Accepted: 08/18/2023] [Indexed: 08/27/2023] Open
Abstract
Huntington's disease (HD) is a debilitating neurodegenerative genetic disorder caused by an expanded polyglutamine-coding (CAG) trinucleotide repeat in the huntingtin (HTT) gene. HD behaves as a highly penetrant dominant disorder likely acting through a toxic gain of function by the mutant huntingtin protein. Widespread cellular degeneration of the medium spiny neurons of the caudate nucleus and putamen are responsible for the onset of symptomology that encompasses motor, cognitive, and behavioural abnormalities. Over the past 150 years of HD research since George Huntington published his description, a plethora of pathogenic mechanisms have been proposed with key themes including excitotoxicity, dopaminergic imbalance, mitochondrial dysfunction, metabolic defects, disruption of proteostasis, transcriptional dysregulation, and neuroinflammation. Despite the identification and characterisation of the causative gene and mutation and significant advances in our understanding of the cellular pathology in recent years, a disease-modifying intervention has not yet been clinically approved. This review includes an overview of Huntington's disease, from its genetic aetiology to clinical presentation and its pathogenic manifestation. An updated view of molecular mechanisms and the latest therapeutic developments will also be discussed.
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Affiliation(s)
- Andrew Jiang
- Applied Translational Genetics Group, Centre for Brain Research, School of Biological Sciences, The University of Auckland, Auckland 1010, New Zealand; (R.R.H.); (K.L.); (R.G.S.)
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2
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LaForce GR, Philippidou P, Schaffer AE. mRNA isoform balance in neuronal development and disease. WILEY INTERDISCIPLINARY REVIEWS. RNA 2023; 14:e1762. [PMID: 36123820 PMCID: PMC10024649 DOI: 10.1002/wrna.1762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 07/11/2022] [Accepted: 08/15/2022] [Indexed: 11/07/2022]
Abstract
Balanced mRNA isoform diversity and abundance are spatially and temporally regulated throughout cellular differentiation. The proportion of expressed isoforms contributes to cell type specification and determines key properties of the differentiated cells. Neurons are unique cell types with intricate developmental programs, characteristic cellular morphologies, and electrophysiological potential. Neuron-specific gene expression programs establish these distinctive cellular characteristics and drive diversity among neuronal subtypes. Genes with neuron-specific alternative processing are enriched in key neuronal functions, including synaptic proteins, adhesion molecules, and scaffold proteins. Despite the similarity of neuronal gene expression programs, each neuronal subclass can be distinguished by unique alternative mRNA processing events. Alternative processing of developmentally important transcripts alters coding and regulatory information, including interaction domains, transcript stability, subcellular localization, and targeting by RNA binding proteins. Fine-tuning of mRNA processing is essential for neuronal activity and maintenance. Thus, the focus of neuronal RNA biology research is to dissect the transcriptomic mechanisms that underlie neuronal homeostasis, and consequently, predispose neuronal subtypes to disease. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.
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Affiliation(s)
- Geneva R LaForce
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Polyxeni Philippidou
- Department of Neurosciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Ashleigh E Schaffer
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio, USA
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Implications of Poly(A) Tail Processing in Repeat Expansion Diseases. Cells 2022; 11:cells11040677. [PMID: 35203324 PMCID: PMC8870147 DOI: 10.3390/cells11040677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/11/2022] [Accepted: 02/13/2022] [Indexed: 11/21/2022] Open
Abstract
Repeat expansion diseases are a group of more than 40 disorders that affect mainly the nervous and/or muscular system and include myotonic dystrophies, Huntington’s disease, and fragile X syndrome. The mutation-driven expanded repeat tract occurs in specific genes and is composed of tri- to dodeca-nucleotide-long units. Mutant mRNA is a pathogenic factor or important contributor to the disease and has great potential as a therapeutic target. Although repeat expansion diseases are quite well known, there are limited studies concerning polyadenylation events for implicated transcripts that could have profound effects on transcript stability, localization, and translation efficiency. In this review, we briefly present polyadenylation and alternative polyadenylation (APA) mechanisms and discuss their role in the pathogenesis of selected diseases. We also discuss several methods for poly(A) tail measurement (both transcript-specific and transcriptome-wide analyses) and APA site identification—the further development and use of which may contribute to a better understanding of the correlation between APA events and repeat expansion diseases. Finally, we point out some future perspectives on the research into repeat expansion diseases, as well as APA studies.
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Mohanan NK, Shaji F, Koshre GR, Laishram RS. Alternative polyadenylation: An enigma of transcript length variation in health and disease. WILEY INTERDISCIPLINARY REVIEWS-RNA 2021; 13:e1692. [PMID: 34581021 DOI: 10.1002/wrna.1692] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 06/16/2021] [Accepted: 08/24/2021] [Indexed: 12/19/2022]
Abstract
Alternative polyadenylation (APA) is a molecular mechanism during a pre-mRNA processing that involves usage of more than one polyadenylation site (PA-site) generating transcripts of varying length from a single gene. The location of a PA-site affects transcript length and coding potential of an mRNA contributing to both mRNA and protein diversification. This variation in the transcript length affects mRNA stability and translation, mRNA subcellular and tissue localization, and protein function. APA is now considered as an important regulatory mechanism in the pathophysiology of human diseases. An important consequence of the changes in the length of 3'-untranslated region (UTR) from disease-induced APA is altered protein expression. Yet, the relationship between 3'-UTR length and protein expression remains a paradox in a majority of diseases. Here, we review occurrence of APA, mechanism of PA-site selection, and consequences of transcript length variation in different diseases. Emerging evidence reveals coordinated involvement of core RNA processing factors including poly(A) polymerases in the PA-site selection in diseases-associated APAs. Targeting such APA regulators will be therapeutically significant in combating drug resistance in cancer and other complex diseases. This article is categorized under: RNA Processing > 3' End Processing RNA in Disease and Development > RNA in Disease Translation > Regulation.
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Affiliation(s)
- Neeraja K Mohanan
- Cardiovascular and Diabetes Biology Group, Rajiv Gandhi Centre for Biotechnology, Trivandrum, India
- Manipal Academy of Higher Education, Manipal, India
| | - Feba Shaji
- Cardiovascular and Diabetes Biology Group, Rajiv Gandhi Centre for Biotechnology, Trivandrum, India
- Regional Centre for Biotechnology, Faridabad, India
| | - Ganesh R Koshre
- Cardiovascular and Diabetes Biology Group, Rajiv Gandhi Centre for Biotechnology, Trivandrum, India
- Manipal Academy of Higher Education, Manipal, India
| | - Rakesh S Laishram
- Cardiovascular and Diabetes Biology Group, Rajiv Gandhi Centre for Biotechnology, Trivandrum, India
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Mason MA, Gomez-Paredes C, Sathasivam K, Neueder A, Papadopoulou AS, Bates GP. Silencing Srsf6 does not modulate incomplete splicing of the huntingtin gene in Huntington's disease models. Sci Rep 2020; 10:14057. [PMID: 32820193 PMCID: PMC7441155 DOI: 10.1038/s41598-020-71111-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 08/06/2020] [Indexed: 12/31/2022] Open
Abstract
We have previously shown that the incomplete splicing of exon 1 to exon 2 of the HTT gene results in the production of a small polyadenylated transcript (Httexon1) that encodes the highly pathogenic exon 1 HTT protein. There is evidence to suggest that the splicing factor SRSF6 is involved in the mechanism that underlies this aberrant splicing event. Therefore, we set out to test this hypothesis, by manipulating SRSF6 levels in Huntington's disease models in which an expanded CAG repeat had been knocked in to the endogenous Htt gene. We began by generating mice that were knocked out for Srsf6, and demonstrated that reduction of SRSF6 to 50% of wild type levels had no effect on incomplete splicing in zQ175 knockin mice. We found that nullizygosity for Srsf6 was embryonic lethal, and therefore, to decrease SRSF6 levels further, we established mouse embryonic fibroblasts (MEFs) from wild type, zQ175, and zQ175::Srsf6+/- mice and transfected them with an Srsf6 siRNA. The incomplete splicing of Htt was recapitulated in the MEFs and we demonstrated that ablation of SRSF6 did not modulate the levels of the Httexon1 transcript. We conclude that SRSF6 is not required for the incomplete splicing of HTT in Huntington's disease.
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Affiliation(s)
- Michael A Mason
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Casandra Gomez-Paredes
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Kirupa Sathasivam
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Andreas Neueder
- Department of Neurology, Ulm University, 89081, Ulm, Germany
| | - Aikaterini-Smaragdi Papadopoulou
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Gillian P Bates
- Huntington's Disease Centre, Department of Neurodegenerative Disease and UK Dementia Research Institute at UCL, Queen Square Institute of Neurology, University College London, London, WC1N 3BG, UK.
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Tabrizi SJ, Flower MD, Ross CA, Wild EJ. Huntington disease: new insights into molecular pathogenesis and therapeutic opportunities. Nat Rev Neurol 2020; 16:529-546. [PMID: 32796930 DOI: 10.1038/s41582-020-0389-4] [Citation(s) in RCA: 213] [Impact Index Per Article: 53.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/29/2020] [Indexed: 12/11/2022]
Abstract
Huntington disease (HD) is a neurodegenerative disease caused by CAG repeat expansion in the huntingtin gene (HTT) and involves a complex web of pathogenic mechanisms. Mutant HTT (mHTT) disrupts transcription, interferes with immune and mitochondrial function, and is aberrantly modified post-translationally. Evidence suggests that the mHTT RNA is toxic, and at the DNA level, somatic CAG repeat expansion in vulnerable cells influences the disease course. Genome-wide association studies have identified DNA repair pathways as modifiers of somatic instability and disease course in HD and other repeat expansion diseases. In animal models of HD, nucleocytoplasmic transport is disrupted and its restoration is neuroprotective. Novel cerebrospinal fluid (CSF) and plasma biomarkers are among the earliest detectable changes in individuals with premanifest HD and have the sensitivity to detect therapeutic benefit. Therapeutically, the first human trial of an HTT-lowering antisense oligonucleotide successfully, and safely, reduced the CSF concentration of mHTT in individuals with HD. A larger trial, powered to detect clinical efficacy, is underway, along with trials of other HTT-lowering approaches. In this Review, we discuss new insights into the molecular pathogenesis of HD and future therapeutic strategies, including the modulation of DNA repair and targeting the DNA mutation itself.
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Affiliation(s)
- Sarah J Tabrizi
- Huntington's Disease Centre, University College London, London, UK. .,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London, London, UK. .,UK Dementia Research Institute, University College London, London, UK.
| | - Michael D Flower
- Huntington's Disease Centre, University College London, London, UK.,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London, London, UK.,UK Dementia Research Institute, University College London, London, UK
| | - Christopher A Ross
- Departments of Neurology, Neuroscience and Pharmacology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Edward J Wild
- Huntington's Disease Centre, University College London, London, UK.,Department of Neurodegenerative Disease, Queen Square Institute of Neurology, University College London, London, UK
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Extensive Expression Analysis of Htt Transcripts in Brain Regions from the zQ175 HD Mouse Model Using a QuantiGene Multiplex Assay. Sci Rep 2019; 9:16137. [PMID: 31695145 PMCID: PMC6834638 DOI: 10.1038/s41598-019-52411-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 10/14/2019] [Indexed: 11/18/2022] Open
Abstract
Huntington’s disease (HD) is an inherited neurodegenerative disorder caused by a CAG repeat expansion within exon 1 of the huntingtin (HTT) gene. HTT mRNA contains 67 exons and does not always splice between exon 1 and exon 2 leading to the production of a small polyadenylated HTTexon1 transcript, and the full-length HTT mRNA has three 3′UTR isoforms. We have developed a QuantiGene multiplex panel for the simultaneous detection of all of these mouse Htt transcripts directly from tissue lysates and demonstrate that this can replace the more work-intensive Taqman qPCR assays. We have applied this to the analysis of brain regions from the zQ175 HD mouse model and wild type littermates at two months of age. We show that the incomplete splicing of Htt occurs throughout the brain and confirm that this originates from the mutant and not endogenous Htt allele. Given that HTTexon1 encodes the highly pathogenic exon 1 HTT protein, it is essential that the levels of all Htt transcripts can be monitored when evaluating HTT lowering approaches. Our QuantiGene panel will allow the rapid comparative assessment of all Htt transcripts in cell lysates and mouse tissues without the need to first extract RNA.
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Full sequence of mutant huntingtin 3'-untranslated region and modulation of its gene regulatory activity by endogenous microRNA. J Hum Genet 2019; 64:995-1004. [PMID: 31296921 DOI: 10.1038/s10038-019-0639-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 05/02/2019] [Accepted: 06/24/2019] [Indexed: 12/28/2022]
Abstract
Huntington's disease (HD) is caused by an expanded CAG trinucleotide repeat in the first exon of the huntingtin gene (HTT). Since the entire course of the disease starts from this dominant gain-of-function mutation, lowering total or mutant huntingtin mRNA/protein has emerged as an appealing therapeutic strategy. We reasoned that endogenous mechanisms underlying HTT gene regulation may inform strategies to target the source of the disease. As part of our investigation to understand how the expression of HTT is controlled, we performed (1) complete sequencing analysis for mutant HTT 3'-UTR and (2) unbiased screening assays to identify naturally-occurring miRNAs that could lower the HTT mRNA levels. By sequencing HD families inheriting the major European mutant haplotype, we determined the full sequence of HTT 3'-UTRs of the most frequent mutant (i.e., hap.01) and normal (i.e., hap.08) haplotypes, revealing 5 sites with alternative alleles. In subsequent miRNA activity assays using the full-length hap.01 and hap.08 3'-UTR reporter vectors and follow-up validation experiments, hsa-miR-4324 and hsa-miR-4756-5p significantly reduced HTT 3'-UTR reporter activity and endogenous HTT protein levels. However, those miRNAs did not show strong haplotype-specific effects. Nevertheless, our data highlighting full sequences of HTT 3'-UTR haplotypes, effects of miRNAs on HTT levels, and potential interaction sites provide rationale and promising targets for total and mutant-specific HTT lowering intervention strategies using endogenous and artificial miRNAs, respectively.
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Neueder A, Dumas AA, Benjamin AC, Bates GP. Regulatory mechanisms of incomplete huntingtin mRNA splicing. Nat Commun 2018; 9:3955. [PMID: 30262848 PMCID: PMC6160442 DOI: 10.1038/s41467-018-06281-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 08/13/2018] [Indexed: 11/09/2022] Open
Abstract
Huntington’s disease is caused by a CAG repeat expansion in exon 1 of the HTT gene. We have previously shown that exon 1 HTT does not always splice to exon 2 producing a small transcript (HTTexon1) that encodes the highly pathogenic exon 1 HTT protein. The mechanisms by which this incomplete splicing occurs are unknown. Here, we have generated a minigene system that recapitulates the CAG repeat-length dependence of HTTexon1 production, and has allowed us to define the regions of intron 1 necessary for incomplete splicing. We show that manipulation of the expression levels of the splicing factor SRSF6, predicted to bind CAG repeats, modulates this aberrant splicing event and also demonstrate that RNA polymerase II transcription speed regulates the levels of HTTexon1 production. Understanding the mechanisms by which this pathogenic exon 1 HTT is generated may provide the basis for the development of strategies to prevent its production. Incomplete splicing of HTT results in the production of the highly pathogenic exon 1 HTT protein. Here the authors identify the necessary intronic regions and the underlying mechanisms that contribute to this process.
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Affiliation(s)
- Andreas Neueder
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease and Dementia Research Institute, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK. .,Department of Neurology, Ulm University, Ulm, 89081, Germany.
| | - Anaelle A Dumas
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease and Dementia Research Institute, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Agnesska C Benjamin
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease and Dementia Research Institute, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK
| | - Gillian P Bates
- UCL Huntington's Disease Centre, Department of Neurodegenerative Disease and Dementia Research Institute, UCL Institute of Neurology, University College London, London, WC1N 3BG, UK.
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Romo L, Ashar-Patel A, Pfister E, Aronin N. Alterations in mRNA 3' UTR Isoform Abundance Accompany Gene Expression Changes in Human Huntington's Disease Brains. Cell Rep 2018; 20:3057-3070. [PMID: 28954224 DOI: 10.1016/j.celrep.2017.09.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 07/14/2017] [Accepted: 08/31/2017] [Indexed: 02/07/2023] Open
Abstract
The huntingtin gene has two mRNA isoforms that differ in their 3' UTR length. The relationship of these isoforms with Huntington's disease is not established. We provide evidence that the abundance of huntingtin 3' UTR isoforms differs between patient and control neural stem cells, fibroblasts, motor cortex, and cerebellum. Huntingtin 3' UTR isoforms, including a mid-3' UTR isoform, have different localizations, half-lives, polyA tail lengths, microRNA sites, and RNA-binding protein sites. Isoform shifts in Huntington's disease motor cortex are not limited to huntingtin; 11% of alternatively polyadenylated genes change the abundance of their 3' UTR isoforms. Altered expression of RNA-binding proteins may be associated with aberrant isoform abundance; knockdown of the RNA-binding protein CNOT6 in control fibroblasts leads to huntingtin isoform differences similar to those in disease fibroblasts. These findings demonstrate that mRNA 3' UTR isoform changes are a feature of molecular pathology in the Huntington's disease brain.
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Affiliation(s)
- Lindsay Romo
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| | - Ami Ashar-Patel
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Edith Pfister
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Neil Aronin
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA; RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA.
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Dabrowska M, Juzwa W, Krzyzosiak WJ, Olejniczak M. Precise Excision of the CAG Tract from the Huntingtin Gene by Cas9 Nickases. Front Neurosci 2018. [PMID: 29535594 PMCID: PMC5834764 DOI: 10.3389/fnins.2018.00075] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Huntington's disease (HD) is a progressive autosomal dominant neurodegenerative disorder caused by the expansion of CAG repeats in the first exon of the huntingtin gene (HTT). The accumulation of polyglutamine-rich huntingtin proteins affects various cellular functions and causes selective degeneration of neurons in the striatum. Therapeutic strategies used to date to silence the expression of mutant HTT include antisense oligonucleotides, RNA interference-based approaches and, recently, genome editing with the CRISPR/Cas9 system. Here, we demonstrate that the CAG repeat tract can be precisely excised from the HTT gene with the use of the paired Cas9 nickase strategy. As a model, we used HD patient-derived fibroblasts with varied numbers of CAG repeats. The repeat excision inactivated the HTT gene and abrogated huntingtin synthesis in a CAG repeat length-independent manner. Because Cas9 nickases are known to be safe and specific, our approach provides an attractive treatment tool for HD that can be extended to other polyQ disorders.
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Affiliation(s)
- Magdalena Dabrowska
- Department of Genome Engineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Wojciech Juzwa
- Department of Biotechnology and Food Microbiology, Poznan University of Life Sciences, Poznan, Poland
| | - Wlodzimierz J Krzyzosiak
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Marta Olejniczak
- Department of Genome Engineering, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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Abstract
Huntington's disease (HD) is an inherited neurodegenerative disorder caused by a mutation that expands the polyglutamine (CAG) repeat in exon 1 of the huntingtin (HTT) gene. Wild-type HTT protein interacts with other proteins to protect cells against toxic stimuli, mediate vesicle transport and endocytosis, and modulate synaptic activity. Mutant HTT protein disrupts autophagy, vesicle transport, neurotransmitter signaling, and mitochondrial function. Although many of the activities of wild-type HTT protein and the toxicities of mutant HTT protein are characterized, less is known about the activities of HTT mRNA. Most putative HD therapies aim to target mutant HTT mRNA before it is translated into the protein. Therefore, it is imperative to learn as much as we can about how cells handle both wild-type and mutant HTT mRNA so that effective therapies can be designed. Here, we review the structure of wild-type and mutant HTT mRNA, with emphasis on their alternatively polyadenylated or spliced isoforms. We then consider the abundance of HTT mRNA isoforms in HD and discuss the potential implications of these findings. Evidence in the review should be used to guide future research aimed at developing mRNA-lowering therapies for HD.
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Affiliation(s)
- Lindsay Romo
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Emily S. Mohn
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | - Neil Aronin
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA, USA
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA
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Xu H, An JJ, Xu B. Distinct cellular toxicity of two mutant huntingtin mRNA variants due to translation regulation. PLoS One 2017; 12:e0177610. [PMID: 28494017 PMCID: PMC5426682 DOI: 10.1371/journal.pone.0177610] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 04/28/2017] [Indexed: 11/23/2022] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by CAG repeat expansion within exon1 of the HTT gene. The gene generates two mRNA variants that carry either a short or long 3' untranslated region (3'UTR) while encoding the same protein. It remains unknown whether the two mRNA variants play distinct roles in HD pathogenesis. We found that the long HTT 3'UTR was capable of guiding mRNA to neuronal dendrites, suggesting that some long-form HTT mRNA is transported to dendrites for local protein synthesis. To assay roles of two HTT mRNA variants in cell bodies, we expressed mRNA harboring HTT exon1 containing 23x or 145x CAGs with the short or long 3'UTR. We found that mutant mRNA containing the short 3'UTR produced more protein aggregates and caused more apoptosis in both cultured neurons and HEK293 cells, compared with mutant mRNA containing the long 3'UTR. Although the two 3'UTRs did not affect mRNA stability, we detected higher levels of protein synthesis from mRNA containing the short 3'UTR than from mRNA containing the long 3'UTR. These results indicate that the long HTT 3'UTR suppresses translation. Thus, short-form mutant HTT mRNA will be more efficient in producing toxic protein than its long-form counterpart.
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Affiliation(s)
- Haifei Xu
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, Florida, United States of America
| | - Juan Ji An
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, Florida, United States of America
| | - Baoji Xu
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, Florida, United States of America
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Liu W, Pfister EL, Kennington LA, Chase KO, Mueller C, DiFiglia M, Aronin N. Does the Mutant CAG Expansion in Huntingtin mRNA Interfere with Exonucleolytic Cleavage of its First Exon? J Huntingtons Dis 2016; 5:33-8. [PMID: 27003665 PMCID: PMC4816656 DOI: 10.3233/jhd-150183] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Silencing mutant huntingtin mRNA by RNA interference (RNAi) is a therapeutic strategy for Huntington's disease. RNAi induces specific endonucleolytic cleavage of the target HTT mRNA, followed by exonucleolytic processing of the cleaved mRNA fragments. OBJECTIVES We investigated the clearance of huntingtin mRNA cleavage products following RNAi, to find if particular huntingtin mRNA sequences persist. We especially wanted to find out if the expanded CAG increased production of a toxic mRNA species by impeding degradation of human mutant huntingtin exon 1 mRNA. METHODS Mice expressing the human mutant HTT transgene with 128 CAG repeats (YAC128 mice) were injected in the striatum with self-complementary AAV9 vectors carrying a miRNA targeting exon 48 of huntingtin mRNA (scAAV-U6-miRNA-HTT-GFP). Transgenic huntingtin mRNA levels were measured in striatal lysates after two weeks. For qPCR, we used species specific primer-probe combinations that together spanned 6 positions along the open reading frame and untranslated regions of the human huntingtin mRNA. Knockdown was also measured in the liver following tail vein injection. RESULTS Two weeks after intrastriatal administration of scAAV9-U6-miRNA-HTT-GFP, we measured transgenic mutant huntingtin in striatum using probes targeting six different sites along the huntingtin mRNA. Real time PCR showed a reduction of 29% to 36% in human HTT. There was no significant difference in knockdown measured at any of the six sites, including exon 1. In liver, we observed a more pronounced HTT mRNA knockdown of 70% to 76% relative to the untreated mice, and there were also no significant differences among sites. CONCLUSIONS Our results demonstrate that degradation is equally distributed across the human mutant huntingtin mRNA following RNAi-induced cleavage.
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Affiliation(s)
- Wanzhao Liu
- RNA Therapeutics Institute and Department of Medicine, University of
Massachusetts Medical School, Worcester, MA, USA
| | - Edith L. Pfister
- RNA Therapeutics Institute and Department of Medicine, University of
Massachusetts Medical School, Worcester, MA, USA
| | - Lori A. Kennington
- RNA Therapeutics Institute and Department of Medicine, University of
Massachusetts Medical School, Worcester, MA, USA
| | - Kathryn O. Chase
- RNA Therapeutics Institute and Department of Medicine, University of
Massachusetts Medical School, Worcester, MA, USA
| | - Christian Mueller
- Gene Therapy Center, University of Massachusetts Medical School,
Worcester, MA, USA
| | - Marian DiFiglia
- MassGeneral Institute for Neurodegenerative Disease, Massachusetts
General Hospital, Charlestown, MA, USA
| | - Neil Aronin
- RNA Therapeutics Institute and Department of Medicine, University of
Massachusetts Medical School, Worcester, MA, USA
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18
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Idris MM, Thorndyke MC, Brown ER. Evidence for dynamic and multiple roles for huntingtin in Ciona intestinalis. INVERTEBRATE NEUROSCIENCE 2014; 13:151-65. [PMID: 23797324 DOI: 10.1007/s10158-013-0158-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 06/12/2013] [Indexed: 11/29/2022]
Abstract
Although mutations in the huntingtin gene (HTT) due to poly-Q expansion cause neuropathology in humans (Huntington’s disease; HD), the normal function(s) of the gene and its protein (HTT) remain obscure. With new information from recently sequenced invertebrate genomes, the study of new animal models opens the possibility of a better understanding of HTT function and its evolution. To these ends, we studied huntingtin expression pattern and dynamics in the invertebrate chordate Ciona intestinalis. Ciona huntingtin (Ci-HTT) shows a biphasic expression pattern during larval development and prior to metamorphosis. A single form of huntingtin protein is present until the early larval stages, at which time two different mass proteins become evident in the metamorphically competent larva. An antibody against Ci-HTT labeled 50 cells in the trunk mesenchyme regions in pre-hatching and hatched larvae and probably represents the distribution of the light form of the protein. Dual labeling with anti-Ci-HTT and anti-aldoketoreductase confirmed the presence of Ci-HTT in mesenchyme cells. Suppression of Ci-HTT RNA by a morpholino oligonucleotide reduced the number and apparent mobility of Ci-HTT positive cells. In Ciona, HTT expression has a dynamic temporal and spatial expression pattern that in ontogeny precedes metamorphosis. Although our results may reflect a derived function for the protein in pre- and post-metamorphic events in Ciona, we also note that as in vertebrates, there is evidence for multiple differential temporal expression, indicating that this protein probably has multiple roles in ontogeny and cell migration.
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Identification of Novel Alternative Splicing Events in the Huntingtin Gene and Assessment of the Functional Consequences Using Structural Protein Homology Modelling. J Mol Biol 2014; 426:1428-38. [DOI: 10.1016/j.jmb.2013.12.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Revised: 12/23/2013] [Accepted: 12/25/2013] [Indexed: 11/20/2022]
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Abstract
Of the neurodegenerative diseases presented in this book, Huntington's disease (HD) stands as the archetypal autosomal dominantly inherited neurodegenerative disorder. Its occurrence through generations of affected families was noted long before the basic genetic underpinnings of hereditary diseases was understood. The early classification of HD as a distinct hereditary neurodegenerative disorder allowed the study of this disease to lead the way in the development of our understanding of the mechanisms of human genetic disorders. Following its clinical and pathologic characterization, the causative genetic mutation in HD was subsequently identified as a trinucleotide (CAG) repeat expansion in the huntingtin (HTT) gene, and consequently, the HTT gene and huntingtin protein have been studied in great detail. Despite this concentrated effort, there is still much about the function of huntingtin that still remains unknown. Presented in this chapter is an overview of the current knowledge on the normal function of huntingtin and some of the potential neurobiologic mechanisms by which the mutant HTT gene may mediate neurodegeneration in HD.
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Affiliation(s)
- Rebecca A G De Souza
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, Child and Family Research Institute, University of British Columbia, 950 West 28th Avenue, Room 2020, Vancouver, BC, V5Z 4H4, Canada
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Goula AV, Festenstein R, Merienne K. Tissue-dependent regulation of RNAP II dynamics: the missing link between transcription and trinucleotide repeat instability in diseases? Transcription 2013; 4:172-6. [PMID: 23989661 DOI: 10.4161/trns.25971] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
More than 15 human genetic diseases, including Huntington's disease, result from the expansion of a trinucleotide repeat. The expansions are unstable in specific somatic tissues, which can lead to disease acceleration. Here we discuss the role of transcription elongation in tissue-selective trinucleotide repeat instability.
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Affiliation(s)
- Agathi-Vasiliki Goula
- Programme of Translational Medicine and Neurogenetics; Institute of Genetics and Molecular and Cellular Biology (IGBMC); UMR 7104-CNRS/INSERM/UdS; Illkirch, France
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Lee JM, Galkina EI, Levantovsky RM, Fossale E, Anne Anderson M, Gillis T, Srinidhi Mysore J, Coser KR, Shioda T, Zhang B, Furia MD, Derry J, Kohane IS, Seong IS, Wheeler VC, Gusella JF, MacDonald ME. Dominant effects of the Huntington's disease HTT CAG repeat length are captured in gene-expression data sets by a continuous analysis mathematical modeling strategy. Hum Mol Genet 2013; 22:3227-38. [PMID: 23595883 DOI: 10.1093/hmg/ddt176] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In Huntington's disease (HD), the size of the expanded HTT CAG repeat mutation is the primary driver of the processes that determine age at onset of motor symptoms. However, correlation of cellular biochemical parameters also extends across the normal repeat range, supporting the view that the CAG repeat represents a functional polymorphism with dominant effects determined by the longer allele. A central challenge to defining the functional consequences of this single polymorphism is the difficulty of distinguishing its subtle effects from the multitude of other sources of biological variation. We demonstrate that an analytical approach based upon continuous correlation with CAG size was able to capture the modest (∼21%) contribution of the repeat to the variation in genome-wide gene expression in 107 lymphoblastoid cell lines, with alleles ranging from 15 to 92 CAGs. Furthermore, a mathematical model from an iterative strategy yielded predicted CAG repeat lengths that were significantly positively correlated with true CAG allele size and negatively correlated with age at onset of motor symptoms. Genes negatively correlated with repeat size were also enriched in a set of genes whose expression were CAG-correlated in human HD cerebellum. These findings both reveal the relatively small, but detectable impact of variation in the CAG allele in global data in these peripheral cells and provide a strategy for building multi-dimensional data-driven models of the biological network that drives the HD disease process by continuous analysis across allelic panels of neuronal cells vulnerable to the dominant effects of the HTT CAG repeat.
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Affiliation(s)
- Jong-Min Lee
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA.
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Kaplan A, Stockwell BR. Therapeutic approaches to preventing cell death in Huntington disease. Prog Neurobiol 2012; 99:262-80. [PMID: 22967354 PMCID: PMC3505265 DOI: 10.1016/j.pneurobio.2012.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 07/20/2012] [Accepted: 08/17/2012] [Indexed: 12/01/2022]
Abstract
Neurodegenerative diseases affect the lives of millions of patients and their families. Due to the complexity of these diseases and our limited understanding of their pathogenesis, the design of therapeutic agents that can effectively treat these diseases has been challenging. Huntington disease (HD) is one of several neurological disorders with few therapeutic options. HD, like numerous other neurodegenerative diseases, involves extensive neuronal cell loss. One potential strategy to combat HD and other neurodegenerative disorders is to intervene in the execution of neuronal cell death. Inhibiting neuronal cell death pathways may slow the development of neurodegeneration. However, discovering small molecule inhibitors of neuronal cell death remains a significant challenge. Here, we review candidate therapeutic targets controlling cell death mechanisms that have been the focus of research in HD, as well as an emerging strategy that has been applied to developing small molecule inhibitors-fragment-based drug discovery (FBDD). FBDD has been successfully used in both industry and academia to identify selective and potent small molecule inhibitors, with a focus on challenging proteins that are not amenable to traditional high-throughput screening approaches. FBDD has been used to generate potent leads, pre-clinical candidates, and has led to the development of an FDA approved drug. This approach can be valuable for identifying modulators of cell-death-regulating proteins; such compounds may prove to be the key to halting the progression of HD and other neurodegenerative disorders.
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Affiliation(s)
- Anna Kaplan
- Department of Biological Sciences, Columbia University, Northwest Corner Building, MC4846, 550 West 120 Street, New York, NY 10027, USA
| | - Brent R. Stockwell
- Howard Hughes Medical Institute, Columbia University, Northwest Corner Building, MC4846, 550 West 120 Street, New York, NY 10027, USA
- Department of Chemistry, Columbia University, Northwest Corner Building, MC4846, 550 West 120 Street, New York, NY 10027, USA
- Department of Biological Sciences, Columbia University, Northwest Corner Building, MC4846, 550 West 120 Street, New York, NY 10027, USA
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Goula AV, Stys A, Chan JPK, Trottier Y, Festenstein R, Merienne K. Transcription elongation and tissue-specific somatic CAG instability. PLoS Genet 2012; 8:e1003051. [PMID: 23209427 PMCID: PMC3510035 DOI: 10.1371/journal.pgen.1003051] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 09/05/2012] [Indexed: 12/12/2022] Open
Abstract
The expansion of CAG/CTG repeats is responsible for many diseases, including Huntington's disease (HD) and myotonic dystrophy 1. CAG/CTG expansions are unstable in selective somatic tissues, which accelerates disease progression. The mechanisms underlying repeat instability are complex, and it remains unclear whether chromatin structure and/or transcription contribute to somatic CAG/CTG instability in vivo. To address these issues, we investigated the relationship between CAG instability, chromatin structure, and transcription at the HD locus using the R6/1 and R6/2 HD transgenic mouse lines. These mice express a similar transgene, albeit integrated at a different site, and recapitulate HD tissue-specific instability. We show that instability rates are increased in R6/2 tissues as compared to R6/1 matched-samples. High transgene expression levels and chromatin accessibility correlated with the increased CAG instability of R6/2 mice. Transgene mRNA and H3K4 trimethylation at the HD locus were increased, whereas H3K9 dimethylation was reduced in R6/2 tissues relative to R6/1 matched-tissues. However, the levels of transgene expression and these specific histone marks were similar in the striatum and cerebellum, two tissues showing very different CAG instability levels, irrespective of mouse line. Interestingly, the levels of elongating RNA Pol II at the HD locus, but not the initiating form of RNA Pol II, were tissue-specific and correlated with CAG instability levels. Similarly, H3K36 trimethylation, a mark associated with transcription elongation, was specifically increased at the HD locus in the striatum and not in the cerebellum. Together, our data support the view that transcription modulates somatic CAG instability in vivo. More specifically, our results suggest for the first time that transcription elongation is regulated in a tissue-dependent manner, contributing to tissue-selective CAG instability.
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Affiliation(s)
- Agathi-Vasiliki Goula
- Programme of Translational Medicine and Neurogenetics, Institute of Genetics and Molecular and Cellular Biology (IGBMC), UMR 7104-CNRS/INSERM/UdS, Illkirch, France
| | - Agnieszka Stys
- Programme of Translational Medicine and Neurogenetics, Institute of Genetics and Molecular and Cellular Biology (IGBMC), UMR 7104-CNRS/INSERM/UdS, Illkirch, France
| | - Jackson P. K. Chan
- Department of Medicine, Imperial College London, Hammersmith Hospital Campus, London, United Kingdom
| | - Yvon Trottier
- Programme of Translational Medicine and Neurogenetics, Institute of Genetics and Molecular and Cellular Biology (IGBMC), UMR 7104-CNRS/INSERM/UdS, Illkirch, France
| | - Richard Festenstein
- Department of Medicine, Imperial College London, Hammersmith Hospital Campus, London, United Kingdom
| | - Karine Merienne
- Programme of Translational Medicine and Neurogenetics, Institute of Genetics and Molecular and Cellular Biology (IGBMC), UMR 7104-CNRS/INSERM/UdS, Illkirch, France
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Huntington disease and the huntingtin protein. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 107:189-214. [PMID: 22482451 DOI: 10.1016/b978-0-12-385883-2.00010-2] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Huntington disease (HD) is a devastating neurodegenerative disease that derives from CAG repeat expansion in the huntingtin gene. The clinical syndrome consists of progressive personality changes, movement disorder, and dementia and can develop in children and adults. The huntingtin protein is required for human development and normal brain function. It is subject to posttranslational modification, and some events, such as phosphorylation, can play an enormous role in regulating toxicity of the huntingtin protein. The function of huntingtin in the cell is unknown, and it may play a role as a scaffold. Multiple mouse models of HD have now been created with fragments and full-length protein. The models show variable fidelity to the disease in terms of genetics, pathology, and rates of progression. Pathogenesis of HD involves cleavage of the protein and is associated with neuronal accumulation of aggregated forms. The potential mechanisms of neurodegeneration are myriad, including primary effects of protein homeostasis, gene expression, and mitochondrial dysfunction. Specific therapeutic approaches are similarly varied and include efforts to reduce huntingtin gene expression, protein accumulation, and protein aggregation.
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Giacomello M, Hudec R, Lopreiato R. Huntington's disease, calcium, and mitochondria. Biofactors 2011; 37:206-18. [PMID: 21674644 DOI: 10.1002/biof.162] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Accepted: 03/23/2011] [Indexed: 01/13/2023]
Abstract
Huntington's disease (HD) is caused by a mutation that increases the number of CAG repeats in the gene encoding for the protein Huntingtin (Htt). The mutation results in the pathological expansion of the polyQ stretch that is normally present within the N-terminal region of Htt. Even if Htt is ubiquitously expressed in tissues, the changes in the protein finally result in the clinical manifestation of motor and cognitive impairments observed in HD patients. The molecular ethiology of the disease is obscure: a number of cellular and animal models are used as essential tools in experimental approaches aimed at understanding it. Biochemical changes have been described that correlate with the malfunction of HD neurons (primarily in the striatum): consensus is gradually emerging that the dyshomeostasis of Ca(2+) and/or mitochondria stress are important factors in the linkage of the Htt mutation to the onset and progression of the disease. Here, we present a succint overview of the changes of Htt, of its possible effect on the transcription of critical genes and of its causative role in the disturbance of the neuronal Ca(2+) homeostasis. Particular emphasis will be placed on the role of mitochondria as key player in the molecular pathogenesis of the disease.
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Abstract
It has been more than 17 years since the causative mutation for Huntington's disease was discovered as the expansion of the triplet repeat in the N-terminal portion of the Huntingtin (HTT) gene. In the intervening time, researchers have discovered a great deal about Huntingtin's involvement in a number of cellular processes. However, the role of Huntingtin in the key pathogenic mechanism leading to neurodegeneration in the disease process has yet to be discovered. Here, we review the body of knowledge that has been uncovered since gene discovery and include discussions of the HTT gene, CAG triplet repeat expansion, HTT expression, protein features, posttranslational modifications, and many of its known protein functions and interactions. We also highlight potential pathogenic mechanisms that have come to light in recent years.
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Affiliation(s)
- Karen N McFarland
- Department of Neurology, University of Florida, Gainesville, FL 32610-0236, USA.
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Zuccato C, Valenza M, Cattaneo E. Molecular Mechanisms and Potential Therapeutical Targets in Huntington's Disease. Physiol Rev 2010; 90:905-81. [DOI: 10.1152/physrev.00041.2009] [Citation(s) in RCA: 626] [Impact Index Per Article: 44.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the gene encoding for huntingtin protein. A lot has been learned about this disease since its first description in 1872 and the identification of its causative gene and mutation in 1993. We now know that the disease is characterized by several molecular and cellular abnormalities whose precise timing and relative roles in pathogenesis have yet to be understood. HD is triggered by the mutant protein, and both gain-of-function (of the mutant protein) and loss-of-function (of the normal protein) mechanisms are involved. Here we review the data that describe the emergence of the ancient huntingtin gene and of the polyglutamine trait during the last 800 million years of evolution. We focus on the known functions of wild-type huntingtin that are fundamental for the survival and functioning of the brain neurons that predominantly degenerate in HD. We summarize data indicating how the loss of these beneficial activities reduces the ability of these neurons to survive. We also review the different mechanisms by which the mutation in huntingtin causes toxicity. This may arise both from cell-autonomous processes and dysfunction of neuronal circuitries. We then focus on novel therapeutical targets and pathways and on the attractive option to counteract HD at its primary source, i.e., by blocking the production of the mutant protein. Strategies and technologies used to screen for candidate HD biomarkers and their potential application are presented. Furthermore, we discuss the opportunities offered by intracerebral cell transplantation and the likely need for these multiple routes into therapies to converge at some point as, ideally, one would wish to stop the disease process and, at the same time, possibly replace the damaged neurons.
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Affiliation(s)
- Chiara Zuccato
- Department of Pharmacological Sciences and Centre for Stem Cell Research, Università degli Studi di Milano, Milan, Italy
| | - Marta Valenza
- Department of Pharmacological Sciences and Centre for Stem Cell Research, Università degli Studi di Milano, Milan, Italy
| | - Elena Cattaneo
- Department of Pharmacological Sciences and Centre for Stem Cell Research, Università degli Studi di Milano, Milan, Italy
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Ehrnhoefer DE, Butland SL, Pouladi MA, Hayden MR. Mouse models of Huntington disease: variations on a theme. Dis Model Mech 2009; 2:123-9. [PMID: 19259385 DOI: 10.1242/dmm.002451] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
An accepted prerequisite for clinical trials of a compound in humans is the successful alleviation of the disease in animal models. For some diseases, however, successful translation of drug effects from mouse models to the bedside has been limited. One question is whether the current models accurately reproduce the human disease. Here, we examine the mouse models that are available for therapeutic testing in Huntington disease (HD), a late-onset neurodegenerative disorder for which there is no effective treatment. The current mouse models show different degrees of similarity to the human condition. Significant phenotypic differences are seen in mouse models that express either truncated or full-length human, or full-length mouse, mutant huntingtin (mHTT). These differences in phenotypic expression may be attributable to the influences of protein context, mouse strain and a difference in regulatory sequences between the mouse Htt and human HTT genes.
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Affiliation(s)
- Dagmar E Ehrnhoefer
- Centre for Molecular Medicine and Therapeutics, Department of Medical Genetics, Child and Family Research Institute, University of British Columbia, Vancouver, Canada
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Ghosh T, Soni K, Scaria V, Halimani M, Bhattacharjee C, Pillai B. MicroRNA-mediated up-regulation of an alternatively polyadenylated variant of the mouse cytoplasmic {beta}-actin gene. Nucleic Acids Res 2008; 36:6318-32. [PMID: 18835850 PMCID: PMC2577349 DOI: 10.1093/nar/gkn624] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Actin is a major cytoskeletal protein in eukaryotes. Recent studies suggest more diverse functional roles for this protein. Actin mRNA is known to be localized to neuronal synapses and undergoes rapid deadenylation during early developmental stages. However, its 3′-untranslated region (UTR) is not characterized and there are no experimentally determined polyadenylation (polyA) sites in actin mRNA. We have found that the cytoplasmic β-actin (Actb) gene generates two alternative transcripts terminated at tandem polyA sites. We used 3′-RACE, EST end analysis and in situ hybridization to unambiguously establish the existence of two 3′-UTRs of varying length in Actb transcript in mouse neuronal cells. Further analyses showed that these two tandem polyA sites are used in a tissue-specific manner. Although the longer 3′-UTR was expressed at a relatively lower level, it conferred higher translational efficiency to the transcript. The longer transcript harbours a conserved mmu-miR-34a/34b-5p target site. Sequence-specific anti-miRNA molecule, mutations of the miRNA target region in the 3′-UTR resulted in reduced expression. The expression was restored by a mutant miRNA complementary to the mutated target region implying that miR-34 binding to Actb 3′-UTR up-regulates target gene expression. Heterogeneity of the Actb 3′-UTR could shed light on the mechanism of miRNA-mediated regulation of messages in neuronal cells.
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Affiliation(s)
- Tanay Ghosh
- Institute of Genomics and Integrative Biology (IGIB), Mall Road, New Delhi 110007, India
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Abstract
Cytoplasmic polyadenylation regulates mRNA stability and translation and is required for early development and synaptic plasticity. The GLD-2 poly(A) polymerase catalyzes cytoplasmic polyadenylation in the germline of metazoa. Among vertebrates, the enzyme is encoded by two isoforms of mRNA that differ only in the length of their 3'-UTRs. Here we focus on regulation of vertebrate GLD-2 mRNA. We show that the 3'-UTR of GLD-2 mRNA elicits its own polyadenylation and translational activation during frog oocyte maturation. We identify the sequence elements responsible for repression and activation, and demonstrate that CPEB and PUF proteins likely mediate repression in the resting oocyte. Regulated polyadenylation of GLD-2 mRNA is conserved, as are the key regulatory elements. Poly(A) tails of GLD-2 mRNA increase in length in the brain in response to neuronal stimulation, suggesting that a comparable system exists in that tissue. We propose a positive feedback circuit in which translation of GLD-2 mRNA is stimulated by its polyadenylation, thereby reinforcing the switch to polyadenylate and activate batteries of mRNAs.
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Affiliation(s)
- Labib Rouhana
- Department of Biochemistry, Laboratory of Genetics, University of Wisconsin-Madison 53706, USA
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Huntingtin gene evolution in Chordata and its peculiar features in the ascidian Ciona genus. BMC Genomics 2006; 7:288. [PMID: 17092333 PMCID: PMC1636649 DOI: 10.1186/1471-2164-7-288] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Accepted: 11/08/2006] [Indexed: 01/20/2023] Open
Abstract
Background To gain insight into the evolutionary features of the huntingtin (htt) gene in Chordata, we have sequenced and characterized the full-length htt mRNA in the ascidian Ciona intestinalis, a basal chordate emerging as new invertebrate model organism. Moreover, taking advantage of the availability of genomic and EST sequences, the htt gene structure of a number of chordate species, including the cogeneric ascidian Ciona savignyi, and the vertebrates Xenopus and Gallus was reconstructed. Results The C. intestinalis htt transcript exhibits some peculiar features, such as spliced leader trans-splicing in the 98 nt-long 5' untranslated region (UTR), an alternative splicing in the coding region, eight alternative polyadenylation sites, and no similarities of both 5' and 3'UTRs compared to homologs of the cogeneric C. savignyi. The predicted protein is 2946 amino acids long, shorter than its vertebrate homologs, and lacks the polyQ and the polyP stretches found in the the N-terminal regions of mammalian homologs. The exon-intron organization of the htt gene is almost identical among vertebrates, and significantly conserved between Ciona and vertebrates, allowing us to hypothesize an ancestral chordate gene consisting of at least 40 coding exons. Conclusion During chordate diversification, events of gain/loss, sliding, phase changes, and expansion of introns occurred in both vertebrate and ascidian lineages predominantly in the 5'-half of the htt gene, where there is also evidence of lineage-specific evolutionary dynamics in vertebrates. On the contrary, the 3'-half of the gene is highly conserved in all chordates at the level of both gene structure and protein sequence. Between the two Ciona species, a fast evolutionary rate and/or an early divergence time is suggested by the absence of significant similarity between UTRs, protein divergence comparable to that observed between mammals and fishes, and different distribution of repetitive elements.
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Chen ZJ, Kren BT, Wong PYP, Low WC, Steer CJ. Sleeping Beauty-mediated down-regulation of huntingtin expression by RNA interference. Biochem Biophys Res Commun 2005; 329:646-52. [PMID: 15737634 DOI: 10.1016/j.bbrc.2005.02.024] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2004] [Indexed: 11/25/2022]
Abstract
Huntington disease (HD) is a devastating neurologic disorder that is characterized by abnormal expansion of a CAG nt repeat in the first exon of the huntingtin (htt) gene, producing a mutant protein with an elongated polyglutamine stretch. The presence of this mutant protein is correlated with the characteristic loss of striatal neurons and the clinical manifestation of HD. Currently there is no effective treatment for the associated cell death. The aim of this study was to evaluate an innovative strategy combining RNA interference (RNAi) and gene transfer via the nonviral Sleeping Beauty (SB) transposon system to down-regulate Htt expression. siRNA expression vectors were designed to target exons 1, 4, 6, and 62 of the human htt gene. Real-time RT-PCR and Western blot analysis were used to quantify Htt mRNA and protein levels, respectively, in human cell lines. The results indicated that selected siRNA constructs significantly decreased Htt mRNA and protein levels relative to controls. In addition, SB transposition of the siRNA constructs into the genome reduced long-term protein expression of Htt by approximately 90%. The combination of siRNA, the SB transposon, and an accurate transgenic mouse model may permit evaluation of this approach in preventing the pathogenesis associated with expression of mutant Htt.
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Affiliation(s)
- Zongyu J Chen
- Department of Medicine, University of Minnesota Medical School, Minneapolis, MN 55455, USA
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Kumar U. Differential expression of Huntington's disease gene (IT15) mRNA in developing rat brain. ACTA ACUST UNITED AC 2005; 128:39-47. [PMID: 15337316 DOI: 10.1016/j.molbrainres.2004.06.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/07/2004] [Indexed: 10/26/2022]
Abstract
Huntington's disease (HD) is an autosomal dominant inheritance neurological disorder associated with CAG repeats expansions within a widely distributed gene that causes selective neuronal death. The gene is essential for normal development and has been suggested for its role in the development of basal ganglia. To understand its normal function during growth and development, we determined the expression patterns for the gene responsible for HD (IT15) mRNA by Northern blot analysis in the developing and adult rat brain. In adult rat brains, IT15 transcripts exist as two isoforms of 10 and 12.5 kb each, which display distinct expression patterns. IT15 mRNA expression is already highly expressed within 1 day of birth. Expression signals for IT15 were first detected at embryonic day 16 or 17 during prenatal development. IT15 transcript peaks leveled around day 20 postnatally and thereafter decreased to levels typically found in adults. In the adult rat brain, mRNA expression was highest in the cerebellum followed by the cortex, striatum, hippocampus and olfactory lobe. In the medulla and the spinal cord, IT15 was weakly expressed in comparison to the other regions studied. Thus, the distinct expression patterns provide a basis for its functional significance during development. These results also suggest that the degree of IT15 mRNA expression is related to the neuronal population in different brain regions.
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Affiliation(s)
- Ujendra Kumar
- Fraser Laboratories For Diabetes Research, Department of Medicine, McGill University, Royal Victoria Hospital, Room M3-15, 687 Pine Avenue West, Montreal, Quebec, H3A 1A1, Canada.
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Beck K, Hayashi K, Nishiguchi B, Le Saux O, Hayashi M, Boyd CD. The distribution of Abcc6 in normal mouse tissues suggests multiple functions for this ABC transporter. J Histochem Cytochem 2003; 51:887-902. [PMID: 12810839 DOI: 10.1177/002215540305100704] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We have studied the tissue distribution of Abcc6, a member of the ABC transmembrane transporter subfamily C, in normal C57BL/6 mice. RNase protection assays revealed that although almost all tissues studied contained detectable levels of the mRNA encoding Abcc6, the highest levels of Abcc6 mRNA were found in the liver. In situ hybridization (ISH) demonstrated abundant Abcc6 mRNA in epithelial cells from a variety of tissues, including hepatic parenchymal cells, bile duct epithelia, kidney proximal tubules, mucosa and gland cells of the stomach, intestine, and colon, squamous epithelium of the tongue, corneal epithelium of the eye, keratinocytes of the skin, and tracheal and bronchial epithelium. Furthermore, we detected Abcc6 mRNA in arterial endothelial cells, smooth muscle cells of the aorta and myocardium, in circulating leukocytes, lymphocytes in the thymus and lymph nodes, and in neurons of the brain, spinal cord, and the specialized neurons of the retina. Immunohistochemical analysis using a polyclonal Abcc6 rabbit antibody confirmed the tissue distribution of Abcc6 suggested by our ISH studies and revealed the cellular localization of Abcc6 in the basolateral plasma membrane in the epithelial cells of proximal convoluted tubules in the kidney. Although the function of Abcc6 is unknown, mutations in the human ABCC6 gene result in a heritable disorder of connective tissue called pseudoxanthoma elasticum (PXE). Our results demonstrating the presence of Abcc6 in epithelial and endothelial cells in a variety of tissues, including those tissues affected in PXE patients, suggest a possible role for Abcc6 in the normal assembly of extracellular matrix components. However, the presence of Abcc6 in neurons and leukocytes, two cell populations not associated with connective tissue, also suggests a more complex multifunctional role for Abcc6.
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Affiliation(s)
- Konstanze Beck
- Lab of Matrix Pathobiology, The Pacific Biomedical Research Center, University of Hawai'i, 1993 East-West Road, Honolulu, HI 96822, USA
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36
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Abstract
A milestone in Huntington's disease (HD) research is represented by the identification of the causative gene. With the genetics at hand, a series of transgenic cellular and animal models has been developed, which has greatly contributed to understanding of HD. All these models are described in this review, and are compared to each other, along with the information they have generated. Although the mechanism by which progressive loss of striatal neurons occurs in HD remains uncertain, hypotheses on mutant huntingtin toxicity involve impaired vescicular trafficking, transcriptional dysregulation, and/or activation of apoptotic pathways. The development of inducible HD mice has shown that neurodegeneration in HD may be at least partially blocked. Although traditionally considered a "gain-of-function" disease, the recent finding that normal huntingtin has an important role in neuronal survival suggests that loss of function of the normal protein might contribute to HD as well, also discloseing new perspectives on the therapeutical approach to the pathology.
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Affiliation(s)
- S Sipione
- Department of Pharmacological Sciences, University of Milano, Center of Excellence on Neurodegenerative Diseases, Italy
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37
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Raskin S, Allan N, Teive HA, Cardoso F, Haddad MS, Levi G, Boy R, Lerena Junior J, Sotomaior VS, Janzen-Dück M, Jardim LB, Fellander FR, Andrade LA. Huntington disease: DNA analysis in Brazilian population. ARQUIVOS DE NEURO-PSIQUIATRIA 2000; 58:977-85. [PMID: 11105061 DOI: 10.1590/s0004-282x2000000600001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Huntington disease (HD) is associated with expansions of a CAG trinucleotide repeat in the HD gene. Accurate measurement of a specific CAG repeat sequence in the HD gene in 92 Brazilian controls without HD, 44 Brazilian subjects with clinical findings suggestive of HD and 40 individuals from 6 putative HD families, showed a range from 7 to 33 repeats in normal subjects and 39 to 88 repeats in affected subjects. A trend between early age at onset of first symptoms and increasing number of repeats was seen. Major increase of repeat size through paternal inheritance than through maternal inheritance was observed. Data generated from this study may have significant implications for the etiology, knowledge of the incidence, diagnosis, prognosis, genetic counseling and treatment of HD Brazilian patients.
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Affiliation(s)
- S Raskin
- Centro deAconselhamento e Laboratório Genetika-Curitiba, PR, Brazil
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38
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Matsuyama N, Hadano S, Onoe K, Osuga H, Showguchi-Miyata J, Gondo Y, Ikeda JE. Identification and characterization of the miniature pig Huntington's disease gene homolog: evidence for conservation and polymorphism in the CAG triplet repeat. Genomics 2000; 69:72-85. [PMID: 11013077 DOI: 10.1006/geno.2000.6317] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Huntington's disease (HD) is associated with a significant expansion of a CAG trinucleotide repeat, which results in a lengthened polyglutamine tract in the single gene product, huntingtin, on human 4p16.3. We isolated cDNA clones that encompassed the entire coding sequence of the miniature pig HD gene (Sus HD) from two porcine testis cDNA libraries. The cDNA contig revealed a 12,749-nucleotide transcript coding for a 345-kDa protein (3139 amino acid residues), which exhibited 96% peptide sequence homology to human huntingtin. Northern blot analysis revealed that the Sus HD gene was ubiquitously expressed as two large transcripts of approximately 11 and 13 kb in size in all the tested tissues, much like the human HD gene. The CAG trinucleotide repeat was found to be interrupted by CAA triplets and to encode 17 or 18 consecutive glutamine residues. In our laboratory stock of miniature pig, three allotypes in the triplet repeat sequence were found. Thus, the Sus HD gene closely resembles its human counterpart in terms of sequence and expression pattern. In particular, human-miniature pig similarities in the normal length of the CAG triplet repeat as well as its repeat-number polymorphism may indicate that miniature pig would provide a good animal model for Huntington's disease.
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Affiliation(s)
- N Matsuyama
- Department of Neurobiology, SLA Research, Inc., Bohseidai, Isehara, Kanagawa, Japan
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39
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Mangiarini L, Sathasivam K, Bates GP. Molecular Pathology of Huntington's Disease: Animal Models and Nuclear Mechanisms. Neuroscientist 1999. [DOI: 10.1177/107385849900500613] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Huntington's disease (HD) is a late-onset neurodegenerative disorder caused by a polyglutamine expansion in huntingtin, a protein of unknown function. Transgenic models expressing a portion or full-length human huntingtin have been generated to unravel the mechanism through which the mutation causes the symptoms and the selective cell death characteristic of HD. We review here advances in the understanding of HD made possible by transgenic models and the means by which they implicate polyglutamine aggregation in the pathology of triplet repeat disorders.
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Affiliation(s)
- Laura Mangiarini
- Medical and Molecular Genetics GKT School of Medicine King's College Guy's Hospital London, UK
| | - Kirupa Sathasivam
- Medical and Molecular Genetics GKT School of Medicine King's College Guy's Hospital London, UK
| | - Gillian P. Bates
- Medical and Molecular Genetics GKT School of Medicine King's College Guy's Hospital London, UK
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40
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Li Z, Karlovich CA, Fish MP, Scott MP, Myers RM. A putative Drosophila homolog of the Huntington's disease gene. Hum Mol Genet 1999; 8:1807-15. [PMID: 10441347 DOI: 10.1093/hmg/8.9.1807] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Huntington's disease (HD) gene encodes a protein, huntingtin, with no known function and no detectable sequence similarity to other proteins in current databases. To gain insight into the normal biological role of huntingtin, we isolated and sequenced a cDNA encoding a protein that is a likely homolog of the HD gene product in Drosophila melanogaster. We also determined the complete sequence of 43 125 contiguous base pairs of genomic DNA that encompass the Drosophila HD gene, allowing the intron-exon structure and 5'- and 3'-flanking regions to be delineated. The predicted Drosophila huntingtin protein has 3583 amino acids, which is several hundred amino acids larger than any other previously characterized member of the HD family. Analysis of the genomic and cDNA sequences indicates that Drosophila HD has 29 exons, compared with the 67 exons present in vertebrate HD genes, and that Drosophila huntingtin lacks the polyglutamine and polyproline stretches present in its mammalian counterparts. The Drosophila HD mRNA is expressed in a broad range of developmental stages and in the adult, a temporal pattern of expression similar to that observed for mammalian HD transcripts. We can discern five regions of high similarity from multiple sequence alignments between Drosophila and vertebrate huntingtins. These regions may define functionally important domains within the protein.
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Affiliation(s)
- Z Li
- Department of Genetics, Stanford University School of Medicine, CA 94305-5120, USA
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41
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Hebb MO, Denovan-Wright EM, Robertson HA. Expression of the Huntington's disease gene is regulated in astrocytes in the arcuate nucleus of the hypothalamus of postpartum rats. FASEB J 1999; 13:1099-106. [PMID: 10336893 DOI: 10.1096/fasebj.13.9.1099] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Huntington's disease (HD) is one of a number of neurodegenerative disorders caused by expansion of polyglutamine-encoding CAG repeats within specific genes. Huntingtin, the protein product of the HD gene, is widely expressed in neural and nonneural human and rodent tissue. The function of the wild-type or mutated form of huntingtin is currently unknown. We have observed that relative to naive and male animals, huntingtin protein was significantly increased in the arcuate nucleus of postpartum rats. Using an oligonucleotide probe, in situ and Northern blot hybridization confirmed the expression of huntingtin mRNA. Quantification of the in situ hybridization signal in the arcuate nucleus revealed an approximate sevenfold increase in the expression of huntingtin mRNA in postpartum, lactating animals compared with naive female or male animals. Emulsion autoradiography and immunohistochemistry revealed that the cells with elevated huntingtin expression had a stellate conformation that morphologically resembled astrocytes. Dual label immunofluorescence immunohistochemistry demonstrated the colocalization of huntingtin and glial fibrillary acidic protein in these cells, confirming that they were astrocytes. Astrocytes expressing huntingtin were consistently found in close apposition to neuronal soma, suggesting interactions between these cell types. During the perinatal and postnatal period, the hypothalamus undergoes alterations in metabolic function. Our results support the idea of glia-induced metabolic changes in the hypothalamus. These results provide the first demonstration of naturally occurring changes in the expression of the Huntington's disease gene in the brain and suggest that huntingtin may play an important role in the processes that regulate neuroendocrine function.
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Affiliation(s)
- M O Hebb
- Laboratory of Molecular Neurobiology, Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
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42
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Syed V, Gomez E, Hecht NB. mRNAs encoding a von Ebner's-like protein and the Huntington disease protein are induced in rat male germ cells by Sertoli cells. J Biol Chem 1999; 274:10737-42. [PMID: 10196145 DOI: 10.1074/jbc.274.16.10737] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The success of spermatogenesis is dependent upon closely coordinated interactions between Sertoli cells and germ cells. To identify specific molecules that mediate interactions between somatic cells and germ cells in the rat testis, Sertoli cell-germ cell co-cultures and mRNA differential display were used. Two cDNAs, clone 1 (660 nucleotides) and clone 2 (390 nucleotides) were up-regulated when Sertoli cells were co-cultured with pachytene spermatocytes or round spermatids. Northern blot analyses confirmed the differential display expression patterns. Sequence analyses indicated that clone 1 was similar to a von Ebner's gland protein (87% at the nucleotide level and 80% at the amino acid level) and clone 2 was identical to a region of the Huntington disease protein. The von Ebner's-like protein mRNA was induced after 4 h of co-culture, while the Huntington disease protein required 18 h of co-culture for expression. The von Ebner's-like protein was induced in germ cells by a secreted Sertoli cell factor(s) smaller than 10 kDa that is sensitive to freezing and thawing or boiling. The Huntington disease protein was induced in germ cells by a Sertoli cell secreted factor(s) larger than 10 kDa which survives freezing and thawing, but is inactivated by boiling.
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Affiliation(s)
- V Syed
- Center for Research on Reproduction and Women's Health and Department of Obstetrics and Gynecology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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43
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Ross CA, Margolis RL, Becher MW, Wood JD, Engelender S, Cooper JK, Sharp AH. Pathogenesis of neurodegenerative diseases associated with expanded glutamine repeats: new answers, new questions. PROGRESS IN BRAIN RESEARCH 1999; 117:397-419. [PMID: 9932422 DOI: 10.1016/s0079-6123(08)64029-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Eight diseases are now known to be caused by an expansion mutation of the trinucleotide repeat CAG encoding glutamine. Each disease is caused by a CAG expansion in a different gene, and the genes bear no similarity to each other except for the presence of the repeat. Nonetheless, the essential feature of all of these disorders is neurodegeneration in a set of overlapping cortical and subcortical regions. Disease age of onset, and in some cases severity, is correlated with repeat length. These and other observations have led to the hypothesis that CAG expansion causes disease by a toxic gain-of-function of the encoded stretch of polyglutamine residues. Expansion-induced abnormalities of cytoskeletal function or neuronal signalling processes may contribute to the pathogenic process. In addition, theoretical and experimental analysis of the chemistry of uninterrupted stretches of glutamine residues suggest that polyglutamine-containing proteins or protein fragments may aggregate, via a "polar zipper", into beta pleated sheets. Recent findings have now established the presence of such aggregates in selected regions of brain from affected individuals, in transgenic mice expressing expanded repeats, and in isolated cells transfected with expanded repeats. The aggregates are most prominently manifest as neuronal intranuclear inclusion bodies. As the investigation of the link between these inclusions and cell dysfunction and death continues, it is possible that new avenues for therapeutic intervention will emerge.
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Affiliation(s)
- C A Ross
- Johns Hopkins University, School of Medicine, Department of Psychiatry, Baltimore, Maryland 21205-2196, USA.
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44
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Karlovich CA, John RM, Ramirez L, Stainier DY, Myers RM. Characterization of the Huntington's disease (HD) gene homologue in the zebrafish Danio rerio. Gene 1998; 217:117-25. [PMID: 9795179 DOI: 10.1016/s0378-1119(98)00342-4] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
The Huntington's disease (HD) gene contains a trinucleotide repeat that is expanded and unstable in patients with the disease (HDCRG, 1993). As the first step toward investigating a potential role for this gene in early vertebrate development, we isolated the homolog of the Huntington's disease (ZHD) cDNA in zebrafish. This cDNA encodes a predicted protein product of 3121 amino acids with 70% identity to human huntingtin. The first exon is predicted to encode four glutamines, followed by only one proline, demonstrating that the polymorphic polyproline stretch found in mammalian HD sequences is absent in the fish. We sequenced approximately 900bp upstream from the predicted start codon and found that it lacks a TATA box, CCAAT box, or Sp1 binding sites. Western blot analysis revealed that the protein is expressed at a high level in late embryonic development and at moderate levels in the adult head.
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Affiliation(s)
- C A Karlovich
- Department of Genetics, School of Medicine Rm. M344, 300 Pasteur Dr., Stanford University, Stanford, CA 94305, USA
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45
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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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46
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Goldmuntz E, Fedon J, Roe B, Budarf ML. Molecular characterization of a serine/threonine kinase in the DiGeorge minimal critical region. Gene X 1997; 198:379-86. [PMID: 9370305 DOI: 10.1016/s0378-1119(97)00341-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The majority of patients with DiGeorge, velocardiofacial or conotruncal anomaly facial syndromes share a common genetic etiology, deletion of chromosomal region 22q11.2. This report describes a computational approach toward the identification and molecular characterization of a newly identified serine/threonine kinase from the minimal critical deleted region (MDGCR). A cosmid contig of the minimal critical region has been assembled and sequenced in its entirety. Database searches and computer analysis of one cosmid (111f11) for coding sequences identified two regions with high similarity to the mouse serine/threonine kinase, Tsk1. Our investigations demonstrate that one of these regions contains a testis-specific gene that undergoes differential splicing, while the other region is most likely a pseudogene. Northern blot analysis and cDNA cloning demonstrate that there is alternate processing of the 3'UTR without altering the conserved kinase domains within the open reading frame. Serine/threonine kinases can play a regulatory role and have been found to be expressed during early embryogenesis. Based on its position in the MDGCR and possible function, the gene reported here is a candidate for the features seen in the 22q11 deletion syndrome.
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Affiliation(s)
- E Goldmuntz
- The Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, The Department of Pediatrics, 19104, USA.
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47
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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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48
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Gallagher PG, Tse WT, Scarpa AL, Lux SE, Forget BG. Structure and organization of the human ankyrin-1 gene. Basis for complexity of pre-mRNA processing. J Biol Chem 1997; 272:19220-8. [PMID: 9235914 DOI: 10.1074/jbc.272.31.19220] [Citation(s) in RCA: 58] [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
Ankyrin-1 (ANK-1) is an erythrocyte membrane protein that is defective in many patients with hereditary spherocytosis, a common hemolytic anemia. In the red cell, ankyrin-1 provides the primary linkage between the membrane skeleton and the plasma membrane. To gain additional insight into the structure and function of this protein and to provide the necessary tools for further genetic studies of hereditary spherocytosis patients, we cloned the human ANK-1 chromosomal gene. Characterization of the ANK-1 gene genomic structure revealed that the erythroid transcript is composed of 42 exons distributed over approximately 160 kilobase pairs of DNA. Comparison of the genomic structure with the protein domains reveals a near-absolute correlation between the tandem repeats encoding the membrane-binding domain of ankyrin with the location of the intron/exon boundaries in the corresponding part of the gene. Erythroid stage-specific, complex patterns of alternative splicing were identified in the region encoding the regulatory domain of ankyrin-1. Novel brain-specific transcripts were also identified in this region, as well as in the "hinge" region between the membrane-binding and spectrin-binding domains. Utilization of alternative polyadenylation signals was found to be the basis for the previously described, stage-specific 9.0- and 7.2-kilobase pair transcripts of the ANK-1 gene.
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Affiliation(s)
- P G Gallagher
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
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49
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Edwalds-Gilbert G, Veraldi KL, Milcarek C. Alternative poly(A) site selection in complex transcription units: means to an end? Nucleic Acids Res 1997; 25:2547-61. [PMID: 9185563 PMCID: PMC146782 DOI: 10.1093/nar/25.13.2547] [Citation(s) in RCA: 410] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Many genes have been described and characterized which result in alternative polyadenylation site use at the 3'-end of their mRNAs based on the cellular environment. In this survey and summary article 95 genes are discussed in which alternative polyadenylation is a consequence of tandem arrays of poly(A) signals within a single 3'-untranslated region. An additional 31 genes are described in which polyadenylation at a promoter-proximal site competes with a splicing reaction to influence expression of multiple mRNAs. Some have a composite internal/terminal exon which can be differentially processed. Others contain alternative 3'-terminal exons, the first of which can be skipped in some cells. In some cases the mRNAs formed from these three classes of genes are differentially processed from the primary transcript during the cell cycle or in a tissue-specific or developmentally specific pattern. Immunoglobulin heavy chain genes have composite exons; regulated production of two different Ig mRNAs has been shown to involve B cell stage-specific changes in trans -acting factors involved in formation of the active polyadenylation complex. Changes in the activity of some of these same factors occur during viral infection and take-over of the cellular machinery, suggesting the potential applicability of at least some aspects of the Ig model. The differential expression of a number of genes that undergo alternative poly(A) site choice or polyadenylation/splicing competition could be regulated at the level of amounts and activities of either generic or tissue-specific polyadenylation factors and/or splicing factors.
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Affiliation(s)
- G Edwalds-Gilbert
- Department of Molecular Genetics and Biochemistry and the Graduate Program in Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261-2072, USA
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50
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Kalchman MA, Koide HB, McCutcheon K, Graham RK, Nichol K, Nishiyama K, Kazemi-Esfarjani P, Lynn FC, Wellington C, Metzler M, Goldberg YP, Kanazawa I, Gietz RD, Hayden MR. HIP1, a human homologue of S. cerevisiae Sla2p, interacts with membrane-associated huntingtin in the brain. Nat Genet 1997; 16:44-53. [PMID: 9140394 DOI: 10.1038/ng0597-44] [Citation(s) in RCA: 279] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Huntington disease (HD) is associated with the expansion of a polyglutamine tract, greater than 35 repeats, in the HD gene product, huntingtin. Here we describe a novel huntingtin interacting protein, HIP1, which co-localizes with huntingtin and shares sequence homology and biochemical characteristics with Sla2p, a protein essential for function of the cytoskeleton in Saccharomyces cerevisiae. The huntingtin-HIP1 interaction is restricted to the brain and is inversely correlated to the polyglutamine length in huntingtin. This provides the first molecular link between huntingtin and the neuronal cytoskeleton and suggests that, in HD, loss of normal huntingtin-HIP1 interaction may contribute to a defect in membrane-cytoskeletal integrity in the brain.
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Affiliation(s)
- M A Kalchman
- Department of Medical Genetics, University of British Columbia, Vancouver, Canada
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