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Im W, Moon J, Kim M. Applications of CRISPR/Cas9 for Gene Editing in Hereditary Movement Disorders. J Mov Disord 2016; 9:136-43. [PMID: 27667185 PMCID: PMC5035944 DOI: 10.14802/jmd.16029] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 08/08/2016] [Accepted: 08/10/2016] [Indexed: 12/26/2022] Open
Abstract
Gene therapy is a potential therapeutic strategy for treating hereditary movement disorders, including hereditary ataxia, dystonia, Huntington’s disease, and Parkinson’s disease. Genome editing is a type of genetic engineering in which DNA is inserted, deleted or replaced in the genome using modified nucleases. Recently, clustered regularly interspaced short palindromic repeat/CRISPR associated protein 9 (CRISPR/Cas9) has been used as an essential tool in biotechnology. Cas9 is an RNA-guided DNA endonuclease enzyme that was originally associated with the adaptive immune system of Streptococcus pyogenes and is now being utilized as a genome editing tool to induce double strand breaks in DNA. CRISPR/Cas9 has advantages in terms of clinical applicability over other genome editing technologies such as zinc-finger nucleases and transcription activator-like effector nucleases because of easy in vivo delivery. Here, we review and discuss the applicability of CRISPR/Cas9 to preclinical studies or gene therapy in hereditary movement disorders.
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Affiliation(s)
- Wooseok Im
- Department of Neurology, Neuroscience Research Center, Seoul National University Hospital, Seoul, Korea
| | - Jangsup Moon
- Department of Neurology, Neuroscience Research Center, Seoul National University Hospital, Seoul, Korea
| | - Manho Kim
- Department of Neurology, Neuroscience Research Center, Seoul National University Hospital, Seoul, Korea.,Protein Metabolism Medical Research Center, Seoul National University College of Medicine, Seoul, Korea
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Johnson E, Chase K, McGowan S, Mondo E, Pfister E, Mick E, Friedline RH, Kim JK, Sapp E, DiFiglia M, Aronin N. Safety of Striatal Infusion of siRNA in a Transgenic Huntington's Disease Mouse Model. J Huntingtons Dis 2016; 4:219-229. [PMID: 26444021 DOI: 10.3233/jhd-150163] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The immune system In Huntington's disease (HD) is activated and may overreact to some therapies. RNA interference using siRNA lowers mutant huntingtin (mHTT) protein but could increase immune responses. OBJECTIVE To examine the innate immune response following siRNA infusion into the striatum of wild-type (WT) and HD transgenic (YAC128) mice. METHODS siRNAs (2'-O-methyl phosphorothioated) were infused unilaterally into striatum of four month-old WT and YAC128 mice for 28 days. Microglia number and morphology (resting (normal), activated, dystrophic), cytokine levels, and DARPP32-positive neurons were measured in striatum immediately or 14 days post-infusion. Controls included contralateral untreated striatum, and PBS and sham treated striata. RESULTS The striata of untreated YAC128 mice had significantly fewer resting microglia and more dystrophic microglia than WT mice, but no difference from WT in the proportion of activated microglia or total number of microglia. siRNA infusion increased the total number of microglia in YAC128 mice compared to PBS treated and untreated striata and increased the proportion of activated microglia in WT and YAC128 mice compared to untreated striata and sham treated groups. Cytokine levels were low and siRNA infusion resulted in only modest changes in those levels. siRNA infusion did not change the number of DARPP32-positive neurons. CONCLUSION Findings suggest that siRNA infusion may be a safe method for lowering mHTT levels in the striatum in young animals, since treatment does not produce a robust cytokine response or cause neurotoxicity. The potential long-term effects of a sustained increase in total and activated microglia after siRNA infusion in HD mice need to be explored.
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Affiliation(s)
- Emily Johnson
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Kathryn Chase
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Sarah McGowan
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Erica Mondo
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Edith Pfister
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Eric Mick
- Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, MA
| | - Randall H Friedline
- Department of Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Jason K Kim
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA.,Department of Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA
| | - Ellen Sapp
- Department of Massachusetts General Hospital, Charlestown, MA
| | - Marian DiFiglia
- Department of Massachusetts General Hospital, Charlestown, MA
| | - Neil Aronin
- Department of Medicine, University of Massachusetts Medical School, Worcester, MA
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Molecular Pathophysiology of Fragile X-Associated Tremor/Ataxia Syndrome and Perspectives for Drug Development. THE CEREBELLUM 2016; 15:599-610. [DOI: 10.1007/s12311-016-0800-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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N-terminal Huntingtin Knock-In Mice: Implications of Removing the N-terminal Region of Huntingtin for Therapy. PLoS Genet 2016; 12:e1006083. [PMID: 27203582 PMCID: PMC4874551 DOI: 10.1371/journal.pgen.1006083] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 05/04/2016] [Indexed: 02/07/2023] Open
Abstract
The Huntington’s disease (HD) protein, huntingtin (HTT), is a large protein consisting of 3144 amino acids and has conserved N-terminal sequences that are followed by a polyglutamine (polyQ) repeat. Loss of Htt is known to cause embryonic lethality in mice, whereas polyQ expansion leads to adult neuronal degeneration. Whether N-terminal HTT is essential for neuronal development or contributes only to late-onset neurodegeneration remains unknown. We established HTT knock-in mice (N160Q-KI) expressing the first 208 amino acids of HTT with 160Q, and they show age-dependent HTT aggregates in the brain and neurological phenotypes. Importantly, the N-terminal mutant HTT also preferentially accumulates in the striatum, the brain region most affected in HD, indicating the importance of N-terminal HTT in selective neuropathology. That said, homozygous N160Q-KI mice are also embryonic lethal, suggesting that N-terminal HTT alone is unable to support embryonic development. Using Htt knockout neurons, we found that loss of Htt selectively affects the survival of developing neuronal cells, but not astrocytes, in culture. This neuronal degeneration could be rescued by a truncated HTT lacking the first 237 amino acids, but not by N-terminal HTT (1–208 amino acids). Also, the rescue effect depends on the region in HTT known to be involved in intracellular trafficking. Thus, the N-terminal HTT region may not be essential for the survival of developing neurons, but when carrying a large polyQ repeat, can cause selective neuropathology. These findings imply a possible therapeutic benefit of removing the N-terminal region of HTT containing the polyQ repeat to treat the neurodegeneration in HD. The 17 amino acids in the N-terminal region of huntingtin (HTT) are conserved in a wide range of species and are followed by a polyglutamine repeat whose expansion causes selective neurodegeneration in Huntington’s disease (HD). Loss of Htt can affect developing neurons and early embryonic development in mice. Whether N-terminal HTT is important for the survival of developing neurons or contributes mainly to a gain of toxic function in HD remains unknown. In the current study, we generated N-terminal mutant HTT knock-in mice and found that N-terminal HTT with an expanded polyQ repeat is unable to support the early development of mice, but can cause age-dependent neurological phenotypes. Further, we show that a truncated HTT without the N-terminal region can rescue the Htt loss-mediated degeneration of developing neurons. Our studies suggest that removal of the N-terminal region of mutant HTT could be a strategy to abolish the neuronal toxicity of mutant HTT.
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Mason SL, Barker RA. Novel targets for Huntington's disease: future prospects. Degener Neurol Neuromuscul Dis 2016; 6:25-36. [PMID: 30050366 PMCID: PMC6053088 DOI: 10.2147/dnnd.s83808] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Huntington's disease (HD) is an incurable, inherited, progressive, neurodegenerative disorder that is characterized by a triad of motor, cognitive, and psychiatric problems. Despite the noticeable increase in therapeutic trials in HD in the last 20 years, there have, to date, been very few significant advances. The main hope for new and emerging therapeutics for HD is to develop a neuroprotective compound capable of slowing down or even stopping the progression of the disease and ultimately prevent the subtle early signs from developing into manifest disease. Recently, there has been a noticeable shift away from symptomatic therapies in favor of more mechanistic-based interventions, a change driven by a better understanding of the pathogenesis of this disorder. In this review, we discuss the status of, and supporting evidence for, potential novel treatments of HD that are currently under development or have reached the level of early Phase I/II clinical trials.
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Affiliation(s)
| | - Roger A Barker
- John van Geest Centre for Brain Repair, .,Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
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Design, Characterization, and Lead Selection of Therapeutic miRNAs Targeting Huntingtin for Development of Gene Therapy for Huntington's Disease. MOLECULAR THERAPY. NUCLEIC ACIDS 2016; 5:e297. [PMID: 27003755 PMCID: PMC5014463 DOI: 10.1038/mtna.2016.7] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 01/14/2016] [Indexed: 12/29/2022]
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by accumulation of CAG expansions in the huntingtin (HTT) gene. Hence, decreasing the expression of mutated HTT (mtHTT) is the most upstream approach for treatment of HD. We have developed HTT gene-silencing approaches based on expression cassette-optimized artificial miRNAs (miHTTs). In the first approach, total silencing of wild-type and mtHTT was achieved by targeting exon 1. In the second approach, allele-specific silencing was induced by targeting the heterozygous single-nucleotide polymorphism (SNP) rs362331 in exon 50 or rs362307 in exon 67 linked to mtHTT. The miHTT expression cassette was optimized by embedding anti-HTT target sequences in ten pri-miRNA scaffolds and their HTT knockdown efficacy, allele selectivity, passenger strand activity, and processing patterns were analyzed in vitro. Furthermore, three scaffolds expressing miH12 targeting exon 1 were incorporated in an adeno-associated viral serotype 5 (AAV5) vector and their HTT knock-down efficiency and pre-miHTT processing were compared in the humanized transgenic Hu128/21 HD mouse model. Our data demonstrate strong allele-selective silencing of mtHTT by miSNP50 targeting rs362331 and total HTT silencing by miH12 both in vitro and in vivo. Ultimately, we show that HTT knock-down efficiency and guide strand processing can be enhanced by using different cellular pri-miRNA scaffolds.
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Ablation of huntingtin in adult neurons is nondeleterious but its depletion in young mice causes acute pancreatitis. Proc Natl Acad Sci U S A 2016; 113:3359-64. [PMID: 26951659 DOI: 10.1073/pnas.1524575113] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The Huntington's disease (HD) protein, huntingtin (HTT), is essential for early development. Because suppressing the expression of mutant HTT is an important approach to treat the disease, we must first understand the normal function of Htt in adults versus younger animals. Using inducible Htt knockout mice, we found that Htt depletion does not lead to adult neurodegeneration or animal death at >4 mo of age, which was also verified by selectively depleting Htt in neurons. On the other hand, young Htt KO mice die at 2 mo of age of acute pancreatitis due to the degeneration of pancreatic acinar cells. Importantly, Htt interacts with the trypsin inhibitor, serine protease inhibitor Kazal-type 3 (Spink3), to inhibit activation of digestive enzymes in acinar cells in young mice, and transgenic HTT can rescue the early death of Htt KO mice. These findings point out age- and cell type-dependent vital functions of Htt and the safety of knocking down neuronal Htt expression in adult brains as a treatment.
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Maeder ML, Gersbach CA. Genome-editing Technologies for Gene and Cell Therapy. Mol Ther 2016; 24:430-46. [PMID: 26755333 PMCID: PMC4786923 DOI: 10.1038/mt.2016.10] [Citation(s) in RCA: 416] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 01/07/2016] [Indexed: 12/11/2022] Open
Abstract
Gene therapy has historically been defined as the addition of new genes to human cells. However, the recent advent of genome-editing technologies has enabled a new paradigm in which the sequence of the human genome can be precisely manipulated to achieve a therapeutic effect. This includes the correction of mutations that cause disease, the addition of therapeutic genes to specific sites in the genome, and the removal of deleterious genes or genome sequences. This review presents the mechanisms of different genome-editing strategies and describes each of the common nuclease-based platforms, including zinc finger nucleases, transcription activator-like effector nucleases (TALENs), meganucleases, and the CRISPR/Cas9 system. We then summarize the progress made in applying genome editing to various areas of gene and cell therapy, including antiviral strategies, immunotherapies, and the treatment of monogenic hereditary disorders. The current challenges and future prospects for genome editing as a transformative technology for gene and cell therapy are also discussed.
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Affiliation(s)
| | - Charles A Gersbach
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA
- Center for Genomic and Computational Biology, Duke University, Durham, North Carolina, USA
- Department of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina, USA
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Faria AV, Ratnanather JT, Tward DJ, Lee DS, van den Noort F, Wu D, Brown T, Johnson H, Paulsen JS, Ross CA, Younes L, Miller MI. Linking white matter and deep gray matter alterations in premanifest Huntington disease. Neuroimage Clin 2016; 11:450-460. [PMID: 27104139 PMCID: PMC4827723 DOI: 10.1016/j.nicl.2016.02.014] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 02/17/2016] [Accepted: 02/22/2016] [Indexed: 01/07/2023]
Abstract
Huntington disease (HD) is a fatal progressive neurodegenerative disorder for which only symptomatic treatment is available. A better understanding of the pathology, and identification of biomarkers will facilitate the development of disease-modifying treatments. HD is potentially a good model of a neurodegenerative disease for development of biomarkers because it is an autosomal-dominant disease with complete penetrance, caused by a single gene mutation, in which the neurodegenerative process can be assessed many years before onset of signs and symptoms of manifest disease. Previous MRI studies have detected abnormalities in gray and white matter starting in premanifest stages. However, the understanding of how these abnormalities are related, both in time and space, is still incomplete. In this study, we combined deep gray matter shape diffeomorphometry and white matter DTI analysis in order to provide a better mapping of pathology in the deep gray matter and subcortical white matter in premanifest HD. We used 296 MRI scans from the PREDICT-HD database. Atrophy in the deep gray matter, thalamus, hippocampus, and nucleus accumbens was analyzed by surface based morphometry, and while white matter abnormalities were analyzed in (i) regions of interest surrounding these structures, using (ii) tractography-based analysis, and using (iii) whole brain atlas-based analysis. We detected atrophy in the deep gray matter, particularly in putamen, from early premanifest stages. The atrophy was greater both in extent and effect size in cases with longer exposure to the effects of the CAG expansion mutation (as assessed by greater CAP-scores), and preceded detectible abnormalities in the white matter. Near the predicted onset of manifest HD, the MD increase was widespread, with highest indices in the deep and posterior white matter. This type of in-vivo macroscopic mapping of HD brain abnormalities can potentially indicate when and where therapeutics could be targeted to delay the onset or slow the disease progression.
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Affiliation(s)
- Andreia V Faria
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - J Tilak Ratnanather
- Center for Imaging Science, The Johns Hopkins University, Baltimore, MD, USA; Institute for Computational Medicine, The Johns Hopkins University, Baltimore, MD, USA; Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD, USA
| | - Daniel J Tward
- Center for Imaging Science, The Johns Hopkins University, Baltimore, MD, USA; Institute for Computational Medicine, The Johns Hopkins University, Baltimore, MD, USA; Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD, USA
| | - David Soobin Lee
- Center for Imaging Science, The Johns Hopkins University, Baltimore, MD, USA; Institute for Computational Medicine, The Johns Hopkins University, Baltimore, MD, USA; Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD, USA
| | - Frieda van den Noort
- MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands
| | - Dan Wu
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Timothy Brown
- Center for Imaging Science, The Johns Hopkins University, Baltimore, MD, USA
| | - Hans Johnson
- Department of Psychiatry, The University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Jane S Paulsen
- Department of Psychiatry, The University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Christopher A Ross
- Division of Neurobiology, Department of Psychiatry, and Departments of Neurology, Neuroscience and Pharmacology, Johns Hopkins University, Baltimore, MD, USA
| | - Laurent Younes
- Center for Imaging Science, The Johns Hopkins University, Baltimore, MD, USA; Institute for Computational Medicine, The Johns Hopkins University, Baltimore, MD, USA; Department of Applied Mathematics and Statistics, The Johns Hopkins University, Baltimore, MD, USA
| | - Michael I Miller
- Center for Imaging Science, The Johns Hopkins University, Baltimore, MD, USA; Institute for Computational Medicine, The Johns Hopkins University, Baltimore, MD, USA; Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD, USA
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Liu L, Huang JS, Han C, Zhang GX, Xu XY, Shen Y, Li J, Jiang HY, Lin ZC, Xiong N, Wang T. Induced Pluripotent Stem Cells in Huntington's Disease: Disease Modeling and the Potential for Cell-Based Therapy. Mol Neurobiol 2015; 53:6698-6708. [PMID: 26659595 DOI: 10.1007/s12035-015-9601-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 12/01/2015] [Indexed: 12/31/2022]
Abstract
Huntington's disease (HD) is an incurable neurodegenerative disorder that is characterized by motor dysfunction, cognitive impairment, and behavioral abnormalities. It is an autosomal dominant disorder caused by a CAG repeat expansion in the huntingtin gene, resulting in progressive neuronal loss predominately in the striatum and cortex. Despite the discovery of the causative gene in 1993, the exact mechanisms underlying HD pathogenesis have yet to be elucidated. Treatments that slow or halt the disease process are currently unavailable. Recent advances in induced pluripotent stem cell (iPSC) technologies have transformed our ability to study disease in human neural cells. Here, we firstly review the progress made to model HD in vitro using patient-derived iPSCs, which reveal unique insights into illuminating molecular mechanisms and provide a novel human cell-based platform for drug discovery. We then highlight the promises and challenges for pluripotent stem cells that might be used as a therapeutic source for cell replacement therapy of the lost neurons in HD brains.
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Affiliation(s)
- Ling Liu
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jin-Sha Huang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Chao Han
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Guo-Xin Zhang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xiao-Yun Xu
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yan Shen
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jie Li
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Hai-Yang Jiang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Zhi-Cheng Lin
- Department of Psychiatry, Harvard Medical School; Division of Alcohol and Drug Abuse, and Mailman Neuroscience Research Center, McLean Hospital, Belmont, MA, USA
| | - Nian Xiong
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Tao Wang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
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Bone Marrow-Derived Cells as a Therapeutic Approach to Optic Nerve Diseases. Stem Cells Int 2015; 2016:5078619. [PMID: 26649049 PMCID: PMC4663341 DOI: 10.1155/2016/5078619] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 09/10/2015] [Indexed: 12/16/2022] Open
Abstract
Following optic nerve injury associated with acute or progressive diseases, retinal ganglion cells (RGCs) of adult mammals degenerate and undergo apoptosis. These diseases have limited therapeutic options, due to the low inherent capacity of RGCs to regenerate and due to the inhibitory milieu of the central nervous system. Among the numerous treatment approaches investigated to stimulate neuronal survival and axonal extension, cell transplantation emerges as a promising option. This review focuses on cell therapies with bone marrow mononuclear cells and bone marrow-derived mesenchymal stem cells, which have shown positive therapeutic effects in animal models of optic neuropathies. Different aspects of available preclinical studies are analyzed, including cell distribution, potential doses, routes of administration, and mechanisms of action. Finally, published and ongoing clinical trials are summarized.
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Fox J, Lu Z, Barrows L. Thiol-disulfide Oxidoreductases TRX1 and TMX3 Decrease Neuronal Atrophy in a Lentiviral Mouse Model of Huntington's Disease. PLOS CURRENTS 2015; 7. [PMID: 26664998 PMCID: PMC4650837 DOI: 10.1371/currents.hd.b966ec2eca8e2d89d2bb4d020be4351e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Huntington’s disease (HD) is caused by a trinucleotide CAG repeat in the
huntingtin gene (HTT) that results in expression of a polyglutamine-expanded
mutant huntingtin protein (mHTT). N-terminal fragments of mHTT accumulate in
brain neurons and glia as soluble monomeric and oligomeric species as well as
insoluble protein aggregates and drive the disease process. Decreasing mHTT
levels in brain provides protection and reversal of disease signs in HD mice
making mHTT a prime target for disease modification. There is evidence for
aberrant thiol oxidation within mHTT and other proteins in HD models. Based on
this, we hypothesized that a specific thiol-disulfide oxidoreductase exists that
decreases mHTT levels in cells and provides protection in HD mice. We undertook
an in-vitro genetic screen of key thiol-disulfide oxidoreductases then completed
secondary screens to identify those with mHTT decreasing properties. Our
in-vitro experiments identified thioredoxin 1 and thioredoxin-related
transmembrane protein 3 as proteins that decrease soluble mHTT levels in
cultured cells. Using a lentiviral mouse model of HD we tested the effect of
these proteins in striatum. Both proteins decreased mHTT-induced striatal
neuronal atrophy. Findings provide evidence for a role of dysregulated
protein-thiol homeostasis in the pathogenesis of HD.
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Affiliation(s)
- Jonathan Fox
- Neuroscience Graduate Program, Department of Veterinary Sciences, University of Wyoming, Laramie, Wyoming, USA
| | - Zhen Lu
- Neuroscience Graduate Program, Department of Veterinary Sciences, University of Wyoming, Laramie, Wyoming, USA
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Identification of Genetic Factors that Modify Clinical Onset of Huntington's Disease. Cell 2015; 162:516-26. [PMID: 26232222 DOI: 10.1016/j.cell.2015.07.003] [Citation(s) in RCA: 436] [Impact Index Per Article: 48.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 04/16/2015] [Accepted: 06/18/2015] [Indexed: 10/23/2022]
Abstract
As a Mendelian neurodegenerative disorder, the genetic risk of Huntington's disease (HD) is conferred entirely by an HTT CAG repeat expansion whose length is the primary determinant of the rate of pathogenesis leading to disease onset. To investigate the pathogenic process that precedes disease, we used genome-wide association (GWA) analysis to identify loci harboring genetic variations that alter the age at neurological onset of HD. A chromosome 15 locus displays two independent effects that accelerate or delay onset by 6.1 years and 1.4 years, respectively, whereas a chromosome 8 locus hastens onset by 1.6 years. Association at MLH1 and pathway analysis of the full GWA results support a role for DNA handling and repair mechanisms in altering the course of HD. Our findings demonstrate that HD disease modification in humans occurs in nature and offer a genetic route to identifying in-human validated therapeutic targets in this and other Mendelian disorders.
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Sequence-Level Analysis of the Major European Huntington Disease Haplotype. Am J Hum Genet 2015; 97:435-44. [PMID: 26320893 DOI: 10.1016/j.ajhg.2015.07.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 07/31/2015] [Indexed: 01/08/2023] Open
Abstract
Huntington disease (HD) reflects the dominant consequences of a CAG-repeat expansion in HTT. Analysis of common SNP-based haplotypes has revealed that most European HD subjects have distinguishable HTT haplotypes on their normal and disease chromosomes and that ∼50% of the latter share the same major HD haplotype. We reasoned that sequence-level investigation of this founder haplotype could provide significant insights into the history of HD and valuable information for gene-targeting approaches. Consequently, we performed whole-genome sequencing of HD and control subjects from four independent families in whom the major European HD haplotype segregates with the disease. Analysis of the full-sequence-based HTT haplotype indicated that these four families share a common ancestor sufficiently distant to have permitted the accumulation of family-specific variants. Confirmation of new CAG-expansion mutations on this haplotype suggests that unlike most founders of human disease, the common ancestor of HD-affected families with the major haplotype most likely did not have HD. Further, availability of the full sequence data validated the use of SNP imputation to predict the optimal variants for capturing heterozygosity in personalized allele-specific gene-silencing approaches. As few as ten SNPs are capable of revealing heterozygosity in more than 97% of European HD subjects. Extension of allele-specific silencing strategies to the few remaining homozygous individuals is likely to be achievable through additional known SNPs and discovery of private variants by complete sequencing of HTT. These data suggest that the current development of gene-based targeting for HD could be extended to personalized allele-specific approaches in essentially all HD individuals of European ancestry.
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Sampaio C, Borowsky B, Reilmann R. Clinical trials in Huntington's disease: Interventions in early clinical development and newer methodological approaches. Mov Disord 2015; 29:1419-28. [PMID: 25216371 DOI: 10.1002/mds.26021] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 08/11/2014] [Accepted: 08/17/2014] [Indexed: 02/02/2023] Open
Abstract
Since the identification of the Huntington's disease (HD) gene, knowledge has accumulated about mechanisms directly or indirectly affected by the mutated Huntingtin protein. Transgenic and knock-in animal models of HD facilitate the preclinical evaluation of these targets. Several treatment approaches with varying, but growing, preclinical evidence have been translated into clinical trials. We review major landmarks in clinical development and report on the main clinical trials that are ongoing or have been recently completed. We also review clinical trial settings and designs that influence drug-development decisions, particularly given that HD is an orphan disease. In addition, we provide a critical analysis of the evolution of the methodology of HD clinical trials to identify trends toward new processes and endpoints. Biomarker studies, such as TRACK-HD and PREDICT-HD, have generated evidence for the potential usefulness of novel outcome measures for HD clinical trials, such as volumetric imaging, quantitative motor (Q-Motor) measures, and novel cognitive endpoints. All of these endpoints are currently applied in ongoing clinical trials, which will provide insight into their reliability, sensitivity, and validity, and their use may expedite proof-of-concept studies. We also outline the specific opportunities that could provide a framework for a successful avenue toward identifying and efficiently testing and translating novel mechanisms of action in the HD field.
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