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Wang J, Haeusler AR, Simko EAJ. Emerging role of RNA•DNA hybrids in C9orf72-linked neurodegeneration. Cell Cycle 2015; 14:526-32. [PMID: 25590632 DOI: 10.1080/15384101.2014.995490] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
RNA plays an active role in structural polymorphism of the genome through the formation of stable RNA•DNA hybrids (R-loops). R-loops can modulate normal physiological processes and are also associated with pathological conditions, such as those related to nucleotide repeat expansions. A guanine-rich hexanucleotide repeat expansion in chromosome 9 open reading frame 72 (C9orf72) has been linked to a spectrum of neurological conditions including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here we discuss the possible roles, both locally and genome-wide, of R-loops that may arise from the C9orf72 hexanucleotide repeat. R-loops have the potential to influence the pathological processes identified in many repeat expansion diseases, such as repeat instability, transcriptional dysregulation, epigenetic modification, and antisense-mediated gene regulation. We propose that, given the wide-ranging consequences of R-loops in the cell, these structures could underlie multiple pathological processes in C9orf72-linked neurodegeneration.
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Affiliation(s)
- Jiou Wang
- a Department of Biochemistry and Molecular Biology; Bloomberg School of Public Health ; Johns Hopkins University ; Baltimore , MD USA
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Cheng YW, Lee MJ, Chen TF, Cheng TW, Lai YM, Hua MS, Chiu MJ. A single nucleotide TDP-43 mutation within a Taiwanese family: A multifaceted demon. Amyotroph Lateral Scler Frontotemporal Degener 2015; 17:292-4. [DOI: 10.3109/21678421.2015.1111905] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Yu-Wen Cheng
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ming-Jen Lee
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ta-Fu Chen
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ting-Wen Cheng
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ya-Mei Lai
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Mau-Sun Hua
- Department of Psychology, College of Science, National Taiwan University, Taipei
| | - Ming-Jang Chiu
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
- Department of Psychology, College of Science, National Taiwan University, Taipei
- Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan
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Hubstenberger A, Cameron C, Noble SL, Keenan S, Evans TC. Modifiers of solid RNP granules control normal RNP dynamics and mRNA activity in early development. J Cell Biol 2015; 211:703-16. [PMID: 26527741 PMCID: PMC4639854 DOI: 10.1083/jcb.201504044] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 09/25/2015] [Indexed: 12/13/2022] Open
Abstract
Modifiers of aberrant solid RNP granules suggest new insights into pathways that control dynamics of large-scale RNP bodies and mRNAs during C. elegans oogenesis. Ribonucleoproteins (RNPs) often coassemble into supramolecular bodies with regulated dynamics. The factors controlling RNP bodies and connections to RNA regulation are unclear. During Caenorhabditis elegans oogenesis, cytoplasmic RNPs can transition among diffuse, liquid, and solid states linked to mRNA regulation. Loss of CGH-1/Ddx6 RNA helicase generates solid granules that are sensitive to mRNA regulators. Here, we identified 66 modifiers of RNP solids induced by cgh-1 mutation. A majority of genes promote or suppress normal RNP body assembly, dynamics, or metabolism. Surprisingly, polyadenylation factors promote RNP coassembly in vivo, suggesting new functions of poly(A) tail regulation in RNP dynamics. Many genes carry polyglutatmine (polyQ) motifs or modulate polyQ aggregation, indicating possible connections with neurodegenerative disorders induced by CAG/polyQ expansion. Several RNP body regulators repress translation of mRNA subsets, suggesting that mRNAs are repressed by multiple mechanisms. Collectively, these findings suggest new pathways of RNP modification that control large-scale coassembly and mRNA activity during development.
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Affiliation(s)
- Arnaud Hubstenberger
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 Pierre-and-Marie-Curie University, University Paris 06, 75005 Paris, France
| | - Cristiana Cameron
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Scott L Noble
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 Graduate Program in Molecular Biology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Sean Keenan
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Thomas C Evans
- Department of Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
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Le Ber I. Frontotemporal lobar dementia and amyotrophic lateral sclerosis associated with c9orf72 expansion. Rev Neurol (Paris) 2015; 171:475-81. [PMID: 26032484 DOI: 10.1016/j.neurol.2015.04.004] [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] [Received: 03/24/2015] [Revised: 04/24/2015] [Accepted: 04/24/2015] [Indexed: 12/12/2022]
Abstract
An intronic GGGGCC repeat expansion in c9orf72 gene has been identified as the most common genetic cause of frontotemporal lobar dementia (FTLD), amyotrophic lateral sclerosis (ALS) and FTLD-ALS. The discovery of c9orf72 gene has led to important scientific progresses and has considerably changed our clinical practice over the last few years. This paper summarizes the common and less typical phenotypes associated with c9orf72 expansion, the complex pathological pattern characterized by p62/dipeptide repeat aggregates, as well as the pathological mechanisms by which the expansion might produce neurodegeneration implicating loss-of-function, RNA toxicity, RNA-binding protein sequestration and accumulation of dipeptide repeats. We also discuss the recommendations and limits for genetic testing and counseling in clinical practice.
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Affiliation(s)
- I Le Ber
- Institut du cerveau et de la moelle épinière (ICM), Inserm U1127, CNRS UMR 7225, Sorbonne Universités, Université Pierre-et-Marie-Curie, université Paris 06, UPMC-P6 UMR S 1127, hôpital Pitié-Salpêtrière, 75013 Paris, France; Centre de référence des rémences rares, hôpital de la Pitié-Salpêtrière, AP-HP, 75013 Paris, France; Département des maladies du système nerveux, hôpital de la Pitié-Salpêtrière, AP-HP, 75013 Paris, France.
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55
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Defining the genetic connection linking amyotrophic lateral sclerosis (ALS) with frontotemporal dementia (FTD). Trends Genet 2015; 31:263-73. [DOI: 10.1016/j.tig.2015.03.005] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 03/10/2015] [Accepted: 03/10/2015] [Indexed: 12/11/2022]
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Coutelier M, Stevanin G, Brice A. Genetic landscape remodelling in spinocerebellar ataxias: the influence of next-generation sequencing. J Neurol 2015; 262:2382-95. [DOI: 10.1007/s00415-015-7725-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Revised: 03/25/2015] [Accepted: 03/26/2015] [Indexed: 12/23/2022]
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Abstract
The degeneration of motor neurons in amyotrophic lateral sclerosis (ALS) inevitably causes paralysis and death within a matter of years. Mounting genetic and functional evidence suggest that abnormalities in RNA processing and metabolism underlie motor neuron loss in sporadic and familial ALS. Abnormal localization and aggregation of essential RNA-binding proteins are fundamental pathological features of sporadic ALS, and mutations in genes encoding RNA processing enzymes cause familial disease. Also, expansion mutations occurring in the noncoding region of C9orf72-the most common cause of inherited ALS-result in nuclear RNA foci, underscoring the link between abnormal RNA metabolism and neurodegeneration in ALS. This review summarizes the current understanding of RNA dysfunction in ALS, and builds upon this knowledge base to identify converging mechanisms of neurodegeneration in ALS. Potential targets for therapy development are highlighted, with particular emphasis on early and conserved pathways that lead to motor neuron loss in ALS.
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Affiliation(s)
- Sami J Barmada
- Department of Neurology, University of Michigan, 109 Zina Pitcher Place, 5015 Biomedical Sciences Research Building, SSPC 2200, Ann Arbor, MI, 48109, USA,
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Cooper-Knock J, Kirby J, Highley R, Shaw PJ. The Spectrum of C9orf72-mediated Neurodegeneration and Amyotrophic Lateral Sclerosis. Neurotherapeutics 2015; 12:326-39. [PMID: 25731823 PMCID: PMC4404438 DOI: 10.1007/s13311-015-0342-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The discovery that a hexanucleotide repeat expansion in C9orf72 is the most numerous genetic variant of both amyotrophic lateral sclerosis and frontotemporal dementia has opened a rapidly growing field, which may provide long hoped for advances in the understanding and treatment of these devastating diseases. In this review we describe the various phenotypes, clinical and pathological, associated with expansion of C9orf72, which go beyond amyotrophic lateral sclerosis and frontotemporal dementia to include neurodegeneration more broadly. Next we take a step back and summarize the current understanding of the C9orf72 expansion and its protein products at a molecular level. Three mechanisms are prominent: toxicity mediated directly by RNA transcribed from the repeat; toxicity mediated by dipeptide repeat proteins translated from the repeat sequence; and haploinsufficiency resulting from reduced transcription of the C9orf72 exonic sequence. A series of exciting advances have recently described how dipeptide repeat proteins might interfere with the normal role of the nucleolus in maturation of RNA binding proteins and in production of ribosomes. Importantly, these mechanisms are unlikely to be mutually exclusive. We draw attention to the fact that clinical and pathological similarities to other genetic variants without a repeat expansion must not be overlooked in ascribing a pathogenic mechanism to C9orf72-disease. Finally, with a view to impact on patient care, we discuss current practice with respect to genetic screening in patients with and without a family history of disease, and the most promising developments towards therapy that have been reported to date.
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Affiliation(s)
- Johnathan Cooper-Knock
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, University of Sheffield, 385A Glossop Road, Sheffield, S10 2HQ UK
| | - Janine Kirby
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, University of Sheffield, 385A Glossop Road, Sheffield, S10 2HQ UK
| | - Robin Highley
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, University of Sheffield, 385A Glossop Road, Sheffield, S10 2HQ UK
| | - Pamela J. Shaw
- Sheffield Institute for Translational Neuroscience, Department of Neuroscience, University of Sheffield, 385A Glossop Road, Sheffield, S10 2HQ UK
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Ng ASL, Rademakers R, Miller BL. Frontotemporal dementia: a bridge between dementia and neuromuscular disease. Ann N Y Acad Sci 2014; 1338:71-93. [PMID: 25557955 DOI: 10.1111/nyas.12638] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The concept that frontotemporal dementia (FTD) is a purely cortical dementia has largely been refuted by the recognition of its close association with motor neuron disease, and the identification of transactive response DNA-binding protein 43 (TDP-43) as a major pathological substrate underlying both diseases. Genetic findings have transformed this field and revealed connections between disorders that were previous thought clinically unrelated. The discovery that the C9ORF72 locus is responsible for the majority of hereditary FTD, amyotrophic lateral sclerosis (ALS), and FTD-ALS cases and the understanding that repeat-containing RNA plays a crucial role in pathogenesis of both disorders has paved the way for the development of potential biomarkers and therapeutic targets for these devastating diseases. In this review, we summarize the historical aspects leading up to our current understanding of the genetic, clinical, and neuropathological overlap between FTD and ALS, and include brief discussions on chronic traumatic encephalopathy (CTE), given its association with TDP-43 pathology, its associated increased dementia risk, and reports of ALS in CTE patients. In addition, we describe other genetic associations between dementia and neuromuscular disease, such as inclusion body myositis with Paget's disease and FTD.
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Affiliation(s)
- Adeline S L Ng
- Department of Neurology, National Neuroscience Institute, Tan Tock Seng Hospital, Novena, Singapore
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