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Glass JD, Dewan R, Ding J, Gibbs JR, Dalgard C, Keagle PJ, Shankaracharya, García-Redondo A, Traynor BJ, Chia R, Landers JE. ATXN2 intermediate expansions in amyotrophic lateral sclerosis. Brain 2022; 145:2671-2676. [PMID: 35521889 PMCID: PMC9890463 DOI: 10.1093/brain/awac167] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 03/21/2022] [Accepted: 04/20/2022] [Indexed: 02/04/2023] Open
Abstract
Intermediate CAG (polyQ) expansions in the gene ataxin-2 (ATXN2) are now recognized as a risk factor for amyotrophic lateral sclerosis. The threshold for increased risk is not yet firmly established, with reports ranging from 27 to 31 repeats. We investigated the presence of ATXN2 polyQ expansions in 9268 DNA samples collected from people with amyotrophic lateral sclerosis, amyotrophic lateral sclerosis with frontotemporal dementia, frontotemporal dementia alone, Lewy body dementia and age matched controls. This analysis confirmed ATXN2 intermediate polyQ expansions of ≥31 as a risk factor for amyotrophic lateral sclerosis with an odds ratio of 6.31. Expansions were an even greater risk for amyotrophic lateral sclerosis with frontotemporal dementia (odds ratio 27.59) and a somewhat lesser risk for frontotemporal dementia alone (odds ratio 3.14). There was no increased risk for Lewy body dementia. In a subset of 1362 patients with amyotrophic lateral sclerosis with complete clinical data, we could not confirm previous reports of earlier onset of amyotrophic lateral sclerosis or shorter survival in 25 patients with expansions. These new data confirm ≥31 polyQ repeats in ATXN2 increase the risk for amyotrophic lateral sclerosis, and also for the first time show an even greater risk for amyotrophic lateral sclerosis with frontotemporal dementia. The lack of a more aggressive phenotype in amyotrophic lateral sclerosis patients with expansions has implications for ongoing gene-silencing trials for amyotrophic lateral sclerosis.
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Affiliation(s)
- Jonathan D Glass
- Correspondence to: Jonathan D. Glass, MD Department of Neurology, Emory University 101 Woodruff Circle, Atlanta, GA 30322, USA E-mail:
| | - Ramita Dewan
- Neuromuscular Diseases Research Section, Laboratory of Neurogenetics, National Institute on Aging, NIH, Bethesda, MD 20892, USA
| | - Jinhui Ding
- Neuromuscular Diseases Research Section, Laboratory of Neurogenetics, National Institute on Aging, NIH, Bethesda, MD 20892, USA,Computational Biology Group, Laboratory of Neurogenetics, National Institute on Aging, Bethesda, MD 20892, USA
| | - J Raphael Gibbs
- Computational Biology Group, Laboratory of Neurogenetics, National Institute on Aging, Bethesda, MD 20892, USA
| | - Clifton Dalgard
- Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
| | - Pamela J Keagle
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Shankaracharya
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605, USA
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Huelsmeier J, Walker E, Bakthavachalu B, Ramaswami M. A C-terminal ataxin-2 disordered region promotes Huntingtin protein aggregation and neurodegeneration in Drosophila models of Huntington’s disease. G3 GENES|GENOMES|GENETICS 2021; 11:6385240. [PMID: 34718534 PMCID: PMC8664476 DOI: 10.1093/g3journal/jkab355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 10/01/2021] [Indexed: 11/15/2022]
Abstract
The Ataxin-2 (Atx2) protein contributes to the progression of neurodegenerative phenotypes in animal models of amyotrophic lateral sclerosis (ALS), type 2 spinocerebellar ataxia (SCA-2), Parkinson’s disease, and Huntington’s disease (HD). However, because the Atx2 protein contains multiple separable activities, deeper understanding requires experiments to address the exact mechanisms by which Atx2 modulates neurodegeneration (ND) progression. Recent work on two ALS models, C9ORF72 and FUS, in Drosophila has shown that a C-terminal intrinsically disordered region (cIDR) of Atx2 protein, required for assembly of ribonucleoprotein (RNP) granules, is essential for the progression of neurodegenerative phenotypes as well as for accumulation of protein inclusions associated with these ALS models. Here, we show that the Atx2-cIDR also similarly contributes to the progression of degenerative phenotypes and accumulation of Huntingtin protein aggregates in Drosophila models of HD. Because Huntingtin is not an established component of RNP granules, these observations support a recently hypothesized, unexpected protein-handling function for RNP granules, which could contribute to the progression of Huntington’s disease and, potentially, other proteinopathies.
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Affiliation(s)
- Joern Huelsmeier
- School of Genetics and Microbiology, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland
| | - Emily Walker
- School of Genetics and Microbiology, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland
| | - Baskar Bakthavachalu
- School of Basic Science, Indian Institute of Technology, Mandi, Suran 175075, India
| | - Mani Ramaswami
- School of Genetics and Microbiology, Trinity College Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland
- National Centre for Biological Sciences, TIFR, Bangalore 560065, India
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The ATXN2 Orthologs CID3 and CID4, Act Redundantly to In-Fluence Developmental Pathways throughout the Life Cycle of Arabidopsis thaliana. Int J Mol Sci 2021; 22:ijms22063068. [PMID: 33802796 PMCID: PMC8002431 DOI: 10.3390/ijms22063068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 02/15/2021] [Accepted: 02/15/2021] [Indexed: 11/17/2022] Open
Abstract
RNA-binding proteins (RBPs) are key elements involved in post-transcriptional regulation. Ataxin-2 (ATXN2) is an evolutionarily conserved RBP protein, whose function has been studied in several model organisms, from Saccharomyces cerevisiae to the Homo sapiens. ATXN2 interacts with poly(A) binding proteins (PABP) and binds to specific sequences at the 3'UTR of target mRNAs to stabilize them. CTC-Interacting Domain3 (CID3) and CID4 are two ATXN2 orthologs present in plant genomes whose function is unknown. In the present study, phenotypical and transcriptome profiling were used to examine the role of CID3 and CID4 in Arabidopsis thaliana. We found that they act redundantly to influence pathways throughout the life cycle. cid3cid4 double mutant showed a delay in flowering time and a reduced rosette size. Transcriptome profiling revealed that key factors that promote floral transition and floral meristem identity were downregulated in cid3cid4 whereas the flowering repressor FLOWERING LOCUS C (FLC) was upregulated. Expression of key factors in the photoperiodic regulation of flowering and circadian clock pathways, were also altered in cid3cid4, as well as the expression of several transcription factors and miRNAs encoding genes involved in leaf growth dynamics. These findings reveal that ATXN2 orthologs may have a role in developmental pathways throughout the life cycle of plants.
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Singh A, Hulsmeier J, Kandi AR, Pothapragada SS, Hillebrand J, Petrauskas A, Agrawal K, RT K, Thiagarajan D, Jayaprakashappa D, VijayRaghavan K, Ramaswami M, Bakthavachalu B. Antagonistic roles for Ataxin-2 structured and disordered domains in RNP condensation. eLife 2021; 10:e60326. [PMID: 33689682 PMCID: PMC7946432 DOI: 10.7554/elife.60326] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 02/23/2021] [Indexed: 02/07/2023] Open
Abstract
Ataxin-2 (Atx2) is a translational control molecule mutated in spinocerebellar ataxia type II and amyotrophic lateral sclerosis. While intrinsically disordered domains (IDRs) of Atx2 facilitate mRNP condensation into granules, how IDRs work with structured domains to enable positive and negative regulation of target mRNAs remains unclear. Using the Targets of RNA-Binding Proteins Identified by Editing technology, we identified an extensive data set of Atx2-target mRNAs in the Drosophila brain and S2 cells. Atx2 interactions with AU-rich elements in 3'UTRs appear to modulate stability/turnover of a large fraction of these target mRNAs. Further genomic and cell biological analyses of Atx2 domain deletions demonstrate that Atx2 (1) interacts closely with target mRNAs within mRNP granules, (2) contains distinct protein domains that drive or oppose RNP-granule assembly, and (3) has additional essential roles outside of mRNP granules. These findings increase the understanding of neuronal translational control mechanisms and inform strategies for Atx2-based interventions under development for neurodegenerative disease.
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Affiliation(s)
- Amanjot Singh
- National Centre for Biological SciencesBangaloreIndia
| | - Joern Hulsmeier
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College DublinDublinIreland
| | - Arvind Reddy Kandi
- National Centre for Biological SciencesBangaloreIndia
- Tata Institute for Genetics and Society Centre at inStem, Bellary RoadBangaloreIndia
| | | | - Jens Hillebrand
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College DublinDublinIreland
| | - Arnas Petrauskas
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College DublinDublinIreland
| | - Khushboo Agrawal
- Tata Institute for Genetics and Society Centre at inStem, Bellary RoadBangaloreIndia
- School of Biotechnology, Amrita Vishwa Vidyapeetham UniversityKollamIndia
| | - Krishnan RT
- National Centre for Biological SciencesBangaloreIndia
| | | | | | | | - Mani Ramaswami
- National Centre for Biological SciencesBangaloreIndia
- Trinity College Institute of Neuroscience, School of Genetics and Microbiology, Smurfit Institute of Genetics and School of Natural Sciences, Trinity College DublinDublinIreland
| | - Baskar Bakthavachalu
- National Centre for Biological SciencesBangaloreIndia
- Tata Institute for Genetics and Society Centre at inStem, Bellary RoadBangaloreIndia
- School of Basic Sciences, Indian Institute of TechnologyMandiIndia
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Schwartz JL, Jones KL, Yeo GW. Repeat RNA expansion disorders of the nervous system: post-transcriptional mechanisms and therapeutic strategies. Crit Rev Biochem Mol Biol 2020; 56:31-53. [PMID: 33172304 PMCID: PMC8192115 DOI: 10.1080/10409238.2020.1841726] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Dozens of incurable neurological disorders result from expansion of short repeat sequences in both coding and non-coding regions of the transcriptome. Short repeat expansions underlie microsatellite repeat expansion (MRE) disorders including myotonic dystrophy (DM1, CUG50–3,500 in DMPK; DM2, CCTG75–11,000 in ZNF9), fragile X tremor ataxia syndrome (FXTAS, CGG50–200 in FMR1), spinal bulbar muscular atrophy (SBMA, CAG40–55 in AR), Huntington’s disease (HD, CAG36–121 in HTT), C9ORF72-amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD and C9-ALS/FTD, GGGGCC in C9ORF72), and many others, like ataxias. Recent research has highlighted several mechanisms that may contribute to pathology in this heterogeneous class of neurological MRE disorders – bidirectional transcription, intranuclear RNA foci, and repeat associated non-AUG (RAN) translation – which are the subject of this review. Additionally, many MRE disorders share similar underlying molecular pathologies that have been recently targeted in experimental and preclinical contexts. We discuss the therapeutic potential of versatile therapeutic strategies that may selectively target disrupted RNA-based processes and may be readily adaptable for the treatment of multiple MRE disorders. Collectively, the strategies under consideration for treatment of multiple MRE disorders include reducing levels of toxic RNA, preventing RNA foci formation, and eliminating the downstream cellular toxicity associated with peptide repeats produced by RAN translation. While treatments are still lacking for the majority of MRE disorders, several promising therapeutic strategies have emerged and will be evaluated within this review.
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Affiliation(s)
- Joshua L Schwartz
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
| | - Krysten Leigh Jones
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA
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St Martin JL, Wang L, Kaprielian Z. Toxicity in ALS: TDP-43 modifiers and C9orf72. Neurosci Lett 2019; 716:134621. [PMID: 31726180 DOI: 10.1016/j.neulet.2019.134621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 10/24/2019] [Accepted: 11/07/2019] [Indexed: 12/13/2022]
Abstract
Amyotrophic Lateral Sclerosis (ALS) is a devastating and fatal neurodegenerative disease affecting approximately 30,000 individuals in the United States. The average age of onset is 55 years and progression of the disease is rapid with most patients dying of respiratory failure within 3-5 years. Currently available therapeutics have modest effects on patient survival, underscoring the immediate need for more effective medicines. Recent technological advances in next generation sequencing have led to a substantial uptick in the discovery of genes linked to ALS. Since 90 % of ALS cases are sporadic, risk genes identified in familial cases provide invaluable insights into the molecular pathogenesis of the disease. Most notably, TDP-43-expressing neuronal inclusions and C9orf72 mutations have emerged as the key pathological and genetic hallmarks, respectively, of ALS. In this review, we will discuss recent advances in modifiers of TDP-43 toxicity, with an emphasis on Ataxin-2, one of the most well-characterized TDP-43 modifiers. An understanding of Ataxin-2 function and related biological pathways could provide a framework for the discovery of other novel modifiers of TDP-43. We will also describe the pathogenic mechanisms underlying C9orf72 toxicity and how these impact the disease process. Finally, we will explore emerging therapeutic strategies for dampening TDP-43 and C9orf72 toxicity and, ultimately, slowing or halting the progression of ALS.
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Affiliation(s)
| | - Lina Wang
- Amgen, Neuroscience Discovery, Cambridge, MA, United States
| | - Zaven Kaprielian
- Dementia Discovery Foundation US Discovery, Boston, United States.
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Abstract
Eukaryotic cells organize their intracellular components into organelles that can be membrane-bound or membraneless. A large number of membraneless organelles, including nucleoli, Cajal bodies, P-bodies, and stress granules, exist as liquid droplets within the cell and arise from the condensation of cellular material in a process termed liquid-liquid phase separation (LLPS). Beyond a mere organizational tool, concentrating cellular components into membraneless organelles tunes biochemical reactions and improves cellular fitness during stress. In this review, we provide an overview of the molecular underpinnings of the formation and regulation of these membraneless organelles. This molecular understanding explains emergent properties of these membraneless organelles and shines new light on neurodegenerative diseases, which may originate from disturbances in LLPS and membraneless organelles.
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Affiliation(s)
- Edward Gomes
- From the Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - James Shorter
- From the Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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