1
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Zannini L, Cardano M, Liberi G, Buscemi G. R-loops and impaired autophagy trigger cGAS-dependent inflammation via micronuclei formation in Senataxin-deficient cells. Cell Mol Life Sci 2024; 81:339. [PMID: 39120648 PMCID: PMC11335261 DOI: 10.1007/s00018-024-05380-3] [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: 04/11/2024] [Revised: 07/17/2024] [Accepted: 07/23/2024] [Indexed: 08/10/2024]
Abstract
Senataxin is an evolutionarily conserved DNA/RNA helicase, whose dysfunctions are linked to neurodegeneration and cancer. A main activity of this protein is the removal of R-loops, which are nucleic acid structures capable to promote DNA damage and replication stress. Here we found that Senataxin deficiency causes the release of damaged DNA into extranuclear bodies, called micronuclei, triggering the massive recruitment of cGAS, the apical sensor of the innate immunity pathway, and the downstream stimulation of interferon genes. Such cGAS-positive micronuclei are characterized by defective membrane envelope and are particularly abundant in cycling cells lacking Senataxin, but not after exposure to a DNA breaking agent or in absence of the tumor suppressor BRCA1 protein, a partner of Senataxin in R-loop removal. Micronuclei with a discontinuous membrane are normally cleared by autophagy, a process that we show is impaired in Senataxin-deficient cells. The formation of Senataxin-dependent inflamed micronuclei is promoted by the persistence of nuclear R-loops stimulated by the DSIF transcription elongation complex and the engagement of EXO1 nuclease activity on nuclear DNA. Coherently, high levels of EXO1 result in poor prognosis in a subset of tumors lacking Senataxin expression. Hence, R-loop homeostasis impairment, together with autophagy failure and unscheduled EXO1 activity, elicits innate immune response through micronuclei formation in cells lacking Senataxin.
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Affiliation(s)
- Laura Zannini
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, Pavia, 27100, Italy
| | - Miriana Cardano
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, Pavia, 27100, Italy
| | - Giordano Liberi
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, Pavia, 27100, Italy.
| | - Giacomo Buscemi
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", CNR, Pavia, 27100, Italy.
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2
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Ikenoshita S, Matsuo K, Yabuki Y, Kawakubo K, Asamitsu S, Hori K, Usuki S, Hirose Y, Bando T, Araki K, Ueda M, Sugiyama H, Shioda N. A cyclic pyrrole-imidazole polyamide reduces pathogenic RNA in CAG/CTG triplet repeat neurological disease models. J Clin Invest 2023; 133:e164792. [PMID: 37707954 PMCID: PMC10645379 DOI: 10.1172/jci164792] [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: 08/24/2022] [Accepted: 09/12/2023] [Indexed: 09/16/2023] Open
Abstract
Expansion of CAG and CTG (CWG) triplet repeats causes several inherited neurological diseases. The CWG repeat diseases are thought to involve complex pathogenic mechanisms through expanded CWG repeat-derived RNAs in a noncoding region and polypeptides in a coding region, respectively. However, an effective therapeutic approach has not been established for the CWG repeat diseases. Here, we show that a CWG repeat DNA-targeting compound, cyclic pyrrole-imidazole polyamide (CWG-cPIP), suppressed the pathogenesis of coding and noncoding CWG repeat diseases. CWG-cPIP bound to the hairpin form of mismatched CWG DNA, interfering with transcription elongation by RNA polymerase through a preferential activity toward repeat-expanded DNA. We found that CWG-cPIP selectively inhibited pathogenic mRNA transcripts from expanded CWG repeats, reducing CUG RNA foci and polyglutamine accumulation in cells from patients with myotonic dystrophy type 1 (DM1) and Huntington's disease (HD). Treatment with CWG-cPIP ameliorated behavioral deficits in adeno-associated virus-mediated CWG repeat-expressing mice and in a genetic mouse model of HD, without cytotoxicity or off-target effects. Together, we present a candidate compound that targets expanded CWG repeat DNA independently of its genomic location and reduces both pathogenic RNA and protein levels. CWG-cPIP may be used for the treatment of CWG repeat diseases and improvement of clinical outcomes.
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Affiliation(s)
- Susumu Ikenoshita
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG)
- Department of Neurology, Graduate School of Medical Sciences
| | - Kazuya Matsuo
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG)
| | - Yasushi Yabuki
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG)
- Graduate School of Pharmaceutical Sciences, and
| | - Kosuke Kawakubo
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG)
- Graduate School of Pharmaceutical Sciences, and
| | - Sefan Asamitsu
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG)
| | - Karin Hori
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG)
| | - Shingo Usuki
- Liaison Laboratory Research Promotion Center, IMEG, Kumamoto University, Kumamoto, Japan
| | - Yuki Hirose
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Toshikazu Bando
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Kimi Araki
- Institute of Resource Development and Analysis and
- Center for Metabolic Regulation of Healthy Aging, Kumamoto University, Kumamoto, Japan
| | - Mitsuharu Ueda
- Department of Neurology, Graduate School of Medical Sciences
| | - Hiroshi Sugiyama
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
- Institute for Integrated Cell-Material Science (iCeMS), Kyoto University, Kyoto, Japan
| | - Norifumi Shioda
- Department of Genomic Neurology, Institute of Molecular Embryology and Genetics (IMEG)
- Graduate School of Pharmaceutical Sciences, and
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3
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Curtis SW, Carlson JC, Beaty TH, Murray JC, Weinberg SM, Marazita ML, Cotney JL, Cutler DJ, Epstein MP, Leslie EJ. Rare variant modifier analysis identifies variants in SEC24D associated with orofacial cleft subtypes. Hum Genet 2023; 142:1531-1541. [PMID: 37676273 DOI: 10.1007/s00439-023-02596-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 08/18/2023] [Indexed: 09/08/2023]
Abstract
As one of the most common structural birth defects, orofacial clefts (OFCs) have been studied for decades, and recent studies have demonstrated that there are genetic differences between the different phenotypic presentations of OFCs. However, the contribution of rare genetic variation genome-wide to different subtypes of OFCs has been understudied, with most studies focusing on common genetic variation or rare variation within targeted regions of the genome. Therefore, we used whole-genome sequencing data from the Gabriella Miller Kids First Pediatric Research Program to conduct a gene-based burden analysis to test for genetic modifiers of cleft lip (CL) vs cleft lip and palate (CLP). We found that there was a significantly increased burden of rare variants in SEC24D in CL cases compared to CLP cases (p = 6.86 [Formula: see text] 10-7). Of the 15 variants within SEC24D, 53.3% were synonymous, but overlapped a known craniofacial enhancer. We then tested whether these variants could alter predicted transcription factor binding sites (TFBS), and found that the rare alleles destroyed binding sites for 9 transcription factors (TFs), including Pax1 (p = 0.0009), and created binding sites for 23 TFs, including Pax6 (p = 6.12 [Formula: see text] 10-5) and Pax9 (p = 0.0001), which are known to be involved in normal craniofacial development, suggesting a potential mechanism by which these synonymous variants could have a functional impact. Overall, this study indicates that rare genetic variation may contribute to the phenotypic heterogeneity of OFCs and suggests that regulatory variation may also contribute and warrant further investigation in future studies of genetic variants controlling risk to OFC.
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Affiliation(s)
- Sarah W Curtis
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
| | - Jenna C Carlson
- Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA, 15621, USA
- Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Terri H Beaty
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Jeffrey C Murray
- Department of Pediatrics, University of Iowa, Iowa City, IA, 52242, USA
| | - Seth M Weinberg
- Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Center for Craniofacial and Dental Genetics, Department of Oral and Craniofacial Sciences, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Mary L Marazita
- Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Center for Craniofacial and Dental Genetics, Department of Oral and Craniofacial Sciences, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Justin L Cotney
- Department of Genetics and Genome Sciences, University of Connecticut, Farmington, CT, 06030, USA
| | - David J Cutler
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
| | - Michael P Epstein
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
| | - Elizabeth J Leslie
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA.
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4
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Curtis SW, Carlson JC, Beaty TH, Murray JC, Weinberg SM, Marazita ML, Cotney JL, Cutler DJ, Epstein MP, Leslie EJ. Rare genetic variants in SEC24D modify orofacial cleft phenotypes. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2023:2023.03.24.23287714. [PMID: 37034635 PMCID: PMC10081436 DOI: 10.1101/2023.03.24.23287714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
As one of the most common structural birth defects, orofacial clefts (OFCs) have been studied for decades, and recent studies have demonstrated that there are genetic differences between the different phenotypic presentations of OFCs. However, the contribution of rare genetic variation genome-wide to different subtypes of OFCs has been understudied, with most studies focusing on common genetic variation or rare variation within targeted regions of the genome. Therefore, we used whole-genome sequencing data from the Gabriella Miller Kids First Pediatric Research Program to conduct a gene-based burden analysis to test for genetic modifiers of cleft lip (CL) vs cleft lip and palate (CLP). We found that there was a significantly increased burden of rare variants in SEC24D in CL cases compared to CLP cases (p=6.86×10-7). Of the 15 variants within SEC24D, 53.3% were synonymous, but overlapped a known craniofacial enhancer. We then tested whether these variants could alter predicted transcription factor binding sites (TFBS), and found that the rare alleles destroyed binding sites for 9 transcription factors (TFs), including Pax1 (p=0.0009), and created binding sites for 23 TFs, including Pax6 (p=6.12×10-5) and Pax9 (p= 0.0001), which are known to be involved in normal craniofacial development, suggesting a potential mechanism by which these synonymous variants could have a functional impact. Overall, this study demonstrates that rare genetic variation contributes to the phenotypic heterogeneity of OFCs and suggests that regulatory variation may also contribute and warrant further investigation in future studies of genetic variants controlling risk to OFC.
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Affiliation(s)
- Sarah W Curtis
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
| | - Jenna C Carlson
- Department of Human Genetics, University of Pittsburgh, Pittsburgh, PA, 15621, USA
- Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Terri H Beaty
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205,USA
| | - Jeffrey C Murray
- Department of Pediatrics, University of Iowa, Iowa City, IA, 52242, USA
| | - Seth M Weinberg
- Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Center for Craniofacial and Dental Genetics, Department of Oral and Craniofacial Sciences, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Mary L Marazita
- Department of Biostatistics, University of Pittsburgh, Pittsburgh, PA, 15261, USA
- Center for Craniofacial and Dental Genetics, Department of Oral and Craniofacial Sciences, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Justin L Cotney
- Department of Genetics and Genome Sciences, University of Connecticut, CT, 06030, USA
| | - David J Cutler
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
| | - Michael P Epstein
- Department of Human Genetics, Emory University, Atlanta, GA, 30322, USA
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5
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Deng N, Zhang Y, Ma Z, Lin R, Cheng TH, Tang H, Snyder M, Cohen S. DSIF modulates RNA polymerase II occupancy according to template G + C content. NAR Genom Bioinform 2022; 4:lqac054. [PMID: 35910045 PMCID: PMC9326580 DOI: 10.1093/nargab/lqac054] [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: 04/05/2022] [Revised: 06/03/2022] [Accepted: 07/19/2022] [Indexed: 11/12/2022] Open
Abstract
The DSIF complex comprising the Supt4h and Supt5h transcription elongation proteins clamps RNA polymerase II (RNAPII) onto DNA templates, facilitating polymerase processivity. Lowering DSIF components can differentially decrease expression of alleles containing nucleotide repeat expansions, suggesting that RNAPII transit through repeat expansions is dependent on DSIF functions. To globally identify sequence features that affect dependence of the polymerase on DSIF in human cells, we used ultra-deep ChIP-seq analysis and RNA-seq to investigate and quantify the genome-wide effects of Supt4h loss on template occupancy and transcript production. Our results indicate that RNAPII dependence on Supt4h varies according to G + C content. Effects of DSIF knockdown were prominent during transcription of sequences high in G + C but minimal for sequences low in G + C and were particularly evident for G + C-rich segments of long genes. Reanalysis of previously published ChIP-seq data obtained from mouse cells showed similar effects of template G + C composition on Supt5h actions. Our evidence that DSIF dependency varies globally in different template regions according to template sequence composition suggests that G + C content may have a role in the selectivity of Supt4h knockdown and Supt5h knockdown during transcription of gene alleles containing expansions of G + C-rich repeats.
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Affiliation(s)
- Ning Deng
- Department of Genetics, Stanford University School of Medicine , Stanford, CA 94305, USA
| | - Yue Zhang
- Department of Genetics, Stanford University School of Medicine , Stanford, CA 94305, USA
| | - Zhihai Ma
- Department of Genetics, Stanford University School of Medicine , Stanford, CA 94305, USA
| | - Richard Lin
- Department of Genetics, Stanford University School of Medicine , Stanford, CA 94305, USA
| | - Tzu-Hao Cheng
- Institute of Biochemistry and Molecular Biology, National Yang Ming Chiao Tung University , Taipei 112, Taiwan
| | - Hua Tang
- Department of Genetics, Stanford University School of Medicine , Stanford, CA 94305, USA
| | - Michael P Snyder
- Department of Genetics, Stanford University School of Medicine , Stanford, CA 94305, USA
| | - Stanley N Cohen
- Department of Genetics, Stanford University School of Medicine , Stanford, CA 94305, USA
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6
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Owsian D, Gruchota J, Arnaiz O, Nowak JK. The transient Spt4-Spt5 complex as an upstream regulator of non-coding RNAs during development. Nucleic Acids Res 2022; 50:2603-2620. [PMID: 35188560 PMCID: PMC8934623 DOI: 10.1093/nar/gkac106] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 01/28/2022] [Accepted: 02/04/2022] [Indexed: 12/21/2022] Open
Abstract
The Spt4-Spt5 complex is conserved and essential RNA polymerase elongation factor. To investigate the role of the Spt4-Spt5 complex in non-coding transcription during development, we used the unicellular model Paramecium tetraurelia. In this organism harboring both germline and somatic nuclei, massive transcription of the entire germline genome takes place during meiosis. This phenomenon starts a series of events mediated by different classes of non-coding RNAs that control developmentally programmed DNA elimination. We focused our study on Spt4, a small zinc-finger protein encoded in P. tetraurelia by two genes expressed constitutively and two genes expressed during meiosis. SPT4 genes are not essential in vegetative growth, but they are indispensable for sexual reproduction, even though genes from both expression families show functional redundancy. Silencing of the SPT4 genes resulted in the absence of double-stranded ncRNAs and reduced levels of scnRNAs - 25 nt-long sRNAs produced from these double-stranded precursors in the germline nucleus. Moreover, we observed that the presence of a germline-specific Spt4-Spt5m complex is necessary for transfer of the scnRNA-binding PIWI protein between the germline and somatic nucleus. Our study establishes that Spt4, together with Spt5m, is essential for expression of the germline genome and necessary for developmental genome rearrangements.
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Affiliation(s)
- Dawid Owsian
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Julita Gruchota
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Olivier Arnaiz
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France
| | - Jacek K Nowak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
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7
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Therapeutic strategies for C9orf72 amyotrophic lateral sclerosis and frontotemporal dementia. Curr Opin Neurol 2021; 34:748-755. [PMID: 34392299 PMCID: PMC8678157 DOI: 10.1097/wco.0000000000000984] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW An intronic G4C2 expansion mutation in C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD). Although there are currently no treatments for this insidious, fatal disease, intense research has led to promising therapeutic strategies, which will be discussed here. RECENT FINDINGS Therapeutic strategies for C9-ALS/FTD have primarily focused on reducing the toxic effects of mutant expansion RNAs or the dipeptide repeat proteins (DPRs). The pathogenic effects of G4C2 expansion transcripts have been targeted using approaches aimed at promoting their degradation, inhibiting nuclear export or silencing transcription. Other promising strategies include immunotherapy to reduce the DPRs themselves, reducing RAN translation, removing the repeats using DNA or RNA editing and manipulation of downstream disease-altered stress granule pathways. Finally, understanding the molecular triggers that lead to pheno-conversion may lead to opportunities that can delay symptomatic disease onset. SUMMARY A large body of evidence implicates RAN-translated DPRs as a main driver of C9-ALS/FTD. Promising therapeutic strategies for these devastating diseases are being rapidly developed with several approaches already in or approaching clinical trials.
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Gagliardi D, Costamagna G, Taiana M, Andreoli L, Biella F, Bersani M, Bresolin N, Comi GP, Corti S. Insights into disease mechanisms and potential therapeutics for C9orf72-related amyotrophic lateral sclerosis/frontotemporal dementia. Ageing Res Rev 2020; 64:101172. [PMID: 32971256 DOI: 10.1016/j.arr.2020.101172] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 08/31/2020] [Indexed: 12/12/2022]
Abstract
In 2011, a hexanucleotide repeat expansion (HRE) in the noncoding region of C9orf72 was associated with the most frequent genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). The main pathogenic mechanisms in C9-ALS/FTD are haploinsufficiency of the C9orf72 protein and gain of function toxicity from bidirectionally-transcribed repeat-containing RNAs and dipeptide repeat proteins (DPRs) resulting from non-canonical RNA translation. Additionally, abnormalities in different downstream cellular mechanisms, such as nucleocytoplasmic transport and autophagy, play a role in pathogenesis. Substantial research efforts using in vitro and in vivo models have provided valuable insights into the contribution of each mechanism in disease pathogenesis. However, conflicting evidence exists, and a unifying theory still lacks. Here, we provide an overview of the recently published literature on clinical, neuropathological and molecular features of C9-ALS/FTD. We highlight the supposed neuronal role of C9orf72 and the HRE pathogenic cascade, mainly focusing on the contribution of RNA foci and DPRs to neurodegeneration and discussing the several downstream mechanisms. We summarize the emerging biochemical and neuroimaging biomarkers, as well as the potential therapeutic approaches. Despite promising results, a specific disease-modifying treatment is still not available to date and greater insights into disease mechanisms may help in this direction.
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Affiliation(s)
- Delia Gagliardi
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy
| | - Gianluca Costamagna
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy
| | - Michela Taiana
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy
| | - Luca Andreoli
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy
| | - Fabio Biella
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy
| | - Margherita Bersani
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy
| | - Nereo Bresolin
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy; Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Giacomo Pietro Comi
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy; Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Stefania Corti
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy; Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy.
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9
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McEachin ZT, Parameswaran J, Raj N, Bassell GJ, Jiang J. RNA-mediated toxicity in C9orf72 ALS and FTD. Neurobiol Dis 2020; 145:105055. [PMID: 32829028 DOI: 10.1016/j.nbd.2020.105055] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 07/27/2020] [Accepted: 08/18/2020] [Indexed: 12/13/2022] Open
Abstract
A GGGGCC hexanucleotide repeat expansion in the first intron of C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia. Compelling evidence suggests that gain of toxicity from the bidirectionally transcribed repeat expanded RNAs plays a central role in disease pathogenesis. Two potential mechanisms have been proposed including RNA-mediated toxicity and/or the production of toxic dipeptide repeat proteins. In this review, we focus on the role of RNA mediated toxicity in ALS/FTD caused by the C9orf72 mutation and discuss arguments for and against this mechanism. In addition, we summarize how G4C2 repeat RNAs can elicit toxicity and potential therapeutic strategies to mitigate RNA-mediated toxicity.
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Affiliation(s)
- Zachary T McEachin
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA; Laboratory for Translational Cell Biology, Emory University, Atlanta, GA 30322, USA.
| | | | - Nisha Raj
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA; Laboratory for Translational Cell Biology, Emory University, Atlanta, GA 30322, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA; Laboratory for Translational Cell Biology, Emory University, Atlanta, GA 30322, USA; Department of Neurology, Emory University, Atlanta, GA 30322, USA
| | - Jie Jiang
- Department of Cell Biology, Emory University, Atlanta, GA 30322, USA.
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10
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Goodman LD, Bonini NM. New Roles for Canonical Transcription Factors in Repeat Expansion Diseases. Trends Genet 2019; 36:81-92. [PMID: 31837826 DOI: 10.1016/j.tig.2019.11.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 11/05/2019] [Accepted: 11/08/2019] [Indexed: 12/11/2022]
Abstract
The presence of microsatellite repeat expansions within genes is associated with >30 neurological diseases. Of interest, (GGGGCC)>30-repeats within C9orf72 are associated with amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD). These expansions can be 100s to 1000s of units long. Thus, it is perplexing how RNA-polymerase II (RNAPII) can successfully transcribe them. Recent investigations focusing on GGGGCC-transcription have identified specific, canonical complexes that may promote RNAPII-transcription at these GC-rich microsatellites: the DSIF complex and PAF1C. These complexes may be important for resolving the unique secondary structures formed by GGGGCC-DNA during transcription. Importantly, this process can produce potentially toxic repeat-containing RNA that can encode potentially toxic peptides, impacting neuron function and health. Understanding how transcription of these repeats occurs has implications for therapeutics in multiple diseases.
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Affiliation(s)
- Lindsey D Goodman
- Department of Molecular and Human Genetics, Neurological Research Institute, Baylor College of Medicine, Houston, TX 77030, USA
| | - Nancy M Bonini
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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11
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Yuva-Aydemir Y, Almeida S, Krishnan G, Gendron TF, Gao FB. Transcription elongation factor AFF2/FMR2 regulates expression of expanded GGGGCC repeat-containing C9ORF72 allele in ALS/FTD. Nat Commun 2019; 10:5466. [PMID: 31784536 PMCID: PMC6884579 DOI: 10.1038/s41467-019-13477-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Accepted: 11/11/2019] [Indexed: 12/18/2022] Open
Abstract
Expanded GGGGCC (G4C2) repeats in C9ORF72 cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). How RNAs containing expanded G4C2 repeats are transcribed in human neurons is largely unknown. Here we describe a Drosophila model in which poly(GR) expression in adult neurons causes axonal and locomotor defects and premature death without apparent TDP-43 pathology. In an unbiased genetic screen, partial loss of Lilliputian (Lilli) activity strongly suppresses poly(GR) toxicity by specifically downregulating the transcription of GC-rich sequences in Drosophila. Knockout of AFF2/FMR2 (one of four mammalian homologues of Lilli) with CRISPR-Cas9 decreases the expression of the mutant C9ORF72 allele containing expanded G4C2 repeats and the levels of repeat RNA foci and dipeptide repeat proteins in cortical neurons derived from induced pluripotent stem cells of C9ORF72 patients, resulting in rescue of axonal degeneration and TDP-43 pathology. Thus, AFF2/FMR2 regulates the transcription and toxicity of expanded G4C2 repeats in human C9ORF72-ALS/FTD neurons.
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Affiliation(s)
- Yeliz Yuva-Aydemir
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, 01605, USA
| | - Sandra Almeida
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, 01605, USA.
| | - Gopinath Krishnan
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, 01605, USA
| | - Tania F Gendron
- Department of Neuroscience, Mayo Clinic Florida, Jacksonville, FL, 32224, USA
| | - Fen-Biao Gao
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, 01605, USA.
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Jiang J, Ravits J. Pathogenic Mechanisms and Therapy Development for C9orf72 Amyotrophic Lateral Sclerosis/Frontotemporal Dementia. Neurotherapeutics 2019; 16:1115-1132. [PMID: 31667754 PMCID: PMC6985338 DOI: 10.1007/s13311-019-00797-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In 2011, a hexanucleotide repeat expansion in the first intron of the C9orf72 gene was identified as the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The proposed disease mechanisms include loss of C9orf72 function and gain of toxicity from the bidirectionally transcribed repeat-containing RNAs. Over the last few years, substantial progress has been made to determine the contribution of loss and gain of function in disease pathogenesis. The extensive body of molecular, cellular, animal, and human neuropathological studies is conflicted, but the predominance of evidence favors gain of toxicity as the main pathogenic mechanism for C9orf72 repeat expansions. Alterations in several downstream cellular functions, such as nucleocytoplasmic transport and autophagy, are implicated. Exciting progress has also been made in therapy development targeting this mutation, such as by antisense oligonucleotide therapies targeting sense transcripts and small molecules targeting nucleocytoplasmic transport, and these are now in phase 1 clinical trials.
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Affiliation(s)
- Jie Jiang
- Department of Cell Biology, Emory University, Atlanta, GA, 30322, USA.
| | - John Ravits
- Department of Neurosciences, University of California at San Diego, La Jolla, CA, 92093, USA.
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Nguyen L, Cleary JD, Ranum LPW. Repeat-Associated Non-ATG Translation: Molecular Mechanisms and Contribution to Neurological Disease. Annu Rev Neurosci 2019; 42:227-247. [PMID: 30909783 DOI: 10.1146/annurev-neuro-070918-050405] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Microsatellite mutations involving the expansion of tri-, tetra-, penta-, or hexanucleotide repeats cause more than 40 different neurological disorders. Although, traditionally, the position of the repeat within or outside of an open reading frame has been used to focus research on disease mechanisms involving protein loss of function, protein gain of function, or RNA gain of function, the discoveries of bidirectional transcription and repeat-associated non-ATG (RAN) have blurred these distinctions. Here we review what is known about RAN proteins in disease, the mechanisms by which they are produced, and the novel therapeutic opportunities they provide.
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Affiliation(s)
- Lien Nguyen
- Center for NeuroGenetics, Department of Molecular Genetics and Microbiology, Genetics Institute, and McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610, USA;
| | - John Douglas Cleary
- Center for NeuroGenetics, Department of Molecular Genetics and Microbiology, Genetics Institute, and McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610, USA;
| | - Laura P W Ranum
- Center for NeuroGenetics, Department of Molecular Genetics and Microbiology, Genetics Institute, and McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida 32610, USA;
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