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Thumbadoo KM, Dieriks BV, Murray HC, Swanson MEV, Yoo JH, Mehrabi NF, Turner C, Dragunow M, Faull RLM, Curtis MA, Siddique T, Shaw CE, Newell KL, Henden L, Williams KL, Nicholson GA, Scotter EL. Hippocampal aggregation signatures of pathogenic UBQLN2 in amyotrophic lateral sclerosis and frontotemporal dementia. Brain 2024; 147:3547-3561. [PMID: 38703371 PMCID: PMC11449146 DOI: 10.1093/brain/awae140] [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: 08/02/2023] [Revised: 03/03/2024] [Accepted: 03/07/2024] [Indexed: 05/06/2024] Open
Abstract
Pathogenic variants in the UBQLN2 gene cause X-linked dominant amyotrophic lateral sclerosis and/or frontotemporal dementia characterized by ubiquilin 2 aggregates in neurons of the motor cortex, hippocampus and spinal cord. However, ubiquilin 2 neuropathology is also seen in sporadic and familial amyotrophic lateral sclerosis and/or frontotemporal dementia cases not caused by UBQLN2 pathogenic variants, particularly C9orf72-linked cases. This makes the mechanistic role of mutant ubiquilin 2 protein and the value of ubiquilin 2 pathology for predicting genotype unclear. Here we examine a cohort of 44 genotypically diverse amyotrophic lateral sclerosis cases with or without frontotemporal dementia, including eight cases with UBQLN2 variants [resulting in p.S222G, p.P497H, p.P506S, p.T487I (two cases) and p.P497L (three cases)]. Using multiplexed (five-label) fluorescent immunohistochemistry, we mapped the co-localization of ubiquilin 2 with phosphorylated TDP-43, dipeptide repeat aggregates and p62 in the hippocampus of controls (n = 6), or amyotrophic lateral sclerosis with or without frontotemporal dementia in sporadic (n = 20), unknown familial (n = 3), SOD1-linked (n = 1), FUS-linked (n = 1), C9orf72-linked (n = 5) and UBQLN2-linked (n = 8) cases. We differentiate between (i) ubiquilin 2 aggregation together with phosphorylated TDP-43 or dipeptide repeat proteins; and (ii) ubiquilin 2 self-aggregation promoted by UBQLN2 pathogenic variants that cause amyotrophic lateral sclerosis and/or frontotemporal dementia. Overall, we describe a hippocampal protein aggregation signature that fully distinguishes mutant from wild-type ubiquilin 2 in amyotrophic lateral sclerosis with or without frontotemporal dementia, whereby mutant ubiquilin 2 is more prone than wild-type to aggregate independently of driving factors. This neuropathological signature can be used to assess the pathogenicity of UBQLN2 gene variants and to understand the mechanisms of UBQLN2-linked disease.
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Affiliation(s)
- Kyrah M Thumbadoo
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
| | - Birger V Dieriks
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Helen C Murray
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Molly E V Swanson
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Ji Hun Yoo
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Pharmacology and Clinical Pharmacology, University of Auckland, Auckland 1010, New Zealand
| | - Nasim F Mehrabi
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Clinton Turner
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomical Pathology, LabPlus, Auckland City Hospital, Auckland 1010, New Zealand
| | - Michael Dragunow
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Pharmacology and Clinical Pharmacology, University of Auckland, Auckland 1010, New Zealand
| | - Richard L M Faull
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Maurice A Curtis
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- Department of Anatomy and Medical Imaging, University of Auckland, Auckland 1010, New Zealand
| | - Teepu Siddique
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Department of Cell and Developmental Biology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
| | - Christopher E Shaw
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
- UK Dementia Research Institute Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 8AF, UK
| | - Kathy L Newell
- Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Lyndal Henden
- Macquarie University Motor Neuron Disease Research Centre, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Kelly L Williams
- Macquarie University Motor Neuron Disease Research Centre, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Garth A Nicholson
- Macquarie University Motor Neuron Disease Research Centre, Macquarie Medical School, Faculty of Medicine, Health and Human Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
- Northcott Neuroscience Laboratory, Australian and New Zealand Army Corps (ANZAC) Research Institute, Concord, New South Wales 2139, Australia
- Faculty of Medicine, University of Sydney, Sydney, New South Wales 2050, Australia
- Molecular Medicine Laboratory, Concord Repatriation General Hospital, Concord, New South Wales 2139, Australia
| | - Emma L Scotter
- School of Biological Sciences, University of Auckland, Auckland 1010, New Zealand
- Centre for Brain Research, University of Auckland, Auckland 1010, New Zealand
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2
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Anderson R, Das MR, Chang Y, Farenhem K, Schmitz CO, Jain A. CAG repeat expansions create splicing acceptor sites and produce aberrant repeat-containing RNAs. Mol Cell 2024; 84:702-714.e10. [PMID: 38295802 PMCID: PMC10923110 DOI: 10.1016/j.molcel.2024.01.006] [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: 08/20/2023] [Revised: 11/07/2023] [Accepted: 01/08/2024] [Indexed: 02/04/2024]
Abstract
Expansions of CAG trinucleotide repeats cause several rare neurodegenerative diseases. The disease-causing repeats are translated in multiple reading frames and without an identifiable initiation codon. The molecular mechanism of this repeat-associated non-AUG (RAN) translation is not known. We find that expanded CAG repeats create new splice acceptor sites. Splicing of proximal donors to the repeats produces unexpected repeat-containing transcripts. Upon splicing, depending on the sequences surrounding the donor, CAG repeats may become embedded in AUG-initiated open reading frames. Canonical AUG-initiated translation of these aberrant RNAs may account for proteins that have been attributed to RAN translation. Disruption of the relevant splice donors or the in-frame AUG initiation codons is sufficient to abrogate RAN translation. Our findings provide a molecular explanation for the abnormal translation products observed in CAG trinucleotide repeat expansion disorders and add to the repertoire of mechanisms by which repeat expansion mutations disrupt cellular functions.
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Affiliation(s)
- Rachel Anderson
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA
| | - Michael R Das
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA
| | - Yeonji Chang
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA
| | - Kelsey Farenhem
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA
| | - Cameron O Schmitz
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA
| | - Ankur Jain
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA.
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3
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Ito H, Machida K, Hasumi M, Ueyama M, Nagai Y, Imataka H, Taguchi H. Reconstitution of C9orf72 GGGGCC repeat-associated non-AUG translation with purified human translation factors. Sci Rep 2023; 13:22826. [PMID: 38129650 PMCID: PMC10739749 DOI: 10.1038/s41598-023-50188-z] [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: 08/28/2023] [Accepted: 12/16/2023] [Indexed: 12/23/2023] Open
Abstract
Nucleotide repeat expansion of GGGGCC (G4C2) in the non-coding region of C9orf72 is the most common genetic cause underlying amyotrophic lateral sclerosis and frontotemporal dementia. Transcripts harboring this repeat expansion undergo the translation of dipeptide repeats via a non-canonical process known as repeat-associated non-AUG (RAN) translation. In order to ascertain the essential components required for RAN translation, we successfully recapitulated G4C2-RAN translation using an in vitro reconstituted translation system comprising human factors, namely the human PURE system. Our findings conclusively demonstrate that the presence of fundamental translation factors is sufficient to mediate the elongation from the G4C2 repeat. Furthermore, the initiation mechanism proceeded in a 5' cap-dependent manner, independent of eIF2A or eIF2D. In contrast to cell lysate-mediated RAN translation, where longer G4C2 repeats enhanced translation, we discovered that the expansion of the G4C2 repeats inhibited translation elongation using the human PURE system. These results suggest that the repeat RNA itself functions as a repressor of RAN translation. Taken together, our utilization of a reconstituted RAN translation system employing minimal factors represents a distinctive and potent approach for elucidating the intricacies underlying RAN translation mechanism.
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Grants
- JPMJFS2112 Japan Science and Technology Agency
- JP26116002 Ministry of Education, Culture, Sports, Science and Technology
- JP18H03984 Ministry of Education, Culture, Sports, Science and Technology
- JP21H04763 Ministry of Education, Culture, Sports, Science and Technology
- JP20H05925 Ministry of Education, Culture, Sports, Science and Technology
- 2019-25 Mitsubishi Foundation
- 2019 Uehara Memorial Foundation
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Affiliation(s)
- Hayato Ito
- School of Life Science and Technology, Tokyo Institute of Technology, S2-19, Nagatsuta 4259, Midori-ku, Yokohama, 226-8501, Japan
| | - Kodai Machida
- Graduate School of Engineering, University of Hyogo, Shosha, 2167, Himeji, Hyogo, 671-2280, Japan
| | - Mayuka Hasumi
- School of Life Science and Technology, Tokyo Institute of Technology, S2-19, Nagatsuta 4259, Midori-ku, Yokohama, 226-8501, Japan
| | - Morio Ueyama
- Department of Neurology, Faculty of Medicine, Kindai University, Ohonohigashi 377-2, Osaka-Sayama, 589-8511, Japan
| | - Yoshitaka Nagai
- Department of Neurology, Faculty of Medicine, Kindai University, Ohonohigashi 377-2, Osaka-Sayama, 589-8511, Japan
| | - Hiroaki Imataka
- Graduate School of Engineering, University of Hyogo, Shosha, 2167, Himeji, Hyogo, 671-2280, Japan
| | - Hideki Taguchi
- School of Life Science and Technology, Tokyo Institute of Technology, S2-19, Nagatsuta 4259, Midori-ku, Yokohama, 226-8501, Japan.
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, S2-19, Nagatsuta 4259, Midori-ku, Yokohama, 226-8501, Japan.
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4
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Peng Y, Tu Q, Han Y, Gao L, Wan C. Incidence of different pressure patterns of spinal cerebellar ataxia and analysis of imaging and genetic diagnosis. Open Life Sci 2023; 18:20220762. [PMID: 38152578 PMCID: PMC10751992 DOI: 10.1515/biol-2022-0762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Revised: 09/23/2023] [Accepted: 10/03/2023] [Indexed: 12/29/2023] Open
Abstract
Neurologists have a difficult time identifying sporadic cerebellar ataxia. Multiple system atrophy of the cerebellar type (MSA-C), spontaneous late cortical cerebellar atrophy, and prolonged alcohol use are a few possible causes. In a group of people with sporadic cerebellar ataxia that was not MSA-C, an autosomal-dominant spinocerebellar ataxia (SCA) mutation was recently discovered. Chinese single-hospital cohort will be used in this study to genetic screen for SCA-related genes. One hundred forty individuals with CA were monitored over 8 years. Thirty-one individuals had familial CA, 109 patients had sporadic CA, 73 had MSA-C, and 36 had non-MSA-C sporadic CA. In 28 of the 31 non-MSA-C sporadic patients who requested the test, we carried out gene analysis, including SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA12, SCA17, SCA31, and dentatorubro-pallidoluysian atrophy (DRPLA). The control group consisted of family members of the patients. In 57% of the instances with spontaneous CA that were not MSA-C, gene abnormalities were discovered. The most frequent exception among individuals with sporadic CA was SCA6 (36%), followed by monsters in SCA1, 2, 3, 8, and DRPLA. In contrast, 75% of the patients with familial CA had gene abnormalities, the most frequent of which was SCA6 abnormality. The age of 69 vs 59 was higher, and the CAG repeat length was a minor age of 23 vs 25 in the former instances compared to the last one among individuals with SCA6 anomalies that were sporadic as opposed to familial cases. In sporadic CA, autosomal-dominant mutations in SCA genes, notably in SCA6, are common. Although the cause of the increased incidence of SCA6 mutations is unknown, it may be related to a greater age of onset and varied penetrance of SCA6 mutations.
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Affiliation(s)
- Yufen Peng
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, 330006, China
| | - Qi Tu
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, 330006, China
| | - Yao Han
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, 330006, China
| | - Liang Gao
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, 330006, China
| | - Chenyi Wan
- Department of Neurology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, 330006, China
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5
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Yang S, Wijegunawardana D, Sheth U, Veire AM, Salgado JMS, Agrawal M, Zhou J, Pereira JD, Gendron TF, Guo JU. Aberrant splicing exonizes C9ORF72 repeat expansion in ALS/FTD. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.13.566896. [PMID: 38014069 PMCID: PMC10680656 DOI: 10.1101/2023.11.13.566896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
A nucleotide repeat expansion (NRE) in the first annotated intron of the C9ORF72 gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). While C9 NRE-containing RNAs can be translated into several toxic dipeptide repeat proteins, how an intronic NRE can assess the translation machinery in the cytoplasm remains unclear. By capturing and sequencing NRE-containing RNAs from patient-derived cells, we found that C9 NRE was exonized by the usage of downstream 5' splice sites and exported from the nucleus in a variety of spliced mRNA isoforms. C9ORF72 aberrant splicing was substantially elevated in both C9 NRE+ motor neurons and human brain tissues. Furthermore, NREs above the pathological threshold were sufficient to activate cryptic splice sites in reporter mRNAs. In summary, our results revealed a crucial and potentially widespread role of repeat-induced aberrant splicing in the biogenesis, localization, and translation of NRE-containing RNAs.
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Affiliation(s)
- Suzhou Yang
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT 06520, USA
| | - Denethi Wijegunawardana
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT 06520, USA
| | - Udit Sheth
- Neurobiology of Disease Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences; Jacksonville, FL 32224, USA
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Austin M. Veire
- Neurobiology of Disease Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences; Jacksonville, FL 32224, USA
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Juliana M. S. Salgado
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Manasi Agrawal
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Jeffrey Zhou
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
| | - João D. Pereira
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Tania F. Gendron
- Neurobiology of Disease Graduate Program, Mayo Clinic Graduate School of Biomedical Sciences; Jacksonville, FL 32224, USA
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Junjie U. Guo
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT 06520, USA
- Interdepartmental Neuroscience Program, Yale University, New Haven, CT 06520, USA
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06520, USA
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6
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Anderson R, Das M, Chang Y, Farenhem K, Jain A. CAG repeat expansions create splicing acceptor sites and produce aberrant repeat-containing RNAs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.16.562581. [PMID: 37904984 PMCID: PMC10614865 DOI: 10.1101/2023.10.16.562581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Expansions of CAG trinucleotide repeats cause several rare neurodegenerative diseases. The disease-causing repeats are translated in multiple reading frames, without an identifiable initiation codon. The molecular mechanism of this repeat-associated non-AUG (RAN) translation is not known. We find that expanded CAG repeats create new splice acceptor sites. Splicing of proximal donors to the repeats produces unexpected repeat-containing transcripts. Upon splicing, depending on the sequences surrounding the donor, CAG repeats may become embedded in AUG-initiated open reading frames. Canonical AUG-initiated translation of these aberrant RNAs accounts for proteins that are attributed to RAN translation. Disruption of the relevant splice donors or the in-frame AUG initiation codons is sufficient to abrogate RAN translation. Our findings provide a molecular explanation for the abnormal translation products observed in CAG trinucleotide repeat expansion disorders and add to the repertoire of mechanisms by which repeat expansion mutations disrupt cellular functions.
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Affiliation(s)
- Rachel Anderson
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA
| | - Michael Das
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA
| | - Yeonji Chang
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA
| | - Kelsey Farenhem
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA
| | - Ankur Jain
- Whitehead Institute for Biomedical Research, 455 Main Street, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology, 31 Ames Street, Cambridge, MA 02139, USA
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7
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Latallo MJ, Wang S, Dong D, Nelson B, Livingston NM, Wu R, Zhao N, Stasevich TJ, Bassik MC, Sun S, Wu B. Single-molecule imaging reveals distinct elongation and frameshifting dynamics between frames of expanded RNA repeats in C9ORF72-ALS/FTD. Nat Commun 2023; 14:5581. [PMID: 37696852 PMCID: PMC10495369 DOI: 10.1038/s41467-023-41339-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 08/30/2023] [Indexed: 09/13/2023] Open
Abstract
C9ORF72 hexanucleotide repeat expansion is the most common genetic cause of both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). One pathogenic mechanism is the accumulation of toxic dipeptide repeat (DPR) proteins like poly-GA, GP and GR, produced by the noncanonical translation of the expanded RNA repeats. However, how different DPRs are synthesized remains elusive. Here, we use single-molecule imaging techniques to directly measure the translation dynamics of different DPRs. Besides initiation, translation elongation rates vary drastically between different frames, with GP slower than GA and GR the slowest. We directly visualize frameshift events using a two-color single-molecule translation assay. The repeat expansion enhances frameshifting, but the overall frequency is low. There is a higher chance of GR-to-GA shift than in the reversed direction. Finally, the ribosome-associated protein quality control (RQC) factors ZNF598 and Pelota modulate the translation dynamics, and the repeat RNA sequence is important for invoking the RQC pathway. This study reveals that multiple translation steps modulate the final DPR production. Understanding repeat RNA translation is critically important to decipher the DPR-mediated pathogenesis and identify potential therapeutic targets in C9ORF72-ALS/FTD.
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Affiliation(s)
- Malgorzata J Latallo
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Shaopeng Wang
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Daoyuan Dong
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Blake Nelson
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Nathan M Livingston
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Rong Wu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Ning Zhao
- Department of Biochemistry and Molecular Genetics, University of Colorado-Anschutz Medical Campus, Aurora, CO, 80045, USA
| | - Timothy J Stasevich
- Department of Biochemistry and Molecular Genetics, University of Colorado-Anschutz Medical Campus, Aurora, CO, 80045, USA
| | - Michael C Bassik
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Shuying Sun
- Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
| | - Bin Wu
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
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8
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Morón-Oset J, Fischer LKS, Jauré N, Zhang P, Jahn AJ, Supèr T, Pahl A, Isaacs AM, Grönke S, Partridge L. Repeat length of C9orf72-associated glycine-alanine polypeptides affects their toxicity. Acta Neuropathol Commun 2023; 11:140. [PMID: 37644512 PMCID: PMC10463776 DOI: 10.1186/s40478-023-01634-6] [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: 08/04/2023] [Accepted: 08/05/2023] [Indexed: 08/31/2023] Open
Abstract
G4C2 hexanucleotide repeat expansions in a non-coding region of the C9orf72 gene are the most common cause of familial amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). G4C2 insertion length is variable, and patients can carry up to several thousand repeats. Dipeptide repeat proteins (DPRs) translated from G4C2 transcripts are thought to be a main driver of toxicity. Experiments in model organisms with relatively short DPRs have shown that arginine-rich DPRs are most toxic, while polyGlycine-Alanine (GA) DPRs cause only mild toxicity. However, GA is the most abundant DPR in patient brains, and experimental work in animals has generally relied on the use of low numbers of repeats, with DPRs often tagged for in vivo tracking. Whether repeat length or tagging affect the toxicity of GA has not been systematically assessed. Therefore, we generated Drosophila fly lines expressing GA100, GA200 or GA400 specifically in adult neurons. Consistent with previous studies, expression of GA100 and GA200 caused only mild toxicity. In contrast, neuronal expression of GA400 drastically reduced climbing ability and survival of flies, indicating that long GA DPRs can be highly toxic in vivo. This toxicity could be abolished by tagging GA400. Proteomics analysis of fly brains showed a repeat-length-dependent modulation of the brain proteome, with GA400 causing earlier and stronger changes than shorter GA proteins. PolyGA expression up-regulated proteins involved in ER to Golgi trafficking, and down-regulated proteins involved in insulin signalling. Experimental down-regulation of Tango1, a highly conserved regulator of ER-to Golgi transport, partially rescued GA400 toxicity, suggesting that misregulation of this process contributes to polyGA toxicity. Experimentally increasing insulin signaling also rescued GA toxicity. In summary, our data show that long polyGA proteins can be highly toxic in vivo, and that they may therefore contribute to ALS/FTD pathogenesis in patients.
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Affiliation(s)
- Javier Morón-Oset
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany
| | | | - Nathalie Jauré
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany
| | - Pingze Zhang
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany
| | - Annika Julia Jahn
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany
| | - Tessa Supèr
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany
| | - André Pahl
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany
| | - Adrian M Isaacs
- Department of Neurodegenerative Disease, UCL Institute of Neurology, Queen Square, London, WC1N 3BG, UK
- UK Dementia Research Institute at UCL, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | - Sebastian Grönke
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany.
| | - Linda Partridge
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany.
- Department of Genetics, Evolution and Environment, Institute of Healthy Ageing, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK.
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9
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Wang S, Sun S. Translation dysregulation in neurodegenerative diseases: a focus on ALS. Mol Neurodegener 2023; 18:58. [PMID: 37626421 PMCID: PMC10464328 DOI: 10.1186/s13024-023-00642-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Accepted: 07/21/2023] [Indexed: 08/27/2023] Open
Abstract
RNA translation is tightly controlled in eukaryotic cells to regulate gene expression and maintain proteome homeostasis. RNA binding proteins, translation factors, and cell signaling pathways all modulate the translation process. Defective translation is involved in multiple neurological diseases including amyotrophic lateral sclerosis (ALS). ALS is a progressive neurodegenerative disorder and poses a major public health challenge worldwide. Over the past few years, tremendous advances have been made in the understanding of the genetics and pathogenesis of ALS. Dysfunction of RNA metabolisms, including RNA translation, has been closely associated with ALS. Here, we first introduce the general mechanisms of translational regulation under physiological and stress conditions and review well-known examples of translation defects in neurodegenerative diseases. We then focus on ALS-linked genes and discuss the recent progress on how translation is affected by various mutant genes and the repeat expansion-mediated non-canonical translation in ALS.
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Affiliation(s)
- Shaopeng Wang
- Department of Physiology and Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Shuying Sun
- Department of Physiology and Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA.
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10
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Viera Ortiz AP, Cajka G, Olatunji OA, Mikytuck B, Shalem O, Lee EB. Impaired ribosome-associated quality control of C9orf72 arginine-rich dipeptide-repeat proteins. Brain 2023; 146:2897-2912. [PMID: 36516294 PMCID: PMC10316761 DOI: 10.1093/brain/awac479] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 11/05/2022] [Accepted: 12/06/2022] [Indexed: 12/15/2022] Open
Abstract
Protein quality control pathways have evolved to ensure the fidelity of protein synthesis and efficiently clear potentially toxic protein species. Defects in ribosome-associated quality control and its associated factors have been implicated in the accumulation of aberrant proteins and neurodegeneration. C9orf72 repeat-associated non-AUG translation has been suggested to involve inefficient translation elongation, lead to ribosomal pausing and activation of ribosome-associated quality control pathways. However, the role of the ribosome-associated quality control complex in the processing of proteins generated through this non-canonical translation is not well understood. Here we use reporter constructs containing the C9orf72-associated hexanucleotide repeat, ribosome-associated quality control complex deficient cell models and stain for ribosome-associated quality control markers in C9orf72-expansion carrier human tissue to understand its role in dipeptide-repeat protein pathology. Our studies show that canonical ribosome-associated quality control substrates products are efficiently cleared by the ribosome-associated quality control complex in mammalian cells. Furthermore, using stalling reporter constructs, we show that repeats associated with the C9orf72-expansion induce ribosomal stalling when arginine (R)-rich dipeptide-repeat proteins are synthesized in a length-dependent manner. However, despite triggering this pathway, these arginine-rich dipeptide-repeat proteins are not efficiently processed by the core components of the ribosome-associated quality control complex (listerin, nuclear-export mediator factor and valosin containing protein) partly due to lack of lysine residues, which precludes ubiquitination. Deficient processing by this complex may be implicated in C9orf72-expansion associated disease as dipeptide-repeat protein inclusions were observed to be predominantly devoid of ubiquitin and co-localize with nuclear-export mediator factor in mutation carriers' frontal cortex and cerebellum tissue. These findings suggest that impaired processing of these arginine-rich dipeptide-repeat proteins derived from repeat-associated non-AUG translation by the ribosome-associated quality control complex may contribute to protein homeostasis dysregulation observed in C9orf72-expansion amyotrophic lateral sclerosis and frontotemporal degeneration neuropathogenesis.
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Affiliation(s)
- Ashley P Viera Ortiz
- Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Translational Neuropathology Research Laboratory, Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Gregory Cajka
- Center for Cellular and Molecular Therapeutics, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Olamide A Olatunji
- Translational Neuropathology Research Laboratory, Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Bailey Mikytuck
- Translational Neuropathology Research Laboratory, Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ophir Shalem
- Center for Cellular and Molecular Therapeutics, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
- Department of Genetics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Edward B Lee
- Translational Neuropathology Research Laboratory, Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
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11
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Parameswaran J, Zhang N, Braems E, Tilahun K, Pant DC, Yin K, Asress S, Heeren K, Banerjee A, Davis E, Schwartz SL, Conn GL, Bassell GJ, Van Den Bosch L, Jiang J. Antisense, but not sense, repeat expanded RNAs activate PKR/eIF2α-dependent ISR in C9ORF72 FTD/ALS. eLife 2023; 12:e85902. [PMID: 37073950 PMCID: PMC10188109 DOI: 10.7554/elife.85902] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2023] [Accepted: 04/18/2023] [Indexed: 04/20/2023] Open
Abstract
GGGGCC (G4C2) hexanucleotide repeat expansion in the C9ORF72 gene is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). The repeat is bidirectionally transcribed and confers gain of toxicity. However, the underlying toxic species is debated, and it is not clear whether antisense CCCCGG (C4G2) repeat expanded RNAs contribute to disease pathogenesis. Our study shows that C9ORF72 antisense C4G2 repeat expanded RNAs trigger the activation of the PKR/eIF2α-dependent integrated stress response independent of dipeptide repeat proteins that are produced through repeat-associated non-AUG-initiated translation, leading to global translation inhibition and stress granule formation. Reducing PKR levels with either siRNA or morpholinos mitigates integrated stress response and toxicity caused by the antisense C4G2 RNAs in cell lines, primary neurons, and zebrafish. Increased phosphorylation of PKR/eIF2α is also observed in the frontal cortex of C9ORF72 FTD/ALS patients. Finally, only antisense C4G2, but not sense G4C2, repeat expanded RNAs robustly activate the PKR/eIF2α pathway and induce aberrant stress granule formation. These results provide a mechanism by which antisense C4G2 repeat expanded RNAs elicit neuronal toxicity in FTD/ALS caused by C9ORF72 repeat expansions.
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Affiliation(s)
| | - Nancy Zhang
- Department of Cell Biology, Emory UniversityAtlantaUnited States
| | - Elke Braems
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute, KU LeuvenLeuvenBelgium
- Center for Brain & Disease Research, Laboratory of Neurobiology, VIB, Campus GasthuisbergLeuvenBelgium
| | | | - Devesh C Pant
- Department of Cell Biology, Emory UniversityAtlantaUnited States
| | - Keena Yin
- Department of Cell Biology, Emory UniversityAtlantaUnited States
| | - Seneshaw Asress
- Department of Neurology, Emory UniversityAtlantaUnited States
| | - Kara Heeren
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute, KU LeuvenLeuvenBelgium
- Center for Brain & Disease Research, Laboratory of Neurobiology, VIB, Campus GasthuisbergLeuvenBelgium
| | - Anwesha Banerjee
- Department of Cell Biology, Emory UniversityAtlantaUnited States
| | - Emma Davis
- Department of Cell Biology, Emory UniversityAtlantaUnited States
| | | | - Graeme L Conn
- Department of Biochemistry, Emory UniversityAtlantaUnited States
| | - Gary J Bassell
- Department of Cell Biology, Emory UniversityAtlantaUnited States
| | - Ludo Van Den Bosch
- Department of Neurosciences, Experimental Neurology and Leuven Brain Institute, KU LeuvenLeuvenBelgium
- Center for Brain & Disease Research, Laboratory of Neurobiology, VIB, Campus GasthuisbergLeuvenBelgium
| | - Jie Jiang
- Department of Cell Biology, Emory UniversityAtlantaUnited States
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12
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Wright SE, Todd PK. Native functions of short tandem repeats. eLife 2023; 12:e84043. [PMID: 36940239 PMCID: PMC10027321 DOI: 10.7554/elife.84043] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 03/08/2023] [Indexed: 03/21/2023] Open
Abstract
Over a third of the human genome is comprised of repetitive sequences, including more than a million short tandem repeats (STRs). While studies of the pathologic consequences of repeat expansions that cause syndromic human diseases are extensive, the potential native functions of STRs are often ignored. Here, we summarize a growing body of research into the normal biological functions for repetitive elements across the genome, with a particular focus on the roles of STRs in regulating gene expression. We propose reconceptualizing the pathogenic consequences of repeat expansions as aberrancies in normal gene regulation. From this altered viewpoint, we predict that future work will reveal broader roles for STRs in neuronal function and as risk alleles for more common human neurological diseases.
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Affiliation(s)
- Shannon E Wright
- Department of Neurology, University of Michigan–Ann ArborAnn ArborUnited States
- Neuroscience Graduate Program, University of Michigan–Ann ArborAnn ArborUnited States
- Department of Neuroscience, Picower InstituteCambridgeUnited States
| | - Peter K Todd
- Department of Neurology, University of Michigan–Ann ArborAnn ArborUnited States
- VA Ann Arbor Healthcare SystemAnn ArborUnited States
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13
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Phenotype and management of neurologic intronic repeat disorders (NIRDs). Rev Neurol (Paris) 2023; 179:173-182. [PMID: 36371266 DOI: 10.1016/j.neurol.2022.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2021] [Revised: 09/15/2022] [Accepted: 09/20/2022] [Indexed: 11/11/2022]
Abstract
During recent years an increasing number of neurologic disorders due to expanded tri-, tetra-, penta-, or hexa-nucleotide repeat motifs in introns of various genes have been described (neurologic intronic repeat disorders (NIRDs)). The repeat may be pathogenic in the heterozygous or homozygous form. Repeat lengths vary considerably and can be stable or unstable during transmission to the next generation. The most well-known NIRDs are Friedreich ataxia, spinocerebellar ataxia types-10, -31, and -36, CANVAS, C9Orf72 familial amyotrophic lateral sclerosis (fALS), and myotonic dystrophy-2 (MD2). Phenotypically, NIRDs manifest as mono-organ (e.g. spinocerebellar ataxia type 31) or multi-organ disease (e.g. Friedreich ataxia, myotonic dystrophy-2). A number of other more rare NIRDs have been recently detected. This review aims at summarising and discussing previous findings and recent advances concerning the etiology, pathophysiology, clinical presentation, and therapeutic management of the most common NIRDs.
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14
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Reyes CJF, Asano K. Between Order and Chaos: Understanding the Mechanism and Pathology of RAN Translation. Biol Pharm Bull 2023; 46:139-146. [PMID: 36724941 DOI: 10.1248/bpb.b22-00448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Repeat-associated non-AUG (RAN) translation is a pathogenic mechanism in which repetitive sequences are translated into aggregation-prone proteins from multiple reading frames, even without a canonical AUG start codon. Since its discovery in spinocerebellar ataxia type 8 (SCA8) and myotonic dystrophy type 1 (DM1), RAN translation is now known to occur in the context of 12 disease-linked repeat expansions. This review discusses recent advances in understanding the regulatory mechanisms controlling RAN translation and its contribution to the pathophysiology of repeat expansion diseases. We discuss the key findings in the context of Fragile X Tremor Ataxia Syndrome (FXTAS), a neurodegenerative disorder caused by a CGG repeat expansion in the 5' untranslated region of FMR1.
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Affiliation(s)
| | - Katsura Asano
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University.,Laboratory of Translational Control Study, Graduate School of Integrated Sciences for Life, Hiroshima University.,Hiroshima Research Center for Healthy Aging, Hiroshima University
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15
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Mori K, Gotoh S, Uozumi R, Miyamoto T, Akamine S, Kawabe Y, Tagami S, Ikeda M. RNA Dysmetabolism and Repeat-Associated Non-AUG Translation in Frontotemporal Lobar Degeneration/Amyotrophic Lateral Sclerosis due to C9orf72 Hexanucleotide Repeat Expansion. JMA J 2023; 6:9-15. [PMID: 36793534 PMCID: PMC9908409 DOI: 10.31662/jmaj.2022-0160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 09/26/2022] [Indexed: 01/12/2023] Open
Abstract
Neuropathological features of frontotemporal dementia and amyotrophic lateral sclerosis (ALS) due to C9orf72 GGGGCC hexanucleotide repeat expansion include early dipeptide repeats, repeat RNA foci, and subsequent TDP-43 pathologies. Since the discovery of the repeat expansion, extensive studies have elucidated the disease mechanism of how the repeat causes neurodegeneration. In this review, we summarize our current understanding of abnormal repeat RNA metabolism and repeat-associated non-AUG translation in C9orf72 frontotemporal lobar degeneration/ALS. For repeat RNA metabolism, we specifically focus on the role of hnRNPA3, the repeat RNA-binding protein, and the EXOSC10/RNA exosome complex, an intracellular RNA-degrading enzyme. In addition, the mechanism of repeat-associated non-AUG translation inhibition via TMPyP4, a repeat RNA-binding compound, is discussed.
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Affiliation(s)
- Kohji Mori
- Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Shiho Gotoh
- Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Ryota Uozumi
- Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Tesshin Miyamoto
- Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan,Seifukai Ibaraki Hospital, Ibaraki, Japan
| | - Shoshin Akamine
- Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Yuya Kawabe
- Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan,Minoh Neuropsychiatric Hospital, Minoh, Japan
| | - Shinji Tagami
- Minoh Neuropsychiatric Hospital, Minoh, Japan,Health and Counseling Center, Osaka University, Toyonaka, Japan
| | - Manabu Ikeda
- Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
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16
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Liu Y, Wan L, Ngai CK, Wang Y, Lam SL, Guo P. Structures and conformational dynamics of DNA minidumbbells in pyrimidine-rich repeats associated with neurodegenerative diseases. Comput Struct Biotechnol J 2023; 21:1584-1592. [PMID: 36874156 PMCID: PMC9975016 DOI: 10.1016/j.csbj.2023.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 02/05/2023] [Accepted: 02/05/2023] [Indexed: 02/10/2023] Open
Abstract
Expansions of short tandem repeats (STRs) are associated with approximately 50 human neurodegenerative diseases. These pathogenic STRs are prone to form non-B DNA structure, which has been considered as one of the causative factors for repeat expansions. Minidumbbell (MDB) is a relatively new type of non-B DNA structure formed by pyrimidine-rich STRs. An MDB is composed of two tetraloops or pentaloops, exhibiting a highly compact conformation with extensive loop-loop interactions. The MDB structures have been found to form in CCTG tetranucleotide repeats associated with myotonic dystrophy type 2, ATTCT pentanucleotide repeats associated with spinocerebellar ataxia type 10, and the recently discovered ATTTT/ATTTC repeats associated with spinocerebellar ataxia type 37 and familial adult myoclonic epilepsy. In this review, we first introduce the structures and conformational dynamics of MDBs with a focus on the high-resolution structural information determined by nuclear magnetic resonance spectroscopy. Then we discuss the effects of sequence context, chemical environment, and nucleobase modification on the structure and thermostability of MDBs. Finally, we provide perspectives on further explorations of sequence criteria and biological functions of MDBs.
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Affiliation(s)
- Yuan Liu
- South China Advanced Institute for Soft Matter Science and Technology, School of Emergent Soft Matter, South China University of Technology, Guangzhou, Guangdong 510640, China
| | - Liqi Wan
- School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Cheuk Kit Ngai
- Department of Chemistry, The Chinese University of Hong Kong, Shatin N.T., Hong Kong, China
| | - Yang Wang
- Zhejiang Cancer Hospital, Institute of Basic Medicine and Cancer (IBMC) Chinese Academy of Sciences, Hangzhou, Zhejiang 310022, China
| | - Sik Lok Lam
- Department of Chemistry, The Chinese University of Hong Kong, Shatin N.T., Hong Kong, China
| | - Pei Guo
- Zhejiang Cancer Hospital, Institute of Basic Medicine and Cancer (IBMC) Chinese Academy of Sciences, Hangzhou, Zhejiang 310022, China
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17
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Wright SE, Rodriguez CM, Monroe J, Xing J, Krans A, Flores BN, Barsur V, Ivanova MI, Koutmou KS, Barmada SJ, Todd PK. CGG repeats trigger translational frameshifts that generate aggregation-prone chimeric proteins. Nucleic Acids Res 2022; 50:8674-8689. [PMID: 35904811 PMCID: PMC9410890 DOI: 10.1093/nar/gkac626] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/13/2022] [Indexed: 11/25/2022] Open
Abstract
CGG repeat expansions in the FMR1 5’UTR cause the neurodegenerative disease Fragile X-associated tremor/ataxia syndrome (FXTAS). These repeats form stable RNA secondary structures that support aberrant translation in the absence of an AUG start codon (RAN translation), producing aggregate-prone peptides that accumulate within intranuclear neuronal inclusions and contribute to neurotoxicity. Here, we show that the most abundant RAN translation product, FMRpolyG, is markedly less toxic when generated from a construct with a non-repetitive alternating codon sequence in place of the CGG repeat. While exploring the mechanism of this differential toxicity, we observed a +1 translational frameshift within the CGG repeat from the arginine to glycine reading frame. Frameshifts occurred within the first few translated repeats and were triggered predominantly by RNA sequence and structural features. Short chimeric R/G peptides form aggregates distinct from those formed by either pure arginine or glycine, and these chimeras induce toxicity in cultured rodent neurons. Together, this work suggests that CGG repeats support translational frameshifting and that chimeric RAN translated peptides may contribute to CGG repeat-associated toxicity in FXTAS and related disorders.
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Affiliation(s)
- Shannon E Wright
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Caitlin M Rodriguez
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA.,Department of Genetics, Stanford University School of Medicine, Stanford, CA 84305, USA
| | - Jeremy Monroe
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jiazheng Xing
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Amy Krans
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,VA Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA
| | - Brittany N Flores
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Venkatesha Barsur
- Department of Pathology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Magdalena I Ivanova
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,Biophysics Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Kristin S Koutmou
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sami J Barmada
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA.,VA Ann Arbor Healthcare System, Ann Arbor, MI 48105, USA
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18
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A nop56 Zebrafish Loss-of-Function Model Exhibits a Severe Neurodegenerative Phenotype. Biomedicines 2022; 10:biomedicines10081814. [PMID: 36009362 PMCID: PMC9404972 DOI: 10.3390/biomedicines10081814] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 07/21/2022] [Accepted: 07/22/2022] [Indexed: 11/17/2022] Open
Abstract
NOP56 belongs to a C/D box small nucleolar ribonucleoprotein complex that is in charge of cleavage and modification of precursor ribosomal RNAs and assembly of the 60S ribosomal subunit. An intronic expansion in NOP56 gene causes Spinocerebellar Ataxia type 36, a typical late-onset autosomal dominant ataxia. Although vertebrate animal models were created for the intronic expansion, none was studied for the loss of function of NOP56. We studied a zebrafish loss-of-function model of the nop56 gene which shows 70% homology with the human gene. We observed a severe neurodegenerative phenotype in nop56 mutants, characterized mainly by absence of cerebellum, reduced numbers of spinal cord neurons, high levels of apoptosis in the central nervous system (CNS) and impaired movement, resulting in death before 7 days post-fertilization. Gene expression of genes related to C/D box complex, balance and CNS development was impaired in nop56 mutants. In our study, we characterized the first NOP56 loss-of-function vertebrate model, which is important to further understand the role of NOP56 in CNS function and development.
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19
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Chu TH, Baral K, Labit E, Rosin N, Sinha S, Umansky D, Alzahrani S, Rancourt D, Biernaskie J, Midha R. Comparison of human skin- and nerve-derived Schwann cells reveals many similarities and subtle genomic and functional differences. Glia 2022; 70:2131-2156. [PMID: 35796321 DOI: 10.1002/glia.24242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 06/24/2022] [Accepted: 06/24/2022] [Indexed: 11/08/2022]
Abstract
Skin is an easily accessible tissue and a rich source of Schwann cells (SCs). Toward potential clinical application of autologous SC therapies, we aim to improve the reliability and specificity of our protocol to obtain SCs from small skin samples. As well, to explore potential functional distinctions between skin-derived SCs (Sk-SCs) and nerve-derived SCs (N-SCs), we used single-cell RNA-sequencing and a series of in vitro and in vivo assays. Our results showed that Sk-SCs expressed typical SC markers. Single-cell sequencing of Sk- and N-SCs revealed an overwhelming overlap in gene expression with the exception of HLA genes which were preferentially up-regulated in Sk-SCs. In vitro, both cell types exhibited similar levels of proliferation, migration, uptake of myelin debris and readily associated with neurites when co-cultured with human iPSC-induced motor neurons. Both exhibited ensheathment of multiple neurites and early phase of myelination, especially in N-SCs. Interestingly, dorsal root ganglion (DRG) neurite outgrowth assay showed substantially more complexed neurite outgrowth in DRGs exposed to Sk-SC conditioned media compared to those from N-SCs. Multiplex ELISA array revealed shared growth factor profiles, but Sk-SCs expressed a higher level of VEGF. Transplantation of Sk- and N-SCs into injured peripheral nerve in nude rats and NOD-SCID mice showed close association of both SCs to regenerating axons. Myelination of rodent axons was observed infrequently by N-SCs, but absent in Sk-SC xenografts. Overall, our results showed that Sk-SCs share near-identical properties to N-SCs but with subtle differences that could potentially enhance their therapeutic utility.
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Affiliation(s)
- Tak-Ho Chu
- Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Kabita Baral
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Elodie Labit
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Nicole Rosin
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Sarthak Sinha
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Daniel Umansky
- Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada
| | - Saud Alzahrani
- Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada
| | - Derrick Rancourt
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,McCaig Institute for Bone and Joint Health, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Jeff Biernaskie
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.,Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada.,Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Rajiv Midha
- Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
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20
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Regulating Phase Transition in Neurodegenerative Diseases by Nuclear Import Receptors. BIOLOGY 2022; 11:biology11071009. [PMID: 36101390 PMCID: PMC9311884 DOI: 10.3390/biology11071009] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 06/12/2022] [Accepted: 06/16/2022] [Indexed: 11/17/2022]
Abstract
RNA-binding proteins (RBPs) with a low-complexity prion-like domain (PLD) can undergo aberrant phase transitions and have been implicated in neurodegenerative diseases such as ALS and FTD. Several nuclear RBPs mislocalize to cytoplasmic inclusions in disease conditions. Impairment in nucleocytoplasmic transport is another major event observed in ageing and in neurodegenerative disorders. Nuclear import receptors (NIRs) regulate the nucleocytoplasmic transport of different RBPs bearing a nuclear localization signal by restoring their nuclear localization. NIRs can also specifically dissolve or prevent the aggregation and liquid–liquid phase separation of wild-type or disease-linked mutant RBPs, due to their chaperoning activity. This review focuses on the LLPS of intrinsically disordered proteins and the role of NIRs in regulating LLPS in neurodegeneration. This review also discusses the implication of NIRs as therapeutic agents in neurogenerative diseases.
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21
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Guo P, Han D. Targeting Pathogenic DNA and RNA Repeats: A Conceptual Therapeutic Way for Repeat Expansion Diseases. Chemistry 2022; 28:e202201749. [PMID: 35727679 DOI: 10.1002/chem.202201749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Indexed: 11/06/2022]
Abstract
Expansions of short tandem repeats (STRs) in the human genome cause nearly 50 neurodegenerative diseases, which are mostly inheritable, nonpreventable and incurable, posing as a huge threat to human health. Non-B DNAs formed by STRs are thought to be structural intermediates that can cause repeat expansions. The subsequent transcripts harboring expanded RNA repeats can further induce cellular toxicity through forming specific structures. Direct targeting of these pathogenic DNA and RNA repeats has emerged as a new potential therapeutic strategy to cure repeat expansion diseases. In this conceptual review, we first introduce the roles of DNA and RNA structures in the genetic instabilities and pathomechanisms of repeat expansion diseases, then describe structural features of DNA and RNA repeats with a focus on the tertiary structures determined by X-ray crystallography and solution nuclear magnetic resonance spectroscopy, and finally discuss recent progress and perspectives of developing chemical tools that target pathogenic DNA and RNA repeats for curing repeat expansion diseases.
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Affiliation(s)
- Pei Guo
- The Cancer Hospital of the University of Chinese Academy of Sciences, Zhejiang Cancer Hospital), Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, 310022, P. R. China
| | - Da Han
- The Cancer Hospital of the University of Chinese Academy of Sciences, Zhejiang Cancer Hospital), Hangzhou Institute of Medicine (HIM), Chinese Academy of Sciences, Hangzhou, Zhejiang, 310022, P. R. China.,Institute of Molecular Medicine, Shanghai Key Laboratory for Nucleic Acid Chemistry and Nanomedicine, State Key Laboratory of Oncogenes and Related Genes, Renji Hospital, School of Medicine Shanghai Jiao Tong University, Shanghai, 200127, P. R. China
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22
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Czuppa M, Dhingra A, Zhou Q, Schludi C, König L, Scharf E, Farny D, Dalmia A, Täger J, Castillo-Lizardo M, Katona E, Mori K, Aumer T, Schelter F, Müller M, Carell T, Kalliokoski T, Messinger J, Rizzu P, Heutink P, Edbauer D. Drug screen in iPSC-Neurons identifies nucleoside analogs as inhibitors of (G 4C 2) n expression in C9orf72 ALS/FTD. Cell Rep 2022; 39:110913. [PMID: 35675776 DOI: 10.1016/j.celrep.2022.110913] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 12/22/2021] [Accepted: 05/12/2022] [Indexed: 11/03/2022] Open
Abstract
An intronic (G4C2)n expansion in C9orf72 causes amyotrophic lateral sclerosis and frontotemporal dementia primarily through gain-of-function mechanisms: the accumulation of sense and antisense repeat RNA foci and dipeptide repeat (DPR) proteins (poly-GA/GP/GR/PA/PR) translated from repeat RNA. To therapeutically block this pathway, we screen a library of 1,430 approved drugs and known bioactive compounds in patient-derived induced pluripotent stem cell-derived neurons (iPSC-Neurons) for inhibitors of DPR expression. The clinically used guanosine/cytidine analogs decitabine, entecavir, and nelarabine reduce poly-GA/GP expression, with decitabine being the most potent. Hit compounds nearly abolish sense and antisense RNA foci and reduce expression of the repeat-containing nascent C9orf72 RNA transcript and its mature mRNA with minimal effects on global gene expression, suggesting that they specifically act on repeat transcription. Importantly, decitabine treatment reduces (G4C2)n foci and DPRs in C9orf72 BAC transgenic mice. Our findings suggest that nucleoside analogs are a promising compound class for therapeutic development in C9orf72 repeat-expansion-associated disorders.
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Affiliation(s)
- Mareike Czuppa
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Ashutosh Dhingra
- German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany.
| | - Qihui Zhou
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Carina Schludi
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Laura König
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Elisabeth Scharf
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Daniel Farny
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Anupriya Dalmia
- German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Joachim Täger
- German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | | | - Eszter Katona
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Kohji Mori
- Psychiatry, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Tina Aumer
- Ludwig-Maximilians-University Munich, Faculty of Chemistry and Pharmacy, Munich, Germany
| | - Florian Schelter
- Ludwig-Maximilians-University Munich, Faculty of Chemistry and Pharmacy, Munich, Germany
| | - Markus Müller
- Ludwig-Maximilians-University Munich, Faculty of Chemistry and Pharmacy, Munich, Germany
| | - Thomas Carell
- Ludwig-Maximilians-University Munich, Faculty of Chemistry and Pharmacy, Munich, Germany
| | | | - Josef Messinger
- Orion Corporation Orion Pharma, Medicine Design, Espoo, Finland
| | - Patrizia Rizzu
- German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Peter Heutink
- German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany; Hertie Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Dieter Edbauer
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany; Ludwig-Maximilians-University Munich, Graduate School of Systemic Neurosciences (GSN), Munich, Germany.
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23
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Loveland AB, Svidritskiy E, Susorov D, Lee S, Park A, Zvornicanin S, Demo G, Gao FB, Korostelev AA. Ribosome inhibition by C9ORF72-ALS/FTD-associated poly-PR and poly-GR proteins revealed by cryo-EM. Nat Commun 2022; 13:2776. [PMID: 35589706 PMCID: PMC9120013 DOI: 10.1038/s41467-022-30418-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 04/29/2022] [Indexed: 12/15/2022] Open
Abstract
Toxic dipeptide-repeat (DPR) proteins are produced from expanded G4C2 repeats in the C9ORF72 gene, the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Two DPR proteins, poly-PR and poly-GR, repress cellular translation but the molecular mechanism remains unknown. Here we show that poly-PR and poly-GR of ≥20 repeats inhibit the ribosome's peptidyl-transferase activity at nanomolar concentrations, comparable to specific translation inhibitors. High-resolution cryogenic electron microscopy (cryo-EM) reveals that poly-PR and poly-GR block the polypeptide tunnel of the ribosome, extending into the peptidyl-transferase center (PTC). Consistent with these findings, the macrolide erythromycin, which binds in the tunnel, competes with poly-PR and restores peptidyl-transferase activity. Our results demonstrate that strong and specific binding of poly-PR and poly-GR in the ribosomal tunnel blocks translation, revealing the structural basis of their toxicity in C9ORF72-ALS/FTD.
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Affiliation(s)
- Anna B Loveland
- RNA Therapeutics Institute, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
| | - Egor Svidritskiy
- RNA Therapeutics Institute, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
| | - Denis Susorov
- RNA Therapeutics Institute, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
| | - Soojin Lee
- Department of Neurology, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
| | - Alexander Park
- RNA Therapeutics Institute, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
| | - Sarah Zvornicanin
- RNA Therapeutics Institute, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
| | - Gabriel Demo
- RNA Therapeutics Institute, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA
- Central European Institute of Technology, Masaryk University, Kamenice 5, Brno, 625 00, Czech Republic
| | - Fen-Biao Gao
- Department of Neurology, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA.
| | - Andrei A Korostelev
- RNA Therapeutics Institute, UMass Chan Medical School, 368 Plantation Street, Worcester, MA, 01605, USA.
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Lopez S, He F. Spinocerebellar Ataxia 36: From Mutations Toward Therapies. Front Genet 2022; 13:837690. [PMID: 35309140 PMCID: PMC8931325 DOI: 10.3389/fgene.2022.837690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 02/11/2022] [Indexed: 11/13/2022] Open
Abstract
Spinocerebellar ataxia 36 (SCA36) is a type of repeat expansion-related neurodegenerative disorder identified a decade ago. Like other SCAs, the symptoms of SCA36 include the loss of coordination like gait ataxia and eye movement problems, but motor neuron-related symptoms like muscular atrophy are also present in those patients. The disease is caused by a GGCCTG hexanucleotide repeat expansion in the gene Nop56, and the demographic incidence map showed that this disease was more common among the ethnic groups of Japanese and Spanish descendants. Although the exact mechanisms are still under investigation, the present evidence supports that the expanded repeats may undergo repeat expansion-related non-AUG-initiated translation, and these dipeptide repeat products could be one of the important ways to lead to pathogenesis. Such studies may help develop potential treatments for this disease.
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25
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Boivin M, Charlet-Berguerand N. Trinucleotide CGG Repeat Diseases: An Expanding Field of Polyglycine Proteins? Front Genet 2022; 13:843014. [PMID: 35295941 PMCID: PMC8918734 DOI: 10.3389/fgene.2022.843014] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Accepted: 01/31/2022] [Indexed: 12/30/2022] Open
Abstract
Microsatellites are repeated DNA sequences of 3–6 nucleotides highly variable in length and sequence and that have important roles in genomes regulation and evolution. However, expansion of a subset of these microsatellites over a threshold size is responsible of more than 50 human genetic diseases. Interestingly, some of these disorders are caused by expansions of similar sequences, sizes and localizations and present striking similarities in clinical manifestations and histopathological features, which suggest a common mechanism of disease. Notably, five identical CGG repeat expansions, but located in different genes, are the causes of fragile X-associated tremor/ataxia syndrome (FXTAS), neuronal intranuclear inclusion disease (NIID), oculopharyngodistal myopathy type 1 to 3 (OPDM1-3) and oculopharyngeal myopathy with leukoencephalopathy (OPML), which are neuromuscular and neurodegenerative syndromes with overlapping symptoms and similar histopathological features, notably the presence of characteristic eosinophilic ubiquitin-positive intranuclear inclusions. In this review we summarize recent finding in neuronal intranuclear inclusion disease and FXTAS, where the causing CGG expansions were found to be embedded within small upstream ORFs (uORFs), resulting in their translation into novel proteins containing a stretch of polyglycine (polyG). Importantly, expression of these polyG proteins is toxic in animal models and is sufficient to reproduce the formation of ubiquitin-positive intranuclear inclusions. These data suggest the existence of a novel class of human genetic pathology, the polyG diseases, and question whether a similar mechanism may exist in other diseases, notably in OPDM and OPML.
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26
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Liu F, Morderer D, Wren MC, Vettleson-Trutza SA, Wang Y, Rabichow BE, Salemi MR, Phinney BS, Oskarsson B, Dickson DW, Rossoll W. Proximity proteomics of C9orf72 dipeptide repeat proteins identifies molecular chaperones as modifiers of poly-GA aggregation. Acta Neuropathol Commun 2022; 10:22. [PMID: 35164882 PMCID: PMC8842533 DOI: 10.1186/s40478-022-01322-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 01/25/2022] [Indexed: 12/14/2022] Open
Abstract
The most common inherited cause of two genetically and clinico-pathologically overlapping neurodegenerative diseases, amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), is the presence of expanded GGGGCC intronic hexanucleotide repeats in the C9orf72 gene. Aside from haploinsufficiency and toxic RNA foci, another non-exclusive disease mechanism is the non-canonical translation of the repeat RNA into five different dipeptide repeat proteins (DPRs), which form neuronal inclusions in affected patient brains. While evidence from cellular and animal models supports a toxic gain-of-function of pathologic poly-GA, poly-GR, and poly-PR aggregates in promoting deposition of TDP-43 pathology and neurodegeneration in affected brain areas, the relative contribution of DPRs to the disease process in c9FTD/ALS patients remains unclear. Here we have used the proximity-dependent biotin identification (BioID) proximity proteomics approach to investigate the formation and collective composition of DPR aggregates using cellular models. While interactomes of arginine rich poly-GR and poly-PR aggregates overlapped and were enriched for nucleolar and ribosomal proteins, poly-GA aggregates demonstrated a distinct association with proteasomal components, molecular chaperones (HSPA1A/HSP70, HSPA8/HSC70, VCP/p97), co-chaperones (BAG3, DNAJA1A) and other factors that regulate protein folding and degradation (SQSTM1/p62, CALR, CHIP/STUB1). Experiments in cellular models of poly-GA pathology show that molecular chaperones and co-chaperones are sequestered to the periphery of dense cytoplasmic aggregates, causing depletion from their typical cellular localization. Their involvement in the pathologic process is confirmed in autopsy brain tissue, where HSPA8, BAG3, VCP, and its adapter protein UBXN6 show a close association with poly-GA aggregates in the frontal cortex, temporal cortex, and hippocampus of c9FTLD and c9ALS cases. The association of heat shock proteins and co-chaperones with poly-GA led us to investigate their potential role in reducing its aggregation. We identified HSP40 co-chaperones of the DNAJB family as potent modifiers that increased the solubility of poly-GA, highlighting a possible novel therapeutic avenue and a central role of molecular chaperones in the pathogenesis of human C9orf72-linked diseases.
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Odeh HM, Fare CM, Shorter J. Nuclear-Import Receptors Counter Deleterious Phase Transitions in Neurodegenerative Disease. J Mol Biol 2022; 434:167220. [PMID: 34464655 PMCID: PMC8748273 DOI: 10.1016/j.jmb.2021.167220] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 08/20/2021] [Accepted: 08/24/2021] [Indexed: 01/17/2023]
Abstract
Nuclear-import receptors (NIRs) engage nuclear-localization signals (NLSs) of polypeptides in the cytoplasm and transport these cargo across the size-selective barrier of the nuclear-pore complex into the nucleoplasm. Beyond this canonical role in nuclear transport, NIRs operate in the cytoplasm to chaperone and disaggregate NLS-bearing clients. Indeed, NIRs can inhibit and reverse functional and deleterious phase transitions of their cargo, including several prominent neurodegenerative disease-linked RNA-binding proteins (RBPs) with prion-like domains (PrLDs), such as TDP-43, FUS, EWSR1, TAF15, hnRNPA1, and hnRNPA2. Importantly, elevated NIR expression can mitigate degenerative phenotypes connected to aberrant cytoplasmic aggregation of RBPs with PrLDs. Here, we review recent discoveries that NIRs can also antagonize aberrant interactions and toxicity of arginine-rich, dipeptide-repeat proteins that are associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) caused by G4C2 hexanucleotide repeat expansions in the first intron of C9ORF72. We also highlight recent findings that multiple NIR family members can prevent and reverse liquid-liquid phase separation of specific clients bearing RGG motifs in an NLS-independent manner. Finally, we discuss strategies to enhance NIR activity or expression, which could have therapeutic utility for several neurodegenerative disorders, including ALS, FTD, multisystem proteinopathy, limbic-predominant age-related TDP-43 encephalopathy, tauopathies, and related diseases.
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Affiliation(s)
- Hana M Odeh
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Charlotte M Fare
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. https://twitter.com/CharlotteFare
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA; Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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28
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Wang S, Sun S. Measuring Repeat-Associated Non-AUG (RAN) Translation. Methods Mol Biol 2022; 2428:113-132. [PMID: 35171477 DOI: 10.1007/978-1-0716-1975-9_8] [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] [Indexed: 06/14/2023]
Abstract
Expansions of short nucleotide repeats account for more than 50 neurological or neuromuscular diseases. Many repeat expansion-containing RNAs can generate toxic repeat proteins through repeat-associated non-AUG (RAN) translation in all the reading frames. Understanding how RAN translation occurs and what cellular factors regulate this process will help decipher the basic mechanism of the molecular process and disease pathogenesis. Using reporter systems to quantitatively measure RAN translation provides a platform to examine candidate genes/pathways and screen for modifiers of this non-canonical pathway. In this chapter, we describe the dual-luciferase reporter system to measure RAN translation using C9ORF72 GGGGCCexp as an example, which is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).
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Affiliation(s)
- Shaopeng Wang
- Department of Pathology, Physiology, Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Shuying Sun
- Department of Pathology, Physiology, Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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29
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The molecular pathogenesis of repeat expansion diseases. Biochem Soc Trans 2021; 50:119-134. [PMID: 34940797 DOI: 10.1042/bst20200143] [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] [Received: 09/24/2021] [Revised: 11/30/2021] [Accepted: 12/06/2021] [Indexed: 12/28/2022]
Abstract
Expanded short tandem repeats in the genome cause various monogenic diseases, particularly neurological disorders. Since the discovery of a CGG repeat expansion in the FMR1 gene in 1991, more than 40 repeat expansion diseases have been identified to date. In the coding repeat expansion diseases, in which the expanded repeat sequence is located in the coding regions of genes, the toxicity of repeat polypeptides, particularly misfolding and aggregation of proteins containing an expanded polyglutamine tract, have been the focus of investigation. On the other hand, in the non-coding repeat expansion diseases, in which the expanded repeat sequence is located in introns or untranslated regions, the toxicity of repeat RNAs has been the focus of investigation. Recently, these repeat RNAs were demonstrated to be translated into repeat polypeptides by the novel mechanism of repeat-associated non-AUG translation, which has extended the research direction of the pathological mechanisms of this disease entity to include polypeptide toxicity. Thus, a common pathogenesis has been suggested for both coding and non-coding repeat expansion diseases. In this review, we briefly outline the major pathogenic mechanisms of repeat expansion diseases, including a loss-of-function mechanism caused by repeat expansion, repeat RNA toxicity caused by RNA foci formation and protein sequestration, and toxicity by repeat polypeptides. We also discuss perturbation of the physiological liquid-liquid phase separation state caused by these repeat RNAs and repeat polypeptides, as well as potential therapeutic approaches against repeat expansion diseases.
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30
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Perez BA, Shorrock HK, Banez‐Coronel M, Zu T, Romano LEL, Laboissonniere LA, Reid T, Ikeda Y, Reddy K, Gomez CM, Bird T, Ashizawa T, Schut LJ, Brusco A, Berglund JA, Hasholt LF, Nielsen JE, Subramony SH, Ranum LPW. CCG•CGG interruptions in high-penetrance SCA8 families increase RAN translation and protein toxicity. EMBO Mol Med 2021; 13:e14095. [PMID: 34632710 PMCID: PMC8573593 DOI: 10.15252/emmm.202114095] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 09/09/2021] [Accepted: 09/10/2021] [Indexed: 12/28/2022] Open
Abstract
Spinocerebellar ataxia type 8 (SCA8), a dominantly inherited neurodegenerative disorder caused by a CTG•CAG expansion, is unusual because most individuals that carry the mutation do not develop ataxia. To understand the variable penetrance of SCA8, we studied the molecular differences between highly penetrant families and more common sporadic cases (82%) using a large cohort of SCA8 families (n = 77). We show that repeat expansion mutations from individuals with multiple affected family members have CCG•CGG interruptions at a higher frequency than sporadic SCA8 cases and that the number of CCG•CGG interruptions correlates with age at onset. At the molecular level, CCG•CGG interruptions increase RNA hairpin stability, and in cell culture experiments, increase p-eIF2α and polyAla and polySer RAN protein levels. Additionally, CCG•CGG interruptions, which encode arginine interruptions in the polyGln frame, increase toxicity of the resulting proteins. In summary, SCA8 CCG•CGG interruptions increase polyAla and polySer RAN protein levels, polyGln protein toxicity, and disease penetrance and provide novel insight into the molecular differences between SCA8 families with high vs. low disease penetrance.
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Affiliation(s)
- Barbara A Perez
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- Department of Molecular Genetics and MicrobiologyUniversity of FloridaGainesvilleFLUSA
| | - Hannah K Shorrock
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- Department of Molecular Genetics and MicrobiologyUniversity of FloridaGainesvilleFLUSA
| | - Monica Banez‐Coronel
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- Department of Molecular Genetics and MicrobiologyUniversity of FloridaGainesvilleFLUSA
| | - Tao Zu
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- Department of Molecular Genetics and MicrobiologyUniversity of FloridaGainesvilleFLUSA
| | - Lisa EL Romano
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- Department of Molecular Genetics and MicrobiologyUniversity of FloridaGainesvilleFLUSA
| | - Lauren A Laboissonniere
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- Department of Molecular Genetics and MicrobiologyUniversity of FloridaGainesvilleFLUSA
| | - Tammy Reid
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- Department of Molecular Genetics and MicrobiologyUniversity of FloridaGainesvilleFLUSA
| | - Yoshio Ikeda
- Department of NeurologyGunma UniversityMaebashiJapan
| | - Kaalak Reddy
- RNA InstituteUniversity at Albany–SUNYAlbanyNYUSA
| | | | - Thomas Bird
- Department of NeurologyUniversity of WashingtonSeattleWAUSA
- Geriatrics Research SectionVA Puget Sound Health Care SystemSeattleWAUSA
| | - Tetsuo Ashizawa
- Department of NeurologyHouston Methodist Research InstituteHoustonTXUSA
| | | | - Alfredo Brusco
- Department of Medical SciencesUniversity of TorinoTorinoItaly
- Medical Genetics Units“Città della Salute e della Scienza” University HospitalTorinoItaly
| | - J Andrew Berglund
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- RNA InstituteUniversity at Albany–SUNYAlbanyNYUSA
| | - Lis F Hasholt
- Institute of Cellular and Molecular MedicineUniversity of CopenhagenCopenhagenDenmark
| | - Jorgen E Nielsen
- Department of NeurologyRigshospitaletUniversity of CopenhagenCopenhagenDenmark
| | - SH Subramony
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- McKnight Brain InstituteUniversity of FloridaGainesvilleFLUSA
| | - Laura PW Ranum
- Center for NeuroGeneticsUniversity of FloridaGainesvilleFLUSA
- Department of Molecular Genetics and MicrobiologyUniversity of FloridaGainesvilleFLUSA
- McKnight Brain InstituteUniversity of FloridaGainesvilleFLUSA
- Genetics InstituteUniversity of FloridaGainesvilleFLUSA
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31
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Božič J, Motaln H, Janež AP, Markič L, Tripathi P, Yamoah A, Aronica E, Lee YB, Heilig R, Fischer R, Thompson AJ, Goswami A, Rogelj B. Interactome screening of C9orf72 dipeptide repeats reveals VCP sequestration and functional impairment by polyGA. Brain 2021; 145:684-699. [PMID: 34534264 PMCID: PMC9014755 DOI: 10.1093/brain/awab300] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 07/19/2021] [Accepted: 07/26/2021] [Indexed: 11/25/2022] Open
Abstract
Repeat expansions in the C9orf72 gene are a common cause of amyotrophic lateral sclerosis and frontotemporal lobar degeneration, two devastating neurodegenerative disorders. One of the proposed mechanisms of GGGGCC repeat expansion is their translation into non-canonical dipeptide repeats, which can then accumulate as aggregates and contribute to these pathologies. There are five different dipeptide repeat proteins (polyGA, polyGR, polyPR, polyPA and polyGP), some of which are known to be neurotoxic. In the present study, we used BioID2 proximity labelling to identify the interactomes of all five dipeptide repeat proteins consisting of 125 repeats each. We identified 113 interacting partners for polyGR, 90 for polyGA, 106 for polyPR, 25 for polyPA and 27 for polyGP. Gene Ontology enrichment analysis of the proteomic data revealed that these target interaction partners are involved in a variety of functions, including protein translation, signal transduction pathways, protein catabolic processes, amide metabolic processes and RNA-binding. Using autopsy brain tissue from patients with C9orf72 expansion complemented with cell culture analysis, we evaluated the interactions between polyGA and valosin containing protein (VCP). Functional analysis of this interaction revealed sequestration of VCP with polyGA aggregates, altering levels of soluble valosin-containing protein. VCP also functions in autophagy processes, and consistent with this, we observed altered autophagy in cells expressing polyGA. We also observed altered co-localization of polyGA aggregates and p62 in cells depleted of VCP. All together, these data suggest that sequestration of VCP with polyGA aggregates contributes to the loss of VCP function, and consequently to alterations in autophagy processes in C9orf72 expansion disorders.
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Affiliation(s)
- Janja Božič
- Department of Biotechnology, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Helena Motaln
- Department of Biotechnology, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Anja Pucer Janež
- Department of Biotechnology, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Lara Markič
- Department of Biotechnology, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Priyanka Tripathi
- Institute of Neuropathology, RWTH Aachen University Medical School, Aachen, Germany
| | - Alfred Yamoah
- Institute of Neuropathology, RWTH Aachen University Medical School, Aachen, Germany
| | - Eleonora Aronica
- Amsterdam UMC, University of Amsterdam, Department of (Neuro) Pathology, Amsterdam Neuroscience, Amsterdam, The Netherlands
| | - Youn-Bok Lee
- Maurice Wohl Clinical Neuroscience Institute, King's College London, London, SE5 8AF, UK
| | - Raphael Heilig
- Target Discovery Institute, Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Roman Fischer
- Target Discovery Institute, Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | | | - Anand Goswami
- Institute of Neuropathology, RWTH Aachen University Medical School, Aachen, Germany
| | - Boris Rogelj
- Department of Biotechnology, Jožef Stefan Institute, Ljubljana, Slovenia.,Biomedical Research Institute (BRIS), Ljubljana, Slovenia.,Faculty of Chemistry and Chemical Technology, University of Ljubljana, Ljubljana, Slovenia
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Malik I, Kelley CP, Wang ET, Todd PK. Molecular mechanisms underlying nucleotide repeat expansion disorders. Nat Rev Mol Cell Biol 2021; 22:589-607. [PMID: 34140671 PMCID: PMC9612635 DOI: 10.1038/s41580-021-00382-6] [Citation(s) in RCA: 159] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2021] [Indexed: 02/05/2023]
Abstract
The human genome contains over one million short tandem repeats. Expansion of a subset of these repeat tracts underlies over fifty human disorders, including common genetic causes of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (C9orf72), polyglutamine-associated ataxias and Huntington disease, myotonic dystrophy, and intellectual disability disorders such as Fragile X syndrome. In this Review, we discuss the four major mechanisms by which expansion of short tandem repeats causes disease: loss of function through transcription repression, RNA-mediated gain of function through gelation and sequestration of RNA-binding proteins, gain of function of canonically translated repeat-harbouring proteins, and repeat-associated non-AUG translation of toxic repeat peptides. Somatic repeat instability amplifies these mechanisms and influences both disease age of onset and tissue specificity of pathogenic features. We focus on the crosstalk between these disease mechanisms, and argue that they often synergize to drive pathogenesis. We also discuss the emerging native functions of repeat elements and how their dynamics might contribute to disease at a larger scale than currently appreciated. Lastly, we propose that lynchpins tying these disease mechanisms and native functions together offer promising therapeutic targets with potential shared applications across this class of human disorders.
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Affiliation(s)
- Indranil Malik
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Chase P Kelley
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics, Genetics Institute, University of Florida, Gainesville, FL, USA
- Genetics and Genomics Graduate Program, University of Florida, Gainesville, FL, USA
| | - Eric T Wang
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics, Genetics Institute, University of Florida, Gainesville, FL, USA.
| | - Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA.
- VA Ann Arbor Healthcare System, Ann Arbor, MI, USA.
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Arginine-rich dipeptide-repeat proteins as phase disruptors in C9-ALS/FTD. Emerg Top Life Sci 2021; 4:293-305. [PMID: 32639008 DOI: 10.1042/etls20190167] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 06/15/2020] [Accepted: 06/17/2020] [Indexed: 12/11/2022]
Abstract
A hexanucleotide repeat expansion GGGGCC (G4C2) within chromosome 9 open reading frame 72 (C9orf72) is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (C9-ALS/FTD). This seminal realization has rapidly focused our attention to the non-canonical translation (RAN translation) of the repeat expansion, which yields dipeptide-repeat protein products (DPRs). The mechanisms by which DPRs might contribute to C9-ALS/FTD are widely studied. Arginine-rich DPRs (R-DPRs) are the most toxic of the five different DPRs produced in neurons, but how do R-DPRs promote C9-ALS/FTD pathogenesis? Proteomic analyses have uncovered potential pathways to explore. For example, the vast majority of the R-DPR interactome is comprised of disease-linked RNA-binding proteins (RBPs) with low-complexity domains (LCDs), strongly suggesting a link between R-DPRs and aberrations in liquid-liquid phase separation (LLPS). In this review, we showcase several potential mechanisms by which R-DPRs disrupt various phase-separated compartments to elicit deleterious neurodegeneration. We also discuss potential therapeutic strategies to counter R-DPR toxicity in C9-ALS/FTD.
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Tusi SK, Nguyen L, Thangaraju K, Li J, Cleary JD, Zu T, Ranum LPW. The alternative initiation factor eIF2A plays key role in RAN translation of myotonic dystrophy type 2 CCUG•CAGG repeats. Hum Mol Genet 2021; 30:1020-1029. [PMID: 33856033 DOI: 10.1093/hmg/ddab098] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 03/26/2021] [Accepted: 03/31/2021] [Indexed: 01/29/2023] Open
Abstract
Repeat-associated non-ATG (RAN) proteins have been reported in 11 microsatellite expansion disorders but the factors that allow RAN translation to occur and the effects of different repeat motifs and alternative AUG-like initiation codons are unclear. We studied the mechanisms of RAN translation across myotonic dystrophy type 2 (DM2) expansion transcripts with (CCUG) or without (CAGG) efficient alternative AUG-like codons. To better understand how DM2 LPAC and QAGR RAN proteins are expressed, we generated a series of CRISPR/Cas9-edited HEK293T cell lines. We show that LPAC and QAGR RAN protein levels are reduced in protein kinase R (PKR)-/- and PKR-like endoplasmic reticulum kinase (PERK)-/- cells, with more substantial reductions of CAGG-encoded QAGR in PKR-/- cells. Experiments using mutant eIF2α-S51A HEK293T cells show that p-eIF2α is required for QAGR production. In contrast, LPAC levels were only partially reduced in these cells, suggesting that both non-AUG and close-cognate initiation occur across CCUG RNAs. Overexpression of the alternative initiation factor eIF2A increases LPAC and QAGR protein levels but, notably, has a much larger effect on QAGR expressed from CAGG-expansion RNAs that lack efficient close-cognate codons. The effects of eIF2A on increasing LPAC are consistent with previous reports that eIF2A affects CUG-initiation translation. The observation that eIF2A also increases QAGR proteins is novel because CAGG expansion transcripts do not contain CUG or similarly efficient close-cognate AUG-like codons. For QAGR but not LPAC, the eIF2A-dependent increases are not seen when p-eIF2α is blocked. These data highlight the differential regulation of DM2 RAN proteins and eIF2A as a potential therapeutic target for DM2 and other RAN diseases.
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Affiliation(s)
- Solaleh Khoramian Tusi
- Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Lien Nguyen
- Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Kiruphagaran Thangaraju
- Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Jian Li
- Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - John D Cleary
- Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Tao Zu
- Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Genetics Institute, University of Florida, Gainesville, FL 32610, USA
| | - Laura P W Ranum
- Center for NeuroGenetics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Department of Molecular Genetics and Microbiology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Genetics Institute, University of Florida, Gainesville, FL 32610, USA
- McKnight Brain Institute, University of Florida, Gainesville, FL 32610, USA
- Norman Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL 32610, USA
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Darling AL, Shorter J. Combating deleterious phase transitions in neurodegenerative disease. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2021; 1868:118984. [PMID: 33549703 PMCID: PMC7965345 DOI: 10.1016/j.bbamcr.2021.118984] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/21/2021] [Accepted: 01/22/2021] [Indexed: 12/11/2022]
Abstract
Protein aggregation is a hallmark of neurodegenerative diseases. However, the mechanism that induces pathogenic aggregation is not well understood. Recently, it has emerged that several of the pathological proteins found in an aggregated or mislocalized state in neurodegenerative diseases are also able to undergo liquid-liquid phase separation (LLPS) under physiological conditions. Although these phase transitions are likely important for various physiological functions, neurodegenerative disease-related mutations and conditions can alter the LLPS behavior of these proteins, which can elicit toxicity. Therefore, therapeutics that antagonize aberrant LLPS may be able to mitigate toxicity and aggregation that is ubiquitous in neurodegenerative disease. Here, we discuss the mechanisms by which aberrant protein phase transitions may contribute to neurodegenerative disease. We also outline potential therapeutic strategies to counter deleterious phases. State without borders: Membrane-less organelles and liquid-liquid phase transitions edited by Vladimir N Uversky.
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Affiliation(s)
- April L Darling
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - James Shorter
- Department of Biochemistry and Biophysics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA.
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Schmitz A, Pinheiro Marques J, Oertig I, Maharjan N, Saxena S. Emerging Perspectives on Dipeptide Repeat Proteins in C9ORF72 ALS/FTD. Front Cell Neurosci 2021; 15:637548. [PMID: 33679328 PMCID: PMC7930069 DOI: 10.3389/fncel.2021.637548] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 01/07/2021] [Indexed: 11/13/2022] Open
Abstract
The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is a hexanucleotide expansion in the chromosome 9 open reading frame 72 gene (C9ORF72). This hexanucleotide expansion consists of GGGGCC (G4C2) repeats that have been implicated to lead to three main modes of disease pathology: loss of function of the C9ORF72 protein, the generation of RNA foci, and the production of dipeptide repeat proteins (DPRs) through repeat-associated non-AUG (RAN) translation. Five different DPRs are currently known to be formed: glycine-alanine (GA) and glycine-arginine (GR) from the sense strand, proline-alanine (PA), and proline-arginine (PR) from the antisense strand, and glycine-proline (GP) from both strands. The exact contribution of each DPR to disease pathology is currently under intense scrutiny and is still poorly understood. However, recent advances in both neuropathological and cellular studies have provided us with clues enabling us to better understand the effect of individual DPRs on disease pathogenesis. In this review, we compile the current knowledge of specific DPR involvement on disease development and highlight recent advances, such as the impact of arginine-rich DPRs on nucleolar protein quality control, the correlation of poly-GR with neurodegeneration, and the possible involvement of chimeric DPR species. Further, we discuss recent findings regarding the mechanisms of RAN translation, its modulators, and other promising therapeutic options.
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Affiliation(s)
- Alexander Schmitz
- Department of Neurology, Center for Experimental Neurology, Inselspital University Hospital, Bern, Switzerland
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - João Pinheiro Marques
- Department of Neurology, Center for Experimental Neurology, Inselspital University Hospital, Bern, Switzerland
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Irina Oertig
- Department of Neurology, Center for Experimental Neurology, Inselspital University Hospital, Bern, Switzerland
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Niran Maharjan
- Department of Neurology, Center for Experimental Neurology, Inselspital University Hospital, Bern, Switzerland
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Smita Saxena
- Department of Neurology, Center for Experimental Neurology, Inselspital University Hospital, Bern, Switzerland
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
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Castro AF, Loureiro JR, Bessa J, Silveira I. Antisense Transcription across Nucleotide Repeat Expansions in Neurodegenerative and Neuromuscular Diseases: Progress and Mysteries. Genes (Basel) 2020; 11:E1418. [PMID: 33261024 PMCID: PMC7760973 DOI: 10.3390/genes11121418] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 11/24/2020] [Accepted: 11/24/2020] [Indexed: 12/14/2022] Open
Abstract
Unstable repeat expansions and insertions cause more than 30 neurodegenerative and neuromuscular diseases. Remarkably, bidirectional transcription of repeat expansions has been identified in at least 14 of these diseases. More remarkably, a growing number of studies has been showing that both sense and antisense repeat RNAs are able to dysregulate important cellular pathways, contributing together to the observed clinical phenotype. Notably, antisense repeat RNAs from spinocerebellar ataxia type 7, myotonic dystrophy type 1, Huntington's disease and frontotemporal dementia/amyotrophic lateral sclerosis associated genes have been implicated in transcriptional regulation of sense gene expression, acting either at a transcriptional or posttranscriptional level. The recent evidence that antisense repeat RNAs could modulate gene expression broadens our understanding of the pathogenic pathways and adds more complexity to the development of therapeutic strategies for these disorders. In this review, we cover the amazing progress made in the understanding of the pathogenic mechanisms associated with repeat expansion neurodegenerative and neuromuscular diseases with a focus on the impact of antisense repeat transcription in the development of efficient therapies.
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Affiliation(s)
- Ana F. Castro
- Genetics of Cognitive Dysfunction Laboratory, i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; (A.F.C.); (J.R.L.)
- IBMC-Institute for Molecular and Cell Biology, Universidade do Porto, 4200-135 Porto, Portugal;
- ICBAS, Universidade do Porto, 4050-313 Porto, Portugal
| | - Joana R. Loureiro
- Genetics of Cognitive Dysfunction Laboratory, i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; (A.F.C.); (J.R.L.)
- IBMC-Institute for Molecular and Cell Biology, Universidade do Porto, 4200-135 Porto, Portugal;
| | - José Bessa
- IBMC-Institute for Molecular and Cell Biology, Universidade do Porto, 4200-135 Porto, Portugal;
- Vertebrate Development and Regeneration Laboratory, i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal
| | - Isabel Silveira
- Genetics of Cognitive Dysfunction Laboratory, i3S- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal; (A.F.C.); (J.R.L.)
- IBMC-Institute for Molecular and Cell Biology, Universidade do Porto, 4200-135 Porto, Portugal;
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Ohta Y, Ikegami K, Sato K, Hishikawa N, Omote Y, Takemoto M, Yamashita T, Abe K. Repeat sizes of NOP56 gene in a Japanese Asidan (SCA36) family with clinical anticipation. J Neurol Sci 2020; 418:117150. [PMID: 32980141 DOI: 10.1016/j.jns.2020.117150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 09/18/2020] [Indexed: 11/18/2022]
Affiliation(s)
- Yasuyuki Ohta
- Department of Neurology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Ken Ikegami
- Department of Neurology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Kota Sato
- Department of Neurology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Nozomi Hishikawa
- Department of Neurology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Yoshio Omote
- Department of Neurology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Mami Takemoto
- Department of Neurology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Toru Yamashita
- Department of Neurology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Koji Abe
- Department of Neurology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
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Soluble and insoluble dipeptide repeat protein measurements in C9orf72-frontotemporal dementia brains show regional differential solubility and correlation of poly-GR with clinical severity. Acta Neuropathol Commun 2020; 8:184. [PMID: 33168090 PMCID: PMC7650212 DOI: 10.1186/s40478-020-01036-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 09/06/2020] [Indexed: 12/14/2022] Open
Abstract
A C9orf72 repeat expansion is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis. One of the suggested pathomechanisms is toxicity from dipeptide repeat proteins (DPRs), which are generated via unconventional translation of sense and antisense repeat transcripts with poly-GA, poly-GP and poly-GR being the most abundant dipeptide proteins. Animal and cellular studies highlight a neurotoxic role of poly-GR and poly-PR and to a lesser degree of poly-GA. Human post-mortem studies in contrast have been much less clear on a potential role of DPR toxicity but have largely focused on immunohistochemical methods to detect aggregated DPR inclusions. This study uses protein fractionation and sensitive immunoassays to quantify not only insoluble but also soluble poly-GA, poly-GP and poly-GR concentrations in brain homogenates of FTD patients with C9orf72 mutation across four brain regions. We show that soluble DPRs are less abundant in clinically affected areas (i.e. frontal and temporal cortices). In contrast, the cerebellum not only shows the largest DPR load but also the highest relative DPR solubility. Finally, poly-GR levels and poly-GP solubility correlate with clinical severity. These findings provide the first cross-comparison of soluble and insoluble forms of all sense DPRs and shed light on the distribution and role of soluble DPRs in the etiopathogenesis of human C9orf72-FTD.
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Abstract
Dipeptide repeat proteins (DPRs) occur via repeat-associated non-AUG (RAN) translation. In this issue of Neuron, McEachin et al. (2020) show that the aggregation-prone poly(GA)-rich chimeric DPRs determine divergent poly(GP) mediated pathology between C9ALS/FTD and SCA36.
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Affiliation(s)
- Niran Maharjan
- Department of Neurology, Inselspital University Hospital, 3010 Bern, Switzerland; Department for BioMedical Research, University of Bern, 3008 Bern, Switzerland
| | - Smita Saxena
- Department of Neurology, Inselspital University Hospital, 3010 Bern, Switzerland; Department for BioMedical Research, University of Bern, 3008 Bern, Switzerland.
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Huang M, Modeste E, Dammer E, Merino P, Taylor G, Duong DM, Deng Q, Holler CJ, Gearing M, Dickson D, Seyfried NT, Kukar T. Network analysis of the progranulin-deficient mouse brain proteome reveals pathogenic mechanisms shared in human frontotemporal dementia caused by GRN mutations. Acta Neuropathol Commun 2020; 8:163. [PMID: 33028409 PMCID: PMC7541308 DOI: 10.1186/s40478-020-01037-x] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 09/13/2020] [Indexed: 02/08/2023] Open
Abstract
Heterozygous, loss-of-function mutations in the granulin gene (GRN) encoding progranulin (PGRN) are a common cause of frontotemporal dementia (FTD). Homozygous GRN mutations cause neuronal ceroid lipofuscinosis-11 (CLN11), a lysosome storage disease. PGRN is a secreted glycoprotein that can be proteolytically cleaved into seven bioactive 6 kDa granulins. However, it is unclear how deficiency of PGRN and granulins causes neurodegeneration. To gain insight into the mechanisms of FTD pathogenesis, we utilized Tandem Mass Tag isobaric labeling mass spectrometry to perform an unbiased quantitative proteomic analysis of whole-brain tissue from wild type (Grn+/+) and Grn knockout (Grn-/-) mice at 3- and 19-months of age. At 3-months lysosomal proteins (i.e. Gns, Scarb2, Hexb) are selectively increased indicating lysosomal dysfunction is an early consequence of PGRN deficiency. Additionally, proteins involved in lipid metabolism (Acly, Apoc3, Asah1, Gpld1, Ppt1, and Naaa) are decreased; suggesting lysosomal degradation of lipids may be impaired in the Grn-/- brain. Systems biology using weighted correlation network analysis (WGCNA) of the Grn-/- brain proteome identified 26 modules of highly co-expressed proteins. Three modules strongly correlated to Grn deficiency and were enriched with lysosomal proteins (Gpnmb, CtsD, CtsZ, and Tpp1) and inflammatory proteins (Lgals3, GFAP, CD44, S100a, and C1qa). We find that lysosomal dysregulation is exacerbated with age in the Grn-/- mouse brain leading to neuroinflammation, synaptic loss, and decreased markers of oligodendrocytes, myelin, and neurons. In particular, GPNMB and LGALS3 (galectin-3) were upregulated by microglia and elevated in FTD-GRN brain samples, indicating common pathogenic pathways are dysregulated in human FTD cases and Grn-/- mice. GPNMB levels were significantly increased in the cerebrospinal fluid of FTD-GRN patients, but not in MAPT or C9orf72 carriers, suggesting GPNMB could be a biomarker specific to FTD-GRN to monitor disease onset, progression, and drug response. Our findings support the idea that insufficiency of PGRN and granulins in humans causes neurodegeneration through lysosomal dysfunction, defects in autophagy, and neuroinflammation, which could be targeted to develop effective therapies.
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Park JH, Chung CG, Seo J, Lee BH, Lee YS, Kweon JH, Lee SB. C9orf72-Associated Arginine-Rich Dipeptide Repeat Proteins Reduce the Number of Golgi Outposts and Dendritic Branches in Drosophila Neurons. Mol Cells 2020; 43:821-830. [PMID: 32975212 PMCID: PMC7528685 DOI: 10.14348/molcells.2020.0130] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 08/13/2020] [Accepted: 08/30/2020] [Indexed: 12/11/2022] Open
Abstract
Altered dendritic morphology is frequently observed in various neurological disorders including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), but the cellular and molecular basis underlying these pathogenic dendritic abnormalities remains largely unclear. In this study, we investigated dendritic morphological defects caused by dipeptide repeat protein (DPR) toxicity associated with G4C2 expansion mutation of C9orf72 (the leading genetic cause of ALS and FTD) in Drosophila neurons and characterized the underlying pathogenic mechanisms. Among the five DPRs produced by repeat-associated non-ATG translation of G4C2 repeats, we found that arginine-rich DPRs (PR and GR) led to the most significant reduction in dendritic branches and plasma membrane (PM) supply in Class IV dendritic arborization (C4 da) neurons. Furthermore, expression of PR and GR reduced the number of Golgi outposts (GOPs) in dendrites. In Drosophila brains, expression of PR, but not GR, led to a significant reduction in the mRNA level of CrebA, a transcription factor regulating the formation of GOPs. Overexpressing CrebA in PR-expressing C4 da neurons mitigated PM supply defects and restored the number of GOPs, but the number of dendritic branches remained unchanged, suggesting that other molecules besides CrebA may be involved in dendritic branching. Taken together, our results provide valuable insight into the understanding of dendritic pathology associated with C9-ALS/FTD.
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Affiliation(s)
- Jeong Hyang Park
- Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science & Technology (DGIST), Daegu 42988, Korea
- Protein Dynamics-Based Proteotoxicity Control Laboratory, Basic Research Lab, DGIST, Daegu 4988, Korea
- These authors contributed equally to this work
| | - Chang Geon Chung
- Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science & Technology (DGIST), Daegu 42988, Korea
- Protein Dynamics-Based Proteotoxicity Control Laboratory, Basic Research Lab, DGIST, Daegu 4988, Korea
- These authors contributed equally to this work
| | - Jinsoo Seo
- Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science & Technology (DGIST), Daegu 42988, Korea
- Protein Dynamics-Based Proteotoxicity Control Laboratory, Basic Research Lab, DGIST, Daegu 4988, Korea
| | - Byung-Hoon Lee
- Protein Dynamics-Based Proteotoxicity Control Laboratory, Basic Research Lab, DGIST, Daegu 4988, Korea
- Department of New Biology, DGIST, Daegu 42988, Korea
| | - Young-Sam Lee
- Protein Dynamics-Based Proteotoxicity Control Laboratory, Basic Research Lab, DGIST, Daegu 4988, Korea
- Department of New Biology, DGIST, Daegu 42988, Korea
- Well Aging Research Center, Division of Biotechnology, DGIST, Daegu 2988, Korea
| | - Jung Hyun Kweon
- Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science & Technology (DGIST), Daegu 42988, Korea
| | - Sung Bae Lee
- Department of Brain & Cognitive Sciences, Daegu Gyeongbuk Institute of Science & Technology (DGIST), Daegu 42988, Korea
- Protein Dynamics-Based Proteotoxicity Control Laboratory, Basic Research Lab, DGIST, Daegu 4988, Korea
- Well Aging Research Center, Division of Biotechnology, DGIST, Daegu 2988, Korea
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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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He F, Flores BN, Krans A, Frazer M, Natla S, Niraula S, Adefioye O, Barmada SJ, Todd PK. The carboxyl termini of RAN translated GGGGCC nucleotide repeat expansions modulate toxicity in models of ALS/FTD. Acta Neuropathol Commun 2020; 8:122. [PMID: 32753055 PMCID: PMC7401224 DOI: 10.1186/s40478-020-01002-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Accepted: 07/22/2020] [Indexed: 12/13/2022] Open
Abstract
An intronic hexanucleotide repeat expansion in C9ORF72 causes familial and sporadic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This repeat is thought to elicit toxicity through RNA mediated protein sequestration and repeat-associated non-AUG (RAN) translation of dipeptide repeat proteins (DPRs). We generated a series of transgenic Drosophila models expressing GGGGCC (G4C2) repeats either inside of an artificial intron within a GFP reporter or within the 5' untranslated region (UTR) of GFP placed in different downstream reading frames. Expression of 484 intronic repeats elicited minimal alterations in eye morphology, viability, longevity, or larval crawling but did trigger RNA foci formation, consistent with prior reports. In contrast, insertion of repeats into the 5' UTR elicited differential toxicity that was dependent on the reading frame of GFP relative to the repeat. Greater toxicity correlated with a short and unstructured carboxyl terminus (C-terminus) in the glycine-arginine (GR) RAN protein reading frame. This change in C-terminal sequence triggered nuclear accumulation of all three RAN DPRs. A similar differential toxicity and dependence on the GR C-terminus was observed when repeats were expressed in rodent neurons. The presence of the native C-termini across all three reading frames was partly protective. Taken together, these findings suggest that C-terminal sequences outside of the repeat region may alter the behavior and toxicity of dipeptide repeat proteins derived from GGGGCC repeats.
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