1
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Zhang YE, Stuelten CH. Alternative splicing in EMT and TGF-β signaling during cancer progression. Semin Cancer Biol 2024; 101:1-11. [PMID: 38614376 PMCID: PMC11180579 DOI: 10.1016/j.semcancer.2024.04.001] [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: 05/26/2023] [Revised: 11/20/2023] [Accepted: 04/04/2024] [Indexed: 04/15/2024]
Abstract
Epithelial to mesenchymal transition (EMT) is a physiological process during development where epithelial cells transform to acquire mesenchymal characteristics, which allows them to migrate and colonize secondary tissues. Many cellular signaling pathways and master transcriptional factors exert a myriad of controls to fine tune this vital process to meet various developmental and physiological needs. Adding to the complexity of this network are post-transcriptional and post-translational regulations. Among them, alternative splicing has been shown to play important roles to drive EMT-associated phenotypic changes, including actin cytoskeleton remodeling, cell-cell junction changes, cell motility and invasiveness. In advanced cancers, transforming growth factor-β (TGF-β) is a major inducer of EMT and is associated with tumor cell metastasis, cancer stem cell self-renewal, and drug resistance. This review aims to provide an overview of recent discoveries regarding alternative splicing events and the involvement of splicing factors in the EMT and TGF-β signaling. It will emphasize the importance of various splicing factors involved in EMT and explore their regulatory mechanisms.
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Affiliation(s)
- Ying E Zhang
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.
| | - Christina H Stuelten
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
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2
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Liu D, Dredge BK, Bert AG, Pillman KA, Toubia J, Guo W, Dyakov BA, Migault MM, Conn VM, Conn S, Gregory PA, Gingras AC, Patel D, Wu B, Goodall G. ESRP1 controls biogenesis and function of a large abundant multiexon circRNA. Nucleic Acids Res 2024; 52:1387-1403. [PMID: 38015468 PMCID: PMC10853802 DOI: 10.1093/nar/gkad1138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 10/24/2023] [Accepted: 11/13/2023] [Indexed: 11/29/2023] Open
Abstract
While the majority of circRNAs are formed from infrequent back-splicing of exons from protein coding genes, some can be produced at quite high level and in a regulated manner. We describe the regulation, biogenesis and function of circDOCK1(2-27), a large, abundant circular RNA that is highly regulated during epithelial-mesenchymal transition (EMT) and whose formation depends on the epithelial splicing regulator ESRP1. CircDOCK1(2-27) synthesis in epithelial cells represses cell motility both by diverting transcripts from DOCK1 mRNA production to circRNA formation and by direct inhibition of migration by the circRNA. HITS-CLIP analysis and CRISPR-mediated deletions indicate ESRP1 controls circDOCK1(2-27) biosynthesis by binding a GGU-containing repeat region in intron 1 and detaining its splicing until Pol II completes its 157 kb journey to exon 27. Proximity-dependent biotinylation (BioID) assay suggests ESRP1 may modify the RNP landscape of intron 1 in a way that disfavours communication of exon 1 with exon 2, rather than physically bridging exon 2 to exon 27. The X-ray crystal structure of RNA-bound ESRP1 qRRM2 domain reveals it binds to GGU motifs, with the guanines embedded in clamp-like aromatic pockets in the protein.
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Affiliation(s)
- Dawei Liu
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
| | - B Kate Dredge
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
| | - Andrew G Bert
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
| | - Katherine A Pillman
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA 5005, Australia
| | - John Toubia
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
- ACRF Cancer Genomics Facility, Centre for Cancer Biology, SA Pathology and University of South Australia, Frome Road, Adelaide, SA 5000, Australia
| | - Wenting Guo
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, RNA Biomedical Institute, Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, 510120, China
| | - Boris J A Dyakov
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health, 600 University Ave, Toronto, ON M5G 1X5, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Melodie M Migault
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
| | - Vanessa M Conn
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
- Flinders Health and Medical Research Institute, College of Medicine & Public Health, Flinders University, Bedford Park, SA, 5042, Australia
| | - Simon J Conn
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
- Flinders Health and Medical Research Institute, College of Medicine & Public Health, Flinders University, Bedford Park, SA, 5042, Australia
| | - Philip A Gregory
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
| | - Anne-Claude Gingras
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Sinai Health, 600 University Ave, Toronto, ON M5G 1X5, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Dinshaw Patel
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Baixing Wu
- Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangdong-Hong Kong Joint Laboratory for RNA Medicine, RNA Biomedical Institute, Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, 510120, China
| | - Gregory J Goodall
- Centre for Cancer Biology, SA Pathology and University of South Australia, Adelaide, SA 5000, Australia
- School of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA 5005, Australia
- Adelaide Medical School, Faculty of Health and Medical Sciences, University of Adelaide, Adelaide, SA, Australia
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3
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Jung S, Shah S, Han G, Richter JD. FMRP deficiency leads to multifactorial dysregulation of splicing and mislocalization of MBNL1 to the cytoplasm. PLoS Biol 2023; 21:e3002417. [PMID: 38048343 PMCID: PMC10721184 DOI: 10.1371/journal.pbio.3002417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 12/14/2023] [Accepted: 11/03/2023] [Indexed: 12/06/2023] Open
Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder that is often modeled in Fmr1 knockout mice where the RNA-binding protein FMRP is absent. Here, we show that in Fmr1-deficient mice, RNA mis-splicing occurs in several brain regions and peripheral tissues. To assess molecular mechanisms of splicing mis-regulation, we employed N2A cells depleted of Fmr1. In the absence of FMRP, RNA-specific exon skipping events are linked to the splicing factors hnRNPF, PTBP1, and MBNL1. FMRP regulates the translation of Mbnl1 mRNA as well as Mbnl1 RNA auto-splicing. Elevated Mbnl1 auto-splicing in FMRP-deficient cells results in the loss of a nuclear localization signal (NLS)-containing exon. This in turn alters the nucleus-to-cytoplasm ratio of MBNL1. This redistribution of MBNL1 isoforms in Fmr1-deficient cells could result in downstream splicing changes in other RNAs. Indeed, further investigation revealed that splicing disruptions resulting from Fmr1 depletion could be rescued by overexpression of nuclear MBNL1. Altered Mbnl1 auto-splicing also occurs in human FXS postmortem brain. These data suggest that FMRP-controlled translation and RNA processing may cascade into a general dys-regulation of splicing in Fmr1-deficient cells.
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Affiliation(s)
- Suna Jung
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Sneha Shah
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Geongoo Han
- Molecular Microbiology and Immunology, Brown University, Providence, Rhode Island, United States of America
| | - Joel D. Richter
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
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4
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Verbeeren J, Teixeira J, Garcia SMDA. The Muscleblind-like protein MBL-1 regulates microRNA expression in Caenorhabditis elegans through an evolutionarily conserved autoregulatory mechanism. PLoS Genet 2023; 19:e1011109. [PMID: 38134228 PMCID: PMC10773944 DOI: 10.1371/journal.pgen.1011109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 01/08/2024] [Accepted: 12/12/2023] [Indexed: 12/24/2023] Open
Abstract
The Muscleblind-like (MBNL) family is a highly conserved set of RNA-binding proteins (RBPs) that regulate RNA metabolism during the differentiation of various animal tissues. Functional insufficiency of MBNL affects muscle and central nervous system development, and contributes to the myotonic dystrophies (DM), a set of incurable multisystemic disorders. Studies on the regulation of MBNL genes are essential to provide insight into the gene regulatory networks controlled by MBNL proteins and to understand how dysregulation within these networks causes disease. In this study, we demonstrate the evolutionary conservation of an autoregulatory mechanism that governs the function of MBNL proteins by generating two distinct protein isoform types through alternative splicing. Our aim was to further our understanding of the regulatory principles that underlie this conserved feedback loop in a whole-organismal context, and to address the biological significance of the respective isoforms. Using an alternative splicing reporter, our studies show that, during development of the Caenorhabditis elegans central nervous system, the orthologous mbl-1 gene shifts production from long protein isoforms that localize to the nucleus to short isoforms that also localize to the cytoplasm. Using isoform-specific CRISPR/Cas9-generated strains, we showed that expression of short MBL-1 protein isoforms is required for healthy neuromuscular function and neurodevelopment, while expression of long MBL-1 protein isoforms is dispensable, emphasizing a key role for cytoplasmic functionalities of the MBL-1 protein. Furthermore, RNA-seq and lifespan analyses indicated that short MBL-1 isoforms are crucial regulators of miRNA expression and, in consequence, required for normal lifespan. In conclusion, this study provides support for the disruption of cytoplasmic RNA metabolism as a contributor in myotonic dystrophy and paves the way for further exploration of miRNA regulation through MBNL proteins during development and in disease models.
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Affiliation(s)
- Jens Verbeeren
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Joana Teixeira
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
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5
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Taylor K, Piasecka A, Kajdasz A, Brzęk A, Polay Espinoza M, Bourgeois CF, Jankowski A, Borowiak M, Raczyńska KD, Sznajder ŁJ, Sobczak K. Modulatory role of RNA helicases in MBNL-dependent alternative splicing regulation. Cell Mol Life Sci 2023; 80:335. [PMID: 37882878 PMCID: PMC10602967 DOI: 10.1007/s00018-023-04927-0] [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: 01/31/2023] [Revised: 07/14/2023] [Accepted: 08/17/2023] [Indexed: 10/27/2023]
Abstract
Muscleblind-like splicing regulators (MBNLs) activate or repress the inclusion of alternative splicing (AS) events, enabling the developmental transition of fetal mRNA splicing isoforms to their adult forms. Herein, we sought to elaborate the mechanism by which MBNLs mediate AS related to biological processes. We evaluated the functional role of DEAD-box (DDX) RNA helicases, DDX5 and DDX17 in MBNL-dependent AS regulation. Whole-transcriptome analysis and validation approaches revealed a handful of MBNLs-dependent AS events to be affected by DDX5 and DDX17 in mostly an opposite manner. The opposite expression patterns of these two groups of factors during muscle development and coordination of fetal-to-adult splicing transition indicate the importance of these proteins at early stages of development. The identified pathways of how the helicases modulate MBNL splicing activity include DDX5 and DDX17-dependent changes in the ratio of MBNL splicing isoforms and most likely changes in accessibility of MBNL-binding sites. Another pathway involves the mode of action of the helicases independent of MBNL activity. These findings lead to a deeper understanding of the network of interdependencies between RNA-binding proteins and constitute a valuable element in the discussion on developmental homeostasis and pathological states in which the studied protein factors play a significant role.
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Affiliation(s)
- Katarzyna Taylor
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland.
| | - Agnieszka Piasecka
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland
| | - Arkadiusz Kajdasz
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704, Poznan, Poland
| | - Aleksandra Brzęk
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland
| | - Micaela Polay Espinoza
- Laboratoire de Biologie et Modelisation de la Cellule, Ecole Normale Superieure de Lyon, CNRS, UMR 5239, Inserm, U1293, Universite Claude Bernard Lyon 1, 46 Allee d'Italie, 69364, Lyon, France
| | - Cyril F Bourgeois
- Laboratoire de Biologie et Modelisation de la Cellule, Ecole Normale Superieure de Lyon, CNRS, UMR 5239, Inserm, U1293, Universite Claude Bernard Lyon 1, 46 Allee d'Italie, 69364, Lyon, France
| | - Artur Jankowski
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland
| | - Małgorzata Borowiak
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland
| | - Katarzyna D Raczyńska
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland
| | - Łukasz J Sznajder
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL, 32610, USA
- Department of Chemistry and Biochemistry, University of Nevada, Las Vegas, NV, 89154, USA
| | - Krzysztof Sobczak
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Uniwersytetu Poznanskiego 6, 61-614, Poznan, Poland.
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6
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Puri D, Sharma S, Samaddar S, Ravivarma S, Banerjee S, Ghosh-Roy A. Muscleblind-1 interacts with tubulin mRNAs to regulate the microtubule cytoskeleton in C. elegans mechanosensory neurons. PLoS Genet 2023; 19:e1010885. [PMID: 37603562 PMCID: PMC10470942 DOI: 10.1371/journal.pgen.1010885] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 08/31/2023] [Accepted: 07/26/2023] [Indexed: 08/23/2023] Open
Abstract
Regulation of the microtubule cytoskeleton is crucial for the development and maintenance of neuronal architecture, and recent studies have highlighted the significance of regulated RNA processing in the establishment and maintenance of neural circuits. In a genetic screen conducted using mechanosensory neurons of C. elegans, we identified a mutation in muscleblind-1/mbl-1 as a suppressor of loss of kinesin-13 family microtubule destabilizing factor klp-7. Muscleblind-1(MBL-1) is an RNA-binding protein that regulates the splicing, localization, and stability of RNA. Our findings demonstrate that mbl-1 is required cell-autonomously for axon growth and proper synapse positioning in the posterior lateral microtubule (PLM) neuron. Loss of mbl-1 leads to increased microtubule dynamics and mixed orientation of microtubules in the anterior neurite of PLM. These defects are also accompanied by abnormal axonal transport of the synaptic protein RAB-3 and reduction of gentle touch sensation in mbl-1 mutant. Our data also revealed that mbl-1 is genetically epistatic to mec-7 (β tubulin) and mec-12 (α tubulin) in regulating axon growth. Furthermore, mbl-1 is epistatic to sad-1, an ortholog of BRSK/Brain specific-serine/threonine kinase and a known regulator of synaptic machinery, for synapse formation at the correct location of the PLM neurite. Notably, the immunoprecipitation of MBL-1 resulted in the co-purification of mec-7, mec-12, and sad-1 mRNAs, suggesting a direct interaction between MBL-1 and these transcripts. Additionally, mbl-1 mutants exhibited reduced levels and stability of mec-7 and mec-12 transcripts. Our study establishes a previously unknown link between RNA-binding proteins and cytoskeletal machinery, highlighting their crucial roles in the development and maintenance of the nervous system.
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Affiliation(s)
- Dharmendra Puri
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
| | - Sunanda Sharma
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
| | - Sarbani Samaddar
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
| | - Sruthy Ravivarma
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
| | - Sourav Banerjee
- National Brain Research Centre, Manesar, Gurgaon, Haryana, India
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7
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Jia R, Zheng ZM. Oncogenic SRSF3 in health and diseases. Int J Biol Sci 2023; 19:3057-3076. [PMID: 37416784 PMCID: PMC10321290 DOI: 10.7150/ijbs.83368] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 05/30/2023] [Indexed: 07/08/2023] Open
Abstract
Serine/arginine rich splicing factor 3 (SRSF3) is an important multi-functional splicing factor, and has attracted increasing attentions in the past thirty years. The importance of SRSF3 is evidenced by its impressively conserved protein sequences in all animals and alternative exon 4 which represents an autoregulatory mechanism to maintain its proper cellular expression level. New functions of SRSF3 have been continuously discovered recently, especially its oncogenic function. SRSF3 plays essential roles in many cellular processes by regulating almost all aspects of RNA biogenesis and processing of many target genes, and thus, contributes to tumorigenesis when overexpressed or disregulated. This review updates and highlights the gene, mRNA, and protein structure of SRSF3, the regulatory mechanisms of SRSF3 expression, and the characteristics of SRSF3 targets and binding sequences that contribute to SRSF3's diverse molecular and cellular functions in tumorigenesis and human diseases.
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Affiliation(s)
- Rong Jia
- The State Key Laboratory Breeding Base of Basic Science of Stomatology & Key Laboratory of Oral Biomedicine Ministry of Education, School & Hospital of Stomatology, Wuhan University, Wuhan, Hubei, China
| | - Zhi-Ming Zheng
- Tumor Virus RNA Biology Section, HIV Dynamics and Replication Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, Maryland, USA
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8
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Hildebrandt RP, Moss KR, Janusz-Kaminska A, Knudson LA, Denes LT, Saxena T, Boggupalli DP, Li Z, Lin K, Bassell GJ, Wang ET. Muscleblind-like proteins use modular domains to localize RNAs by riding kinesins and docking to membranes. Nat Commun 2023; 14:3427. [PMID: 37296096 PMCID: PMC10256740 DOI: 10.1038/s41467-023-38923-6] [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: 08/23/2022] [Accepted: 05/22/2023] [Indexed: 06/12/2023] Open
Abstract
RNA binding proteins (RBPs) act as critical facilitators of spatially regulated gene expression. Muscleblind-like (MBNL) proteins, implicated in myotonic dystrophy and cancer, localize RNAs to myoblast membranes and neurites through unknown mechanisms. We find that MBNL forms motile and anchored granules in neurons and myoblasts, and selectively associates with kinesins Kif1bα and Kif1c through its zinc finger (ZnF) domains. Other RBPs with similar ZnFs associate with these kinesins, implicating a motor-RBP specificity code. MBNL and kinesin perturbation leads to widespread mRNA mis-localization, including depletion of Nucleolin transcripts from neurites. Live cell imaging and fractionation reveal that the unstructured carboxy-terminal tail of MBNL1 allows for anchoring at membranes. An approach, termed RBP Module Recruitment and Imaging (RBP-MRI), reconstitutes kinesin- and membrane-recruitment functions using MBNL-MS2 coat protein fusions. Our findings decouple kinesin association, RNA binding, and membrane anchoring functions of MBNL while establishing general strategies for studying multi-functional, modular domains of RBPs.
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Affiliation(s)
- Ryan P Hildebrandt
- Department of Molecular Genetics & Microbiology, Center for Neurogenetics, Genetics Institute, University of Florida, Gainesville, FL, USA
| | - Kathryn R Moss
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | | | - Luke A Knudson
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Lance T Denes
- Department of Molecular Genetics & Microbiology, Center for Neurogenetics, Genetics Institute, University of Florida, Gainesville, FL, USA
| | - Tanvi Saxena
- Department of Molecular Genetics & Microbiology, Center for Neurogenetics, Genetics Institute, University of Florida, Gainesville, FL, USA
| | - Devi Prasad Boggupalli
- Department of Molecular Genetics & Microbiology, Center for Neurogenetics, Genetics Institute, University of Florida, Gainesville, FL, USA
| | - Zhuangyue Li
- Department of Molecular Genetics & Microbiology, Center for Neurogenetics, Genetics Institute, University of Florida, Gainesville, FL, USA
| | - Kun Lin
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA.
| | - Eric T Wang
- Department of Molecular Genetics & Microbiology, Center for Neurogenetics, Genetics Institute, University of Florida, Gainesville, FL, USA.
- Myology Institute, University of Florida, Gainesville, FL, USA.
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9
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How does precursor RNA structure influence RNA processing and gene expression? Biosci Rep 2023; 43:232489. [PMID: 36689327 PMCID: PMC9977717 DOI: 10.1042/bsr20220149] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 01/17/2023] [Accepted: 01/23/2023] [Indexed: 01/24/2023] Open
Abstract
RNA is a fundamental biomolecule that has many purposes within cells. Due to its single-stranded and flexible nature, RNA naturally folds into complex and dynamic structures. Recent technological and computational advances have produced an explosion of RNA structural data. Many RNA structures have regulatory and functional properties. Studying the structure of nascent RNAs is particularly challenging due to their low abundance and long length, but their structures are important because they can influence RNA processing. Precursor RNA processing is a nexus of pathways that determines mature isoform composition and that controls gene expression. In this review, we examine what is known about human nascent RNA structure and the influence of RNA structure on processing of precursor RNAs. These known structures provide examples of how other nascent RNAs may be structured and show how novel RNA structures may influence RNA processing including splicing and polyadenylation. RNA structures can be targeted therapeutically to treat disease.
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10
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Nitschke L, Hu RC, Miller A, Lucas L, Cooper T. Alternative splicing mediates the compensatory upregulation of MBNL2 upon MBNL1 loss-of-function. Nucleic Acids Res 2023; 51:1245-1259. [PMID: 36617982 PMCID: PMC9943662 DOI: 10.1093/nar/gkac1219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 12/05/2022] [Accepted: 01/03/2023] [Indexed: 01/10/2023] Open
Abstract
Loss of gene function can be compensated by paralogs with redundant functions. An example of such compensation are the paralogs of the Muscleblind-Like (MBNL) family of RNA-binding proteins that are sequestered and lose their function in Myotonic Dystrophy Type 1 (DM1). Loss of MBNL1 increases the levels of its paralog MBNL2 in tissues where Mbnl2 expression is low, allowing MBNL2 to functionally compensate for MBNL1 loss. Here, we show that loss of MBNL1 increases the inclusion of Mbnl2 exon 6 and exon 9. We find that inclusion of Mbnl2 exon 6 increases the translocation of MBNL2 to the nucleus, while the inclusion of Mbnl2 exon 9 shifts the reading frame to an alternative C-terminus. We show that the C-terminus lacking exon 9 contains a PEST domain which causes proteasomal degradation. Loss of MBNL1 increases the inclusion of exon 9, resulting in an alternative C-terminus lacking the PEST domain and the increase of MBNL2. We further find that the compensatory mechanism is active in a mouse DM1 model. Together, this study uncovers the compensatory mechanism by which loss of MBNL1 upregulates its paralog MBNL2 and highlights a potential role of the compensatory mechanism in DM1.
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Affiliation(s)
- Larissa Nitschke
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Rong-Chi Hu
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Andrew N Miller
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lathan Lucas
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
- Chemical, Physical & Structural Biology Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA
| | - Thomas A Cooper
- Department of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular & Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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11
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Suárez-Sánchez R, Ávila-Avilés RD, Hernández-Hernández JM, Sánchez-Celis D, Azotla-Vilchis CN, Gómez-Macías ER, Leyva-García N, Ortega A, Magaña JJ, Cisneros B, Hernández-Hernández O. RNA Foci Formation in a Retinal Glial Model for Spinocerebellar Ataxia Type 7. LIFE (BASEL, SWITZERLAND) 2022; 13:life13010023. [PMID: 36675972 PMCID: PMC9861853 DOI: 10.3390/life13010023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/15/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
Spinocerebellar ataxia type 7 (SCA7) is a neurodegenerative disorder characterized by cerebellar ataxia and retinopathy. SCA7 is caused by a CAG expansion in the ATXN7 gene, which results in an extended polyglutamine (polyQ) tract in the encoded protein, the ataxin-7. PolyQ expanded ataxin-7 elicits neurodegeneration in cerebellar Purkinje cells, however, its impact on the SCA7-associated retinopathy remains to be addressed. Since Müller glial cells play an essential role in retinal homeostasis, we generate an inducible model for SCA7, based on the glial Müller MIO-M1 cell line. The SCA7 pathogenesis has been explained by a protein gain-of-function mechanism, however, the contribution of the mutant RNA to the disease cannot be excluded. In this direction, we found nuclear and cytoplasmic foci containing mutant RNA accompanied by subtle alternative splicing defects in MIO-M1 cells. RNA foci were also observed in cells from different lineages, including peripheral mononuclear leukocytes derived from SCA7 patient, suggesting that this molecular mark could be used as a blood biomarker for SCA7. Collectively, our data showed that our glial cell model exhibits the molecular features of SCA7, which makes it a suitable model to study the RNA toxicity mechanisms, as well as to explore therapeutic strategies aiming to alleviate glial dysfunction.
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Affiliation(s)
- Rocío Suárez-Sánchez
- Laboratorio de Medicina Genómica, Departamento de Genética, Instituto Nacional de Rehabilitación-Luis, Guillermo Ibarra Ibarra, Ciudad de México 14389, Mexico
| | - Rodolfo Daniel Ávila-Avilés
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México 07360, Mexico
| | - J. Manuel Hernández-Hernández
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México 07360, Mexico
| | - Daniel Sánchez-Celis
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México 07360, Mexico
| | - Cuauhtli N. Azotla-Vilchis
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México 07360, Mexico
| | - Enue R. Gómez-Macías
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México 07360, Mexico
| | - Norberto Leyva-García
- Laboratorio de Medicina Genómica, Departamento de Genética, Instituto Nacional de Rehabilitación-Luis, Guillermo Ibarra Ibarra, Ciudad de México 14389, Mexico
| | - Arturo Ortega
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del, Instituto Politécnico Nacional, Ciudad de México 07360, Mexico
| | - Jonathan J. Magaña
- Laboratorio de Medicina Genómica, Departamento de Genética, Instituto Nacional de Rehabilitación-Luis, Guillermo Ibarra Ibarra, Ciudad de México 14389, Mexico
- Escuela de Ingeniería y Ciencias, Departamento de Bioingeniería, Tecnológico de Monterrey-Campus Ciudad de México, Ciudad de México 14380, Mexico
| | - Bulmaro Cisneros
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Ciudad de México 07360, Mexico
| | - Oscar Hernández-Hernández
- Laboratorio de Medicina Genómica, Departamento de Genética, Instituto Nacional de Rehabilitación-Luis, Guillermo Ibarra Ibarra, Ciudad de México 14389, Mexico
- Correspondence: or ; Tel.: +52-(55)-5999-1000 (ext. 14710)
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12
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Cognate RNA-Binding Modes by the Alternative-Splicing Regulator MBNL1 Inferred from Molecular Dynamics. Int J Mol Sci 2022; 23:ijms232416147. [PMID: 36555788 PMCID: PMC9780971 DOI: 10.3390/ijms232416147] [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: 11/04/2022] [Revised: 12/06/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
The muscleblind-like protein family (MBNL) plays a prominent role in the regulation of alternative splicing. Consequently, the loss of MBNL function resulting from sequestration by RNA hairpins triggers the development of a neuromuscular disease called myotonic dystrophy (DM). Despite the sequence and structural similarities between the four zinc-finger domains that form MBNL1, recent studies have revealed that the four binding domains have differentiated splicing activity. The dynamic behaviors of MBNL1 ZnFs were simulated using conventional molecular dynamics (cMD) and steered molecular dynamics (sMD) simulations of a structural model of MBNL1 protein to provide insights into the binding selectivity of the four zinc-finger (ZnF) domains toward the GpC steps in YGCY RNA sequence. In accordance with previous studies, our results suggest that both global and local residue fluctuations on each domain have great impacts on triggering alternative splicing, indicating that local motions in RNA-binding domains could modulate their affinity and specificity. In addition, all four ZnF domains provide a distinct RNA-binding environment in terms of structural sampling and mobility that may be involved in the differentiated MBNL1 splicing events reported in the literature.
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13
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The X-linked splicing regulator MBNL3 has been co-opted to restrict placental growth in eutherians. PLoS Biol 2022; 20:e3001615. [PMID: 35476669 PMCID: PMC9084524 DOI: 10.1371/journal.pbio.3001615] [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: 10/13/2021] [Revised: 05/09/2022] [Accepted: 03/29/2022] [Indexed: 11/19/2022] Open
Abstract
Understanding the regulatory interactions that control gene expression during the development of novel tissues is a key goal of evolutionary developmental biology. Here, we show that Mbnl3 has undergone a striking process of evolutionary specialization in eutherian mammals resulting in the emergence of a novel placental function for the gene. Mbnl3 belongs to a family of RNA-binding proteins whose members regulate multiple aspects of RNA metabolism. We find that, in eutherians, while both Mbnl3 and its paralog Mbnl2 are strongly expressed in placenta, Mbnl3 expression has been lost from nonplacental tissues in association with the evolution of a novel promoter. Moreover, Mbnl3 has undergone accelerated protein sequence evolution leading to changes in its RNA-binding specificities and cellular localization. While Mbnl2 and Mbnl3 share partially redundant roles in regulating alternative splicing, polyadenylation site usage and, in turn, placenta maturation, Mbnl3 has also acquired novel biological functions. Specifically, Mbnl3 knockout (M3KO) alone results in increased placental growth associated with higher Myc expression. Furthermore, Mbnl3 loss increases fetal resource allocation during limiting conditions, suggesting that location of Mbnl3 on the X chromosome has led to its role in limiting placental growth, favoring the maternal side of the parental genetic conflict.
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14
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Arandel L, Matloka M, Klein AF, Rau F, Sureau A, Ney M, Cordier A, Kondili M, Polay-Espinoza M, Naouar N, Ferry A, Lemaitre M, Begard S, Colin M, Lamarre C, Tran H, Buée L, Marie J, Sergeant N, Furling D. Reversal of RNA toxicity in myotonic dystrophy via a decoy RNA-binding protein with high affinity for expanded CUG repeats. Nat Biomed Eng 2022; 6:207-220. [PMID: 35145256 DOI: 10.1038/s41551-021-00838-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 12/07/2021] [Indexed: 12/19/2022]
Abstract
Myotonic dystrophy type 1 (DM1) is an RNA-dominant disease whose pathogenesis stems from the functional loss of muscleblind-like RNA-binding proteins (RBPs), which causes the formation of alternative-splicing defects. The loss of functional muscleblind-like protein 1 (MBNL1) results from its nuclear sequestration by mutant transcripts containing pathogenic expanded CUG repeats (CUGexp). Here we show that an RBP engineered to act as a decoy for CUGexp reverses the toxicity of the mutant transcripts. In vitro, the binding of the RBP decoy to CUGexp in immortalized muscle cells derived from a patient with DM1 released sequestered endogenous MBNL1 from nuclear RNA foci, restored MBNL1 activity, and corrected the transcriptomic signature of DM1. In mice with DM1, the local or systemic delivery of the RBP decoy via an adeno-associated virus into the animals' skeletal muscle led to the long-lasting correction of the splicing defects and to ameliorated disease pathology. Our findings support the development of decoy RBPs with high binding affinities for expanded RNA repeats as a therapeutic strategy for myotonic dystrophies.
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Affiliation(s)
- Ludovic Arandel
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Magdalena Matloka
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Arnaud F Klein
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Frédérique Rau
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Alain Sureau
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Michel Ney
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Aurélien Cordier
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Maria Kondili
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Micaela Polay-Espinoza
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Naira Naouar
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Arnaud Ferry
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France.,Sorbonne Paris Cité, Université Paris Descartes, Paris, France
| | - Mégane Lemaitre
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France.,Sorbonne Université, Inserm, Phénotypage du petit animal, Paris, France
| | - Séverine Begard
- Université de Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, Lille, France
| | - Morvane Colin
- Université de Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, Lille, France
| | - Chloé Lamarre
- Université de Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, Lille, France
| | - Hélène Tran
- Université de Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, Lille, France
| | - Luc Buée
- Université de Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, Lille, France
| | - Joëlle Marie
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France
| | - Nicolas Sergeant
- Université de Lille, Inserm, CHU Lille, Lille Neuroscience and Cognition, Lille, France.
| | - Denis Furling
- Sorbonne Université, Inserm, Institut de Myologie, Centre de Recherche en Myologie, Paris, France.
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Hinman MN, Richardson JI, Sockol RA, Aronson ED, Stednitz SJ, Murray KN, Berglund JA, Guillemin K. Zebrafish mbnl mutants model physical and molecular phenotypes of myotonic dystrophy. Dis Model Mech 2021; 14:dmm045773. [PMID: 34125183 PMCID: PMC8246264 DOI: 10.1242/dmm.045773] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 05/04/2021] [Indexed: 12/12/2022] Open
Abstract
The muscleblind RNA-binding proteins (MBNL1, MBNL2 and MBNL3) are highly conserved across vertebrates and are important regulators of RNA alternative splicing. Loss of MBNL protein function through sequestration by CUG or CCUG RNA repeats is largely responsible for the phenotypes of the human genetic disorder myotonic dystrophy (DM). We generated the first stable zebrafish (Danio rerio) models of DM-associated MBNL loss of function through mutation of the three zebrafish mbnl genes. In contrast to mouse models, zebrafish double and triple homozygous mbnl mutants were viable to adulthood. Zebrafish mbnl mutants displayed disease-relevant physical phenotypes including decreased body size and impaired movement. They also exhibited widespread alternative splicing changes, including the misregulation of many DM-relevant exons. Physical and molecular phenotypes were more severe in compound mbnl mutants than in single mbnl mutants, suggesting partially redundant functions of Mbnl proteins. The high fecundity and larval optical transparency of this complete series of zebrafish mbnl mutants will make them useful for studying DM-related phenotypes and how individual Mbnl proteins contribute to them, and for testing potential therapeutics. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Melissa N. Hinman
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Jared I. Richardson
- RNA Institute, State University of New York at Albany, Albany, NY 12222, USA
- Department of Biochemistry and Molecular Biology, Center for NeuroGenetics, University of Florida, Gainesville, FL 32611, USA
| | - Rose A. Sockol
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Eliza D. Aronson
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Sarah J. Stednitz
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA
| | - Katrina N. Murray
- Zebrafish International Resource Center, University of Oregon, Eugene, OR 97403, USA
| | - J. Andrew Berglund
- RNA Institute, State University of New York at Albany, Albany, NY 12222, USA
- Department of Biochemistry and Molecular Biology, Center for NeuroGenetics, University of Florida, Gainesville, FL 32611, USA
| | - Karen Guillemin
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
- Humans and the Microbiome Program, CIFAR, Toronto, ON M5G 1M1, Canada
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16
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Chen YS, Liu CW, Lin YC, Tsai CY, Yang CH, Lin JC. The SRSF3-MBNL1-Acin1 circuit constitutes an emerging axis to lessen DNA fragmentation in colorectal cancer via an alternative splicing mechanism. Neoplasia 2020; 22:702-713. [PMID: 33142236 PMCID: PMC7586066 DOI: 10.1016/j.neo.2020.10.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/30/2020] [Accepted: 10/04/2020] [Indexed: 02/07/2023] Open
Abstract
Altered alternative splicing (AS) events are considered pervasive causes that result in the development of carcinogenesis. Herein, we identified reprogrammed expression and splicing profiles of Muscle blind-like protein 1 (MBNL1) transcripts in tumorous tissues compared to those of adjacent normal tissues dissected from individual colorectal cancer (CRC) patients using whole-transcriptome analyses. MBNL1 transcript 8 (MBNL18) containing exons 5 and 7 was majorly generated by cancerous tissues and CRC-derived cell lines compared with those of the normal counterparts. Interplay between the exonic CA-rich element and upregulated SRSF3 facilitated the inclusion of MBNL1 exons 5 and 7, which encode a bipartite nuclear localization signal (NLS) and conformational NLS. Moreover, abundant SRSF3 interfered with the autoregulatory mechanism involved in utilization of MBNL1 exons 5 and 7, resulting in enrichment of the MBNL18 isoform in cultured CRC cell lines. Subsequently, an increase in the MBNL18 isoform drove a shift in the apoptotic chromatin condensation inducer in nucleus 1-S (Acin1-S) isoform to the Acin1-L isoform, leading to diminished DNA fragmentation in cultured CRC cells under oxidative stress. Taken together, SRSF3-MBNL1-Acin1 was demonstrated to constitute an emerging axis which is relevant to proapoptotic signatures and post-transcriptional events of CRC cells.
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Affiliation(s)
- Yi-Su Chen
- Department of Family Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Chao-Wei Liu
- Ph.D. Program in Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; Department of Laboratory Science, National Taiwan University Hospital, Taipei, Taiwan
| | - Ying-Chin Lin
- Department of Family Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan; Department of Family Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chia-Ying Tsai
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Ching-Hui Yang
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Jung-Chun Lin
- Ph.D. Program in Medical Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; Pulmonary Research Center, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.
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17
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An Overview of Alternative Splicing Defects Implicated in Myotonic Dystrophy Type I. Genes (Basel) 2020; 11:genes11091109. [PMID: 32971903 PMCID: PMC7564762 DOI: 10.3390/genes11091109] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/14/2020] [Accepted: 09/17/2020] [Indexed: 01/02/2023] Open
Abstract
Myotonic dystrophy type I (DM1) is the most common form of adult muscular dystrophy, caused by expansion of a CTG triplet repeat in the 3′ untranslated region (3′UTR) of the myotonic dystrophy protein kinase (DMPK) gene. The pathological CTG repeats result in protein trapping by expanded transcripts, a decreased DMPK translation and the disruption of the chromatin structure, affecting neighboring genes expression. The muscleblind-like (MBNL) and CUG-BP and ETR-3-like factors (CELF) are two families of tissue-specific regulators of developmentally programmed alternative splicing that act as antagonist regulators of several pre-mRNA targets, including troponin 2 (TNNT2), insulin receptor (INSR), chloride channel 1 (CLCN1) and MBNL2. Sequestration of MBNL proteins and up-regulation of CELF1 are key to DM1 pathology, inducing a spliceopathy that leads to a developmental remodelling of the transcriptome due to an adult-to-foetal splicing switch, which results in the loss of cell function and viability. Moreover, recent studies indicate that additional pathogenic mechanisms may also contribute to disease pathology, including a misregulation of cellular mRNA translation, localization and stability. This review focuses on the cause and effects of MBNL and CELF1 deregulation in DM1, describing the molecular mechanisms underlying alternative splicing misregulation for a deeper understanding of DM1 complexity. To contribute to this analysis, we have prepared a comprehensive list of transcript alterations involved in DM1 pathogenesis, as well as other deregulated mRNA processing pathways implications.
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18
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Taylor K, Sobczak K. Intrinsic Regulatory Role of RNA Structural Arrangement in Alternative Splicing Control. Int J Mol Sci 2020; 21:ijms21145161. [PMID: 32708277 PMCID: PMC7404189 DOI: 10.3390/ijms21145161] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 07/17/2020] [Indexed: 12/14/2022] Open
Abstract
Alternative splicing is a highly sophisticated process, playing a significant role in posttranscriptional gene expression and underlying the diversity and complexity of organisms. Its regulation is multilayered, including an intrinsic role of RNA structural arrangement which undergoes time- and tissue-specific alterations. In this review, we describe the principles of RNA structural arrangement and briefly decipher its cis- and trans-acting cellular modulators which serve as crucial determinants of biological functionality of the RNA structure. Subsequently, we engage in a discussion about the RNA structure-mediated mechanisms of alternative splicing regulation. On one hand, the impairment of formation of optimal RNA structures may have critical consequences for the splicing outcome and further contribute to understanding the pathomechanism of severe disorders. On the other hand, the structural aspects of RNA became significant features taken into consideration in the endeavor of finding potential therapeutic treatments. Both aspects have been addressed by us emphasizing the importance of ongoing studies in both fields.
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19
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Ray D, Yun YC, Idris M, Cheng S, Boot A, Iain TBH, Rozen SG, Tan P, Epstein DM. A tumor-associated splice-isoform of MAP2K7 drives dedifferentiation in MBNL1-low cancers via JNK activation. Proc Natl Acad Sci U S A 2020; 117:16391-16400. [PMID: 32601196 PMCID: PMC7368273 DOI: 10.1073/pnas.2002499117] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Master splicing regulator MBNL1 shapes large transcriptomic changes that drive cellular differentiation during development. Here we demonstrate that MBNL1 is a suppressor of tumor dedifferentiation. We surveyed MBNL1 expression in matched tumor/normal pairs across The Cancer Genome Atlas and found that MBNL1 was down-regulated in several common cancers. Down-regulation of MBNL1 predicted poor overall survival in breast, lung, and stomach adenocarcinomas and increased relapse and distant metastasis in triple-negative breast cancer. Down-regulation of MBNL1 led to increased tumorigenic and stem/progenitor-like properties in vitro and in vivo. A discrete set of alternative splicing events (ASEs) are shared between MBNL1-low cancers and embryonic stem cells including a MAP2K7∆exon2 splice variant that leads to increased stem/progenitor-like properties via JNK activation. Accordingly, JNK inhibition is capable of reversing MAP2K7∆exon2-driven tumor dedifferentiation in MBNL1-low cancer cells. Our work elucidates an alternative-splicing mechanism that drives tumor dedifferentiation and identifies biomarkers that predict enhanced susceptibility to JNK inhibition.
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Affiliation(s)
- Debleena Ray
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 165897 Singapore, Singapore;
| | - Yu Chye Yun
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 165897 Singapore, Singapore
| | - Muhammad Idris
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 165897 Singapore, Singapore
| | - Shanshan Cheng
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 165897 Singapore, Singapore
- Centre for Computational Biology, Duke-NUS Medical School, 165897 Singapore, Singapore
| | - Arnoud Boot
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 165897 Singapore, Singapore
- Centre for Computational Biology, Duke-NUS Medical School, 165897 Singapore, Singapore
| | - Tan Bee Huat Iain
- Division of Medical Oncology, National Cancer Centre, 169610 Singapore, Singapore
| | - Steven G Rozen
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 165897 Singapore, Singapore
- Centre for Computational Biology, Duke-NUS Medical School, 165897 Singapore, Singapore
| | - Patrick Tan
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 165897 Singapore, Singapore
| | - David M Epstein
- Cancer and Stem Cell Biology Program, Duke-NUS Medical School, 165897 Singapore, Singapore;
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20
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Stepniak-Konieczna E, Konieczny P, Cywoniuk P, Dluzewska J, Sobczak K. AON-induced splice-switching and DMPK pre-mRNA degradation as potential therapeutic approaches for Myotonic Dystrophy type 1. Nucleic Acids Res 2020; 48:2531-2543. [PMID: 31965181 PMCID: PMC7049696 DOI: 10.1093/nar/gkaa007] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 12/28/2019] [Accepted: 01/03/2020] [Indexed: 01/04/2023] Open
Abstract
Expansion of an unstable CTG repeat in the 3′UTR of the DMPK gene causes Myotonic Dystrophy type 1 (DM1). CUG-expanded DMPK transcripts (CUGexp) sequester Muscleblind-like (MBNL) alternative splicing regulators in ribonuclear inclusions (foci), leading to abnormalities in RNA processing and splicing. To alleviate the burden of CUGexp, we tested therapeutic approach utilizing antisense oligonucleotides (AONs)-mediated DMPK splice-switching and degradation of mutated pre-mRNA. Experimental design involved: (i) skipping of selected constitutive exons to induce frameshifting and decay of toxic mRNAs by an RNA surveillance mechanism, and (ii) exclusion of the alternative exon 15 (e15) carrying CUGexp from DMPK mRNA. While first strategy failed to stimulate DMPK mRNA decay, exclusion of e15 enhanced DMPK nuclear export but triggered accumulation of potentially harmful spliced out pre-mRNA fragment containing CUGexp. Neutralization of this fragment with antisense gapmers complementary to intronic sequences preceding e15 failed to diminish DM1-specific spliceopathy due to AONs’ chemistry-related toxicity. However, intronic gapmers alone reduced the level of DMPK mRNA and mitigated DM1-related cellular phenotypes including spliceopathy and nuclear foci. Thus, a combination of the correct chemistry and experimental approach should be carefully considered to design a safe AON-based therapeutic strategy for DM1.
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Affiliation(s)
- Ewa Stepniak-Konieczna
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 6, 61-614 Poznan, Poland
| | - Patryk Konieczny
- Institute of Human Biology and Evolution, Faculty of Biology, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 6, 61-614 Poznan, Poland
| | - Piotr Cywoniuk
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 6, 61-614 Poznan, Poland
| | - Julia Dluzewska
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 6, 61-614 Poznan, Poland
| | - Krzysztof Sobczak
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznan, Uniwersytetu Poznanskiego 6, 61-614 Poznan, Poland
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21
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Hung CS, Lin JC. Alternatively spliced MBNL1 isoforms exhibit differential influence on enhancing brown adipogenesis. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1863:194437. [PMID: 31730826 DOI: 10.1016/j.bbagrm.2019.194437] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 09/23/2019] [Accepted: 09/25/2019] [Indexed: 01/15/2023]
Abstract
Browning of white adipocytes (WAs) (also referred as beige cells) was demonstrated to execute thermogenesis by consuming stored lipids as do brown adipocytes (BAs), and this is highly related to metabolic homeostasis. Alternative splicing (AS) constitutes a pivotal mechanism for defining cellular fates and functional specifications. Nevertheless, the impacts of AS regulation on the browning of WAs have not been comprehensively investigated. In this study, we first identified the discriminative expression and splicing profiles of the muscleblind-like 1 (MBNL1) gene in postnatal brown adipose tissues (BATs) compared to those of embryonic BATs. A shift in the MBNL1+ex 5 isoform 7 (MBNL17) to MBNL1-ex 5 isoform 1 (MBNL11) was characterized throughout BAT development or during the in vitro browning of pre-WAs, 3T3-L1 cells. The interplay between MBNL1 and the exonic CCUG motif constitutes an autoregulatory mechanism for excluding MBNL1 exon 5. The simultaneous association of RNA-binding motif protein 4a (RBM4a) with exonic and intronic CU elements collaboratively mediates the skipping of MBNL1 exon 5. Overexpressing the MBNL11 isoform exhibited a more-prominent effect than that of the MBNL17 isoform on programming its own transcripts and beige cell-related splicing events in a CCUG motif-mediated manner. In addition to splicing regulation, overexpression of the MBNL11 and MBNL17 isoforms differentially enhanced beige adipogenic signatures of 3T3-L1 cells. Our findings demonstrated that MBNL1 constitutes an emerging and autoregulatory mechanism involved in development of beige cells.
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Affiliation(s)
- Ching-Sheng Hung
- PhD Program in Medicine Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; Department of Laboratory Medicine, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Jung-Chun Lin
- PhD Program in Medicine Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan; School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan.
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22
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Taylor K, Sznajder LJ, Cywoniuk P, Thomas JD, Swanson MS, Sobczak K. MBNL splicing activity depends on RNA binding site structural context. Nucleic Acids Res 2019; 46:9119-9133. [PMID: 29955876 PMCID: PMC6158504 DOI: 10.1093/nar/gky565] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 06/16/2018] [Indexed: 02/02/2023] Open
Abstract
Muscleblind-like (MBNL) proteins are conserved RNA-binding factors involved in alternative splicing (AS) regulation during development. While AS is controlled by distribution of MBNL paralogs and isoforms, the affinity of these proteins for specific RNA-binding regions and their location within transcripts, it is currently unclear how RNA structure impacts MBNL-mediated AS regulation. Here, we defined the RNA structural determinants affecting MBNL-dependent AS activity using both cellular and biochemical assays. While enhanced inclusion of MBNL-regulated alternative exons is controlled by the arrangement and number of MBNL binding sites within unstructured RNA, when these sites are embedded in a RNA hairpin MBNL binds preferentially to one side of stem region. Surprisingly, binding of MBNL proteins to RNA targets did not entirely correlate with AS efficiency. Moreover, comparison of MBNL proteins revealed structure-dependent competitive behavior between the paralogs. Our results showed that the structure of targeted RNAs is a prevalent component of the mechanism of alternative splicing regulation by MBNLs.
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Affiliation(s)
- Katarzyna Taylor
- Laboratory of Gene Therapy, Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Lukasz J Sznajder
- Center for NeuroGenetics and the Genetics Institute, Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, 2033 Mowry Road, Gainesville, FL 32610, USA
| | - Piotr Cywoniuk
- Laboratory of Gene Therapy, Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - James D Thomas
- Center for NeuroGenetics and the Genetics Institute, Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, 2033 Mowry Road, Gainesville, FL 32610, USA.,Computational Biology Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - Maurice S Swanson
- Center for NeuroGenetics and the Genetics Institute, Department of Molecular Genetics and Microbiology, University of Florida College of Medicine, 2033 Mowry Road, Gainesville, FL 32610, USA
| | - Krzysztof Sobczak
- Laboratory of Gene Therapy, Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
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23
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Liu H, Lorenzini PA, Zhang F, Xu S, Wong MSM, Zheng J, Roca X. Alternative splicing analysis in human monocytes and macrophages reveals MBNL1 as major regulator. Nucleic Acids Res 2019; 46:6069-6086. [PMID: 29771377 PMCID: PMC6159523 DOI: 10.1093/nar/gky401] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 05/01/2018] [Indexed: 12/11/2022] Open
Abstract
We report the detailed transcriptomic profiles of human innate myeloid cells using RNA sequencing. Monocytes migrate from blood into infected or wounded tissue to differentiate into macrophages, and control inflammation via phagocytosis or cytokine secretion. We differentiated culture primary monocytes with either GM- or M-CSF to obtain pro- or anti-inflammatory macrophages, and respectively activated them with either LPS/IFNγ or anti-inflammatory cytokines. We also treated the THP-1 monocytic cell line with PMA and similar cytokines to mimic differentiation and activation. We detected thousands of expression and alternative-splicing changes during monocyte-to-macrophage differentiation and activation, and a net increase in exon inclusion. MBNL1 knockdown phenocopies several alternative-splicing changes and strongly impairs PMA differentiation, suggesting functional defects in monocytes from Myotonic Dystrophy patients. This study provides general insights into alternative splicing in the monocyte–macrophage lineage, whose future characterization will elucidate their contribution to immune functions, which are altered in immunodeficiencies, autoimmunity, atherosclerosis and cancer.
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Affiliation(s)
- Hongfei Liu
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
| | - Paolo A Lorenzini
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore.,Nanyang Institute of Technology in Health and Medicine, Interdisciplinary Graduate School (IGS), Nanyang Technological University, 637551 Singapore
| | - Fan Zhang
- School of Computer Science and Engineering, Nanyang Technological University, 637551 Singapore
| | - Shaohai Xu
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
| | - Mei Su M Wong
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
| | - Jie Zheng
- School of Computer Science and Engineering, Nanyang Technological University, 637551 Singapore
| | - Xavier Roca
- School of Biological Sciences, Nanyang Technological University, 637551 Singapore
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24
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Hale MA, Richardson JI, Day RC, McConnell OL, Arboleda J, Wang ET, Berglund JA. An engineered RNA binding protein with improved splicing regulation. Nucleic Acids Res 2019; 46:3152-3168. [PMID: 29309648 PMCID: PMC5888374 DOI: 10.1093/nar/gkx1304] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 12/19/2017] [Indexed: 01/08/2023] Open
Abstract
The muscleblind-like (MBNL) family of proteins are key developmental regulators of alternative splicing. Sequestration of MBNL proteins by expanded CUG/CCUG repeat RNA transcripts is a major pathogenic mechanism in the neuromuscular disorder myotonic dystrophy (DM). MBNL1 contains four zinc finger (ZF) motifs that form two tandem RNA binding domains (ZF1-2 and ZF3-4) which each bind YGCY RNA motifs. In an effort to determine the differences in function between these domains, we designed and characterized synthetic MBNL proteins with duplicate ZF1-2 or ZF3-4 domains, referred to as MBNL-AA and MBNL-BB, respectively. Analysis of splicing regulation revealed that MBNL-AA had up to 5-fold increased splicing activity while MBNL-BB had 4-fold decreased activity compared to a MBNL protein with the canonical arrangement of zinc finger domains. RNA binding analysis revealed that the variations in splicing activity are due to differences in RNA binding specificities between the two ZF domains rather than binding affinity. Our findings indicate that ZF1-2 drives splicing regulation via recognition of YGCY RNA motifs while ZF3-4 acts as a general RNA binding domain. Our studies suggest that synthetic MBNL proteins with improved or altered splicing activity have the potential to be used as both tools for investigating splicing regulation and protein therapeutics for DM and other microsatellite diseases.
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Affiliation(s)
- Melissa A Hale
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA.,Center for NeuroGenetics, University of Florida, Gainesville, FL 32610, USA
| | - Jared I Richardson
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA.,Center for NeuroGenetics, University of Florida, Gainesville, FL 32610, USA
| | - Ryan C Day
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA.,Center for NeuroGenetics, University of Florida, Gainesville, FL 32610, USA
| | - Ona L McConnell
- Center for NeuroGenetics, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - Juan Arboleda
- Center for NeuroGenetics, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - Eric T Wang
- Center for NeuroGenetics, University of Florida, Gainesville, FL 32610, USA.,Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA
| | - J Andrew Berglund
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA.,Center for NeuroGenetics, University of Florida, Gainesville, FL 32610, USA
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25
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Sznajder ŁJ, Swanson MS. Short Tandem Repeat Expansions and RNA-Mediated Pathogenesis in Myotonic Dystrophy. Int J Mol Sci 2019; 20:ijms20133365. [PMID: 31323950 PMCID: PMC6651174 DOI: 10.3390/ijms20133365] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 06/27/2019] [Accepted: 07/08/2019] [Indexed: 12/23/2022] Open
Abstract
Short tandem repeat (STR) or microsatellite, expansions underlie more than 50 hereditary neurological, neuromuscular and other diseases, including myotonic dystrophy types 1 (DM1) and 2 (DM2). Current disease models for DM1 and DM2 propose a common pathomechanism, whereby the transcription of mutant DMPK (DM1) and CNBP (DM2) genes results in the synthesis of CUG and CCUG repeat expansion (CUGexp, CCUGexp) RNAs, respectively. These CUGexp and CCUGexp RNAs are toxic since they promote the assembly of ribonucleoprotein (RNP) complexes or RNA foci, leading to sequestration of Muscleblind-like (MBNL) proteins in the nucleus and global dysregulation of the processing, localization and stability of MBNL target RNAs. STR expansion RNAs also form phase-separated gel-like droplets both in vitro and in transiently transfected cells, implicating RNA-RNA multivalent interactions as drivers of RNA foci formation. Importantly, the nucleation and growth of these nuclear foci and transcript misprocessing are reversible processes and thus amenable to therapeutic intervention. In this review, we provide an overview of potential DM1 and DM2 pathomechanisms, followed by a discussion of MBNL functions in RNA processing and how multivalent interactions between expanded STR RNAs and RNA-binding proteins (RBPs) promote RNA foci assembly.
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Affiliation(s)
- Łukasz J Sznajder
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA.
| | - Maurice S Swanson
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
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26
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Nakagaki-Silva EE, Gooding C, Llorian M, Jacob AG, Richards F, Buckroyd A, Sinha S, Smith CW. Identification of RBPMS as a mammalian smooth muscle master splicing regulator via proximity of its gene with super-enhancers. eLife 2019; 8:46327. [PMID: 31283468 PMCID: PMC6613909 DOI: 10.7554/elife.46327] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Accepted: 06/12/2019] [Indexed: 01/08/2023] Open
Abstract
Alternative splicing (AS) programs are primarily controlled by regulatory RNA-binding proteins (RBPs). It has been proposed that a small number of master splicing regulators might control cell-specific splicing networks and that these RBPs could be identified by proximity of their genes to transcriptional super-enhancers. Using this approach we identified RBPMS as a critical splicing regulator in differentiated vascular smooth muscle cells (SMCs). RBPMS is highly down-regulated during phenotypic switching of SMCs from a contractile to a motile and proliferative phenotype and is responsible for 20% of the AS changes during this transition. RBPMS directly regulates AS of numerous components of the actin cytoskeleton and focal adhesion machineries whose activity is critical for SMC function in both phenotypes. RBPMS also regulates splicing of other splicing, post-transcriptional and transcription regulators including the key SMC transcription factor Myocardin, thereby matching many of the criteria of a master regulator of AS in SMCs.
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Affiliation(s)
| | - Clare Gooding
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Miriam Llorian
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.,Francis Crick Institute, London, United Kingdom
| | - Aishwarya G Jacob
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.,Anne McLaren Laboratory, Cambridge Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom
| | - Frederick Richards
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Adrian Buckroyd
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Sanjay Sinha
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom.,Anne McLaren Laboratory, Cambridge Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom
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27
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Ubiquitination of MBNL1 Is Required for Its Cytoplasmic Localization and Function in Promoting Neurite Outgrowth. Cell Rep 2019; 22:2294-2306. [PMID: 29490267 DOI: 10.1016/j.celrep.2018.02.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 10/19/2017] [Accepted: 02/06/2018] [Indexed: 12/20/2022] Open
Abstract
The Muscleblind-like protein family (MBNL) plays an important role in regulating the transition between differentiation and pluripotency and in the pathogenesis of myotonic dystrophy type 1 (DM1), a CTG expansion disorder. How different MBNL isoforms contribute to the differentiation and are affected in DM1 has not been investigated. Here, we show that the MBNL1 cytoplasmic, but not nuclear, isoform promotes neurite morphogenesis and reverses the morphological defects caused by expanded CUG RNA. Cytoplasmic MBNL1 is polyubiquitinated by lysine 63 (K63). Reduced cytoplasmic MBNL1 in the DM1 mouse brain is consistent with the reduced extent of K63 ubiquitination. Expanded CUG RNA induced the deubiqutination of cytoplasmic MBNL1, which resulted in nuclear translocation and morphological impairment that could be ameliorated by inhibiting K63-linked polyubiquitin chain degradation. Our results suggest that K63-linked ubiquitination of MBNL1 is required for its cytoplasmic localization and that deubiquitination of cytoplasmic MBNL1 is pathogenic in the DM1 brain.
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28
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André LM, van Cruchten RTP, Willemse M, Wansink DG. (CTG)n repeat-mediated dysregulation of MBNL1 and MBNL2 expression during myogenesis in DM1 occurs already at the myoblast stage. PLoS One 2019; 14:e0217317. [PMID: 31116797 PMCID: PMC6530876 DOI: 10.1371/journal.pone.0217317] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 05/08/2019] [Indexed: 11/18/2022] Open
Abstract
Myotonic dystrophy type 1 (DM1) is a severe neuromuscular disorder caused by the expression of trinucleotide repeat-containing DMPK transcripts. Abnormally expanded (CUG)n repeats in these transcripts form hairpin-like structures that cause the RNA to accumulate in the cell nucleus by sequestering isoforms of the Muscleblind (MBNL) family, tissue-specific regulators of developmentally programmed, post-transcriptional processes in RNA metabolism. Through this mechanism, the function of MBNL in RNA processing becomes dominantly perturbed, which eventually leads to aberrant alternative splicing and the expression of foetal splice variants of a wide variety of proteins, including the MBNL isoforms themselves. Here, we employ a patient-derived muscle cell model for DM1 to examine in detail the expression of MBNL RNA and protein variants during myogenic differentiation. This DM1 model consists of a panel of isogenic myoblast cell lines that either contain a pathogenic DMPK allele with a congenital mutation of 2600 triplets, or lack this expanded repeat through CRISPR/Cas9-mediated gene editing. We found that the temporal expression levels of MBNL1, MBNL2 and MBNL3 RNAs are not influenced by presence of the (CTG)2600 repeat during myogenesis in vitro. However, throughout myoblast proliferation and differentiation to myotubes a disproportionate inclusion of MBNL1 exon 5 and MBNL2 exons 5 and 8 occurs in cells with the (CTG)2600 repeat. As a consequence, a reduced quantity and imbalanced collection of splice variants of MBNL1 and MBNL2 accumulates in both the cytoplasm and the nucleus of DM1 myoblasts and myotubes. We thus propose that both the quantitative and qualitative changes in the intracellular partitioning of MBNL proteins are a pivotal cause of skeletal muscle problems in DM1, starting already in muscle progenitor cells.
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Affiliation(s)
- Laurène M. André
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Department of Cell Biology, Nijmegen, The Netherlands
| | - Remco T. P. van Cruchten
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Department of Cell Biology, Nijmegen, The Netherlands
| | - Marieke Willemse
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Department of Cell Biology, Nijmegen, The Netherlands
| | - Derick G. Wansink
- Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Department of Cell Biology, Nijmegen, The Netherlands
- * E-mail:
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29
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Tabaglio T, Low DH, Teo WKL, Goy PA, Cywoniuk P, Wollmann H, Ho J, Tan D, Aw J, Pavesi A, Sobczak K, Wee DKB, Guccione E. MBNL1 alternative splicing isoforms play opposing roles in cancer. Life Sci Alliance 2018; 1:e201800157. [PMID: 30456384 PMCID: PMC6238595 DOI: 10.26508/lsa.201800157] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 08/27/2018] [Accepted: 08/29/2018] [Indexed: 12/20/2022] Open
Abstract
MBNL1 proteins lacking exon 7 (−ex7) are antisurvival factors with tumor suppressive role that cancer cells tend to down-regulate in favor of MBNL +ex7 isoforms. The extent of and the oncogenic role played by alternative splicing (AS) in cancer are well documented. Nonetheless, only few studies have attempted to dissect individual gene function at an isoform level. Here, we focus on the AS of splicing factors during prostate cancer progression, as these factors are known to undergo extensive AS and have the potential to affect hundreds of downstream genes. We identified exon 7 (ex7) in the MBNL1 (Muscleblind-like 1) transcript as being the most differentially included exon in cancer, both in cell lines and in patients' samples. In contrast, MBNL1 overall expression was down-regulated, consistently with its described role as a tumor suppressor. This observation holds true in the majority of cancer types analyzed. We first identified components associated to the U2 splicing complex (SF3B1, SF3A1, and PHF5A) as required for efficient ex7 inclusion and we confirmed that this exon is fundamental for MBNL1 protein homodimerization. We next used splice-switching antisense oligonucleotides (AONs) or siRNAs to compare the effect of MBNL1 splicing isoform switching with knockdown. We report that whereas the absence of MBNL1 is tolerated in cancer cells, the expression of isoforms lacking ex7 (MBNL1 Δex7) induces DNA damage and inhibits cell viability and migration, acting as dominant negative proteins. Our data demonstrate the importance of studying gene function at the level of alternative spliced isoforms and support our conclusion that MBNL1 Δex7 proteins are antisurvival factors with a defined tumor suppressive role that cancer cells tend to down-regulate in favor of MBNL +ex7 isoforms.
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Affiliation(s)
- Tommaso Tabaglio
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore.,Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Diana Hp Low
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore.,Cancer Science Institute, Singapore
| | - Winnie Koon Lay Teo
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore
| | - Pierre Alexis Goy
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore.,Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Piotr Cywoniuk
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Poznan, Poland
| | - Heike Wollmann
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore
| | - Jessica Ho
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore
| | - Damien Tan
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore
| | - Joey Aw
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore
| | - Andrea Pavesi
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore
| | - Krzysztof Sobczak
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Poznan, Poland
| | - Dave Keng Boon Wee
- Institute of High Performance Computing, Agency for Science, Technology and Research, Singapore.,Bioinformatics Institute, Agency for Science, Technology and Research, Singapore
| | - Ernesto Guccione
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore.,Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,Cancer Science Institute, Singapore.,National Cancer Centre Singapore, Singapore.,Department of Oncological Sciences, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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30
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Sellier C, Cerro-Herreros E, Blatter M, Freyermuth F, Gaucherot A, Ruffenach F, Sarkar P, Puymirat J, Udd B, Day JW, Meola G, Bassez G, Fujimura H, Takahashi MP, Schoser B, Furling D, Artero R, Allain FHT, Llamusi B, Charlet-Berguerand N. rbFOX1/MBNL1 competition for CCUG RNA repeats binding contributes to myotonic dystrophy type 1/type 2 differences. Nat Commun 2018; 9:2009. [PMID: 29789616 PMCID: PMC5964235 DOI: 10.1038/s41467-018-04370-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 04/26/2018] [Indexed: 12/30/2022] Open
Abstract
Myotonic dystrophy type 1 and type 2 (DM1, DM2) are caused by expansions of CTG and CCTG repeats, respectively. RNAs containing expanded CUG or CCUG repeats interfere with the metabolism of other RNAs through titration of the Muscleblind-like (MBNL) RNA binding proteins. DM2 follows a more favorable clinical course than DM1, suggesting that specific modifiers may modulate DM severity. Here, we report that the rbFOX1 RNA binding protein binds to expanded CCUG RNA repeats, but not to expanded CUG RNA repeats. Interestingly, rbFOX1 competes with MBNL1 for binding to CCUG expanded repeats and overexpression of rbFOX1 partly releases MBNL1 from sequestration within CCUG RNA foci in DM2 muscle cells. Furthermore, expression of rbFOX1 corrects alternative splicing alterations and rescues muscle atrophy, climbing and flying defects caused by expression of expanded CCUG repeats in a Drosophila model of DM2.
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Affiliation(s)
- Chantal Sellier
- IGBMC, INSERM U964, CNRS UMR7104, University of Strasbourg, 67404, Illkirch, France
| | - Estefanía Cerro-Herreros
- Translational Genomics Group, Interdisciplinary Research Structure for Biotechnology and Biomedicine BIOTECMED, University of Valencia, 46010, Valencia, Spain
- INCLIVA Health Research Institute, 46010, Valencia, Spain
| | - Markus Blatter
- Institute for Molecular Biology and Biophysics, Swiss Federal Institute of Technology (ETH) Zurich, 8092, Zurich, Switzerland
| | - Fernande Freyermuth
- IGBMC, INSERM U964, CNRS UMR7104, University of Strasbourg, 67404, Illkirch, France
| | - Angeline Gaucherot
- IGBMC, INSERM U964, CNRS UMR7104, University of Strasbourg, 67404, Illkirch, France
| | - Frank Ruffenach
- IGBMC, INSERM U964, CNRS UMR7104, University of Strasbourg, 67404, Illkirch, France
| | - Partha Sarkar
- Department of Neurology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Jack Puymirat
- Human Genetics Research Unit, Laval University, CHUQ, Ste-Foy, Quebec, QC G1V 4G2, Canada
| | - Bjarne Udd
- Neuromuscular Research Center, Tampere University Hospital, 33521, Tampere, Finland
- Department of Medical Genetics, Folkhälsan Institute of Genetics, Helsinki University, 00290, Helsinki, Finland
- Department of Neurology, Vasa Central Hospital, 65130, Vaasa, Finland
| | - John W Day
- Department of Neurology, Stanford University, San Francisco, CA, 94305, USA
| | - Giovanni Meola
- Department of Biomedical Sciences for Health, University of Milan, 20097, Milan, Italy
- Neurology Unit, IRCCS Policlinico San Donato, San Donato Milanese, 20097, Milan, Italy
| | - Guillaume Bassez
- Sorbonne Université, Inserm, Association Institut de Myologie, Center of Research in Myology, 75013, Paris, France
| | - Harutoshi Fujimura
- Department of Neurology, Toneyama National Hospital, Toyonaka, 560-0045, Japan
| | - Masanori P Takahashi
- Department of Neurology, Osaka University Graduate School of Medicine, Suita, 565-0871, Japan
| | - Benedikt Schoser
- Friedrich-Baur-Institute, Department of Neurology, Ludwig Maximilian University, 80539, Munich, Germany
| | - Denis Furling
- Sorbonne Université, Inserm, Association Institut de Myologie, Center of Research in Myology, 75013, Paris, France
| | - Ruben Artero
- Translational Genomics Group, Interdisciplinary Research Structure for Biotechnology and Biomedicine BIOTECMED, University of Valencia, 46010, Valencia, Spain
- INCLIVA Health Research Institute, 46010, Valencia, Spain
| | - Frédéric H T Allain
- Institute for Molecular Biology and Biophysics, Swiss Federal Institute of Technology (ETH) Zurich, 8092, Zurich, Switzerland
| | - Beatriz Llamusi
- Translational Genomics Group, Interdisciplinary Research Structure for Biotechnology and Biomedicine BIOTECMED, University of Valencia, 46010, Valencia, Spain.
- INCLIVA Health Research Institute, 46010, Valencia, Spain.
| | - Nicolas Charlet-Berguerand
- IGBMC, INSERM U964, CNRS UMR7104, University of Strasbourg, 67404, Illkirch, France.
- UMR7104, Centre National de la Recherche Scientifique, 67404, Illkirch, France.
- Institut National de la Santé et de la Recherche Médicale, U964, 67404, Illkirch, France.
- Université de Strasbourg, 67404, Illkirch, France.
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31
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Picchio L, Legagneux V, Deschamps S, Renaud Y, Chauveau S, Paillard L, Jagla K. Bruno-3 regulates sarcomere component expression and contributes to muscle phenotypes of myotonic dystrophy type 1. Dis Model Mech 2018; 11:dmm.031849. [PMID: 29716962 PMCID: PMC5992612 DOI: 10.1242/dmm.031849] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 04/18/2018] [Indexed: 01/22/2023] Open
Abstract
Steinert disease, or myotonic dystrophy type 1 (DM1), is a multisystemic disorder caused by toxic noncoding CUG repeat transcripts, leading to altered levels of two RNA binding factors, MBNL1 and CELF1. The contribution of CELF1 to DM1 phenotypes is controversial. Here, we show that the Drosophila CELF1 family member, Bru-3, contributes to pathogenic muscle defects observed in a Drosophila model of DM1. Bru-3 displays predominantly cytoplasmic expression in muscles and its muscle-specific overexpression causes a range of phenotypes also observed in the fly DM1 model, including affected motility, fiber splitting, reduced myofiber length and altered myoblast fusion. Interestingly, comparative genome-wide transcriptomic analyses revealed that Bru-3 negatively regulates levels of mRNAs encoding a set of sarcomere components, including Actn transcripts. Conversely, it acts as a positive regulator of Actn translation. As CELF1 displays predominantly cytoplasmic expression in differentiating C2C12 myotubes and binds to Actn mRNA, we hypothesize that it might exert analogous functions in vertebrate muscles. Altogether, we propose that cytoplasmic Bru-3 contributes to DM1 pathogenesis in a Drosophila model by regulating sarcomeric transcripts and protein levels.
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Affiliation(s)
- Lucie Picchio
- GReD (Genetics, Reproduction and Development Laboratory), INSERM 1103, CNRS 6293, University of Clermont Auvergne, 28 Place Henri Dunant, 63000 Clermont-Ferrand, France
| | - Vincent Legagneux
- IGDR (Institut de Génétique et Développement de Rennes), UMR 6290 CNRS, Université de Rennes, 2 Avenue Léon Bernard, 35000 Rennes, France.,Inserm UMR1085 IRSET, Université de Rennes 1, 35000 Rennes, France.,CNRS-Université de Rennes1-INRIA, UMR6074 IRISA, 35000 Rennes, France
| | - Stephane Deschamps
- IGDR (Institut de Génétique et Développement de Rennes), UMR 6290 CNRS, Université de Rennes, 2 Avenue Léon Bernard, 35000 Rennes, France
| | - Yoan Renaud
- GReD (Genetics, Reproduction and Development Laboratory), INSERM 1103, CNRS 6293, University of Clermont Auvergne, 28 Place Henri Dunant, 63000 Clermont-Ferrand, France
| | - Sabine Chauveau
- GReD (Genetics, Reproduction and Development Laboratory), INSERM 1103, CNRS 6293, University of Clermont Auvergne, 28 Place Henri Dunant, 63000 Clermont-Ferrand, France
| | - Luc Paillard
- IGDR (Institut de Génétique et Développement de Rennes), UMR 6290 CNRS, Université de Rennes, 2 Avenue Léon Bernard, 35000 Rennes, France
| | - Krzysztof Jagla
- GReD (Genetics, Reproduction and Development Laboratory), INSERM 1103, CNRS 6293, University of Clermont Auvergne, 28 Place Henri Dunant, 63000 Clermont-Ferrand, France
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Thomas JD, Oliveira R, Sznajder ŁJ, Swanson MS. Myotonic Dystrophy and Developmental Regulation of RNA Processing. Compr Physiol 2018; 8:509-553. [PMID: 29687899 DOI: 10.1002/cphy.c170002] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Myotonic dystrophy (DM) is a multisystemic disorder caused by microsatellite expansion mutations in two unrelated genes leading to similar, yet distinct, diseases. DM disease presentation is highly variable and distinguished by differences in age-of-onset and symptom severity. In the most severe form, DM presents with congenital onset and profound developmental defects. At the molecular level, DM pathogenesis is characterized by a toxic RNA gain-of-function mechanism that involves the transcription of noncoding microsatellite expansions. These mutant RNAs disrupt key cellular pathways, including RNA processing, localization, and translation. In DM, these toxic RNA effects are predominantly mediated through the modulation of the muscleblind-like and CUGBP and ETR-3-like factor families of RNA binding proteins (RBPs). Dysfunction of these RBPs results in widespread RNA processing defects culminating in the expression of developmentally inappropriate protein isoforms in adult tissues. The tissue that is the focus of this review, skeletal muscle, is particularly sensitive to mutant RNA-responsive perturbations, as patients display a variety of developmental, structural, and functional defects in muscle. Here, we provide a comprehensive overview of DM1 and DM2 clinical presentation and pathology as well as the underlying cellular and molecular defects associated with DM disease onset and progression. Additionally, fundamental aspects of skeletal muscle development altered in DM are highlighted together with ongoing and potential therapeutic avenues to treat this muscular dystrophy. © 2018 American Physiological Society. Compr Physiol 8:509-553, 2018.
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Affiliation(s)
- James D Thomas
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, Florida, USA
| | - Ruan Oliveira
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, Florida, USA
| | - Łukasz J Sznajder
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, Florida, USA
| | - Maurice S Swanson
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, Florida, USA
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Abstract
Muscleblind-like (MBNL) proteins bind to hundreds of pre- and mature mRNAs to regulate their alternative splicing, alternative polyadenylation, stability and subcellular localization. Once MBNLs are withheld from transcript regulation, cellular machineries generate products inapt for precise embryonal/adult developmental tasks and myotonic dystrophy, a devastating multi-systemic genetic disorder, develops. We have recently demonstrated that all three MBNL paralogs are capable of fine-tuning cellular content of one of the three MBNL paralogs, MBNL1, by binding to the first coding exon (e1) of its pre-mRNA. Intriguingly, this autoregulatory feedback loop grounded on alternative splicing of e1 appears to play a crucial role in delaying the onset of myotonic dystrophy. Here, we describe this process in the context of other autoregulatory and regulatory loops that maintain the content and diverse functions of MBNL proteins at optimal level in health and disease, thus supporting the overall cellular homeostasis.
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Affiliation(s)
- Patryk Konieczny
- a Department of Gene Expression , Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University , Poland
| | - Ewa Stepniak-Konieczna
- a Department of Gene Expression , Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University , Poland
| | - Krzysztof Sobczak
- a Department of Gene Expression , Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University , Poland
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Konieczny P, Stepniak-Konieczna E, Taylor K, Sznajder LJ, Sobczak K. Autoregulation of MBNL1 function by exon 1 exclusion from MBNL1 transcript. Nucleic Acids Res 2017; 45:1760-1775. [PMID: 27903900 PMCID: PMC5389549 DOI: 10.1093/nar/gkw1158] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2015] [Accepted: 11/07/2016] [Indexed: 01/14/2023] Open
Abstract
Muscleblind-like proteins (MBNLs) are regulators of RNA metabolism. During tissue differentiation the level of MBNLs increases, while their functional insufficiency plays a crucial role in myotonic dystrophy (DM). Deep sequencing of RNA molecules cross-linked to immunoprecipitated protein particles (CLIP-seq) revealed that MBNL1 binds to MBNL1 exon 1 (e1) encoding both the major part of 5΄UTR and an amino-terminal region of MBNL1 protein. We tested several hypotheses regarding the possible autoregulatory function of MBNL1 binding to its own transcript. Our data indicate that MBNLs induce skipping of e1 from precursor MBNL1 mRNA and that e1 exclusion may impact transcript association with polysomes and translation. Furthermore, e1-deficient protein isoform lacking the first two zinc fingers is highly unstable and its EGFP fusion protein has severely compromised splicing activity. We also show that MBNL1 can be transcribed from three different promoters and that the transcription initiation site determines the mode of e1 regulation. Taken together, we demonstrate that MBNL proteins control steady-state levels of MBNL1 through an interaction with e1 in its precursor mRNA. Insights from our study open a new avenue in therapies against DM based on manipulation of the transcription initiation site and e1 splicing of MBNL1 mRNA.
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Affiliation(s)
- Patryk Konieczny
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Ewa Stepniak-Konieczna
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Katarzyna Taylor
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Lukasz J Sznajder
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Krzysztof Sobczak
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
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Sznajder ŁJ, Michalak M, Taylor K, Cywoniuk P, Kabza M, Wojtkowiak-Szlachcic A, Matłoka M, Konieczny P, Sobczak K. Mechanistic determinants of MBNL activity. Nucleic Acids Res 2016; 44:10326-10342. [PMID: 27733504 PMCID: PMC5137450 DOI: 10.1093/nar/gkw915] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 10/05/2016] [Indexed: 11/13/2022] Open
Abstract
Muscleblind-like (MBNL) proteins are critical RNA processing factors in development. MBNL activity is disrupted in the neuromuscular disease myotonic dystrophy type 1 (DM1), due to the instability of a non-coding microsatellite in the DMPK gene and the expression of CUG expansion (CUGexp) RNAs. Pathogenic interactions between MBNL and CUGexp RNA lead to the formation of nuclear complexes termed foci and prevent MBNL function in pre-mRNA processing. The existence of multiple MBNL genes, as well as multiple protein isoforms, raises the question of whether different MBNL proteins possess unique or redundant functions. To address this question, we coexpressed three MBNL paralogs in cells at equivalent levels and characterized both specific and redundant roles of these proteins in alternative splicing and RNA foci dynamics. When coexpressed in the same cells, MBNL1, MBNL2 and MBNL3 bind the same RNA motifs with different affinities. While MBNL1 demonstrated the highest splicing activity, MBNL3 showed the lowest. When forming RNA foci, MBNL1 is the most mobile paralog, while MBNL3 is rather static and the most densely packed on CUGexp RNA. Therefore, our results demonstrate that MBNL paralogs and gene-specific isoforms possess inherent functional differences, an outcome that could be enlisted to improve therapeutic strategies for DM1.
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Affiliation(s)
- Łukasz J Sznajder
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Michał Michalak
- Department of Molecular and Cellular Biology, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Katarzyna Taylor
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Piotr Cywoniuk
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Michał Kabza
- Department of Bioinformatics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Agnieszka Wojtkowiak-Szlachcic
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Magdalena Matłoka
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Patryk Konieczny
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Krzysztof Sobczak
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
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36
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Dose-Dependent Regulation of Alternative Splicing by MBNL Proteins Reveals Biomarkers for Myotonic Dystrophy. PLoS Genet 2016; 12:e1006316. [PMID: 27681373 PMCID: PMC5082313 DOI: 10.1371/journal.pgen.1006316] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 08/23/2016] [Indexed: 01/23/2023] Open
Abstract
Alternative splicing is a regulated process that results in expression of
specific mRNA and protein isoforms. Alternative splicing factors determine the
relative abundance of each isoform. Here we focus on MBNL1, a splicing factor
misregulated in the disease myotonic dystrophy. By altering the concentration of
MBNL1 in cells across a broad dynamic range, we show that different splicing
events require different amounts of MBNL1 for half-maximal response, and respond
more or less steeply to MBNL1. Motifs around MBNL1 exon 5 were studied to assess
how cis-elements mediate the MBNL1 dose-dependent splicing
response. A framework was developed to estimate MBNL concentration using
splicing responses alone, validated in the cell-based model, and applied to
myotonic dystrophy patient muscle. Using this framework, we evaluated the
ability of individual and combinations of splicing events to predict functional
MBNL concentration in human biopsies, as well as their performance as biomarkers
to assay mild, moderate, and severe cases of DM. Our studies provide insight into the mechanisms of myotonic dystrophy, the most
common adult form of muscular dystrophy. In this disease, a family of RNA
binding proteins is sequestered by toxic RNA, which leads to mis-regulation and
disease symptoms. We have created a cellular model with one of these family
members to study how these RNA binding proteins function in the absence of the
toxic RNA. In parallel, we analyzed transcriptomic data from over 50 individuals
(44 affected by myotonic dystrophy) with a range of disease severity. The
results from the transcriptomic data provide a rational approach to select
biomarkers for clinical research and therapeutic trials.
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Oddo JC, Saxena T, McConnell OL, Berglund JA, Wang ET. Conservation of context-dependent splicing activity in distant Muscleblind homologs. Nucleic Acids Res 2016; 44:8352-62. [PMID: 27557707 PMCID: PMC5041496 DOI: 10.1093/nar/gkw735] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 08/11/2016] [Indexed: 12/15/2022] Open
Abstract
The Muscleblind (MBL) protein family is a deeply conserved family of RNA binding proteins that regulate alternative splicing, alternative polyadenylation, RNA stability and RNA localization. Their inactivation due to sequestration by expanded CUG repeats causes symptoms in the neuromuscular disease myotonic dystrophy. MBL zinc fingers are the most highly conserved portion of these proteins, and directly interact with RNA. We identified putative MBL homologs in Ciona intestinalis and Trichoplax adhaerens, and investigated their ability, as well as that of MBL homologs from human/mouse, fly and worm, to regulate alternative splicing. We found that all homologs can regulate alternative splicing in mouse cells, with some regulating over 100 events. The cis-elements through which each homolog exerts its splicing activities are likely to be highly similar to mammalian Muscleblind-like proteins (MBNLs), as suggested by motif analyses and the ability of expanded CUG repeats to inactivate homolog-mediated splicing. While regulation of specific target exons by MBL/MBNL has not been broadly conserved across these species, genes enriched for MBL/MBNL binding sites in their introns may play roles in cell adhesion, ion transport and axon guidance, among other biological pathways, suggesting a specific, conserved role for these proteins across a broad range of metazoan species.
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Affiliation(s)
- Julia C Oddo
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Tanvi Saxena
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA
| | - Ona L McConnell
- Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA
| | - J Andrew Berglund
- Center for Neurogenetics, University of Florida, Gainesville, FL 32610, USA Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA Department of Chemistry and Biochemistry and Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
| | - Eric T Wang
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32610, USA
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38
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Zhang BW, Cai HF, Wei XF, Sun JJ, Lan XY, Lei CZ, Lin FP, Qi XL, Plath M, Chen H. miR-30-5p Regulates Muscle Differentiation and Alternative Splicing of Muscle-Related Genes by Targeting MBNL. Int J Mol Sci 2016; 17:ijms17020182. [PMID: 26840300 PMCID: PMC4783916 DOI: 10.3390/ijms17020182] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 12/26/2015] [Accepted: 01/22/2016] [Indexed: 02/07/2023] Open
Abstract
MicroRNAs (miRNAs), a class of single stranded, small (~22 nucleotides), non-coding RNAs, play an important role in muscle development. We focused on the role of the miR-30-5p family during bovine muscle development from previous high-throughput sequencing results and analyzed their expression profiles. MHC and MyoG mRNAs expression as well as their proteins were suppressed in differentiated C2C12 cells, suggesting the importance of miR-30-5p in muscle development. MBNL, the candidate target of miR-30-5p, is an alternative splicing regulation factor. MBNL1 and MBNL3 have opposite effects on muscle differentiation. Our results confirmed that miR-30a-5p and miR-30e-5p repress the expression of MBNL1, MBNL2 and MBNL3, whereas miR-30b-5p inhibits MBNL1 and MBNL2 expression. This provides direct evidence that MBNL expression can be flexibly regulated by miR-30-5p. Previous studies showed that MBNL1 promotes exon inclusion of two muscle-related genes (Trim55 and INSR). Through RNA splicing studies, we found that miR-30-5p had an effect on their alternative splicing, which means miR-30-5p via MBNL1 could be integrated into muscle signaling pathways in which INSR or Trim55 are located. In conclusion, miR-30-5p could inhibit muscle cell differentiation and regulate the alternative splicing of Trim55 and INSR by targeting MBNL. These results promote the understanding of the function of miRNAs in muscle development.
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Affiliation(s)
- Bo-Wen Zhang
- Shaanxi Key Laboratory of Agricultural Molecular Biology, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Han-Fang Cai
- Shaanxi Key Laboratory of Agricultural Molecular Biology, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Xue-Feng Wei
- Shaanxi Key Laboratory of Agricultural Molecular Biology, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Jia-Jie Sun
- Shaanxi Key Laboratory of Agricultural Molecular Biology, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Xian-Yong Lan
- Shaanxi Key Laboratory of Agricultural Molecular Biology, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Chu-Zhao Lei
- Shaanxi Key Laboratory of Agricultural Molecular Biology, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Feng-Peng Lin
- Department of Animal Husbandry, Bureau of Biyang County of Henan province, Biyang 463700, Henan, China.
| | - Xing-Lei Qi
- Department of Animal Husbandry, Bureau of Biyang County of Henan province, Biyang 463700, Henan, China.
| | - Martin Plath
- Shaanxi Key Laboratory of Agricultural Molecular Biology, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
| | - Hong Chen
- Shaanxi Key Laboratory of Agricultural Molecular Biology, College of Animal Science and Technology, Northwest A&F University, Yangling 712100, Shaanxi, China.
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39
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Urbanek MO, Krzyzosiak WJ. RNA FISH for detecting expanded repeats in human diseases. Methods 2015; 98:115-123. [PMID: 26615955 DOI: 10.1016/j.ymeth.2015.11.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 11/18/2015] [Accepted: 11/21/2015] [Indexed: 12/14/2022] Open
Abstract
RNA fluorescence in situ hybridization (FISH) is a widely used technique for detecting transcripts in fixed cells and tissues. Many variants of RNA FISH have been proposed to increase signal strength, resolution and target specificity. The current variants of this technique facilitate the detection of the subcellular localization of transcripts at a single molecule level. Among the applications of RNA FISH are studies on nuclear RNA foci in diseases resulting from the expansion of tri-, tetra-, penta- and hexanucleotide repeats present in different single genes. The partial or complete retention of mutant transcripts forming RNA aggregates within the nucleoplasm has been shown in multiple cellular disease models and in the tissues of patients affected with these atypical mutations. Relevant diseases include, among others, myotonic dystrophy type 1 (DM1) with CUG repeats, Huntington's disease (HD) and spinocerebellar ataxia type 3 (SCA3) with CAG repeats, fragile X-associated tremor/ataxia syndrome (FXTAS) with CGG repeats, myotonic dystrophy type 2 (DM2) with CCUG repeats, amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) with GGGGCC repeats and spinocerebellar ataxia type 32 (SCA32) with GGCCUG. In this article, we summarize the results obtained with FISH to examine RNA nuclear inclusions. We provide a detailed protocol for detecting RNAs containing expanded CAG and CUG repeats in different cellular models, including fibroblasts, lymphoblasts, induced pluripotent stem cells and murine and human neuronal progenitors. We also present the results of the first single-molecule FISH application in a cellular model of polyglutamine disease.
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Affiliation(s)
- Martyna O Urbanek
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14 Str., 61-704 Poznan, Poland
| | - Wlodzimierz J Krzyzosiak
- Department of Molecular Biomedicine, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14 Str., 61-704 Poznan, Poland.
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40
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Pettersson OJ, Aagaard L, Jensen TG, Damgaard CK. Molecular mechanisms in DM1 - a focus on foci. Nucleic Acids Res 2015; 43:2433-41. [PMID: 25605794 PMCID: PMC4344492 DOI: 10.1093/nar/gkv029] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 01/05/2015] [Accepted: 01/11/2015] [Indexed: 01/15/2023] Open
Abstract
Myotonic dystrophy type 1 is caused by abnormal expansion of a CTG-trinucleotide repeat in the gene encoding Dystrophia Myotonica Protein Kinase (DMPK), which in turn leads to global deregulation of gene expression in affected individuals. The transcribed mRNA contains a massive CUG-expansion in the 3' untranslated region (3'UTR) facilitating nucleation of several regulatory RNA-binding proteins, which are thus unable to perform their normal cellular function. These CUG-expanded mRNA-protein aggregates form distinct, primarily nuclear foci. In differentiated muscle cells, most of the CUG-expanded RNA remains in the nuclear compartment, while in dividing cells such as fibroblasts a considerable fraction of the mutant RNA reaches the cytoplasm, consistent with findings that both nuclear and cytoplasmic events are mis-regulated in DM1. Recent evidence suggests that the nuclear aggregates, or ribonuclear foci, are more dynamic than previously anticipated and regulated by several proteins, including RNA helicases. In this review, we focus on the homeostasis of DMPK mRNA foci and discuss how their dynamic regulation may affect disease-causing mechanisms in DM1.
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Affiliation(s)
- Olof Joakim Pettersson
- Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 4, Building 1240, DK-8000 Aarhus C, Denmark
| | - Lars Aagaard
- Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 4, Building 1240, DK-8000 Aarhus C, Denmark
| | - Thomas Gryesten Jensen
- Department of Biomedicine, Aarhus University, Wilhelm Meyers Allé 4, Building 1240, DK-8000 Aarhus C, Denmark
| | - Christian Kroun Damgaard
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, Building 1130, DK-8000 Aarhus C, Denmark
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41
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Yu Z, Goodman LD, Shieh SY, Min M, Teng X, Zhu Y, Bonini NM. A fly model for the CCUG-repeat expansion of myotonic dystrophy type 2 reveals a novel interaction with MBNL1. Hum Mol Genet 2014; 24:954-62. [PMID: 25305073 DOI: 10.1093/hmg/ddu507] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Expanded non-coding RNA repeats of CUG and CCUG are the underlying genetic causes for myotonic dystrophy type 1 (DM1) and type 2 (DM2), respectively. A gain-of-function of these pathogenic repeat expansions is mediated at least in part by their abnormal interactions with RNA-binding proteins such as MBNL1 and resultant loss of activity of these proteins. To study pathogenic mechanisms of CCUG-repeat expansions in an animal model, we created a fly model of DM2 that expresses pure, uninterrupted CCUG-repeat expansions ranging from 16 to 720 repeats in length. We show that this fly model for DM2 recapitulates key features of human DM2 including RNA repeat-induced toxicity, ribonuclear foci formation and changes in alternative splicing. Interestingly, expression of two isoforms of MBNL1, MBNL135 and MBNL140, leads to cleavage and concurrent upregulation of the levels of the RNA-repeat transcripts, with MBNL140 having more significant effects than MBNL135. This property is shared with a fly CUG-repeat expansion model. Our results suggest a novel mechanism for interaction between the pathogenic RNA repeat expansions of myotonic dystrophy and MBNL1.
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Affiliation(s)
| | - Lindsey D Goodman
- Neurosciences Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | | | | | | | - Nancy M Bonini
- Department of Biology and Neurosciences Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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42
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Kino Y, Washizu C, Kurosawa M, Oma Y, Hattori N, Ishiura S, Nukina N. Nuclear localization of MBNL1: splicing-mediated autoregulation and repression of repeat-derived aberrant proteins. Hum Mol Genet 2014; 24:740-56. [PMID: 25274774 DOI: 10.1093/hmg/ddu492] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In some neurological diseases caused by repeat expansions such as myotonic dystrophy, the RNA-binding protein muscleblind-like 1 (MBNL1) accumulates in intranuclear inclusions containing mutant repeat RNA. The interaction between MBNL1 and mutant RNA in the nucleus is a key event leading to loss of MBNL function, yet the details of this effect have been elusive. Here, we investigated the mechanism and significance of MBNL1 nuclear localization. We found that MBNL1 contains two classes of nuclear localization signal (NLS), a classical bipartite NLS and a novel conformational NLS. Alternative splicing of exon 7 acts as a switch between these NLS types and couples MBNL1 activity and intracellular localization. Depending on its nuclear localization, MBNL1 promoted nuclear accumulation of mutant RNA containing a CUG or CAG repeat, some of which produced proteins containing homopolymeric tracts such as polyglutamine. Furthermore, MBNL1 repressed the expression of these homopolymeric proteins including those presumably produced through repeat-associated non-ATG (RAN) translation. These results suggest that nuclear retention of expanded RNA reflects a novel role of MBNL proteins in repressing aberrant protein expression and may provide pathological and therapeutic implications for a wide range of repeat expansion diseases associated with nuclear RNA retention and/or RAN translation.
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Affiliation(s)
- Yoshihiro Kino
- Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo 113-0033, Japan CREST (Core Research for Evolutionary Science and Technology), JST, Saitama 332-0012, Japan Laboratory for Structural Neuropathology, Brain Science Institute, RIKEN, Saitama 351-0198, Japan Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, Tokyo 204-8588, Japan and
| | - Chika Washizu
- Laboratory for Structural Neuropathology, Brain Science Institute, RIKEN, Saitama 351-0198, Japan
| | - Masaru Kurosawa
- Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo 113-0033, Japan CREST (Core Research for Evolutionary Science and Technology), JST, Saitama 332-0012, Japan Laboratory for Structural Neuropathology, Brain Science Institute, RIKEN, Saitama 351-0198, Japan
| | - Yoko Oma
- Department of Life Sciences, Graduate School of Arts and Sciences, the University of Tokyo, Tokyo 153-8902, Japan
| | - Nobutaka Hattori
- Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo 113-0033, Japan
| | - Shoichi Ishiura
- Department of Life Sciences, Graduate School of Arts and Sciences, the University of Tokyo, Tokyo 153-8902, Japan
| | - Nobuyuki Nukina
- Department of Neuroscience for Neurodegenerative Disorders, Juntendo University Graduate School of Medicine, Tokyo 113-0033, Japan CREST (Core Research for Evolutionary Science and Technology), JST, Saitama 332-0012, Japan Laboratory for Structural Neuropathology, Brain Science Institute, RIKEN, Saitama 351-0198, Japan
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43
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Konieczny P, Stepniak-Konieczna E, Sobczak K. MBNL proteins and their target RNAs, interaction and splicing regulation. Nucleic Acids Res 2014; 42:10873-87. [PMID: 25183524 PMCID: PMC4176163 DOI: 10.1093/nar/gku767] [Citation(s) in RCA: 126] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Muscleblind-like (MBNL) proteins are key regulators of precursor and mature mRNA metabolism in mammals. Based on published and novel data, we explore models of tissue-specific MBNL interaction with RNA. We portray MBNL domains critical for RNA binding and splicing regulation, and the structure of MBNL's normal and pathogenic RNA targets, particularly in the context of myotonic dystrophy (DM), in which expanded CUG or CCUG repeat transcripts sequester several nuclear proteins including MBNLs. We also review the properties of MBNL/RNA complex, including recent data obtained from UV cross-linking and immunoprecipitation (CLIP-Seq), and discuss how this interaction shapes normal MBNL-dependent alternative splicing regulation. Finally, we review how this acquired knowledge about the pathogenic RNA structure and nature of MBNL sequestration can be translated into the design of therapeutic strategies against DM.
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Affiliation(s)
- Patryk Konieczny
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Ewa Stepniak-Konieczna
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
| | - Krzysztof Sobczak
- Department of Gene Expression, Institute of Molecular Biology and Biotechnology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland
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Rehman S, Gladman JT, Periasamy A, Sun Y, Mahadevan MS. Development of an AP-FRET based analysis for characterizing RNA-protein interactions in myotonic dystrophy (DM1). PLoS One 2014; 9:e95957. [PMID: 24781112 PMCID: PMC4004549 DOI: 10.1371/journal.pone.0095957] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 03/31/2014] [Indexed: 01/09/2023] Open
Abstract
Förster Resonance Energy Transfer (FRET) microscopy is a powerful tool used to identify molecular interactions in live or fixed cells using a non-radiative transfer of energy from a donor fluorophore in the excited state to an acceptor fluorophore in close proximity. FRET can be a very sensitive tool to study protein-protein and/or protein-nucleic acids interactions. RNA toxicity is implicated in a number of disorders; especially those associated with expanded repeat sequences, such as myotonic dystrophy. Myotonic dystrophy (DM1) is caused by a (CTG)n repeat expansion in the 3′ UTR of the DMPK gene which results in nuclear retention of mutant DMPK transcripts in RNA foci. This results in toxic gain-of-function effects mediated through altered functions of RNA-binding proteins (e.g. MBNL1, hnRNPH, CUGBP1). In this study we demonstrate the potential of a new acceptor photobleaching assay to measure FRET (AP-FRET) between RNA and protein. We chose to focus on the interaction between MBNL1 and mutant DMPK mRNA in cells from DM1 patients due to the strong microscopic evidence of their co-localization. Using this technique we have direct evidence of intracellular interaction between MBNL1 and the DMPK RNA. Furthermore using the AP-FRET assay and MBNL1 mutants, we show that all four zinc-finger motifs in MBNL1 are crucial for MBNL1-RNA foci interactions. The data derived using this new assay provides compelling evidence for the interaction between RNA binding proteins and RNA foci, and mechanistic insights into MBNL1-RNA foci interaction demonstrating the power of AP-FRET in examining RNA-Protein interactions in DM1.
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Affiliation(s)
- Shagufta Rehman
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Jordan T Gladman
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Ammasi Periasamy
- Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Yuansheng Sun
- Department of Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Mani S Mahadevan
- Department of Pathology, University of Virginia, Charlottesville, Virginia, United States of America
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Mohan A, Goodwin M, Swanson MS. RNA-protein interactions in unstable microsatellite diseases. Brain Res 2014; 1584:3-14. [PMID: 24709120 DOI: 10.1016/j.brainres.2014.03.039] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 03/25/2014] [Accepted: 03/26/2014] [Indexed: 12/14/2022]
Abstract
A novel RNA-mediated disease mechanism has emerged from studies on dominantly inherited neurological disorders caused by unstable microsatellite expansions in non-coding regions of the genome. These non-coding tandem repeat expansions trigger the production of unusual RNAs that gain a toxic function, which involves the formation of RNA repeat structures that interact with, and alter the activities of, various factors required for normal RNA processing as well as additional cellular functions. In this review, we explore the deleterious effects of toxic RNA expression and discuss the various model systems currently available for studying RNA gain-of-function in neurologic diseases. Common themes, including bidirectional transcription and repeat-associated non-ATG (RAN) translation, have recently emerged from expansion disease studies. These and other discoveries have highlighted the need for further investigations designed to provide the additional mechanistic insights essential for future therapeutic development.
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Affiliation(s)
- Apoorva Mohan
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Cancer Genetics Research Complex, 2033 Mowry Road, Gainesville, FL 32610-3610, USA
| | - Marianne Goodwin
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Cancer Genetics Research Complex, 2033 Mowry Road, Gainesville, FL 32610-3610, USA
| | - Maurice S Swanson
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Cancer Genetics Research Complex, 2033 Mowry Road, Gainesville, FL 32610-3610, USA.
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Carpentier C, Ghanem D, Fernandez-Gomez FJ, Jumeau F, Philippe JV, Freyermuth F, Labudeck A, Eddarkaoui S, Dhaenens CM, Holt I, Behm-Ansmant I, Marmier-Gourrier N, Branlant C, Charlet-Berguerand N, Marie J, Schraen-Maschke S, Buée L, Sergeant N, Caillet-Boudin ML. Tau exon 2 responsive elements deregulated in myotonic dystrophy type I are proximal to exon 2 and synergistically regulated by MBNL1 and MBNL2. Biochim Biophys Acta Mol Basis Dis 2014; 1842:654-64. [PMID: 24440524 DOI: 10.1016/j.bbadis.2014.01.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 12/09/2013] [Accepted: 01/07/2014] [Indexed: 01/21/2023]
Abstract
The splicing of the microtubule-associated protein Tau is regulated during development and is found to be deregulated in a growing number of pathological conditions such as myotonic dystrophy type I (DM1), in which a reduced number of isoforms is expressed in the adult brain. DM1 is caused by a dynamic and unstable CTG repeat expansion in the DMPK gene, resulting in an RNA bearing long CUG repeats (n>50) that accumulates in nuclear foci and sequesters CUG-binding splicing factors of the muscle blind-like (MBNL) family, involved in the splicing of Tau pre-mRNA among others. However, the precise mechanism leading to Tau mis-splicing and the role of MBNL splicing factors in this process are poorly understood. We therefore used new Tau minigenes that we developed for this purpose to determine how MBNL1 and MBNL2 interact to regulate Tau exon 2 splicing. We demonstrate that an intronic region 250 nucleotides downstream of Tau exon 2 contains cis-regulatory splicing enhancers that are sensitive to MBNL and that bind directly to MBNL1. Both MBNL1 and MBNL2 act as enhancers of Tau exon 2 inclusion. Intriguingly, the interaction of MBNL1 and MBNL2 is required to fully reverse the mis-splicing of Tau exon 2 induced by the trans-dominant effect of long CUG repeats, similar to the DM1 condition. In conclusion, both MBNL1 and MBNL2 are involved in the regulation of Tau exon 2 splicing and the mis-splicing of Tau in DM1 is due to the combined inactivation of both.
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Affiliation(s)
- C Carpentier
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - D Ghanem
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - F J Fernandez-Gomez
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - F Jumeau
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - J V Philippe
- Laboratory of Molecular Engineering and Articular Pathophysiology (IMoPA), Nancy University - CNRS, UMR 7214, 7365 Vandoeuvre-les-Nancy, France
| | - F Freyermuth
- Department de Neurobiology & Genetics, IGBMC, Inserm U964, CNRS UMR7104, University of Strasbourg, Illkirch, France
| | - A Labudeck
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - S Eddarkaoui
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - C M Dhaenens
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - I Holt
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry, Shropshire, UK; Institute for Science and Technology in Medicine, Keele University, Keele, Staffordshire, UK
| | - I Behm-Ansmant
- Laboratory of Molecular Engineering and Articular Pathophysiology (IMoPA), Nancy University - CNRS, UMR 7214, 7365 Vandoeuvre-les-Nancy, France
| | - N Marmier-Gourrier
- Laboratory of Molecular Engineering and Articular Pathophysiology (IMoPA), Nancy University - CNRS, UMR 7214, 7365 Vandoeuvre-les-Nancy, France
| | - C Branlant
- Laboratory of Molecular Engineering and Articular Pathophysiology (IMoPA), Nancy University - CNRS, UMR 7214, 7365 Vandoeuvre-les-Nancy, France
| | - N Charlet-Berguerand
- Department de Neurobiology & Genetics, IGBMC, Inserm U964, CNRS UMR7104, University of Strasbourg, Illkirch, France
| | - J Marie
- Therapy of muscular diseases - Myology Institute, UPMC Univ. Paris 6, UM76/Inserm, U974/CNRS, UMR 7215, G.H. Pitié-Salpétrière - Bâtiment Babinski, Paris, France
| | - S Schraen-Maschke
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - L Buée
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France
| | - N Sergeant
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France.
| | - M L Caillet-Boudin
- Inserm UMR837-1 and Univ. Lille Nord de France, Jean-Pierre Aubert Research Center, Alzheimer & Tauopathies, F-59045 Lille, France; Regional University Hospital of Lille, France.
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Caillet-Boudin ML, Fernandez-Gomez FJ, Tran H, Dhaenens CM, Buee L, Sergeant N. Brain pathology in myotonic dystrophy: when tauopathy meets spliceopathy and RNAopathy. Front Mol Neurosci 2014; 6:57. [PMID: 24409116 PMCID: PMC3885824 DOI: 10.3389/fnmol.2013.00057] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 12/20/2013] [Indexed: 01/18/2023] Open
Abstract
Myotonic dystrophy (DM) of type 1 and 2 (DM1 and DM2) are inherited autosomal dominant diseases caused by dynamic and unstable expanded microsatellite sequences (CTG and CCTG, respectively) in the non-coding regions of the genes DMPK and ZNF9, respectively. These mutations result in the intranuclear accumulation of mutated transcripts and the mis-splicing of numerous transcripts. This so-called RNA gain of toxic function is the main feature of an emerging group of pathologies known as RNAopathies. Interestingly, in addition to these RNA inclusions, called foci, the presence of neurofibrillary tangles (NFT) in patient brains also distinguishes DM as a tauopathy. Tauopathies are a group of nearly 30 neurodegenerative diseases that are characterized by intraneuronal protein aggregates of the microtubule-associated protein Tau (MAPT) in patient brains. Furthermore, a number of neurodegenerative diseases involve the dysregulation of splicing regulating factors and have been characterized as spliceopathies. Thus, myotonic dystrophies are pathologies resulting from the interplay among RNAopathy, spliceopathy, and tauopathy. This review will describe how these processes contribute to neurodegeneration. We will first focus on the tauopathy associated with DM1, including clinical symptoms, brain histology, and molecular mechanisms. We will also discuss the features of DM1 that are shared by other tauopathies and, consequently, might participate in the development of a tauopathy. Moreover, we will discuss the determinants common to both RNAopathies and spliceopathies that could interfere with tau-related neurodegeneration.
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Affiliation(s)
- Marie-Laure Caillet-Boudin
- Alzheimer and Tauopathies, Faculty of Medicine, Jean-Pierre Aubert Research Centre, Institute of Predictive Medicine and Therapeutic Research, Inserm, UMR 837 Lille, France ; University of Lille Nord de France, UDSL Lille, France
| | - Francisco-Jose Fernandez-Gomez
- Alzheimer and Tauopathies, Faculty of Medicine, Jean-Pierre Aubert Research Centre, Institute of Predictive Medicine and Therapeutic Research, Inserm, UMR 837 Lille, France ; University of Lille Nord de France, UDSL Lille, France
| | - Hélène Tran
- Alzheimer and Tauopathies, Faculty of Medicine, Jean-Pierre Aubert Research Centre, Institute of Predictive Medicine and Therapeutic Research, Inserm, UMR 837 Lille, France ; University of Lille Nord de France, UDSL Lille, France
| | - Claire-Marie Dhaenens
- Alzheimer and Tauopathies, Faculty of Medicine, Jean-Pierre Aubert Research Centre, Institute of Predictive Medicine and Therapeutic Research, Inserm, UMR 837 Lille, France ; University of Lille Nord de France, UDSL Lille, France
| | - Luc Buee
- Alzheimer and Tauopathies, Faculty of Medicine, Jean-Pierre Aubert Research Centre, Institute of Predictive Medicine and Therapeutic Research, Inserm, UMR 837 Lille, France ; University of Lille Nord de France, UDSL Lille, France
| | - Nicolas Sergeant
- Alzheimer and Tauopathies, Faculty of Medicine, Jean-Pierre Aubert Research Centre, Institute of Predictive Medicine and Therapeutic Research, Inserm, UMR 837 Lille, France ; University of Lille Nord de France, UDSL Lille, France
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Giudice J, Cooper TA. RNA-binding proteins in heart development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 825:389-429. [PMID: 25201112 DOI: 10.1007/978-1-4939-1221-6_11] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
RNA-binding proteins (RBPs) are key players of posttranscriptional regulation occurring during normal tissue development. All tissues examined thus far have revealed the importance of RBPs in the regulation of complex networks involved in organ morphogenesis, maturation, and function. They are responsible for controlling tissue-specific gene expression by regulating alternative splicing, mRNA stability, translation, and poly-adenylation. The heart is the first organ form during embryonic development and is also the first to acquire functionality. Numerous remodeling processes take place during late cardiac development since fetal heart first adapts to birth and then undergoes a transition to adult functionality. This physiological remodeling involves transcriptional and posttranscriptional networks that are regulated by RBPs. Disruption of the normal regulatory networks has been shown to cause cardiomyopathy in humans and animal models. Here we review the complexity of late heart development and the current information regarding how RBPs control aspects of postnatal heart development. We also review how activities of RBPs are modulated adding complexity to the regulation of developmental networks.
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Affiliation(s)
- Jimena Giudice
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, 77030, USA,
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49
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Edge C, Gooding C, Smith CWJ. Dissecting domains necessary for activation and repression of splicing by Muscleblind-like protein 1. BMC Mol Biol 2013; 14:29. [PMID: 24373687 PMCID: PMC3880588 DOI: 10.1186/1471-2199-14-29] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 12/16/2013] [Indexed: 01/06/2023] Open
Abstract
Background Alternative splicing contributes to the diversity of the proteome, and provides the cell with an important additional layer of regulation of gene expression. Among the many RNA binding proteins that regulate alternative splicing pathways are the Muscleblind-like (MBNL) proteins. MBNL proteins bind YGCY motifs in RNA via four CCCH zinc fingers arranged in two tandem arrays, and play a crucial role in the transition from embryonic to adult muscle splicing patterns, deregulation of which leads to Myotonic Dystrophy. Like many other RNA binding proteins, MBNL proteins can act as both activators or repressors of different splicing events. Results We used targeted point mutations to interfere with the RNA binding of MBNL1 zinc fingers individually and in combination. The effects of the mutations were tested in assays for splicing repression and activation, including overexpression, complementation of siRNA-mediated knockdown, and artificial tethering using MS2 coat protein. Mutations were tested in the context of both full length MBNL1 as well as a series of truncation mutants. Individual mutations within full length MBNL1 had little effect, but mutations in ZF1 and 2 combined were more detrimental than those in ZF 3 and 4, upon splicing activation, repression and RNA binding. Activation and repression both required linker sequences between ZF2 and 3, but activation was more sensitive to loss of linker sequences. Conclusions Our results highlight the importance of RNA binding by MBNL ZF domains 1 and 2 for splicing regulatory activity, even when the protein is artificially recruited to its regulatory location on target RNAs. However, RNA binding is not sufficient for activity; additional regions between ZF 2 and 3 are also essential. Activation and repression show differential sensitivity to truncation of this linker region, suggesting interactions with different sets of cofactors for the two types of activity.
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Affiliation(s)
| | | | - Christopher W J Smith
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK.
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MBNL142 and MBNL143 gene isoforms, overexpressed in DM1-patient muscle, encode for nuclear proteins interacting with Src family kinases. Cell Death Dis 2013; 4:e770. [PMID: 23949219 PMCID: PMC3763452 DOI: 10.1038/cddis.2013.291] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 05/19/2013] [Accepted: 05/23/2013] [Indexed: 12/20/2022]
Abstract
Myotonic dystrophy type-1 (DM1) is the most prevalent form of muscular dystrophy in adults. This disorder is an RNA-dominant disease, caused by expansion of a CTG repeat in the DMPK gene that leads to a misregulation in the alternative splicing of pre-mRNAs. The longer muscleblind-like-1 (MBNL1) transcripts containing exon 5 and the respective protein isoforms (MBNL142-43) were found to be overexpressed in DM1 muscle and localized exclusively in the nuclei. In vitro assays showed that MBNL142-43 bind the Src-homology 3 domain of Src family kinases (SFKs) via their proline-rich motifs, enhancing the SFK activity. Notably, this association was also confirmed in DM1 muscle and myotubes. The recovery, mediated by an siRNA target to Ex5-MBNL142-43, succeeded in reducing the nuclear localization of both Lyn and MBNL142-43 proteins and in decreasing the level of tyrosine phosphorylated proteins. Our results suggest an additional molecular mechanism in the DM1 pathogenesis, based on an altered phosphotyrosine signalling pathway.
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