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de Pontual L, Tomé S. Overview of the Complex Relationship between Epigenetics Markers, CTG Repeat Instability and Symptoms in Myotonic Dystrophy Type 1. Int J Mol Sci 2022; 23:ijms23073477. [PMID: 35408837 PMCID: PMC8998570 DOI: 10.3390/ijms23073477] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 03/14/2022] [Accepted: 03/16/2022] [Indexed: 02/05/2023] Open
Abstract
Among the trinucleotide repeat disorders, myotonic dystrophy type 1 (DM1) is one of the most complex neuromuscular diseases caused by an unstable CTG repeat expansion in the DMPK gene. DM1 patients exhibit high variability in the dynamics of CTG repeat instability and in the manifestations and progression of the disease. The largest expanded alleles are generally associated with the earliest and most severe clinical form. However, CTG repeat length alone is not sufficient to predict disease severity and progression, suggesting the involvement of other factors. Several data support the role of epigenetic alterations in clinical and genetic variability. By highlighting epigenetic alterations in DM1, this review provides a new avenue on how these changes can serve as biomarkers to predict clinical features and the mutation behavior.
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Affiliation(s)
| | - Stéphanie Tomé
- Correspondence: ; Tel.: +33-1-42-16-57-16; Fax: +33-1-42-16-57-00
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2
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Impact of Genetic Testing on Human Health:. Dela J Public Health 2021; 7:10-11. [PMID: 35619978 PMCID: PMC9124557 DOI: 10.32481/djph.2021.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Advances in the field of human genetics over the past three decades have led to improvements in human health through development and availability of novel genetic testing approaches for diagnosis, prognosis, treatment therapy, safety, preventive screening and population-based risk assessment. In this commentary, I highlight the current landscape of genetic testing in Delaware with a focus on the genetic etiology and molecular diagnosis of pediatric disease, tailored treatment efficacy and safety through novel clinical trials and pharmacogenomics, and training in the application of genomic approaches to rare and common diseases. Future opportunities include integrating application of genetic information into clinical practice, improving genetics education, focusing on disparities and access, and advancing genomics and digital health technologies.
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Timchenko L. Correction of RNA-Binding Protein CUGBP1 and GSK3β Signaling as Therapeutic Approach for Congenital and Adult Myotonic Dystrophy Type 1. Int J Mol Sci 2019; 21:ijms21010094. [PMID: 31877772 PMCID: PMC6982105 DOI: 10.3390/ijms21010094] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 12/13/2019] [Accepted: 12/17/2019] [Indexed: 01/02/2023] Open
Abstract
Myotonic dystrophy type 1 (DM1) is a complex genetic disease affecting many tissues. DM1 is caused by an expansion of CTG repeats in the 3′-UTR of the DMPK gene. The mechanistic studies of DM1 suggested that DMPK mRNA, containing expanded CUG repeats, is a major therapeutic target in DM1. Therefore, the removal of the toxic RNA became a primary focus of the therapeutic development in DM1 during the last decade. However, a cure for this devastating disease has not been found. Whereas the degradation of toxic RNA remains a preferential approach for the reduction of DM1 pathology, other approaches targeting early toxic events downstream of the mutant RNA could be also considered. In this review, we discuss the beneficial role of the restoring of the RNA-binding protein, CUGBP1/CELF1, in the correction of DM1 pathology. It has been recently found that the normalization of CUGBP1 activity with the inhibitors of GSK3 has a positive effect on the reduction of skeletal muscle and CNS pathologies in DM1 mouse models. Surprisingly, the inhibitor of GSK3, tideglusib also reduced the toxic CUG-containing RNA. Thus, the development of the therapeutics, based on the correction of the GSK3β-CUGBP1 pathway, is a promising option for this complex disease.
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Affiliation(s)
- Lubov Timchenko
- Departments of Neurology and Pediatrics, Cincinnati Children's Hospital Medical Center and the University of Cincinnati, Cincinnati, OH 45229, USA
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4
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Matloka M, Klein AF, Rau F, Furling D. Cells of Matter- In Vitro Models for Myotonic Dystrophy. Front Neurol 2018; 9:361. [PMID: 29875732 PMCID: PMC5974047 DOI: 10.3389/fneur.2018.00361] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 05/03/2018] [Indexed: 12/17/2022] Open
Abstract
Myotonic dystrophy type 1 (DM1 also known as Steinert disease) is a multisystemic disorder mainly characterized by myotonia, progressive muscle weakness and wasting, cognitive impairments, and cardiac defects. This autosomal dominant disease is caused by the expression of nuclear retained RNAs containing pathologic expanded CUG repeats that alter the function of RNA-binding proteins in a tissue-specific manner, leading ultimately to neuromuscular dysfunction and clinical symptoms. Although considerable knowledge has been gathered on myotonic dystrophy since its first description, the development of novel relevant disease models remains of high importance to investigate pathophysiologic mechanisms and to assess new therapeutic approaches. In addition to animal models, in vitro cell cultures provide a unique resource for both fundamental and translational research. This review discusses how cellular models broke ground to decipher molecular basis of DM1 and describes currently available cell models, ranging from exogenous expression of the CTG tracts to variable patients' derived cells.
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Affiliation(s)
| | | | | | - Denis Furling
- Sorbonne Université, INSERM, Association Institut de Myologie, Centre de Recherche en Myologie, Paris, France
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Nakamori M, Hamanaka K, Thomas JD, Wang ET, Hayashi YK, Takahashi MP, Swanson MS, Nishino I, Mochizuki H. Aberrant Myokine Signaling in Congenital Myotonic Dystrophy. Cell Rep 2017; 21:1240-1252. [PMID: 29091763 PMCID: PMC5689469 DOI: 10.1016/j.celrep.2017.10.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 09/02/2017] [Accepted: 10/04/2017] [Indexed: 02/07/2023] Open
Abstract
Myotonic dystrophy types 1 (DM1) and 2 (DM2) are dominantly inherited neuromuscular disorders caused by a toxic gain of function of expanded CUG and CCUG repeats, respectively. Although both disorders are clinically similar, congenital myotonic dystrophy (CDM), a severe DM form, is found only in DM1. CDM is also characterized by muscle fiber immaturity not observed in adult DM, suggesting specific pathological mechanisms. Here, we revealed upregulation of the interleukin-6 (IL-6) myokine signaling pathway in CDM muscles. We also found a correlation between muscle immaturity and not only IL-6 expression but also expanded CTG repeat length and CpG methylation status upstream of the repeats. Aberrant CpG methylation was associated with transcriptional dysregulation at the repeat locus, increasing the toxic RNA burden that upregulates IL-6. Because the IL-6 pathway is involved in myocyte maturation and muscle atrophy, our results indicate that enhanced RNA toxicity contributes to severe CDM phenotypes through aberrant IL-6 signaling.
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Affiliation(s)
- Masayuki Nakamori
- Department of Neurology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
| | - Kohei Hamanaka
- Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan
| | - James D Thomas
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Eric T Wang
- Department of Molecular Genetics and Microbiology, Center for NeuroGenetics and the Genetics Institute, University of Florida, College of Medicine, Gainesville, FL 32610, USA
| | - Yukiko K Hayashi
- Department of Pathophysiology, Tokyo Medical University, Shinjuku, Tokyo 160-0022, Japan
| | - Masanori P Takahashi
- Department of Neurology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan; Department of Functional Diagnostic Science, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
| | - 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
| | - Ichizo Nishino
- Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187-8502, Japan
| | - Hideki Mochizuki
- Department of Neurology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
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Gudde AEEG, van Kessel IDG, André LM, Wieringa B, Wansink DG. Trinucleotide-repeat expanded and normal DMPK transcripts contain unusually long poly(A) tails despite differential nuclear residence. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2017; 1860:740-749. [PMID: 28435090 DOI: 10.1016/j.bbagrm.2017.04.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 03/26/2017] [Accepted: 04/14/2017] [Indexed: 12/29/2022]
Abstract
In yeast and higher eukaryotes nuclear retention of transcripts may serve in control over RNA decay, nucleocytoplasmic transport and premature cytoplasmic appearance of mRNAs. Hyperadenylation of RNA is known to be associated with nuclear retention, but the cause-consequence relationship between hyperadenylation and regulation of RNA nuclear export is still unclear. We compared polyadenylation status between normal and expanded DMPK transcripts in muscle cells and tissues derived from unaffected individuals and patients with myotonic dystrophy type 1 (DM1). DM1 is an autosomal dominant disorder caused by (CTG)n repeat expansion in the DMPK gene. DM1 etiology is characterized by an almost complete block of nuclear export of DMPK transcripts carrying a long (CUG)n repeat, including aberrant sequestration of RNA-binding proteins. We show here by use of cell fractionation, RNA size separation and analysis of poly(A) tail length that a considerable fraction of transcripts from the normal DMPK allele is also retained in the nucleus (~30%). They carry poly(A) tails with an unusually broad length distribution, ranging between a few dozen to >500 adenosine residues. Remarkably, expanded DMPK (CUG)n transcripts from the mutant allele, almost exclusively nuclear, carry equally long poly(A) tails. Our findings thus suggest that nuclear retention may be a common feature of regulation of DMPK RNA expression. The typical forced nuclear residence of expanded DMPK transcripts affects this regulation in tissues of DM1 patients, but not through hyperadenylation.
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Affiliation(s)
- Anke E E G Gudde
- Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, Department of Cell Biology, Nijmegen, The Netherlands
| | - Ingeborg D G van Kessel
- Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, Department of Cell Biology, Nijmegen, The Netherlands
| | - Laurène M André
- Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, Department of Cell Biology, Nijmegen, The Netherlands
| | - Bé Wieringa
- Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, Department of Cell Biology, Nijmegen, The Netherlands
| | - Derick G Wansink
- Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, Department of Cell Biology, Nijmegen, The Netherlands.
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7
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Baptista H, Lopes Cardoso I. Steinert syndrome and repercussions in dental medicine. Arch Oral Biol 2017; 75:37-47. [DOI: 10.1016/j.archoralbio.2016.12.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 12/19/2016] [Accepted: 12/21/2016] [Indexed: 12/12/2022]
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8
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Smith CA, Gutmann L. Myotonic Dystrophy Type 1 Management and Therapeutics. Curr Treat Options Neurol 2016; 18:52. [DOI: 10.1007/s11940-016-0434-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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9
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Tan SV, Z'graggen WJ, Boërio D, Turner C, Hanna MG, Bostock H. In vivo assessment of muscle membrane properties in myotonic dystrophy. Muscle Nerve 2016; 54:249-57. [PMID: 26789642 DOI: 10.1002/mus.25025] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 12/16/2015] [Accepted: 12/28/2015] [Indexed: 11/07/2022]
Abstract
INTRODUCTION Myotonia in myotonic dystrophy types 1 (DM1) and 2 (DM2) is generally attributed to reduced chloride-channel conductance. We used muscle velocity recovery cycles (MVRCs) to investigate muscle membrane properties in DM1 and DM2, using comparisons with myotonia congenita (MC). METHODS MVRCs and responses to repetitive stimulation were compared between patients with DM1 (n = 18), DM2 (n = 5), MC (n = 18), and normal controls (n = 20). RESULTS Both DM1 and DM2 showed enhanced late supernormality after multiple conditioning stimuli, indicating delayed repolarization as in MC. Contrary to MC, however, DM1 showed reduced early supernormality after multiple conditioning stimuli, and weak DM1 patients also showed abnormally slow latency recovery after repetitive stimulation. CONCLUSIONS These findings support the presence of impaired chloride conductance in both DM1 and DM2. The early supernormality changes indicate that sodium currents were reduced in DM1, whereas the weakness-associated slow recovery after repetitive stimulation may provide an indication of reduced Na(+) /K(+) -ATPase activation. Muscle Nerve 54: 249-257, 2016.
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Affiliation(s)
- S Veronica Tan
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, The National, Queen Square, London, WC1N 3BG, UK.,Institute of Neurology, University College London, Queen Square, London, UK.,Department of Neurology and Neurophysiology, St Thomas' Hospital, Guy's and St Thomas' NHS Foundation Trust, London, UK.,Department of Academic Neurosciences, Kings College, London, UK
| | - Werner J Z'graggen
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.,Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
| | - Delphine Boërio
- Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.,Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
| | - Christopher Turner
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, The National, Queen Square, London, WC1N 3BG, UK.,Institute of Neurology, University College London, Queen Square, London, UK
| | - Michael G Hanna
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, The National, Queen Square, London, WC1N 3BG, UK.,Institute of Neurology, University College London, Queen Square, London, UK
| | - Hugh Bostock
- MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, The National, Queen Square, London, WC1N 3BG, UK.,Institute of Neurology, University College London, Queen Square, London, UK.,Department of Neurosurgery, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland.,Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Bern, Switzerland
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10
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Gudde AEEG, González-Barriga A, van den Broek WJAA, Wieringa B, Wansink DG. A low absolute number of expanded transcripts is involved in myotonic dystrophy type 1 manifestation in muscle. Hum Mol Genet 2016; 25:1648-62. [PMID: 26908607 PMCID: PMC4805313 DOI: 10.1093/hmg/ddw042] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 02/09/2016] [Indexed: 12/15/2022] Open
Abstract
Muscular manifestation of myotonic dystrophy type 1 (DM1), a common inheritable degenerative multisystem disorder, is mainly caused by expression of RNA from a (CTG·CAG)n-expanded DM1 locus. Here, we report on comparative profiling of expression of normal and expanded endogenous or transgenic transcripts in skeletal muscle cells and biopsies from DM1 mouse models and patients in order to help us in understanding the role of this RNA-mediated toxicity. In tissue of HSALR mice, the most intensely used ‘muscle-only’ model in the DM1 field, RNA from the α-actin (CTG)250 transgene was at least 1000-fold more abundant than that from the Dmpk gene, or the DMPK gene in humans. Conversely, the DMPK transgene in another line, DM500/DMSXL mice, was expressed ∼10-fold lower than the endogenous gene. Temporal regulation of expanded RNA expression differed between models. Onset of expression occurred remarkably late in HSALR myoblasts during in vitro myogenesis whereas Dmpk or DMPK (trans)genes were expressed throughout proliferation and differentiation phases. Importantly, quantification of absolute transcript numbers revealed that normal and expanded Dmpk/DMPK transcripts in mouse models and DM1 patients are low-abundance RNA species. Northern blotting, reverse transcriptase–quantitative polymerase chain reaction, RNA-sequencing and fluorescent in situ hybridization analyses showed that they occur at an absolute number between one and a few dozen molecules per cell. Our findings refine the current RNA dominance theory for DM1 pathophysiology, as anomalous factor binding to expanded transcripts and formation of soluble or insoluble ribonucleoprotein aggregates must be nucleated by only few expanded DMPK transcripts and therefore be a small numbers game.
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Affiliation(s)
- Anke E E G Gudde
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Anchel González-Barriga
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Walther J A A van den Broek
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Bé Wieringa
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Derick G Wansink
- Department of Cell Biology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
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11
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Antisense therapy in neurology. J Pers Med 2013; 3:144-76. [PMID: 25562650 PMCID: PMC4251390 DOI: 10.3390/jpm3030144] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 07/26/2013] [Accepted: 07/29/2013] [Indexed: 12/12/2022] Open
Abstract
Antisense therapy is an approach to fighting diseases using short DNA-like molecules called antisense oligonucleotides. Recently, antisense therapy has emerged as an exciting and promising strategy for the treatment of various neurodegenerative and neuromuscular disorders. Previous and ongoing pre-clinical and clinical trials have provided encouraging early results. Spinal muscular atrophy (SMA), Huntington’s disease (HD), amyotrophic lateral sclerosis (ALS), Duchenne muscular dystrophy (DMD), Fukuyama congenital muscular dystrophy (FCMD), dysferlinopathy (including limb-girdle muscular dystrophy 2B; LGMD2B, Miyoshi myopathy; MM, and distal myopathy with anterior tibial onset; DMAT), and myotonic dystrophy (DM) are all reported to be promising targets for antisense therapy. This paper focuses on the current progress of antisense therapies in neurology.
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12
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Sicot G, Gomes-Pereira M. RNA toxicity in human disease and animal models: from the uncovering of a new mechanism to the development of promising therapies. Biochim Biophys Acta Mol Basis Dis 2013; 1832:1390-409. [PMID: 23500957 DOI: 10.1016/j.bbadis.2013.03.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Revised: 03/01/2013] [Accepted: 03/04/2013] [Indexed: 01/06/2023]
Abstract
Mutant ribonucleic acid (RNA) molecules can be toxic to the cell, causing human disease through trans-acting dominant mechanisms. RNA toxicity was first described in myotonic dystrophy type 1, a multisystemic disorder caused by the abnormal expansion of a non-coding trinucleotide repeat sequence. The development of multiple and complementary animal models of disease has greatly contributed to clarifying the complex disease pathways mediated by toxic RNA molecules. RNA toxicity is not limited to myotonic dystrophy and spreads to an increasing number of human conditions, which share some unifying pathogenic events mediated by toxic RNA accumulation and disruption of RNA-binding proteins. The remarkable progress in the dissection of disease pathobiology resulted in the rational design of molecular therapies, which have been successfully tested in animal models. Toxic RNA diseases, and in particular myotonic dystrophy, clearly illustrate the critical contribution of animal models of disease in translational research: from gene mutation to disease mechanisms, and ultimately to therapy development. This article is part of a Special Issue entitled: Animal Models of Disease.
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13
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Hennessey JC, McGuire JJ. Attenuated vasodilator effectiveness of protease-activated receptor 2 agonist in heterozygous par2 knockout mice. PLoS One 2013; 8:e55965. [PMID: 23409098 PMCID: PMC3567012 DOI: 10.1371/journal.pone.0055965] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Accepted: 01/03/2013] [Indexed: 01/20/2023] Open
Abstract
Studies of homozygous PAR2 gene knockout mice have described a mix of phenotypic effects in vitro and in vivo. However, there have been few studies of PAR2 heterozygous (wild-type/knockout; PAR2-HET) mice. The phenotypes of many hemi and heterozygous transgenic mice have been described as intermediates between those of wild-type and knockout animals. In our study we aimed to determine the effects of intermediary par2 gene zygosity on vascular tissue responses to PAR2 activation. Specifically, we compared the vasodilator effectiveness of the PAR2 activating peptide 2-furoyl-LIGRLO-amide in aortas of wild-type PAR2 homozygous (PAR2-WT) and PAR2-HET mice. In myographs under isometric tension conditions, isolated aortic rings were contracted by alpha 1-adrenoeceptor agonist (phenylephrine), and thromboxane receptor agonist (U46619) and then relaxation responses by the additions of 2-furoyl-LIGRLO-amide, acetylcholine, and nitroprusside were recorded. A Schild regression analysis of the inhibition by a PAR2 antagonist (GB-83) of PAR2 agonist-induced aortic ring relaxations was used to compare receptor expression in PAR2-WT to PAR2-HET. PAR2 mRNA in aortas was measured by quantitative real-time PCR. In aortas contracted by either phenylephrine or U46619, the maximum relaxations induced by 2-furoyl-LIGRLO-amide were less in PAR2-HET than in the gender-matched PAR2-WT. GB-83 was 3- to 4-fold more potent for inhibition of 2fly in PAR2-HET than in PAR2-WT. PAR2 mRNA content of aortas from PAR2-HET was not significantly different than in PAR2-WT. Acetylcholine- and nitroprusside-induced relaxations of aortas from PAR2-HET were not significantly different than in PAR2-WT and PAR2 knockout. An interesting secondary finding was that relaxations induced by agonists of PAR2 and muscarinic receptors were larger in females than in males. We conclude that the lower PAR2-mediated responses in PAR2-HET aortas are consistent with evidence of a lower quantity of functional receptor expression, despite the apparently normal PAR2 mRNA content in PAR2-HET aortas.
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Affiliation(s)
- John C. Hennessey
- Cardiovascular Research Group, Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
| | - John J. McGuire
- Cardiovascular Research Group, Division of BioMedical Sciences, Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
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14
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Belzil VV, Gendron TF, Petrucelli L. RNA-mediated toxicity in neurodegenerative disease. Mol Cell Neurosci 2012; 56:406-19. [PMID: 23280309 DOI: 10.1016/j.mcn.2012.12.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 12/19/2012] [Accepted: 12/21/2012] [Indexed: 12/12/2022] Open
Abstract
Cellular viability depends upon the well-orchestrated functions carried out by numerous protein-coding and non-coding RNAs, as well as RNA-binding proteins. During the last decade, it has become increasingly evident that abnormalities in RNA processing represent a common feature among many neurodegenerative diseases. In "RNAopathies", which include diseases caused by non-coding repeat expansions, RNAs exert toxicity via diverse mechanisms: RNA foci formation, bidirectional transcription, and the production of toxic RNAs and proteins by repeat associated non-ATG translation. The mechanisms of toxicity in "RNA-binding proteinopathies", diseases in which RNA-binding proteins like TDP-43 and FUS play a prominent role, have yet to be fully elucidated. Nonetheless, both loss of function of the RNA binding protein, and a toxic gain of function resulting from its aggregation, are thought to be involved in disease pathogenesis. As part of the special issue on RNA and Splicing Regulation in Neurodegeneration, this review intends to explore the diverse RNA-related mechanisms contributing to neurodegeneration, with a special emphasis on findings emerging from animal models.
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Affiliation(s)
- Veronique V Belzil
- Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, USA
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15
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Udd B, Krahe R. The myotonic dystrophies: molecular, clinical, and therapeutic challenges. Lancet Neurol 2012; 11:891-905. [DOI: 10.1016/s1474-4422(12)70204-1] [Citation(s) in RCA: 335] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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16
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Harmon EB, Harmon ML, Larsen TD, Yang J, Glasford JW, Perryman MB. Myotonic dystrophy protein kinase is critical for nuclear envelope integrity. J Biol Chem 2011; 286:40296-306. [PMID: 21949239 DOI: 10.1074/jbc.m111.241455] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myotonic dystrophy 1 (DM1) is a multisystemic disease caused by a triplet nucleotide repeat expansion in the 3' untranslated region of the gene coding for myotonic dystrophy protein kinase (DMPK). DMPK is a nuclear envelope (NE) protein that promotes myogenic gene expression in skeletal myoblasts. Muscular dystrophy research has revealed the NE to be a key determinant of nuclear structure, gene regulation, and muscle function. To investigate the role of DMPK in NE stability, we analyzed DMPK expression in epithelial and myoblast cells. We found that DMPK localizes to the NE and coimmunoprecipitates with Lamin-A/C. Overexpression of DMPK in HeLa cells or C2C12 myoblasts disrupts Lamin-A/C and Lamin-B1 localization and causes nuclear fragmentation. Depletion of DMPK also disrupts NE lamina, showing that DMPK is required for NE stability. Our data demonstrate for the first time that DMPK is a critical component of the NE. These novel findings suggest that reduced DMPK may contribute to NE instability, a common mechanism of skeletal muscle wasting in muscular dystrophies.
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Affiliation(s)
- Erin B Harmon
- Cardiovascular Health Research Center, Sanford Research/USD, Sioux Falls, South Dakota 57104, USA.
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17
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Abstract
Myotonic dystrophies (dystrophia myotonica, or DM) are inherited disorders characterized by myotonia and progressive muscle degeneration, which are variably associated with a multisystemic phenotype. To date, two types of myotonic dystrophy, type 1 (DM1) and type 2 (DM2), are known to exist; both are autosomal dominant disorders caused by expansion of an untranslated short tandem repeat DNA sequence (CTG)(n) and (CCTG)(n), respectively. These expanded repeats in DM1 and DM2 show different patterns of repeat-size instability. Phenotypes of DM1 and DM2 are similar but there are some important differences, most conspicuously in the severity of the disease (including the presence or absence of the congenital form), muscles primarily affected (distal versus proximal), involved muscle fiber types (type 1 versus type 2 fibers), and some associated multisystemic phenotypes. The pathogenic mechanism of DM1 and DM2 is thought to be mediated by the mutant RNA transcripts containing expanded CUG and CCUG repeats. Strong evidence supports the hypothesis that sequestration of muscle-blind like (MBNL) proteins by these expanded repeats leads to misregulated splicing of many gene transcripts in corroboration with the raised level of CUG-binding protein 1. However, additional mechanisms, such as changes in the chromatin structure involving CTCN-binding site and gene expression dysregulations, are emerging. Although treatment of DM1 and DM2 is currently limited to supportive therapies, new therapeutic approaches based on pathogenic mechanisms may become feasible in the near future.
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Affiliation(s)
- Tetsuo Ashizawa
- Department of Neurology, McKnight Brain Institute, The University of Texas Medical Branch, Galveston, TX, USA.
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Nakamori M, Pearson CE, Thornton CA. Bidirectional transcription stimulates expansion and contraction of expanded (CTG)*(CAG) repeats. Hum Mol Genet 2010; 20:580-8. [PMID: 21088112 DOI: 10.1093/hmg/ddq501] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
More than 12 neurogenetic disorders are caused by unstable expansions of (CTG)•(CAG) repeats. The expanded repeats are unstable in germline and somatic cells, with potential consequences for disease severity. Previous studies have shown that contractions of (CAG)(95) are more frequent when the repeat tract is transcribed. Here we determined whether transcription can promote repeat expansion, using (CTG)•(CAG) repeat tracts in the size range that is typical for myotonic dystrophy type 1. We derived normal human fibroblasts having single-copy genomic integrations of 800 CTG repeats. The repeat tract showed modest instability when it was not transcribed, yielding an estimated mutation rate of 0.28% per generation. Instability was enhanced several-fold by transcription in the forward or reverse transcription, and 30-fold by bidirectional transcription, yielding many expansions and contractions of more than 200 repeats. These results suggest that convergent bidirectional transcription, which has been reported at several disease loci, could contribute to somatic instability of highly expanded (CTG)•(CAG) repeats.
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Affiliation(s)
- Masayuki Nakamori
- Department of Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
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19
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López Castel A, Nakamori M, Tomé S, Chitayat D, Gourdon G, Thornton CA, Pearson CE. Expanded CTG repeat demarcates a boundary for abnormal CpG methylation in myotonic dystrophy patient tissues. Hum Mol Genet 2010; 20:1-15. [PMID: 21044947 DOI: 10.1093/hmg/ddq427] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Myotonic dystrophy (DM1) affects multiple organs, shows age-dependent progression and is caused by CTG expansions at the DM1 locus. We determined the DM1 CpG methylation profile and CTG length in tissues from DM1 foetuses, DM1 adults, non-affected individuals and transgenic DM1 mice. Analysis included CTCF binding sites upstream and downstream of the CTG tract, as methylation-sensitive CTCF binding affects chromatinization and transcription of the DM1 locus. In humans, in a given foetus, expansions were largest in heart and smallest in liver, differing by 40-400 repeats; in adults, the largest expansions were in heart and cerebral cortex and smallest in cerebellum, differing by up to 5770 repeats in the same individual. Abnormal methylation was specific to the mutant allele. In DM1 adults, heart, liver and cortex showed high-to-moderate methylation levels, whereas cerebellum, kidney and skeletal muscle were devoid of methylation. Methylation decreased between foetuses and adults. Contrary to previous findings, methylation was not restricted to individuals with congenital DM1. The expanded repeat demarcates an abrupt boundary of methylation. Upstream sequences, including the CTCF site, were methylated, whereas the repeat itself and downstream sequences were not. In DM1 mice, expansion-, tissue- and age-specific methylation patterns were similar but not identical to those in DM1 individuals; notably in mice, methylation was present up- and downstream of the repeat, but greater upstream. Thus, in humans, the CpG-free expanded CTG repeat appears to maintain a highly polarized pattern of CpG methylation at the DM1 locus, which varies markedly with age and tissues.
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Affiliation(s)
- Arturo López Castel
- Genetics and Genome Biology, Department of Pediatrics, The Hospital for Sick Children, and Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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Raheem O, Olufemi SE, Bachinski LL, Vihola A, Sirito M, Holmlund-Hampf J, Haapasalo H, Li YP, Udd B, Krahe R. Mutant (CCTG)n expansion causes abnormal expression of zinc finger protein 9 (ZNF9) in myotonic dystrophy type 2. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 177:3025-36. [PMID: 20971734 DOI: 10.2353/ajpath.2010.100179] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The mutation that underlies myotonic dystrophy type 2 (DM2) is a (CCTG)n expansion in intron 1 of zinc finger protein 9 (ZNF9). It has been suggested that ZNF9 is of no consequence for disease pathogenesis. We determined the expression levels of ZNF9 during muscle cell differentiation and in DM2 muscle by microarray profiling, real-time RT-PCR, splice variant analysis, immunofluorescence, and Western blotting. Our results show that in differentiating myoblasts, ZNF9 protein was localized primarily to the nucleus, whereas in mature muscle fibers, it was cytoplasmic and organized in sarcomeric striations at the Z-disk. In patients with DM2, ZNF9 was abnormally expressed. First, there was an overall reduction in both the mRNA and protein levels. Second, the subcellular localization of the ZNF9 protein was somewhat less cytoplasmic and more membrane-bound. Third, our splice variant analysis revealed retention of intron 3 in an aberrant isoform, and fourth quantitative allele-specific expression analysis showed the persistence of intron 1 sequences from the abnormal allele, further suggesting that the mutant allele is incompletely spliced. Thus, the decrease in total expression appears to be due to impaired splicing of the mutant transcript. Our data indicate that ZNF9 expression in DM2 patients is altered at multiple levels. Although toxic RNA effects likely explain overlapping phenotypic manifestations between DM1 and DM2, abnormal ZNF9 levels in DM2 may account for the differences in DM1.
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Affiliation(s)
- Olayinka Raheem
- Neuromuscular Research Unit, University of Tampere and Tampere University Hospital, Tampere, Finland.
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21
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Schoser B, Timchenko L. Myotonic dystrophies 1 and 2: complex diseases with complex mechanisms. Curr Genomics 2010; 11:77-90. [PMID: 20885816 PMCID: PMC2874224 DOI: 10.2174/138920210790886844] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2009] [Revised: 11/22/2009] [Accepted: 11/25/2009] [Indexed: 11/22/2022] Open
Abstract
Two multi-system disorders, Myotonic Dystrophies type 1 and type 2 (DM1 and DM2), are complex neuromuscular diseases caused by an accumulation of expanded, non-coding RNAs, containing repetitive CUG and CCUG elements. Similarities of these mutations suggest similar mechanisms for both diseases. The expanded CUGn and CCUGn RNAs mainly target two RNA binding proteins, MBNL1 and CUGBP1, elevating levels of CUGBP1 and reducing levels of MBNL1. These alterations change processing of RNAs that are regulated by these proteins. Whereas overall toxicity of CUGn/CCUGn RNAs on RNA homeostasis in DM cells has been proven, the mechanisms which make these RNAs toxic remain illusive. A current view is that the toxicity of RNA CUGn and CCUGn is associated exclusively with global mis-splicing in DM patients. However, a growing number of new findings show that the expansion of CUGn and CCUGn RNAs mis-regulates several additional pathways in nuclei and cytoplasm of cells from patients with DM1 and DM2. The purpose of this review is to discuss the similarities and differences in the clinical presentation and molecular genetics of both diseases. We will also discuss the complexity of the molecular abnormalities in DM1 and DM2 caused by CUG and CCUG repeats and will summarize the outcomes of the toxicity of CUG and CCUG repeats.
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Affiliation(s)
- Benedikt Schoser
- Department of Neurology, Friedrich-Baur Institute, Ludwig-Maximilians-University, Ziemssenstr. 1a, Munich, Germany
| | - Lubov Timchenko
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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22
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Epigenetic changes and non-coding expanded repeats. Neurobiol Dis 2010; 39:21-7. [PMID: 20171282 DOI: 10.1016/j.nbd.2010.02.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 02/08/2010] [Accepted: 02/09/2010] [Indexed: 12/31/2022] Open
Abstract
Many neurogenetic disorders are caused by unstable expansions of tandem repeats. Some of the causal mutations are located in non-protein-coding regions of genes. When pathologically expanded, these repeats can trigger focal epigenetic changes that repress the expression of the mutant allele. When the mutant gene is not repressed, the transcripts containing the expanded repeat can give rise to a toxic gain-of-function by the mutant RNA. These two mechanisms, heterochromatin-mediated gene repression and RNA dominance, produce a wide range of neurodevelopmental and neurodegenerative abnormalities. Here we review the mechanisms of gene dysregulation induced by non-coding repeat expansions, and early indications that some of these disorders may prove to be responsive to therapeutic intervention.
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23
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Absence of a differentiation defect in muscle satellite cells from DM2 patients. Neurobiol Dis 2009; 36:181-90. [DOI: 10.1016/j.nbd.2009.07.009] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 07/07/2009] [Accepted: 07/16/2009] [Indexed: 01/01/2023] Open
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Harmon EB, Harmon ML, Larsen TD, Paulson AF, Perryman MB. Myotonic dystrophy protein kinase is expressed in embryonic myocytes and is required for myotube formation. Dev Dyn 2008; 237:2353-66. [DOI: 10.1002/dvdy.21653] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
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25
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Zhang L, Lee JE, Wilusz J, Wilusz CJ. The RNA-binding protein CUGBP1 regulates stability of tumor necrosis factor mRNA in muscle cells: implications for myotonic dystrophy. J Biol Chem 2008; 283:22457-63. [PMID: 18559347 DOI: 10.1074/jbc.m802803200] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Type I myotonic dystrophy (DM1) is caused by a triplet repeat expansion in the 3'-untranslated region (UTR) of the dystrophia myotonia protein kinase (DMPK) gene. Pathogenesis is closely linked with production of a toxic RNA from the mutant allele, which interferes with function of several RNA-binding proteins, including CUGBP1. Here we show that expression of a mutant DMPK 3'-UTR containing 960 CUG repeats is sufficient to increase expression and stability of an mRNA encoding the potent proinflammatory cytokine, tumor necrosis factor (TNF). CUGBP1 specifically recognizes sequences within the TNF 3'-UTR that are dissimilar from its canonical UG-rich binding site. Depletion of CUGBP1 from mouse myoblasts results in increased abundance of TNF mRNA through stabilization of the transcript. Moreover, activation of the protein kinase C pathway by treatment with phorbol ester, which has been shown previously to result in CUGBP1 phosphorylation, also causes TNF mRNA stabilization. Our results suggest that the elevated serum TNF seen in DM1 patients may be derived from muscle where it is induced by expression of toxic DMPK RNA. Importantly, overexpression of this potent cytokine could contribute to the muscle wasting and insulin resistance that are characteristic of this debilitating disease.
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Affiliation(s)
- Libin Zhang
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523, USA
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26
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Zühlke C, Roeder E, Purmann S, Wieczorek D, Curry C, Loustalet C, Hellenbroich Y, Richardt HH, Gillessen-Kaesbach G. Homozygous myotonic dystrophy: Clinical findings in two patients and review of the literature. Am J Med Genet A 2007; 143A:2058-61. [PMID: 17663477 DOI: 10.1002/ajmg.a.31772] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Christine Zühlke
- Institut für Humangenetik, Universitätsklinikum Schleswig-Holstein, Campus Lübeck, Germany.
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27
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Medica I, Teran N, Volk M, Pfeifer V, Ladavac E, Peterlin B. Patients with primary cataract as a genetic pool of DMPK protomutation. J Hum Genet 2006; 52:123-128. [PMID: 17146587 DOI: 10.1007/s10038-006-0091-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Accepted: 11/02/2006] [Indexed: 02/04/2023]
Abstract
Myotonic dystrophy 1 (DM1) is known to diminish reproductive fitness in its severe form. Since no de novo mutations are known for this disease, it has the tendency to become extinct from a population. To explain the preservation of DM1 in a population, a hypothesis that a pool of subjects for the mutated gene exists in the apparently healthy (non-DM1) population was tested. In order to determine the (CTG) repeat number, PCR was performed in 274 patients found to have primary cataract of adult onset who showed no DM1 symptoms, and were not related to DM1 patients. In four cataract patients (1.46%; 95% CI 0.5-3.7), a protomutation in the myotonin protein kinase gene was found which might lead to a complete mutation after transmission through the next generations. The number of (CTG) repeats in the remaining 270 cataract patients did not differ significantly from the control subjects in terms of the distribution of larger [(CTG)n > or = 19] versus smaller [(CTG)n < 19] alleles. We consider the primary cataract patients to be the pool of DMPK protomutation from which DM1 mutation is maintained in the population.
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Affiliation(s)
- Igor Medica
- Division of Medical Genetics, Department of Obstetrics and Gynaecology, University Medical Centre Ljubljana, Šlajmerjeva 3, 1000, Ljubljana, Slovenia
- Outpatient Paediatric Clinic Pula, Pula, Croatia
| | - Natasa Teran
- Division of Medical Genetics, Department of Obstetrics and Gynaecology, University Medical Centre Ljubljana, Šlajmerjeva 3, 1000, Ljubljana, Slovenia
| | - Marija Volk
- Division of Medical Genetics, Department of Obstetrics and Gynaecology, University Medical Centre Ljubljana, Šlajmerjeva 3, 1000, Ljubljana, Slovenia
| | - Vladimir Pfeifer
- Department of Ophtalmology, University Medical Centre Ljubljana, Ljubljana, Slovenia
| | - Edi Ladavac
- Department of Ophtalmology, General Hospital Pula, Pula, Croatia
| | - Borut Peterlin
- Division of Medical Genetics, Department of Obstetrics and Gynaecology, University Medical Centre Ljubljana, Šlajmerjeva 3, 1000, Ljubljana, Slovenia.
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Cho DH, Thienes CP, Mahoney SE, Analau E, Filippova GN, Tapscott SJ. Antisense Transcription and Heterochromatin at the DM1 CTG Repeats Are Constrained by CTCF. Mol Cell 2005; 20:483-9. [PMID: 16285929 DOI: 10.1016/j.molcel.2005.09.002] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2005] [Revised: 08/17/2005] [Accepted: 09/02/2005] [Indexed: 11/30/2022]
Abstract
Prior studies of the DM1 locus have shown that the CTG repeats are a component of a CTCF-dependent insulator element and that repeat expansion results in conversion of the region to heterochromatin. We now show that the DM1 insulator is maintained in a local heterochromatin context: an antisense transcript emanating from the adjacent SIX5 regulatory region extends into the insulator element and is converted into 21 nucleotide (nt) fragments with associated regional histone H3 lysine 9 (H3-K9) methylation and HP1gamma recruitment that is embedded within a region of euchromatin-associated H3 lysine 4 (H3-K4) methylation. CTCF restricts the extent of the antisense RNA at the wild-type (wt) DM1 locus and constrains the H3-K9 methylation to the nucleosome associated with the CTG repeat, whereas the expanded allele in congenital DM1 is associated with loss of CTCF binding, spread of heterochromatin, and regional CpG methylation.
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Affiliation(s)
- Diane H Cho
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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29
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Machuca-Tzili L, Brook D, Hilton-Jones D. Clinical and molecular aspects of the myotonic dystrophies: a review. Muscle Nerve 2005; 32:1-18. [PMID: 15770660 DOI: 10.1002/mus.20301] [Citation(s) in RCA: 145] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Type 1 myotonic dystrophy or DM1 (Steinert's disease), which is the commonest muscular dystrophy in adults, has intrigued physicians for over a century. Unusual features, compared with other dystrophies, include myotonia, anticipation, and involvement of other organs, notably the brain, eyes, smooth muscle, cardiac conduction apparatus, and endocrine system. Morbidity is high, with a substantial mortality relating to cardiorespiratory dysfunction. More recently a second form of multisystem myotonic disorder has been recognized and variously designated as proximal myotonic myopathy (PROMM), proximal myotonic dystrophy (PDM), or DM2. For both DM1 and DM2 the molecular basis is expansion of an unstable repeat sequence in a noncoding part of a gene (DMPK in DM1 and ZNF9 in DM2). There is accumulating evidence that the basic molecular mechanism is disruption of mRNA metabolism, which has far-reaching effects on many other genes, in part through the induction of aberrant splicing, explaining the multisystemic nature of the disease. The unstable nature of the expansion provides a molecular explanation for anticipation. This review emphasizes the clinical similarities and differences between DM1 and DM2. It examines current views about the molecular basis of these disorders, and contrasts them with other repeat expansion disorders that have increasingly been recognized as a cause of neurological disease.
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Affiliation(s)
- Laura Machuca-Tzili
- Department of Genetics, University of Nottingham, Nottingham, United Kingdom
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30
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Mulvihill DJ, Nichol Edamura K, Hagerman KA, Pearson CE, Wang YH. Effect of CAT or AGG Interruptions and CpG Methylation on Nucleosome Assembly upon Trinucleotide Repeats on Spinocerebellar Ataxia, Type 1 and Fragile X Syndrome*. J Biol Chem 2005; 280:4498-503. [PMID: 15574425 DOI: 10.1074/jbc.m413239200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nucleosome packaging regulates many aspects of DNA metabolism and is thought to mediate genetic instability and transcription of expanded trinucleotide repeats. Both instability and transcription are sensitive to repeat length, tract purity, and CpG methylation. CAT or AGG interruptions within the (CAG)n or (CGG)n tracts of spinocerebellar ataxia, type 1 or fragile X syndrome, respectively, confer increased genetic stability to the repeats. We report the formation of nucleosomes on sequences containing pure and interrupted (CAG)n and (CGG)n repeats having lengths above and below the genetic stability thresholds. Increased lengths of pure repeats led to increased and decreased propensities for nucleosome assembly on the (CAG)n and (CGG)n repeats, respectively. CpG methylation of the CGG repeat further reduced assembly. CAT interruptions in (CAG)n tracts decreased nucleosome assembly. In contrast, AGG interruptions in (CGG)n tracts did not affect assembly by hypoacetylated histones. The latter observation was unaltered by CpG methylation of the repeats. However, nucleosome assembly by hyperacetylated histones on interrupted CGG tracts was increased relative to pure tracts and this effect was abolished by CpG methylation. Thus, CAT or AGG interruptions can modulate the ability of (CAG)n and (CGG) tracts to assemble into chromatin and the effect of the AGG interruptions is dependent upon both the methylation status of the DNA and the acetylation status of the histones. Compared with the genetically unstable pure repeats, both interruptions permit a propensity of nucleosome assembly closer to that of random (genetically stable) sequences, suggesting an association of nucleosome assembly of trinucleotide repeats and genetic instability.
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Affiliation(s)
- David J Mulvihill
- Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA
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31
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Ranum LPW, Day JW. Myotonic dystrophy: RNA pathogenesis comes into focus. Am J Hum Genet 2004; 74:793-804. [PMID: 15065017 PMCID: PMC1181975 DOI: 10.1086/383590] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2003] [Accepted: 02/12/2004] [Indexed: 01/10/2023] Open
Abstract
Myotonic dystrophy (DM)--the most common form of muscular dystrophy in adults, affecting 1/8000 individuals--is a dominantly inherited disorder with a peculiar and rare pattern of multisystemic clinical features affecting skeletal muscle, the heart, the eye, and the endocrine system. Two genetic loci have been associated with the DM phenotype: DM1, on chromosome 19, and DM2, on chromosome 3. In 1992, the mutation responsible for DM1 was identified as a CTG expansion located in the 3' untranslated region of the dystrophia myotonica-protein kinase gene (DMPK). How this untranslated CTG expansion causes myotonic dystrophy type 1(DM1) has been controversial. The recent discovery that myotonic dystrophy type 2 (DM2) is caused by an untranslated CCTG expansion, along with other discoveries on DM1 pathogenesis, indicate that the clinical features common to both diseases are caused by a gain-of-function RNA mechanism in which the CUG and CCUG repeats alter cellular function, including alternative splicing of various genes. We discuss the pathogenic mechanisms that have been proposed for the myotonic dystrophies, the clinical and molecular features of DM1 and DM2, and the characterization of murine and cell-culture models that have been generated to better understand these diseases.
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Affiliation(s)
- Laura P W Ranum
- Institute of Human Genetics, University of Minnesota, Minneapolis, MN 55455, USA.
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32
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Wansink DG, Wieringa B. Transgenic mouse models for myotonic dystrophy type 1 (DM1). Cytogenet Genome Res 2004; 100:230-42. [PMID: 14526185 DOI: 10.1159/000072859] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2002] [Accepted: 12/18/2002] [Indexed: 11/19/2022] Open
Abstract
The study of animal models for myotonic dystrophy type 1 (DM1) has helped us to 'de- and reconstruct' our ideas on how the highly variable multisystemic constellation of disease features can be caused by only one type of event, i.e., the expansion of a perfect (CTG)(n) repeat in the DM1 locus on 19q. Evidence is now accumulating that cell type, cell state and species dependent activities of the DNA replication/repair/recombination machinery contribute to the intergenerational and somatic behavior of the (CTG)(n) repeat at the DNA level. At the RNA level, a gain-of-function mechanism, with dominant toxic effects of (CUG)(n) repeat containing transcripts, probably has a central role in DM1 pathology. Parallel study of DM2, a closely related form of myotonic dystrophy, has revealed a similar mechanism, but also made clear that part of the attention should remain focused on a possible role for candidate loss-of-function genes from the DM1 locus itself (like DMWD, DMPK and SIX5) or elsewhere in the genome, to find explanations for clinical aspects that are unique to DM1. This review will focus on new insight regarding structure-function features of candidate genes involved in DM1 pathobiology, and on the mechanisms of expansion and disease pathology that have now partly been disclosed with the help of transgenic animal models.
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Affiliation(s)
- D G Wansink
- Department of Cell Biology, NCMLS, University Medical Center, Nijmegen, The Netherlands
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33
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Saveliev A, Everett C, Sharpe T, Webster Z, Festenstein R. DNA triplet repeats mediate heterochromatin-protein-1-sensitive variegated gene silencing. Nature 2003; 422:909-13. [PMID: 12712207 DOI: 10.1038/nature01596] [Citation(s) in RCA: 189] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2002] [Accepted: 03/12/2003] [Indexed: 11/08/2022]
Abstract
Gene repression is crucial to the maintenance of differentiated cell types in multicellular organisms, whereas aberrant silencing can lead to disease. The organization of DNA into chromatin and heterochromatin is implicated in gene silencing. In chromatin, DNA wraps around histones, creating nucleosomes. Further condensation of chromatin, associated with large blocks of repetitive DNA sequences, is known as heterochromatin. Position effect variegation (PEV) occurs when a gene is located abnormally close to heterochromatin, silencing the affected gene in a proportion of cells. Here we show that the relatively short triplet-repeat expansions found in myotonic dystrophy and Friedreich's ataxia confer variegation of expression on a linked transgene in mice. Silencing was correlated with a decrease in promoter accessibility and was enhanced by the classical PEV modifier heterochromatin protein 1 (HP1). Notably, triplet-repeat-associated variegation was not restricted to classical heterochromatic regions but occurred irrespective of chromosomal location. Because the phenomenon described here shares important features with PEV, the mechanisms underlying heterochromatin-mediated silencing might have a role in gene regulation at many sites throughout the mammalian genome and modulate the extent of gene silencing and hence severity in several triplet-repeat diseases.
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Affiliation(s)
- Alexander Saveliev
- CSC Gene Control Mechanisms and Disease Group, Experimental Genetics, Faculty of Medicine, Imperial College School of Medicine, Hammersmith Campus, Du Cane Road, London W12 0NN, UK
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34
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Matsuura T, Ashizawa T. Spinocerebellar ataxia type 10: a disease caused by a large ATTCT repeat expansion. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 516:79-97. [PMID: 12611436 DOI: 10.1007/978-1-4615-0117-6_4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Tohru Matsuura
- Department of Neurology, Baylor College of Medicine and Veterans Affairs Medical Center, Houston, Texas 77030 USA
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35
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Timchenko LT, Tapscott SJ, Cooper TA, Monckton DG. Myotonic dystrophy: discussion of molecular basis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 516:27-45. [PMID: 12611434 DOI: 10.1007/978-1-4615-0117-6_2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Lubov T Timchenko
- Section of Cardiovascular Sciences, Department of Medicine, Baylor College of Medicine, Houston, TX 77030, USA
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Fabre E, Dujon B, Richard GF. Transcription and nuclear transport of CAG/CTG trinucleotide repeats in yeast. Nucleic Acids Res 2002; 30:3540-7. [PMID: 12177295 PMCID: PMC134249 DOI: 10.1093/nar/gkf483] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Trinucleotide repeats are involved in several neurological disorders in humans. DNA sequences containing CAG/CTG repeats are prone to slippage during replication and double-strand break repair. The effects of trinucleotide repeats on transcription and on nuclear export were analyzed in vivo in yeast. Transcription of a CAG/CTG trinucleotide repeat in the 3'-untranslated region of a URA3 reporter gene leads to transcription of messenger RNAs several kilobases longer than the expected size. These long mRNAs form more readily when CAG rather than CTG repeats are transcribed. CAG- or CUG-containing transcripts show a non-homogeneous cellular localization. We propose that long mRNAs result from transcription slippage, and discuss the possible implications for human diseases.
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Affiliation(s)
- Emmanuelle Fabre
- Unité de Génétique Moléculaire des Levures (URA 2171 CNRS and UFR 927 Université Pierre et Marie Curie) Institut Pasteur, 25 rue du Dr Roux, 75724 Paris cedex 15, France.
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37
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Quintero-Mora ML, Depardon F, Cisneros B. Expanded CTG repeats inhibit neuronal differentiation of the PC12 cell line. Biochem Biophys Res Commun 2002; 295:289-94. [PMID: 12150945 DOI: 10.1016/s0006-291x(02)00660-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Myotonic dystrophy (DM) is a dominant neuromuscular disorder caused by the expansion of trinucleotide CTG repeats in the 3-untranslated region (3'-UTR) of the MtPK gene. Although DM-associated mental retardation suggests that neuronal functions are disturbed by the expansion mutation, the effect of this alteration in neuronal cells has not been approached. In this study we established stable transfectans of PC12 neuronal cell line expressing the reporter gene CAT alone (empty-vector clone) or fused to the MtPK 3'-UTR with 5, 60, or 90 CTG repeats (CTG5, CTG60, and CTG90 clones, respectively). CTG90 cells exhibited a suppression of NGF-induced neuronal differentiation while empty-vector, CTG5 and CTG60 clones differentiated normally. CTG90 cells displayed normal activation of early differentiation markers, ERK1/2, but the up-regulation of the late marker MAP2 was dramatically reduced. Our neuronal cell system provides the first information of how the mutant MtPK 3'-UTR mRNA affects neuronal functions.
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Affiliation(s)
- María Leonor Quintero-Mora
- Departamento de Genética y Biología Molecular, Centro de Investigación y Estudios Avanzados del IPN, Avenida Instituto Politécnico Nacional 2508, Apartado Postal 14-740, C.P. 07000 Mexico D.F., Mexico
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38
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Abstract
Within the closing decade of the twentieth century, 14 neurological disorders were shown to result from the expansion of unstable trinucleotide repeats, establishing this once unique mutational mechanism as the basis of an expanding class of diseases. Trinucleotide repeat diseases can be categorized into two subclasses based on the location of the trinucleotide repeats: diseases involving noncoding repeats (untranslated sequences) and diseases involving repeats within coding sequences (exonic). The large body of knowledge accumulating in this fast moving field has provided exciting clues and inspired many unresolved questions about the pathogenesis of diseases caused by expanded trinucleotide repeats. This review summarizes the current understanding of the molecular pathology of each of these diseases, starting with a clinical picture followed by a focused description of the disease genes, the proteins involved, and the studies that have lent insight into their pathophysiology.
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Affiliation(s)
- C J Cummings
- Program in Cell and Molecular Biology, Department of Pediatrics, Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas 77030, USA.
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39
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Tanner SM, Austin JL, Leone G, Rush LJ, Plass C, Heinonen K, Mrózek K, Sill H, Knuutila S, Kolitz JE, Archer KJ, Caligiuri MA, Bloomfield CD, de La Chapelle A. BAALC, the human member of a novel mammalian neuroectoderm gene lineage, is implicated in hematopoiesis and acute leukemia. Proc Natl Acad Sci U S A 2001; 98:13901-6. [PMID: 11707601 PMCID: PMC61139 DOI: 10.1073/pnas.241525498] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The molecular basis of human leukemia is heterogeneous. Cytogenetic findings are increasingly associated with molecular abnormalities, some of which are being understood at the functional level. Specific therapies can be developed based on such knowledge. To search for new genes in the acute leukemias, we performed a representational difference analysis. We describe a human gene in chromosome 8q22.3, BAALC (brain and acute leukemia, cytoplasmic), that is highly conserved among mammals but evidently absent from lower organisms. We characterized BAALC on the genomic level and investigated its expression pattern in human and mouse, as well as its complex splicing behavior. In vitro studies of the protein showing its subcellular localization suggest a function in the cytoskeleton network. Two isoforms are specifically expressed in neuroectoderm-derived tissues, but not in tumors or cancer cell lines of nonneural tissue origin. We show that blasts from a subset of patients with acute leukemia greatly overexpress eight different BAALC transcripts, resulting in five protein isoforms. Among patients with acute myeloid leukemia, those overexpressing BAALC show distinctly poor prognosis, pointing to a key role of the BAALC products in leukemia. Our data suggest that BAALC is a gene implicated in both neuroectodermal and hematopoietic cell functions.
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Affiliation(s)
- S M Tanner
- Human Cancer Genetics Program, Ohio State University, 646 Medical Research Facility, 420 West 12th Avenue, Columbus, OH 43210, USA
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40
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Furling D, Lemieux D, Taneja K, Puymirat J. Decreased levels of myotonic dystrophy protein kinase (DMPK) and delayed differentiation in human myotonic dystrophy myoblasts. Neuromuscul Disord 2001; 11:728-35. [PMID: 11595515 DOI: 10.1016/s0960-8966(01)00226-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Muscle cell cultures derived from a myotonic dystrophy (DM1) fetus were established in order to determine on the one hand, whether the differentiation of DM1 myoblasts is altered and, on the other hand, whether the levels of myotonic dystrophy protein kinase (DMPK) protein is decreased in DM1 muscle cells. DM1 myoblasts isolated from a quadriceps of a 12-weeks old fetus proliferate at a similar rate as normal myoblasts isolated from a quadriceps of an unaffected 15-weeks old fetus but their maturation is altered as shown by the decreased levels in slow myosin heavy chain protein. In contrast, no change was observed in the expression of vimentin, myogenin and embryonic myosin heavy chain. The levels of DMPK transcripts sharply increased during myoblast differentiation and the mutant DMPK transcripts are retained in discrete foci in the nuclei of muscle cells. The levels of 85-kDa DMPK protein was reduced by about 50% in DM1 cells compared with normal cells. Our study demonstrates that delay in DM1 myoblast maturation is associated with nuclear retention of mutant DMPK transcripts and decreased levels of DMPK protein.
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Affiliation(s)
- D Furling
- Laboratory of Human Genetics, Department of Medicine, Laval University Medical Research Center, CHUQ, 2705 Boulevard Laurier, Ste-Foy, Quebec, Canada
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41
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Galvão R, Mendes-Soares L, Câmara J, Jaco I, Carmo-Fonseca M. Triplet repeats, RNA secondary structure and toxic gain-of-function models for pathogenesis. Brain Res Bull 2001; 56:191-201. [PMID: 11719250 DOI: 10.1016/s0361-9230(01)00651-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Ten years after the discovery of human diseases caused by trinucleotide repeat expansions, searching for mechanistic links between gene mutation and pathological phenotype remains a fundamental and unsolved issue. Evidence accumulated so far indicates that the pathogenesis of repeat disorders is complex and multi-factorial. Diseases caused by CAG expansions coding for polyglutamine tracts have been extensively studied, and in most cases a toxic gain-of-function of the mutant protein was demonstrated. Most recently, tracking the effects of repeats along the pathway of gene expression is providing additional clues to understand how a triplet repeat expansion can cause disease. Expanded repeats form DNA secondary structures that confer genetic instability, and most likely contribute to alter the local chromatin configuration leading to transcriptional silencing. At the level of RNA, the expanded repeat may either interfere with processing of the primary transcript, resulting in deficit of the corresponding protein, or interact with RNA-binding proteins altering their normal activity. The latter mechanism, termed RNA gain-of-function, has no precedents in human genetics. Recent evidence suggests that expanded RNAs and associated RNA-binding proteins are potential contributors to the pathogenesis of several triplet repeat diseases.
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Affiliation(s)
- R Galvão
- Institute of Histology and Embryology, Faculty of Medicine, University of Lisbon, Lisbon, Portugal
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Eriksson M, Hedberg B, Carey N, Ansved T. Decreased DMPK transcript levels in myotonic dystrophy 1 type IIA muscle fibers. Biochem Biophys Res Commun 2001; 286:1177-82. [PMID: 11527424 DOI: 10.1006/bbrc.2001.5516] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Myotonic dystrophy 1 is caused by the expansion of a CTG trinucleotide repeat on chromosome 19q13.3. The repeat lies in the 3' untranslated region of the myotonic dystrophy protein kinase gene (DMPK), and it has been hypothesised that the expansion alters the expression levels of DMPK and/or its neighbouring genes, DMWD and SIX5. Published data remain controversial, partly due to the mixed cell populations found in most tissues examined. We have microdissected human skeletal muscle biopsies from myotonic dystrophy 1 patients and controls and analysed gene expression at this locus for type I and type IIA fibres, using quantitative real-time reverse transcription-polymerase chain reaction. Levels of DMPK expression were specifically decreased in the type IIA fibres of myotonic dystrophy patients, below the levels found in controls. This suggests that DMPK expression is altered in this disease, suggesting significant pathological consequences.
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Affiliation(s)
- M Eriksson
- Department of Molecular Medicine, Karolinska Institutet, Karolinska Hospital, Stockholm, 171 76, Sweden.
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43
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Frisch R, Singleton KR, Moses PA, Gonzalez IL, Carango P, Marks HG, Funanage VL. Effect of triplet repeat expansion on chromatin structure and expression of DMPK and neighboring genes, SIX5 and DMWD, in myotonic dystrophy. Mol Genet Metab 2001; 74:281-91. [PMID: 11592825 DOI: 10.1006/mgme.2001.3229] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Myotonic dystrophy (DM), an autosomal dominant neuromuscular disease, is associated with expansion of a polymorphic (CTG)n repeat in the 3'-untranslated region of the DM protein kinase (DMPK) gene. The repeat expansion results in decreased levels of DMPK mRNA and protein, but the mechanism for this decreased expression is unknown. Loss of a nuclease-hypersensitive site in the region of the repeat expansion has been observed in muscle and skin fibroblasts from DM patients, indicating a change in local chromatin structure. This change in chromatin structure has been proposed as a mechanism whereby the expression of DMPK and neighboring genes, sine oculis homeobox (Drosophila) homolog 5 (SIX5) and dystrophia myotonica-containing WD repeat motif (DMWD), might be affected. We have developed a polymerase chain reaction (PCR)-based method to assay the chromatin sensitivity of the region adjacent to the repeat expansion in somatic cell hybrids carrying either normal or affected DMPK alleles and show that hybrids carrying expanded alleles exhibit decreased sensitivity to PvuII digestion in this region. Semiquantitative multiplex reverse transcriptase PCR (RT/PCR) assays of gene expression from the chromosomes carrying the expanded alleles showed marked reduction of DMPK mRNA, partial inhibition of SIX5 expression from a congenital DM chromosome, and no reduction of DMWD mRNA. Nested RT/PCR analysis of DMPK mRNA from somatic cell hybrids carrying the repeat expansions revealed that most of the DMPK transcripts expressed from the expanded alleles lacked exons 13 and 14, whereas full-length transcripts were expressed predominantly from the normal alleles. These results suggest that the CTG repeat expansion leads to a decrease in DMPK mRNA levels by affecting splicing at the 3' end of the DMPK pre-mRNA transcript.
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Affiliation(s)
- R Frisch
- Department of Medical Research, Nemours Children's Clinic, Wilmington, Delaware 19803, USA
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44
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Filippova GN, Thienes CP, Penn BH, Cho DH, Hu YJ, Moore JM, Klesert TR, Lobanenkov VV, Tapscott SJ. CTCF-binding sites flank CTG/CAG repeats and form a methylation-sensitive insulator at the DM1 locus. Nat Genet 2001; 28:335-43. [PMID: 11479593 DOI: 10.1038/ng570] [Citation(s) in RCA: 232] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
An expansion of a CTG repeat at the DM1 locus causes myotonic dystrophy (DM) by altering the expression of the two adjacent genes, DMPK and SIX5, and through a toxic effect of the repeat-containing RNA. Here we identify two CTCF-binding sites that flank the CTG repeat and form an insulator element between DMPK and SIX5. Methylation of these sites prevents binding of CTCF, indicating that the DM1 locus methylation in congenital DM would disrupt insulator function. Furthermore, CTCF-binding sites are associated with CTG/CAG repeats at several other loci. We suggest a general role for CTG/CAG repeats as components of insulator elements at multiple sites in the human genome.
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Affiliation(s)
- G N Filippova
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
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45
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Fardaei M, Larkin K, Brook JD, Hamshere MG. In vivo co-localisation of MBNL protein with DMPK expanded-repeat transcripts. Nucleic Acids Res 2001; 29:2766-71. [PMID: 11433021 PMCID: PMC55763 DOI: 10.1093/nar/29.13.2766] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Myotonic dystrophy (DM1) is the most common form of adult muscular dystrophy and is inherited as an autosomal dominant trait. The genetic basis of DM1 is the expansion of a CTG repeat in the 3' untranslated region of a protein kinase gene (DMPK). The molecular mechanism by which this expanded repeat produces the pathophysiology of DM1 remains unknown. Transcripts from the expanded allele accumulate as foci in the nucleus of DM1 cells and it has been suggested that these transcript foci sequester cellular proteins that are required for normal nuclear function. We have investigated the role of three RNA-binding proteins, CUG-BP, hnRNP C and MBNL, as possible sequestered factors. Using a combination of indirect immunofluorescence to detect endogenous proteins and overexpression of proteins with green fluorescent protein (GFP) tags we have shown that CUG-BP and hnRNP C do not co-localise with expanded repeat foci in DM1 cell lines. However, GFP-tagged MBNL does itself form foci in DM1 cell lines and co-localises with the foci of expanded repeat transcripts. GFP-tagged MBNL does not appear as foci in non-DM1 cell lines. This work provides further support for the involvement of MBNL in DM1.
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Affiliation(s)
- M Fardaei
- Institute of Genetics, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, UK
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46
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Ueda H, Ohno S, Kobayashi T. Myotonic dystrophy and myotonic dystrophy protein kinase. PROGRESS IN HISTOCHEMISTRY AND CYTOCHEMISTRY 2001; 35:187-251. [PMID: 11064921 DOI: 10.1016/s0079-6336(00)80002-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Myotonic dystrophy protein kinase (DMPK) was designated as a gene responsible for myotonic dystrophy (DM) on chromosome 19, because the gene product has extensive homology to protein kinase catalytic domains. DM is the most common disease with multisystem disorders among muscular dystrophies. The genetic basis of DM is now known to include mutational expansion of a repetitive trinucleotide sequence (CTG)n in the 3'-untranslated region (UTR) of DMPK. Full-length DMPK was detected and various isoforms of DMPK have been reported in skeletal and cardiac muscles, central nervous tissues, etc. DMPK is localized predominantly in type I muscle fibers, muscle spindles, neuromuscular junctions and myotendinous tissues in skeletal muscle. In cardiac muscle it is localized in intercalated dises and Purkinje fibers. Electron microscopically it is detected in the terminal cisternae of SR in skeletal muscle and the junctional and corbular SR in cardia muscle. In central nervous system, it is located in many neurons, especially in the cytoplasm of cerebellar Purkinje cells, hippocampal interneurons and spinal motoneurons. Electron microscopically it is detected in rough endoplasmic reticulum. The functional role of DMPK is not fully understood, however, it may play an important role in Ca2+ homeostasis and signal transduction system. Diseased amount of DMPK may play an important role in the degeneration of skeletal muscle in adult type DM. However, other molecular pathogenetical mechanisms such as dysfunction of surrounding genes by structural change of the chromosome by long trinucleotide repeats, and the trans-gain of function of CUG-binding proteins might be responsible to induce multisystemic disorders of DM such as myotonia, endocrine dysfunction, etc.
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Affiliation(s)
- H Ueda
- Department of Anatomy, Yamanashi Medical University, Japan
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47
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Depardon F, Cisneros B, Alonso-Vilatela E, Montañez C. Myotonic dystrophy protein kinase (DMPK) gene expression in lymphocytes of patients with myotonic dystrophy. Arch Med Res 2001; 32:123-8. [PMID: 11343809 DOI: 10.1016/s0188-4409(01)00263-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Myotonic dystrophy (DM) is an autosomal dominant neuromuscular disorder with defects in many tissues, including skeletal muscle myotonia, progressive myopathy, and abnormalities in heart, brain, and endocrine systems. It is associated with a trinucleotide repeat occurring in the 3' (UTR) untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. Several studies have been carried out to determine DMPK gene expression in muscle and non-muscle tissues. METHODS DMPK gene expression was determined in lymphocytes of adult-onset patients with DM and normal controls. To quantitate total locus expression as well as allele-specific mRNA levels, semiquantitative RT-PCR assay was used. Allele-specific expression was analyzed using a Bpm1 polymorphism located at exon 10 of the DMPK gene. RESULTS In heterozygous patients with DM, we observed a fourfold difference between mRNA levels produced by the Bpm1-undigested allele (187 bp) compared to the Bpm1-digested allele (136 bp). By using (CTG) trinucleotide (with cytosine, thymine, and guanine) expansion polymorphism, it was shown that the down-regulated allele corresponds to the mutant allele. Interestingly, the reduction in the mutant allele-transcript levels is compensated by an increase of the wild-type allele, yielding no significant differences in total locus mRNA amount between patients and normal individuals. CONCLUSIONS These results suggest that the expression of the two alleles at the DMPK locus in lymphocytes is coordinated. The reduction in mutant-allele transcript levels is compensated by an increase in wild-type allele mRNA levels.
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Affiliation(s)
- F Depardon
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados (CINVESTAV), Mexico City, Mexico
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48
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Good PJ, Chen Q, Warner SJ, Herring DC. A family of human RNA-binding proteins related to the Drosophila Bruno translational regulator. J Biol Chem 2000; 275:28583-92. [PMID: 10893231 DOI: 10.1074/jbc.m003083200] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The post-transcriptional regulation of gene expression by RNA-binding proteins is an important element in controlling both normal cell functions and animal development. The diverse roles are demonstrated by the Elav family of RNA-binding proteins, where various members have been shown to regulate several processes involving mRNA. We have identified another family of RNA-binding proteins distantly related to the Elav family but closely related to Bruno, a translational regulator in Drosophila melanogaster. In humans, six Bruno-like genes have been identified, whereas other species such as Drosophila, Xenopus laevis, and Caenorhabditis elegans have at least two members of this family, and related genes have also been detected in plants and ascidians. The human BRUNOL2 and BRUNOL3 are 92% identical in the RNA-binding domains, although the BRUNOL2 gene is expressed ubiquitously whereas BRUNOL3 is expressed predominantly in the heart, muscle, and nervous system. Both of these proteins bind the same target RNA, the Bruno response element. The RNA-binding domain that recognizes the Bruno response element is composed of two consecutive RNA recognition motifs at the amino terminus of vertebrate Bruno protein. The possible involvement of the Bruno family of proteins in the CUG repeat expansion disease myotonic dystrophy is discussed.
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Affiliation(s)
- P J Good
- Department of Biochemistry and Molecular Biology and Feist-Weiller Cancer Center, Louisiana State University, Health Sciences Center, Shreveport, Lousiana 71130, USA.
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49
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Inukai A, Doyu M, Kato T, Liang Y, Kuru S, Yamamoto M, Kobayashi Y, Sobue G. Reduced expression of DMAHP/SIX5 gene in myotonic dystrophy muscle. Muscle Nerve 2000; 23:1421-6. [PMID: 10951446 DOI: 10.1002/1097-4598(200009)23:9<1421::aid-mus14>3.0.co;2-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In myotonic dystrophy (DM), the expansion of CTG triplet repeats in the 3'-untranslated region of DM-protein kinase (DMPK) is a causal gene mutation. However, the pathogenic molecular mechanism of CTG repeat expansion for DM phenotypic expression is unclear. To investigate this issue, we examined the influence of CTG repeat expansion on the expression levels of DMPK gene and 3'-flanking DM locus-associated homeodomain protein (DMAHP)/SIX5 gene in the muscles of DM patients. We isolated RNA from muscle tissues of six DM patients and six controls, and performed a competitive reverse transcriptional polymerase chain reaction (RT-PCR) assay. The total mRNA level of DMAHP/SIX5 was significantly lower in DM than in controls, but the DMPK mRNA level was unchanged. Our results suggest that CTG repeat expansion influences the expression of genes other than DMPK to cause the DM phenotype.
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Affiliation(s)
- A Inukai
- Department of Neurology, Nagoya University School of Medicine, Japan
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50
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Miller JW, Urbinati CR, Teng-Umnuay P, Stenberg MG, Byrne BJ, Thornton CA, Swanson MS. Recruitment of human muscleblind proteins to (CUG)(n) expansions associated with myotonic dystrophy. EMBO J 2000; 19:4439-48. [PMID: 10970838 PMCID: PMC302046 DOI: 10.1093/emboj/19.17.4439] [Citation(s) in RCA: 685] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2000] [Accepted: 06/28/2000] [Indexed: 11/12/2022] Open
Abstract
Myotonic dystrophy (DM1) is an autosomal dominant neuromuscular disorder associated with a (CTG)(n) expansion in the 3'-untranslated region of the DM1 protein kinase (DMPK) gene. To explain disease pathogenesis, the RNA dominance model proposes that the DM1 mutation produces a gain-of-function at the RNA level in which CUG repeats form RNA hairpins that sequester nuclear factors required for proper muscle development and maintenance. Here, we identify the triplet repeat expansion (EXP) RNA-binding proteins as candidate sequestered factors. As predicted by the RNA dominance model, binding of the EXP proteins is specific for dsCUG RNAs and proportional to the size of the triplet repeat expansion. Remarkably, the EXP proteins are homologous to the Drosophila muscleblind proteins required for terminal differentiation of muscle and photoreceptor cells. EXP expression is also activated during mammalian myoblast differentiation, but the EXP proteins accumulate in nuclear foci in DM1 cells. We propose that DM1 disease is caused by aberrant recruitment of the EXP proteins to the DMPK transcript (CUG)(n) expansion.
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Affiliation(s)
- J W Miller
- Department of Molecular Genetics and Microbiology, Centers for Gene Therapy and Mammalian Genetics, University of Florida College of Medicine, Gainesville, FL 32610, USA
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