1
|
Chung Liang L, Sulaiman N, Yazid MD. A Decade of Progress in Gene Targeted Therapeutic Strategies in Duchenne Muscular Dystrophy: A Systematic Review. Front Bioeng Biotechnol 2022; 10:833833. [PMID: 35402409 PMCID: PMC8984139 DOI: 10.3389/fbioe.2022.833833] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 01/31/2022] [Indexed: 02/01/2023] Open
Abstract
As one of the most severe forms of muscle dystrophy, Duchenne muscular dystrophy (DMD) results in progressive muscle wasting, ultimately resulting in premature death due to cardiomyopathy. In the many years of research, the solution to DMD remains palliative. Although numerous studies including clinical trials have provided promising results, approved drugs, even, the therapeutic window is still minimal with many shortcomings to be addressed. Logically, to combat DMD that arose from a single genetic mutation with gene therapy made sense. However, gene-based strategies as a treatment option are no stranger to drawbacks and limitations such as the size of the dystrophin gene and possibilities of vectors to elicit immune responses. In this systematic review, we aim to provide a comprehensive compilation on gene-based therapeutic strategies and critically evaluate the approaches relative to its efficacy and feasibility while addressing their current limitations. With the keywords “DMD AND Gene OR Genetic AND Therapy OR Treatment,” we reviewed papers published in Science Direct, PubMed, and ProQuest over the past decade (2012–2021).
Collapse
Affiliation(s)
- Lam Chung Liang
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, Malaysia
| | - Nadiah Sulaiman
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, Malaysia
| | - Muhammad Dain Yazid
- Centre for Tissue Engineering and Regenerative Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, Malaysia
| |
Collapse
|
2
|
Waldrop MA, Moore SA, Mathews KD, Darbro BW, Medne L, Finkel R, Connolly AM, Crawford TO, Drachman D, Wein N, Habib AA, Krzesniak-Swinarska MA, Zaidman CM, Collins JJ, Jokela M, Udd B, Day JW, Ortiz-Guerrero G, Statland J, Butterfield RJ, Dunn DM, Weiss RB, Flanigan KM. Intron mutations and early transcription termination in Duchenne and Becker muscular dystrophy. Hum Mutat 2022; 43:511-528. [PMID: 35165973 PMCID: PMC9901284 DOI: 10.1002/humu.24343] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 02/05/2022] [Accepted: 02/07/2022] [Indexed: 11/11/2022]
Abstract
DMD pathogenic variants for Duchenne and Becker muscular dystrophy are detectable with high sensitivity by standard clinical exome analyses of genomic DNA. However, up to 7% of DMD mutations are deep intronic and analysis of muscle-derived RNA is an important diagnostic step for patients who have negative genomic testing but abnormal dystrophin expression in muscle. In this study, muscle biopsies were evaluated from 19 patients with clinical features of a dystrophinopathy, but negative clinical DMD mutation analysis. Reverse transcription-polymerase chain reaction or high-throughput RNA sequencing methods identified 19 mutations with one of three pathogenic pseudoexon types: deep intronic point mutations, deletions or insertions, and translocations. In association with point mutations creating intronic splice acceptor sites, we observed the first examples of DMD pseudo 3'-terminal exon mutations causing high efficiency transcription termination within introns. This connection between splicing and premature transcription termination is reminiscent of U1 snRNP-mediating telescripting in sustaining RNA polymerase II elongation across large genes, such as DMD. We propose a novel classification of three distinct types of mutations identifiable by muscle RNA analysis, each of which differ in potential treatment approaches. Recognition and appropriate characterization may lead to therapies directed toward full-length dystrophin expression for some patients.
Collapse
Affiliation(s)
- Megan A. Waldrop
- The Center for Gene Therapy, Nationwide Children’s Hospital, Columbus, OH 43205,Department of Neurology, The Ohio State University, Columbus, OH 43205,Department of Pediatrics, The Ohio State University, Columbus, OH 43205
| | - Steven A. Moore
- Department of Pathology, The University of Iowa, Iowa City, IA, 52242
| | | | | | - Livja Medne
- Children’s Hospital of Philadelphia, Philadelphia, PA 19104
| | | | - Anne M. Connolly
- Department of Neurology, Washington University, Saint Louis, MO 63110
| | | | | | - Nicolas Wein
- The Center for Gene Therapy, Nationwide Children’s Hospital, Columbus, OH 43205
| | | | | | - Craig M. Zaidman
- Department of Neurology, Washington University, Saint Louis, MO 63110
| | - James J. Collins
- Department of Pediatric Neurology, Mercy Hospitals, Springfield, MO 65804
| | - Manu Jokela
- Neuromuscular Research Center, Tampere University Hospital and University of Tampere, Tampere, Finland,Division of Clinical Neurosciences, Turku University Hospital and University of Turku, Turku, Finland
| | - Bjarne Udd
- Neuromuscular Research Center, Tampere University Hospital and University of Tampere, Tampere, Finland
| | - John W. Day
- Department of Neurology, University of Minnesota Medical Center, Minneapolis, MN 55454
| | | | - Jeff Statland
- Department of Neurology, University of Kansas, Kansas City, KS
| | - Russell J. Butterfield
- Department of Pediatrics, The University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Diane M. Dunn
- Department of Human Genetics, The University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Robert B. Weiss
- Department of Pediatrics, The University of Utah School of Medicine, Salt Lake City, UT 84112,Department of Human Genetics, The University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Kevin M. Flanigan
- The Center for Gene Therapy, Nationwide Children’s Hospital, Columbus, OH 43205,Department of Neurology, The Ohio State University, Columbus, OH 43205,Department of Pediatrics, The Ohio State University, Columbus, OH 43205
| |
Collapse
|
3
|
Keegan NP, Wilton SD, Fletcher S. Analysis of Pathogenic Pseudoexons Reveals Novel Mechanisms Driving Cryptic Splicing. Front Genet 2022; 12:806946. [PMID: 35140743 PMCID: PMC8819188 DOI: 10.3389/fgene.2021.806946] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 12/09/2021] [Indexed: 12/16/2022] Open
Abstract
Understanding pre-mRNA splicing is crucial to accurately diagnosing and treating genetic diseases. However, mutations that alter splicing can exert highly diverse effects. Of all the known types of splicing mutations, perhaps the rarest and most difficult to predict are those that activate pseudoexons, sometimes also called cryptic exons. Unlike other splicing mutations that either destroy or redirect existing splice events, pseudoexon mutations appear to create entirely new exons within introns. Since exon definition in vertebrates requires coordinated arrangements of numerous RNA motifs, one might expect that pseudoexons would only arise when rearrangements of intronic DNA create novel exons by chance. Surprisingly, although such mutations do occur, a far more common cause of pseudoexons is deep-intronic single nucleotide variants, raising the question of why these latent exon-like tracts near the mutation sites have not already been purged from the genome by the evolutionary advantage of more efficient splicing. Possible answers may lie in deep intronic splicing processes such as recursive splicing or poison exon splicing. Because these processes utilize intronic motifs that benignly engage with the spliceosome, the regions involved may be more susceptible to exonization than other intronic regions would be. We speculated that a comprehensive study of reported pseudoexons might detect alignments with known deep intronic splice sites and could also permit the characterisation of novel pseudoexon categories. In this report, we present and analyse a catalogue of over 400 published pseudoexon splice events. In addition to confirming prior observations of the most common pseudoexon mutation types, the size of this catalogue also enabled us to suggest new categories for some of the rarer types of pseudoexon mutation. By comparing our catalogue against published datasets of non-canonical splice events, we also found that 15.7% of pseudoexons exhibit some splicing activity at one or both of their splice sites in non-mutant cells. Importantly, this included seven examples of experimentally confirmed recursive splice sites, confirming for the first time a long-suspected link between these two splicing phenomena. These findings have the potential to improve the fidelity of genetic diagnostics and reveal new targets for splice-modulating therapies.
Collapse
Affiliation(s)
- Niall P. Keegan
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
- *Correspondence: Niall P. Keegan,
| | - Steve D. Wilton
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
| | - Sue Fletcher
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, WA, Australia
- Centre for Neuromuscular and Neurological Disorders, Perron Institute for Neurological and Translational Science, The University of Western Australia, Perth, WA, Australia
| |
Collapse
|
4
|
Andrews JG, Lamb MM, Conway KM, Street N, Westfield C, Ciafaloni E, Matthews D, Pandya S. Differentiation of Pediatric-Onset Duchenne and Becker Muscular Dystrophy Subphenotypes Using Data from the Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet). J Neuromuscul Dis 2022; 9:171-178. [PMID: 34776418 PMCID: PMC9059491 DOI: 10.3233/jnd-210739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) phenotypes are used to describe disease progression in affected individuals. However, considerable heterogeneity has been observed across and within these two phenotypes, suggesting a spectrum of severity rather than distinct conditions. Characterizing the phenotypes and subphenotypes aids researchers in the design of clinical studies and clinicians in providing anticipatory guidance to affected individuals and their families. Using data from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet), we used K-means cluster analysis to group phenotypically similar males with pediatric-onset dystrophinopathy. We identified four dystrophinopathy clusters: Classical BMD, Classical DMD, late ambulatory DMD, and severe DMD. The clusters that we identified align with both 'classical' and 'non-classical' dystrophinopathy described in the literature. Individuals with dystrophinopathies have heterogenous clinical presentations that cluster into phenotypically similar groups. Use of clinically-derived phenotyping may provide a clearer understanding of disease trajectories, reduce variability in study results, and prevent exclusion of certain cohorts from analysis. Findings from studying subphenotypes may ultimately improve our ability to predict disease progression.
Collapse
Affiliation(s)
- Jennifer G. Andrews
- Department of Pediatrics, University of Arizona, Tucson, USA,Correspondence to: Jennifer G. Andrews, Department of Pediatrics, University of Arizona, PO Box 245073, AZ 857-5073, Tucson. Tel.: (520) 626 6816; Fax: (520) 626 8056,
| | - Molly M. Lamb
- Department of Epidemiology, Colorado School of Public Health, University of Colorado, Aurora, USA
| | - Kristin M. Conway
- Department of Epidemiology, College of Public Health, The University of Iowa, Iowa City, USA
| | - Natalie Street
- National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, USA
| | | | - Emma Ciafaloni
- Department of Neurology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, USA
| | - Dennis Matthews
- Physical Medicine and Rehabilitation, School of Medicine, University of Colorado, Aurora, USA
| | - Shree Pandya
- Department of Neurology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, USA
| | | |
Collapse
|
5
|
Petersen USS, Doktor TK, Andresen BS. Pseudoexon activation in disease by non-splice site deep intronic sequence variation - wild type pseudoexons constitute high-risk sites in the human genome. Hum Mutat 2021; 43:103-127. [PMID: 34837434 DOI: 10.1002/humu.24306] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 11/02/2021] [Accepted: 11/06/2021] [Indexed: 12/27/2022]
Abstract
Accuracy of pre-messenger RNA (pre-mRNA) splicing is crucial for normal gene expression. Complex regulation supports the spliceosomal distinction between authentic exons and the many seemingly functional splice sites delimiting pseudoexons. Pseudoexons are nonfunctional intronic sequences that can be activated for aberrant inclusion in mRNA, which may cause disease. Pseudoexon activation is very challenging to predict, in particular when activation occurs by sequence variants that alter the splicing regulatory environment without directly affecting splice sites. As pseudoexon inclusion often evades detection due to activation of nonsense-mediated mRNA decay, and because conventional diagnostic procedures miss deep intronic sequence variation, pseudoexon activation is a heavily underreported disease mechanism. Pseudoexon characteristics have mainly been studied based on in silico predicted sequences. Moreover, because recognition of sequence variants that create or strengthen splice sites is possible by comparison with well-established consensus sequences, this type of pseudoexon activation is by far the most frequently reported. Here we review all known human disease-associated pseudoexons that carry functional splice sites and are activated by deep intronic sequence variants located outside splice site sequences. We delineate common characteristics that make this type of wild type pseudoexons distinct high-risk sites in the human genome.
Collapse
Affiliation(s)
- Ulrika S S Petersen
- Department of Biochemistry and Molecular Biology and the Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Thomas K Doktor
- Department of Biochemistry and Molecular Biology and the Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Brage S Andresen
- Department of Biochemistry and Molecular Biology and the Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| |
Collapse
|
6
|
Verdile V, Guizzo G, Ferrante G, Paronetto MP. RNA Targeting in Inherited Neuromuscular Disorders: Novel Therapeutic Strategies to Counteract Mis-Splicing. Cells 2021; 10:cells10112850. [PMID: 34831073 PMCID: PMC8616048 DOI: 10.3390/cells10112850] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 10/08/2021] [Accepted: 10/18/2021] [Indexed: 01/14/2023] Open
Abstract
Neuromuscular disorders represent multifaceted abnormal conditions, with little or no cure, leading to patient deaths from complete muscle wasting and atrophy. Despite strong efforts in the past decades, development of effective treatments is still urgently needed. Advent of next-generation sequencing technologies has allowed identification of novel genes and mutations associated with neuromuscular pathologies, highlighting splicing defects as essential players. Deciphering the significance and relative contributions of defective RNA metabolism will be instrumental to address and counteract these malignancies. We review here recent progress on the role played by alternative splicing in ensuring functional neuromuscular junctions (NMJs), and its involvement in the pathogenesis of NMJ-related neuromuscular disorders, with particular emphasis on congenital myasthenic syndromes and muscular dystrophies. We will also discuss novel strategies based on oligonucleotides designed to bind their cognate sequences in the RNA or targeting intermediary of mRNA metabolism. These efforts resulted in several chemical classes of RNA molecules that have recently proven to be clinically effective, more potent and better tolerated than previous strategies.
Collapse
Affiliation(s)
- Veronica Verdile
- Laboratory of Molecular and Cellular Neurobiology, Fondazione Santa Lucia, CERC, 00143 Rome, Italy; (V.V.); (G.G.); (G.F.)
- Department of Movement, Human and Health Sciences, University of Rome Foro Italico, Piazza Lauro de Bosis 6, 00135 Rome, Italy
| | - Gloria Guizzo
- Laboratory of Molecular and Cellular Neurobiology, Fondazione Santa Lucia, CERC, 00143 Rome, Italy; (V.V.); (G.G.); (G.F.)
| | - Gabriele Ferrante
- Laboratory of Molecular and Cellular Neurobiology, Fondazione Santa Lucia, CERC, 00143 Rome, Italy; (V.V.); (G.G.); (G.F.)
| | - Maria Paola Paronetto
- Laboratory of Molecular and Cellular Neurobiology, Fondazione Santa Lucia, CERC, 00143 Rome, Italy; (V.V.); (G.G.); (G.F.)
- Department of Movement, Human and Health Sciences, University of Rome Foro Italico, Piazza Lauro de Bosis 6, 00135 Rome, Italy
- Correspondence:
| |
Collapse
|
7
|
Geng C, Tong Y, Zhang S, Ling C, Wu X, Wang D, Dai Y. Sequence and Structure Characteristics of 22 Deletion Breakpoints in Intron 44 of the DMD Gene Based on Long-Read Sequencing. Front Genet 2021; 12:638220. [PMID: 34211494 PMCID: PMC8240811 DOI: 10.3389/fgene.2021.638220] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 03/29/2021] [Indexed: 12/27/2022] Open
Abstract
Purpose: Exon deletions make up to 80% of mutations in the DMD gene, which cause Duchenne and Becker muscular dystrophy. Exon 45-55 regions were reported as deletion hotspots and intron 44 harbored more than 25% of deletion start points. We aimed to investigate the fine structures of breakpoints in intron 44 to find potential mechanisms of large deletions in intron 44. Methods: Twenty-two dystrophinopathy patients whose deletion started in intron 44 were sequenced using long-read sequencing of a DMD gene capture panel. Sequence homology, palindromic sequences, and polypyrimidine sequences were searched at the breakpoint junctions. RepeatMasker was used to analyze repetitive elements and Mfold was applied to predict secondary DNA structure. Results: With a designed DMD capture panel, 22 samples achieved 2.25 gigabases and 1.28 million reads on average. Average depth was 308× and 99.98% bases were covered at least 1×. The deletion breakpoints in intron 44 were scattered and no breakpoints clustered in any region less than 500 bp. A total of 72.7% of breakpoints located in distal 100 kb of intron 44 and more repetitive elements were found in this region. Microhomologies of 0–1 bp were found in 36.4% (8/22) of patients, which corresponded with non-homologous end-joining. Microhomologies of 2–20 bp were found in 59.1% (13/22) of patients, which corresponded with microhomology-mediated end-joining. Moreover, a 7 bp insertion was found in one patient, which might be evidence of aberrant replication origin firing. Palindromic sequences, polypyrimidine sequences, and small hairpin loops were found near several breakpoint junctions. No evidence of large hairpin loop formation in deletion root sequences was observed. Conclusion: This study was the first to explore possible mechanisms underlying exon deletions starting from intron 44 of the DMD gene based on long-read sequencing. Diverse mechanisms might be associated with deletions in the DMD gene.
Collapse
Affiliation(s)
- Chang Geng
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Yuanren Tong
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | | | - Chao Ling
- Laboratory of Clinical Genetics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| | - Xin Wu
- GrandOmics Biosciences, Beijing, China
| | | | - Yi Dai
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
| |
Collapse
|
8
|
Abstract
The DMD gene is the largest in the human genome, with a total intron content exceeding 2.2Mb. In the decades since DMD was discovered there have been numerous reported cases of pseudoexons (PEs) arising in the mature DMD transcripts of some individuals, either as the result of mutations or as low-frequency errors of the spliceosome. In this review, I collate from the literature 58 examples of DMD PEs and examine the diversity and commonalities of their features. In particular, I note the high frequency of PEs that arise from deep intronic SNVs and discuss a possible link between PEs induced by distal mutations and the regulation of recursive splicing.
Collapse
Affiliation(s)
- Niall P Keegan
- Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University and Perron Institute, Perth, Australia
| |
Collapse
|
9
|
Xie Z, Sun C, Liu Y, Yu M, Zheng Y, Meng L, Wang G, Cornejo-Sanchez DM, Bharadwaj T, Yan J, Zhang L, Pineda-Trujillo N, Zhang W, Leal SM, Schrauwen I, Wang Z, Yuan Y. Practical approach to the genetic diagnosis of unsolved dystrophinopathies: a stepwise strategy in the genomic era. J Med Genet 2020; 58:743-751. [PMID: 32978268 DOI: 10.1136/jmedgenet-2020-107113] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 07/02/2020] [Accepted: 08/08/2020] [Indexed: 12/18/2022]
Abstract
OBJECTIVE To investigate the diagnostic value of implementing a stepwise genetic testing strategy (SGTS) in genetically unsolved cases with dystrophinopathies. METHODS After routine genetic testing in 872 male patients with highly suspected dystrophinopathies, we identified 715 patients with a pathogenic DMD variant. Of the 157 patients who had no pathogenic DMD variants and underwent a muscle biopsy, 142 patients were confirmed to have other myopathies, and 15 suspected dystrophinopathies remained genetically undiagnosed. These 15 patients underwent a more comprehensive evaluation as part of the SGTS pipeline, which included the stepwise analysis of dystrophin mRNA, short-read whole-gene DMD sequencing, long-read whole-gene DMD sequencing and in silico bioinformatic analyses. RESULTS SGTS successfully yielded a molecular diagnosis of dystrophinopathy in 11 of the 15 genetically unsolved cases. We identified 8 intronic and 2 complex structural variants (SVs) leading to aberrant splicing in 10 of 11 patients, of which 9 variants were novel. In one case, a molecular defect was detected on mRNA and protein level only. Aberrant splicing mechanisms included 6 pseudoexon inclusions and 4 alterations of splice sites and splicing regulatory elements. We showed for the first time the exonisation of a MER48 element as a novel pathogenic mechanism in dystrophinopathies. CONCLUSION Our study highlights the high diagnostic utility of implementing a SGTS pipeline in dystrophinopathies with intronic variants and complex SVs.
Collapse
Affiliation(s)
- Zhiying Xie
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Chengyue Sun
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Yilin Liu
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Meng Yu
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Yiming Zheng
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Lingchao Meng
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Gao Wang
- Center for Statistical Genetics, Sergievsky Center, Taub Institute for Alzheimer's Disease and the Aging Brain, and the Department of Neurology, Columbia University Medical Center, New York, New York, USA
| | - Diana M Cornejo-Sanchez
- Center for Statistical Genetics, Sergievsky Center, Taub Institute for Alzheimer's Disease and the Aging Brain, and the Department of Neurology, Columbia University Medical Center, New York, New York, USA
| | - Thashi Bharadwaj
- Center for Statistical Genetics, Sergievsky Center, Taub Institute for Alzheimer's Disease and the Aging Brain, and the Department of Neurology, Columbia University Medical Center, New York, New York, USA
| | - Jin Yan
- Science and Technology, Beijing Epigen Medical Technology Inc, Beijing, China
| | - Lingxiang Zhang
- Science and Technology, Beijing Epigen Medical Technology Inc, Beijing, China
| | - Nicolas Pineda-Trujillo
- Grupo Mapeo Genetico, Departamento de Pediatría, Facultad de Medicina, Universidad de Antioquia, Medellin, Colombia
| | - Wei Zhang
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Suzanne M Leal
- Center for Statistical Genetics, Sergievsky Center, Taub Institute for Alzheimer's Disease and the Aging Brain, and the Department of Neurology, Columbia University Medical Center, New York, New York, USA
| | - Isabelle Schrauwen
- Center for Statistical Genetics, Sergievsky Center, Taub Institute for Alzheimer's Disease and the Aging Brain, and the Department of Neurology, Columbia University Medical Center, New York, New York, USA
| | - Zhaoxia Wang
- Department of Neurology, Peking University First Hospital, Beijing, China
| | - Yun Yuan
- Department of Neurology, Peking University First Hospital, Beijing, China
| |
Collapse
|
10
|
Greer K, Johnsen R, Nevo Y, Fellig Y, Fletcher S, Wilton SD. Single Exon Skipping Can Address a Multi-Exon Duplication in the Dystrophin Gene. Int J Mol Sci 2020; 21:ijms21124511. [PMID: 32630425 PMCID: PMC7350004 DOI: 10.3390/ijms21124511] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 12/13/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is a severe muscle wasting disease typically caused by protein-truncating mutations that preclude synthesis of a functional dystrophin. Exonic deletions are the most common type of DMD lesion, however, whole exon duplications account for between 10–15% of all reported mutations. Here, we describe in vitro evaluation of antisense oligonucleotide-induced splice switching strategies to re-frame the transcript disrupted by a multi-exon duplication within the DMD gene. Phosphorodiamidate morpholino oligomers and phosphorodiamidate morpholino oligomers coupled to a cell penetrating peptide were evaluated in a Duchenne muscular dystrophy patient cell strain carrying an exon 14–17 duplication. Two strategies were employed; the conventional approach was to remove both copies of exon 17 in addition to exon 18, and the second strategy was to remove only the first copy of exon 17. Both approaches result in a larger than normal but in-frame DMD transcript, but surprisingly, the removal of only the first exon 17 appeared to be more efficient in restoring dystrophin, as determined using western blotting. The emergence of a normal sized DMD mRNA transcript that was not apparent in untreated samples may have arisen from back splicing and could also account for some of the dystrophin protein being produced.
Collapse
Affiliation(s)
- Kane Greer
- Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University, Murdoch 6150, Australia
- Perron Institute for Neurological and Translational Science, Perth 6009, Australia
| | - Russell Johnsen
- Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University, Murdoch 6150, Australia
- Perron Institute for Neurological and Translational Science, Perth 6009, Australia
| | - Yoram Nevo
- Institute of Neurology, Schneider Children's Medical Center of Israel, Tel-Aviv University,Tel-Aviv 62919, Israel
| | - Yakov Fellig
- Pathology Department, Hadassah-Hebrew-University Medical Center, Jerusalem 91120, Israel
| | - Susan Fletcher
- Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University, Murdoch 6150, Australia
- Perron Institute for Neurological and Translational Science, Perth 6009, Australia
- Centre for Neuromuscular & Neurological Disorders, University of Western Australia, Perth 6009, Australia
| | - Steve D Wilton
- Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University, Murdoch 6150, Australia
- Perron Institute for Neurological and Translational Science, Perth 6009, Australia
- Centre for Neuromuscular & Neurological Disorders, University of Western Australia, Perth 6009, Australia
| |
Collapse
|
11
|
Breakpoint junction features of seven DMD deletion mutations. Hum Genome Var 2019; 6:39. [PMID: 31645977 PMCID: PMC6804640 DOI: 10.1038/s41439-019-0070-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Revised: 07/22/2019] [Accepted: 07/23/2019] [Indexed: 11/25/2022] Open
Abstract
Duchenne muscular dystrophy is an inherited muscle wasting disease with severe symptoms and onset in early childhood. Duchenne muscular dystrophy is caused by loss-of-function mutations, most commonly deletions, within the DMD gene. Characterizing the junction points of large genomic deletions facilitates a more detailed model of the origins of these mutations and allows for a greater understanding of phenotypic variations associated with particular genotypes, potentially providing insights into the deletion mechanism. Here, we report sequencing of breakpoint junctions for seven patients with intragenic, whole-exon DMD deletions. Of the seven junction sequences identified, we found one instance of a “clean” break, three instances of microhomology (2–5 bp) at the junction site, and three complex rearrangements involving local sequences. Bioinformatics analysis of the upstream and downstream breakpoint regions revealed a possible role of short inverted repeats in the initiation of some of these deletion events. Researchers in Australia have identified new examples of the genomic factors and mechanisms that lead to deletions linked with Duchenne muscular dystrophy (DMD). DMD is an inherited neuromuscular disease which causes progressive deterioration of muscles and, in some cases, intellectual impairment. Using samples from seven DMD patients, Niall Keegan of Murdoch University in Perth and colleagues sequenced the DNA left behind around the deletions in the DMD gene which cause the disease. They found one clean break, three sections with short repeated sequences, and three with more complex rearrangements. The diversity of these findings led them to suggest that the deletions resulted from a diversity of genomic factors and repair mechanisms. Future work could incorporate these findings into a model to predict where deletions will occur, expanding our understanding of DMD and its causes.
Collapse
|
12
|
de Boer M, van Leeuwen K, Hauri-Hohl M, Roos D. Activation of cryptic splice sites in three patients with chronic granulomatous disease. Mol Genet Genomic Med 2019; 7:e854. [PMID: 31364312 PMCID: PMC6732321 DOI: 10.1002/mgg3.854] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 05/24/2019] [Accepted: 06/05/2019] [Indexed: 01/07/2023] Open
Abstract
Background Chronic granulomatous disease (CGD) is a primary immune deficiency caused by mutations in the genes encoding the structural components of the phagocyte NADPH oxidase. As a result, the patients cannot generate sufficient amounts of reactive oxygen species required for killing pathogenic microorganisms. Methods We analyzed NADPH oxidase activity and component expression in neutrophils, performed genomic DNA and cDNA analysis, and used mRNA splicing prediction tools to evaluate the impact of mutations. Results In two patients with CGD, we had previously found mutations that cause aberrant pre‐mRNA splicing. In one patient an exonic mutation in a cryptic donor splice site caused the deletion of the 3' part of exon 6 from the mRNA of CYBB. This patient suffers from X‐linked CGD. The second patient, with autosomal CGD, has a mutation in the donor splice site of intron 1 of CYBA that activates a cryptic donor splice site downstream in intron 1, causing the insertion of intronic sequences in the mRNA. The third patient, recently analyzed, also with autosomal CGD, has a mutation in intron 4 of CYBA, 15 bp from the acceptor splice site. This mutation weakens a branch site and activates a cryptic acceptor splice site, causing the insertion of 14 intronic nucleotides into the mRNA. Conclusion We found three different mutations, one exonic, one in a donor splice site and one intronic, that all caused missplicing of pre‐mRNA. We analyzed these mutations with four different splice prediction programs and found that predictions of splice site strength, splice enhancer and splice silencer protein binding and branch site strength are all essential for correct prediction of pre‐mRNA splicing.
Collapse
Affiliation(s)
- Martin de Boer
- Sanquin Research and Landsteiner Laboratory, Amsterdam Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Karin van Leeuwen
- Sanquin Research and Landsteiner Laboratory, Amsterdam Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Mathias Hauri-Hohl
- Department of Stem Cell Transplantation Research, University Children's Hospital Zürich, Zürich, Switzerland
| | - Dirk Roos
- Sanquin Research and Landsteiner Laboratory, Amsterdam Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| |
Collapse
|
13
|
Aartsma-Rus A, Hegde M, Ben-Omran T, Buccella F, Ferlini A, Gallano P, Howell RR, Leturcq F, Martin AS, Potulska-Chromik A, Saute JA, Schmidt WM, Sejersen T, Tuffery-Giraud S, Uyguner ZO, Witcomb LA, Yau S, Nelson SF. Evidence-Based Consensus and Systematic Review on Reducing the Time to Diagnosis of Duchenne Muscular Dystrophy. J Pediatr 2019; 204:305-313.e14. [PMID: 30579468 DOI: 10.1016/j.jpeds.2018.10.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 09/27/2018] [Accepted: 10/24/2018] [Indexed: 12/11/2022]
Affiliation(s)
- Annemieke Aartsma-Rus
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Madhuri Hegde
- Department of Human Genetics, Emory University School of Medicine/School of Biological Sciences, Georgia Institute of Technology/Perkin Elmer Genetics, Atlanta, GA
| | - Tawfeg Ben-Omran
- Clinical and Metabolic Genetics, Department of Pediatrics, Hamad Medical Corporation, Doha, Qatar
| | | | | | - Pia Gallano
- U705 CIBERER, Servei de Genetica, Hospital de Sant Pau, Barcelona, Spain
| | | | - France Leturcq
- Department of Genetics and Molecular Biology, Hospitalier Universitaire Paris Centre, Cochin Hospital, Paris, France
| | - Ann S Martin
- Parent Project Muscular Dystrophy, Hackensack, NJ
| | | | - Jonas A Saute
- Medical Genetics and Neurology Services, Hospital de Clinicas de Porto Alegre/Internal Medicine Department, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Wolfgang M Schmidt
- Neuromuscular Research Department, Medical University of Vienna, Vienna, Austria
| | - Thomas Sejersen
- Department of Women's and Children's Health, Karolinska Institute/Astrid Lindgrens Barnsjukhus, Karolinska University Hospital, Stockholm, Sweden
| | - Sylvie Tuffery-Giraud
- Laboratory of Rare Genetic Diseases (LGMR), University of Montpellier, Montpellier, France
| | - Zehra Oya Uyguner
- Department of Medical Genetics, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey
| | | | - Shu Yau
- Viapath Analytics, Guy's Hospital, London, United Kingdom
| | - Stanley F Nelson
- Department of Human Genetics, University of California, Los Angeles, CA.
| |
Collapse
|
14
|
Deep intronic variants introduce DMD pseudoexon in patient with muscular dystrophy. Neuromuscul Disord 2017; 27:631-634. [DOI: 10.1016/j.nmd.2017.04.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 03/27/2017] [Accepted: 04/05/2017] [Indexed: 12/27/2022]
|
15
|
Normal and altered pre-mRNA processing in the DMD gene. Hum Genet 2017; 136:1155-1172. [DOI: 10.1007/s00439-017-1820-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 06/02/2017] [Indexed: 12/11/2022]
|
16
|
Deep intronic mutations and human disease. Hum Genet 2017; 136:1093-1111. [DOI: 10.1007/s00439-017-1809-4] [Citation(s) in RCA: 178] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 05/05/2017] [Indexed: 12/22/2022]
|
17
|
Wang L, Chen M, He R, Sun Y, Yang J, Xiao L, Cao J, Zhang H, Zhang C. Serum Creatinine Distinguishes Duchenne Muscular Dystrophy from Becker Muscular Dystrophy in Patients Aged ≤3 Years: A Retrospective Study. Front Neurol 2017; 8:196. [PMID: 28533764 PMCID: PMC5421192 DOI: 10.3389/fneur.2017.00196] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 04/21/2017] [Indexed: 11/13/2022] Open
Abstract
Here, we investigated correlations between serum creatinine (SCRN) levels and clinical phenotypes of dystrophinopathy in young patients. Sixty-eight patients with dystrophinopathy at the Neuromuscular Clinic, The First Affiliated Hospital, Sun Yat-sen University, were selected for this study. The diagnosis of dystrophinopathy was based on clinical manifestation, biochemical changes, and molecular analysis. Some patients underwent muscle biopsies; SCRN levels were tested when patients were ≤3 years old, and reading frame changes were analyzed. Each patient was followed up, and motor function and clinical phenotype were assessed when the same patients were ≥4 years old. Our findings indicated that in young patients, lower SCRN levels were associated with increased disease severity (p < 0.01) and that SCRN levels were the highest in patients exhibiting mild Becker muscular dystrophy (BMD) (p < 0.001) and the lowest in patients with Duchenne muscular dystrophy (DMD) (p < 0.01) and were significantly higher in patients carrying in-frame mutations than in patients carrying out-of-frame mutations (p < 0.001). SCRN level cutoff values for identifying mild BMD [18 µmol/L; area under the curve (AUC): 0.947; p < 0.001] and DMD (17 µmol/L; AUC: 0.837; p < 0.001) were established. These results suggest that SCRN might be a valuable biomarker for distinguishing DMD from BMD in patients aged ≤3 years and could assist in the selection of appropriate treatment strategies.
Collapse
Affiliation(s)
- Liang Wang
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Menglong Chen
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Ruojie He
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Yiming Sun
- Department of Health Care, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Juan Yang
- Department of Neurology, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Lulu Xiao
- The Department of Tissue Typing Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Jiqing Cao
- Department of Neurology, Wuhan Central Hospital, Wuhan, Hubei, China
| | - Huili Zhang
- Department of Neurology, Guangzhou First People's Hospital, Guangzhou, Guangdong, China
| | - Cheng Zhang
- Department of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong, China
| |
Collapse
|
18
|
Detailed molecular characterization of a novel IDS exonic mutation associated with multiple pseudoexon activation. J Mol Med (Berl) 2016; 95:299-309. [PMID: 27837218 DOI: 10.1007/s00109-016-1484-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 10/12/2016] [Accepted: 11/01/2016] [Indexed: 12/21/2022]
Abstract
Mutations affecting splicing underlie the development of many human genetic diseases, but rather rarely through mechanisms of pseudoexon activation. Here, we describe a novel c.1092T>A mutation in the iduronate-2-sulfatase (IDS) gene detected in a patient with significantly decreased IDS activity and a clinical diagnosis of mild mucopolysaccharidosis II form. The mutation created an exonic de novo acceptor splice site and resulted in a complex splicing pattern with multiple pseudoexon activation in the patient's fibroblasts. Using an extensive series of minigene splicing experiments, we showed that the competition itself between the de novo and authentic splice site led to the bypass of the authentic one. This event then resulted in activation of several cryptic acceptor and donor sites in the upstream intron. As this was an unexpected and previously unreported mechanism of aberrant pseudoexon inclusion, we systematically analysed and disproved that the patient's mutation induced any relevant change in surrounding splicing regulatory elements. Interestingly, all pseudoexons included in the mature transcripts overlapped with the IDS alternative terminal exon 7b suggesting that this sequence represents a key element in the IDS pre-mRNA architecture. These findings extend the spectrum of mechanisms enabling pseudoexon activation and underscore the complexity of mutation-induced splicing aberrations. KEY MESSAGE Novel exonic IDS gene mutation leads to a complex splicing pattern. Mutation activates multiple pseudoexons through a previously unreported mechanism. Multiple cryptic splice site (ss) activation results from a bypass of authentic ss. Authentic ss bypass is due to a competition between de novo and authentic ss.
Collapse
|
19
|
Fletcher S, Bellgard MI, Price L, Akkari AP, Wilton SD. Translational development of splice-modifying antisense oligomers. Expert Opin Biol Ther 2016; 17:15-30. [PMID: 27805416 DOI: 10.1080/14712598.2017.1250880] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
INTRODUCTION Antisense nucleic acid analogues can interact with pre-mRNA motifs and influence exon or splice site selection and thereby alter gene expression. Design of antisense molecules to target specific motifs can result in either exon exclusion or exon inclusion during splicing. Novel drugs exploiting the antisense concept are targeting rare, life-limiting diseases; however, the potential exists to treat a wide range of conditions by antisense-mediated splice intervention. Areas covered: In this review, the authors discuss the clinical translation of novel molecular therapeutics to address the fatal neuromuscular disorders Duchenne muscular dystrophy and spinal muscular atrophy. The review also highlights difficulties posed by issues pertaining to restricted participant numbers, variable phenotype and disease progression, and the identification and validation of study endpoints. Expert opinion: Translation of novel therapeutics for Duchenne muscular dystrophy and spinal muscular atrophy has been greatly advanced by multidisciplinary research, academic-industry partnerships and in particular, the engagement and support of the patient community. Sponsors, supporters and regulators are cooperating to deliver new drugs and identify and define meaningful outcome measures. Non-conventional and adaptive trial design could be particularly suited to clinical evaluation of novel therapeutics and strategies to treat serious, rare diseases that may be problematic to study using more conventional clinical trial structures.
Collapse
Affiliation(s)
- S Fletcher
- a Centre for Neuromuscular and Neurological Disorders , University of Western Australia , Nedlands , Western Australia , Australia.,b Western Australian Neuroscience Research Institute , Nedlands , Western Australia , Australia.,c Centre for Comparative Genomics , Murdoch University , Western Australia , Australia
| | - M I Bellgard
- b Western Australian Neuroscience Research Institute , Nedlands , Western Australia , Australia.,c Centre for Comparative Genomics , Murdoch University , Western Australia , Australia
| | - L Price
- a Centre for Neuromuscular and Neurological Disorders , University of Western Australia , Nedlands , Western Australia , Australia.,b Western Australian Neuroscience Research Institute , Nedlands , Western Australia , Australia.,c Centre for Comparative Genomics , Murdoch University , Western Australia , Australia
| | - A P Akkari
- b Western Australian Neuroscience Research Institute , Nedlands , Western Australia , Australia.,c Centre for Comparative Genomics , Murdoch University , Western Australia , Australia.,d Shiraz Pharmaceuticals, Inc , Chapel Hill , NC , USA
| | - S D Wilton
- a Centre for Neuromuscular and Neurological Disorders , University of Western Australia , Nedlands , Western Australia , Australia.,b Western Australian Neuroscience Research Institute , Nedlands , Western Australia , Australia.,c Centre for Comparative Genomics , Murdoch University , Western Australia , Australia
| |
Collapse
|
20
|
Abstract
Recent improvements in experimental and computational techniques that are used to study the transcriptome have enabled an unprecedented view of RNA processing, revealing many previously unknown non-canonical splicing events. This includes cryptic events located far from the currently annotated exons and unconventional splicing mechanisms that have important roles in regulating gene expression. These non-canonical splicing events are a major source of newly emerging transcripts during evolution, especially when they involve sequences derived from transposable elements. They are therefore under precise regulation and quality control, which minimizes their potential to disrupt gene expression. We explain how non-canonical splicing can lead to aberrant transcripts that cause many diseases, and also how it can be exploited for new therapeutic strategies.
Collapse
|
21
|
Toh ZYC, Thandar Aung-Htut M, Pinniger G, Adams AM, Krishnaswarmy S, Wong BL, Fletcher S, Wilton SD. Deletion of Dystrophin In-Frame Exon 5 Leads to a Severe Phenotype: Guidance for Exon Skipping Strategies. PLoS One 2016; 11:e0145620. [PMID: 26745801 PMCID: PMC4706350 DOI: 10.1371/journal.pone.0145620] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Accepted: 12/07/2015] [Indexed: 12/03/2022] Open
Abstract
Duchenne and Becker muscular dystrophy severity depends upon the nature and location of the DMD gene lesion and generally correlates with the dystrophin open reading frame. However, there are striking exceptions where an in-frame genomic deletion leads to severe pathology or protein-truncating mutations (nonsense or frame-shifting indels) manifest as mild disease. Exceptions to the dystrophin reading frame rule are usually resolved after molecular diagnosis on muscle RNA. We report a moderate/severe Becker muscular dystrophy patient with an in-frame genomic deletion of DMD exon 5. This mutation has been reported by others as resulting in Duchenne or Intermediate muscular dystrophy, and the loss of this in-frame exon in one patient led to multiple splicing events, including omission of exon 6, that disrupts the open reading frame and is consistent with a severe phenotype. The patient described has a deletion of dystrophin exon 5 that does not compromise recognition of exon 6, and although the deletion does not disrupt the reading frame, his clinical presentation is more severe than would be expected for classical Becker muscular dystrophy. We suggest that the dystrophin isoform lacking the actin-binding sequence encoded by exon 5 is compromised, reflected by the phenotype resulting from induction of this dystrophin isoform in mouse muscle in vivo. Hence, exon skipping to address DMD-causing mutations within DMD exon 5 may not yield an isoform that confers marked clinical benefit. Additional studies will be required to determine whether multi-exon skipping strategies could yield more functional dystrophin isoforms, since some BMD patients with larger in-frame deletions in this region have been reported with mild phenotypes.
Collapse
Affiliation(s)
- Zhi Yon Charles Toh
- Western Australian Neuroscience Research Institute, Perth, Australia
- University of Western Australia, Perth, Australia
| | | | - Gavin Pinniger
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Perth, Australia
| | - Abbie M. Adams
- Western Australian Neuroscience Research Institute, Perth, Australia
- University of Western Australia, Perth, Australia
- Centre for Comparative Genomics, Murdoch University, Perth, Australia
| | | | - Brenda L. Wong
- Department of Paediatrics, Department of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, United States of America
| | - Sue Fletcher
- Western Australian Neuroscience Research Institute, Perth, Australia
- University of Western Australia, Perth, Australia
- Centre for Comparative Genomics, Murdoch University, Perth, Australia
| | - Steve D. Wilton
- Western Australian Neuroscience Research Institute, Perth, Australia
- University of Western Australia, Perth, Australia
- Centre for Comparative Genomics, Murdoch University, Perth, Australia
- * E-mail:
| |
Collapse
|