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Ma Y, Schwager (Karpukhina) A, Dib C, Gautier C, Hermine O, Allemand E, Vassetzky YS. Exchange of subtelomeric regions between chromosomes 4q and 10q reverts the FSHD genotype and phenotype. SCIENCE ADVANCES 2024; 10:eadl1922. [PMID: 38691604 PMCID: PMC11062572 DOI: 10.1126/sciadv.adl1922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 03/26/2024] [Indexed: 05/03/2024]
Abstract
The most common form of facioscapulohumeral dystrophy (FSHD1) is caused by a partial loss of the D4Z4 macrosatellite repeat array in the subtelomeric region of chromosome 4. Patients with FSHD1 typically carry 1 to 10 D4Z4 repeats, whereas nonaffected individuals have 11 to 150 repeats. The ~150-kilobyte subtelomeric region of the chromosome 10q exhibits a ~99% sequence identity to the 4q, including the D4Z4 array. Nevertheless, contractions of the chr10 array do not cause FSHD or any known disease, as in most people D4Z4 array on chr10 is flanked by the nonfunctional polyadenylation signal, not permitting the DUX4 expression. Here, we attempted to correct the FSHD genotype by a CRISPR-Cas9-induced exchange of the chr4 and chr10 subtelomeric regions. We demonstrated that the induced t(4;10) translocation can generate recombinant genotypes translated into improved FSHD phenotype. FSHD myoblasts with the t(4;10) exhibited reduced expression of the DUX4 targets, restored PAX7 target expression, reduced sensitivity to oxidative stress, and improved differentiation capacity.
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Affiliation(s)
- Yinxing Ma
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, Villejuif, France
- Center for Single-Cell Omics, School of Public Health, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Anna Schwager (Karpukhina)
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, Villejuif, France
- Koltzov Institute of Developmental Biology, Moscow, Russia
| | - Carla Dib
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, Villejuif, France
| | - Candice Gautier
- Université de Paris Cité, Institut Imagine, Inserm U1163, Paris, France
| | - Olivier Hermine
- Université de Paris Cité, Institut Imagine, Inserm U1163, Paris, France
- Department of Hematology, Hôpital Necker Enfants Malades, AP-HP, Faculté de Médecine Paris Descartes, Paris, France
| | - Eric Allemand
- Université de Paris Cité, Institut Imagine, Inserm U1163, Paris, France
| | - Yegor S. Vassetzky
- CNRS UMR9018, Université Paris-Saclay, Institut Gustave Roussy, Villejuif, France
- Koltzov Institute of Developmental Biology, Moscow, Russia
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2
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Lemmers RJLF, Butterfield R, van der Vliet PJ, de Bleecker JL, van der Pol L, Dunn DM, Erasmus CE, D'Hooghe M, Verhoeven K, Balog J, Bigot A, van Engelen B, Statland J, Bugiardini E, van der Stoep N, Evangelista T, Marini-Bettolo C, van den Bergh P, Tawil R, Voermans NC, Vissing J, Weiss RB, van der Maarel SM. Autosomal dominant in cis D4Z4 repeat array duplication alleles in facioscapulohumeral dystrophy. Brain 2024; 147:414-426. [PMID: 37703328 PMCID: PMC10834250 DOI: 10.1093/brain/awad312] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/26/2023] [Accepted: 08/10/2023] [Indexed: 09/15/2023] Open
Abstract
Facioscapulohumeral dystrophy (FSHD) has a unique genetic aetiology resulting in partial chromatin relaxation of the D4Z4 macrosatellite repeat array on 4qter. This D4Z4 chromatin relaxation facilitates inappropriate expression of the transcription factor DUX4 in skeletal muscle. DUX4 is encoded by a retrogene that is embedded within the distal region of the D4Z4 repeat array. In the European population, the D4Z4 repeat array is usually organized in a single array that ranges between 8 and 100 units. D4Z4 chromatin relaxation and DUX4 derepression in FSHD is most often caused by repeat array contraction to 1-10 units (FSHD1) or by a digenic mechanism requiring pathogenic variants in a D4Z4 chromatin repressor like SMCHD1, combined with a repeat array between 8 and 20 units (FSHD2). With a prevalence of 1.5% in the European population, in cis duplications of the D4Z4 repeat array, where two adjacent D4Z4 arrays are interrupted by a spacer sequence, are relatively common but their relationship to FSHD is not well understood. In cis duplication alleles were shown to be pathogenic in FSHD2 patients; however, there is inconsistent evidence for the necessity of an SMCHD1 mutation for disease development. To explore the pathogenic nature of these alleles we compared in cis duplication alleles in FSHD patients with or without pathogenic SMCHD1 variant. For both groups we showed duplication-allele-specific DUX4 expression. We studied these alleles in detail using pulsed-field gel electrophoresis-based Southern blotting and molecular combing, emphasizing the challenges in the characterization of these rearrangements. Nanopore sequencing was instrumental to study the composition and methylation of the duplicated D4Z4 repeat arrays and to identify the breakpoints and the spacer sequence between the arrays. By comparing the composition of the D4Z4 repeat array of in cis duplication alleles in both groups, we found that specific combinations of proximal and distal repeat array sizes determine their pathogenicity. Supported by our algorithm to predict pathogenicity, diagnostic laboratories should now be furnished to accurately interpret these in cis D4Z4 repeat array duplications, alleles that can easily be missed in routine settings.
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Affiliation(s)
- Richard J L F Lemmers
- Department of Human Genetics, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
| | | | - Patrick J van der Vliet
- Department of Human Genetics, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
| | | | - Ludo van der Pol
- University Medical Center Utrecht, 3584 EA, Utrecht, The Netherlands
| | - Diane M Dunn
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Corrie E Erasmus
- Neuromuscular Centre Nijmegen, Radboud University Nijmegen Medical Centre, 6525 GA, Nijmegen, The Netherlands
| | - Marc D'Hooghe
- Department of Neurology, Algemeen Ziekenhuis Sint-Jan, 8000, Brugge, Belgium
| | - Kristof Verhoeven
- Department of Neurology, Algemeen Ziekenhuis Sint-Jan, 8000, Brugge, Belgium
| | - Judit Balog
- Department of Human Genetics, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
| | - Anne Bigot
- Sorbonne Université, Inserm UMRS974, Institut de Myologie, Centre de Recherche en Myologie, F-75013 Paris, France
| | - Baziel van Engelen
- Neuromuscular Centre Nijmegen, Radboud University Nijmegen Medical Centre, 6525 GA, Nijmegen, The Netherlands
| | | | - Enrico Bugiardini
- National Hospital For Neurology and Neurosurgery, UCL Queen Square Institute of Neurology, London, WC1N 3BG, UK
| | - Nienke van der Stoep
- Department of Clinical Genetics, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
| | - Teresinha Evangelista
- Unité de Morphologie Neuromusculaire, Institut de Myologie, AP-HP, F-75013, Paris, France
| | - Chiara Marini-Bettolo
- The John Walton Muscular Dystrophy Research Centre, Faculty of Medical Sciences, Newcastle upon Tyne, NE1 3BZ, UK
| | | | - Rabi Tawil
- Department of Neurology, University of Rochester Medical Center, NY 14642, Rochester, USA
| | - Nicol C Voermans
- Neuromuscular Centre Nijmegen, Radboud University Nijmegen Medical Centre, 6525 GA, Nijmegen, The Netherlands
| | - John Vissing
- Department of Neurology, University of Copenhagen, DK-2100 Copenhagen, Denmark
| | - Robert B Weiss
- Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA
| | - Silvère M van der Maarel
- Department of Human Genetics, Leiden University Medical Center, 2300 RC, Leiden, The Netherlands
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3
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Guruju NM, Jump V, Lemmers R, Van Der Maarel S, Liu R, Nallamilli BR, Shenoy S, Chaubey A, Koppikar P, Rose R, Khadilkar S, Hegde M. Molecular Diagnosis of Facioscapulohumeral Muscular Dystrophy in Patients Clinically Suspected of FSHD Using Optical Genome Mapping. Neurol Genet 2023; 9:e200107. [PMID: 38021397 PMCID: PMC10664978 DOI: 10.1212/nxg.0000000000200107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 09/18/2023] [Indexed: 12/01/2023]
Abstract
Background and Objectives Facioscapulohumeral muscular dystrophy (FSHD) represents the third most common muscular dystrophy in the general population and is characterized by progressive and often asymmetric muscle weakness of the face, upper extremities, arms, lower leg, and hip girdle. In FSHD type 1, contraction of the number of D4Z4 repeats to 1-10 on the chromosome 4-permissive allele (4qA) results in abnormal epigenetic derepression of the DUX4 gene in skeletal muscle. In FSHD type 2, epigenetic derepression of the DUX4 gene on the permissive allele (4qA) with normal-sized D4Z4 repeats (mostly 8-20) is caused by heterozygous pathogenic variants in chromatin modifier genes such as SMCHD1, DNMT3B, or LRIF1. We present validation of the optical genome mapping (OGM) platform for accurate mapping of the D4Z4 repeat size, followed by diagnostic testing of 547 cases with a suspected clinical diagnosis of FSHD and next-generation sequencing (NGS) of the SMCHD1 gene to identify cases with FSHD2. Methods OGM with Bionano Genomics Saphyr and EnFocus FSHD analysis software was used to identify FSHD haplotypes and D4Z4 repeat number and compared with the gold standard of Southern blot-based diagnosis. A custom Agilent SureSelect enrichment kit was used to enrich SMCHD1, followed by NGS on an Illumina system with 100-bp paired-end reads. Copy number variants were assessed using NxClinical software. Results We performed OGM for the diagnosis of FSHD in 547 patients suspected of FSHD between December 2019 and December 2022, including 301 male (55%) and 246 female patients (45%). Overall, 308 of the referred patients were positive for D4Z4 contraction on a permissive haplotype, resulting in a diagnosis of FSHD1. A total of 252 of 547 patients were referred for concurrent testing for FSHD1 and FSHD2. This resulted in the identification of FSHD2 in 9/252 (3.6%) patients. In our FSHD2 cohort, the 4qA allele size ranged from 8 to 18 repeats. Among FSHD1-positive cases, 2 patients had biallelic contraction and 4 patients had homozygous contraction and showed early onset of clinical features. Nine of the 308 patients (3%) positive for 4qA contraction had mosaic 4q alleles with contraction on at least one 4qA allele. The overall diagnostic yield in our cohort was 58%. Discussion A combination of OGM to identify the FSHD haplotype and D4Z4 repeat number and NGS to identify sequence and copy number variants in the SMCHD1 gene is a practical and cost-effective option with increased precision for accurate diagnosis of FSHD types 1 and 2.
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Affiliation(s)
- Naga M Guruju
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Vanessa Jump
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Richard Lemmers
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Silvere Van Der Maarel
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Ruby Liu
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Babi R Nallamilli
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Suresh Shenoy
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Alka Chaubey
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Pratik Koppikar
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Rajiv Rose
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Satish Khadilkar
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
| | - Madhuri Hegde
- From the Revvity Omics (N.M.G., V.J., Ruby Liu, B.R.N., S.S., R.R., M.H.), Pittsburgh, PA; Leiden University Medical Centre (Richard Lemmers, S.V.D.M.), Netherlands; Bionano Genomics (A.C.), San Diego, CA; UT Dallas (P.K.), TX; Bombay Hospital (S.K.), Mumbai, India
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4
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Kovanda A, Lovrečić L, Rudolf G, Babic Bozovic I, Jaklič H, Leonardis L, Peterlin B. Evaluation of Optical Genome Mapping in Clinical Genetic Testing of Facioscapulohumeral Muscular Dystrophy. Genes (Basel) 2023; 14:2166. [PMID: 38136988 PMCID: PMC10743191 DOI: 10.3390/genes14122166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 11/24/2023] [Accepted: 11/27/2023] [Indexed: 12/24/2023] Open
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is the third most common hereditary muscular dystrophy, caused by the contraction of the D4Z4 repeats on the permissive 4qA haplotype on chromosome 4, resulting in the faulty expression of the DUX4 gene. Traditional diagnostics are based on Southern blotting, a time- and effort-intensive method that can be affected by single nucleotide variants (SNV) and copy number variants (CNV), as well as by the similarity of the D4Z4 repeats located on chromosome 10. We aimed to evaluate optical genome mapping (OGM) as an alternative molecular diagnostic method for the detection of FSHD. We first performed optical genome mapping with EnFocus™ FSHD analysis using DLE-1 labeling and the Saphyr instrument in patients with inconclusive diagnostic Southern blot results, negative FSHD2 results, and clinically evident FSHD. Second, we performed OGM in parallel with the classical Southern blot analysis for our prospectively collected new FSHD cases. Finally, panel exome sequencing was performed to confirm the presence of FSHD2. In two patients with diagnostically inconclusive Southern blot results, OGM was able to identify shortened D4Z4 repeats on the permissive 4qA alleles, consistent with the clinical presentation. The results of the prospectively collected patients tested in parallel using Southern blotting and OGM showed full concordance, indicating that OGM is a useful alternative to the classical Southern blotting method for detecting FSHD1. In a patient showing clinical FSHD but no shortened D4Z4 repeats in the 4qA allele using OGM or Southern blotting, a likely pathogenic variant in SMCHD1 was detected using exome sequencing, confirming FSHD2. OGM and panel exome sequencing can be used consecutively to detect FSHD2.
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Affiliation(s)
- Anja Kovanda
- Clinical Institute of Genomic Medicine, University Medical Center, 1000 Ljubljana, Slovenia; (A.K.)
- Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Luca Lovrečić
- Clinical Institute of Genomic Medicine, University Medical Center, 1000 Ljubljana, Slovenia; (A.K.)
- Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Gorazd Rudolf
- Clinical Institute of Genomic Medicine, University Medical Center, 1000 Ljubljana, Slovenia; (A.K.)
- Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Ivana Babic Bozovic
- Clinical Institute of Genomic Medicine, University Medical Center, 1000 Ljubljana, Slovenia; (A.K.)
| | - Helena Jaklič
- Clinical Institute of Genomic Medicine, University Medical Center, 1000 Ljubljana, Slovenia; (A.K.)
| | - Lea Leonardis
- Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
- Institute of Clinical Neurophysiology, University Medical Center Ljubljana, 1000 Ljubljana, Slovenia
| | - Borut Peterlin
- Clinical Institute of Genomic Medicine, University Medical Center, 1000 Ljubljana, Slovenia; (A.K.)
- Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
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5
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Butterfield RJ, Dunn DM, Duval B, Moldt S, Weiss RB. Deciphering D4Z4 CpG methylation gradients in fascioscapulohumeral muscular dystrophy using nanopore sequencing. Genome Res 2023; 33:1439-1454. [PMID: 37798116 PMCID: PMC10620044 DOI: 10.1101/gr.277871.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Accepted: 08/02/2023] [Indexed: 10/07/2023]
Abstract
Fascioscapulohumeral muscular dystrophy (FSHD) is caused by a unique genetic mechanism that relies on contraction and hypomethylation of the D4Z4 macrosatellite array on the Chromosome 4q telomere allowing ectopic expression of the DUX4 gene in skeletal muscle. Genetic analysis is difficult because of the large size and repetitive nature of the array, a nearly identical array on the 10q telomere, and the presence of divergent D4Z4 arrays scattered throughout the genome. Here, we combine nanopore long-read sequencing with Cas9-targeted enrichment of 4q and 10q D4Z4 arrays for comprehensive genetic analysis including determination of the length of the 4q and 10q D4Z4 arrays with base-pair resolution. In the same assay, we differentiate 4q from 10q telomeric sequences, determine A/B haplotype, identify paralogous D4Z4 sequences elsewhere in the genome, and estimate methylation for all CpGs in the array. Asymmetric, length-dependent methylation gradients were observed in the 4q and 10q D4Z4 arrays that reach a hypermethylation point at approximately 10 D4Z4 repeat units, consistent with the known threshold of pathogenic D4Z4 contractions. High resolution analysis of individual D4Z4 repeat methylation revealed areas of low methylation near the CTCF/insulator region and areas of high methylation immediately preceding the DUX4 transcriptional start site. Within the DUX4 exons, we observed a waxing/waning methylation pattern with a 180-nucleotide periodicity, consistent with phased nucleosomes. Targeted nanopore sequencing complements recently developed molecular combing and optical mapping approaches to genetic analysis for FSHD by adding precision of the length measurement, base-pair resolution sequencing, and quantitative methylation analysis.
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Affiliation(s)
- Russell J Butterfield
- Department of Pediatrics, University of Utah, Salt Lake City, Utah 84108, USA;
- Department of Neurology, University of Utah, Salt Lake City, Utah 84132, USA
| | - Diane M Dunn
- Department of Human Genetics, University of Utah, Salt Lake City, Utah 84112, USA
| | - Brett Duval
- Department of Human Genetics, University of Utah, Salt Lake City, Utah 84112, USA
| | - Sarah Moldt
- Department of Pediatrics, University of Utah, Salt Lake City, Utah 84108, USA
| | - Robert B Weiss
- Department of Human Genetics, University of Utah, Salt Lake City, Utah 84112, USA
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6
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Duranti E, Villa C. Influence of DUX4 Expression in Facioscapulohumeral Muscular Dystrophy and Possible Treatments. Int J Mol Sci 2023; 24:ijms24119503. [PMID: 37298453 DOI: 10.3390/ijms24119503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/23/2023] [Accepted: 05/29/2023] [Indexed: 06/12/2023] Open
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) represents the third most common form of muscular dystrophy and is characterized by muscle weakness and atrophy. FSHD is caused by the altered expression of the transcription factor double homeobox 4 (DUX4), which is involved in several significantly altered pathways required for myogenesis and muscle regeneration. While DUX4 is normally silenced in the majority of somatic tissues in healthy individuals, its epigenetic de-repression has been linked to FSHD, resulting in DUX4 aberrant expression and cytotoxicity in skeletal muscle cells. Understanding how DUX4 is regulated and functions could provide useful information not only to further understand FSHD pathogenesis, but also to develop therapeutic approaches for this disorder. Therefore, this review discusses the role of DUX4 in FSHD by examining the possible molecular mechanisms underlying the disease as well as novel pharmacological strategies targeting DUX4 aberrant expression.
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Affiliation(s)
- Elisa Duranti
- School of Medicine and Surgery, University of Milano-Bicocca, 20900 Monza, Italy
| | - Chiara Villa
- School of Medicine and Surgery, University of Milano-Bicocca, 20900 Monza, Italy
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7
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Claus C, Slavin M, Ansseau E, Lancelot C, Bah K, Lassche S, Fiévet M, Greco A, Tomaiuolo S, Tassin A, Dudome V, Kusters B, Declèves AE, Laoudj-Chenivesse D, van Engelen BGM, Nonclercq D, Belayew A, Kalisman N, Coppée F. The double homeodomain protein DUX4c is associated with regenerating muscle fibers and RNA-binding proteins. Skelet Muscle 2023; 13:5. [PMID: 36882853 PMCID: PMC9990282 DOI: 10.1186/s13395-022-00310-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 11/30/2022] [Indexed: 03/09/2023] Open
Abstract
BACKGROUND We have previously demonstrated that double homeobox 4 centromeric (DUX4C) encoded for a functional DUX4c protein upregulated in dystrophic skeletal muscles. Based on gain- and loss-of-function studies we have proposed DUX4c involvement in muscle regeneration. Here, we provide further evidence for such a role in skeletal muscles from patients affected with facioscapulohumeral muscular dystrophy (FSHD). METHODS DUX4c was studied at RNA and protein levels in FSHD muscle cell cultures and biopsies. Its protein partners were co-purified and identified by mass spectrometry. Endogenous DUX4c was detected in FSHD muscle sections with either its partners or regeneration markers using co-immunofluorescence or in situ proximity ligation assay. RESULTS We identified new alternatively spliced DUX4C transcripts and confirmed DUX4c immunodetection in rare FSHD muscle cells in primary culture. DUX4c was detected in nuclei, cytoplasm or at cell-cell contacts between myocytes and interacted sporadically with specific RNA-binding proteins involved, a.o., in muscle differentiation, repair, and mass maintenance. In FSHD muscle sections, DUX4c was found in fibers with unusual shape or central/delocalized nuclei (a regeneration feature) staining for developmental myosin heavy chain, MYOD or presenting intense desmin labeling. Some couples of myocytes/fibers locally exhibited peripheral DUX4c-positive areas that were very close to each other, but in distinct cells. MYOD or intense desmin staining at these locations suggested an imminent muscle cell fusion. We further demonstrated DUX4c interaction with its major protein partner, C1qBP, inside myocytes/myofibers that presented features of regeneration. On adjacent muscle sections, we could unexpectedly detect DUX4 (the FSHD causal protein) and its interaction with C1qBP in fusing myocytes/fibers. CONCLUSIONS DUX4c upregulation in FSHD muscles suggests it contributes not only to the pathology but also, based on its protein partners and specific markers, to attempts at muscle regeneration. The presence of both DUX4 and DUX4c in regenerating FSHD muscle cells suggests DUX4 could compete with normal DUX4c functions, thus explaining why skeletal muscle is particularly sensitive to DUX4 toxicity. Caution should be exerted with therapeutic agents aiming for DUX4 suppression because they might also repress the highly similar DUX4c and interfere with its physiological role.
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Affiliation(s)
- Clothilde Claus
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Moriya Slavin
- Department of Biological Chemistry, the Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Eugénie Ansseau
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Céline Lancelot
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Karimatou Bah
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Saskia Lassche
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA, Nijmegen, The Netherlands.,Department of Neurology, Zuyderland Medical Center, Heerlen, the Netherlands
| | - Manon Fiévet
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Anna Greco
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA, Nijmegen, The Netherlands
| | - Sara Tomaiuolo
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Alexandra Tassin
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium.,Laboratory of Respiratory Physiology and Rehabilitation, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Virginie Dudome
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Benno Kusters
- Department of Pathology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA, Nijmegen, The Netherlands
| | - Anne-Emilie Declèves
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | | | - Baziel G M van Engelen
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525 GA, Nijmegen, The Netherlands
| | - Denis Nonclercq
- Laboratory of Histology, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Alexandra Belayew
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium
| | - Nir Kalisman
- Department of Biological Chemistry, the Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
| | - Frédérique Coppée
- Laboratory of Metabolic and Molecular Biochemistry, Research Institute for Health Sciences and Technology, University of Mons, 6, Avenue du Champs de Mars, B-7000, Mons, Belgium.
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8
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Tihaya MS, Mul K, Balog J, de Greef JC, Tapscott SJ, Tawil R, Statland JM, van der Maarel SM. Facioscapulohumeral muscular dystrophy: the road to targeted therapies. Nat Rev Neurol 2023; 19:91-108. [PMID: 36627512 DOI: 10.1038/s41582-022-00762-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/07/2022] [Indexed: 01/11/2023]
Abstract
Advances in the molecular understanding of facioscapulohumeral muscular dystrophy (FSHD) have revealed that FSHD results from epigenetic de-repression of the DUX4 gene in skeletal muscle, which encodes a transcription factor that is active in early embryonic development but is normally silenced in almost all somatic tissues. These advances also led to the identification of targets for disease-altering therapies for FSHD, as well as an improved understanding of the molecular mechanism of the disease and factors that influence its progression. Together, these developments led the FSHD research community to shift its focus towards the development of disease-modifying treatments for FSHD. This Review presents advances in the molecular and clinical understanding of FSHD, discusses the potential targeted therapies that are currently being explored, some of which are already in clinical trials, and describes progress in the development of FSHD-specific outcome measures and assessment tools for use in future clinical trials.
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Affiliation(s)
- Mara S Tihaya
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Karlien Mul
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Judit Balog
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Jessica C de Greef
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Stephen J Tapscott
- Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Rabi Tawil
- Department of Neurology, University of Rochester Medical Center, Rochester, NY, USA
| | - Jeffrey M Statland
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS, USA
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9
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Mariot V, Dumonceaux J. Gene Editing to Tackle Facioscapulohumeral Muscular Dystrophy. Front Genome Ed 2022; 4:937879. [PMID: 35910413 PMCID: PMC9334676 DOI: 10.3389/fgeed.2022.937879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 06/20/2022] [Indexed: 11/13/2022] Open
Abstract
Facioscapulohumeral dystrophy (FSHD) is a skeletal muscle disease caused by the aberrant expression of the DUX4 gene in the muscle tissue. To date, different therapeutic approaches have been proposed, targeting DUX4 at the DNA, RNA or protein levels. The recent development of the clustered regularly interspaced short-palindromic repeat (CRISPR) based technology opened new avenues of research, and FSHD is no exception. For the first time, a cure for genetic muscular diseases can be considered. Here, we describe CRISPR-based strategies that are currently being investigated for FSHD. The different approaches include the epigenome editing targeting the DUX4 gene and its promoter, gene editing targeting the polyadenylation of DUX4 using TALEN, CRISPR/cas9 or adenine base editing and the CRISPR-Cas9 genome editing for SMCHD1. We also discuss challenges facing the development of these gene editing based therapeutics.
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10
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Beermann ML, Homma S, Miller JB. Proximity ligation assay to detect DUX4 protein in FSHD1 muscle: a pilot study. BMC Res Notes 2022; 15:163. [PMID: 35538497 PMCID: PMC9092897 DOI: 10.1186/s13104-022-06054-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 04/26/2022] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVE Aberrant expression in skeletal muscle of DUX4, a double homeobox transcription factor, underlies pathogenesis in facioscapulohumeral muscular dystrophy (FSHD). Although previous studies of FSHD muscle biopsies detected mRNAs encoding DUX4 and its target genes, no studies had reported detection of DUX4 protein. Our objective was to develop a proximity ligation assay (PLA) for DUX4 and to determine if this assay could detect DUX4 protein in FSHD muscle sections. RESULTS We developed a PLA protocol using two DUX4 antibodies previously reported by Stephen Tapscott's group: P2G4, a mouse mAb specific for an epitope in the N-terminal region, and E5-5, a rabbit mAb specific for an epitope in the C-terminal region, in combination with commercial PLA secondary reagents. We validated the DUX4 PLA using cultured human myogenic cells in which DUX4 was ectopically expressed in a small fraction of nuclei. Using this two primary mAb PLA on an FSHD1 biceps biopsy, we observed nuclei with apparent DUX4 PLA signals associated with a small subset of myofibers (~ 0.05-0.1%). Though a limited pilot study, these results suggest that the two primary mAb PLA protocol could be useful for detecting DUX4 protein in FSHD muscle biopsies.
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Affiliation(s)
- Mary Lou Beermann
- Department of Neurology, Boston University School of Medicine, 700 Albany Street, Room 408K, Boston, MA, 02118, USA
| | - Sachiko Homma
- Department of Neurology, Boston University School of Medicine, 700 Albany Street, Room 408K, Boston, MA, 02118, USA
| | - Jeffrey Boone Miller
- Department of Neurology, Boston University School of Medicine, 700 Albany Street, Room 408K, Boston, MA, 02118, USA.
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11
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Masteika IF, Sathya A, Homma S, Miller BM, Boyce FM, Miller JB. Downstream events initiated by expression of FSHD-associated DUX4: Studies of nucleocytoplasmic transport, γH2AX accumulation, and Bax/Bak-dependence. Biol Open 2022; 11:274475. [PMID: 35191484 PMCID: PMC8890089 DOI: 10.1242/bio.059145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 01/12/2022] [Indexed: 12/15/2022] Open
Abstract
Abnormal expression in skeletal muscle of the double homeobox transcription factor DUX4 underlies pathogenesis in facioscapulohumeral muscular dystrophy (FSHD). Though multiple changes are known to be initiated by aberrant DUX4 expression, the downstream events initiated by DUX4 remain incompletely understood. In this study, we examined plausible downstream events initiated by DUX4. First, we found that nucleocytoplasmic protein export appeared to be decreased upon DUX4 expression as indicated by nuclear accumulation of a shuttle-GFP reporter. Second, building on studies from other labs, we showed that phospho(Ser139)-H2AX (γH2AX), an indicator of double-strand DNA breaks, accumulated both in human FSHD1 myotube nuclei upon endogenous DUX4 expression and in Bax-/-;Bak-/- (double knockout), SV40-immortalized mouse embryonic fibroblasts upon exogenous DUX4 expression. In contrast, DUX4-induced caspase 3/7 activation was prevented in Bax-/-;Bak-/- double knockout SV40-MEFs, but not by single knockouts of Bax, Bak, or Bid. Thus, aberrant DUX4 expression appeared to alter nucleocytoplasmic protein transport and generate double-strand DNA breaks in FSHD1 myotube nuclei, and the Bax/Bak pathway is required for DUX4-induced caspase activation but not γH2AX accumulation. These results add to our knowledge of downstream events induced by aberrant DUX4 expression and suggest possibilities for further mechanistic investigation.
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Affiliation(s)
- Isabel F Masteika
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Anvitha Sathya
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Sachiko Homma
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | - Bess M Miller
- Biological & Biomedical Sciences Program, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Frederick M Boyce
- Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Jeffrey Boone Miller
- Department of Neurology, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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12
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Bouwman LF, den Hamer B, van den Heuvel A, Franken M, Jackson M, Dwyer CA, Tapscott SJ, Rigo F, van der Maarel SM, de Greef JC. Systemic delivery of a DUX4-targeting antisense oligonucleotide to treat facioscapulohumeral muscular dystrophy. MOLECULAR THERAPY. NUCLEIC ACIDS 2021; 26:813-827. [PMID: 34729250 PMCID: PMC8526479 DOI: 10.1016/j.omtn.2021.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 09/17/2021] [Indexed: 01/16/2023]
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is one of the most prevalent skeletal muscle dystrophies. Skeletal muscle pathology in individuals with FSHD is caused by inappropriate expression of the transcription factor DUX4, which activates different myotoxic pathways. At the moment there is no molecular therapy that can delay or prevent skeletal muscle wasting in FSHD. In this study, a systemically delivered antisense oligonucleotide (ASO) targeting the DUX4 transcript was tested in vivo in ACTA1-MCM;FLExDUX4 mice that express DUX4 in skeletal muscles. We show that the DUX4 ASO was well tolerated and repressed the DUX4 transcript, DUX4 protein, and mouse DUX4 target gene expression in skeletal muscles. In addition, the DUX4 ASO alleviated the severity of skeletal muscle pathology and partially prevented the dysregulation of inflammatory and extracellular matrix genes. DUX4 ASO-treated ACTA1-MCM;FLExDUX4 mice performed better on a treadmill; however, the hanging grid and four-limb grip strength tests were not improved compared to control ASO-treated ACTA1-MCM;FLExDUX4 mice. This study shows that systemic delivery of ASOs targeting DUX4 is a promising therapeutic strategy for FSHD and strategies that further improve the ASO efficacy in skeletal muscle are warranted.
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Affiliation(s)
- Linde F. Bouwman
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands
| | - Bianca den Hamer
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands
| | - Anita van den Heuvel
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands
| | - Marnix Franken
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands
| | - Michaela Jackson
- Ionis Pharmaceuticals Inc., 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Chrissa A. Dwyer
- Ionis Pharmaceuticals Inc., 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Stephen J. Tapscott
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
- Department of Neurology, University of Washington, Seattle, WA 98105, USA
| | - Frank Rigo
- Ionis Pharmaceuticals Inc., 2855 Gazelle Court, Carlsbad, CA 92010, USA
| | - Silvère M. van der Maarel
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands
| | - Jessica C. de Greef
- Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands
- Corresponding author Jessica C. de Greef, Department of Human Genetics, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands.
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13
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Lemmers RJLF, Vliet PJ, Granado DSL, Stoep N, Buermans H, Schendel R, Schimmel J, Visser M, Coster R, Jeanpierre M, Laforet P, Upadhyaya M, Engelen B, Sacconi S, Tawil R, Voermans NC, Rogers M, van der Maarel SM. High resolution breakpoint junction mapping of proximally extended D4Z4 deletions in FSHD1 reveals evidence for a founder effect. Hum Mol Genet 2021; 31:748-760. [PMID: 34559225 DOI: 10.1093/hmg/ddab250] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 08/17/2021] [Accepted: 08/24/2021] [Indexed: 01/09/2023] Open
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is an inherited myopathy clinically characterized by weakness in the facial, shoulder girdle and upper arm muscles. FSHD is caused by chromatin relaxation of the D4Z4 macrosatellite repeat, mostly by a repeat contraction, facilitating ectopic expression of DUX4 in skeletal muscle. Genetic diagnosis for FSHD is generally based on the sizing and haplotyping of the D4Z4 repeat on chromosome 4 by Southern blotting, molecular combing or single-molecule optical mapping, which is usually straight forward but can be complicated by atypical rearrangements of the D4Z4 repeat. One of these rearrangements is a D4Z4 proximally-extended deletion (DPED) allele, where not only the D4Z4 repeat is partially deleted, but also sequences immediately proximal to the repeat are lost, which can impede accurate diagnosis in all genetic methods. Previously, we identified several DPED alleles in FSHD and estimated the size of the proximal deletions by a complex pulsed-field gel electrophoresis and Southern blot strategy. Here, using next generation sequencing, we have defined the breakpoint junctions of these DPED alleles at the base pair resolution in 12 FSHD families and 4 control individuals facilitating a PCR-based diagnosis of these DPED alleles. Our results show that half of the DPED alleles are derivates of an ancient founder allele. For some DPED alleles we found that genetic elements are deleted such as DUX4c, FRG2, DBE-T and myogenic enhancers necessitating re-evaluation of their role in FSHD pathogenesis.
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Affiliation(s)
- Richard J L F Lemmers
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Patrick J Vliet
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Nienke Stoep
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Henk Buermans
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Robin Schendel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Joost Schimmel
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Marianne Visser
- Academic Medical Center, Department of Neurology, Amsterdam, The Netherlands
| | - Rudy Coster
- Department of Pediatrics, Division of Pediatric Neurology, Ghent University Hospital, Ghent, Belgium
| | | | - Pascal Laforet
- Nord-Est/Ile-de-France Neuromuscular Reference Center, FHU PHENIX, Neurology Department, Raymond-Poincaré Hospital, Versailles Saint-Quentin-en-Yvelines - Paris Saclay University, Garches, France
| | - Meena Upadhyaya
- Department of Medical Genetics, Cardiff University, Cardif, UK
| | - Baziel Engelen
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University, The Netherlands
| | - Sabrina Sacconi
- Centre de référence des Maladies neuromusculaires, Nice University Hospital, Nice, France
| | - Rabi Tawil
- Department of Neurology, University of Rochester Medical Center, Rochester, NY, USA
| | - Nicol C Voermans
- Department of Neurology, Donders Institute for Brain, Cognition and Behaviour, Radboud University, The Netherlands
| | - Mark Rogers
- Department of Medical Genetics, Cardiff University, Cardif, UK
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14
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Adenine base editing of the DUX4 polyadenylation signal for targeted genetic therapy in facioscapulohumeral muscular dystrophy. MOLECULAR THERAPY. NUCLEIC ACIDS 2021; 25:342-354. [PMID: 34484861 PMCID: PMC8399085 DOI: 10.1016/j.omtn.2021.05.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 05/26/2021] [Indexed: 12/26/2022]
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is caused by chromatin relaxation of the D4Z4 repeat resulting in misexpression of the D4Z4-encoded DUX4 gene in skeletal muscle. One of the key genetic requirements for the stable production of full-length DUX4 mRNA in skeletal muscle is a functional polyadenylation signal (ATTAAA) in exon three of DUX4 that is used in somatic cells. Base editors hold great promise to treat DNA lesions underlying genetic diseases through their ability to carry out specific and rapid nucleotide mutagenesis even in postmitotic cells such as skeletal muscle. In this study, we present a simple and straightforward strategy for mutagenesis of the somatic DUX4 polyadenylation signal by adenine base editing in immortalized myoblasts derived from independent FSHD-affected individuals. We show that mutating this critical cis-regulatory element results in downregulation of DUX4 mRNA and its direct transcriptional target genes. Our findings identify the somatic DUX4 polyadenylation signal as a therapeutic target and represent the first step toward clinical application of the CRISPR-Cas9 base editing platform for FSHD gene therapy.
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15
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Banerji CRS, Zammit PS. Pathomechanisms and biomarkers in facioscapulohumeral muscular dystrophy: roles of DUX4 and PAX7. EMBO Mol Med 2021; 13:e13695. [PMID: 34151531 PMCID: PMC8350899 DOI: 10.15252/emmm.202013695] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 03/27/2021] [Accepted: 03/30/2021] [Indexed: 12/29/2022] Open
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is characterised by progressive skeletal muscle weakness and wasting. FSHD is linked to epigenetic derepression of the subtelomeric D4Z4 macrosatellite at chromosome 4q35. Epigenetic derepression permits the distal-most D4Z4 unit to transcribe DUX4, with transcripts stabilised by splicing to a poly(A) signal on permissive 4qA haplotypes. The pioneer transcription factor DUX4 activates target genes that are proposed to drive FSHD pathology. While this toxic gain-of-function model is a satisfying "bottom-up" genotype-to-phenotype link, DUX4 is rarely detectable in muscle and DUX4 target gene expression is inconsistent in patients. A reliable biomarker for FSHD is suppression of a target gene score of PAX7, a master regulator of myogenesis. However, it is unclear how this "top-down" finding links to genomic changes that characterise FSHD and to DUX4. Here, we explore the roles and interactions of DUX4 and PAX7 in FSHD pathology and how the relationship between these two transcription factors deepens understanding via the immune system and muscle regeneration. Considering how FSHD pathomechanisms are represented by "DUX4opathy" models has implications for developing therapies and current clinical trials.
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Affiliation(s)
| | - Peter S Zammit
- Randall Centre for Cell and Molecular BiophysicsKing's College LondonLondonUK
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16
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Nicolau S, Milone M, Liewluck T. Guidelines for genetic testing of muscle and neuromuscular junction disorders. Muscle Nerve 2021; 64:255-269. [PMID: 34133031 DOI: 10.1002/mus.27337] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 05/28/2021] [Indexed: 12/24/2022]
Abstract
Despite recent advances in the understanding of inherited muscle and neuromuscular junction diseases, as well as the advent of a wide range of genetic tests, patients continue to face delays in diagnosis of sometimes treatable disorders. These guidelines outline an approach to genetic testing in such disorders. Initially, a patient's phenotype is evaluated to identify myopathies requiring directed testing, including myotonic dystrophies, facioscapulohumeral muscular dystrophy, oculopharyngeal muscular dystrophy, mitochondrial myopathies, dystrophinopathies, and oculopharyngodistal myopathy. Initial investigation in the remaining patients is generally a comprehensive gene panel by next-generation sequencing. Broad panels have a higher diagnostic yield and can be cost-effective. Due to extensive phenotypic overlap and treatment implications, genes responsible for congenital myasthenic syndromes should be included when evaluating myopathy patients. For patients whose initial genetic testing is negative or inconclusive, phenotypic re-evaluation is warranted, along with consideration of genes and variants not included initially, as well as their acquired mimickers.
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Affiliation(s)
- Stefan Nicolau
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
| | | | - Teerin Liewluck
- Department of Neurology, Mayo Clinic, Rochester, Minnesota, USA
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