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Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common muscular dystrophies. Over the last decade, a consensus was reached regarding the underlying cause of FSHD allowing—for the first time—a targeted approach to treatment. FSHD is the result of a toxic gain-of-function from de-repression of the DUX4 gene, a gene not normally expressed in skeletal muscle. With a clear therapeutic target, there is increasing interest in drug development for FSHD, an interest buoyed by the recent therapeutic successes in other neuromuscular diseases. Herein, we review the underlying disease mechanism, potential therapeutic approaches as well as the state of trial readiness in the planning and execution of future clinical trials in FSHD.
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Affiliation(s)
- Leo H Wang
- Department of Neurology, University of Washington, Seattle, WA, USA
| | - Rabi Tawil
- Department of Neurology, University of Rochester, Rochester, NY, USA
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2
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Abstract
Facioscapulohumeral muscular dystrophy (FSHD), a progressive myopathy that afflicts individuals of all ages, provides a powerful model of the complex interplay between genetic and epigenetic mechanisms of chromatin regulation. FSHD is caused by dysregulation of a macrosatellite repeat, either by contraction of the repeat or by mutations in silencing proteins. Both cases lead to chromatin relaxation and, in the context of a permissive allele, aberrant expression of the DUX4 gene in skeletal muscle. DUX4 is a pioneer transcription factor that activates a program of gene expression during early human development, after which its expression is silenced in most somatic cells. When misexpressed in FSHD skeletal muscle, the DUX4 program leads to accumulated muscle pathology. Epigenetic regulators of the disease locus represent particularly attractive therapeutic targets for FSHD, as many are not global modifiers of the genome, and altering their expression or activity should allow correction of the underlying defect.
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MESH Headings
- CRISPR-Cas Systems
- Chromatin/chemistry
- Chromosomal Proteins, Non-Histone/genetics
- Chromosomal Proteins, Non-Histone/metabolism
- Chromosomes, Human, Pair 4
- DNA (Cytosine-5-)-Methyltransferases/genetics
- DNA (Cytosine-5-)-Methyltransferases/metabolism
- DNA Methylation
- Epigenesis, Genetic
- Gene Editing
- Genetic Loci
- Genome, Human
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- Humans
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscular Dystrophy, Facioscapulohumeral/classification
- Muscular Dystrophy, Facioscapulohumeral/genetics
- Muscular Dystrophy, Facioscapulohumeral/metabolism
- Muscular Dystrophy, Facioscapulohumeral/pathology
- Mutation
- Severity of Illness Index
- DNA Methyltransferase 3B
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Affiliation(s)
- Charis L Himeda
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Nevada 89557, USA;
| | - Peter L Jones
- Department of Pharmacology, School of Medicine, University of Nevada, Reno, Nevada 89557, USA;
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Denny AP, Heather AK. Are Antioxidants a Potential Therapy for FSHD? A Review of the Literature. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:7020295. [PMID: 28690764 PMCID: PMC5485364 DOI: 10.1155/2017/7020295] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 04/27/2017] [Accepted: 05/03/2017] [Indexed: 11/21/2022]
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is an inherited myopathy affecting approximately 1 in 7500 individuals worldwide. It is a progressive disease characterised by skeletal muscle weakness and wasting. A genetic mutation on the 4q35 chromosome results in the expression of the double homeobox 4 gene (DUX4) which drives oxidative stress, inflammation, toxicity, and atrophy within the skeletal muscle. FSHD is characterised by oxidative stress, and there is currently no cure and a lack of therapies for the disease. Antioxidants have been researched for many years, with investigators aiming to use antioxidants therapeutically for oxidative stress-associated diseases. This has included both natural and synthetic antioxidants. The use of antioxidants in preclinical or clinical models has been largely successful with a plethora of research reporting positive results. However, when translated to clinical trials, the use of antioxidants as a therapeutic intervention for a variety of disease has been largely unsuccessful. Moreover, specifically focusing on FSHD, limited research has been conducted on the use of antioxidants as a therapy in either preclinical or clinical models. This review summarises the current state of antioxidant use in the treatment of FSHD and discusses their potential avenue for therapeutic use for FSHD patients.
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Affiliation(s)
- Adam Philip Denny
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Alison Kay Heather
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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Himeda CL, Jones TI, Jones PL. CRISPR/dCas9-mediated Transcriptional Inhibition Ameliorates the Epigenetic Dysregulation at D4Z4 and Represses DUX4-fl in FSH Muscular Dystrophy. Mol Ther 2016; 24:527-35. [PMID: 26527377 PMCID: PMC4786914 DOI: 10.1038/mt.2015.200] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 10/21/2015] [Indexed: 12/16/2022] Open
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is one of the most prevalent myopathies, affecting males and females of all ages. Both forms of the disease are linked by epigenetic derepression of the D4Z4 macrosatellite repeat array at chromosome 4q35, leading to aberrant expression of D4Z4-encoded RNAs in skeletal muscle. Production of full-length DUX4 (DUX4-fl) mRNA from the derepressed D4Z4 array results in misexpression of DUX4-FL protein and its transcriptional targets, and apoptosis, ultimately leading to accumulated muscle pathology. Returning the chromatin at the FSHD locus to its nonpathogenic, epigenetically repressed state would simultaneously affect all D4Z4 RNAs, inhibiting downstream pathogenic pathways, and is thus an attractive therapeutic strategy. Advances in CRISPR/Cas9-based genome editing make it possible to target epigenetic modifiers to an endogenous disease locus, although reports to date have focused on more typical genomic regions. Here, we demonstrate that a CRISPR/dCas9 transcriptional inhibitor can be specifically targeted to the highly repetitive FSHD macrosatellite array and alter the chromatin to repress expression of DUX4-fl in primary FSHD myocytes. These results implicate the promoter and exon 1 of DUX4 as potential therapeutic targets and demonstrate the utility of CRISPR technology for correction of the epigenetic dysregulation in FSHD.
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Affiliation(s)
- Charis L Himeda
- The Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Takako I Jones
- The Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Peter L Jones
- The Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
- The Department of Neurology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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Himeda CL, Jones TI, Jones PL. Facioscapulohumeral muscular dystrophy as a model for epigenetic regulation and disease. Antioxid Redox Signal 2015; 22:1463-82. [PMID: 25336259 PMCID: PMC4432493 DOI: 10.1089/ars.2014.6090] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
SIGNIFICANCE Aberrant epigenetic regulation is an integral aspect of many diseases and complex disorders. Facioscapulohumeral muscular dystrophy (FSHD), a progressive myopathy that afflicts individuals of all ages, is caused by disrupted genetic and epigenetic regulation of a macrosatellite repeat. FSHD provides a powerful model to investigate disease-relevant epigenetic modifiers and general mechanisms of epigenetic regulation that govern gene expression. RECENT ADVANCES In the context of a genetically permissive allele, the one aspect of FSHD that is consistent across all known cases is the aberrant epigenetic state of the disease locus. In addition, certain mutations in the chromatin regulator SMCHD1 (structural maintenance of chromosomes hinge-domain protein 1) are sufficient to cause FSHD2 and enhance disease severity in FSHD1. Thus, there are multiple pathways to generate the epigenetic dysregulation required for FSHD. CRITICAL ISSUES Why do some individuals with the genetic requirements for FSHD develop disease pathology, while others remain asymptomatic? Similarly, disease progression is highly variable among individuals. What are the relative contributions of genetic background and environmental factors in determining disease manifestation, progression, and severity in FSHD? What is the interplay between epigenetic factors regulating the disease locus and which, if any, are viable therapeutic targets? FUTURE DIRECTIONS Epigenetic regulation represents a potentially powerful therapeutic target for FSHD. Determining the epigenetic signatures that are predictive of disease severity and identifying the spectrum of disease modifiers in FSHD are vital to the development of effective therapies.
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Affiliation(s)
- Charis L Himeda
- The Wellstone Program and the Departments of Cell and Developmental Biology and Neurology, University of Massachusetts Medical School , Worcester, Massachusetts
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Zeng W, Chen YY, Newkirk DA, Wu B, Balog J, Kong X, Ball AR, Zanotti S, Tawil R, Hashimoto N, Mortazavi A, van der Maarel SM, Yokomori K. Genetic and epigenetic characteristics of FSHD-associated 4q and 10q D4Z4 that are distinct from non-4q/10q D4Z4 homologs. Hum Mutat 2014; 35:998-1010. [PMID: 24838473 DOI: 10.1002/humu.22593] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 05/06/2014] [Indexed: 12/15/2022]
Abstract
Facioscapulohumeral dystrophy (FSHD) is one of the most prevalent muscular dystrophies. The majority of FSHD cases are linked to a decreased copy number of D4Z4 macrosatellite repeats on chromosome 4q (FSHD1). Less than 5% of FSHD cases have no repeat contraction (FSHD2), most of which are associated with mutations of SMCHD1. FSHD is associated with the transcriptional derepression of DUX4 encoded within the D4Z4 repeat, and SMCHD1 contributes to its regulation. We previously found that the loss of heterochromatin mark (i.e., histone H3 lysine 9 tri-methylation (H3K9me3)) at D4Z4 is a hallmark of both FSHD1 and FSHD2. However, whether this loss contributes to DUX4 expression was unknown. Furthermore, additional D4Z4 homologs exist on multiple chromosomes, but they are largely uncharacterized and their relationship to 4q/10q D4Z4 was undetermined. We found that the suppression of H3K9me3 results in displacement of SMCHD1 at D4Z4 and increases DUX4 expression in myoblasts. The DUX4 open reading frame (ORF) is disrupted in D4Z4 homologs and their heterochromatin is unchanged in FSHD. The results indicate the significance of D4Z4 heterochromatin in DUX4 gene regulation and reveal the genetic and epigenetic distinction between 4q/10q D4Z4 and the non-4q/10q homologs, highlighting the special role of the 4q/10q D4Z4 chromatin and the DUX4 ORF in FSHD.
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Affiliation(s)
- Weihua Zeng
- Department of Biological Chemistry, School of Medicine, University of California, Irvine, California; Department of Developmental and Cell Biology, School of Biological Sciences, University of California, Irvine, California
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Sacconi S, Lemmers R, Balog J, van der Vliet P, Lahaut P, van Nieuwenhuizen M, Straasheijm K, Debipersad R, Vos-Versteeg M, Salviati L, Casarin A, Pegoraro E, Tawil R, Bakker E, Tapscott S, Desnuelle C, van der Maarel S. The FSHD2 gene SMCHD1 is a modifier of disease severity in families affected by FSHD1. Am J Hum Genet 2013; 93:744-51. [PMID: 24075187 DOI: 10.1016/j.ajhg.2013.08.004] [Citation(s) in RCA: 126] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 07/04/2013] [Accepted: 08/01/2013] [Indexed: 01/04/2023] Open
Abstract
Facioscapulohumeral muscular dystrophy type 1 (FSHD1) is caused by contraction of the D4Z4 repeat array on chromosome 4 to a size of 1-10 units. The residual number of D4Z4 units inversely correlates with clinical severity, but significant clinical variability exists. Each unit contains a copy of the DUX4 retrogene. Repeat contractions are associated with changes in D4Z4 chromatin structure that increase the likelihood of DUX4 expression in skeletal muscle, but only when the repeat resides in a genetic background that contains a DUX4 polyadenylation signal. Mutations in the structural maintenance of chromosomes flexible hinge domain containing 1 (SMCHD1) gene, encoding a chromatin modifier of D4Z4, also result in the increased likelihood of DUX4 expression in individuals with a rare form of FSHD (FSHD2). Because SMCHD1 directly binds to D4Z4 and suppresses somatic expression of DUX4, we hypothesized that SMCHD1 may act as a genetic modifier in FSHD1. We describe three unrelated individuals with FSHD1 presenting an unusual high clinical severity based on their upper-sized FSHD1 repeat array of nine units. Each of these individuals also carries a mutation in the SMCHD1 gene. Familial carriers of the FSHD1 allele without the SMCHD1 mutation were only mildly affected, suggesting a modifier effect of the SMCHD1 mutation. Knocking down SMCHD1 in FSHD1 myotubes increased DUX4 expression, lending molecular support to a modifier role for SMCHD1 in FSHD1. We conclude that FSHD1 and FSHD2 share a common pathophysiological pathway in which the FSHD2 gene can act as modifier for disease severity in families affected by FSHD1.
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van der Maarel SM, Miller DG, Tawil R, Filippova GN, Tapscott SJ. Facioscapulohumeral muscular dystrophy: consequences of chromatin relaxation. Curr Opin Neurol 2012; 25:614-20. [PMID: 22892954 PMCID: PMC3653067 DOI: 10.1097/wco.0b013e328357f22d] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
PURPOSE OF REVIEW In recent years, we have seen remarkable progress in our understanding of the disease mechanism underlying facioscapulohumeral muscular dystrophy (FSHD). The purpose of this review is to provide a comprehensive overview of our current understanding of the disease mechanism and to discuss the observations supporting the possibility of a developmental defect in this disorder. RECENT FINDINGS In the majority of cases, FSHD is caused by contraction of the D4Z4 repeat array (FSHD1). This results in local chromatin relaxation and stable expression of the DUX4 retrogene in skeletal muscle, but only when a polymorphic DUX4 polyadenylation signal is present. In some cases (FSHD2), D4Z4 chromatin relaxation and stable DUX4 expression occur in the absence of D4Z4 array contraction. DUX4 is a germline transcription factor and its expression in skeletal muscle leads to activation of early stem cell and germline programs and transcriptional activation of retroelements. SUMMARY Recent studies have provided a plausible disease mechanism for FSHD in which FSHD results from inappropriate expression of the germline transcription factor DUX4. The genes regulated by DUX4 suggest several mechanisms of muscle damage, and provide potential biomarkers and therapeutic targets that should be investigated in future studies.
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Richards M, Coppée F, Thomas N, Belayew A, Upadhyaya M. Facioscapulohumeral muscular dystrophy (FSHD): an enigma unravelled? Hum Genet 2011; 131:325-40. [PMID: 21984394 DOI: 10.1007/s00439-011-1100-z] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 09/26/2011] [Indexed: 01/02/2023]
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is the third most common muscular dystrophy after the dystrophinopathies and myotonic dystrophy and is associated with a typical pattern of muscle weakness. Most patients with FSHD carry a large deletion in the polymorphic D4Z4 macrosatellite repeat array at 4q35 and present with 1-10 repeats whereas non-affected individuals possess 11-150 repeats. An almost identical repeat array is present at 10q26 and the high sequence identity between these two arrays can cause difficulties in molecular diagnosis. Each 3.3-kb D4Z4 unit contains a DUX4 (double homeobox 4) gene that, among others, is activated upon contraction of the 4q35 repeat array due to the induction of chromatin remodelling of the 4qter region. A number of 4q subtelomeric sequence variants are now recognised, although FSHD only occurs in association with three 'permissive' haplotypes, each of which is associated with a polyadenylation signal located immediately distal of the last D4Z4 unit. The resulting poly-A tail appears to stabilise DUX4 mRNAs transcribed from this most distal D4Z4 unit in FSHD muscle cells. Synthesis of both the DUX4 transcripts and protein in FSHD muscle cells induces significant cell toxicity. DUX4 is a transcription factor that may target several genes which results in a deregulation cascade which inhibits myogenesis, sensitises cells to oxidative stress and induces muscle atrophy, thus recapitulating many of the key molecular features of FSHD.
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Affiliation(s)
- Mark Richards
- School of Medicine, Institute of Medical Genetics, Cardiff University, Cardiff, CF14 4XN, UK
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van der Maarel SM, Tawil R, Tapscott SJ. Facioscapulohumeral muscular dystrophy and DUX4: breaking the silence. Trends Mol Med 2011; 17:252-8. [PMID: 21288772 PMCID: PMC3092836 DOI: 10.1016/j.molmed.2011.01.001] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Revised: 12/14/2010] [Accepted: 01/03/2011] [Indexed: 01/10/2023]
Abstract
Autosomal dominant facioscapulohumeral muscular dystrophy (FSHD) has an unusual pathogenic mechanism. FSHD is caused by deletion of a subset of D4Z4 macrosatellite repeat units in the subtelomere of chromosome 4q. Recent studies provide compelling evidence that a retrotransposed gene in the D4Z4 repeat, DUX4, is expressed in the human germline and then epigenetically silenced in somatic tissues. In FSHD, the combination of inefficient chromatin silencing of the D4Z4 repeat and polymorphisms on the FSHD-permissive alleles that stabilize the DUX4 mRNAs emanating from the repeat result in inappropriate DUX4 protein expression in muscle cells. FSHD is thereby the first example of a human disease caused by the inefficient repression of a retrogene in a macrosatellite repeat array.
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Affiliation(s)
- Silvère M van der Maarel
- Leiden University Medical Center, Department of Human Genetics, Albinusdreef 2, 2333 ZA, Leiden, Netherlands. Phone: +31 71 526 9480, Fax: +31 71 526 8285
| | - Rabi Tawil
- University of Rochester Medical Center, Department of Neurology, POBox 673, 601 Elmwood Avenue, Rochester, NY 14642 USA. Phone: 1-585-275-6372, FAX: 1-585-273-1255
| | - Stephen J. Tapscott
- Division of Human Biology, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109 USA. Phone: 1-206-667-4499, FAX 1-206-667-6524
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Orrell RW. Facioscapulohumeral dystrophy and scapuloperoneal syndromes. HANDBOOK OF CLINICAL NEUROLOGY 2011; 101:167-80. [PMID: 21496633 DOI: 10.1016/b978-0-08-045031-5.00013-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Facioscapulohumeral dystrophy (FSHD) is the third most common muscular dystrophy. It is named for its characteristic involvement of the muscles of the face and upper arm. It is present worldwide, with a prevalence of around 4 per 100000 and an incidence of about 1 in 20000. Overall lifespan is not affected significantly. The scapuloperoneal syndrome is a rarer presentation that may cause some confusion. FSHD is an autosomal dominant condition. The molecular genetics of FSHD are complex, with current understanding focusing on epigenetic effects related to contraction-dependent (FSHD1) and contraction-independent (FSHD2) effects of a hypomethylated repeat sequence (D4Z4), in the presence of a specific 4qA161 phenotype. Molecular genetic diagnosis is available based on these findings, but with some complexities which may lead to false-negative results on routine laboratory investigation. No medication has been demonstrated to alter the clinical course of the disease significantly. A range of supportive measures may be applied. This chapter reviews the epidemiology, pathogenesis, genetics, clinical features, investigation, prognosis, and management of patients with FSHD and the scapuloperoneal syndrome.
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Affiliation(s)
- Richard W Orrell
- University Department of Clinical Neurosciences, UCL Institute of Neurology, London, UK
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Barro M, Carnac G, Flavier S, Mercier J, Vassetzky Y, Laoudj-Chenivesse D. Myoblasts from affected and non-affected FSHD muscles exhibit morphological differentiation defects. J Cell Mol Med 2010; 14:275-89. [PMID: 18505476 PMCID: PMC2910739 DOI: 10.1111/j.1582-4934.2008.00368.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Facioscapulohumeral dystrophy (FSHD) is a muscular hereditary disease with a prevalence of 1 in 20,000 caused by a partial deletion of a subtelomeric repeat array on chromosome 4q. However, very little is known about the pathogenesis as well as the molecular and biochemical changes linked to the progressive muscle degeneration observed in these patients. Several studies have investigated possible pathophysiological pathways in FSHD myoblasts and mature muscle cells but some of these reports were apparently in contradiction. The discrepancy between these studies may be explained by differences between the sources of myoblasts. Therefore, we decided to thoroughly analyze affected and unaffected muscles from patients with FSHD in terms of vulnerability to oxidative stress, differentiation capacity and morphological abnormalities. We have established a panel of primary myoblast cell cultures from patients affected with FSHD and matched healthy individuals. Our results show that primary myoblasts are more susceptible to an induced oxidative stress than control myoblasts. Moreover, we demonstrate that both types of FSHD primary myoblasts differentiate into multi-nucleated myotubes, which present morphological abnormalities. Whereas control myoblasts fuse to form branched myotubes with aligned nuclei, FSHD myoblasts fuse to form either thin and branched myotubes with aligned nuclei or large myotubes with random nuclei distribution. In conclusion, we postulate that these abnormalities could be responsible for muscle weakness in patients with FSHD and provide an important marker for FSHD myoblasts.
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de Greef JC, Lemmers RJLF, van Engelen BGM, Sacconi S, Venance SL, Frants RR, Tawil R, van der Maarel SM. Common epigenetic changes of D4Z4 in contraction-dependent and contraction-independent FSHD. Hum Mutat 2009; 30:1449-59. [PMID: 19728363 DOI: 10.1002/humu.21091] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Facioscapulohumeral muscular dystrophy (FSHD), caused by partial deletion of the D4Z4 macrosatellite repeat on chromosome 4q, has a complex genetic and epigenetic etiology. To develop FSHD, D4Z4 contraction needs to occur on a specific genetic background. Only contractions associated with the 4qA161 haplotype cause FSHD. In addition, contraction of the D4Z4 repeat in FSHD patients is associated with significant D4Z4 hypomethylation. To date, however, the methylation status of contracted repeats on nonpathogenic haplotypes has not been studied. We have performed a detailed methylation study of the D4Z4 repeat on chromosome 4q and on a highly homologous repeat on chromosome 10q. We show that patients with a D4Z4 deletion (FSHD1) have D4Z4-restricted hypomethylation. Importantly, controls with a D4Z4 contraction on a nonpathogenic chromosome 4q haplotype or on chromosome 10q also demonstrate hypomethylation. In 15 FSHD families without D4Z4 contractions but with at least one 4qA161 haplotype (FSHD2), we observed D4Z4-restricted hypomethylation on chromosomes 4q and 10q. This finding implies that a genetic defect resulting in D4Z4 hypomethylation underlies FSHD2. In conclusion, we describe two ways to develop FSHD: (1) contraction-dependent or (2) contraction-independent D4Z4 hypomethylation on the 4qA161 subtelomere.
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Affiliation(s)
- Jessica C de Greef
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
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Nadaj-Pakleza AA, Vincitorio CM, Laforêt P, Eymard B, Dion E, Teijeira S, Vietez I, Jeanpierre M, Navarro C, Stojkovic T. Permanent muscle weakness in MC
Ardle disease. Muscle Nerve 2009; 40:350-7. [DOI: 10.1002/mus.21351] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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de Greef JC, Frants RR, van der Maarel SM. Epigenetic mechanisms of facioscapulohumeral muscular dystrophy. Mutat Res 2008; 647:94-102. [PMID: 18723032 PMCID: PMC2650037 DOI: 10.1016/j.mrfmmm.2008.07.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2008] [Revised: 07/18/2008] [Accepted: 07/23/2008] [Indexed: 04/08/2023]
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) seems to be caused by a complex epigenetic disease mechanism as a result of contraction of the polymorphic macrosatellite repeat D4Z4 on chromosome 4qter. Currently, the exact mechanism causing the FSHD phenotype is still not elucidated. In this review, we discuss the genetic and epigenetic changes observed in patients with FSHD and the possible disease mechanisms that may be associated with FSHD pathogenesis.
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Affiliation(s)
- Jessica C. de Greef
- Department of Human Genetics, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Rune R. Frants
- Department of Human Genetics, Leiden University Medical Center (LUMC), Leiden, The Netherlands
| | - Silvère M. van der Maarel
- Department of Human Genetics, Leiden University Medical Center (LUMC), Leiden, The Netherlands
- Address correspondence and reprint requests to: Dr. S.M. van der Maarel, Department of Human Genetics, Center for Human and Clinical Genetics, Leiden University Medical Center, Bldg. 2, room S-03-042, Postal zone S-4-P, P.O. Box 9600, 2300 RC Leiden, The Netherlands
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Lemmers RJLF, van der Wielen MJR, Bakker E, Frants RR, van der Maarel SM. Rapid and accurate diagnosis of facioscapulohumeral muscular dystrophy. Neuromuscul Disord 2006; 16:615-7; author reply 617-8. [PMID: 16938455 DOI: 10.1016/j.nmd.2006.07.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 06/02/2006] [Accepted: 07/17/2006] [Indexed: 11/21/2022]
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van der Maarel SM, Frants RR, Padberg GW. Facioscapulohumeral muscular dystrophy. Biochim Biophys Acta Mol Basis Dis 2006; 1772:186-94. [PMID: 16837171 DOI: 10.1016/j.bbadis.2006.05.009] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 05/30/2006] [Accepted: 05/30/2006] [Indexed: 01/01/2023]
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is caused by a cascade of epigenetic events following contraction of the polymorphic macrosatellite repeat D4Z4 in the subtelomere of chromosome 4q. Currently, the central issue is whether immediate downstream effects are local (i.e., at chromosome 4q) or global (genome-wide) and there is evidence for both scenarios. Currently, there is no therapy for FSHD, mostly because of our lack of understanding of the primary pathogenic process in FSHD muscle. Clinical trials based on suppression of inflammatory reactions or increasing muscle mass by drugs or training have been disappointing. A recent, probably the first evidence-based pilot trial to revert epigenetic changes did also not provide grounds for a larger clinical study. Clearly, better disease models need to be developed to identify and test novel intervention strategies to eventually improve the quality of life for patients with FSHD.
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Affiliation(s)
- Silvère M van der Maarel
- Leiden University Medical Center (LUMC), Department of Human Genetics, Postal zone S-3-P, PO box 9600, 2300 RC Leiden, The Netherlands.
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Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is a dominantly inherited disorder with an initially restricted pattern of weakness. Early involvement of the facial and scapular stabilizer muscles results in a distinctive clinical presentation. Progression is descending, with subsequent involvement of either the distal anterior leg or hip-girdle muscles. There is wide variability in age at onset, disease severity, and side-to-side symmetry, which is evident even within affected members of the same family. Although FSHD is considered a relatively benign dystrophy by some, as many as 20% of patients eventually become wheelchair-bound. Associated nonskeletal muscle manifestations include high-frequency hearing loss as well as retinal telangiectasias, both of which are rarely symptomatic. The causal genetic lesion in FSHD was described over a decade ago, raising hope that knowledge about its molecular and cellular pathophysiology was soon to follow. In the vast majority of cases, FSHD results from a heterozygous partial deletion of a critical number of repetitive elements (D4Z4) on chromosome 4q35; yet, to date, no causal gene has been identified. The accumulating evidence points to a complex, perhaps unique, molecular genetic mechanism. The absence of detectable expressed sequences from D4Z4, the association of FSHD-causing 4q35 deletions with a specific distal genomic sequence (4qA allele), altered DNA methylation patterns on 4q35, as well as other direct and indirect evidence point to epigenetic mechanisms. As a consequence, partial deletion of D4Z4 results in a (local) chromatin change and ultimately results in the loss of appropriate control of gene expression. There is at present no effective treatment for FSHD. A better understanding of the underlying pathophysiology is needed to design targeted interventions. Despite these limitations, however, two randomized controlled clinical trials have been conducted on FSHD. These trials, along with a previous natural history study, have helped to better define outcome measures for future trials in FSHD as well as other dystrophies.
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Affiliation(s)
- Rabi Tawil
- University of Rochester Medical Center, Neuromuscular Disease Center, P.O. Box 673, 601 Elmwood Avenue, Rochester, New York 14642, USA.
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Rijkers T, Deidda G, van Koningsbruggen S, van Geel M, Lemmers RJLF, van Deutekom JCT, Figlewicz D, Hewitt JE, Padberg GW, Frants RR, van der Maarel SM. FRG2, an FSHD candidate gene, is transcriptionally upregulated in differentiating primary myoblast cultures of FSHD patients. J Med Genet 2005; 41:826-36. [PMID: 15520407 PMCID: PMC1735617 DOI: 10.1136/jmg.2004.019364] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
BACKGROUND Autosomal dominant facioscapulohumeral muscular dystrophy (FSHD) is associated with partial deletion of the subtelomeric D4Z4 repeat array on chromosome 4qter. This chromosomal rearrangement may result in regional chromatin relaxation and transcriptional deregulation of genes nearby. METHODS AND RESULTS Here we describe the isolation and characterisation of FRG2, a member of a chromosomally dispersed gene family, mapping only 37 kb proximal to the D4Z4 repeat array. Homology and motif searches yielded no clues to the function of the predicted protein. FRG2 expression is undetectable in all tissues tested except for differentiating myoblasts of FSHD patients, which display low, yet distinct levels of FRG2 expression, partly from chromosome 4 but predominantly originating from its homologue on chromosome 10. However, in non-FSHD myopathy patients only distantly related FRG2 homologues are transcribed, while differentiating myoblasts from healthy controls fail to express any member of this gene family. Moreover, fibroblasts of FSHD patients and control individuals undergoing forced Ad5-MyoD mediated myogenesis show expression of FRG2 mainly originating from chromosome 10. Luciferase reporter assays show that the FRG2 promoter region can direct high levels of expression but is inhibited by increasing numbers of D4Z4 repeat units. Transient transfection experiments with FRG2 fusion-protein constructs reveal nuclear localisation and apparently FRG2 overexpression causes a wide range of morphological changes. CONCLUSION The localisation of FRG2 genes close to the D4Z4 repeats on chromosome 4 and 10, their transcriptional upregulation specifically in FSHD myoblast cultures, potential involvement in myogenesis, and promoter properties qualify FRG2 as an attractive candidate for FSHD pathogenesis.
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Cell Differentiation
- Cells, Cultured
- Chromosomes, Human, Pair 10/genetics
- Chromosomes, Human, Pair 4/genetics
- Female
- Genetic Predisposition to Disease
- Humans
- Male
- Molecular Sequence Data
- Muscle Development
- Muscular Dystrophy, Facioscapulohumeral/genetics
- Myoblasts, Skeletal/chemistry
- Myoblasts, Skeletal/cytology
- Myoblasts, Skeletal/metabolism
- Nuclear Proteins
- Promoter Regions, Genetic
- Proteins/analysis
- Proteins/genetics
- Proteins/metabolism
- Transcriptional Activation
- Up-Regulation
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Affiliation(s)
- T Rijkers
- Department of Human Genetics, Center for Human and Clinical Genetics, Leiden University Medical Center, Wassenaarseweg 72, 2333 AL Leiden, The Netherlands
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Lemmers RJFL, Wohlgemuth M, Frants RR, Padberg GW, Morava E, van der Maarel SM. Contractions of D4Z4 on 4qB subtelomeres do not cause facioscapulohumeral muscular dystrophy. Am J Hum Genet 2004; 75:1124-30. [PMID: 15467981 PMCID: PMC1182148 DOI: 10.1086/426035] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Accepted: 09/16/2004] [Indexed: 02/04/2023] Open
Abstract
Facioscapulohumeral muscular dystrophy (FSHD) is associated with contractions of the D4Z4 repeat in the subtelomere of chromosome 4q. Two allelic variants of chromosome 4q (4qA and 4qB) exist in the region distal to D4Z4. Although both variants are almost equally frequent in the population, FSHD is associated exclusively with the 4qA allele. We identified three families with FSHD in which each proband carries two FSHD-sized alleles and is heterozygous for the 4qA/4qB polymorphism. Segregation analysis demonstrated that FSHD-sized 4qB alleles are not associated with disease, since these were present in unaffected family members. Thus, in addition to a contraction of D4Z4, additional cis-acting elements on 4qA may be required for the development of FSHD. Alternatively, 4qB subtelomeres may contain elements that prevent FSHD pathogenesis.
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Affiliation(s)
- Richard J F L Lemmers
- Leiden University Medical Center, Center for Human and Clinical Genetics, Department of Human Genetics, Leiden, The Netherlands
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