Direct detection of 4q35 rearrangements implicated in facioscapulohumeral muscular dystrophy (FSHD)

Evaluation of Optical Genome Mapping in Clinical Genetic Testing of Facioscapulohumeral Muscular Dystrophy

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.

Complex 4q35 and 10q26 Rearrangements: A Challenge for Molecular Diagnosis of Patients With Facioscapulohumeral Dystrophy

Background and Objectives

After clinical evaluation, the molecular diagnosis of type 1 facioscapulohumeral dystrophy (FSHD1) relies in most laboratories on the detection of a shortened D4Z4 array at the 4q35 locus by Southern blotting. In many instances, this molecular diagnosis remains inconclusive and requires additional experiments to determine the number of D4Z4 units or identify somatic mosaicism, 4q-10q translocations, and proximal p13E-11 deletions. These limitations highlight the need for alternative methodologies, illustrated by the recent emergence of novel technologies such as molecular combing (MC), single molecule optical mapping (SMOM), or Oxford Nanopore-based long-read sequencing providing a more comprehensive analysis of 4q and 10q loci. Over the last decade, MC revealed a further increasing complexity in the organization of the 4q and 10q distal regions in patients with FSHD with cis-duplication of D4Z4 arrays in approximately 1%-2% of cases.

Methods

By using MC, we investigated in our center 2,363 cases for molecular diagnosis of FSHD. We also evaluated whether previously reported cis-duplications might be identified by SMOM using the Bionano EnFocus FSHD 1.0 algorithm.

Results

In our cohort of 2,363 samples, we identified 147 individuals carrying an atypical organization of the 4q35 or 10q26 loci. Mosaicism is the most frequent category followed by cis-duplications of the D4Z4 array. We report here chromosomal abnormalities of the 4q35 or 10q26 loci in 54 patients clinically described as FSHD, which are not present in the healthy population. In one-third of the 54 patients, these rearrangements are the only genetic defect suggesting that they might be causative of the disease. By analyzing DNA samples from 3 patients carrying a complex rearrangement of the 4q35 region, we further showed that the SMOM direct assembly of the 4q and 10q alleles failed to reveal these abnormalities and lead to negative results for FSHD molecular diagnosis.

Discussion

This work further highlights the complexity of the 4q and 10q subtelomeric regions and the need of in-depth analyses in a significant number of cases. This work also highlights the complexity of the 4q35 region and interpretation issues with consequences on the molecular diagnosis of patients or genetic counseling.

A feasibility study of noninvasive prenatal diagnosis in facioscapulohumeral muscular dystrophy type 1 in a Chinese family

Objective: To demonstrate the feasibility of haplotype-based noninvasive prenatal diagnosis of Facioscapulohumeral Muscular Dystrophy type 1 (FSHD1). Methods: Bionano optical mapping was used to identify the D4Z4 structural variation of the genomic DNA sample from the proband affected with FSHD1. In addition, based on the technique of next generation sequencing, the pathogenic haplotype was determined by using trio strategy through genotyping his parents, and also fetal inheritance of paternal haplotypes was then deduced using the Hidden Markov Model. Results: Bionano optical mapping analysis revealed that the proband has only three D4Z4 repeats left in the 4q35 chromosomal region and a disease-permitting 4qA haplotype. The other normal allele of the proband contains 29 D4Z4 repeats and also a 4qA haplotype. The noninvasive cell-free fetal DNA (cffDNA)-based haplotype analysis suggested that the fetus inherited the pathogenic allele from his father and thus was predicted to be affected by FSHD1. In addition, Bionano optical mapping also demonstrated the presence of the pathogenic allele in the fetus by interrogating the genomic DNA from the amniotic fluid cells. Conclusion: Our study showed the cffDNA-based haplotyping was feasible for the noninvasive prenatal diagnosis of FSHD1, which is able to provide earlier testing results with a lower risk of miscarriage and infection than invasive techniques.

High resolution breakpoint junction mapping of proximally extended D4Z4 deletions in FSHD1 reveals evidence for a founder effect

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.

Validation of Optical Genome Mapping for the Molecular Diagnosis of Facioscapulohumeral Muscular Dystrophy

The molecular diagnosis of facioscapulohumeral muscular dystrophy (FSHD) relies on detecting contractions of the unique D4Z4 repeat array at the chromosome 4q35 locus in the presence of a permissive 4q35A haplotype. Long, intact DNA molecules are required for accurate sizing of D4Z4 repeats. We validated the use of optical genome mapping to determine size and haplotype of D4Z4 alleles for FSHD analysis. The cohort included 36 unique DNA specimens from fresh blood samples or archived agarose plugs. High-molecular- weight DNA underwent sequence-specific labeling followed by separation and image analysis with data collection on the Saphyr system. D4Z4 allele sizes were calculated and haplotypes determined from the labeling patterns. Each specimen had previous diagnostic testing using restriction enzyme digests with EcoRI, EcoRI/BlnI, XapI, or HindIII, followed by pulsed field gel electrophoresis and Southern blot analysis with appropriate probes. Optical genome mapping detected 4q35 and 10q26 alleles ranging from 1 to 79 D4Z4 repeats and showed strong correlation with Southern blot allele sizing (R² = 0.95) and haplotyping (133 of 134; 99.4% haplotype match). Analysis of inter-assay and intra-assay runs showed high reproducibility (0.03 to 0.94 %CV). Subsequent optical genome mapping for routine clinical testing from 315 clinical FSHD cases compared favorably with historical result trends. Optical genome mapping is an accurate and highly reproducible method for chromosomal abnormalities associated with FSHD.

Facioscapulohumeral muscular dystrophy: genetics, gene activation and downstream signalling with regard to recent therapeutic approaches: an update

Whilst a disease-modifying treatment for Facioscapulohumeral muscular dystrophy (FSHD) does not exist currently, recent advances in complex molecular pathophysiology studies of FSHD have led to possible therapeutic approaches for its targeted treatment. Although the underlying genetics of FSHD have been researched extensively, there remains an incomplete understanding of the pathophysiology of FSHD in relation to the molecules leading to DUX4 gene activation and the downstream gene targets of DUX4 that cause its toxic effects. In the context of the local proximity of chromosome 4q to the nuclear envelope, a contraction of the D4Z4 macrosatellite induces lower methylation levels, enabling the ectopic expression of DUX4. This disrupts numerous signalling pathways that mostly result in cell death, detrimentally affecting skeletal muscle in affected individuals. In this regard different options are currently explored either to suppress the transcription of DUX4 gene, inhibiting DUX4 protein from its toxic effects, or to alleviate the symptoms triggered by its numerous targets.

CLIA Laboratory Testing for Facioscapulohumeral Dystrophy: A Retrospective Analysis

Objective

To summarize facioscapulohumeral muscular dystrophy (FSHD) diagnostic testing results from the University of Iowa Molecular Pathology Laboratory.

Methods

All FSHD tests performed in the diagnostic laboratory from January 2015 to July 2019 were retrospectively reviewed. Testing was by restriction enzyme digestion and Southern blot analysis with sequencing of SMCHD1, if indicated. Cases were classified as FSHD1 (4q35 EcoRI size ≤40 kb; 1–10 D4Z4 repeats), FSHD2 (permissive 4q35A allele, D4Z4 hypomethylation, and pathogenic SMCHD1 variant), or non-FSHD1,2. We also noted cases with borderline EcoRI fragment size (41–43 kb; 11 D4Z4 repeats), cases that meet criteria for both FSHD1 and FSHD2, somatic mosaicism, and cases with hybrid alleles that add complexity to test interpretation.

Results

Of the 1,594 patients with FSHD tests included in the analysis, 703 (44.1%) were diagnosed with FSHD. Among these positive tests, 664 (94.5%) met criteria for FSHD1 and 39 (5.5%) met criteria for FSHD2. Of all 1,594 cases, 20 (1.3%) had a 4q35 allele of borderline size, 23 (1.5%) were somatic mosaics, and 328 (20.9%) had undergone translocation events. Considering only cases with at least 1 4q35A allele, D4Z4 repeat number differed significantly among groups: FSHD1 cases median 6.0 (interquartile range [IQR] 4–7) repeats, FSHD2 cases 15.0 (IQR 12–22) repeats, and non-FSHD1,2 cases 28.0 (IQR 19–40) repeats.

Conclusion

FSHD1 accounts for 94.5% of genetically confirmed cases of FSHD. The data show a continuum of D4Z4 repeat numbers with FSHD1 samples having the fewest, FSHD2 an intermediate number, and non-FSHD1,2 the most.

Interpretation of the Epigenetic Signature of Facioscapulohumeral Muscular Dystrophy in Light of Genotype-Phenotype Studies

Facioscapulohumeral muscular dystrophy (FSHD) is characterized by incomplete penetrance and intra-familial clinical variability. The disease has been associated with the genetic and epigenetic features of the D4Z4 repetitive elements at 4q35. Recently, D4Z4 hypomethylation has been proposed as a reliable marker in the FSHD diagnosis. We exploited the Italian Registry for FSHD, in which FSHD families are classified using the Clinical Comprehensive Evaluation Form (CCEF). A total of 122 index cases showing a classical FSHD phenotype (CCEF, category A) and 110 relatives were selected to test with the receiver operating characteristic (ROC) curve, the diagnostic and predictive value of D4Z4 methylation. Moreover, we performed DNA methylation analysis in selected large families with reduced penetrance characterized by the co-presence of subjects carriers of one D4Z4 reduced allele with no signs of disease or presenting the classic FSHD clinical phenotype. We observed a wide variability in the D4Z4 methylation levels among index cases revealing no association with clinical manifestation or disease severity. By extending the analysis to family members, we revealed the low predictive value of D4Z4 methylation in detecting the affected condition. In view of the variability in D4Z4 methylation profiles observed in our large cohort, we conclude that D4Z4 methylation does not mirror the clinical expression of FSHD. We recommend that measurement of this epigenetic mark must be interpreted with caution in clinical practice.

Clinical and genetic features of somatic mosaicism in facioscapulohumeral dystrophy

PURPOSE

To analyse the clinical spectrum, genetic features, specific D4Z4 hypomethylation status and genotype-phenotype correlations for somatic mosaicism in facioscapulohumeral dystrophy (FSHD).

METHODS

This was a prospective, hospital-based, case-control, observational study of 35 participants with FSHD with somatic mosaicism recruited over 10 years, with 17 penetrant patients and 18 non-penetrant mutation carriers. This study also included a univariate comparison of 17 paired mosaic and non-mosaic patients with FSHD.

RESULTS

Mosaic participants with FSHD varied in age of diagnosis (median 45; range 15-65 years), muscle strength (FSHD clinical score median 0; range 0-10 points), clinical severity (age-corrected clinical severity score (ACSS) median 0; range 0-467 points), D4Z4 repeats (median 3; range 2-5 units), mosaic proportion (median 55%; range 27%-72%) and D4Z4 methylation extent (median 49.82%; range 27.17%-64.51%). The genotypic severity scale and D4Z4 methylation extent were significantly associated with ACSS (p₁=0.003; p₂=0.002). Among the matched pairs, the 17 mosaic patients had shorter D4Z4 repeats, lower FSHD clinical scores and lower ACSS than non-mosaic patients. Additionally, 34 of 35 (97%) participants carried two mosaic arrays, while a single patient had three mosaic arrays (3%). Two cases also carried four-type non-mosaic arrays on chromosome 10 (translocation configuration).

CONCLUSIONS

Broadly, this large mosaic FSHD cohort exhibited significant clinical heterogeneity and relatively slight disease severity. Both genotypic severity scale and D4Z4 hypomethylation status served as modifiers of clinical phenotypes. Consistent with previous reports, mitotic interchromosomal/intrachromosomal gene conversion without crossover was here identified as a major genetic mechanism underlying mosaic FSHD.

Strength training and aerobic exercise training for muscle disease

BACKGROUND

Strength training or aerobic exercise programmes, or both, might optimise muscle and cardiorespiratory function and prevent additional disuse atrophy and deconditioning in people with a muscle disease. This is an update of a review first published in 2004 and last updated in 2013. We undertook an update to incorporate new evidence in this active area of research.

OBJECTIVES

To assess the effects (benefits and harms) of strength training and aerobic exercise training in people with a muscle disease.

SEARCH METHODS

We searched Cochrane Neuromuscular's Specialised Register, CENTRAL, MEDLINE, Embase, and CINAHL in November 2018 and clinical trials registries in December 2018.

SELECTION CRITERIA

Randomised controlled trials (RCTs), quasi-RCTs or cross-over RCTs comparing strength or aerobic exercise training, or both lasting at least six weeks, to no training in people with a well-described muscle disease diagnosis.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 14 trials of aerobic exercise, strength training, or both, with an exercise duration of eight to 52 weeks, which included 428 participants with facioscapulohumeral muscular dystrophy (FSHD), dermatomyositis, polymyositis, mitochondrial myopathy, Duchenne muscular dystrophy (DMD), or myotonic dystrophy. Risk of bias was variable, as blinding of participants was not possible, some trials did not blind outcome assessors, and some did not use an intention-to-treat analysis. Strength training compared to no training (3 trials) For participants with FSHD (35 participants), there was low-certainty evidence of little or no effect on dynamic strength of elbow flexors (MD 1.2 kgF, 95% CI -0.2 to 2.6), on isometric strength of elbow flexors (MD 0.5 kgF, 95% CI -0.7 to 1.8), and ankle dorsiflexors (MD 0.4 kgF, 95% CI -2.4 to 3.2), and on dynamic strength of ankle dorsiflexors (MD -0.4 kgF, 95% CI -2.3 to 1.4). For participants with myotonic dystrophy type 1 (35 participants), there was very low-certainty evidence of a slight improvement in isometric wrist extensor strength (MD 8.0 N, 95% CI 0.7 to 15.3) and of little or no effect on hand grip force (MD 6.0 N, 95% CI -6.7 to 18.7), pinch grip force (MD 1.0 N, 95% CI -3.3 to 5.3) and isometric wrist flexor force (MD 7.0 N, 95% CI -3.4 to 17.4). Aerobic exercise training compared to no training (5 trials) For participants with DMD there was very low-certainty evidence regarding the number of leg revolutions (MD 14.0, 95% CI -89.0 to 117.0; 23 participants) or arm revolutions (MD 34.8, 95% CI -68.2 to 137.8; 23 participants), during an assisted six-minute cycle test, and very low-certainty evidence regarding muscle strength (MD 1.7, 95% CI -1.9 to 5.3; 15 participants). For participants with FSHD, there was low-certainty evidence of improvement in aerobic capacity (MD 1.1 L/min, 95% CI 0.4 to 1.8, 38 participants) and of little or no effect on knee extension strength (MD 0.1 kg, 95% CI -0.7 to 0.9, 52 participants). For participants with dermatomyositis and polymyositis (14 participants), there was very low-certainty evidence regarding aerobic capacity (MD 14.6, 95% CI -1.0 to 30.2). Combined aerobic exercise and strength training compared to no training (6 trials) For participants with juvenile dermatomyositis (26 participants) there was low-certainty evidence of an improvement in knee extensor strength on the right (MD 36.0 N, 95% CI 25.0 to 47.1) and left (MD 17 N 95% CI 0.5 to 33.5), but low-certainty evidence of little or no effect on maximum force of hip flexors on the right (MD -9.0 N, 95% CI -22.4 to 4.4) or left (MD 6.0 N, 95% CI -6.6 to 18.6). This trial also provided low-certainty evidence of a slight decrease of aerobic capacity (MD -1.2 min, 95% CI -1.6 to 0.9). For participants with dermatomyositis and polymyositis (21 participants), we found very low-certainty evidence for slight increases in muscle strength as measured by dynamic strength of knee extensors on the right (MD 2.5 kg, 95% CI 1.8 to 3.3) and on the left (MD 2.7 kg, 95% CI 2.0 to 3.4) and no clear effect in isometric muscle strength of eight different muscles (MD 1.0, 95% CI -1.1 to 3.1). There was very low-certainty evidence that there may be an increase in aerobic capacity, as measured with time to exhaustion in an incremental cycle test (17.5 min, 95% CI 8.0 to 27.0) and power performed at VO₂ max (maximal oxygen uptake) (18 W, 95% CI 15.0 to 21.0). For participants with mitochondrial myopathy (18 participants), we found very low-certainty evidence regarding shoulder muscle (MD -5.0 kg, 95% CI -14.7 to 4.7), pectoralis major muscle (MD 6.4 kg, 95% CI -2.9 to 15.7), and anterior arm muscle strength (MD 7.3 kg, 95% CI -2.9 to 17.5). We found very low-certainty evidence regarding aerobic capacity, as measured with mean time cycled (MD 23.7 min, 95% CI 2.6 to 44.8) and mean distance cycled until exhaustion (MD 9.7 km, 95% CI 1.5 to 17.9). One trial in myotonic dystrophy type 1 (35 participants) did not provide data on muscle strength or aerobic capacity following combined training. In this trial, muscle strength deteriorated in one person and one person had worse daytime sleepiness (very low-certainty evidence). For participants with FSHD (16 participants), we found very low-certainty evidence regarding muscle strength, aerobic capacity and VO₂ peak; the results were very imprecise. Most trials reported no adverse events other than muscle soreness or joint complaints (low- to very low-certainty evidence).

AUTHORS' CONCLUSIONS

The evidence regarding strength training and aerobic exercise interventions remains uncertain. Evidence suggests that strength training alone may have little or no effect, and that aerobic exercise training alone may lead to a possible improvement in aerobic capacity, but only for participants with FSHD. For combined aerobic exercise and strength training, there may be slight increases in muscle strength and aerobic capacity for people with dermatomyositis and polymyositis, and a slight decrease in aerobic capacity and increase in muscle strength for people with juvenile dermatomyositis. More research with robust methodology and greater numbers of participants is still required.

Rapid prenatal diagnosis of Facioscapulohumeral Muscular Dystrophy 1 by combined Bionano optical mapping and karyomapping

Purpose

To explore the feasibility of performing rapid prenatal diagnoses of FSHD1 using a combination of Bianano optical mapping and linkage‐based karyomapping.

Methods

DNA specimens from a family that had been previously diagnosed with FSHD1 using Southern Blot analysis were used for this study. Genetic diagnosis of the proband, fetus chorionic amniotic fluid, and aborted fetal tissue was performed using Bianano optical mapping (BOM) together with linkage‐based karyomapping.

Results

BOM analysis showed that the proband's 4q35.2 region contained four D4Z4 repeats and the 4qA permissible allele, consistent with the previous FSHD1 diagnosis obtained by Southern Blotting. BOM analysis of the fetus' 4q35.2 region was consistent with that of the proband. Karyomap analysis revealed that the fetus inherited the affected chromosome segment from the proband. After genetic counseling, the couple choose termination of pregnancy, and we performed gene diagnosis of the abortus tissue by BOM.

Conclusions

Bianano optical mapping can determine the number of D4Z4 repeats and exclude interference of the 10q26.3 homologous region, and in combination with karyomapping, can be used for rapid and accurate prenatal diagnosis of FSHD1.

Facioscapulohumeral Muscular Dystrophy

Facioscapulohumeral Muscular Dystrophy is a common form of muscular dystrophy that presents clinically with progressive weakness of the facial, scapular, and humeral muscles, with later involvement of the trunk and lower extremities. While typically inherited as autosomal dominant, facioscapulohumeral muscular dystrophy (FSHD) has a complex genetic and epigenetic etiology that has only recently been well described. The most prevalent form of the disease, FSHD1, is associated with the contraction of the D4Z4 microsatellite repeat array located on a permissive 4qA chromosome. D4Z4 contraction allows epigenetic derepression of the array, and possibly the surrounding 4q35 region, allowing misexpression of the toxic DUX4 transcription factor encoded within the terminal D4Z4 repeat in skeletal muscles. The less common form of the disease, FSHD2, results from haploinsufficiency of the SMCHD1 gene in individuals carrying a permissive 4qA allele, also leading to the derepression of DUX4, further supporting a central role for DUX4. How DUX4 misexpression contributes to FSHD muscle pathology is a major focus of current investigation. Misexpression of other genes at the 4q35 locus, including FRG1 and FAT1, and unlinked genes, such as SMCHD1, has also been implicated as disease modifiers, leading to several competing disease models. In this review, we describe recent advances in understanding the pathophysiology of FSHD, including the application of MRI as a research and diagnostic tool, the genetic and epigenetic disruptions associated with the disease, and the molecular basis of FSHD. We discuss how these advances are leading to the emergence of new approaches to enable development of FSHD therapeutics. © 2017 American Physiological Society. Compr Physiol 7:1229-1279, 2017.

Large family cohorts of lymphoblastoid cells provide a new cellular model for investigating facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is associated with aberrant epigenetic regulation of the chromosome 4q35 D4Z4 macrosatellite repeat. The resulting DNA hypomethylation and relaxation of epigenetic repression leads to increased expression of the deleterious DUX4-fl mRNA encoded within the distal D4Z4 repeat. With the typical late onset of muscle weakness, prevalence of asymptomatic individuals, and an autosomal dominant mode of inheritance, FSHD is often passed on from one generation to the next and affects multiple individuals within a family. Here we have characterized unique collections of 114 lymphoblastoid cell lines (LCLs) generated from 12 multigenerational FSHD families, including 56 LCLs from large, genetically homogeneous families in Utah. We found robust expression of DUX4-fl in most FSHD LCLs and a good correlation between DNA hypomethylation and repeat length. In addition, DUX4-fl levels can be manipulated using epigenetic drugs as in myocytes, suggesting that some epigenetic pathways regulating DUX4-fl in myocytes are maintained in LCLs. Overall, these FSHD LCLs provide an alternative cellular model in which to study many aspects of D4Z4, DUX4, and FSHD gene regulation in a background of low genetic variation. Significantly, these non-adherent immortal LCLs are amenable for high-throughput screening of potential therapeutics targeting DUX4-fl mRNA or protein expression.

Analyzing Copy Number Variation Using Pulsed-Field Gel Electrophoresis: Providing a Genetic Diagnosis for FSHD1

The myopathy facioscapulohumeral muscular dystrophy type 1 (FSHD1) is caused by copy number variation of the D4Z4 macrosatellite repeat on chromosome 4. In unaffected individuals the number of 3.3 kb D4Z4 units varies between 8 and 100, whereas 1-10 units are seen in FSHD1 cases. A homologous and heterogenous D4Z4 array can be found on chromosome 10q, but contractions of this array are typically not associated with FSHD. Discriminating between the chromosome 4 and chromosome 10 D4Z4 arrays, as well as determining the array size, requires the use of pulsed-field gel electrophoresis, Southern blotting, and the isolation of high-quality DNA.

Severe Glomerular Endothelial Injury Associated with a Short D4Z4 Repeat on Chromosome 4q35

The short D4Z4 repeat on chromosome 4q35 is a confirmatory genetic cause of facioscapulohumeral muscular dystrophy (FSHD), which presents with no renal complications. We herein report a five-year-old girl previously diagnosed with Coat's-like retinopathy, deafness, and mental retardation, who was found to have early-onset, severe FSHD. Despite the absence of muscle weakness, a Southern blot analysis showed a short D4Z4 repeat on chromosome 4q35. She presented with steroid-resistant nephrotic syndrome, and her renal histopathological findings were severe glomerular endothelial injury, which is a new complication associated with this genetic abnormality. Screening of renal complications may be necessary for FSHD patients. This patient requires close follow-up for her muscle symptoms.

Morpholino-mediated Knockdown of DUX4 Toward Facioscapulohumeral Muscular Dystrophy Therapeutics

Derepression of DUX4 in skeletal muscle has emerged as a likely cause of pathology in facioscapulohumeral muscular dystrophy (FSHD). Here we report on the use of antisense phosphorodiamidate morpholino oligonucleotides to suppress DUX4 expression and function in FSHD myotubes and xenografts. The most effective was phosphorodiamidate morpholino oligonucleotide FM10, which targets the polyadenylation signal of DUX4. FM10 had no significant cell toxicity, and RNA-seq analyses of FSHD and control myotubes revealed that FM10 down-regulated many transcriptional targets of DUX4, without overt off-target effects. Electroporation of FM10 into FSHD patient muscle xenografts in mice also down-regulated DUX4 and DUX4 targets. These findings demonstrate the potential of antisense phosphorodiamidate morpholino oligonucleotides as an FSHD therapeutic option.

New Insights into Genotype-phenotype Correlations in Chinese Facioscapulohumeral Muscular Dystrophy: A Retrospective Analysis of 178 Patients

Background:

Facioscapulohumeral muscular dystrophy (FSHD), a common autosomal dominant muscular disorder, is caused by contraction of the D4Z4 repeats on 4q35. The complicated genotype-phenotype correlation among different ethnic population remains a controversial subject. We aimed to refine this correlation in order to provide new information for genetic counseling.

Methods:

Here, a cohort of 136 Chinese families including 178 affected individuals and 137 unaffected members were investigated. Genetic analyses were performed using the p13E-11, 4qA and 4qB probes after pulsed field gel electrophoresis separation and southern blotting. A 10-grade FSHD clinical severity scale was adopted for clinical assessment. The genotype-phenotype correlation was established by linear regression analyses.

Results:

We observed a roughly inversed correlation between the short EcoRI fragment size and age-corrected clinical severity score in 154 symptomatic patients (P < 0.05). Compared to male patients, a significant higher proportion of females in both asymptomatic carriers and severe patients showed larger variation in the size of short EcoRI fragment. A high incidence (19/42, 45.2%) of asymptomatic (or minimally affected) carriers was found in familial members.

Conclusions:

Although the number of D4Z4 repeats is known as one of the critical influences on genotype-phenotype correlation, a majority of phenotypic spectrum was still incompatible with their heterozygous contraction of the D4Z4 repeat, especial in female cases. Our results suggest that there are multi-factors synergistically modulating the phenotypic expression.

Allele-specific DNA hypomethylation characterises FSHD1 and FSHD2

BACKGROUND

Facioscapulohumeral muscular dystrophy (FSHD) is associated with an epigenetic defect on 4qter. Two clinically indistinguishable forms of FSHD are known, FSHD1 and FSHD2. FSHD1 is caused by contraction of the highly polymorphic D4Z4 macrosatellite repeat array on chromosome 4q35. FSHD2 is caused by pathogenic mutations of the SMCHD1 gene.Both genetic defects lead to D4Z4 DNA hypomethylation. In the presence of a polymorphic polyadenylation signal (PAS), DNA hypomethylation leads to inappropriate expression of the D4Z4-encoded DUX4 transcription factor in skeletal muscle. Currently, hypomethylation is not diagnostic per se because of the interference of non-pathogenic arrays and the lack of information about the presence of DUX4-PAS.

METHODS

We investigated, by bisulfite sequencing, the DNA methylation levels of the region distal to the D4Z4 array selectively in PAS-positive alleles.

RESULTS

Comparison of FSHD1, FSHD2 and Control subjects showed a highly significant difference of methylation levels in all CpGs tested. Importantly, using a cohort of 112 samples, one of these CpGs (CpG6) is able to discriminate the affected individuals with a sensitivity of 0.95 supporting this assay potential for FSHD diagnosis. Moreover, our study showed a relationship between PAS-specific methylation and severity of the disease.

CONCLUSIONS

These data point to the CpGs distal to the D4Z4 array as a critical region reflecting multiple factors affecting the epigenetics of FSHD. Additionally, methylation analysis of this region allows the establishment of a rapid and sensitive tool for FSHD diagnosis.

Molecular combing compared to Southern blot for measuring D4Z4 contractions in FSHD

We compare molecular combing to Southern blot in the analysis of the facioscapulohumeral muscular dystrophy type 1 locus (FSHD1) on chromosome 4q35-qter (chr 4q) in genomic DNA specimens sent to a clinical laboratory for FSHD testing. A de-identified set of 87 genomic DNA specimens determined by Southern blot as normal (n = 71), abnormal with D4Z4 macrosatellite repeat array contractions (n = 7), indeterminate (n = 6), borderline (n = 2), or mosaic (n = 1) was independently re-analyzed by molecular combing in a blinded fashion. The molecular combing results were identical to the Southern blot results in 75 (86%) of cases. All contractions (n = 7) and mosaics (n = 1) detected by Southern blot were confirmed by molecular combing. Of the 71 samples with normal Southern blot results, 67 (94%) had concordant molecular combing results. The four discrepancies were either mosaic (n = 2), rearranged (n = 1), or borderline by molecular combing (n = 1). All indeterminate Southern blot results (n = 6) were resolved by molecular combing as either normal (n = 4), borderline (n = 1), or rearranged (n = 1). The two borderline Southern blot results showed a D4Z4 contraction on the chr 4qA allele and a normal result by molecular combing. Molecular combing overcomes a number of technical limitations of Southern blot by providing direct visualization of D4Z4 macrosatellite repeat arrays on specific chr 4q and chr 10q alleles and more precise D4Z4 repeat sizing. This study suggests that molecular combing has superior analytical validity compared to Southern blot for determining D4Z4 contraction size, detecting mosaicism, and resolving borderline and indeterminate Southern blot results. Further studies are needed to establish the clinical validity and diagnostic accuracy of these findings in FSHD.

Dominant lethal pathologies in male mice engineered to contain an X-linked DUX4 transgene

Facioscapulohumeral muscular dystrophy (FSHD) is an enigmatic disease associated with epigenetic alterations in the subtelomeric heterochromatin of the D4Z4 macrosatellite repeat. Each repeat unit encodes DUX4, a gene that is normally silent in most tissues. Besides muscular loss, most patients suffer retinal vascular telangiectasias. To generate an animal model, we introduced a doxycycline-inducible transgene encoding DUX4 and 3' genomic DNA into a euchromatic region of the mouse X chromosome. Without induction, DUX4 RNA was expressed at low levels in many tissues and animals displayed a variety of unexpected dominant leaky phenotypes, including male-specific lethality. Remarkably, rare live-born males expressed DUX4 RNA in the retina and presented a retinal vascular telangiectasia. By using doxycycline to induce DUX4 expression in satellite cells, we observed impaired myogenesis in vitro and in vivo. This mouse model, which shows pathologies due to FSHD-related D4Z4 sequences, is likely to be useful for testing anti-DUX4 therapies in FSHD.

Skeletal muscle imaging in facioscapulohumeral muscular dystrophy, pattern and asymmetry of individual muscle involvement

To better understand postural and movement disabilities, the pattern of total body muscle fat infiltration was analyzed in a large group of patients with facioscapulohumeral muscular dystrophy. Additionally, we studied whether residual D4Z4 repeat array length adjusted for age and gender could predict the degree of muscle involvement. Total body computed tomography scans of 70 patients were used to assess the degree of fat infiltration of 42 muscles from neck to ankle level on a semi-quantitative scale. Groups of muscles that highly correlated regarding fat infiltration were identified using factor analysis. Linear regression analysis was performed using muscle fat infiltration as the dependent variable and D4Z4 repeat length and age as independent variables. A pattern of muscle fat infiltration in facioscapulohumeral muscular dystrophy could be constructed. Trunk muscles were most frequently affected. Of these, back extensors were more frequently affected than previously reported. Asymmetry in muscle involvement was seen in 45% of the muscles that were infiltrated with fat. The right-sided upper extremity showed significantly higher scores for fat infiltration compared to the left side, which could not be explained by handedness. It was possible to explain 29% of the fat infiltration based on D4Z4 repeat length, corrected for age and gender. Based on our results we conclude that frequent involvement of fat infiltration in back extensors, in addition to the abdominal muscles, emphasizes the extent of trunk involvement, which may have a profound impact on postural control even in otherwise mildly affected patients.

Facioscapulohumeral dystrophy: the path to consensus on pathophysiology

Although the pathophysiology of facioscapulohumeral dystrophy (FSHD) has been controversial over the last decades, progress in recent years has led to a model that incorporates these decades of findings and is gaining general acceptance in the FSHD research community. Here we review how the contributions from many labs over many years led to an understanding of a fundamentally new mechanism of human disease. FSHD is caused by inefficient repeat-mediated epigenetic repression of the D4Z4 macrosatellite repeat array on chromosome 4, resulting in the variegated expression of the DUX4 retrogene, encoding a double-homeobox transcription factor, in skeletal muscle. Normally expressed in the testis and epigenetically repressed in somatic tissues, DUX4 expression in skeletal muscle induces expression of many germline, stem cell, and other genes that might account for the pathophysiology of FSHD. Although some disagreements regarding the details of mechanisms remain in the field, the coalescing agreement on a central model of pathophysiology represents a pivot-point in FSHD research, transitioning the field from discovery-oriented studies to translational studies aimed at developing therapies based on a sound model of disease pathophysiology.

Facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is characterized by a typical and asymmetric pattern of muscle involvement and disease progression. Two forms of FSHD, FSHD1 and FSHD2, have been identified displaying identical clinical phenotype but different genetic and epigenetic basis. Autosomal dominant FSHD1 (95% of patients) is characterized by chromatin relaxation induced by pathogenic contraction of a macrosatellite repeat called D4Z4 located on the 4q subtelomere (FSHD1 patients harbor 1 to 10 D4Z4 repeated units). Chromatin relaxation is associated with inappropriate expression of DUX4, a retrogene, which in muscles induces apoptosis and inflammation. Consistent with this hypothesis, individuals carrying zero repeat on chromosome 4 do not develop FSHD1. Not all D4Z4 contracted alleles cause FSHD. Distal to the last D4Z4 unit, a polymorphic site with two allelic variants has been identified: 4qA and 4qB. 4qA is in cis with a functional polyadenylation consensus site. Only contractions on 4qA alleles are pathogenic because the DUX4 transcript is polyadenylated and translated into stable protein. FSHD2 is instead a digenic disease. Chromatin relaxation of the D4Z4 locus is caused by heterozygous mutations in the SMCHD1 gene encoding a protein essential for chromatin condensation. These patients also harbor at least one 4qA allele in order to express stable DUX4 transcripts. FSHD1 and FSHD2 may have an additive effect: patients harboring D4Z4 contraction and SMCHD1 mutations display a more severe clinical phenotype than with either defect alone. Knowledge of the complex genetic and epigenetic defects causing these diseases is essential in view of designing novel therapeutic strategies. This article is part of a Special Issue entitled: Neuromuscular Diseases: Pathology and Molecular Pathogenesis.

Facioscapulohumeral Muscular Dystrophy: More Complex than it Appears

Facioscapulohumeral muscular dystrophy (FSHD) has been classified as an autosomal dominant myopathy, linked to rearrangements in an array of 3.3 kb tandemly repeated DNA elements (D4Z4) located at the 4q subtelomere (4q35). For the last 20 years, the diagnosis of FSHD has been confirmed in clinical practice by the detection of one D4Z4 allele with a reduced number (≤8) of repeats at 4q35. Although wide inter- and intra-familial clinical variability was found in subjects carrying D4Z4 alleles of reduced size, this DNA testing has been considered highly sensitive and specific. However, several exceptions to this general rule have been reported. Specifically, FSHD families with asymptomatic relatives carrying D4Z4 reduced alleles, FSHD genealogies with subjects affected with other neuromuscular disorders and FSHD affected patients carrying D4Z4 alleles of normal size have been described. In order to explain these findings, it has been proposed that the reduction of D4Z4 repeats at 4q35 could be pathogenic only in certain chromosomal backgrounds, defined as "permissive" specific haplotypes. However, our most recent studies show that the current DNA signature of FSHD is a common polymorphism and that in FSHD families the risk of developing FSHD for carriers of D4Z4 reduced alleles (DRA) depends on additional factors besides the 4q35 locus. These findings highlight the necessity to re-evaluate the significance and the predictive value of DRA, not only for research but also in clinical practice. Further clinical and genetic analysis of FSHD families will be extremely important for studies aiming at dissecting the complexity of FSHD.

Strength training and aerobic exercise training for muscle disease

BACKGROUND

Strength training or aerobic exercise programmes might optimise muscle and cardiorespiratory function and prevent additional disuse atrophy and deconditioning in people with a muscle disease. This is an update of a review first published in 2004.

OBJECTIVES

To examine the safety and efficacy of strength training and aerobic exercise training in people with a muscle disease.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register (July 2012), CENTRAL (2012 Issue 3 of 4), MEDLINE (January 1946 to July 2012), EMBASE (January 1974 to July 2012), EMBASE Classic (1947 to 1973) and CINAHL (January 1982 to July 2012).

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials comparing strength training or aerobic exercise programmes, or both, to no training, and lasting at least six weeks, in people with a well-described diagnosis of a muscle disease.We did not use the reporting of specific outcomes as a study selection criterion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted the data obtained from the full text-articles and from the original investigators. We collected adverse event data from included studies.

MAIN RESULTS

We included five trials (170 participants). The first trial compared the effect of strength training versus no training in 36 people with myotonic dystrophy. The second trial compared aerobic exercise training versus no training in 14 people with polymyositis and dermatomyositis. The third trial compared strength training versus no training in a factorial trial that also compared albuterol with placebo, in 65 people with facioscapulohumeral muscular dystrophy (FSHD). The fourth trial compared combined strength training and aerobic exercise versus no training in 18 people with mitochondrial myopathy. The fifth trial compared combined strength training and aerobic exercise versus no training in 35 people with myotonic dystrophy type 1.In both myotonic dystrophy trials and the dermatomyositis and polymyositis trial there were no significant differences between training and non-training groups for primary and secondary outcome measures. The risk of bias of the strength training trial in myotonic dystrophy and the aerobic exercise trial in polymyositis and dermatomyositis was judged as uncertain, and for the combined strength training and aerobic exercise trial, the risk of bias was judged as adequate. In the FSHD trial, for which the risk of bias was judged as adequate, a +1.17 kg difference (95% confidence interval (CI) 0.18 to 2.16) in dynamic strength of elbow flexors in favour of the training group reached statistical significance. In the mitochondrial myopathy trial, there were no significant differences in dynamic strength measures between training and non-training groups. Exercise duration and distance cycled in a submaximal endurance test increased significantly in the training group compared to the control group. The differences in mean time and mean distance cycled till exhaustion between groups were 23.70 min (95% CI 2.63 to 44.77) and 9.70 km (95% CI 1.51 to 17.89), respectively. The risk of bias was judged as uncertain. In all trials, no adverse events were reported.

AUTHORS' CONCLUSIONS

Moderate-intensity strength training in myotonic dystrophy and FSHD and aerobic exercise training in dermatomyositis and polymyositis and myotonic dystrophy type I appear to do no harm, but there is insufficient evidence to conclude that they offer benefit. In mitochondrial myopathy, aerobic exercise combined with strength training appears to be safe and may be effective in increasing submaximal endurance capacity. Limitations in the design of studies in other muscle diseases prevent more general conclusions in these disorders.

Focal and other unusual presentations of facioscapulohumeral muscular dystrophy

INTRODUCTION

Facioscapulohumeral dystrophy (FSHD) presents classically with facial and shoulder-girdle weakness. We report focal atypical presentations of FSHD. Our aim was to identify focal/unusual phenotypes in genetically confirmed FSHD cases.

METHODS

We undertook a retrospective review of an academic center database of the period from 1996 to 2011. Of 139 FSHD cases, 7 had atypical genetically confirmed disease. Clinical data were abstracted.

RESULTS

Seven cases (4 men) had a mean age of 37 years at onset (range 18-63 years) and mean 43 years at diagnosis (range 20-74 years). Presenting symptoms were monomelic lower limb (n = 3) or upper limb (n = 2) atrophy, or axial weakness (n = 2). Five patients had focal weakness on examination. CK was normal to borderline high. Two patients had a relative with FSHD. Coexistent unusual features included dyspnea (n = 1), S1 radicular pain with calf atrophy (n = 2), and peripheral neuropathy (n = 1). Almost all patients had myopathic EMG changes. DNA analysis showed a D4Z4 EcoRI fragment size ranging from 20 to 37 kilobases.

CONCLUSIONS

FSHD may present with focal weakness, dyspnea and myopathic EMG changes. These findings should raise the possibility of FSHD.

Compound heterozygosity in a South African patient with facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is characterised by weakness and atrophy of the facial and shoulder girdle muscles. The FSHD phenotype segregates as an autosomal dominant trait and is caused by a deletion of an integral number of 3.3 kilobase pair (kb) repeat units on chromosome 4q35. Haplotype and Southern blot analyses of chromosome 4 resulted in the detection of two BlnI resistant deletion fragments, of 24 kb and 34 kb respectively, in a single individual from a South African FSHD family. The patient had moderate facial weakness and marked winging and high-riding of the scapulae with prominent pectoral and proximal arm muscle atrophy and weakness. Quadriceps and anterior tibial muscles were weak and the patient had bilateral foot drop. Although none of his children were symptomatic yet and only two showed very mild clinical signs, one had inherited the 24 kb deletion fragment, while the other two had the 34 kb deletion fragment. Molecular analysis conclusively identified the first compound heterozygous case in the South African FSHD population. However, in accordance with other studies of compound heterozygotes and clinical findings, no direct correlation between the clinical severity of this patient and the number of deletion fragments was observed.

A long ncRNA links copy number variation to a polycomb/trithorax epigenetic switch in FSHD muscular dystrophy

Repetitive sequences account for more than 50% of the human genome. Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal-dominant disease associated with reduction in the copy number of the D4Z4 repeat mapping to 4q35. By an unknown mechanism, D4Z4 deletion causes an epigenetic switch leading to de-repression of 4q35 genes. Here we show that the Polycomb group of epigenetic repressors targets D4Z4 in healthy subjects and that D4Z4 deletion is associated with reduced Polycomb silencing in FSHD patients. We identify DBE-T, a chromatin-associated noncoding RNA produced selectively in FSHD patients that coordinates de-repression of 4q35 genes. DBE-T recruits the Trithorax group protein Ash1L to the FSHD locus, driving histone H3 lysine 36 dimethylation, chromatin remodeling, and 4q35 gene transcription. This study provides insights into the biological function of repetitive sequences in regulating gene expression and shows how mutations of such elements can influence the progression of a human genetic disease.

Patients with a phenotype consistent with facioscapulohumeral muscular dystrophy display genetic and epigenetic heterogeneity

OBJECTIVE

To identify the genetic and epigenetic defects in patients presenting with a facioscapulohumeral (FSHD) clinical phenotype without D4Z4 contractions on chromosome 4q35 tested by linear gel electrophoresis and Southern blot analysis.

DESIGN AND PATIENTS

The authors studied 16 patients displaying an FSHD-like phenotype, with normal cardiovascular and respiratory function, a myopathic pattern on electromyography, and a muscle biopsy being normal or displaying only mild and aspecific dystrophic changes. They sequenced the genes calpain 3 (CAPN3), valosin containing protein (VCP) and four-and-a-half LIM domains protein 1 (FHL1), and they analysed the D4Z4 repeat arrays by extensive genotyping and DNA methylation analysis.

RESULTS

The authors identified one patient carrying a complex rearrangement in the FSHD locus that masked the D4Z4 contraction associated with FSHD1 in standard genetic testing, one patient with somatic mosaicism for the D4Z4 4q35 contraction, six patients that were diagnosed as having FSHD2, four patients with CAPN3 mutations and two patients with a VCP mutation, No mutations were detected in FHL1, and in two patients, the authors could not identify the genetic defect.

CONCLUSIONS

In patients presenting with an FSHD-like clinical phenotype with a negative molecular testing for FSHD, consider (1) detailed genetic testing including D4Z4 contraction of permissive hybrid D4Z4 repeat arrays, p13E-11 probe deletions, and D4Z4 hypomethylation in the absence of repeat contraction as observed in FSHD2; (2) mutations in CAPN3 even in the absence of protein deficiency on western blot analysis; and (3) VCP mutations even in the absence of cognitive impairment, Paget disease and typical inclusion in muscle biopsy.

Camptocormia phenotype of FSHD: a clinical and MRI study on six patients

Recently it has been postulated that there is an atypical facioscapulohumeral muscular dystrophy (FSHD) phenotype with isolated axial myopathy. Involvement of paraspinal and limb muscles was evaluated in six patients with molecularly proven FSHD and a predominant bent spine phenotype. Consistent with the camptocormia phenotype, the most severely affected muscles in all six patients were the thoracic and lumbar spinal tract together with hamstrings. MRI disclosed severe axial muscle degeneration but mostly subclinical involvement of limb muscles. The involvement of hip extensor muscles in FSHD might considerably contribute to the clinical phenotype of camptocormia due to axial muscle involvement.

The cell biology of disease: FSHD: copy number variations on the theme of muscular dystrophy

In humans, copy number variations (CNVs) are a common source of phenotypic diversity and disease susceptibility. Facioscapulohumeral muscular dystrophy (FSHD) is an important genetic disease caused by CNVs. It is an autosomal-dominant myopathy caused by a reduction in the copy number of the D4Z4 macrosatellite repeat located at chromosome 4q35. Interestingly, the reduction of D4Z4 copy number is not sufficient by itself to cause FSHD. A number of epigenetic events appear to affect the severity of the disease, its rate of progression, and the distribution of muscle weakness. Indeed, recent findings suggest that virtually all levels of epigenetic regulation, from DNA methylation to higher order chromosomal architecture, are altered at the disease locus, causing the de-regulation of 4q35 gene expression and ultimately FSHD.

[Retinal involvement and genetic myopathy]

INTRODUCTION

In genetic diseases, association between retinal and muscular involvement is uncommon, quite specific and frequently allows the diagnosis. In this context, three types of retinal involvement have been described: retinitis pigmentosa (RP), pattern retinal dystrophy (PRD) and exudative retinitis resembling Coats disease (CD).

STATE OF THE ART

The association between RP, PRD and muscle weakness is highly evocative of a mitochondrial disorder. Extra ocular muscles may be affected, but limb girdle or distal weakness can also be present in association or not with symptoms and signs of multisystemic involvement. In a large number of patients suffering from facioscapulohumeral muscular dystrophy (FSHD), retinal vessels telangectasia can be found at the fundoscopic examination. This finding, which corresponds to a developmental abnormality of peripheral retinal blood vessels, is not progressive and remains clinically asymptomatic. Nevertheless, a few patients with FSHD can develop an exsudative retinopathy resembling Coats disease with the risk of the major complication, recurrent retinal detachments.

PERSPECTIVES AND CONCLUSIONS

Considering the diagnostic interest and the deleterious consequences that may follow retinal involvement, close collaboration between the neurologist and ophthalmologist is needed in order to establish the diagnosis, detect complications early, and set up appropriate therapies.

FSH dystrophy and a subtelomeric 4q haplotype: a new assay and associations with disease

BACKGROUND

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant disease associated with contraction of arrays of tandem 3.3-kb units (D4Z4) on subtelomeric 4q. Disease-linked arrays usually have fewer than 11 repeat units. Equally short D4Z4 arrays at subtelomeric 10q are not linked to FSHD. The newly described 4qA161 haplotype, which is more prevalent in pathogenic 4q alleles, involves sequences in and near D4Z4.

METHODS

We developed two new assays for 4qA161, which are based upon direct sequencing of PCR products or detecting restriction fragment length polymorphisms. They were used to analyse single nucleotide polymorphisms (SNPs) indicative of 4q161 alleles.

RESULTS

All (35/35) FSHD patients had one or two 4qA161 alleles (60% or 40%, respectively). In contrast, 46% (21/46) of control individuals had no 4qA161 allele (p<10(-4)), and 26% had homozygous 4qB163 alleles.

CONCLUSIONS

Our results from a heterogeneous population are consistent with the previously described association of the 4qA161 haplotype with FSHD, but a causal association with pathogenesis is uncertain. In addition, we found that haplotype analysis is complicated by the presence of minor 10q alleles. Nonetheless, our sequencing assay for the 4qA161allele can enhance molecular diagnosis of FSHD, including prenatal diagnosis, and is simpler to perform than the previously described assay.

Decreased nocturnal movements in patients with facioscapulohumeral muscular dystrophy

STUDY OBJECTIVES

Reduced mobility during sleep characterizes a variety of movement disorders and neuromuscular diseases. Facioscapulohumeral muscular dystrophy (FSHD) is the third most common form of muscular dystrophy in the general population, and people with FSHD have poor sleep quality. The aims of the present study were to evaluate nocturnal motor activity in patients with FSHD by means of videopolysomnography and to verify whether activity was associated with modifications in sleep structure.

METHODS

We enrolled 32 adult patients affected by genetically confirmed FSHD (18 women and 14 men, mean age 45.1 +/- 13.4 years) and 32 matched control subjects, (18 women and 14 men, mean age 45.5 +/- 11.4 years). Major body movements (MBM) were scored in videopolygraphic recordings in accordance with established criteria. An MBM index was calculated (number of MBM per hour of sleep).

RESULTS

The FSHD group showed a decrease in the MBM index (FSHD: 1.2 +/- 1.1; control subjects: 2.3 +/- 1.2, analysis of variance F = 13.672; p = 0.008). The sleep pattern of patients with FSHD, as compared with that of controls, was characterized by longer sleep latencies, shorter sleep durations, an increased percentage of wake during sleep, and a decreased percentage of rapid eye movement sleep. In the patient group, the MBM index was inversely correlated with severity of disease (Spearman test: r30 = -0.387; p < 0.05).

CONCLUSIONS

The present findings suggest that patients with FSHD have a reduced number of nocturnal movements, which is related to disease severity. Reduced movement in bed may contribute to the sleep modifications observed in these patients.

Worldwide population analysis of the 4q and 10q subtelomeres identifies only four discrete interchromosomal sequence transfers in human evolution

Subtelomeres are dynamic structures composed of blocks of homologous DNA sequences. These so-called duplicons are dispersed over many chromosome ends. We studied the human 4q and 10q subtelomeres, which contain the polymorphic macrosatellite repeat D4Z4 and which share high sequence similarity over a region of, on average, >200 kb. Sequence analysis of four polymorphic markers in the African, European, and Asian HAPMAP panels revealed 17 subtelomeric 4q and eight subtelomeric 10qter haplotypes. Haplotypes that are composed of a mixture of 4q and 10q sequences were detected at frequencies >10% in all three populations, seemingly supporting a mechanism of ongoing interchromosomal exchanges between these chromosomes. We constructed an evolutionary network of most haplotypes and identified the 4q haplotype ancestral to all 4q and 10q haplotypes. According to the network, all subtelomeres originate from only four discrete sequence-transfer events during human evolution, and haplotypes with mixtures of 4q- and 10q-specific sequences represent intermediate structures in the transition from 4q to 10q subtelomeres. Haplotype distribution studies on a large number of globally dispersed human DNA samples from the HGDP-CEPH panel supported our findings and show that all haplotypes were present before human migration out of Africa. D4Z4 repeat array contractions on the 4A161 haplotype cause Facioscapulohumeral muscular dystrophy (FSHD), whereas contractions on most other haplotypes are nonpathogenic. We propose that the limited occurrence of interchromosomal sequence transfers results in an accumulation of haplotype-specific polymorphisms that can explain the unique association of FSHD with D4Z4 contractions in a single 4q subtelomere.

Cephalometric findings in facioscapulohumeral muscular dystrophy patients with obstructive sleep apneas

PURPOSES

The purposes of the study are: (1) to establish if cephalometry and upper airway examination may provide tools for detecting facioscapulohumeral (FSHD) patients at risk for obstructive sleep apnea syndrome (OSAS); and (2) to correlate cephalometry and otorhinolaryngologic evaluation with clinical and polysomnographic features of FHSD patients with OSAS.

METHODS

Patients were 13 adults affected by genetically confirmed FSHD and OSAS, 11 men, with mean age 47.1 ± 12.8 years (range, 33-72 years). All underwent clinical evaluation, Manual Muscle Test, Clinical Severity Scale for FSHD, Epworth Sleepiness Scale, polysomnography, otorhinolaryngologic evaluation, and cephalometry.

RESULTS

Cephalometric evidence of pharyngeal narrowing [posterior airways space (PAS) < 10 mm] was present in only one patient. The mandibular planus and hyoid (MP-H) distance ranged from 6.5 to 33.1 mm (mean, 17.5 ± 7.8 mm). The mean length of soft palate (PNS-P) was 31.9 ± 4.8 mm (range, 22.2 to 39.7 mm). No patient presented an ANB angle > 7°. There was no significant correlation between cephalometric measures, clinical scores, and PSG indexes. PAS and MP-H were not related to the severity of the disease.

CONCLUSIONS

Upper airway morphological evaluation is of poor utility in the clinical assessment of FSHD patients and do not allow to predict the occurrence of sleep-related upper airway obstruction. This suggests that the pathogenesis of OSAS in FSHD is dependent on the muscular impairment, rather than to the anatomy of upper airways.

Strength training and aerobic exercise training for muscle disease

BACKGROUND

Strength training or aerobic exercise programmes might optimise muscle and cardiorespiratory function and prevent additional disuse atrophy and deconditioning in people with a muscle disease.

OBJECTIVES

To examine the safety and efficacy of strength training and aerobic exercise training in people with a muscle disease.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Specialized Register (July 2009), the Cochrane Rehabilitation and Related Therapies Field Register (October 2002, August 2008 and July 2009), The Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2009) MEDLINE (January 1966 to July 2009), EMBASE (January 1974 to July 2009), EMBASE Classic (1947 to 1973) and CINAHL (January 1982 to July 2009).

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials comparing strength training or aerobic exercise programmes, or both, to no training, and lasting at least 10 weeks.For strength training Primary outcome: static or dynamic muscle strength. Secondary: muscle endurance or muscle fatigue, functional assessments, quality of life, muscle membrane permeability, pain and experienced fatigue.For aerobic exercise training Primary outcome: aerobic capacity expressed as work capacity. Secondary: aerobic capacity (oxygen consumption, parameters of cardiac or respiratory function), functional assessments, quality of life, muscle membrane permeability, pain and experienced fatigue.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted the data.

MAIN RESULTS

We included three trials (121 participants). The first compared the effect of strength training versus no training in 36 people with myotonic dystrophy. The second trial compared strength training versus no training, both combined with albuterol or placebo, in 65 people with facioscapulohumeral muscular dystrophy. The third trial compared combined strength training and aerobic exercise versus no training in 18 people with mitochondrial myopathy. In the myotonic dystrophy trial there were no significant differences between training and non-training groups for primary and secondary outcome measures. In the facioscapulohumeral muscular dystrophy trial only a +1.17 kg difference (95% confidence interval 0.18 to 2.16) in dynamic strength of elbow flexors in favour of the training group reached statistical significance. In the mitochondrial myopathy trial there were no significant differences in dynamic strength measures between training and non-training groups. Exercise duration and distance cycled in a submaximal endurance test increased significantly in the training group compared to the control group.

AUTHORS' CONCLUSIONS

In myotonic dystrophy and facioscapulohumeral muscular dystrophy, moderate-intensity strength training appears not to do harm but there is insufficient evidence to conclude that it offers benefit. In mitochondrial myopathy, aerobic exercise combined with strength training appears to be safe and may be effective in increasing submaximal endurance capacity. Limitations in the design of studies in other muscle diseases prevent more general conclusions in these disorders.

Control of the upper body movements during level walking in patients with facioscapulohumeral dystrophy

Facioscapulohumeral dystrophy (FSHD) is a muscular disease usually spreading from upper to lower body and characterised by asymmetric muscle weakness. Walking ability is compromised in these patients, with a consequent high risk of falls. A quantitative analysis of the upper body oscillations may unveil useful information about the capacity of these patients to stabilise the head, maintain balance, and compensate for lower limb muscle weakness during walking. This study involved 13 patients with FSHD and 13 healthy volunteers. The trajectories of three points located on the cranio-caudal axis, at head, shoulder, and pelvis levels, during level walking, were analysed. The range of motion of these three points and the attenuation of the relevant accelerations going from pelvis to head level were used to describe the upper body movements during walking. The patients had wider and less symmetrical oscillations than the healthy controls both in antero-posterior and medio-lateral directions. Furthermore, the capacity of the patients to attenuate the accelerations going from pelvis to head level was reduced. These features may be related not only to upper body muscle weakness, but also to a strategy functional to the compensation of proximal leg muscle weakness. In conclusion, this study highlighted that the control of upper body oscillations and of head stability is reduced in patients with FSHD, suggesting that the assessment of the upper body movements should be included in the treatment decision process.

Quality of life and pain in patients with facioscapulohumeral muscular dystrophy

The aim of this study was to assess quality of life (QoL) and evaluate the occurrence and characteristics of pain in facioscapulohumeral muscular dystrophy (FSHD) patients. No study has yet assessed QoL in a large group of FSHD patients and, overall, few studies have assessed pain in neuromuscular diseases. We performed a prospective study using a multidimensional protocol including: clinical (according to the Clinical Severity Scale Rev1); genetic (p13E-11 EcoRI fragments Rev1); QoL (Short Form-36); pain (Visual Analog Scale and Portenoy-6 questions); and depression (Beck Depression Inventory) assessment. QoL measures of FSHD were compared with those of Italian norms. Moreover, we correlated QoL and pain measurements with clinical findings. Sixty-five patients were enrolled in the study. QoL was statistically significantly reduced with respect to the Italian normative sample, mainly in physical domains. Our study demonstrated that pain is frequent in FSHD patients. More than half of the patients complained of at least moderate pain. Women complained of slightly higher levels of deterioration in the emotional aspects of QoL than men. Clinical pattern (as assessed by Clinical Severity Scale) was closely related to physical QoL domains: the higher the clinical involvement, the more severe the QoL deterioration. This study provided information that may be crucial in clinical practice: pain may be a relevant aspect in FSHD patients, and prevention strategies or relevant therapies should be considered as appropriate. Moreover, we must pay more attention to gender differences: women can suffer far greater deterioration in the emotional aspects of QoL. Further multidimensional observations are needed. Muscle Nerve 40: 200-205, 2009.

Specific loss of histone H3 lysine 9 trimethylation and HP1gamma/cohesin binding at D4Z4 repeats is associated with facioscapulohumeral dystrophy (FSHD)

Facioscapulohumeral dystrophy (FSHD) is an autosomal dominant muscular dystrophy in which no mutation of pathogenic gene(s) has been identified. Instead, the disease is, in most cases, genetically linked to a contraction in the number of 3.3 kb D4Z4 repeats on chromosome 4q. How contraction of the 4qter D4Z4 repeats causes muscular dystrophy is not understood. In addition, a smaller group of FSHD cases are not associated with D4Z4 repeat contraction (termed "phenotypic" FSHD), and their etiology remains undefined. We carried out chromatin immunoprecipitation analysis using D4Z4-specific PCR primers to examine the D4Z4 chromatin structure in normal and patient cells as well as in small interfering RNA (siRNA)-treated cells. We found that SUV39H1-mediated H3K9 trimethylation at D4Z4 seen in normal cells is lost in FSHD. Furthermore, the loss of this histone modification occurs not only at the contracted 4q D4Z4 allele, but also at the genetically intact D4Z4 alleles on both chromosomes 4q and 10q, providing the first evidence that the genetic change (contraction) of one 4qD4Z4 allele spreads its effect to other genomic regions. Importantly, this epigenetic change was also observed in the phenotypic FSHD cases with no D4Z4 contraction, but not in other types of muscular dystrophies tested. We found that HP1gamma and cohesin are co-recruited to D4Z4 in an H3K9me3-dependent and cell type-specific manner, which is disrupted in FSHD. The results indicate that cohesin plays an active role in HP1 recruitment and is involved in cell type-specific D4Z4 chromatin regulation. Taken together, we identified the loss of both histone H3K9 trimethylation and HP1gamma/cohesin binding at D4Z4 to be a faithful marker for the FSHD phenotype. Based on these results, we propose a new model in which the epigenetic change initiated at 4q D4Z4 spreads its effect to other genomic regions, which compromises muscle-specific gene regulation leading to FSHD pathogenesis.

Sleep disordered breathing in facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most frequent forms of muscular dystrophy. The aims of this study were: 1) to evaluate the prevalence of sleep disordered breathing (SDB) in patients with FSHD; 2) to define the sleep-related respiratory patterns in FSHD patients with SDB; and 3) to find the clinical predictors of SDB. Fifty-one consecutive FSHD patients were enrolled, 23 women, mean age 45.7+/-12.3 years (range: 26-72). The diagnosis of FSHD was confirmed by genetic tests. All patients underwent medical and neurological evaluations, subjective evaluation of sleep and full-night laboratory-based polysomnography. Twenty patients presented SDB: 13 presented obstructive apneas, four presented REM related oxygen desaturations and three showed a mixed pattern. Three patients needed positive airways pressure. SDB was not related to the severity of the disease. Body mass index, neck circumference and daytime sleepiness did not allow prediction of SDB. In conclusion, the results suggest a high prevalence of SDB in patients with FSHD. The presence of SDB does not depend on the clinical severity of the disease. SDB is often asymptomatic, and no clinical or physical measure can reliably predict its occurrence. A screening of SDB should be included in the clinical assessment of FSHD.

Complex evolution of a Y-chromosomal double homeobox 4 (DUX4)-related gene family in hominoids

The human Y chromosome carries four human Y-chromosomal euchromatin/heterochromatin transition regions, all of which are characterized by the presence of interchromosomal segmental duplications. The Yq11.1/Yq11.21 transition region harbours a peculiar segment composed of an imperfectly organized tandem-repeat structure encoding four members of the double homeobox (DUX) gene family. By comparative fluorescence in situ hybridization (FISH) analysis we have documented the primary appearance of Y-chromosomal DUX genes (DUXY) on the gibbon Y chromosome. The major amplification and dispersal of DUXY paralogs occurred after the gibbon and hominid lineages had diverged. Orthologous DUXY loci of human and chimpanzee show a highly similar structural organization. Sequence alignment survey, phylogenetic reconstruction and recombination detection analyses of human and chimpanzee DUXY genes revealed the existence of all copies in a common ancestor. Comparative analysis of the circumjacent beta-satellites indicated that DUXY genes and beta-satellites evolved in concert. However, evolutionary forces acting on DUXY genes may have induced amino acid sequence differences in the orthologous chimpanzee and human DUXY open reading frames (ORFs). The acquisition of complete ORFs in human copies might relate to evolutionary advantageous functions indicating neo-functionalization. We propose an evolutionary scenario in which an ancestral tandem array DUX gene cassette transposed to the hominoid Y chromosome followed by lineage-specific chromosomal rearrangements paved the way for a species-specific evolution of the Y-chromosomal members of a large highly diverged homeobox gene family.