Molecular genetics of facioscapulohumeral muscular dystrophy

Case report: Identification of facioscapulohumeral muscular dystrophy 1 in two siblings with normal phenotypic parents using optical genome mapping

Objective

Facioscapulohumeral muscular dystrophy type 1 (FSHD1) is one of the most common forms of autosomal-dominant muscular dystrophies characterized by variable disease penetrance due to shortened D4Z4 repeat units on 4q35. The molecular diagnosis of FSHD1 is usually made by Southern blotting, which is complex, time-consuming, and lacks clinical practicality. Therefore, in this study, optical genome mapping (OGM) is employed for the genetic diagnosis of FSHD1. Furthermore, epigenetic heterogeneity is determined from methylation analysis.

Methods

Genomic DNA samples from four members of the same family were subjected to whole-exome sequencing. OGM was used to identify structural variations in D4Z4, while sodium bisulfite sequencing helped identify the methylation levels of CpG sites in a region located distally to the D4Z4 array. A multidisciplinary team collected the clinical data, and comprehensive family analyses aided in the assessment of phenotypes and genotypes.

Results

Whole-exome sequencing did not reveal variants related to clinical phenotypes in the patients. OGM showed that the proband was a compound heterozygote for the 4qA allele with four and eight D4Z4 repeat units, whereas the affected younger brother had only one 4qA allele with four D4Z4 repeat units. Both the proband and her younger brother were found to display asymmetric weakness predominantly involving the facial, shoulder girdle, and upper arm muscles, whereas the younger brother had more severe clinical symptoms. The proband's father, who was found to be normal after a neurological examination, also carried the 4qA allele with eight D4Z4 repeat units. The unaffected mother exhibited 49 D4Z4 repeat units of the 4qA allele and a minor mosaic pattern with four D4Z4 repeat units of the 4qA allele. Consequently, the presence of the 4qA allele in the four D4Z4 repeat units strongly pointed to the occurrence of maternal germline mosaicism. The CpG6 methylation levels were lower in symptomatic patients compared to those in the asymptomatic parents. The older sister had lower clinical scores and ACSS and higher CpG6 methylation levels than that of her younger brother.

Conclusions

In this study, two siblings with FSHD1 with phenotypically normal parents were identified by OGM. Our findings suggest that the 4qA allele of four D4Z4 repeats was inherited through maternal germline mosaicism. The clinical phenotype heterogeneity is influenced by the CpG6 methylation levels. The results of this study greatly aid in the molecular diagnosis of FSHD1 and in also understanding the clinical phenotypic variability underlying the disease.

Epigenetic profiling of the D4Z4 locus: Optimization of the protocol for studying DNA methylation at single CpG site level

The alteration of epigenetic modifications, including DNA methylation, can contribute to the etiopathogenesis and progression of many diseases. Among them, facioscapulohumeral dystrophy (FSHD) is a muscular disorder characterized by the loss of repressive epigenetic features affecting the D4Z4 locus (4q35). As a consequence, these alterations are responsible for DNA hypomethylation and a transcriptional-active chromatin conformation change that, in turn, lead to the aberrant expression of DUX4 in muscle cells. In the present study, methylation levels of 29 CpG sites of the DR1 region (within each repeat unit of the D4Z4 macrosatellite) were assessed on 335 subjects by employing primers designed for enhancing the performance of the assay. First, the DR1 original primers were optimized by adding M13 oligonucleotide tails. Moreover, the DR1 reverse primer was replaced with a degenerate one. As a result, the protocol optimization allowed a better sequencing resolution and a more accurate evaluation of DR1 methylation levels. Moreover, the assessment of the repeatability of measurements proved the reliability and robustness of the assay. The optimized protocol emerges as an excellent method to detect methylation levels compatible with FSHD.

The FSHD muscle-blood biomarker: a circulating transcriptomic biomarker for clinical severity in facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is a prevalent, incurable skeletal myopathy. Clinical trials for FSHD are hindered by heterogeneous biomarkers poorly associated with clinical severity, requiring invasive muscle biopsy. Macroscopically, FSHD presents with slow fatty replacement of muscle, rapidly accelerated by inflammation. Mis-expression of the transcription factor DUX4 is currently accepted to underlie pathogenesis, and mechanisms including PAX7 target gene repression have been proposed. Here, we performed RNA-sequencing on MRI-guided inflamed and isogenic non-inflamed muscle biopsies from the same clinically characterized FSHD patients (n = 24), alongside isogenic peripheral blood mononucleated cells from a subset of patients (n = 13) and unaffected controls (n = 11). Multivariate models were employed to evaluate the clinical associations of five published FSHD transcriptomic biomarkers. We demonstrated that PAX7 target gene repression can discriminate control, inflamed and non-inflamed FSHD muscle independently of age and sex (P < 0.013), while the discriminatory power of DUX4 target genes was limited to distinguishing FSHD muscle from control. Importantly, the level of PAX7 target gene repression in non-inflamed muscle associated with clinical assessments of FSHD severity (P = 0.04). DUX4 target gene biomarkers in FSHD muscle showed associations with lower limb fat fraction and D4Z4 array length but not clinical assessment. Lastly, PAX7 target gene repression in FSHD muscle correlated with the level in isogenic peripheral blood mononucleated cells (P = 0.002). A refined PAX7 target gene biomarker comprising 143/601 PAX7 target genes computed in peripheral blood (the FSHD muscle-blood biomarker) associated with clinical severity in FSHD patients (P < 0.036). Our new circulating biomarker validates as a classifier of clinical severity in an independent data set of 54 FSHD patient and 29 matched control blood samples, with improved power in older patients (P = 0.03). In summary, we present the minimally invasive FSHD muscle-blood biomarker of FSHD clinical severity valid in patient muscle and blood, of potential use in routine disease monitoring and clinical trials.

Bilateral scapulothoracic arthrodesis for facioscapulohumeral muscular dystrophy: function, fusion, and respiratory consequences

BACKGROUND

Scapulothoracic arthrodesis (STA) has been proposed for the treatment of painful scapular winging in patients with facioscapulohumeral muscular dystrophy (FSHD). However, the rate of osseous fusion is variable, and there is a theoretical risk of reduced respiratory function after bilateral STA.

METHODS

This was a retrospective study of 10 STAs, performed sequentially, in 5 FSHD patients. The surgical technique involved use of a semitubular plate and wire construct with autograft (iliac crest) interposed between the scapula and rib cage. Osseous fusion, respiratory function, and shoulder function were evaluated. The mean follow-up period was 141 ± 67 months (range, 24-225 months).

RESULTS

Early complications included 1 pneumothorax and 1 pleural effusion. No late complications occurred, and no patients underwent reoperation. On postoperative computed tomography images, complete bony union of the scapula to the ribs was observed in 90% of shoulders (9 of 10). Comparison of preoperative and postoperative pulmonary function test results showed no significant difference in vital capacity (from 87% ± 14% to 85% ± 12%) and forced vital capacity (from 86% ± 16% to 77% ± 15%). Patients gained on average 40° of active forward elevation (from 62° ± 20° to 102° ± 4°) and 22° of abduction (from 58° ± 21° to 89° ± 7°) (P < .001). The mean Subjective Shoulder Value increased from 25% ± 8% to 72% ± 18% (P < .001). All patients were pleased with the results and would recommend the procedure to other persons.

CONCLUSION

In patients with FSHD, bilateral STA provides satisfactory shoulder function with a high rate of scapulothoracic fusion and few or no significant respiratory repercussions.

DUX4 Suppresses MHC Class I to Promote Cancer Immune Evasion and Resistance to Checkpoint Blockade

Advances in cancer immunotherapies make it critical to identify genes that modulate antigen presentation and tumor-immune interactions. We report that DUX4, an early embryonic transcription factor that is normally silenced in somatic tissues, is re-expressed in diverse solid cancers. Both cis-acting inherited genetic variation and somatically acquired mutations in trans-acting repressors contribute to DUX4 re-expression in cancer. Although many DUX4 target genes encode self-antigens, DUX4-expressing cancers were paradoxically characterized by reduced markers of anti-tumor cytolytic activity and lower major histocompatibility complex (MHC) class I gene expression. We demonstrate that DUX4 expression blocks interferon-γ-mediated induction of MHC class I, implicating suppressed antigen presentation in DUX4-mediated immune evasion. Clinical data in metastatic melanoma confirmed that DUX4 expression was associated with significantly reduced progression-free and overall survival in response to anti-CTLA-4. Our results demonstrate that cancers can escape immune surveillance by reactivating a normal developmental pathway and identify a therapeutically relevant mechanism of cell-intrinsic immune evasion.

The Genetics and Epigenetics of Facioscapulohumeral Muscular Dystrophy

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.

Clinical application of single-molecule optical mapping to a multigeneration FSHD1 pedigree

Introduction

Facioscapulohumeral muscular dystrophy 1 (FSHD1) is a relatively common autosomal dominant adult muscular dystrophy with variable disease penetrance. The disease is caused by shortening of a D4Z4 repeat array located near the telomere of chromosome 4 at 4q35. This causes activation of a dormant gene DUX4, permitting aberrant DUX4 expression which is toxic to muscles. Molecular diagnosis of FSHD1 by Southern blot hybridization or FISH combing is difficult and time consuming, requiring specialist laboratories. As an alternative, we apply a novel approach for the diagnosis of FSHD1 utilizing single‐molecule optical mapping (SMOM).

Methods

Long DNA molecules with BssS1 enzyme marking were subjected to SMOM on the Bionano Genomics platform to determine the number of D4Z4 repeats. Southern blot and molecular combing were used to confirm the FSHD1 haplotypes.

Results

In a study of a five‐generation FSHD1 pedigree, SMOM correctly diagnosed the disease and normal haplotypes, identifying the founder 4qA disease allele as having 4 D4Z4 repeat units. Southern blot and molecular combing analysis confirmed the SMOM results for the 4qA disease and 4qB nondisease alleles.

Conclusion

Based on our findings, we propose that SMOM is a reliable and accurate technique suitable for the molecular diagnosis of FSHD1.

Genotype and phenotype analysis of 43 Iranian facioscapulohumeral muscular dystrophy patients; Evidence for anticipation

Facioscapulohumeral muscular dystrophy (FSHD) is the third most common hereditary myopathy (prevalence 1/8300-1/20,000). It is typically characterized by progressive weakness of facial, scapular and humeral muscles. Pelvic, abdominal and lower limbs muscles may eventually be affected. FSHD is classified into two subgroups, FSHD1 and FSHD2. FSHD1 is due to a reduction in the copy number of D4Z4 macrosatellites on chromosome 4q35 (11-100 repeats in normal individuals and 1-10 repeats in patients), and FSHD2 is caused by mutations in SMCHD1 or DNMT3B. Here, we present clinical features and results of genetic analysis on 43 Iranian FSHD patients. Forty patients carried 2-7 D4Z4 repeats based on Southern blot analysis, thus confirming FSHD1 diagnosis in these patients. The number of patients with D4Z4 repeats in the range of 1-3, 4-6 and 7-9 were, respectively, 22, 17 and one. Patients with the lower number of D4Z4 repeats generally showed earlier onset and more severe disease presentations. Anticipation was observed in 14 multi-generational families. To the best of our knowledge, this is the first phenotype and genotype analysis of FSHD patients in the Iranian population. The results of this study will be beneficial for genetic counselling of FSHD patients and their families, and for the establishment of a simple affordable genetic test for Iranians as the majority of patients had 1-5 D4Z4 repeats.

Long-term follow-up of MRI changes in thigh muscles of patients with Facioscapulohumeral dystrophy: A quantitative study

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common hereditary muscular disorders. Currently FSHD has no known effective treatment and detailed data on the natural history are lacking. Determination of the efficacy of a given therapeutic approach might be difficult in FSHD given the slow and highly variable disease progression. Magnetic resonance imaging (MRI) has been widely used to qualitatively and quantitatively evaluate in vivo the muscle alterations in various neuromuscular disorders. The main aim of the present study was to investigate longitudinally the time-dependent changes occurring in thigh muscles of FSHD patients using quantitative MRI and to assess the potential relationships with the clinical findings. Thirty-five FSHD1 patients (17 females) were enrolled. Clinical assessment tools including manual muscle testing using medical research council score (MRC), and motor function measure (MFM) were recorded each year for a period ranging from 1 to 2 years. For the MRI measurements, we used a new quantitative index, i.e., the mean pixel intensity (MPI) calculated from the pixel-intensity distribution in T1 weighted images. The corresponding MPI scores were calculated for each thigh, for each compartment and for both thighs totally (MPI_total). The total mean pixel intensity (MPI_total) refers to the sum of each pixel signal intensity divided by the corresponding number of pixels. An increased MPI_total indicates both a raised fat infiltration together with a reduced muscle volume thereby illustrating disease progression. Clinical scores did not change significantly over time whereas MPI_total increased significantly from an initial averaged value of 39.6 to 41.1 with a corresponding rate of 0.62/year. While clinical scores and MPI_total measured at the start of the study were significantly related, no correlation was found between the rate of MPI_total and MRC sum score changes, MFM_total and MFM subscores. The relative rate of MPI_total change was 2.3% (0.5–4.3)/year and was significantly higher than the corresponding rates measured for MRCS 0% (0–1.7) /year and MFM_total 0% (0–2.0) /year (p = 0.000). On the basis of these results, we suggested that muscle MRI and more particularly the MPI_total index could be used as a reliable biomarker and outcome measure of disease progression. In slowly progressive myopathies such as FSHD, the MPI_total index might reveal subclinical changes, which could not be evidenced using clinical scales over a short period of time.

A complex interplay of genetic and epigenetic events leads to abnormal expression of the DUX4 gene in facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD), a prevalent inherited human myopathy, develops following a complex interplay of genetic and epigenetic events. FSHD1, the more frequent genetic form, is associated with: (1) deletion of an integral number of 3.3 Kb (D4Z4) repeated elements at the chromosomal region 4q35, (2) a specific 4q35 subtelomeric haplotype denominated 4qA, and (3) decreased methylation of cytosines at the 4q35-linked D4Z4 units. FSHD2 is most often caused by mutations at the SMCHD1 (Structural Maintenance of Chromosomes Hinge Domain 1) gene, on chromosome 18p11.32. FSHD2 individuals also carry the 4qA haplotype and decreased methylation of D4Z4 cytosines. Each D4Z4 unit contains a copy of the retrotransposed gene DUX4 (double homeobox containing protein 4). DUX4 gene functionality was questioned in the past because of its pseudogene-like structure, its location on repetitive telomeric DNA sequences (i.e. junk DNA), and the elusive nature of both the DUX4 transcript and the encoded protein, DUX4. It is now known that DUX4 is a nuclear-located transcription factor, which is normally expressed in germinal tissues. Aberrant DUX4 expression triggers a deregulation cascade inhibiting muscle differentiation, sensitizing cells to oxidative stress, and inducing muscle atrophy. A unifying pathogenic model for FSHD emerged with the recognition that the FSHD-permissive 4qA haplotype corresponds to a polyadenylation signal that stabilizes the DUX4 mRNA, allowing the toxic protein DUX4 to be expressed. This working hypothesis for FSHD pathogenesis highlights the intrinsic epigenetic nature of the molecular mechanism underlying FSHD as well as the pathogenic pathway connecting FSHD1 and FSHD2. Pharmacological control of either DUX4 gene expression or the activity of the DUX4 protein constitutes current potential rational therapeutic approaches to treat FSHD.

Muscle Quantitative MR Imaging and Clustering Analysis in Patients with Facioscapulohumeral Muscular Dystrophy Type 1

BACKGROUND

Facioscapulohumeral muscular dystrophy type 1 (FSHD1) is the third most common inherited muscular dystrophy. Considering the highly variable clinical expression and the slow disease progression, sensitive outcome measures would be of interest.

METHODS AND FINDINGS

Using muscle MRI, we assessed muscular fatty infiltration in the lower limbs of 35 FSHD1 patients and 22 healthy volunteers by two methods: a quantitative imaging (qMRI) combined with a dedicated automated segmentation method performed on both thighs and a standard T1-weighted four-point visual scale (visual score) on thighs and legs. Each patient had a clinical evaluation including manual muscular testing, Clinical Severity Score (CSS) scale and MFM scale. The intramuscular fat fraction measured using qMRI in the thighs was significantly higher in patients (21.9 ± 20.4%) than in volunteers (3.6 ± 2.8%) (p<0.001). In patients, the intramuscular fat fraction was significantly correlated with the muscular fatty infiltration in the thighs evaluated by the mean visual score (p<0.001). However, we observed a ceiling effect of the visual score for patients with a severe fatty infiltration clearly indicating the larger accuracy of the qMRI approach. Mean intramuscular fat fraction was significantly correlated with CSS scale (p ≤ 0.01) and was inversely correlated with MMT score, MFM subscore D1 (p ≤ 0.01) further illustrating the sensitivity of the qMRI approach. Overall, a clustering analysis disclosed three different imaging patterns of muscle involvement for the thighs and the legs which could be related to different stages of the disease and put forth muscles which could be of interest for a subtle investigation of the disease progression and/or the efficiency of any therapeutic strategy.

CONCLUSION

The qMRI provides a sensitive measurement of fat fraction which should also be of high interest to assess disease progression and any therapeutic strategy in FSHD1 patients.

Individual epigenetic status of the pathogenic D4Z4 macrosatellite correlates with disease in facioscapulohumeral muscular dystrophy

Background

Both forms of facioscapulohumeral muscular dystrophy (FSHD) are associated with aberrant epigenetic regulation of the chromosome 4q35 D4Z4 macrosatellite. Chromatin changes due to large deletions of heterochromatin (FSHD1) or mutations in chromatin regulatory proteins (FSHD2) lead to relaxation of epigenetic repression and increased expression of the deleterious double homeobox 4 (DUX4) gene encoded within the distal D4Z4 repeat. However, many individuals with the genetic requirements for FSHD remain asymptomatic throughout their lives. Here we investigated family cohorts of FSHD1 individuals who were either affected (manifesting) or without any discernible weakness (nonmanifesting/asymptomatic) and their unaffected family members to determine if individual epigenetic status and stability of repression at the contracted 4q35 D4Z4 array in myocytes correlates with FSHD disease.

Results

Family cohorts were analyzed for DNA methylation on the distal pathogenic 4q35 D4Z4 repeat on permissive A-type subtelomeres. We found DNA hypomethylation in FSHD1-affected subjects, hypermethylation in healthy controls, and distinctly intermediate levels of methylation in nonmanifesting subjects. We next tested if these differences in DNA methylation had functional relevance by assaying DUX4-fl expression and the stability of epigenetic repression of DUX4-fl in myogenic cells. Treatment with drugs that alter epigenetic status revealed that healthy cells were refractory to treatment, maintaining stable repression of DUX4, while FSHD1-affected cells were highly responsive to treatment and thus epigenetically poised to express DUX4. Myocytes from nonmanifesting subjects had significantly higher levels of DNA methylation and were more resistant to DUX4 activation in response to epigenetic drug treatment than cells from FSHD1-affected first-degree relatives containing the same contraction, indicating that the epigenetic status of the contracted D4Z4 array is reflective of disease.

Conclusions

The epigenetic status of the distal 4qA D4Z4 repeat correlates with FSHD disease; FSHD-affected subjects have hypomethylation, healthy unaffected subjects have hypermethylation, and nonmanifesting subjects have characteristically intermediate methylation. Thus, analysis of DNA methylation at the distal D4Z4 repeat could be used as a diagnostic indicator of developing clinical FSHD. In addition, the stability of epigenetic repression upstream of DUX4 expression is a key regulator of disease and a viable therapeutic target.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0072-6) contains supplementary material, which is available to authorized users.

Identifying diagnostic DNA methylation profiles for facioscapulohumeral muscular dystrophy in blood and saliva using bisulfite sequencing

Background

Facioscapulohumeral muscular dystrophy (FSHD) is linked to chromatin relaxation due to epigenetic changes at the 4q35 D4Z4 macrosatellite array. Molecular diagnostic criteria for FSHD are complex and involve analysis of high molecular weight (HMW) genomic DNA isolated from lymphocytes, followed by multiple restriction digestions, pulse-field gel electrophoresis (PFGE), and Southern blotting. A subject is genetically diagnosed as FSHD1 if one of the 4q alleles shows a contraction in the D4Z4 array to below 11 repeats, while maintaining at least 1 repeat, and the contraction is in cis with a disease-permissive A-type subtelomere. FSHD2 is contraction-independent and cannot be diagnosed or excluded by this common genetic diagnostic procedure. However, FSHD1 and FSHD2 are linked by epigenetic deregulation, assayed as DNA hypomethylation, of the D4Z4 array on FSHD-permissive alleles. We have developed a PCR-based assay that identifies the epigenetic signature for both types of FSHD, distinguishing FSHD1 from FSHD2, and can be performed on genomic DNA isolated from blood, saliva, or cultured cells.

Results

Samples were obtained from healthy controls or patients clinically diagnosed with FSHD, and include both FSHD1 and FSHD2. The genomic DNAs were subjected to bisulfite sequencing analysis for the distal 4q D4Z4 repeat with an A-type subtelomere and the DUX4 5’ promoter region. We compared genomic DNA isolated from saliva and blood from the same individuals and found similar epigenetic signatures. DNA hypomethylation was restricted to the contracted 4qA chromosome in FSHD1 patients while healthy control subjects were hypermethylated. Candidates for FSHD2 showed extreme DNA hypomethylation on the 4qA DUX4 gene body as well as all analyzed DUX4 5’ sequences. Importantly, our assay does not amplify the D4Z4 arrays with non-permissive B-type subtelomeres and accurately excludes the arrays with non-permissive A-type subtelomeres.

Conclusions

We have developed an assay to identify changes in DNA methylation on the pathogenic distal 4q D4Z4 repeat. We show that the DNA methylation profile of saliva reflects FSHD status. This assay can distinguish FSHD from healthy controls, differentiate FSHD1 from FSHD2, does not require HMW genomic DNA or PFGE, and can be performed on either cultured cells, tissue, blood, or saliva samples.

Electronic supplementary material

The online version of this article (doi:10.1186/1868-7083-6-23) contains supplementary material, which is available to authorized users.

Exercise in neuromuscular diseases

This article reviews the current knowledge regarding the benefits and contraindications of exercise on individuals with neuromuscular diseases (NMDs). Specific exercise prescriptions for individuals with NMDs do not exist because the evidence base is limited. Understanding the effect of exercise on individuals with NMDs requires the implementation of a series of multicenter, randomized controlled trials that are sufficiently powered and use reliable and valid outcome measures to assess the effect of exercise interventions-a major effort for each NMD. In addition to traditional measures of exercise efficacy, outcome variables should include measures of functional status and health-related quality of life.

Recommendations for the management of facioscapulohumeral muscular dystrophy in 2011

Facioscapulohumeral muscular dystrophy (FSHD) is a neuromuscular disease, characterized by an autosomal dominant mode of inheritance, facial involvement, and selectivity and asymmetry of muscle involvement. In general, FSHD typically presents before age 20 years. Usually, FSHD muscle involvement starts in the face and then progresses to the shoulder girdle, the humeral muscles and the abdominal muscles, and then the anterolateral compartment of the leg. Disease severity is highly variable and progression is very slow. About 20% of FSHD patients become wheelchair-bound. Lifespan is not shortened. The diagnosis of FSHD is based on a genetic test by which a deletion of 3.3kb DNA repeats (named D4Z4 and mapping to the subtelomeric region of chromosome 4q35) is identified. The progressive pattern of FSHD requires that the severity of symptoms as well as their physical, social and psychological impact be evaluated on a regular basis. A yearly assessment is recommended. Multidisciplinary management of FSHD--consisting of a combination of genetic counselling, functional assessment, an assessment by a physical therapist, prescription of symptomatic therapies and prevention of known complications of this disease--is required. Prescription of physical therapy sessions and orthopedic appliances are to be adapted to the patient's deficiencies and contractures.

Genetic counseling and testing for FSHD (facioscapulohumeral muscular dystrophy) in the Israeli population

Facioscapulohumeral muscular dystrophy (FSHD), is a dominantly inherited, late onset, progressive disease. At present, no treatment or prevention of symptoms are available. There is considerable clinical variability, even within families. The gene whose defect causes FSHD has not been identified, but molecular diagnosis can be made by analyzing D4Z4 repeat length on chromosome 4q35. The results can support or rule out the clinical diagnosis of FSHD, but there are also "gray zone", non-conclusive results. During the years 2000-6, 66 individuals (including 7 asymptomatic individuals), were tested in our institute for D4Z4 repeat number. In 77% of the cases the results were conclusive: two thirds of them supported a diagnosis of FSHD while in a third this diagnosis was ruled out. In 23% the results were in the gray zone. Cognitive involvement was rare, occurring only when the D4Z4 repeat size was very small (<15 kb). Maximal utilization of the existing molecular test for FSHD demands detailed clinical and family pedigree information. We recommend that comprehensive genetic counseling always be given before and after molecular testing for FSHD, in addition to the neurological follow-up. Presymptomatic testing should only be offered when complete molecular evaluation can be offered, including 4qA and 4qB variant analysis.

New multiplex PCR-based protocol allowing indirect diagnosis of FSHD on single cells: can PGD be offered despite high risk of recombination?

Molecular pathophysiology of facioscapulohumeral muscular dystrophy (FSHD) involves the heterozygous contraction of the number of tandemly repeated D4Z4 units at chromosome 4q35.2. FSHD is associated with a range of 1-10 D4Z4 units instead of 11-150 in normal controls. Several factors complicate FSHD molecular diagnosis, especially the cis-segregation of D4Z4 contraction with a 4qA allele, whereas D4Z4 shortening is silent both on alleles 4qB and 10q. Discrimination of pathogenic 4q-D4Z4 alleles from highly homologous 10q-D4Z4 arrays requires the use of the conventional Southern blot, which is not suitable at the single-cell level. Preimplantation genetic diagnosis (PGD) is a frequent request from FSHD families with several affected relatives. We aimed to develop a rapid and sensitive PCR-based multiplex approach on single cells to perform an indirect familial segregation study of pathogenic alleles. Among several available polymorphic markers at 4q35.2, the four most proximal (D4S2390, D4S1652, D4S2930 and D4S1523, <1.23 Mb) showing the highest heterozygote frequencies (67-91%) were selected. Five recombination events in the D4S2390-D4S1523 interval were observed among 144 meioses. In the D4S2390-D4Z4 interval, no recombination event occurred among 28 FSHD meioses. Instead, a particular haplotype segregated with both clinical and molecular status, allowing the characterization of an at-risk allele in each tested FSHD family (maximal LOD score 2.98 for theta=0.0). This indirect protocol can easily complement conventional techniques in prenatal diagnosis. Although our multiplex PCR-based approach technically fulfils guidelines for single-cell analysis, the relatively high recombination risk hampers its application to PGD.

Measurement of the functional status of patients with different types of muscular dystrophy

Muscular dystrophy (MD) comprises a group of diseases characterized by progressive muscle weakness that induces functional deterioration. Clinical management requires the use of a well-designed scale to measure patients' functional status. This study aimed to investigate the quality of the functional scales used to assess patients with different types of MD. The Brooke scale and the Vignos scale were used to grade arm and leg function, respectively. The Barthel Index was used to evaluate the function of daily living activity. We performed tests to assess the acceptability of these scales. The characteristics of the different types of MD are discussed. This was a multicenter study and included patients diagnosed with Duchenne muscular dystrophy (DMD) (classified as severely progressive MD), Becker muscular dystrophy (BMD), limb girdle muscular dystrophy (LGMD) and facioscapulohumeral muscular dystrophy (FSHD). BMD, LGMD, and FSHD were classified as slowly progressive MD. The results demonstrated that the Brooke scale was acceptable for grading arm function in DMD, but was unable to discriminate between differing levels of severity in slowly progressive MD. The floor effect was large for all types of slowly progressive MD (range, 20.0-61.9), and was especially high for BMD. The floor effect was also large for BMD (23.8%) and FSHD (50.0%) using the Vignos scale. Grades 6-8 of the Vignos scale were inapplicable because they included items involving the use of long leg braces for walking or standing, and some patients did not use long leg braces. In the Barthel Index, a ceiling effect was prominent for slowly progressive MD (58.9%), while a floor effect existed for DMD (17.9%). Among the slowly progressive MDs, FSHD patients had the best level of functioning; they had better leg function and their daily living activities were less affected than patients with other forms of slowly progressive MD. The results of this study demonstrate the acceptability of the different applications used for measuring functional status in patients with different types of MD. Some of the limitations of these measures as applied to MD should be carefully considered, especially in patients with slowly progressive MD. We suggest that these applications be used in combination with other measures, or that a complicated instrument capable of evaluating the various levels of functional status be used.

Rehabilitation management of neuromuscular disease: the role of exercise training

This paper summarizes the current state of knowledge regarding exercise and neuromuscular diseases/disorders (NMDs) and reviews salient studies in the literature. Unfortunately, there is inadequate evidence in much of the NMDs to make specific recommendations regarding exercise prescriptions. This review focuses on the role of exercise in a few of the specific NMDs where most research has taken place and recommends future research directions.

The biological effects of simple tandem repeats: lessons from the repeat expansion diseases

Tandem repeats are common features of both prokaryote and eukaryote genomes, where they can be found not only in intergenic regions but also in both the noncoding and coding regions of a variety of different genes. The repeat expansion diseases are a group of human genetic disorders caused by long and highly polymorphic tandem repeats. These disorders provide many examples of the effects that such repeats can have on many biological processes. While repeats in the coding sequence can result in the generation of toxic or malfunctioning proteins, noncoding repeats can also have significant effects including the generation of chromosome fragility, the silencing of the genes in which they are located, the modulation of transcription and translation, and the sequestering of proteins involved in processes such as splicing and cell architecture.

Classification and nomenclature of all human homeobox genes

Background

The homeobox genes are a large and diverse group of genes, many of which play important roles in the embryonic development of animals. Increasingly, homeobox genes are being compared between genomes in an attempt to understand the evolution of animal development. Despite their importance, the full diversity of human homeobox genes has not previously been described.

Results

We have identified all homeobox genes and pseudogenes in the euchromatic regions of the human genome, finding many unannotated, incorrectly annotated, unnamed, misnamed or misclassified genes and pseudogenes. We describe 300 human homeobox loci, which we divide into 235 probable functional genes and 65 probable pseudogenes. These totals include 3 genes with partial homeoboxes and 13 pseudogenes that lack homeoboxes but are clearly derived from homeobox genes. These figures exclude the repetitive DUX1 to DUX5 homeobox sequences of which we identified 35 probable pseudogenes, with many more expected in heterochromatic regions. Nomenclature is established for approximately 40 formerly unnamed loci, reflecting their evolutionary relationships to other loci in human and other species, and nomenclature revisions are proposed for around 30 other loci. We use a classification that recognizes 11 homeobox gene 'classes' subdivided into 102 homeobox gene 'families'.

Conclusion

We have conducted a comprehensive survey of homeobox genes and pseudogenes in the human genome, described many new loci, and revised the classification and nomenclature of homeobox genes. The classification scheme may be widely applicable to homeobox genes in other animal genomes and will facilitate comparative genomics of this important gene superclass.

Hybridization analysis of D4Z4 repeat arrays linked to FSHD

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant disease involving shortening of D4Z4, an array of tandem 3.3-kb repeat units on chromosome 4. These arrays are in subtelomeric regions of 4q and 10q and have 1-100 units. FSHD is associated with an array of 1-10 units at 4q35. Unambiguous clinical diagnosis of FSHD depends on determining the array length at 4q35, usually with the array-adjacent p13E-11 probe after pulsed-field or linear gel electrophoresis. Complicating factors for molecular diagnosis of FSHD are the phenotypically neutral 10q D4Z4 arrays, cross-hybridizing sequences elsewhere in the genome, deletions including the genomic p13E-11 sequence and part of D4Z4, translocations between 4q and 10q D4Z4 arrays, and the extremely high G + C content of D4Z4 arrays (73%). In this study, we optimized conditions for molecular diagnosis of FSHD with a 1-kb D4Z4 subfragment probe after hybridization with p13E-11. We demonstrate that these hybridization conditions allow the identification of FSHD alleles with deletions of the genomic p13E-11 sequence and aid in determination of the nonpathogenic D4Z4 arrays at 10q. Furthermore, we show that the D4Z4-like sequences present elsewhere in the genome are not tandemly arranged, like those at 4q35 and 10q26.

[Facioscapulohumeral myopathy and germinal mosaicism]

BACKGROUND

Germline mosaicism is now well known to account for recurrence of hereditary human disorders. Facioscapulohumeral muscular dystrophy is an autosomal dominant disorder; its locus has been identified in the telomeric region of chromosome 4 at the q35 band. It appears to have a high rate of mutation.

CASE REPORT

A young girl had presented from childhood signs of a severe form of facioscapulohumeral muscular dystrophy, but with no familial history. The diagnosis was ultimately confirmed at the age of 23 years by molecular studies evidencing the deletion. The same abnormality was sparsely found in the child's father who appeared to harbor the mutation as a germline mosaicism with no clinical expression.

CONCLUSION

This case illustrates the possibility of severe facioscapulohumeral muscular dystrophy and the dominant transmission of the disorder which may be clinically occult. It underlines the importance of molecular biology and the difficulties of genetic counselling.

Application of chromosome 4q35-qter marker (pFR-1) for DNA rearrangement of facioscapulohumeral muscular dystrophy patients in Taiwan

Facioscapulohumeral muscular dystrophy (FSHD) has been found to be linked to chromosome 4qter. A chromosome 4q35-ter marker, pFR-1 (subclone of the cosmid c51), has been recently isolated and used as a probe for mapping near, or within, the FSHD gene. To examine FSHD-associated DNA rearrangements in the Taiwan population, we used the pFR-1 probe to perform Southern blot analysis on 142 individuals, including 32 FSHD patients within 9 autosomal dominant families, five sporadic FSHD patients from 4 families (include one pair of twins), three sporadic scapuloperoneal syndrome (SPS) patients and two sporadic polymyositis patients with their unaffected parents, and 29 healthy controls. In 29 healthy individuals, 3 SPS and 2 polymyositis patients with their families, probe pFR-1 analysis revealed that all had polymorphic restriction fragments that were larger than 28 kb in length. All but 1 FSHD-affected individual had specific smaller EcoRI fragments (ranging in size from 10.5 to 27 kb). Two point linkage analysis between pFR-1 and the FSHD locus provided significant evidence for FSHD linkage (Z(max)=6.84). A similar smaller fragment was also present in 5 sporadic patients, while this smaller fragment could not be found in one of their parents. Identical EcoRI restriction fragment length polymorphism (RFLP) patterns linked to FSHD were shown in the monozygotic twins, even though they showed extreme variability in the expression of FSHD. We conclude that the pFR-1 probe is a tightly linked marker of FSHD and can be used to detect most DNA rearrangements associated with this disease in the Taiwan population. However, the same RFLP patterns may represent extreme variability in the expression of the FSHD gene.

Detection of the mutation in facioscapulohumeral muscular dystrophy patients

The gene responsible for facioscapulohumeral muscular dystrophy (FSHD) was mapped to chromosome 4q35 by linkage analyses. Recently, the probe p13E-11 derived from the cosmid clone 13E, which has been mapped to 4qter, detected a polymorphic EcoRI fragment, usually greater than 28 kb in normal individuals. In sporadic and familial FSHD patients, a specific shorter fragment, usually smaller than 28 kb, was found to cosegregate with FSHD. Two FSHD patients are presented here. Patient 1 is a sporadic case of FSHD with healthy parents. He had a de novo mutation identified by Southern blot analysis using the above-mentioned probe. Patient 2 is a typical familial FSHD patient clinically and histologically. A rearranged and shortened EcoRI fragment was identified by molecular analysis. Southern blot analysis using the probe p13E-11 also indicated a rearranged EcoRI fragment in both patients.

Molecular genetics of facioscapulohumeral muscular dystrophy (FSHD)

Facioscapulohumeral muscular dystrophy (FSHD; MIM 158900), is an autosomal dominant neuromuscular disorder. The disease is characterized by the weakness of the muscles of the face, upper-arm and shoulder girdle. The gene for FSHD has been mapped to 4q35 (FSHD1A) and is closely linked to D4F1O4S1, which detects two highly polymorphic loci (located at 4q35 and 10q26), with restriction enzyme EcoRI. The polymorphic EcoRI fragment detected with D4F1O4S1 is composed almost entirely of D4Z4 (3.3 kb) tandem repeats. In FSHD patients a deletion of the integral number of D4Z4 repeats generates a fragment which is usually smaller than 35 kb, whereas in normal controls, the size usually ranges from 50 to 300 kb. These 'small' EcoRI fragments segregate with FSHD in families but appear as de novo deletions in the majority of sporadic cases. Each 3.3 kb repeat contains two homeobox domains neither of which has yet been proven to encode a protein. D4Z4 is located adjacent to the 4q telomere and cross hybridizes to several different regions of the genome. Although D4Z4 probably does not encode a protein with any direct association to FSHD, a clear correlation has been shown between the deletion size at this locus and the age at onset of the disease in FSHD patients. In approximately 5-10% of FSHD families the disease locus is unlinked to 4q35 (locus designated FSHD1B), however, none of the non 4q35 loci for FSHD have yet been chromosomally located. Thus so far, only one gene, FRG1 (FSHD region gene 1) has been identified from the FSHD candidate region on 4q35. The apparent low level of expressed sequences from within this region, the integral deletions of D4Z4 repeats observed in FSHD patients and the close proximity of these repeats to the 4q telomere, all suggest that the disease may be the result of position effect variegation. To date, the molecular diagnosis of FSHD with D4F104S1 has been most secure in those families which are linked to other 4q35 markers. Recent studies based on the distinction of 4q35 fragments from those from 10q26 will facilitate molecular diagnosis. The pathophysiology and biochemical defect in FSHD still remains to be elucidated. The identification of the FSHD gene and characterization of the gene product will not only potentiate accurate diagnosis but may also unravel the complexities of the 4q35 FSHD region.

Recent advances in muscular dystrophies and myopathies

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Towards the finer mapping of facioscapulohumeral muscular dystrophy at 4q35: construction of a laser microdissection library

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal-dominant disorder which has been mapped to the 4q35 region. In order to saturate this distal 4q region with DNA markers, a laser-based chromosomal microdissection and microcloning procedure was used to construct a genomic library from the distal 20% of chromosome 4, derived from a single human metaphase spread. Of the 100 microclones analyzed from this library, 94 clones contained inserts sized from 80-800 bp, with an average size of 340 bp. Less than 20% of these clones hybridized to human repeat sequences. Seventy-two single-copy clones were further characterized by Southern blot hybridization against a DNA panel of somatic cell hybrids, containing various regions of chromosome 4. Forty-two clones mapped to chromosome 4, of which 8 clones mapped into the relevant 4q35 region. Twenty of these chromosome 4-specific clones were screened against "zoo-blots"; 11 clones, of which 3 mapped to 4q35, identified conserved sequences. This is the first report to describe the isolation of potential expressed sequences derived from the FSHD region. These chromosome region-specific microclones will be useful in the construction of the physical map of the region, the positional cloning of potential disease-associated genes, and the identification of additional polymorphic markers from within the distal 4q region.

DNA rearrangements in Japanese facioscapulohumeral muscular dystrophy patients: clinical correlations

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant muscular disorder in which the disease locus has been mapped to chromosome 4q35-qter. In most patients, the DNA rearrangements associated with FSHD have been found in the EcoRI fragment detected by the p13E-11 probe, and deletions of the 3.2 kb repeat units within the fragment are thought to cause the disease. To examine FSHD-associated DNA rearrangements in the Japanese population, we performed Southern blot analysis of the genomic DNA, using the p13E-11 and pFR-1 probes, in 158 Japanese individuals, including 38 FSHD patients from 19 families. We found that all but one (a possible affected recombinant) of the Japanese FSHD patients (97.4%) had specific smaller (< 28 kb) EcoRI fragments which cosegregated with the disease; this included four patients who had severe inflammatory changes in the muscle and eight patients with de novo DNA rearrangements. We found no FSHD patient who had a fragment larger than 28 kb. By contrast, only two of 35 Japanese controls (5.7%) had EcoRI fragments smaller than 28 kb. Our patients showed anticipation, i.e. decreased size of the EcoRI fragment in parallel with earlier onset of the disease (r = 0.531, P = 0.003, with younger age at onset in children (17.8 +/- 7.0) than their affected parents (31.5 +/- 14.8) (P = 0.019). However, since each family had a specific small EcoRI fragment associated with the disease, the differing clinical severity within a family cannot be explained by the size of the fragment alone.(ABSTRACT TRUNCATED AT 250 WORDS)

A scapular onset muscular dystrophy without facial involvement: possible allelism with facioscapulohumeral muscular dystrophy

A dominantly inherited muscular dystrophy with onset in the shoulder girdle and later progression to the lower limbs is described. The disorder was clinically distinguishable from known facioscapulohumeral, scapulohumeral and limb girdle syndromes. A 38 kb allele detected by probe p13E-11 (D4F104S1) segregated with the disease. Linkage analysis gave a maximum lod score of z = 1.61 at theta = 0.01 with the 4q35 markers D4S184 (affected only analysis z = 1.20 at theta = 0.01) suggesting probable allelism with facioscapulohumeral muscular dystrophy.