Facioscapulohumeral muscular dystrophy 1 patients participating in the UK FSHD registry can be subdivided into 4 patterns of self-reported symptoms.

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant incurable skeletal muscle disease. FSHD1 constitutes 95% of cases and is linked to truncation of the D4Z4 macrosatellite at 4q35. In most cases the condition initially presents with facial and proximal weakness of the upper limbs, but over the course of the disease involves lower limb and truncal muscles. Weakness is progressive and frequently asymmetric, which is a hallmark of the disease. Here we performed an analysis of 643 FSHD1 patients in the UK FSHD patient registry, investigating factors affecting rate of onset of 5 major FSHD symptoms: facial, periscapular, foot dorsiflexor, hip girdle weakness, and hearing loss. We found shorter D4Z4 repeat length associated with accelerated onset of each symptom. Furthermore, paternal inheritance of the pathogenic allele was associated with accelerated onset of foot dorsiflexor weakness, while pregnancy and carrying multiple children to term was associated with slower onset of all muscle symptoms. Lastly, we performed clustering analysis on age of onset of the 4 muscle symptoms across 222 patients. We identified 4 clinical presentations of FSHD1. A classical presentation (74%) and 3 facial sparing phenotypes: a mild presentation (5%) with later facial and periscapular involvement, an early shoulder presentation (10%) with accelerated periscapular weakness and an early foot presentation (9%) with accelerated foot dorsiflexor weakness. The mild presentation was associated with longer D4Z4 repeat lengths, while the early foot presentation had a female bias. We note, however that symptom progression differs significantly in these 4 clinical presentations independently of D4Z4 repeat length and gender, motivating investigation of further modifiers of FSHD1 severity.

Consequences of epigenetic derepression in facioscapulohumeral muscular dystrophy.

Facioscapulohumeral muscular dystrophy (FSHD), a common hereditary myopathy, is caused either by the contraction of the D4Z4 macrosatellite repeat at the distal end of chromosome 4q to a size of 1 to 10 repeat units (FSHD1) or by mutations in D4Z4 chromatin modifiers such as Structural Maintenance of Chromosomes Hinge Domain Containing 1 (FSHD2). These two genotypes share a phenotype characterized by progressive and often asymmetric muscle weakening and atrophy, and common epigenetic alterations of the D4Z4 repeat. All together, these epigenetic changes converge the two genetic forms into one disease and explain the derepression of the DUX4 gene, which is otherwise kept epigenetically silent in skeletal muscle. DUX4 is consistently transcriptionally upregulated in FSHD1 and FSHD2 skeletal muscle cells where it is believed to exercise a toxic effect. Here we provide a review of the recent literature describing the progress in understanding the complex genetic and epigenetic architecture of FSHD, with a focus on one of the consequences that these epigenetic changes inflict, the DUX4-induced immune deregulation cascade. Moreover, we review the latest therapeutic strategies, with particular attention to the potential of epigenetic correction of the FSHD locus.

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.

Inflammatory facioscapulohumeral muscular dystrophy type 2 in 18p deletion syndrome.

Facioscapulohumeral muscular dystrophy (FSHD) has been shown to be related to genetic and epigenetic derepression of DUX4 (mapping to chromosome 4), a gene located within a repeat array of D4Z4 sequences of polymorphic length. FSHD type 1 (FSHD1) is associated with pathogenic D4Z4 repeat array contraction, while FSHD type 2 (FSHD2) is associated with SMCHD1 variants (a chromatin modifier gene that maps to the short arm of chromosome 18). Both FSHD types require permissive polyadenylation signal (4qA) downstream of the D4Z4 array.

Design, set-up and utility of the UK facioscapulohumeral muscular dystrophy patient registry.

Facioscapulohumeral dystrophy (FSHD) is a rare inherited neuromuscular disease estimated to affect 1/15,000 people. Through basic research, remarkable progress has been made towards the development of targeted therapies. Patient identification, through registries or other means is essential for trial-readiness. The UK FSHD Patient Registry is a patient initiated registry that collects standardised and internationally agreed dataset of self-reported clinical details combined with professionally verified genetic information. It includes four additional questionnaires to capture patient reported outcomes related to pain, quality of life and scapular fixation. Between 2013 and 2015, 518 patients registered 243 males, 241 females with a mean age of 47.8 years. Most of the patients have FSHD type 1 (91.7 %), and weakness of the facial (59.2 %) was the most prevalent symptom at onset, followed by shoulder-girdle muscles (53.3 %) and distal (22.45 %) or proximal lower limb weakness (14.8 %). 85.57 % patients were ambulant or ambulant with assistance at the time of registration, 7.9 % report respiratory insufficiency. The registry has demonstrated utility with the recruitment of patients for a natural history study of infantile onset FSHD, and the longitudinal analysis of patient-related outcomes will provide much-needed baseline information to power future trials. The internationally agreed core dataset enables national registries to participate in a "Global FSHD registry". We suggest that the registry's ability to interoperate with other large datasets will be instrumental for sharing and exploiting data globally.

A novel clinical tool to classify facioscapulohumeral muscular dystrophy phenotypes.

Based on the 7-year experience of the Italian Clinical Network for FSHD, we revised the FSHD clinical form to describe, in a harmonized manner, the phenotypic spectrum observed in FSHD. The new Comprehensive Clinical Evaluation Form (CCEF) defines various clinical categories by the combination of different features. The inter-rater reproducibility of the CCEF was assessed between two examiners using kappa statistics by evaluating 56 subjects carrying the molecular marker used for FSHD diagnosis. The CCEF classifies: (1) subjects presenting facial and scapular girdle muscle weakness typical of FSHD (category A, subcategories A1-A3), (2) subjects with muscle weakness limited to scapular girdle or facial muscles (category B subcategories B1, B2), (3) asymptomatic/healthy subjects (category C, subcategories C1, C2), (4) subjects with myopathic phenotype presenting clinical features not consistent with FSHD canonical phenotype (D, subcategories D1, D2). The inter-rater reliability study showed an excellent concordance of the final four CCEF categories with a κ equal to 0.90; 95 % CI (0.71; 0.97). Absolute agreement was observed for categories C and D, an excellent agreement for categories A [κ = 0.88; 95 % CI (0.75; 1.00)], and a good agreement for categories B [κ = 0.79; 95 % CI (0.57; 1.00)]. The CCEF supports the harmonized phenotypic classification of patients and families. The categories outlined by the CCEF may assist diagnosis, genetic counseling and natural history studies. Furthermore, the CCEF categories could support selection of patients in randomized clinical trials. This precise categorization might also promote the search of genetic factor(s) contributing to the phenotypic spectrum of disease.

Double SMCHD1 variants in FSHD2: the synergistic effect of two SMCHD1 variants on D4Z4 hypomethylation and disease penetrance in FSHD2.

Facioscapulohumeral muscular dystrophy (FSHD) predominantly affects the muscles in the face, trunk and upper extremities and is marked by large clinical variability in disease onset and progression. FSHD is associated with partial chromatin relaxation of the D4Z4 repeat array on chromosome 4 and the somatic expression of the D4Z4 encoded DUX4 gene. The most common form, FSHD1, is caused by a contraction of the D4Z4 repeat array on chromosome 4 to a size of 1-10 units. FSHD2, the less common form of FSHD, is most often caused by heterozygous variants in the chromatin modifier SMCHD1, which is involved in the maintenance of D4Z4 methylation. We identified three families in which the proband carries two potentially damaging SMCHD1 variants. We investigated whether these variants were located in cis or in trans and determined their functional consequences by detailed clinical information and D4Z4 methylation studies. In the first family, both variants in trans were shown to act synergistically on D4Z4 hypomethylation and disease penetrance, in the second family both SMCHD1 function-affecting variants were located in cis while in the third family one of the two variants did not affect function. This study demonstrates that having two SMCHD1 missense variants that affect function is compatible with life in males and females, which is remarkable considering its role in X inactivation in mice. The study also highlights the variability in SMCHD1 variants underlying FSHD2 and the predictive value of D4Z4 methylation analysis in determining the functional consequences of SMCHD1 variants of unknown significance.

Inter-individual differences in CpG methylation at D4Z4 correlate with clinical variability in FSHD1 and FSHD2.

Facioscapulohumeral muscular dystrophy (FSHD: MIM#158900) is a common myopathy with marked but largely unexplained clinical inter- and intra-familial variability. It is caused by contractions of the D4Z4 repeat array on chromosome 4 to 1-10 units (FSHD1), or by mutations in the D4Z4-binding chromatin modifier SMCHD1 (FSHD2). Both situations lead to a partial opening of the D4Z4 chromatin structure and transcription of D4Z4-encoded polyadenylated DUX4 mRNA in muscle. We measured D4Z4 CpG methylation in control, FSHD1 and FSHD2 individuals and found a significant correlation with the D4Z4 repeat array size. After correction for repeat array size, we show that the variability in clinical severity in FSHD1 and FSHD2 individuals is dependent on individual differences in susceptibility to D4Z4 hypomethylation. In FSHD1, for individuals with D4Z4 repeat arrays of 1-6 units, the clinical severity mainly depends on the size of the D4Z4 repeat. However, in individuals with arrays of 7-10 units, the clinical severity also depends on other factors that regulate D4Z4 methylation because affected individuals, but not non-penetrant mutation carriers, have a greater reduction of D4Z4 CpG methylation than can be expected based on the size of the pathogenic D4Z4 repeat array. In FSHD2, this epigenetic susceptibility depends on the nature of the SMCHD1 mutation in combination with D4Z4 repeat array size with dominant negative mutations being more deleterious than haploinsufficiency mutations. Our study thus identifies an epigenetic basis for the striking variability in onset and disease progression that is considered a clinical hallmark of FSHD.

Restrictive lung involvement in facioscapulohumeral muscular dystrophy.

INTRODUCTION: Few studies have evaluated the frequency or predisposing factors for respiratory involvement in facioscapulohumeral muscular dystrophy type 1 (FSHD1) and type 2 (FSHD2). METHODS: We performed a prospective cross-sectional observational study of 61 genetically confirmed FSHD participants (53 FSHD1 and 8 FSHD2). Participants underwent bedside pulmonary function testing in sitting and supine positions, a standard clinical history and physical assessment, and manual muscle testing. RESULTS: Restrictive respiratory involvement was suggested in 9.8% (95% confidence interval 2.4-17.3): 7.5% FSHD1 and 25.0% FSHD2 (P = 0.17). Participants with testing suggestive of restrictive lung involvement (n = 6) were more severely affected (P = 0.005), had weaker hip flexion (P = 0.0007), and were more likely to use a wheelchair (P = 0.01). CONCLUSIONS: Restrictive respiratory involvement should be considered in all moderate to severely affected FSHD patients with proximal lower extremity weakness. The higher frequency of restrictive lung disease in FSHD2 seen here requires confirmation in a larger cohort of FSHD2 patients.

Effective classification and gene expression profiling for the Facioscapulohumeral Muscular Dystrophy.

The Facioscapulohumeral Muscular Dystrophy (FSHD) is an autosomal dominant neuromuscular disorder whose incidence is estimated in about one in 400,000 to one in 20,000. No effective therapeutic strategies are known to halt progression or reverse muscle weakness and atrophy. It is known that the FSHD is caused by modifications located within a D4ZA repeat array in the chromosome 4q, while recent advances have linked these modifications to the DUX4 gene. Unfortunately, the complete mechanisms responsible for the molecular pathogenesis and progressive muscle weakness still remain unknown. Although there are many studies addressing cancer databases from a machine learning perspective, there is no such precedent in the analysis of the FSHD. This study aims to fill this gap by analyzing two specific FSHD databases. A feature selection algorithm is used as the main engine to select genes promoting the highest possible classification capacity. The combination of feature selection and classification aims at obtaining simple models (in terms of very low numbers of genes) capable of good generalization, that may be associated with the disease. We show that the reported method is highly efficient in finding genes to discern between healthy cases (not affected by the FSHD) and FSHD cases, allowing the discovery of very parsimonious models that yield negligible repeated cross-validation error. These models in turn give rise to very simple decision procedures in the form of a decision tree. Current biological evidence regarding these genes shows that they are linked to skeletal muscle processes concerning specific human conditions.

[Clinical and molecular diagnosis of facioscapulohumeral dystrophy type 1 (FSHD1) in 2012]. / Diagnostic clinique et moléculaire de la myopathie facioscapulo-humérale de type 1 (FSHD1) en 2012.

INTRODUCTION: Diagnosis of facioscapulohumeral dystrophy type 1 (FSHD1) is supported by a suggestive clinical presentation and associated with a heterozygous contraction of the D4Z4 repeat array on chromosome 4q35. STATE OF THE ART: The FSHD1 phenotype has a widely variable course with great inter- and intrafamilial heterogeneity. Three clinical forms can be distinguished: the classical phenotype associated with four to seven repeat units (RU) and a variable course, a severe infantile form with one to three RU, and a mild phenotype associated with borderline UR (8 to 10 RU). At the molecular level, for D4Z4 contraction to be pathogenic, it needs to occur on a specific chromosomal background, namely on the 4qA allelic variant of chromosome 4. In most cases, once FSHD is clinically suspected, the diagnosis can be genetically confirmed with a DNA test using Southern Blotting and hybridization to a set of probes. However, diagnosis of FSHD1 remains challenging. Firstly, some patients may present with an atypical phenotype with highly focal or unusual symptoms. Secondly, there are potential pitfalls in the genetic diagnosis of FSHD resulting in false positive or false negative results. In the absence of genetic confirmation, other investigations, mainly EMG and muscle biopsy, are needed to rule out another diagnosis. In cases with no clear diagnosis and a permissive chromosome without contraction, FSHD2 may be suspected. PERSPECTIVES: Molecular combing is a new technique which permits visualization and sizing of the D4Z4 repeat array on its genetic background on stretched single DNA fibers by fluorescence microscopy. This tool will improve genetic diagnosis in FSHD patients. CONCLUSION: Diagnosis of FSHD1 is mainly supported by clinical features. Clinicians need to be aware of unusual presentations of this disease. The wide spectrum of intrafamilial variability and the lack of good correlation between genotype and phenotype present challenges for genetic counseling and prognostication. More studies are needed concerning penetrance and genotype-phenotype correlation.

[Facioscapulohumeral muscular dystrophy type 2]. / Dystrophie musculaire facio-scapulo-humérale de type 2.

INTRODUCTION: In recent years, the advances of knowledge in clinical, genetic and epigenetic features of facioscapulohumeral muscular dystrophy (FSHD) allowed the identification of two forms of FSHD, the classical autosomal dominant FSHD type 1, and FSHD type 2 characterized by an identical clinical phenotype but associated with a different (epi)genetic defect. STATE OF THE ART: In the large majority of FSHD1 patients, the identification of D4Z4 pathogenic contraction on a permissive chromosome 4 is sufficient for diagnosis, while FSHD2 diagnosis is complicated by the fact that the genetic defect associated with this disease is not known yet and a complete D4Z4 genotype and a D4Z4 specific methylation test are required. Indeed, FSHD2 patients display a non-contracted D4Z4 allele on chromosomes 4, at least one permissive chromosome 4QA and a profound hypomethylation of both chromosomes 4 and 10. A common pathophysiological pathway has been hypothesized for FSHD1 and FSHD2 in order to explain the identical clinical phenotype and the highly similar epigenetic changes found in patients affected by these diseases. According to this hypothesis, chromatin relaxation - due to pathogenic D4Z4 contraction in FSHD1 patients, and to important hypomethylation of this locus in FSHD2 patients - would allow the last D4Z4 unit to encode for a toxic DUX4 transcript. This transcript would be stable only when encoded from a permissive chromosome 4 carrying a polyadenylation signal immediately distal to the last D4Z4 unit on chromosome 4. PERSPECTIVES: Since, to express clinical phenotype, FSHD2 patients have to carry both 4QA chromosome and hypomethylated D4Z4 on chromosomes 4 and 10, digenic transmission has been hypothesized for this disease. The identification of the gene(s) and the exact epigenetic pathway underlining this disease will be mandatory to increase the rate of diagnosis for FSHD2 patients and to confirm the hypothesis of a common FSHD1 and FSHD2 pathophysiological pathway involving DUX4 gene. CONCLUSIONS: The identification, among patients carrying a FSHD phenotype, of FSHD2, a new disease with distinct (epi)genetic features but having a common pathophysiological pathway with FSHD1, suggests the possibility of developping new therapeutic strategies suitable for both diseases.

Diagnosis by sequencing: correction of misdiagnosis from FSHD2 to LGMD2A by whole-exome analysis.

We studied and validated facioscapulohumeral muscular dystrophy (FSHD) samples from patients without a D4Z4 contraction (FSHD2 or 'phenotypic FSHD'). For this, we developed non-radioactive protocols to test D4Z4 allele constitution and DNA methylation, and applied these to samples from the Coriell Institute Cell Repository. The D4Z4 sizing showed two related subjects to have classic chromosome 4 contraction-dependent FSHD1. A third sample (GM17726) did not have a short chromosome 4 fragment, and had been assigned as non-4q FSHD (FSHD2). We tested D4Z4 haplotype and methylation for this individual but found both to be inconsistent with this diagnosis. Using exome sequencing, we identified two known pathogenic mutations in CAPN3 (Arg490Gln and Thr184Argfs(*)36), indicating a case of LGMD2A rather than FSHD. Our study shows how a wrong diagnosis can easily be corrected by whole-exome sequencing by constraining the variant analysis to candidate genes after the data have been generated. This new way of 'diagnosis by sequencing' is likely to become common place in genetic diagnostic laboratories. We also publish a digoxigenin-labeled Southern protocol to test D4Z4 methylation. Our data supports hypomethylation as a good epigenetic predictor for FSHD2. The non-radioactive protocol will help to make this assay more accessible to clinical diagnostic laboratories and the wider FSHD research community.

Clinical profile and molecular diagnosis in patients of facioscapulohumeral dystrophy from Indian subcontinent.

Facioscapulohumeral dystrophy (FSHD) is an autosomal dominant muscular dystrophy. We retrospectively studied three families (two Indian, one Nepalese) with 12 affected members (male:female-7:5). Mean age at onset of weakness was 17.63 + 5.48 years. Patients were classified according to muscle groups affected (F-face, S-scapula, H-humeral, PG-pelvic girdle, P-peroneal, A-loss of independent ambulation): FSH-A (2), four FSH (4), SH (3), FSH-PG (2) and one: F (1). Progression of weakness was classified as F>S>P>PG in eight cases, S> F>P in one, static in three. Eleven patients had electromyographic findings suggestive of myopathy and one had features of neurogenic involvement. Molecular diagnosis was done by southern blotting using probe p13E-11 after digestion of genomic DNA with EcoRI and/or EcoRI/BlnI for twelve patients and three unaffected relatives. No EcoRI fragment smaller than 35 Kb was seen in unaffected subjects. Size of EcoRI fragment varied between 17 kb to 27 kb in affected subjects and was constant for affected members of the same family. Molecular diagnosis by southern blotting has helped to provide genetic counseling for the families.

Facioscapulohumeral muscular dystrophy. Phenotype-genotype correlation in patients with borderline D4Z4 repeat numbers.

Facioscapulohumeral muscular dystrophy (FSHD) is associated with a decreased number of D4Z4 repeats on chromosome 4q35. Diagnostic difficulties arise from atypical clinical presentations and from an overlap in D4Z4 numbers between controls and FSHD individuals. Thus, a molecular genetic test result with a borderline D4Z4 number has its limitations for the clinician wanting to differentiate between the diagnosis of FSHD and a myopathy presenting with FSHD-like symptoms.To investigate this problem in more detail we conducted a systematic study of 39 unrelated FSHD patients with borderline D4Z4 repeat numbers and 102 healthy controls. Our aim was threefold: [1] to define the molecular diagnostic cut-off point between FSHD cases and the control population, [2] to describe the myopathic spectrum in patients with borderline D4Z4 repeat numbers and [3] to look for correlations between D4Z4 number and clinical severity. The results indicate that there is no definite D4Z4 diagnostic cut-off point separating FSHD, FSHD-like myopathies and controls. A broad myopathic spectrum with four phenotypes (typical FSHD, facial-sparing FSHD, FSHD with atypical features, non-FSHD muscle disease) was found in the borderline region. The expected correlation of D4Z4 repeat number and clinical severity was not found. Therefore the molecular test is of limited help to differentiate FSHD from FSHDlike muscle disorders when the D4Z4 number is n = >or= 8.

Facioscapulohumeral muscular dystrophy.

A decade's progress in facioscapulohumeral muscular dystrophy genetics has been marked by the discovery of novel genetic phenomena such as crossover of subtelomeric DNA between chromosomes 4 and 10 in normal individuals and by the recognition that the facioscapulohumeral muscular dystrophy deletion-mutation may cause a position variegation effect on more proximal DNA. The mutated DNA itself is probably not transcribed. Larger deletions tend to cause more severe disease. Antenatal diagnosis, based on detection of the short fragment of mutated DNA, is possible in between 95 and 100% of cases, depending on the precise nature of the parental facioscapulohumeral muscular dystrophy mutation. Yet remarkably, the nature of the gene product(s) of the affected proximal gene(s), as well as of the molecular pathogenesis of facioscapulohumeral muscular dystrophy muscle, retinal and cochlear disease, is completely unknown. Marked perivascular inflammation is often present in facioscapulohumeral muscular dystrophy muscle biopsies. The expression of facioscapulohumeral muscular dystrophy within reported monozygotic twinships differs greatly. This raises the question of whether variations in expression of the T-cell receptor gene repertoire or of other immune genes play an important modifying role in determining the severity of facioscapulohumeral muscular dystrophy. A focus on traditional scientific disciplines may now be appropriate. Symptomatic treatments, for instance of scapular winging and of lagophthalmos, are important, and timely photocoagulation of the retinal exudates which are a very rare, but real, complication of retinal telangiectasis can curtail visual loss. The results of collobarative trials of pharmacological agents such as albuterol which affect muscle mass and development are awaited.