For Facioscapulohumeral Muscular Dystrophy Research Articles

Best practice guidelines on genetic diagnostics of facioscapulohumeral muscular dystrophy: Update of the 2012 guidelines.

The gold standard for facioscapulohumeral muscular dystrophy (FSHD) genetic diagnostic procedures was published in 2012. With the increasing complexity of the genetics of FSHD1 and 2, the increase of genetic testing centers, and the start of clinical trials for FSHD, it is crucial to provide an update on our knowledge of the genetic features of the FSHD loci and renew the international consensus on the molecular testing recommendations. To this end, members of the FSHD European Trial Network summarized the evidence presented during the 2022 ENMC meeting on Genetic diagnosis, clinical outcome measures, and biomarkers. The working group additionally invited genetic and clinical experts from the USA, India, Japan, Australia, South-Africa, and Brazil to provide a global perspective. Six virtual meetings were organized to reach consensus on the minimal requirements for genetic confirmation of FSHD1 and FSHD2. Here, we present the clinical and genetic features of FSHD, specific features of FSHD1 and FSHD2, pros and cons of established and new technologies (Southern blot in combination with either linear or pulsed-field gel electrophoresis, molecular combing, optical genome mapping, FSHD2 methylation analysis and FSHD2 genotyping), the possibilities and challenges of prenatal testing, including pre-implantation genetic testing, and the minimal requirements and recommendations for genetic confirmation of FSHD1 and FSHD2. This consensus is expected to contribute to current clinical management and trial-readiness for FSHD.

Outcomes of scapulothoracic fusion in patients with facioscapulohumeral dystrophy: a comparison of allograft versus autograft bone grafting.

Scapulothoracic (ST) fusion for facioscapulohumeral muscular dystrophy (FSHD) is an established treatment that corrects scapular instability, although it has high reported complication rates. The purpose of our study was to characterize the outcomes of ST fusion for FSHD in a large patient cohort and compare the outcomes based on bone graft type and fixation technique. Our hypothesis was that union rates would not differ by bone graft type during ST fusion. A retrospective chart review was undertaken to identify patients who underwent ST fusion at multiple institutions performed by a single surgeon between 2013 and 2019 with minimum 2-year follow-up. Patient demographic characteristics, surgical technique, time to union, complications, and clinical outcomes including patient-reported outcome measures were recorded. Univariate and multivariate statistical analyses including regression analyses were performed to compare preoperative and postoperative outcomes. A total of 50 patients with 54 ST fusions (bilateral in 4 patients) and an average follow-up period of 5.8 years (standard deviation, 1.6 years) were included for analysis. Active forward elevation (77° vs. 124°, P<.00001) and abduction (60° vs. 90°, P<.00001) both improved significantly after fusion. Average internal rotation after fusion was at spinal level L3-L4. The visual analog scale pain score (2.6 vs. 1.2, P<.00001), Subjective Shoulder Value score (33 vs. 76, P<.00001), and American Shoulder and Elbow Surgeons (ASES) score (41.8 vs. 76.1, P<.00001) all improved significantly postoperatively. Of the shoulders, 50% (27 of 54) received treatment with cerclage wires and 50% (27 of 54) received treatment with Luque wires. Femoral head allograft was used in 53.7% of shoulders (29 of 54), whereas iliac crest autograft was used in 46.3% (25 of 54). Average radiographic time to healing was 11.1 weeks (standard deviation, 3.2 weeks), with no incidence of nonunion, and did not significantly differ by bone graft type (P=.26) or technique (P=.20). The complication rate was 24.1%, including seroma (n=3), superficial infection (n=2), transient neurologic injury (n=2), hemothorax (n=1), rib fracture (n=1), pneumothorax (n=1), and shortness of breath (n=1), although none requiring reoperation. There was no significant difference in the rate of postoperative complications when compared by surgical technique (P=.81) and bone graft type (P=.93). There were no independently predictive factors influencing the rate of postoperative complications by multivariate regression. Regression analysis showed that the postoperative ASES score was independently associated with the preoperative ASES score (P<.0001), use of iliac crest autograft (P<.011), and presence of complications (P<.043). Patients receiving ST fusion for FSHD demonstrate globally improved active motion and patient-reported outcome measures. Fusion construct or type of bone graft does not affect time to union or complication rates. Surgeons should be aware of a relatively high complication rate in the early postoperative period.

Molecular therapies: present and future in neuromuscular diseases

The possibilities in the field of molecular therapies of neuromuscular diseases have rapidly developed in recent years. First compounds are already available in clinical practice and numerous other substances are in advanced phases of clinical trials. This article gives an exemplary overview of the current state of clinical research in molecular therapies of neuromuscular diseases. It also gives a view into the near future of the clinical application, including the challenges. Using Duchenne muscular dystrophy (DMD) and myotubular myopathy as examples, the principles of gene addition in monogenetic skeletal muscle diseases, which are already manifested in childhood are described. In addition to initial successes, the challenges and setbacks hindering the approval and regular clinical application of further compounds are demonstrated. Furthermore, the state of current clinical research in Becker-Kiener muscular dystrophy (BMD) and the numerous forms of limb-girdle muscular dystrophy (LGMD) are summarized. Numerous new therapeutic approaches and acorresponding outlook are also shown for facioscapulohumeral muscular dystrophy (FSHD), Pompe disease, and myotonic dystrophy. Clinical research in the field of molecular therapy of neuromuscular diseases is one of the pacesetters of modern precision medicine; however, challenges need to be seen, jointly addressed and overcome in the future.

Facioscapulohumeral dystrophy transcriptome signatures correlate with different stages of disease and are marked by different MRI biomarkers

With several therapeutic strategies for facioscapulohumeral muscular dystrophy (FSHD) entering clinical testing, outcome measures are becoming increasingly important. Considering the spatiotemporal nature of FSHD disease activity, clinical trials would benefit from non-invasive imaging-based biomarkers that can predict FSHD-associated transcriptome changes. This study investigated two FSHD-associated transcriptome signatures (DUX4 and PAX7 signatures) in FSHD skeletal muscle biopsies, and tested their correlation with a variety of disease-associated factors, including Ricci clinical severity score, disease duration, D4Z4 repeat size, muscle pathology scorings and functional outcome measures. It establishes that DUX4 and PAX7 signatures both show a sporadic expression pattern in FSHD-affected biopsies, possibly marking different stages of disease. This study analyzed two imaging-based biomarkers—Turbo Inversion Recovery Magnitude (TIRM) hyperintensity and fat fraction—and provides insights into their predictive power as non-invasive biomarkers for FSHD signature detection in clinical trials. Further insights in the heterogeneity of—and correlation between—imaging biomarkers and molecular biomarkers, as provided in this study, will provide important guidance to clinical trial design in FSHD. Finally, this study investigated the role of infiltrating non-muscle cell types in FSHD signature expression and detected potential distinct roles for two fibro-adipogenic progenitor subtypes in FSHD.

Multicolor Whole-Genome Mapping in Nanochannels for Genetic Analysis.

Analysis of structural variations (SVs) is important to understand mutations underlying genetic disorders and pathogenic conditions. However, characterizing SVs using short-read, high-throughput sequencing technology is difficult. Although long-read sequencing technologies are being increasingly employed in characterizing SVs, their low throughput and high costs discourage widespread adoption. Sequence motif-based optical mapping in nanochannels is useful in whole-genome mapping and SV detection, but it is not possible to precisely locate the breakpoints or estimate the copy numbers. We present here a universal multicolor mapping strategy in nanochannels combining conventional sequence-motif labeling system with Cas9-mediated target-specific labeling of any 20-base sequences (20mers) to create custom labels and detect new features. The sequence motifs are labeled with green fluorophores and the 20mers are labeled with red fluorophores. Using this strategy, it is possible to not only detect the SVs but also utilize custom labels to interrogate the features not accessible to motif-labeling, locate breakpoints, and precisely estimate copy numbers of genomic repeats. We validated our approach by quantifying the D4Z4 copy numbers, a known biomarker for facioscapulohumeral muscular dystrophy (FSHD) and estimating the telomere length, a clinical biomarker for assessing disease risk factors in aging-related diseases and malignant cancers. We also demonstrate the application of our methodology in discovering transposable long non-interspersed Elements 1 (LINE-1) insertions across the whole genome.

Rasch analysis to evaluate the motor function measure for patients with facioscapulohumeral muscular dystrophy.

Patient-relevant outcome measures for facioscapulohumeral muscular dystrophy (FSHD) are needed. The motor function measure (MFM) is an ordinal-based outcome measure for neuromuscular disorders, but its suitability to measure FSHD patients is questionable. Here, we performed Rasch analyses on MFM data from 194 FSHD patients to assess clinimetric properties in this patient group. Both the total scale and its three domains were analyzed (D1: standing position and transfers; D2: axial and proximal motor function; D3: distal motor function). Fit to the Rasch model, sample-item targeting, individual item fit, threshold ordering, sex- and age-based differential item functioning, response dependency and unidimensionality were assessed. Rasch analysis revealed multiple limitations of the MFM for FSHD, the most important being a large ceiling effect and suboptimal sample-item targeting, which were most pronounced for domains D2 and D3. There were disordered thresholds for most items, often resulting in items functioning in a dichotomous fashion. It was not possible to remodel the MFM into a Rasch-built interval scale. Remodeling of domain D1 into an interval scale with adequate fit statistics was achieved, but sample-item targeting remained suboptimal. Therefore, the MFM should be used with caution in FSHD patients, as it is not optimally suited to measure functional abilities in this patient group.

Deletion of the Williams Beuren syndrome critical region unmasks facioscapulohumeral muscular dystrophy

Among 1339 unrelated cases accrued by the Italian National Registry for facioscapulohumeral muscular dystrophy (FSHD), we found three unrelated cases who presented signs of Williams-Beuren Syndrome (WBS) in early childhood and later developed FSHD. All three cases carry the molecular defects associated with the two disorders. The rarity of WBS and FSHD, 1 in 7500 and 1 in 20,000 respectively, makes a random association of the two diseases unlikely. These cases open novel and unexpected interpretation of genetic findings. The nonrandom association of both FSHD and WBS points at a gene co-expression network providing hints for the identification of modules and functionally enriched pathways in the two conditions.

Applying genome-wide CRISPR-Cas9 screens for therapeutic discovery in facioscapulohumeral muscular dystrophy.

The emergence of CRISPR-Cas9 gene-editing technologies and genome-wide CRISPR-Cas9 libraries enables efficient unbiased genetic screening that can accelerate the process of therapeutic discovery for genetic disorders. Here, we demonstrate the utility of a genome-wide CRISPR-Cas9 loss-of-function library to identify therapeutic targets for facioscapulohumeral muscular dystrophy (FSHD), a genetically complex type of muscular dystrophy for which there is currently no treatment. In FSHD, both genetic and epigenetic changes lead to misexpression of DUX4, the FSHD causal gene that encodes the highly cytotoxic DUX4 protein. We performed a genome-wide CRISPR-Cas9 screen to identify genes whose loss-of-function conferred survival when DUX4 was expressed in muscle cells. Genes emerging from our screen illuminated a pathogenic link to the cellular hypoxia response, which was revealed to be the main driver of DUX4-induced cell death. Application of hypoxia signaling inhibitors resulted in increased DUX4 protein turnover and subsequent reduction of the cellular hypoxia response and cell death. In addition, these compounds proved successful in reducing FSHD disease biomarkers in patient myogenic lines, as well as improving structural and functional properties in two zebrafish models of FSHD. Our genome-wide perturbation of pathways affecting DUX4 expression has provided insight into key drivers of DUX4-induced pathogenesis and has identified existing compounds with potential therapeutic benefit for FSHD. Our experimental approach presents an accelerated paradigm toward mechanistic understanding and therapeutic discovery of a complex genetic disease, which may be translatable to other diseases with well-established phenotypic selection assays.

A Five-Year Longitudinal Study in Facioscapolohumeral Muscular Dystrophy: Assessment of Variables Influencing Disease Progression

Background: Reduction of tandemly arrayed D4Z4 repeats is diagnostic for facioscapulohumeral muscular dystrophy (FSHD). However, various clinical phenotypes have been observed in carriers of this molecular lesion. Currently their natural history is obscure. Methods: A prospective observational cohort study is conducted to quantify disease progression over five-year follow-up (2013-2016) in246 carriers of D4Z4 reduced alleles DRA with 1-10 RU from the Italian National Registry for FSHD recruited between January 10th, 2007 and December 20th, 2011. Participants were subdivided in probands (141, males 84) and relatives (105, males 52). Muscle impairment was measured as FSHD score and disease progression as ΔFSHD score. Clinical phenotypes were assessed and categorized on the basis of the Comprehensive Clinical Evaluation Form (CCEF). Findings: The highest ΔFSHD score (1·7) was found in subjects with full FSHD phenotype (category A) or with complex/atypical diseases (category D); subjects with incomplete clinical phenotype (category B) had lower ΔFSHD score (0·6, p<0.0001). Of 97subjects with mild or no disability (FSHD score 0-2) at baseline 63 (64·9%) maintained the same FSHD score (ΔFSHD score 0); 79·1% of asymptomatic carriers (38/48)remained asymptomatic. Disease worsened in 79·4% (112/141) of probands versus 38·1% (40/105) of relatives and advanced more rapidly in probands compared to affected relatives (ΔFSHD score 2·3 versus 1·2). We found no differences in disease progression between the two sexes (p=0·151). Among different muscles investigated by MRC grading scale, tibialis anterior was affected the most (41·0% (101/246) of subjects) at baseline; in five years its strength diminished in 49·6% (70/141) of probands. Interpretation: CCEF categories have strong prognostic effect in carriers of DRA. Assessment of clinical phenotypes and family kinship are pivotal for the clinical management of DRA carrier and should guide eligibility criteria for clinical trials. Funding Statement: Telethon Italy GUP13012, AFM Telethon 16593, Regione Emilia Romagna RARER. Declaration of Interests: The authors report no competing interests. Ethics Approval Statement: The INRF database was approved by the local ethics committee of the contributing centers. Informed written consent was obtained from all study participants, in accordance with the ethical standards of the 1964 Declaration of Helsinki.

NEW THERAPEUTIC APPROACHES: I.8Emerging therapeutic approaches for Facioscapulohumeral muscular dystrophy (FSHD)

NEW THERAPEUTIC APPROACHES: I.8Emerging therapeutic approaches for Facioscapulohumeral muscular dystrophy (FSHD)

Identification of SMCHD1 domains for nuclear localization, homo-dimerization, and protein cleavage

BackgroundSMCHD1 is a disease modifier and a causative gene for facioscapulohumeral muscular dystrophy (FSHD) type 1 and type 2, respectively. A large variety of different mutations in SMCHD1 have been identified as causing FSHD2. In many cases, it is unclear how these mutations disrupt the normal function of SMCHD1.MethodsWe made and analyzed lenti-viral vectors that express Flag-tagged full-length or different mutant SMCHD1 proteins to better understand the functional domains of SMCHD1 in muscle cells.ResultsWe identified regions necessary for nuclear localization, dimerization, and cleavage sites. Moreover, we confirmed that some mutants increased DUX4 expression in FSHD1 myoblasts.ConclusionsThese findings provide an additional basis for understanding the molecular consequences of SMCHD1 mutations.

Electrical impedance myography in facioscapulohumeral muscular dystrophy: A 1‐year follow‐up study

Electrical impedance myography (EIM) is a noninvasive technique for measuring muscle composition and a potential physiological biomarker for facioscapulohumeral muscular dystrophy (FSHD). Thirty-two participants with genetically confirmed and clinically affected FSHD underwent EIM in 7 muscles bilaterally. Correlations between EIM and baseline clinical measures were used to select EIM variables of interest in FSHD, and EIM and clinical measures were followed for 1 year. There were no significant changes in the EIM variables. Although 50-kHZ reactance correlated the strongest with clinical measures at baseline, the 50-211-kHZ phase ratio demonstrated lower within-subject 12-month variability, potentially offering sample size savings for FSHD clinical trial planning. EIM did not identify significant disease progression over 12 months. It is currently unclear whether this is because of limitations of the technology or the slow rate of disease progression in this cohort of FSHD patients over this period of time. Muscle Nerve 58: 213-218, 2018.

A cre-inducible DUX4 transgenic mouse model for investigating facioscapulohumeral muscular dystrophy.

The Double homeobox 4 (DUX4) gene is an important regulator of early human development and its aberrant expression is causal for facioscapulohumeral muscular dystrophy (FSHD). The DUX4-full length (DUX4-fl) mRNA splice isoform encodes a transcriptional activator; however, DUX4 and its unique DNA binding preferences are specific to old-world primates. Regardless, the somatic cytotoxicity caused by DUX4 expression is conserved when expressed in cells and animals ranging from fly to mouse. Thus, viable animal models based on DUX4-fl expression have been difficult to generate due in large part to overt developmental toxicity of low DUX4-fl expression from leaky transgenes. We have overcome this obstacle and here we report the generation and initial characterization of a line of conditional floxed DUX4-fl transgenic mice, FLExDUX4, that is viable and fertile. In the absence of cre, these mice express a very low level of DUX4-fl mRNA from the transgene, resulting in mild phenotypes. However, when crossed with appropriate cre-driver lines of mice, the double transgenic offspring readily express DUX4-fl mRNA, protein, and target genes with the spatiotemporal pattern of nuclear cre expression dictated by the chosen system. When cre is expressed from the ACTA1 skeletal muscle-specific promoter, the double transgenic animals exhibit a developmental myopathy. When crossed with tamoxifen-inducible cre lines, DUX4-mediated pathology can be induced in adult animals. Thus, the appearance and progression of pathology can be controlled to provide readily screenable phenotypes useful for assessing therapeutic approaches targeting DUX4-fl mRNA and protein. Overall, the FLExDUX4 line of mice is quite versatile and will allow new investigations into mechanisms of DUX4-mediated pathophysiology as well as much-needed pre-clinical testing of DUX4-targeted FSHD interventions in vivo.

Adding quantitative muscle MRI to the FSHD clinical trial toolbox.

To add quantitative muscle MRI to the clinical trial toolbox for facioscapulohumeral muscular dystrophy (FSHD) by correlating it to clinical outcome measures in a large cohort of genetically and clinically well-characterized patients with FSHD comprising the entire clinical spectrum. Quantitative MRI scans of leg muscles of 140 patients with FSHD1 and FSHD2 were assessed for fatty infiltration and TIRM hyperintensities and were correlated to multiple clinical outcome measures. The mean fat fraction of the total leg musculature correlated highly with the motor function measure, FSHD clinical score, Ricci score, and 6-minute walking test (correlation coefficients -0.845, 0.835, 0.791, -0.701, respectively). Fat fraction per muscle group correlated well with corresponding muscle strength (correlation coefficients up to -0.82). The hamstring muscles, adductor muscles, rectus femoris, and gastrocnemius medialis were affected most frequently, also in early stage disease and in patients without leg muscle weakness. Muscle involvement was asymmetric in 20% of all muscle pairs and fatty infiltration within muscles showed a decrease from distal to proximal of 3.9%. TIRM hyperintense areas, suggesting inflammation, were found in 3.5% of all muscles, with and without fatty infiltration. We show a strong correlation between quantitative muscle MRI and clinical outcome measures. Muscle MRI is able to detect muscle pathology before clinical involvement of the leg muscles. This indicates that quantitative leg muscle MRI is a promising biomarker that captures disease severity and motor functioning and can thus be included in the FSHD trial toolbox.

A cross sectional study of two independent cohorts identifies serum biomarkers for facioscapulohumeral muscular dystrophy (FSHD)

Measuring the severity and progression of facioscapulohumeral muscular dystrophy (FSHD) is particularly challenging because muscle weakness progresses over long periods of time and can be sporadic. Biomarkers are essential for measuring disease burden and testing treatment strategies. We utilized the sensitive, specific, high-throughput SomaLogic proteomics platform of 1129 proteins to identify proteins with levels that correlate with FSHD severity in a cross-sectional study of two independent cohorts. We discovered biomarkers that correlate with clinical severity and disease burden measured by magnetic resonance imaging. Sixty-eight proteins in the Rochester cohort (n = 48) and 51 proteins in the Seattle cohort (n = 30) had significantly different levels in FSHD-affected individuals when compared with controls (p-value ≤ .005). A subset of these varied by at least 1.5 fold and four biomarkers were significantly elevated in both cohorts. Levels of creatine kinase MM and MB isoforms, carbonic anhydrase III, and troponin I type 2 reliably predicted the disease state and correlated with disease severity. Other novel biomarkers were also discovered that may reveal mechanisms of disease pathology. Assessing the levels of these biomarkers during clinical trials may add significance to other measures of quantifying disease progression or regression.

G.O.14 - Antisense strategies targeting DUX4 and DUX4c as therapeutic approaches for facioscapulohumeral muscular dystrophy (FSHD)

G.O.14 - Antisense strategies targeting DUX4 and DUX4c as therapeutic approaches for facioscapulohumeral muscular dystrophy (FSHD)

Loss of epigenetic silencing of the DUX4 transcription factor gene in facioscapulohumeral muscular dystrophy.

Current genetic and molecular evidence best supports an epigenetic mechanism for facioscapulohumeral muscular dystrophy (FSHD), whereby de-repression of the D4Z4 macrosatellite array leads to aberrant expression of the DUX4 transcription factor in skeletal muscle. This de-repression is triggered by either array contraction or (more rarely) by mutation of the SMCHD1 (structural maintenance of chromosomes flexible hinge domain containing 1) gene. Activation of DUX4 targets, including germline genes and several mammalian retrotransposons, then drives pathogenesis. A direct role for DUX4 mRNA in suppression of nonsense-mediated decay pathways has recently been demonstrated and may also contribute to muscle pathology. Loss of D4Z4 repression in FSHD is observed as hypomethylation of the array accompanied by loss of repressive chromatin marks. The molecular mechanisms of D4Z4 repression are poorly understood, but recent data have identified an Argonaute (AGO)-dependent siRNA pathway. Targeting this pathway by exogenous siRNAs could be a therapeutic strategy for FSHD.

610. Translating DUX4-Targeted RNAi Therapy for FSHD

OBJECTIVE: Develop a DUX4-targeted RNAi-based gene therapy for Facioscapulohumeral muscular dystrophy (FSHD)BACKGROUND: FSHD, the third most prevalent muscular dystrophy, is an autosomal dominant disorder that most commonly causes progressive weakness in muscles of the face, shoulder girdle, and limbs. FSHD was formally classified as a major form of muscular dystrophy in 1954, but the pathogenic events leading to the disease have only recently started coming into focus. Several studies now support an FSHD model involving aberrant expression of the DUX4 gene, which encodes a myotoxic transcription factor. The emergence of DUX4 represented a momentum shift in the FSHD field as it provided an important target for therapy design. As FSHD is currently untreatable, developing effective therapies is a critical need in the field. We hypothesized that an FSHD treatment should center on inhibiting DUX4 expression and/or activity, and have implemented several strategies to accomplish this goal. In the first published study on DUX4 inhibition, we demonstrated that AAV-mediated RNAi gene therapy could effectively suppress DUX4 expression and protect mouse muscles from its toxic effects. Specifically, our therapeutic DUX4-targeted artificial microRNAs improved histological, molecular, and functional outcomes associated with DUX4 expression in muscle. We are now working to translate this therapy through optimization of vector and delivery route. In addition, as over-expression of inhibitory RNAs have been associated with off-target effects, we are assessing the safety of this approach using dose-escalation and toxicology studies. The latter experiment is particularly important since the potential toxicity of RNAi therapy has not been previously assessed in muscles.DESIGN/METHODS: We addressed 4 issues in this study, as we proceed down a path toward translation: (1) removed the GFP reporter from our 1st-generation AAV vectors; (2) tested additional DUX4-targeted miRNA sequences; (3) developed muscle-restrictive promoters for miRNA expression; and (4) determined the safety of muscle-targeted miRNA therapy through dose-escalation toxicology studies, using direct intramuscular injection and vascular delivery.RESULTS: Removal of the GFP reporter gene had no deleterious effect on therapeutic efficacy and positioned our new vectors for potential clinical usage. Our alternative DUX4 miRNA proved to be equally effective at preventing DUX4-induced toxicity as the original sequence, and we have established safety thresholds by determining the maximum tolerable AAV. miRNA dose in mice for IM and IV delivery. At very high levels, all AAV-delivered miRNAs showed some toxicity, but importantly we found no deleterious overt pathology related to miRNA treatment at vector doses proven effective for DUX4 suppression in mice, over several timepoints. This toxicology data is promising for translating this strategy, especially considering DUX4 is markedly less abundant in human FSHD muscle than in our mouse model (which expresses the gene at very high levels).CONCLUSIONS: This study provides important data necessary for translating an RNAi-based therapy for FSHD.

144. Consequences of Temporal, Pulsing DUX4 Expression Pattern Revealed in a Novel Therapeutic Screening Platform for Facioscapulohumeral Muscular Dystrophy (FSHD)

144. Consequences of Temporal, Pulsing DUX4 Expression Pattern Revealed in a Novel Therapeutic Screening Platform for Facioscapulohumeral Muscular Dystrophy (FSHD)

Multiplex Screen of Serum Biomarkers in Facioscapulohumeral Muscular Dystrophy.

Recent studies have proposed a unified genetic model for Facioscapulohumeral muscular dystrophy (FSHD), identifying potential therapeutic targets for future clinical trials. Serum biomarkers related to disease activity will be important for proof of concept or early phase clinical studies. To identify potential serum biomarkers in FSHD for possible use in future clinical trials. We performed a prospective cross-sectional study of serum biomarkers in 22 FSHD patients (19 FSHD1, 3 FSHD2) compared to 23 age and gender-matched healthy controls using a commercial multiplex, microsphere-based immune-fluorescent assay of 243 markers (Myriad, Human Discovery MAP 250, v2.0). 169 markers had values sufficient for analysis. Correction for multiple testing identified 7 biomarkers below a 5% false discovery rate: creatine kinase MB fraction (CKMB, 6.52 fold change, P<0.0001), tissue-type plasminogen activator (PLAT, 1.64 fold change, P<0.0001), myoglobin (2.23 fold change, P=0.0001), epidermal growth factor (EGF, 2.33 fold change, P=0.0004), chemokine (C-C motif) ligand 2 (1.48 fold change, P=0.0004), CD 40 ligand (1.89 fold change, P=0.001), and vitronectin (VTN, 1.28 fold change, P=0.001). Moderate correlations to measures of FSHD disease were seen for CKMB, PLAT, and EGF. Markers in the plasminogen pathway (PLAT, serpin peptidase inhibitor, and VTN) were correlated with each other in FSHD but not healthy controls. Commercial multiplex immune-fluorescent screening is a potentially powerful tool for identifying biomarkers for future FSHD therapeutic trials. Biomarkers identified in this study warrant further study in a larger prospective validation study.