The Classification, Natural History and Treatment of the Limb Girdle Muscular Dystrophies

Anesthetic Challenges of a Patient With Limb-Girdle Muscular Dystrophy in a Patient With Colon Cancer

Limb-girdle muscular dystrophy (LGMD) presents a unique challenge for anesthesiologists because of the potential complications related to surgery and anesthesia. This is a case of a 55-year-old male with colon cancer and a history of LGMD, who underwent a low anterior resection colectomy under general anesthesia. Because of the pathogenic variants in the RYR1 gene implicated in various congenital myopathies, we review clinical concerns associated with LGMD and describe the anesthetic management of our patient with LGMD and a potentially difficult airway.

Validation of a novel western blot assay to monitor patterns and levels of alpha dystroglycan in skeletal muscle of patients with limb girdle muscular dystrophies

The cell membrane protein, dystroglycan, plays a crucial role in connecting the cytoskeleton of a variety of mammalian cells to the extracellular matrix. The α-subunit of dystroglycan (αDG) is characterized by a high level of glycosylation, including a unique O-mannosyl matriglycan. This specific glycosylation is essential for binding of αDG to extracellular matrix ligands effectively. A subset of muscular dystrophies, called dystroglycanopathies, are associated with aberrant, dysfunctional glycosylation of αDG. This defect prevents myocytes from attaching to the basal membrane, leading to contraction-induced injury. Here, we describe a novel Western blot (WB) assay for determining levels of αDG glycosylation in skeletal muscle tissue. The assay described involves extracting proteins from fine needle tibialis anterior (TA) biopsies and separation using SDS-PAGE followed by WB. Glycosylated and core αDG are then detected in a multiplexed format using fluorescent antibodies. A practical application of this assay is demonstrated with samples from normal donors and patients diagnosed with LGMD2I/R9. Quantitative analysis of the WB, which employed the use of a normal TA derived calibration curve, revealed significantly reduced levels of αDG in patient biopsies relative to unaffected TA. Importantly, the assay was able to distinguish between the L276I homozygous patients and a more severe form of clinical disease observed with other FKRP variants. Data demonstrating the accuracy and reliability of the assay are also presented, which further supports the potential utility of this novel assay to monitor changes in ⍺DG of TA muscle biopsies in the evaluation of potential therapeutics.

Constructing networks for comparison of collagen types

Collagens are structural proteins that are predominantly found in the extracellular matrix of multicellular animals, where they are mainly responsible for the stability and structural integrity of various tissues. All collagens contain polypeptide strands (α-chains). There are several types of collagens, some of which differ significantly in form, function, and tissue specificity. Because of their importance in clinical research, they are grouped into subdivisions, the so-called collagen families, and their sequences are often analysed. However, problems arise with highly homologous sequence segments. To increase the accuracy of collagen classification and prediction of their functions, the structure of these collagens and their expression in different tissues could result in a better focus on sequence segments of interest. Here, we analyse collagen families with different levels of conservation. As a result, clusters with high interconnectivity can be found, such as the fibrillar collagens, the COL4 network-forming collagens, and the COL9 FACITs. Furthermore, a large cluster between network-forming, FACIT, and COL28a1 α-chains is formed with COL6a3 as a major hub node. The formation of clusters also signifies, why it is important to always analyse the α-chains and why structural changes can have a wide range of effects on the body.

Pharmacological Treatments and Therapeutic Targets in Muscle Dystrophies Generated by Alterations in Dystrophin-Associated Proteins

Muscular dystrophies (MDs) are a heterogeneous group of diseases of genetic origin characterized by progressive skeletal muscle degeneration and weakness. There are several types of MDs, varying in terms of age of onset, severity, and pattern of the affected muscles. However, all of them worsen over time, and many patients will eventually lose their ability to walk. In addition to skeletal muscle effects, patients with MDs may present cardiac and respiratory disorders, generating complications that could lead to death. Interdisciplinary management is required to improve the surveillance and quality of life of patients with an MD. At present, pharmacological therapy is only available for Duchene muscular dystrophy (DMD)-the most common type of MD-and is mainly based on the use of corticosteroids. Other MDs caused by alterations in dystrophin-associated proteins (DAPs) are less frequent but represent an important group within these diseases. Pharmacological alternatives with clinical potential in patients with MDs and other proteins associated with dystrophin have been scarcely explored. This review focuses on drugs and molecules that have shown beneficial effects, mainly in experimental models involving alterations in DAPs. The mechanisms associated with the effects leading to promising results regarding the recovery or maintenance of muscle strength and reduction in fibrosis in the less-common MDs (i.e., with respect to DMD) are explored, and other therapeutic targets that could contribute to maintaining the homeostasis of muscle fibers, involving different pathways, such as calcium regulation, hypertrophy, and maintenance of satellite cell function, are also examined. It is possible that some of the drugs explored here could be used to affordably improve the muscular function of patients until a definitive treatment for MDs is developed.

Identification of novel pathogenic variants of Calpain-3 gene in limb girdle muscular dystrophy R1

BACKGROUND

Limb Girdle Muscular Dystrophy R1 (LGMDR1) is an autosomal recessive neuromuscular disease caused by mutations in the calpain-3 (CAPN3) gene. As clinical and pathological features may overlap with other types of LGMD, therefore definite molecular diagnosis is required to understand the progression of this debilitating disease. This study aims to identify novel variants of CAPN3 gene in LGMDR1 patients.

RESULTS

Thirty-four patients with clinical and histopathological features suggestive of LGMD were studied. The muscle biopsy samples were evaluated using Enzyme histochemistry, Immunohistochemistry, followed by Western Blotting and Sanger sequencing. Out of 34 LGMD cases, 13 patients were diagnosed as LGMDR1 by immunoblot analysis, demonstrating reduced or absent calpain-3 protein as compared to controls. Variants of CAPN3 gene were also found and pathogenicity was predicted using in-silico prediction tools. The CAPN3 gene variants found in this study, included, two missense variants [CAPN3: c.1189T > C, CAPN3: c.2338G > C], one insertion-deletion [c.1688delinsTC], one splice site variant [c.2051-1G > T], and one nonsense variant [c.1939G > T; p.Glu647Ter].

CONCLUSIONS

We confirmed 6 patients as LGMDR1 (with CAPN3 variants) from our cohort and calpain-3 protein expression was significantly reduced by immunoblot analysis as compared to control. Besides the previously known variants, our study found two novel variants in CAPN3 gene by Sanger sequencing-based approach indicating that genetic variants in LGMDR1 patients may help to understand the etiology of the disease and future prognostication.

Gene therapy with bidridistrogene xeboparvovec for limb-girdle muscular dystrophy type 2E/R4: phase 1/2 trial results

Limb-girdle muscular dystrophy 2E/R4 is caused by mutations in the β-sarcoglycan (SGCB) gene, leading to SGCB deficiency and consequent muscle loss. We developed a gene therapy approach based on functional replacement of the deficient SCB protein. Here we report interim results from a first-in-human, open-label, nonrandomized, phase 1/2 trial evaluating the safety and efficacy of bidridistrogene xeboparvovec, an adeno-associated virus-based gene therapy containing a codon-optimized, full-length human SGCB transgene. Patients aged 4-15 years with confirmed SGCB mutations at both alleles received one intravenous infusion of either 1.85 × 1013 vector genome copies kg-1 (Cohort 1, n = 3) or 7.41 × 1013 vector gene copies kg-1 (Cohort 2, n = 3). Primary endpoint was safety, and secondary endpoint was change in SGCB expression in skeletal muscle from baseline to Day 60. We report interim Year 2 results (trial ongoing). The most frequent treatment-related adverse events were vomiting (four of six patients) and gamma-glutamyl transferase increase (three of six patients). Serious adverse events resolved with standard therapies. Robust SGCB expression was observed: Day 60 mean (s.d.) percentage of normal expression 36.2% (2.7%) in Cohort 1 and 62.1% (8.7%) in Cohort 2. Post hoc exploratory analysis showed preliminary motor improvements using the North Star Assessment for Limb-girdle Type Muscular Dystrophies maintained through Year 2. The 2-year safety and efficacy of bidridistrogene xeboparvovec support clinical development advancement. Further studies are necessary to confirm the long-term safety and efficacy of this gene therapy. ClinicalTrials.gov registration: NCT03652259 .

Combined sequence and copy number analysis improves diagnosis of limb girdle and other myopathies

OBJECTIVE

Clinical and genetic heterogeneities make diagnosis of limb-girdle muscular dystrophy (LGMD) and other overlapping disorders of muscle weakness complicated and expensive. We aimed to develop a comprehensive next generation sequence-based multi-gene panel ("The Lantern Focused Neuromuscular Panel") to detect both sequence variants and copy number variants in one assay.

METHODS

Patients with clinical diagnosis of LGMD or other overlapping muscular dystrophies in the United States were tested by PerkinElmer Genomics in 2018-2021 via "The Lantern Project," a sponsored diagnostic testing program. Sixty-six genes related to LGMD subtypes- and other myopathies were investigated. Main outcomes were diagnostic yield, gene-variant spectrum, and LGMD subtypes' prevalence.

RESULTS

Molecular diagnosis was established in 19.6% (1266) of 6473 cases. Major genes contributing to LGMD were identified including CAPN3 (5.4%, 68), DYSF (4.0%, 51), GAA (3.7%, 47), ANO5 (3.6%, 45), and FKRP (2.7%, 34). Genes of other overlapping MD subtypes identified included PABPN1 (10.5%, 133), VCP (2.2%, 28), MYOT (1.2% 15), LDB3 (1.0%, 13), COL6A1 (1.5%, 19), FLNC (1.1%, 14), and DNAJB6 (0.8%, 10). Different sizes of copy number variants including single exon, multi-exon, and whole genes were identified in 7.5% (95) cases in genes including DMD, EMD, CAPN3, ANO5, SGCG, COL6A2, DOK7, and LAMA2.

INTERPRETATION

"The Lantern Focused Neuromuscular Panel" enables identification of LGMD subtypes and other myopathies with overlapping clinical features. Prevalence of some MD subtypes was higher than previously reported. Widespread deployment of this comprehensive NGS panel has the potential to ensure early, accurate diagnosis as well as re-define MD epidemiology.

Single-centre experience with autosomal recessive limb-girdle muscular dystrophy: case series and literature review

Limb-girdle muscular dystrophy (LGMD) is a group of myopathies that lead to progressive muscle weakness, predominantly involving the shoulder and pelvic girdles; it has a heterogeneous genetic etiology, with variation in the prevalence of subtypes according to the ethnic backgrounds and geographic origins of the populations. The aim of the present study was to analyze a series of patients with autosomal recessive LGMD (LGMD-R) to contribute to a better characterization of the disease and to find the relative proportion of the different subtypes in a Southern Brazil cohort. The sample population consisted of 36 patients with LGMD-R. A 9-gene targeted next-generation sequencing panel revealed variants in 23 patients with LGMD (64%), and it identified calpainopathy (LGMD-R1) in 26%, dysferlinopathy (LGMD-R2) in 26%, sarcoglycanopathies (LGMD-R3-R5) in 13%, telethoninopathy (LGMD-R7) in 18%, dystroglicanopathy (LGMD-R9) in 13%, and anoctaminopathy (LGMD-R12) in 4% of the patients. In these 23 patients with LGMD, there were 27 different disease-related variants in the ANO5, CAPN3, DYSF, FKRP, SGCA, SGCB, SGCG, and TCAP genes. There were different causal variants in different exons of these genes, except for the TCAP gene, for which all patients carried the p.Gln53* variant, and the FKRP gene, which showed recurrence of the p.Leu276Ile variant. We analyzed the phenotypic, genotypic and muscle immunohistochemical features of this Southern Brazilian cohort.

Disease modeling and gene correction of LGMDR21 iPSCs elucidates the role of POGLUT1 in skeletal muscle maintenance, regeneration, and the satellite cell niche

Autosomal recessive limb-girdle muscular dystrophy 21 (LGMDR21) is caused by pathogenic variants in protein O-glucosyltransferase 1 (POGLUT1), which is responsible for O-glucosylation of specific epidermal growth factor (EGF) repeats found in ∼50 mammalian proteins, including Notch receptors. Previous data from patient biopsies indicated that impaired Notch signaling, reduction of muscle stem cells, and accelerated differentiation are probably involved in disease etiopathology. Using patient induced pluripotent stem cells (iPSCs), their corrected isotypes, and control iPSCs, gene expression profiling indicated dysregulation of POGLUT1, NOTCH, muscle development, extracellular matrix (ECM), cell adhesion, and migration as involved pathways. They also exhibited reduced in vitro POGLUT1 enzymatic activity and NOTCH signaling as well as defective myogenesis, proliferation, migration and differentiation. Furthermore, in vivo studies demonstrated significant reductions in engraftment, muscle stem cell formation, PAX7 expression, and maintenance, along with an increased percentage of mislocalized PAX7+ cells in the interstitial space. Gene correction in patient iPSCs using CRISPR-Cas9 nickase led to the rescue of the main in vitro and in vivo phenotypes. These results demonstrate the efficacy of iPSCs and gene correction in disease modeling and rescue of the phenotypes and provide evidence of the involvement of muscle stem cell niche localization, PAX7 expression, and cell migration as possible mechanisms in LGMDR21.

Tripartite Motif-Containing Protein 32 (TRIM32): What Does It Do for Skeletal Muscle?

Tripartite motif-containing protein 32 (TRIM32) is a member of the tripartite motif family and is highly conserved from flies to humans. Via its E3 ubiquitin ligase activity, TRIM32 mediates and regulates many physiological and pathophysiological processes, such as growth, differentiation, muscle regeneration, immunity, and carcinogenesis. TRIM32 plays multifunctional roles in the maintenance of skeletal muscle. Genetic variations in the TRIM32 gene are associated with skeletal muscular dystrophies in humans, including limb-girdle muscular dystrophy type 2H (LGMD2H). LGMD2H-causing genetic variations of TRIM32 occur most frequently in the C-terminal NHL (ncl-1, HT2A, and lin-41) repeats of TRIM32. LGMD2H is characterized by skeletal muscle dystrophy, myopathy, and atrophy. Surprisingly, most patients with LGMD2H show minimal or no dysfunction in other tissues or organs, despite the broad expression of TRIM32 in various tissues. This suggests more prominent roles for TRIM32 in skeletal muscle than in other tissues or organs. This review is focused on understanding the physiological roles of TRIM32 in skeletal muscle, the pathophysiological mechanisms mediated by TRIM32 genetic variants in LGMD2H patients, and the correlations between TRIM32 and Duchenne muscular dystrophy (DMD).

Concept Elicitation Interviews and Conceptual Model to Understand the Patient Experience of Limb Girdle Muscular Dystrophy

INTRODUCTION

Limb girdle muscular dystrophies (LGMDs) are a group of rare and heterogeneous disorders involving progressive wasting of shoulder and pelvic girdle musculature. This study aimed to generate qualitative evidence on patient and caregiver experiences with symptoms and impacts of LGMD on overall function and daily life for sarcoglycanopathy subtypes 2C/R5, 2D/R3, and 2E/R4.

METHODS

Twenty-three individuals with LGMD with (n = 5) or without (n = 18) a caregiver participated in 60-minute semi-structured video interviews. Interview transcripts were analyzed using thematic analysis. Differences in patient experience by ambulation status and LGMD subtype were examined.

RESULTS

Participants were ambulatory (n = 14) and non-ambulatory (n = 9), representing three subtypes: 2C/R5 (n = 4), 2D/R3 (n = 12), and 2E/R4 (n = 7), with mean age of 34.8 years (SD = 16.08). 56.5% identified as female. Conceptual saturation was achieved within 18/23 interviews. Ambulatory participants identified difficulty with complex physical activities, e.g., running (n = 11, 78.6%), physical strength (n = 14, 100%), and difficulty with transfers, e.g., difficulty getting off the floor (n = 10, 71.4%). All non-ambulatory participants discussed problems with activities of daily living (ADLs) and transfers, e.g., getting in/out of bed and upper extremity function, particularly reaching (n = 8, 88.9%) and fine motor skills (n = 6, 66.7%). Fatigue and pain were reported by the majority of participants (n = 16, 69.6% and n = 19, 82.6%, respectively). A conceptual disease model was developed illustrating symptoms and impacts and their relationships to disease stage, capturing the patient experience across LGMD disease trajectory.

CONCLUSIONS

This study contributes to the limited evidence describing the patient experience of living with LGMD. The conceptual model can inform patient-centered assessment in future LGMD clinical trials.

Utilization of Targeted RNA-Seq for the Resolution of Variant Pathogenicity and Enhancement of Diagnostic Yield in Dysferlinopathy

For inherited diseases, obtaining a definitive diagnosis is critical for proper disease management, family planning, and participation in clinical trials. This can be challenging for dysferlinopathy due to the significant clinical overlap between the 30+ subtypes of limb–girdle muscular dystrophy (LGMD) and the large number of variants of unknown significance (VUSs) that are identified in the dysferlin gene, DYSF. We performed targeted RNA-Seq using a custom gene-panel in 77 individuals with a clinical/genetic suspicion of dysferlinopathy and evaluated all 111 identified DYSF variants according to the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) guidelines. This evaluation identified 11 novel DYSF variants and allowed for the classification of 87 DYSF variants as pathogenic/likely pathogenic, 8 likely benign, while 16 variants remained VUSs. By the end of the study, 60 of the 77 cases had a definitive diagnosis of dysferlinopathy, which was a 47% increase in diagnostic yield over the rate at study onset. This data shows the ability of RNA-Seq to assist in variant pathogenicity classification and diagnosis of dysferlinopathy and is, therefore, a type of analysis that should be considered when DNA-based genetic analysis is not sufficient to provide a definitive diagnosis.

Systemic γ-sarcoglycan AAV gene transfer results in dose-dependent correction of muscle deficits in the LGMD 2C/R5 mouse model

Limb-girdle muscular dystrophy (LGMD) type 2C/R5 results from mutations in the γ-sarcoglycan (SGCG) gene and is characterized by muscle weakness and progressive wasting. Loss of functional γ-sarcoglycan protein in the dystrophin-associated protein complex destabilizes the sarcolemma, leading to eventual myofiber death. The SGCG knockout mouse (SGCG ^-/-) has clinical-pathological features that replicate the human disease, making it an ideal model for translational studies. We designed a self-complementary rAAVrh74 vector containing a codon-optimized human SGCG transgene driven by the muscle-specific MHCK7 promoter (SRP-9005) to investigate adeno-associated virus (AAV)-mediated SGCG gene transfer in SGCG ^-/- mice as proof of principle for LGMD 2C/R5. Gene transfer therapy resulted in widespread transgene expression in skeletal muscle and heart, improvements in muscle histopathology characterized by decreased central nuclei and fibrosis, and normalized fiber size. Histopathologic improvements were accompanied by functional improvements, including increased ambulation and force production and resistance to injury of the tibialis anterior and diaphragm muscles. This study demonstrates successful systemic delivery of the hSGCG transgene in SGCG ^-/- mice, with functional protein expression, reconstitution of the sarcoglycan complex, and corresponding physiological and functional improvements, which will help establish a minimal effective dose for translation of SRP-9005 gene transfer therapy in patients with LGMD 2C/R5.

Identification of circulating miRNAs differentially expressed in patients with Limb-girdle, Duchenne or facioscapulohumeral muscular dystrophies

BACKGROUND

Limb-girdle muscular dystrophy (LGMD) is a rare neuromuscular disease including a growing and heterogeneous number of subtypes with variable phenotype. Their clinical and histopathological characteristics frequently overlap with other neuromuscular dystrophies. Our goal was to identify, by a non-invasive method, a molecular signature including biochemical and epigenetic parameters with potential value for patient prognosis and stratification.

RESULTS

Circulating miRNome was obtained by smallRNA-seq in plasma from LGMD patients (n = 6) and matched-controls (n = 6). Data, validated by qPCR in LGMD samples, were also examined in other common muscular dystrophies: Duchenne (DMD) (n = 5) and facioscapulohumeral muscular dystrophy (FSHD) (n = 4). Additionally, biochemical and clinical parameters were analyzed. miRNome analysis showed that thirteen differentially expressed miRs could separate LGMD vs control group by hierarchical clustering. Most of differentially expressed miRs in LGMD patients were up-regulated (miR-122-5p, miR-122b-3p, miR-6511a-3p, miR-192-5p, miR-574-3p, mir-885-3p, miR-29a-3p, miR-4646-3p, miR-203a-3p and miR-203b-5p) whilst only three of sequenced miRs were significantly down-regulated (miR-19b-3p, miR-7706, miR-323b-3p) when compared to matched controls. Bioinformatic analysis of target genes revealed cell cycle, muscle tissue development, regeneration and senescence as the most affected pathways. Four of these circulating miRs (miR-122-5p, miR-192-5p, miR-19b-3p and miR-323b-3p), together with the myomiR miR-206, were further analysed by qPCR in LGMD, DMD and FSHD. The receiver operating characteristic curves (ROC) revealed high area under the curve (AUC) values for selected miRs in all groups, indicating that these miRs have good sensitivity and specificity to distinguish LGMD, DMD and FSHD patients from healthy controls. miR-122-5p, miR-192-5p and miR-323-3p were differentially expressed compared to matched-controls in all groups but apparently, each type of muscular dystrophy showed a specific pattern of miR expression. Finally, a strong correlation between miRs and biochemical data was only found in LGMD patients: while miR-192-5p and miR-122-5p negatively correlated with CK, miR-192-5p positively correlated with vitamin D3 and ALP.

CONCLUSIONS

Although limited by the small number of patients included in this study, we propose here a specific combination of circulating miR-122-5p/miR-192-5p/miR-323-3 and biochemical parameters as a potential molecular signature whose clinical value for LGMD patient prognosis and stratification should be further confirmed in a larger cohort of patients.

The Limb-Girdle Muscular Dystrophies

PURPOSE OF REVIEW

The limb-girdle muscular dystrophies (LGMDs) are a group of inherited muscle disorders with a common feature of limb-girdle pattern of weakness, caused by over 29 individual genes. This article describes the classification scheme, common subtypes, and the management of individuals with LGMD.

RECENT FINDINGS

Advances in genetic testing and next-generation sequencing panels containing all of the LGMD genes have led to earlier genetic confirmation, but also to more individuals with variants of uncertain significance. The LGMDs include disorders with autosomal recessive inheritance, which are often due to loss-of-function mutations in muscle structural or repair proteins and typically have younger ages of onset and more rapidly progressive presentations, and those with autosomal dominant inheritance, which can have older ages of presentation and chronic progressive disease courses. All cause progressive disability and potential loss of ability to walk or maintain a job due to progressive muscle wasting. Certain mutations are associated with cardiac or respiratory involvement. No disease-altering therapies have been approved by the US Food and Drug Administration (FDA) for LGMDs and standard treatment uses a multidisciplinary clinic model, but recessive LGMDs are potentially amenable to systemic gene replacement therapies, which are already being tested in clinical trials for sarcoglycan and FKRP mutations. The dominant LGMDs may be amenable to RNA-based therapeutic approaches.

SUMMARY

International efforts are underway to better characterize LGMDs, help resolve variants of uncertain significance, provide consistent and improved standards of care, and prepare for future clinical trials.

Causative variants linked with limb girdle muscular dystrophy in an Iranian population: 6 novel variants

BACKGROUND

Limb-girdle muscular dystrophy (LGMD) is a non-syndromic muscular dystrophy caused by variations in the genes involved in muscle structure, function and repair. The heterogeneity in the severity, progression, age of onset, and causative genes makes next-generation sequencing (NGS) a necessary approach for the proper diagnosis of LGMD.

METHODS

In this article, 26 Iranian patients with LGMD criteria were diagnosed with disease variants in the genes encoding calpain3, dysferlin, sarcoglycans and Laminin α-2. Patients were referred to the hospital with variable distribution of muscle wasting and progressive weakness in the body. The symptoms along with biochemical and EMG tests were suggestive of LGMD; thus the genomic DNA of patients were investigated by whole-exome sequencing including flanking intronic regions. The target genes were explored for the disease-causing variants. Moreover, the consequence of the amino acid alterations on proteins' secondary structure and function was investigated for a better understanding of the pathogenicity of variants. Variants were sorted based on the genomic region, type and clinical significance.

RESULTS

In a comprehensive investigation of previous clinical records, 6 variations were determined as novel, including c.1354-2 A > T and c.3169_3172dupCGGC in DYSF, c.568 G > T in SGCD, c.7243 C > T, c.8662_8663 insT and c. 4397G > C in LAMA2. Some of the detected variants were located in functional domains and/or near to the post-translational modification sites, altering or removing highly conserved regions of amino acid sequence.

PACSIN proteins in vivo: Roles in development and physiology

Protein kinase C and casein kinase substrate in neurons (PACSINs), or syndapins (synaptic dynamin‐associated proteins), are a family of proteins involved in the regulation of cell cytoskeleton, intracellular trafficking and signalling. Over the last twenty years, PACSINs have been mostly studied in the in vitro and ex vivo settings, and only in the last decade reports on their function in vivo have emerged. We first summarize the identification, structure and cellular functions of PACSINs, and then focus on the relevance of PACSINs in vivo. During development in various model organisms, PACSINs participate in diverse processes, such as neural crest cell development, gastrulation, laterality development and neuromuscular junction formation. In mouse, PACSIN2 regulates angiogenesis during retinal development and in human, PACSIN2 associates with monosomy and embryonic implantation. In adulthood, PACSIN1 has been extensively studied in the brain and shown to regulate neuromorphogenesis, receptor trafficking and synaptic plasticity. Several genetic studies suggest a role for PACSIN1 in the development of schizophrenia, which is also supported by the phenotype of mice depleted of PACSIN1. PACSIN2 plays an essential role in the maintenance of intestinal homeostasis and participates in kidney repair processes after injury. PACSIN3 is abundant in muscle tissue and necessary for caveolar biogenesis to create membrane reservoirs, thus controlling muscle function, and has been linked to certain genetic muscular disorders. The above examples illustrate the importance of PACSINs in diverse physiological or tissue repair processes in various organs, and associations to diseases when their functions are disturbed.

Molecular Diagnosis of Muscular Dystrophy Patients in Western Indian Population: A Comprehensive Mutation Analysis Using Amplicon Sequencing

Muscular Dystrophies (MDs) are a group of inherited diseases and heterogeneous in nature. To date, 40 different genes have been reported for the occurrence and/or progression of MDs. This study was conducted to demonstrate the application of next-generation sequencing (NGS) in developing a time-saving and cost-effective diagnostic method to detect single nucleotide variants (SNVs) and copy number variants (CNVs) in a single test. A total of 123 cases clinically suspected of MD were enrolled in this study. Amplicon panel-based diagnosis was carried out for 102 (DMD/BMD) cases and the results were further screened using multiplex ligation-dependent probe amplification (MLPA). Whilst in the case of LGMD (N = 19) and UMD (N = 2), only NGS panel-based analysis was carried out. We identified the large deletions in 74.50% (76/102) of the cases screened with query DMD or BMD. Further, the large deletion in CAPN3 gene (N = 3) and known SNV mutations (N = 4) were identified in LGMD patients. Together, the total diagnosis rate for this amplicon panel was 70.73% (87/123) which demonstrated the utility of panel-based diagnosis for high throughput, affordable, and time-saving diagnostic strategy. Collectively, present study demonstrates that the panel based NGS sequencing could be superior over to MLPA.

Diagnostic delay in patients with FKRP-related muscular dystrophy

Diagnostic journey for people with FKRP mutations participating in a dystroglycanopathy natural history study (n = 68; NCT00313677) was analyzed. Earliest symptoms and age at muscular dystrophy diagnosis were abstracted from subject-reported medical history and record review. Initial signs/symptoms were classified as chronic motor dysfunction (e.g., delayed motor milestones, weakness, falling; n = 40, 59%), elevated transaminases (n = 7, 10%), or acute/intermittent symptoms (myoglobinuria, myalgia, febrile illness-associated acute weakness; n = 21, 31%). Median time from sign/symptom onset to diagnosis was 6.5 years and differed by symptom group: 7.5 years for motor group, 9 years for acute/intermittent group, and 4 years for elevated transaminases group. The sign/symptom category that most commonly resulted in a diagnosis was chronic motor dysfunction (n = 45). Of those without clear weakness as first symptom (n = 55), 36.4% were not diagnosed with MD until weakness became apparent. Median time to diagnosis was shortest for those with febrile illness-associated acute weakness (0.25 years). Median time from first sign/symptom to MD diagnosis has decreased incrementally from 18.8 years for those with onset in the 1970s to < 10 years for symptom onset occurring after 2000. Awareness of disease presentation variability will aid in earlier diagnosis, which is increasingly important with treatments in development.

Patient reported quality of life in limb girdle muscular dystrophy

This study determined the frequency and impact of symptoms on quality of life in patients diagnosed with limb girdle muscular dystrophy (LGMD). Participants with a diagnosis of LGMD in registries based at the Coalition to Cure Calpain-3, the Jain foundation, and the Global FKRP Registry competed a survey to report the frequency and relative impact of themes and symptoms of LGMD. Frequency, mean impact, and population impact scores were calculated, and responses were categorized by age, symptom duration, gender, employment status, use of assistive devices, and LGMD subtypes. 134 participants completed the survey. The most prevalent themes included an inability to do activities (100%), limitation with mobility (99.3%), and lower extremity weakness (97.0%). Themes with the greatest impact were: limitations with mobility, lower extremity weakness, and an inability to do activities. Symptom duration and the use of assistive devices were associated with the presence of multiple themes. Employment was associated with the impact of several themes with no differences in frequency. The prevalence and impact of these themes vary in the LMGD population. The most prevalent and impactful themes were related to weakness, but additional concerns related to emotional challenges should also be considered in clinical and research settings.

Clinical and Molecular Spectrum of Muscular Dystrophies (MDs) with Intellectual Disability (ID): a Comprehensive Overview

Muscular dystrophies encompass a wide and heterogeneous subset of hereditary myopathies that manifest by the structural or functional abnormalities in the skeletal muscle. Some pathogenic mutations induce a dysfunction or loss of proteins that are critical for the stability of muscle cells, leading to progressive muscle degradation and weakening. Several studies have well-established cognitive deficits in muscular dystrophies which are mainly due to the disruption of brain-specific expression of affected muscle proteins. We provide a comprehensive overview of the types of muscular dystrophies that are accompanied by intellectual disability by detailed consulting of the main libraries. The current paper focuses on the clinical and molecular evidence about Duchenne, congenital, limb-girdle, and facioscapulohumeral muscular dystrophies as well as myotonic dystrophies. Because these syndromes impose a heavy burden of psychological and financial problems on patients, their families, and the health care community, a thorough examination is necessary to perform timely psychological and medical interventions and thus improve the quality of life.

System for Operating Electric Wheelchairs Using Only the Remaining Functions of the Thumbs of Muscular Dystrophy Patients

For patients with muscular dystrophy, a motor dysfunction, who have difficulty operating an electric wheelchair with joysticks, a simplified one-input device is used. However, avoiding obstacles can be time-consuming. In this study, we analyzed the motor functions of the thumb of a patient with severe muscular dystrophy and identified the operations that did not cause physical fatigue. Then, we developed an operation support system to continuously operate. Finally, we conducted experiments comparing the proposed system with the conventional system and verified the effectiveness of the proposed system based on the steering accuracy of the electric wheelchair and the task completion time.

The utility of whole-exome sequencing in accurate diagnosis of neuromuscular disorders in consanguineous families in Jordan

BACKGROUND

Neuromuscular disorders (NMDs) encompass a large group of genetic and acquired diseases affecting muscles, leading to progressive muscular weakness. These disorders are frequently inherited in an autosomal-recessive (AR) pattern with extreme heterogeneity and various clinical presentations. Consanguinity increases the likelihood of AR disorders, with high rates of cousin inbreeding in Jordan and other Arab countries. In Jordan, the implementation of genetic diagnosis is limited, with delayed or misdiagnosis of genetic disorders. Thus, the lack of genetic counselling and specialized treatment options is frequently encountered in the country.

METHODS

Whole-exome sequencing (WES) was conducted for eleven probands from ten Jordanian families who have been formerly diagnosed with limb-girdle dystrophy (LGMD) and Charcot-Marie-Tooth disease (CMT). The previous diagnoses were established principally on clinical examination in the absence of genetic testing. Additionally, Sanger sequencing and segregation analysis were used to validate the resulted pathogenic variants.

RESULTS

Multiple variants were identified using WES: For DYSF gene, a missense variant (c. 4076 T > C, p.Leu1359Pro) in exon 38; a nonsense variant (c. 4321C > T, p.Gln1441Ter) in exon 39; a single-nucleotide deletion (c. 5711delG, p.Gly1904AlafsTer101) in exon 51. Other variants included a missense variant (c. 122G > A, p.Arg41Gln) in exon 3 of MPV17 gene, a single-nucleotide deletion (c. 859 delC, p.Lue287Ser fs14*) in exon 6 of SGCB gene, a missense variant (c. 311G > A, p.Gly104Asp) in exon 2 of SLC25A46 gene, a nonsense variant (c. 496C > T, p.Arg166Ter) in exon 5 of SGCG gene, and a nonsense variant (c.3202C > T, p.Gln1068Ter) in exon 13 of SH3TC2 gene.

CONCLUSION

Utilization of WES is helpful to facilitate rapid and accurate NMDs diagnosis, complementing a thorough clinical evaluation. This approach can be invaluable to aid in the identification of genetic risks among consanguineous couples. Subsequently, well-informed genetic counselling and potential individualized treatment can be provided.

The effects of 12 weeks' resistance training on psychological parameters and quality of life in adults with Facioscapulohumeral, Becker, and Limb-girdle dystrophies

PURPOSE

Investigate the impact of 12-weeks' moderate-intensity resistance training on psychological parameters in ambulatory adults with Facioscapulohumeral, Becker, and Limb-girdle muscular dystrophy.

METHODS

Seventeen adults with Facioscapulohumeral (n = 6), Limb-girdle (n = 6; types 2A, 2B, 2L, and 2I), or Becker (n = 5) muscular dystrophy took part. Participants were tested at baseline (PRE), after a 12-week control period (PRE2), and after a 12-week supervised resistance training programme (POST). Training included multi-joint and single-joint resistance exercises. Outcomes from self-report questionnaires were health-related quality of life, depressive symptoms, trait anxiety, self-esteem, and physical self-worth.

RESULTS

No difference in outcome measures, except depressive symptoms, was found in the control period (PRE to PRE2). Symptoms of depression were reduced by 9% from PRE to PRE2 (p < 0.05) and by a further 19% from PRE2 to POST (p < 0.05). Other changes from PRE2 to POST were that trait anxiety reduced by 10%, self-esteem increased by 10%, physical self-worth increased by 20%, and quality of life improved in 8 domains (p < 0.05).

CONCLUSION

These findings demonstrate the positive impact of moderate-intensity resistance training on psychological health and quality of life in adults with Facioscapulohumeral, Becker, and Limb-girdle muscular dystrophies.Implications for rehabilitationResistance training can have a positive impact on psychological health and quality of life in adults with Facioscapulohumeral, Becker, and Limb-girdle muscular dystrophy.Healthcare professionals should consider including moderate-intensity resistance training within the management and treatment programmes of adults with Facioscapulohumeral, Becker, and Limb-girdle muscular dystrophy.

Diagnostic muscle biopsies in the era of genetics: the added value of myopathology in a selection of limb-girdle muscular dystrophy patients

In the second most common dystrophy associated with predominant pelvic and shoulder girdle muscle weakness termed Limb-Girdle Muscular Dystrophy (LGMD), genetic complexity, large phenotypic variability, and clinical overlap can result in extensive diagnostic delays in certain individuals. In view of the large strides genetics has taken in this day and age, we address the question if muscle biopsies can still provide diagnostic evidence of substance for these patients. We reviewed and reanalyzed muscle biopsy characteristics in a cohort of LGMD patient pairs in which gene variants were picked up in CAPN3, FKRP, TTN, and ANO5, using histochemical-immunohistochemical-and immunofluorescent staining, and western blotting. We found that not the nature and severity of inflammatory changes, but the changed properties of the dystrophin complex were the most valuable assets to differentiate LGMD from myositis. Proteomic evaluation brought both primary and secondary deficiencies to light, which could be equally revealing for diagnosis. Though a muscle biopsy might, at present, not always be strictly necessary anymore, it still represents an irrefutable asset when the genetic diagnosis is complicated.

Clinical Determinants of Disease Progression in Patients With Beta-Sarcoglycan Gene Mutations

Background: Limb-girdle muscular dystrophy 2E (LGMD 2E), recently renamed as autosomal recessive limb-girdle muscular dystrophy-4 (LGMDR4), is characterized by the lack of beta-sarcoglycan, normally expressed in skeletal muscles and cardiomyocytes. We hypothesized that progressive respiratory and left ventricular (LV) failure in LGMDR4 could be associated with the age and interrelated phenomena of the disease's natural history.

Methods: We conducted a retrospective review of the records of 26 patients with LGMDR4. Our primary objective was to compare the rates of decline among creatine phosphokinase (CPK) values, pulmonary function test (PFT) measures, and echocardiographic estimates and to relate them to patients' age.

Results: The rates of decline/year of CPK, PFTs, and LV function estimates are significatively bound to age, with the LV ejection fraction (EF) being the strongest independent variable describing disease progression. Moreover, the rate of decline of CPK, PFTs, and LV differed in patients grouped according to their genetic mutations, demonstrating a possible genotype–phenotype correlation. The parallel trend of decline in CPK, PFT, and EF values demonstrates the presence in LGMDR4 of a simultaneous and progressive deterioration in muscular, respiratory, and cardiac function.

Conclusions: This study expands the current knowledge regarding the trend of CPK values and cardiac and respiratory impairment in patients with LGMDR4, to optimize the monitoring of these patients, to improve their quality of life, and to provide clinical indices capable of quantifying the effects of any new gene or drug therapy.

A Journey with LGMD: From Protein Abnormalities to Patient Impact

The limb-girdle muscular dystrophies (LGMD) are a collection of genetic diseases united in their phenotypical expression of pelvic and shoulder area weakness and wasting. More than 30 subtypes have been identified, five dominant and 26 recessive. The increase in the characterization of new genotypes in the family of LGMDs further adds to the heterogeneity of the disease. Meanwhile, better understanding of the phenotype led to the reconsideration of the disease definition, which resulted in eight old subtypes to be no longer recognized officially as LGMD and five new diseases to be added to the LGMD family. The unique variabilities of LGMD stem from genetic mutations, which then lead to protein and ultimately muscle dysfunction. Herein, we review the LGMD pathway, starting with the genetic mutations that encode proteins involved in muscle maintenance and repair, and including the genotype–phenotype relationship of the disease, the epidemiology, disease progression, burden of illness, and emerging treatments.

TRIM32: A Multifunctional Protein Involved in Muscle Homeostasis, Glucose Metabolism, and Tumorigenesis

Human tripartite motif family of proteins 32 (TRIM32) is a ubiquitous multifunctional protein that has demonstrated roles in differentiation, muscle physiology and regeneration, and tumor suppression. Mutations in TRIM32 result in two clinically diverse diseases. A mutation in the B-box domain gives rise to Bardet–Biedl syndrome (BBS), a disease whose clinical presentation shares no muscle pathology, while mutations in the NHL (NCL-1, HT2A, LIN-41) repeats of TRIM32 causes limb-girdle muscular dystrophy type 2H (LGMD2H). TRIM32 also functions as a tumor suppressor, but paradoxically is overexpressed in certain types of cancer. Recent evidence supports a role for TRIM32 in glycolytic-mediated cell growth, thus providing a possible mechanism for TRIM32 in the accumulation of cellular biomass during regeneration and tumorigenesis, including in vitro and in vivo approaches, to understand the broad spectrum of TRIM32 functions. A special emphasis is placed on the utility of the Drosophila model, a unique system to study glycolysis and anabolic pathways that contribute to the growth and homeostasis of both normal and tumor tissues.

Muscle Diversity, Heterogeneity, and Gradients: Learning from Sarcoglycanopathies

Skeletal muscle, the most abundant tissue in the body, is heterogeneous. This heterogeneity forms the basis of muscle diversity, which is reflected in the specialized functions of muscles in different parts of the body. However, these different parts are not always clearly delimitated, and this often gives rise to gradients within the same muscle and even across the body. During the last decade, several studies on muscular disorders both in mice and in humans have observed particular distribution patterns of muscle weakness during disease, indicating that the same mutation can affect muscles differently. Moreover, these phenotypical differences reveal gradients of severity, existing alongside other architectural gradients. These two factors are especially prominent in sarcoglycanopathies. Nevertheless, very little is known about the mechanism(s) driving the phenotypic diversity of the muscles affected by these diseases. Here, we will review the available literature on sarcoglycanopathies, focusing on phenotypic differences among affected muscles and gradients, characterization techniques, molecular signatures, and cell population heterogeneity, highlighting the possibilities opened up by new technologies. This review aims to revive research interest in the diverse disease phenotype affecting different muscles, in order to pave the way for new therapeutic interventions.

Preclinical Systemic Delivery of Adeno-Associated α-Sarcoglycan Gene Transfer for Limb-Girdle Muscular Dystrophy

Limb-girdle muscular dystrophy type 2D/R3 (LGMD2D/R3) is a progressive muscular dystrophy that manifests with muscle weakness, respiratory abnormalities, and in rare cases cardiomyopathy. LGMD2D/R3 is caused by mutations in the SGCA gene resulting in loss of protein and concomitant loss of some or all components of the dystrophin-associated glycoprotein complex. The sgca-null (sgca^−/−) mouse recapitulates the clinical phenotype of patients with LGMD2D/R3, including dystrophic features such as muscle necrosis and fibrosis, elevated serum creatine kinase (CK), and reduction in the generation of absolute muscle force and locomotor activity. Thus, sgca^−/− mice provide a relevant model to test the safety and efficacy of gene transfer. We designed a self-complementary AAVrh74 vector containing a codon-optimized full-length human SGCA (hSGCA) transgene driven by a muscle-specific promoter, shortened muscle creatine kinase (tMCK). In this report, we test the efficacy and safety of scAAVrh74.tMCK.hSGCA in sgca^−/− mice using a dose-escalation design to evaluate a single systemic injection of 1.0 × 10¹², 3.0 × 10¹², and 6.0 × 10¹² vg total dose compared with vehicle-treatment and wild-type mice. In sgca^−/− mice, treatment with scAAVrh74.tMCK.hSGCA resulted in robust expression of α-sarcoglycan protein at the sarcolemma membrane in skeletal muscle at all doses tested. In addition, scAAVrh74.tMCK.hSGCA was effective in improving the histopathology of limb and diaphragm muscle of sgca^−/− mice, as indicated by reductions in fibrosis, central nucleation, and normalization of myofiber size. These molecular changes were concomitant with significant increases in specific force generation in the diaphragm and tibialis anterior muscle, protection against eccentric force loss, and reduction in serum CK. Locomotor activity was improved at all doses of vector-treated compared with vehicle-treated sgca^−/− mice. Lastly, vector toxicity was not detected in a serum chemistry panel and by gross necropsy. Collectively, these findings provide support for a systemic delivery of scAAVrh74.tMCK.hSGCA in a clinical setting for the treatment of LGMD2D/R3.

Circulating miR-206 as a Biomarker for Patients Affected by Severe Limb Girdle Muscle Dystrophies

Limb-girdle muscular dystrophies (LGMD) are clinically and genetically heterogeneous conditions, presenting with a wide clinical spectrum, leading to progressive proximal weakness caused by loss of muscle fibers. MiR-206 is a member of myomiRNAs, a group of miRNAs with important function in skeletal muscle. Our aim is to determine the value of miR-206 in detecting muscle disease evolution in patients affected by LGMD. We describe clinical features, disease history and progression of eleven patients affected by various types of LGMD: transportinopathy, sarcoglycanopathy and calpainopathy. We analyzed the patients’ mutations and we studied the circulating miR-206 in serum by qRT-PCR; muscle MRI was done with a 1.5 Tesla apparatus. The severe evolution of disease type is associated with the expression levels of miR-206, which was significantly elevated in our LGMD patient cohort in comparison with a control group. In particular, we observed an over-expression of miR-206 that was 50–80 folds elevated in two patients with a severe and early disease course in the transportinopathy and calpainopathy sub-types. The functional impairment was observed clinically and muscle loss and atrophy documented by muscle MRI. This study provides the first evidence that miR-206 is associated with phenotypic expression and it could be used as a prognostic indicator of LGMD disease progression.

User-centred assistive SystEm for arm Functions in neUromuscuLar subjects (USEFUL): a randomized controlled study

Background

Upper limb assistive devices can compensate for muscular weakness and empower the user in the execution of daily activities. Multiple devices have been recently proposed but there is still a lack in the scientific comparison of their efficacy.

Methods

We conducted a cross-over multi-centric randomized controlled trial to assess the functional improvement at the upper limb level of two arms supports on 36 patients with muscular dystrophy. Participants tested a passive device (i.e., Wrex by Jaeco) and a semi-active solution for gravity compensation (i.e., Armon Ayura). We evaluated devices’ effectiveness with an externally-assessed scale (i.e., Performance of the Upper Limb-PUL-module), a self-perceived scale (i.e., Abilhand questionnaire), and a usability scale (i.e., System Usability Scale). Friedman’s test was used to assess significant functional gain for PUL module and Abilhand questionnaire. Moreover, PUL changes were compared by means of the Friedman’s test.

Results

Most of the patients improved upper limb function with the use of arm supports (median PUL scores increase of 1–3 points). However, the effectiveness of each device was related to the level of residual ability of the end-user. Slightly impaired patients maintained the same independence without and with assistive devices, even if they reported reduced muscular fatigue for both devices. Moderately impaired patients enhanced their arm functionality with both devices, and they obtained higher improvements with the semi-active one (median PUL scores increase of 9 points). Finally, severely impaired subjects benefited only from the semi-active device (median PUL scores increase of 12 points). Inadequate strength was recognized as a barrier to passive devices. The usability, measured by the System Usability Scale, was evaluated by end-users “good” (70/100 points) for the passive, and “excellent” (80/100 points) for the semi-active device.

Conclusions

This study demonstrated that assistive devices can improve the quality of life of people suffering from muscular dystrophy. The use of passive devices, despite being low cost and easy to use, shows limitations in the efficacy of the assistance to daily tasks, limiting the assistance to a predefined horizontal plane. The addition of one active degree of freedom improves efficacy and usability especially for medium to severe patients. Further investigations are needed to increase the evidence on the effect of arm supports on quality of life and diseases’ progression in subjects with degenerative disorders.

Trial registration clinicaltrials.gov, NCT03127241, Registered 25th April 2017. The clinical trial was also registered as a post-market study at the Italian Ministry of Health.

Costameric integrin and sarcoglycan protein levels are altered in a Drosophila model for Limb-girdle muscular dystrophy type 2H

Mutations in two different domains of the ubiquitously expressed TRIM32 protein give rise to two clinically separate diseases, one of which is Limb-girdle muscular dystrophy type 2H (LGMD2H). Uncovering the muscle-specific role of TRIM32 in LGMD2H pathogenesis has proven difficult, as neurogenic phenotypes, independent of LGMD2H pathology, are present in TRIM32 KO mice. We previously established a platform to study LGMD2H pathogenesis using Drosophila melanogaster as a model. Here we show that LGMD2H disease-causing mutations in the NHL domain are molecularly and structurally conserved between fly and human TRIM32. Furthermore, transgenic expression of a subset of myopathic alleles (R394H, D487N, and 520fs) induce myofibril abnormalities, altered nuclear morphology, and reduced TRIM32 protein levels, mimicking phenotypes in patients afflicted with LGMD2H. Intriguingly, we also report for the first time that the protein levels of βPS integrin and sarcoglycan δ, both core components of costameres, are elevated in TRIM32 disease-causing alleles. Similarly, murine myoblasts overexpressing a catalytically inactive TRIM32 mutant aberrantly accumulate α- and β-dystroglycan and α-sarcoglycan. We speculate that the stoichiometric loss of costamere components disrupts costamere complexes to promote muscle degeneration.

Genetically confirmed limb-girdle muscular dystrophy type 2B with DYSF mutation using gene panel sequencing: A case report

RATIONALE

The limb-girdle muscular dystrophies (LGMDs) are a heterogeneous group of disorders characterized by progressive proximal muscle weakness and have more than 30 different subtypes linked to specific gene loci, which manifest as highly overlapping and heterogeneous phenotypes.

PATIENT CONCERNS

A 59-year-old male presented for evaluation of progressive muscle weakness since his late twenties. When he was 38 years old, he had muscle weakness in the upper extremities and had a waddling gait, hyper lordosis of lower back, and anterior pelvic tilt. His gait disturbance and muscle weakness slowly progressed. When he was 55 years old, he could not walk at all and had to use a wheelchair for ambulation.

DIAGNOSIS

Next-generation sequencing using a custom target capture-based gene panel including specific genes responsible for muscular dystrophy was performed. As a result, the proband was genetically diagnosed as LGMD type 2B, carrying 2 compound heterozygous mutations (NM_003494.3:c.1663C>T, p.Arg555Trp; rs377735262 and NM_003494.3:c.2997G>T, p.Trp999Cys; rs28937581) of the DYSF gene.

INTERVENTIONS

Physical and occupational therapy were prescribed properly for the first time Bracing and assistive devices were adapted specifically to the patient's deficiencies to preserve mobility and function and prevent contractures.

OUTCOMES

The patient with LGMD has periodic assessments of physical and occupational therapy for the prevention and management of comorbidities. However, in the 3 years after the gene panel sequencing diagnoses, his weakness was slowly progress and the patient still could not walk.

LESSONS

Gene panel sequencing allows for the correct recognition of different LGMD subtypes, improving timely treatment, management, and enrolment of molecularly diagnosed individuals in clinical trials.

Calpainopathy: Description of a Novel Mutation and Clinical Presentation with Early Severe Contractures

Presented here are five members of a family that was ascertained from an isolated, consanguineous, indigenous Amerindian community in Colombia that was affected with calpain 3-related, limb-girdle muscular dystrophy type R1. These patients are homozygous for a unique and novel deletion of four bases (TGCC) in exon 3 of the calpain 3 gene (CAPN3) (NM_000070.2; NP_000061.1) (g.409_412del). The mutation site occurs at the CysPc protein domain, triggering a modified truncated protein structure and affecting motifs within the calpain-like thiol protease family (peptidase family C2) region. The patients reported here developed a very severe phenotype with primary contractures, spinal rigidity in the early stages of the disease, and bilateral talipes equinovarus (clubfoot) in the most affected patients who had the selective involvement of their extremities’ distal muscles in a way that resembled Emery–Dreifuss syndrome. We recommend mandatory screening for calpainopathy in all patients with an Emery–Dreifuss-like syndrome or those presenting a non-congenital illness with primary contractures and who, because of other data, are suspected of having muscular dystrophy.

Gene transfer to skeletal muscle using hydrodynamic limb vein injection: current applications, hurdles and possible optimizations

Hydrodynamic limb vein injection is an in vivo locoregional gene delivery method. It consists of administrating a large volume of solution containing nucleic acid constructs in a limb with both blood inflow and outflow temporarily blocked using a tourniquet. The fast, high pressure delivery allows the musculature of the whole limb to be reached. The skeletal muscle is a tissue of choice for a variety of gene transfer applications, including gene therapy for Duchenne muscular dystrophy or other myopathies, as well as for the production of antibodies or other proteins with broad therapeutic effects. Hydrodynamic limb vein delivery has been evaluated with success in a large range of animal models. It has also proven to be safe and well-tolerated in muscular dystrophy patients, thus supporting its translation to the clinic. However, some possible limitations may occur at different steps of the delivery process. Here, we have highlighted the interests, bottlenecks and potential improvements that could further optimize non-viral gene transfer following hydrodynamic limb vein injection.

Muscular dystrophies

Muscular dystrophies are primary diseases of muscle due to mutations in more than 40 genes, which result in dystrophic changes on muscle biopsy. Now that most of the genes responsible for these conditions have been identified, it is possible to accurately diagnose them and implement subtype-specific anticipatory care, as complications such as cardiac and respiratory muscle involvement vary greatly. This development and advances in the field of supportive medicine have changed the standard of care, with an overall improvement in the clinical course, survival, and quality of life of affected individuals. The improved understanding of the pathogenesis of these diseases is being used for the development of novel therapies. In the most common form, Duchenne muscular dystrophy, a few personalised therapies have recently achieved conditional approval and many more are at advanced stages of clinical development. In this Seminar, we concentrate on clinical manifestations, molecular pathogenesis, diagnostic strategy, and therapeutic developments for this group of conditions.

Cross-sectional study into age-related pathology of mouse models for limb girdle muscular dystrophy types 2D and 2F

Limb girdle muscular dystrophy (LGMD) types 2D and 2F are caused by mutations in the genes encoding for α- and δ-sarcoglycan, respectively, leading to progressive muscle weakness. Mouse models exist for LGMD2D (Sgca-/-) and 2F (Sgcd-/-). In a previous natural history study, we described the pathology in these mice at 34 weeks of age. However, the development of muscle pathology at younger ages has not been fully characterised yet. We therefore performed a study into age-related changes in muscle function and pathology by examining mice at different ages. From 4 weeks of age onwards, male mice were subjected to functional tests and sacrificed at respectively 8, 16 or 24 weeks of age. Muscle histopathology and expression of genes involved in muscle pathology were analysed for several skeletal muscles, while miRNA levels were assessed in serum. In addition, for Sgcd-/- mice heart pathology was assessed. Muscle function showed a gradual decline in both Sgca-/- and Sgcd-/- mice. Respiratory function was also impaired at all examined timepoints. Already at 8 weeks of age, muscle pathology was prominent, and fibrotic, inflammatory and regenerative markers were elevated, which remained relatively constant with age. In addition, Sgcd-/- mice showed signs of cardiomyopathy from 16 weeks of age onwards. These results indicate that Sgca-/- and Sgcd-/- are relevant disease models for LGMD2D and 2F.

Anesthetic management of a patient with limb-girdle muscular dystrophy 2B:CARE-compliant case report and literature review

Background

Limb-girdle muscular dystrophies (LGMDs) belong to few neuromuscular disorders mainly involving pelvic and shoulder girdle muscles. Also, cardiac or pulmonary complications, increased rhabdomyolysis risk when exposed to volatile anesthetics and succinylcholine may increase anesthesia related risks. However, current reports about the anesthesia management of these patients are limited.

Case presentation

We described our anesthetic management of a 36 years old woman with LGMD 2B receiving arthroscopic knee surgery. In consideration of the high risk of rhabdomyolysis, total intravenous anesthesia (TIVA) was selected for her surgery. Considering the unpredictable respiratory depression, opioid based patient-controlled intravenous analgesia was replaced with an intra-articular cocktail therapy consisting of 20 ml of 0.2% ropivacaine. Also, we reviewed the literatures on anesthetic management of LGMD through searching PubMed, in order to provide a comprehensive and safe guidance for the surgery.

Conclusions

Carefully conducted general anesthesia with TIVA technique is a good choice for LGMD patients. Neuraxial anesthesia may be used if general anesthesia needs to be avoided. To warrant safe anesthesia for surgery, any decision must be well thought out during perioperative period.

LMNA-Related Muscular Dystrophy with Clinical Intrafamilial Variability

The LMNA gene is associated to a huge broad of phenotypes, including congenital Emery-Dreifuss muscular dystrophy and late-onset LMNA-related muscular dystrophy. In these forms, muscle weakness, contractures, and cardiac impairment are common. In an autosomal dominant pedigree including 5 affected patients, NGS molecular analysis performed in 6 relatives identifies the heterozygous c.1129C>T p.Arg377Cys variant in the exon 6 of the LMNA gene in three of them. Clinical, laboratorial, imaging investigation of these affected patients showed a significant clinical variability: the father presented subclinical imaging muscular dystrophy masqueraded as radiculopathy. One of his sons presented cardiac arrhythmia, muscular weakness, elbow contractures, and intranuclear pseudoinclusions on muscle biopsy. A second son presented only decreased tendon reflexes. Two other brothers presenting myalgia and cramps were not carriers of the same mutation in the LMNA gene. Early diagnosis, considering these variable phenotype and genotype, is important for genetic counseling, as well as cardiac, and rehabilitation management.

Preliminary Evidences of Safety and Efficacy of Flavonoids- and Omega 3-Based Compound for Muscular Dystrophies Treatment: A Randomized Double-Blind Placebo Controlled Pilot Clinical Trial

Background: Nutritional compounds can exert both anti-inflammatory and anti-oxidant effects. Since these events exacerbate the pathophysiology of muscular dystrophies, we investigated nutraceutical supplementation as an adjuvant therapy in dystrophic patients, to low costs and easy route of administration. Moreover, this treatment could represent an alternative therapeutic strategy for dystrophic patients who do not respond to corticosteroid treatment.

Objective: A 24 weeks randomized double-blind placebo-controlled clinical study was aimed at evaluating the safety and efficacy of daily oral administration of flavonoids- and omega3-based natural supplement (FLAVOMEGA) in patients affected by muscular dystrophy with recognized muscle inflammation.

Design: We screened 60 patients diagnosed for Duchenne (DMD), Facioscapulohumeral (FSHD), and Limb Girdle Muscular Dystrophy (LGMD). Using a computer-generated random allocation sequence, we stratified patients in a 2:1:1 ratio (DMD:FSHD:LGMD) to one of two treatment groups: continuous FLAVOMEGA, continuous placebo. Of 29 patients included, only 24 completed the study: 15 were given FLAVOMEGA, 14 placebo.

Results: FLAVOMEGA was well tolerated with no reported adverse events. Significant treatment differences in the change from baseline in 6 min walk distance (6MWD; secondary efficacy endpoint) (P = 0.033) and in isokinetic knee extension (P = 0.039) (primary efficacy endpoint) were observed in LGMD and FSHD subjects. Serum CK levels (secondary efficacy endpoint) decreased in all FLAVOMEGA treated groups with significant difference in DMD subjects (P = 0.039).

Conclusions: Although the small number of patients and the wide range of disease severity among patients reduced statistical significance, we obtained an optimal profile of safety and tolerability for the compound, showing valuable data of efficacy in primary and secondary endpoints.

Trial registration number: NCT03317171

Retrospectively registered 25/10/2017

Sarcoglycan Alpha Mitigates Neuromuscular Junction Decline in Aged Mice by Stabilizing LRP4

During aging, acetylcholine receptor (AChR) clusters become fragmented and denervated at the neuromuscular junction (NMJ). Underpinning molecular mechanisms are not well understood. We showed that LRP4, a receptor for agrin and critical for NMJ formation and maintenance, was reduced at protein level in aged mice, which was associated with decreased MuSK tyrosine phosphorylation, suggesting compromised agrin-LRP4-MuSK signaling in aged muscles. Transgenic expression of LRP4 in muscles alleviated AChR fragmentation and denervation and improved neuromuscular transmission in aged mice. LRP4 ubiquitination was augmented in aged muscles, suggesting increased LRP4 degradation as a mechanism for reduced LRP4. We found that sarcoglycan α (SGα) interacted with LRP4 and delayed LRP4 degradation in cotransfected cells. AAV9-mediated expression of SGα in muscles mitigated AChR fragmentation and denervation and improved neuromuscular transmission in aged mice. These observations support a model where compromised agrin-LRP4-MuSK signaling serves as a pathological mechanism of age-related NMJ decline and identify a novel function of SGα in stabilizing LRP4 for NMJ stability in aged mice.SIGNIFICANCE STATEMENT This study provides evidence that LRP4, a receptor of agrin that is critical for NMJ formation and maintenance, is reduced at protein level in aged muscles. Transgenic expression of LRP4 in muscles ameliorates AChR fragmentation and denervation and improves neuromuscular transmission in aged mice, demonstrating a critical role of the agrin-LRP4-MuSK signaling. Our study also reveals a novel function of SGα to prevent LRP4 degradation in aged muscles. Finally, we show that NMJ decline in aged mice can be mitigated by AAV9-mediated expression of SGα in muscles. These observations provide insight into pathological mechanisms of age-related NMJ decline and suggest that improved agrin-LRP4-MuSK signaling may be a target for potential therapeutic intervention.

Myoediting: Toward Prevention of Muscular Dystrophy by Therapeutic Genome Editing

Muscular dystrophies represent a large group of genetic disorders that significantly impair quality of life and often progress to premature death. There is no effective treatment for these debilitating diseases. Most therapies, developed to date, focus on alleviating the symptoms or targeting the secondary effects, while the underlying gene mutation is still present in the human genome. The discovery and application of programmable nucleases for site-specific DNA double-stranded breaks provides a powerful tool for precise genome engineering. In particular, the CRISPR/Cas system has revolutionized the genome editing field and is providing a new path for disease treatment by targeting the disease-causing genetic mutations. In this review, we provide a historical overview of genome-editing technologies, summarize the most recent advances, and discuss potential strategies and challenges for permanently correcting genetic mutations that cause muscular dystrophies.

Development of muscular dystrophy in a CRISPR-engineered mutant rabbit model with frame-disrupting ANO5 mutations

Limb girdle muscular dystrophy type 2L (LGMD2L) and Miyoshi myopathy type 3 (MMD3) are autosomal recessive muscular dystrophy caused by mutations in the gene encoding anoctamin-5 (ANO5), which belongs to the anoctamin protein family. Two independent lines of mice with complete disruption of ANO5 transcripts did not exhibit overt muscular dystrophy phenotypes; instead, one of these mice was observed to present with some abnormality in sperm motility. In contrast, a third line of ANO5-knockout (KO) mice with residual expression of truncated ANO5 expression was reported to display defective membrane repair and very mild muscle pathology. Many of the ANO5-related patients carry point mutations or small insertions/deletions (indels) in the ANO5 gene. To more closely mimic the human ANO5 mutations, we engineered mutant ANO5 rabbits via co-injection of Cas9 mRNA and sgRNA into the zygotes. CRISPR-mediated small indels in the exon 12 and/or 13 in the mutant rabbits lead to the development of typical signs of muscular dystrophy with increased serum creatine kinase (CK), muscle necrosis, regeneration, fatty replacement and fibrosis. This novel ANO5 mutant rabbit model would be useful in studying the disease pathogenesis and therapeutic treatments for ANO5-deficient muscular dystrophy.

Factors affecting the health-related quality of life of caregivers of patients with muscular dystrophy

Muscular dystrophy (MD) is a group of progressive muscle weakness diseases. The caregiver burden, increasing as the disease progresses, can be associated with impaired health-related quality of life (HRQOL). The aims of this study were to investigate the HRQOL in caregivers of patients with MD and identify the factors associated with HRQOL. A cross-sectional assessment of caregiver HRQOL was performed with the Short Form-36 and compared with norms. The factors affecting HRQOL were investigated by patient and caregiver characteristics. The Muscular Dystrophy Functional Rating Scale was used to assess the functional status (mobility, basic activities of daily living, arm function, and impairment) of patients. The demographic data and social interaction activities of caregivers were assessed. Caregivers (n = 62) had poor HRQOL. Caregiver HRQOL was associated with the patient's functional status, especially in the domains of Vitality and Mental Health. Numerous visits by neighbors and close friends of the caregiver family indicated better HRQOL (in the body pain, general health, vitality, role emotion and mental health domains). Caregiver HRQOL was associated with caregiver education level, while patient age, caregiver age, length of caregiving, and family income were not. These findings demonstrate that caregivers have poor HRQOL, and the mental domain of quality of life is associated with the patient's functional status, social interaction, and caregiver education level. We suggest that rehabilitation programs focus on caregiver HRQOL, promote the patient's functional status with assistive technology, enhance professional caring techniques, and encourage participation in social groups to improve caregiver HRQOL.

Untangling the complexity of limb-girdle muscular dystrophies

The limb-girdle muscular dystrophies (LGMDs) are a group of genetically heterogeneous, autosomal inherited muscular dystrophies with a childhood to adult onset, manifesting with hip- and shoulder-girdle muscle weakness. When the term LGMD was first conceptualized in 1954, it was thought to be a single entity. Currently, there are 8 autosomal dominant (LGMD1A-1H) and 26 autosomal recessive (LGMD2A-2Z) variants according to the Online Mendelian Inheritance in Man database. In addition, there are other genetically identified muscular dystrophies with an LGMD phenotype not yet classified as LGMD. This highlights the entanglement of LGMDs, which represents an area in continuous expansion. Herein we aim to simplify the complexity of LGMDs by subgrouping them on the basis of the underlying defective protein and impaired function. Muscle Nerve 58: 167-177, 2018.