Limb-girdle Dystrophy Type Research Articles

Dosage-Adjusted Resistance Training in Mice with a Reduced Risk of Muscle Damage.

Progressive resistance training (PRT), which involves performing muscle contractions against progressively greater external loads, can increase muscle mass and strength in healthy individuals and in patient populations. There is a need for precision rehabilitation tools to test the safety and effectiveness of PRT to maintain and/or restore muscle mass and strength in preclinical studies on small and large animal models. The PRT methodology and device described in this article can be used to perform dosage-adjusted resistance training (DART). The DART device can be used as a standalone dynamometer to objectively assess the concentric contractile torque generated by the ankle dorsiflexors in mice or can be added to a pre-existing isokinetic dynamometry system. The DART device can be fabricated with a standard 3D printer based on the instructions and open-source 3D print files provided in this work. The article also describes the workflow for a study to compare contraction-induced muscle damage caused by a single bout of DART to muscle damage caused by a comparable bout of isometric contractions (ISOM) in a mouse model of limb-girdle muscular dystrophy type 2B/R2 (BLAJ mice). The data from eight BLAJ mice (four animals for each condition) suggest that less than 10% of the tibialis anterior (TA) muscle was damaged from a single bout of DART or ISOM, with DART being less damaging than ISOM.

Recurrent, non-traumatic, non-exertional rhabdomyolysis after immunologic stimuli in a healthy adolescent female: a case report

BackgroundDysferlinopathy refers to a heterogenous group of autosomal recessive disorders that affect a skeletal muscle protein called dysferlin. These mutations are associated with limb-girdle muscular dystrophy type 2B, Miyoshi myopathy, asymptomatic hyperCKemia, and distal myopathy with anterior tibial onset.Case presentationA 16 year old female presented with myalgia, weakness and dark urine one week after her second BNT162b2 mRNA (Pfizer) vaccine. Initial serum creatine kinase (CK) was measured at 153,000 IU/L, eventually up-trending to over 200,000 IU/L. However, stable renal function precluded hemodialysis allowing discharge after 10 days of intravenous (IV) hydration and alkaline diuresis.Just two years prior to the current presentation, the patient was hospitalized following Group A Streptococcal pharyngitis infection complicated by rhabdomyolysis. She presented with fatigue, lower extremity weakness, and dark oliguria with CK measuring 984,800 IU/L. IV hydration was attempted however hemodialysis was ultimately required throughout her 24-day hospital stay. Her episode was presumed to be idiopathic and no further work-up was performed at that time.During the patient’s current hospitalization, she reported similar symptomology (myalgias and weakness) following her first quadrivalent Gardasil vaccine at age 11. No hospitalization was required at that time. A comprehensive workup was now initiated while the patient was being treated for her suspected second or third non-exertional, non-traumatic rhabdomyolysis. Rheumatologic, metabolic, infectious, and endocrinologic workup were all unremarkable. Patient eventually had whole exome sequencing performed which revealed a heterozygous pathogenic variant in the DYSF gene (DYSF c.2643 + 1G > A) encoding dysferlin. No clinically significant sequelae occurred thus far.ConclusionsWhile there have been reports of symptomatic heterozygote carriers of dysferlinopathies, to our knowledge none have been associated with recurrent rhabdomyolysis after immunogenic stimuli. This unique case presentation highlights the importance of a multi-disciplinary care team, the utility of modern whole-exome gene sequencing, and the future challenges of balancing vaccine risk vs benefit.

Whole‐Body MRI in Limb Girdle Muscular Dystrophy Type R1/2A: Correlation With Clinical Scores

The most common limb girdle muscular dystrophy (LGMD) worldwide is LGMD type R1 (LGMDR1). The aim of this study was to correlate the magnetic resonance imaging (MRI) findings with functional scores and to describe the whole-body MRI (WBMRI) pattern in a LGMDR1 Brazilian cohort. LGMDR1 patients under follow-up in three centers were referred for the study. Clinical data were collected and a functional evaluation was performed, consisting of Gardner-Medwin and Walton (GMW) and Brooke scales. All patients underwent a WBMRI study (1.5T) with axial T1 and STIR images. Fifty-one muscles were semiquantitatively assessed regarding fatty infiltration and muscle edema. The study group consisted of 18 patients. The highest fatty infiltration scores involved the serratus anterior, biceps femoris long head, adductor magnus and lumbar erector spinae. There was a latero-medial and caudo-cranial descending gradient of involvement of the paravertebral muscles, with erector spinae being significantly more affected than the transversospinalis muscles (p<0.05). A striped appearance that has been dubbed the "pseudocollagen sign" was present in 72% of the patients. There was a positive correlation between the MRI score and GMW (Rho:0.83) and Brooke (Rho:0.53) scores. WBMRI in LGMDR1 allows a global patient evaluation including involvement of the paraspinal muscles, usually an underestimated feature in the clinical and imaging study of myopathies. Knowledge of the WBMRI pattern of LGMDR1 involvement can be useful in the diagnostic approach and in future studies to identify the best target muscles to serve as outcome measures in clinical trials.

Disease-associated mutations within the yeast DNAJB6 homolog Sis1 slow conformer-specific substrate processing and can be corrected by the modulation of nucleotide exchange factors

Molecular chaperones, or heat shock proteins (HSPs), protect against the toxic misfolding and aggregation of proteins. As such, mutations or deficiencies within the chaperone network can lead to disease. Dominant mutations within DNAJB6 (Hsp40)—an Hsp70 co-chaperone—lead to a protein aggregation-linked myopathy termed Limb-Girdle Muscular Dystrophy Type D1 (LGMDD1). Here, we used the yeast prion model client in conjunction with in vitro chaperone activity assays to gain mechanistic insights into the molecular basis of LGMDD1. Here, we show how mutations analogous to those found in LGMDD1 affect Sis1 (a functional homolog of human DNAJB6) function by altering the structure of client protein aggregates, interfering with the Hsp70 ATPase cycle, dimerization and substrate processing; poisoning the function of wild-type protein. These results uncover the mechanisms through which LGMDD1-associated mutations alter chaperone activity, and provide insights relevant to potential therapeutic interventions.

Limb-girdle muscular dystrophy type 2J: case report

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Dual Blockade of Misfolded Alpha-Sarcoglycan Degradation by Bortezomib and Givinostat Combination.

Limb-girdle muscular dystrophy type R3 (LGMD R3) is a rare genetic disorder characterized by a progressive proximal muscle weakness and caused by mutations in the SGCA gene encoding alpha-sarcoglycan (α-SG). Here, we report the results of a mechanistic screening ascertaining the molecular mechanisms involved in the degradation of the most prevalent misfolded R77C-α-SG protein. We performed a combinatorial study to identify drugs potentializing the effect of a low dose of the proteasome inhibitor bortezomib on the R77C-α-SG degradation inhibition. Analysis of the screening associated to artificial intelligence-based predictive ADMET characterization of the hits led to identification of the HDAC inhibitor givinostat as potential therapeutical candidate. Functional characterization revealed that givinostat effect was related to autophagic pathway inhibition, unveiling new theories concerning degradation pathways of misfolded SG proteins. Beyond the identification of a new therapeutic option for LGMD R3 patients, our results shed light on the potential repurposing of givinostat for the treatment of other genetic diseases sharing similar protein degradation defects such as LGMD R5 and cystic fibrosis.

Generation of Calpain-3 knock-out porcine embryos by CRISPR-Cas9 electroporation and intracytoplasmic microinjection of oocytes before insemination

Limb girdle muscular dystrophy type R1 (LGMDR1) is an autosomal recessive myopathy described in humans resulting from a deficiency of calpain-3 protein (CAPN3). This disease lacks effective treatment and an appropriate model, so the generation of KO pigs by CRISPR-Cas9 offers a way to better understand disease ethology and to develop novel therapies. Microinjection is the main method described for gene editing by CRISPR-Cas9 in porcine embryo, but electroporation, which allows handling more embryos faster and easier, has also recently been reported. The objective of the current study was to optimize porcine oocyte electroporation to maximize embryo quality and mutation rate in order to efficiently generate LGMDR1 porcine models. We found that the efficiency of generating CAPN3 KO embryos was highest with 4 electroporation pulses and double sgRNA concentration than microinjection. Direct comparison between microinjection and electroporation demonstrated similar rates of embryo development and mutation parameters. The results of our study demonstrate that oocyte electroporation, an easier and faster method than microinjection, is comparable to standard approaches, paving the way for democratization of transgenesis in pigs.

Serum miRNAs as biomarkers for the rare types of muscular dystrophy

Muscular dystrophies are a group of disorders that cause progressive muscle weakness. There is an increasing interest for the development of biomarkers for these disorders and specifically for Duchene Muscular Dystrophy. Limited research however, has been performed on the biomarkers’ development for the most rare muscular dystrophies, like the Facioscapulohumeral Muscular Dystrophy, Limb-Girdle Muscular Dystrophy and Myotonic Dystrophy type 2. Here, we aimed to identify novel serum-based miRNA biomarkers for these rare muscular dystrophies, through high-throughput next-generation RNA sequencing. We identified many miRNAs that associate with muscular dystrophy patients compared to controls. Based on a series of selection criteria, the two best candidate miRNAs for each of these disorders were chosen and validated in a larger number of patients. Our results showed that miR-223-3p and miR-206 are promising serum-based biomarkers for Facioscapulohumeral Muscular Dystrophy type 1, miR-143-3p and miR-486-3p for Limb-Girdle Muscular Dystrophy type 2A whereas miR-363-3p and miR-25-3p associate with Myotonic Dystrophy type 2. Some of the identified miRNAs were significantly elevated in the serum of the patients compared to controls, whereas some others were lower. In conclusion, we provide new evidence that certain circulating miRNAs may be used as biomarkers for three types of rare muscular dystrophies.

The therapeutic potential of soluble activin type IIB receptor treatment in a limb girdle muscular dystrophy type 2D mouse model

Limb girdle muscular dystrophy type 2D (LGMD2D) is characterized by progressive weakening of muscles in the hip and shoulder girdles. It is caused by a mutation in the α-sarcoglycan gene and results in absence of α-sarcoglycan in the dystrophin-glycoprotein complex. The activin type IIB receptor is involved in the activin/myostatin pathway, with myostatin being a negative regulator of muscle growth. In this study, we investigated the effects of sequestering myostatin by a soluble activin type IIB receptor (sActRIIB) on muscle growth in Sgca-null mice, modelling LGMD2D. Treatment was initiated at 3 weeks of age, prior to the disease onset, or at 9 weeks of age when already in an advanced stage of the disease. We found that early sActRIIB treatment resulted in increased muscle size. However, this led to more rapid decline of muscle function than in saline-treated Sgca-null mice. Furthermore, no histopathological improvements were seen after sActRIIB treatment. When initiated at 9 weeks of age, sActRIIB treatment resulted in increased muscle mass too, but to a lesser extent. No effect of the treatment was observed on muscle function or histopathology. These data show that sActRIIB treatment as a stand-alone therapy does not improve muscle function or histopathology in Sgca-null mice.

A Novel Gene Therapy Shows Promise for Limb Girdle Muscular Dystrophy Type 2B

A Novel Gene Therapy Shows Promise for Limb Girdle Muscular Dystrophy Type 2B

Novel compound heterozygous mutations in the TTN gene: elongation and truncation variants causing limb-girdle muscular dystrophy type 2J in a Han Chinese family.

Limb-girdle muscular dystrophy (LGMD) is a group of clinically heterogeneous muscle disorders commonly manifesting proximal limb girdle muscle weakness. There have been more than 30 subtypes of LGMD associated with causative genes and limb-girdle muscular dystrophy type 2J (LGMD2J) is caused by mutations in the TTN gene. We report a Han Chinese family with LGMD2J. The proband and his sister both presented with weakness in the proximal lower limbs bilaterally. Muscle biopsy and genetic analysis were performed. Muscle biopsy of the proband showed dystrophic changes accompanied by rimmed vacuoles. Whole-exome sequencing identified novel compound heterozygous mutations in the TTN gene, including elongation (c.107962_107963delAT, p.I35988Sfs*26) and truncation (c.99125_99128dupACAG, p.S33043Rfs*9) variants in the proband and his sister. Both two variants have never been reported. Notably, we are the first to identify an elongation mutation in the TTN gene, broadening the genetic mutation spectrum of LGMD2J. Several variants in the last exon of the TTN gene have been reported, one of which was associated with LGMD2J. Besides, LGMD2J should be distinguished from other myopathies caused by mutations in the TTN gene. The pathogenesis of and specific curative methods for LGMD2J remain to be further elucidated.

Homozygous missense variant in POPDC3 causes recessive limb-girdle muscular dystrophy type 26.

Limb-girdle muscular dystrophy (LGMD) comprises a heterogeneous group of diseases, affecting different muscles, predominantly skeletal muscles and cardiac muscles of the body. LGMD is classified into two main subtypes A and B, which are further subclassified into eight dominant and thirty recessive subtypes. Three genes, namely POPDC1, POPDC2 and POPDC3, encode popeye domain-containing protein (POPDC), and the variants of POPDC1 and POPDC3 genes have been associated with LGMD. In the present study, we performed whole-exome sequencing (WES) analysis on a single-family to investigate the hallmark features of LGMD. The results of WES were further confirmed by Sanger sequencing and 3D protein modeling was also conducted. WES data analysis and Sanger sequencing revealed a homozygous missense variant (c.460A>G; p.Lys154Glu) at a highly conserved amino acid position in the POPDC3. Mutations in the POPDC3 gene have been previously associated with recessive limb-girdle muscular dystrophy type 26. 3D protein modeling further suggested that the identified variant might affect the POPDC3 structure and proper function. The present study confirms the role of POPDC3 in LGMD, and will facilitate genetic counseling of the family to mitigate the risks of the carrier or affects on future pregnancies.

Axial muscle involvement in patients with limb girdle muscular dystrophy type R9

Limb girdle muscular dystrophy type R9 (LGMDR9) is characterized by progressive weakness of the shoulder and hip girdles. Involvement of proximal extremity muscles is well-described whereas information about axial muscle involvement is lacking. It is important to recognize the involvement of axial muscles to understand functional challenges for the patients. The aim of this study was to investigate the involvement of axial and leg muscles in patients with LGMDR9. This observational, cross-sectional study investigated fat replacement of axial and leg muscles in 14 patients with LGMDR9 and 13 matched, healthy controls using quantitative MRI (Dixon technique). We investigated paraspinal muscles at three levels, psoas major at the lumbar level, and leg muscles in the thigh and calf. Trunk strength was assessed with stationary dynamometry and manual muscle tests. Patients with LGMDR9 had significantly increased fat replacement of all investigated axial muscles compared with healthy controls (P < .05). Trunk extension and flexion strength were significantly reduced in patients. Extension strength correlated negatively with mean fat fraction of paraspinal muscles. Fat fractions of all investigated leg muscles were significantly increased versus controls, with the posterior thigh muscles being the most severely affected. Patients with LGMDR9 have severe involvement of their axial muscles and correspondingly have reduced trunk extension and flexion strength. Our findings define the axial muscles as some of the most severely involved muscle groups in LGMDR9, which should be considered in the clinical management of the disorder and monitoring of disease progression.

Prevalence of chronic pain in a national cohort of patients with limb-girdle muscular dystrophy: a cross-sectional study

Purpose The aim was to investigate the prevalence, characteristics, predictors, and consequences of chronic pain in a national cohort of patients with limb-girdle muscular dystrophy (LGMD). Materials and methods Questionnaires were sent to all Danish LGMD patients (≥18 years of age) registered with the National Rehabilitation Center for Neuromuscular Diseases. Results Of 209 patients, 121 responded. 44.7% of the patients experienced persistent (daily or constant) chronic pain lasting more than 3 months. 21.0% of patients experienced chronic pain that was not daily. Most pain patients experienced three or more pain problems, primarily in the lower back, neck, shoulders, hips, and legs. Symptoms suggestive of neuropathic pain were sometimes present. Patients with persistent chronic pain reported moderate pain interference with daily activities, greater psychological distress, and lower quality of life compared to patients without pain but did not differ regarding physical functioning. Sex, age, LGMD duration, LGMD type, mechanical ventilation use, mobility, arm function, or performance on activities of daily living did not predict chronic pain. Conclusion Chronic pain is common in patients with LGMD. Chronic pain should be considered an important component of LGMD and addressed in the clinic and rehabilitation setting from a biopsychosocial perspective. Implication for rehabilitation Chronic pain is highly prevalent in patients with limb-girdle muscular dystrophy. Health professionals need to systematically ask patients about pain and the influence of pain on everyday life irrespective of LGMD-duration and extent of muscle wastage. Chronic pain and psychological distress need to be addressed in the clinic and rehabilitation setting as an additional disabling component of LGMD and this should be done within a biopsychosocial framework.

Targeted Next-Generation Sequencing Reveals Mutations in Non-coding Regions and Potential Regulatory Sequences of Calpain-3 Gene in Polish Limb-Girdle Muscular Dystrophy Patients.

Limb–girdle muscular dystrophy type R1 (LGMDR1) is caused by mutations in CAPN3 and is the most common type of recessive LGMD. Even with the use of whole-exome sequencing (WES), only one mutant allele of CAPN3 is found in a significant number of LGMDR patients. This points to a role of non-coding, intronic or regulatory, sequence variants in the disease pathogenesis. Targeted sequencing of the whole CAPN3 gene including not only intronic, 3′ and 5′ UTRs but also potential regulatory regions was performed in 27 patients suspected with LGMDR1. This group included 13 patients with only one mutated CAPN3 allele detected previously with exome sequencing. A second rare variant in the non-coding part of CAPN3 was found in 11 of 13 patients with previously identified single mutation. Intronic mutations were found in 10 cases, with c.1746-20C>G variant present in seven patients. In addition, a large deletion of exons 2–8 was found in one patient. In the patients with no causative mutation previously found, we detected rare CAPN3 variants in 5 out of 10 patients and in two of them in a compound heterozygous state. Rare variants within putative regulatory sequences distant from the CAPN3 gene were found in 15 patients, although in 11 of these cases, other variants are deemed causative. The results indicate that intronic mutations are common in Polish LGMDR patients, and testing for non-coding mutations in CAPN3 should be performed in apparently single heterozygous patients.

Phenotype genotype characterization of FKRP mutations in an Indian cohort of limb girdle muscular dystrophy

Mutations in the FKRP (Fukutin Related Protein) gene produces variable phenotypes including Limb Girdle Muscular Dystrophy Type R9 (formerly LGMD2I). It has been rarely reported in South Asian population. We studied a cohort of Indian patients with LGMD2I to elucidate the mutation spectrum and possible genotype–phenotype correlation.

A new case of TRIM32/ASTN2 deletions confirm the association of LMGD with MCI

Defects in TRIM32 gene were reported in limb-girdle muscular dystrophy type 2H (LMGD2H). Homozygosis deletion of the entire TRIM32 gene and part of ASNT2 gene was previously described in only one patient presenting LMGD2H with a mild cognitive impairment (MCI). Interesting ASTN2 gene encodes a protein expressed in the brain and probably involved in neuronal migration. We provide an extensive phenotypic description of the second case of TRIM32/ASTN2 deletion.

Аutosomal recessive limb-girdle muscular dystrophy type 2A: two cases in Ukraine with different age of onset

The paper reports on two cases of young women from Ukraine with autosomal recessive limb-girdle muscular dystrophy type 2A with different age of symptoms onset and an absence of any family history presented with gradual onset of proximal muscle weakness in four limbs and thinning of shoulders, arms and thighs. Both patients had elevated creatine phosphokinase level and c.550delA mutations in CAPN3 gene. Sequence analysis and deletion/duplication testing of the 159 genes from skeletal muscles disease testing panel of 5-year-old girl identified deletion of exon 8 (heterozygous) and c.550delA (p.Thr184Argfs*36) mutation (heterozygous), were in CAPN3 gene. Magnetic Resonance Imaging of soft tissue of the proximal lower extremities was performed which showed signs of symmetrical atrophic changes in the major adductor muscle, the long and short adductor muscles, the semitendinosus muscle of the thigh, as a manifestations of autosomal recessive limb-girdle muscular dystrophy type 2A. Homozygous, pathogenic variant of the defect in the CAPN3 gene c.550del (p.Thr184Argfs * 36) was identified in a 25-year-old woman. Type 2A is the most common form of limb-girdle muscular dystrophy, accounting for about 30% of cases. The autosomal recessive limb-girdle muscular dystrophy type 2A is on caused by mutations in the CAPN3 gene, and it is characterized by selective atrophy and weakness of proximal limb and girdle muscles. The age of onset of muscle weakness is extremely variable; the most common being between 8 and 15 years, although it can range between 2 and 50 years. The diagnosis can be suspected by findings on a muscle biopsy or when a doctor experienced in muscular dystrophy examines you. A serum creatine kinase blood test may also show raised levels which indicate a problem in the muscles. The diagnosis has to be confirmed by means of identifying a mutation in the CAPN3 gene which is done on a deoxyribonucleic acid sample from a blood test. To date there are no specific treatments for limb-girdle muscular dystrophy, however careful management of the symptoms of the condition can improve a person’s quality of life. Joint contractures (tightening) can occur in limb-girdle muscular dystrophy and therefore regular physiotherapy is recommended.

Muscle-Related Plectinopathies.

Plectin is a giant cytoskeletal crosslinker and intermediate filament stabilizing protein. Mutations in the human plectin gene (PLEC) cause several rare diseases that are grouped under the term plectinopathies. The most common disorder is autosomal recessive disease epidermolysis bullosa simplex with muscular dystrophy (EBS-MD), which is characterized by skin blistering and progressive muscle weakness. Besides EBS-MD, PLEC mutations lead to EBS with nail dystrophy, EBS-MD with a myasthenic syndrome, EBS with pyloric atresia, limb-girdle muscular dystrophy type R17, or EBS-Ogna. In this review, we focus on the clinical and pathological manifestations caused by PLEC mutations on skeletal and cardiac muscle. Skeletal muscle biopsies from EBS-MD patients and plectin-deficient mice revealed severe dystrophic features with variation in fiber size, degenerative myofibrillar changes, mitochondrial alterations, and pathological desmin-positive protein aggregates. Ultrastructurally, PLEC mutations lead to a disorganization of myofibrils and sarcomeres, Z- and I-band alterations, autophagic vacuoles and cytoplasmic bodies, and misplaced and degenerating mitochondria. We also summarize a variety of genetically manipulated mouse and cell models, which are either plectin-deficient or that specifically lack a skeletal muscle-expressed plectin isoform. These models are powerful tools to study functional and molecular consequences of PLEC defects and their downstream effects on the skeletal muscle organization.

LGMD: EP.182 Quality of life in dysferlinopathy can be good despite poor function

Measuring quality of life (QoL) in chronic conditions is complex. However, it is important for guiding management and may be required for approval of new treatments. Here we evaluate the QoL-gNMD neuromuscular quality of life assessment tool in patients with dysferlinopathy. Methods: Twenty genetically confirmed patients with dysferlinopathy were evaluated by trained physiotherapists during the first year of the Jain clinical outcomes study in dysferlinopathy extension study. Assessments included the QoL-gNMD, the ACTIVLIM and the North Star assessment for limb girdle type muscular dystrophy (NSAD).