LAMA2-related Muscular Dystrophy Research Articles

Bone quality in LAMA2-related muscular dystrophy and SELENON-related congenital myopathy, a one-year prospective natural history study

Fragility fractures are frequently reported in neuromuscular diseases and negatively influence functional prognosis, quality of life and survival. In LAMA2-related muscular dystrophy (LAMA2-MD) and SELENON(SEPN1)-related congenital myopathy (SELENON-RM) cross-sectional and prospective natural history studies on bone quality and fragility long bone fractures (LBFs) are lacking. We therefore aim to systematically assess bone quality and provide recommendations for clinical care. We performed a one-year prospective natural history study in 21 LAMA2-MD and 10 SELENON-RM patients including a standardized fracture history and bone quality assessment through dual energy Xray absorptiometry scan (DEXA-scan) and/or bone health index (BHI). Ninety percent of the LAMA2-MD and SELENON-RM patients showed low bone quality. Eight (38%) LAMA2-MD and five (50%) SELENON-RM patients had a history of fragility LBFs. During the one-year follow-up period, one LAMA2-MD patient (female, 3 years) experienced a fragility LBF of the right humerus. We found no difference in bone mineral density between baseline and one-year follow-up. Based on general international guidelines for osteoporosis, we advise adequate vitamin D and calcium intake, and standardized clinical follow-up through a DEXA-scan or BHI in all LAMA2-MD and SELENON-RM patients. On indication, patients should be referred to the pediatrics or internal medicine for consideration of additional treatments.

Respiratory function in LAMA2-related muscular dystrophy and SELENON-related congenital myopathy, a 1.5-year natural history study

IntroductionLAMA2-related muscular dystrophy (LAMA2-MD) and SELENON(SEPN1)-related congenital myopathy (SELENON-RM) are rare neuromuscular diseases with respiratory impairment from a young age. Prospective natural history studies are needed for prevalence estimations, respiratory characterization, optimizing clinical care and selecting outcome measures for trial readiness. MethodsOur prospective 1.5-year natural history study included spirometry (forced vital capacity (FVC); difference between upright and supine vital capacity (dVC)), respiratory muscle strength tests (sniff nasal inspiratory pressure (SNIP)) (age≥5 years), and diaphragm ultrasound (thickness; thickening; echogenicity; all ages). ResultsTwenty-six LAMA2-MD patients (M = 8, median 21 [9; 31] years) and 11 SELENON-RM patients (M = 8, 20 [10; 33] years) were included. At baseline, 17 (85 %) LAMA2-MD (FVC%: 59 % [33; 68]) and all SELENON-RM patients (FVC%: 34 % [31; 46]) had an impaired respiratory function (FVC%<80 %). Nine (35 %) LAMA2-MD and eight (73 %) SELENON-RM patients received mechanical ventilation at baseline, and two additional SELENON-RM patients started during follow-up. Contrarily to LAMA2-MD, SELENON-RM patients had severe diaphragm atrophy (diaphragm thickness z-score: 2.5 [-3.1; −2.1]) and dysfunction (diaphragm thickness ratio: 1.2 [1.0; 1.7]; dVC: 30 % [7.7; 41]). SNIP was low in both neuromuscular diseases and correlated with motor function. In SELENON-RM, respiratory function decreased during follow-up. ConclusionThe majority of LAMA2-MD and all SELENON-RM patients had respiratory impairment. SELENON-RM patients showed lower respiratory function which was progressive, more prevalent mechanical ventilation, and more severe diaphragm atrophy and dysfunction than LAMA2-MD patients. Spirometry (FVC%, dVC) and respiratory muscle strength tests (SNIP) are useful in clinical care and as outcome measure in clinical trials. Clinical trial numberNCT04478981.

VP427 The Swiss cohort of LAMA2-related muscular dystrophy patients

VP427 The Swiss cohort of LAMA2-related muscular dystrophy patients

LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study.

LAMA2-related muscular dystrophy (LAMA2-MD) is a rare neuromuscular disease characterized by proximal and axial muscle weakness, rigidity of the spine, scoliosis, and respiratory impairment. No curative treatment options exist, yet promising preclinical studies are ongoing. Currently, there is a paucity on natural history data, and appropriate clinical and functional outcome measures are needed. We aim for deep clinical phenotyping, establishment of a well-characterized baseline cohort for prospective follow-up and recruitment for future clinical trials, improvement of clinical care, and selection of outcome measures for reaching trial readiness. We performed a cross-sectional, single-center, observational study. This study included neurologic examination and functional measurements among others the Motor Function Measure 20/32 (MFM-20/32) as primary outcome measure, accelerometry, questionnaires, muscle ultrasound, respiratory function tests, electrocardiography and echocardiography, and dual-energy X-ray absorptiometry. Twenty-seven patients with genetically confirmed LAMA2-MD were included (21 ± 13 years; M = 9; ambulant = 7). Axial and proximal muscle weakness was most pronounced. The mean MFM-20/32 score was 42.0% ± 29.4%, with domain 1 (standing and transfers) being severely affected and domain 3 (distal muscle function) relatively spared. Physical activity as measured through accelerometry showed very strong correlations to MFM-20/32 (Pearson correlation, -0.928, p < 0.01). Muscle ultrasound showed symmetrically increased echogenicity, with the sternocleidomastoid muscle most affected. Respiratory function was impaired in 85% of patients without prominent diaphragm dysfunction and was independent of age. Ten patients (37%) needed (non)invasive ventilatory support. Cardiac assessment revealed QRS fragmentation in 62%, abnormal left ventricular global longitudinal strain in 25%, and decreased left ventricular ejection fraction in 14% of patients. Decreased bone quality leading to fragility fractures was seen in most of the patients. LAMA2-MD has a widely variable phenotype. Based on the results of this cross-sectional study and current standards of care for congenital muscular dystrophies, we advise routine cardiorespiratory follow-up and optimization of bone quality. We propose MFM-20/32, accelerometry, and muscle ultrasound for assessing disease severity and progression. For definitive clinical recommendations and outcome measures, natural history data are needed. This study was registered at clinicaltrials.gov (NCT04478981, 21 July 2020). The first patient was enrolled in September 2020.

Vemurafenib improves muscle histopathology in a mouse model of LAMA2-related congenital muscular dystrophy.

Laminin-α2-related congenital muscular dystrophy (LAMA2-CMD) is a neuromuscular disease affecting around 1-9 in 1,000,000 children. LAMA2-CMD is caused by mutations in the LAMA2 gene resulting in the loss of laminin-211/221 heterotrimers in skeletal muscle. LAMA2-CMD patients exhibit severe hypotonia and progressive muscle weakness. Currently, there is no effective treatment for LAMA2-CMD and patients die prematurely. The loss of laminin-α2 results in muscle degeneration, defective muscle repair and dysregulation of multiple signaling pathways. Signaling pathways that regulate muscle metabolism, survival and fibrosis have been shown to be dysregulated in LAMA2-CMD. As vemurafenib is a US Food and Drug Administration (FDA)-approved serine/threonine kinase inhibitor, we investigated whether vemurafenib could restore some of the serine/threonine kinase-related signaling pathways and prevent disease progression in the dyW-/- mouse model of LAMA2-CMD. Our results show that vemurafenib reduced muscle fibrosis, increased myofiber size and reduced the percentage of fibers with centrally located nuclei in dyW-/- mouse hindlimbs. These studies show that treatment with vemurafenib restored the TGF-β/SMAD3 and mTORC1/p70S6K signaling pathways in skeletal muscle. Together, our results indicate that vemurafenib partially improves histopathology but does not improve muscle function in a mouse model of LAMA2-CMD.

First person – Ariany Oliveira-Santos

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Disease Models &amp; Mechanisms, helping researchers promote themselves alongside their papers. Ariany Oliveira-Santos is first author on ‘Vemurafenib improves muscle histopathology in a mouse model of LAMA2-related congenital muscular dystrophy’, published in DMM. Ariany is a postdoctoral researcher in the lab of Dean Burkin at the University of Nevada, Reno, NV, USA, investigating muscle biology and the development of new therapeutics for muscle diseases, particularly muscular dystrophies.

Nerve pathology is prevented by linker proteins in mouse models for LAMA2-related muscular dystrophy.

LAMA2-related muscular dystrophy (LAMA2 MD or MDC1A) is a devastating congenital muscular dystrophy that is caused by mutations in the LAMA2 gene encoding laminin-α2, the long chain of several heterotrimeric laminins. Laminins are essential components of the extracellular matrix that interface with underlying cells. The pathology of LAMA2 MD patients is dominated by an early-onset, severe muscular dystrophy that ultimately leads to death by respiratory insufficiency. However, pathology in nonmuscle tissues has been described. Prior work in the dyW /dyW mouse model for LAMA2 MD has shown that two linker proteins, mini-agrin and αLNNd, when expressed in skeletal muscle fibers, greatly increase survival from a few months up to more than 2 years. However, the restoration of skeletal muscle function accentuates the pathology in nonmuscle tissue in dyW /dyW mice, first and foremost in the peripheral nerve resulting in paralysis of the hind limbs. We now show that the expression of the two linker proteins in all tissues ameliorates the muscular dystrophy and prevents the appearance of the hind limb paralysis. Importantly, the same ameliorating effect of the linker proteins was seen in dy3K /dy3K mice, which represent the most severe mouse model of LAMA2 MD. In summary, these data show that the two linker proteins can compensate the loss of laminin-α2 in muscle and peripheral nerve, which are the two organs most affected in LAMA2 MD. These results are of key importance for designing appropriate expression constructs for mini-agrin and αLNNd to develop a gene therapy for LAMA2 MD patients.

LAMA2-Related Muscular Dystrophy: The Importance of Accurate Phenotyping and Brain Imaging in the Diagnosis of LGMD.

We report three siblings from a non-consanguineous family presenting with contractural limb-girdle phenotype with intrafamilial variability. Muscle MRI showed posterior thigh and quadriceps involvement with a sandwich-like sign. Whole-exome sequencing identified two compound heterozygous missense TTN variants and one heterozygous LAMA2 variant. Brain MRI performed because of concentration difficulties in one of the siblings evidenced white-matter abnormalities, subsequently found in the others. The genetic analysis was re-oriented, revealing a novel pathogenic intronic LAMA2 variant which confirmed the LAMA2-RD diagnosis. This work highlights the importance of a thorough clinical phenotyping and the importance of brain imaging, in order to orientate and interpret the genetic analysis.

Establishment of a PBMC-derived induced pluripotent stem cell (NJUCMi001-A) from a patient with LAMA2-related congenital muscular dystrophy (MDC1A) carrying frameshift deletion c.3367delA in LAMA2 gene

LAMA2-related congenital muscular dystrophy (MDC1A), the most commonly recognized type of congenital muscular dystrophies, is a severe neonatal onset muscle disease caused by recessive mutations in the LAMA2 gene. Here, we established an induced pluripotent stem cell line from a MDC1A patient carrying a frameshift deletion c.3367delA in LAMA2 gene. The iPSC line expressed pluripotency markers, retained normal karyotype, showed capability of differentiating into three germ layers. The iPSC line will help to further elucidate the pathogenic mechanisms of LAMA2 mutation, and benefit treatment for congenital muscular dystrophies in the future.

P.185 Evaluation of brain microstructure in LAMA2 related muscular dystrophy by NODDI; A pilot study

P.185 Evaluation of brain microstructure in LAMA2 related muscular dystrophy by NODDI; A pilot study

FP.40 A cross-sectional study on LAMA2-related muscular dystrophy and SELENON-related myopathy, the first results of the LAST STRONG Study

FP.40 A cross-sectional study on LAMA2-related muscular dystrophy and SELENON-related myopathy, the first results of the LAST STRONG Study

VP.76 Natural history of a novel mouse model for LAMA2-related congenital muscular dystrophy

VP.76 Natural history of a novel mouse model for LAMA2-related congenital muscular dystrophy

VP.77 Muscle transcriptomic study of a novel LAMA2-related congenital muscular dystrophy mouse model

VP.77 Muscle transcriptomic study of a novel LAMA2-related congenital muscular dystrophy mouse model

FP.38 Linker protein-mediated gene therapy ameliorates muscle and nerve pathology in mouse models for LAMA2-related congenital muscular dystrophy

<i>LAMA2</i>-related muscular dystrophy (LAMA2 MD or MDC1A) is the most frequent form of congenital muscular dystrophies. It is caused by mutations in <i>LAMA2</i>, the gene encoding laminin-α2, one chain of the heterotrimeric extracellular matrix protein laminin-211 (α2β1γ1). The large size of the cDNA encoding laminin-α2 and the heterotrimeric structure of laminin-211 present a challenge for gene replacement or gene editing strategies. Here, we describe the development of an AAV-based gene therapy to functionally replace laminin-211 by two small linker proteins. The two linker proteins, mini-agrin (mag) and αLNNd, are assembled from selected domains of agrin, nidogen-1 and laminin-α1. Previous work from our lab in transgenic mice has demonstrated that this Simultaneous Expression of Artificial Linkers (SEAL) in skeletal muscle of LAMA2 MD mice has a tremendous ameliorative effect on muscle pathology and survival. However, muscle-specific treatment makes the peripheral neuropathy phenotype in aged LAMA2 MD mice very apparent, as they develop a severe hindlimb paralysis. Here, we show in novel transgenic models that ubiquitous expression of linker proteins additionally overcomes this LAMA2-related peripheral neuropathy. We also show that the linker proteins are efficiently expressed upon systemic delivery by AAV9. Expression by a muscle-specific promoter significantly ameliorates the muscle disease phenotype in LAMA2 MD mice, as shown on the level of body- and muscle mass, fiber size, inflammation and muscle function (grip strength and locomotion). These experiments show that AAV-mediated expression of the two linker proteins is possible and they suggest that this functional replacement strategy by the design of small proteins assembled from protein domains present in patients may overcome some of the current challenges of gene therapy trials. Additionally, the linker proteins are secreted and are deposited in the extracellular matrix, which allows their accumulation upon expression by AAV. In summary, this study serves as a proof-of-concept in mice and establishes systemic delivery of AAVs that express the two linkers (SEAL technology) as a promising gene therapy for treating LAMA2 MD. Our current efforts focus on the use of next-generation AAVs with increased tropisms to skeletal muscle but low infection of liver (AAVMYO) and the use of ubiquitous promoters to evaluate the possibility of ameliorating the peripheral neuropathy.

VP.78 Clinical and genetic study of LAMA2-related muscular dystrophy patients with seizures

<i>LAMA2</i>-related muscular dystrophy (LAMA2-MD) is an autosomal recessive muscular dystrophy caused by pathogenic variants in <i>LAMA2</i> gene, including two subgroups: severe, early-onset <i>LAMA2</i>-related congenital muscular dystrophy (LAMA2-CMD) and mild, late-onset autosomal recessive limb-girdle muscular dystrophy-23 (LGMD R23). Seizures frequently occurred in LAMA2-MD, however, the relationship between seizures and genotype in LAMA2-MD is not fully known. The clinical information of seizures including seizure type, frequency, treament, EEG changes, brain MRI and genetic data of LAMA2-MD patients from Peking University First Hospital between January 2003 and March 2022 were collected and analyzed. Among 141 LAMA2-MD patients, seizures were observed in 10.5% (13/124) of LAMA2-CMD patients and 29.4% (5/17) of LGMD R23 patients, including 14 patients with epilepsy and 4 patients with febrile seizures. The median (range) age of first seizure episode was 5 (0.1-20) years in LAMA2-CMD and 14 (1-24) years in LGMD R23. Eight patients with epilepsy showed focal seizures. Abnormal results of electroencephalography were found in 8/10 patients, manifesting as temporal, occipital or temporo-occipital epileptiform abnormalities. Brain magnetic resonance imaging (MRI) was performed in 16 patients with seizures, showing occipital pachygyria in 4 patients, cerebellum and brain stem dysplasia in 2 patients. Brain MRI of 41 LAMA2-MD patients without seizures were reassessed, showing occipital lobe pachygyria in 6 patients. Therefore, there was no significant association between seizures and occipital pachygyria in our cohort (P=0.18). Nine patients received antiepileptic drugs, while patients with occipital lobe pachygyria showed poor seizure control. The pathogenic variants included splice mutation (n=8), nonsense mutation (n=6) and frameshift mutation(n=6) in LAMA2-CMD patients, while missense mutation (n=5), frameshift mutation(n=4) in LGMD R23 patients. Compared with LAMA2-CMD, seizures were more frequently occurred in LGMD R23 patients and mainly manifested as focal seizures. No correlation between genotype and seizures was observed. In this study, we found that seizures occurred in 10.5% of LAMA2-CMD and 29.4% of LGMD R23 patients, and described the features of seizures in LAMA2-MD patients.

Whole exome sequencing identified a novel LAMA2 frameshift variant causing merosin-deficient congenital muscular dystrophy in a patient with cardiomyopathy, and autism-like behavior

Muscular dystrophy (MD) is a group of multiple muscle diseases, which causes severely impaired motor ability, degeneration and dysfunctions in the musculoskeletal system, respiratory failure and feeding difficulties. LAMA2-related MD is caused by pathogenic variants in the LAMA2 gene, encoding laminin a2 chain, a component of the skeletal muscle extracellular matrix protein laminin-α2β1γ1. We performed clinical examination and molecular genetic analysis in a patient with congenital MD (CMD), and autism-like phenotype. We performed whole exome sequencing (WES) to find possible genetic etiology of CMD in an Iranian non-consanguineous patient. The pathogenicity of the variants was assessed using various Bioinformatics tools. American College of Medical Genetics and Genomics (ACMG) guidelines were used to interpret the variant and Sanger sequencing in the patient and her family was applied for the confirmation of the variant. WES results showed a novel frameshift homozygous variant (p.Tyr1313LeufsTer4) in the LAMA2 gene leading to the CMD phenotype. This variant resides in a highly conserved region and was found to be co-segregating in the family. It fulfils the criteria of being pathogenic. We successfully identified a novel LAMA2 pathogenic variant in an Iranian patient suffering from CMD and autism using WES. Identification of disease-causing variant in autosomal recessive disorders such as CMD can be useful in genetic counseling, prenatal diagnosis, and predicting prognosis of the disease.

Adapting an off-the-shelf Mobility Device for Early Intervention: A Case Study

ABSTRACT Movement and mobility are a significant aspect of early childhood. Assistive technology and adapted mobility can be a critical aspect of the early intervention process by promoting access to play, the environment, social opportunities, and development of visual perceptual and navigational skills. This case study describes the design, materials, and build of an inexpensive mobility device for use with a three-year-old child with LAMA2-related muscular dystrophy. This is based on an off-the-shelf toy car with independent motors which provides the child with high maneuverability in indoor environments. The adaptations made provided the child with the postural support necessary for promoting safe use of the device while increasing access to mobility, her environment, and social opportunities.

Diagnostic interest of whole-body MRI in early- and late-onset LAMA2 muscular dystrophies: a large international cohort

LAMA2-related muscular dystrophy (LAMA2-RD) encompasses a group of recessive muscular dystrophies caused by mutations in the LAMA2 gene, which codes for the alpha-2 chain of laminin-211 (merosin). Diagnosis is straightforward in the classic congenital presentation with no ambulation and complete merosin deficiency in muscle biopsy, but is far more difficult in milder ambulant individuals with partial merosin deficiency. To investigate the diagnostic utility of muscle imaging in LAMA2-RD using whole-body magnetic resonance imaging (WBMRI). 27 patients (2-62years, 21-80% with acquisition of walking ability and 6 never ambulant) were included in an international collaborative study. All carried two pathogenic mutations, mostly private missense changes. An intronic variant (c.909 + 7A > G) was identified in all the Chilean cases. Three patients (two ambulant) showed intellectual disability, epilepsy, and brain structural abnormalities. WBMRI T1w sequences or T2 fat-saturated images (Dixon) revealed abnormal muscle fat replacement predominantly in subscapularis, lumbar paraspinals, gluteus minimus and medius, posterior thigh (adductor magnus, biceps femoris, hamstrings) and soleus. This involvement pattern was consistent for both ambulant and non-ambulant patients. The degree of replacement was predominantly correlated to the disease duration, rather than to the onset or the clinical severity. A "COL6-like sandwich sign" was observed in several muscles in ambulant adults, but different involvement of subscapularis, gluteus minimus, and medius changes allowed distinguishing LAMA2-RD from collagenopathies. The thigh muscles seem to be the best ones to assess disease progression. WBMRI in LAMA2-RD shows a homogeneous pattern of brain and muscle imaging, representing a supportive diagnostic tool.

Muscle magnetic resonance imaging in patients with LAMA2-related muscular dystrophy

LAMA2-related muscular dystrophy (LAMA2-MD) is classified into congenital muscular dystrophy type 1A (MDC1A) and autosomal recessive limb-girdle muscular dystrophy-23 (LGMDR23). The purpose of this study was to identify the involvement pattern of thigh muscles of LAMA2-MD patients on magnetic resonance imaging. Fourteen MDC1A and 3 LGMDR23 patients were included, with 21 known and 8 novel LAMA2 disease-causing variants. In LAMA2-MD, the gluteus maximus, anterior (quadriceps femoris) and posterior (adductor magnus and biceps femoris) thigh muscles were extensively and severely affected with fatty infiltration, with relatively sparing of the adductor longus. The pattern of muscle involvement was similar between MDC1A and LGMDR23, but more severe in MDC1A, as well as in LAMA2-MD patients without ambulation. The rather peculiar pattern of the adductor magnus and long head of the biceps femoris first and severely affected in the mid-thigh level was found in LGMDR23. Strong correlation between fatty infiltration and age as well as disease duration was observed for the adductor longus in MDC1A. Edema and atrophy selectively involved in some muscles. The pattern of fatty infiltration on thigh muscle MRI of LAMA2-MD could provide important information for the diagnosis, differential diagnosis and assessment of clinical severity.

CONGENITAL MUSCULAR DYSTROPHIES: EP.68 Therapeutic effect of linker protein-mediated gene therapy in a mouse model for LAMA2-related muscular dystrophy

CONGENITAL MUSCULAR DYSTROPHIES: EP.68 Therapeutic effect of linker protein-mediated gene therapy in a mouse model for LAMA2-related muscular dystrophy