Collagen VI-related Muscular Dystrophy Research Articles

Pregnancy in a woman with extreme short stature and low body weight secondary to a collagen VI-related muscular dystrophy

Pregnancy poses significant physiological demands, and women of extreme short stature may be particularly at risk of complications. Described here are two pregnancies in a woman who was 130 cm tall with a body mass index of 12 kg/m2 and the maternal and neonatal outcomes. The challenges encountered in the care of our patient included cardiorespiratory compromise, management of medication dosing, management of delivery and bleeding risk.

P425 Inhibition of TGFβ signaling pathway as a therapeutic approach in collagen VI-related muscular dystrophy

P425 Inhibition of TGFβ signaling pathway as a therapeutic approach in collagen VI-related muscular dystrophy

The Capillary Morphogenesis Gene 2 Triggers the Intracellular Hallmarks of Collagen VI-Related Muscular Dystrophy.

Collagen VI-related disorders (COL6-RD) represent a severe form of congenital disease for which there is no treatment. Dominant-negative pathogenic variants in the genes encoding α chains of collagen VI are the main cause of COL6-RD. Here we report that patient-derived fibroblasts carrying a common single nucleotide variant mutation are unable to build the extracellular collagen VI network. This correlates with the intracellular accumulation of endosomes and lysosomes triggered by the increased phosphorylation of the collagen VI receptor CMG2. Notably, using a CRISPR-Cas9 gene-editing tool to silence the dominant-negative mutation in patients’ cells, we rescued the normal extracellular collagen VI network, CMG2 phosphorylation levels, and the accumulation of endosomes and lysosomes. Our findings reveal an unanticipated role of CMG2 in regulating endosomal and lysosomal homeostasis and suggest that mutated collagen VI dysregulates the intracellular environment in fibroblasts in collagen VI-related muscular dystrophy.

Transcriptome analysis of collagen VI-related muscular dystrophy muscle biopsies.

ObjectiveTo define the transcriptomic changes responsible for the histologic alterations in skeletal muscle and their progression in collagen VI‐related muscular dystrophy (COL6‐RD).MethodsCOL6‐RD patient muscle biopsies were stratified into three groups based on the overall level of pathologic severity considering degrees of fibrosis, muscle fiber atrophy, and fatty replacement of muscle tissue. Using microarray and RNA‐Seq, we then performed global gene expression profiling on the same muscle biopsies and compared their transcriptome with age‐ and sex‐matched controls.ResultsCOL6‐RD muscle biopsy transcriptomes as a group revealed prominent upregulation of muscle extracellular matrix component genes and the downregulation of skeletal muscle and mitochondrion‐specific genes. Upregulation of the TGFβ pathway was the most conspicuous change across all biopsies and was fully evident even in the mildest/earliest histological group. There was no difference in the overall transcriptional signature between the different histologic groups but polyserial analysis identified relative changes along with COL6‐RD histological severity.InterpretationOverall, our study establishes the prominent dysregulation of extracellular matrix genes, TGFβ signaling, and its downstream cellular pathways at the transcriptomic level in COL6‐RD muscle.

Pathogenic variants in COL6A3 cause Ullrich-like congenital muscular dystrophy in young Labrador Retriever dogs

The collagen VI-related muscular dystrophies in people include a broad spectrum of diseases ranging from the severe Ullrich congenital muscular dystrophy to the mild Bethlem myopathy. Clinical features are attributable to both muscle and connective tissue and include progressive muscle weakness and respiratory failure, hyperlaxity of distal joints, and progressive contracture of large joints. Here we describe two different COL6A3 pathogenic variants in Labrador Retriever dogs that result in autosomal recessive or autosomal dominant congenital myopathies with hyperlaxity of distal joints and joint contracture, similar to the condition in people.

EP.122Recurrent pneumothorax in an adult case of Ullrich congenital muscular dystrophy – case report and review of literature

Collagen VI related muscular dystrophy is caused by dominant or recessive mutations in the COL6A1, COL6A2 or COL6A3 genes and comprises of a spectrum of rare neuromuscular disorders including the early-onset and more severe Ulrich congenital muscular dystrophy, the milder adult form of Bethlem myopathy and an intermediate phenotype. They are characterised clinically by progressive muscle weakness, distal hyperlaxity, joint contractures and respiratory insufficiency. Respiratory failure develops with progression of the condition and is caused by respiratory muscle (diaphragm and intercostal) weakness as well as spinal and thoracic deformities. Intrinsic lung disease is not common, but pneumothorax, occurring as a single event or as recurrent episodes is being increasingly recognised in these patients. Our patient is a 22 year old female with Ulrich congenital muscular dystrophy caused by heterozygous mutation in exon 9 of COL6A1 gene. She was known to have a restrictive lung defect with scoliosis since childhood. Nocturnal ventilatory support was initiated at the age of 18 following a sleep study showing evidence of hypoventilation. She developed a spontaneous left sided pneumothorax at 21 years old, requiring intercostal drain (ICD) insertion followed by chemical pleurodesis via ICD. A contralateral spontaneous pneumothorax occurred 8 months later, which was complicated by PEA arrest requiring intubation and ventilation; followed by a protracted recovery period. This case is being presented to increase the awareness of a potentially life threatening complication associated with this condition. A first presentation of spontaneous pneumothorax in these patients should lead to careful assessment of lung parenchymal changes and consideration of definitive pre-emptive contralateral intervention.

P.385Automated diagnosis of collagen VI related muscular dystrophies using advanced image analysis and machine learning

P.385Automated diagnosis of collagen VI related muscular dystrophies using advanced image analysis and machine learning

O.35Disruption of bioavailability of TGFβ in collagen VI-related muscular dystrophy

O.35Disruption of bioavailability of TGFβ in collagen VI-related muscular dystrophy

O.10A novel target for splice-modulating therapies: a common pseudoexon-inducing mutation that causes a severe collagen VI-related muscular dystrophy

O.10A novel target for splice-modulating therapies: a common pseudoexon-inducing mutation that causes a severe collagen VI-related muscular dystrophy

A Convolutional Neural Network for the automatic diagnosis of collagen VI-related muscular dystrophies

The development of machine learning systems for the diagnosis of rare diseases is challenging, mainly due to the lack of data to study them. This paper surmounts this obstacle and presents the first Computer-Aided Diagnosis (CAD) system for low-prevalence collagen VI-related congenital muscular dystrophies. The proposed CAD system works on images of fibroblast cultures obtained with a confocal microscope and relies on a Convolutional Neural Network (CNN) to classify patches of such images in two classes: samples from healthy persons and samples from persons affected by a collagen VI-related muscular distrophy. This fine-grained classification is then used to generate an overall diagnosis on the query image using a majority voting scheme. The proposed system is advantageous, as it overcomes the lack of training data, points to the possibly problematic areas in the query images, and provides a global quantitative evaluation of the condition of the patients, which is fundamental to monitor the effectiveness of potential therapies. The system achieves a high classification performance, with 95% of accuracy and 92% of precision on randomly selected independent test images, outperforming alternative approaches by a significant margin.

A novel COL6A2 mutation causing late-onset limb-girdle muscular dystrophy

Limb-girdle muscular dystrophies (LGMD) are genetic disorders characterized by weakness of predominantly proximal limb and trunk muscles due to progressive loss of muscle tissue. Collagen VI-related muscular dystrophies usually display more generalized muscle involvement combined with contractures and/or hyperlaxity of distal finger joints. LGMD-like phenotype of collagenopathy has only rarely been described and as reported is usually of childhood onset. We identified a Finnish family with COL6A2-related LGMD with autosomal dominant inheritance and very late onset at 40–60 years of age. Since the mutation was previously unreported, the pathognomonic findings on muscle MRI were the decisive clue for the correct diagnosis.

Transcriptome profiling identifies regulators of pathogenesis in collagen VI related muscular dystrophy.

ObjectivesThe collagen VI related muscular dystrophies (COL6-RD), Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM) are among the most common congenital muscular dystrophies and are characterized by distal joint laxity and a combination of distal and proximal joint contractures. Inheritance can be dominant negative (DN) or recessive depending on the type and location of the mutation. DN mutations allow incorporation of abnormal chains into secreted tetramers and are the most commonly identified mutation type in COL6-RD. Null alleles (nonsense, frameshift, and large deletions) do not allow incorporation of abnormal chains and act recessively. To better define the pathways disrupted by mutations in collagen VI, we have used a transcriptional profiling approach with RNA-Seq to identify differentially expressed genes in COL6-RD individuals from controls.MethodsRNA-Seq allows precise detection of all expressed transcripts in a sample and provides a tool for quantification of expression data on a genomic scale. We have used RNA-Seq to identify differentially expressed genes in cultured dermal fibroblasts from 13 COL6-RD individuals (8 dominant negative and 5 null) and 6 controls. To better assess the transcriptional changes induced by abnormal collagen VI in the extracellular matrix (ECM); we compared transcriptional profiles from subjects with DN mutations and subjects with null mutations to transcriptional profiles from controls.ResultsDifferentially expressed transcripts between COL6-RD and control fibroblasts include upregulation of ECM components and downregulation of factors controlling matrix remodeling and repair. DN and null samples are differentiated by downregulation of genes involved with DNA replication and repair in null samples.ConclusionsDifferentially expressed genes identified here may help identify new targets for development of therapies and biomarkers to assess the efficacy of treatments.

Upper extremity outcome measures for collagen VI-related myopathy and LAMA2-related muscular dystrophy

Congenital muscular dystrophy (CMD) comprises a rare group of genetic muscle diseases that present at birth or early during infancy. Two common subtypes of CMD are collagen VI-related muscular dystrophy (COL6-RD) and laminin alpha 2-related dystrophy (LAMA2-RD). Traditional outcome measures in CMD include gross motor and mobility assessments, yet significant motor declines underscore the need for valid upper extremity motor assessments as a clinical endpoint. This study validated a battery of upper extremity measures in these two CMD subtypes for future clinical trials.For this cross-sectional study, 42 participants were assessed over the same 2–5 day period at the National Institutes of Health Clinical Center. All upper extremity measures were correlated with the Motor Function Measure 32 (MFM32). The battery of upper extremity assessments included the Jebsen Taylor Hand Function Test, Quality of Upper Extremity Skills Test (QUEST), hand held dynamometry, goniometry, and MyoSet Tools. Spearman Rho was used for correlations to the MFM32. Pearson was performed to correlate the Jebsen, QUEST, hand-held dynamometry, goniometry and the MyoSet Tools. Correlations were considered significant at the 0.01 level (2-tailed).Significant correlations were found between both the MFM32 and MFM Dimension 3 only (Distal Motor function) and the Jebsen, QUEST, MyoGrip and MyoPinch, elbow flexion/extension ROM and myometry. Additional correlations between the assessments are reported.The Jebsen, the Grasp and Dissociated Movements domains of the QUEST, the MyoGrip and the MyoPinch tools, as well as elbow ROM and myometry were determined to be valid and feasible in this population, provided variation in test items, and assessed a range of difficulty in CMD. To move forward, it will be of utmost importance to determine whether these upper extremity measures are reproducible and sensitive to change over time.

P.342 - Transcriptome profiling identifies key pathways important in collagen VI related muscular dystrophies including differences between patients with dominant negative vs. null mutations

P.342 - Transcriptome profiling identifies key pathways important in collagen VI related muscular dystrophies including differences between patients with dominant negative vs. null mutations

150. Further Development of an Allele-Specific Gene Silencing Strategy to Correct a Dominant-Negative Mutation Causing Collagen VI-Related Muscular Dystrophy

Collagen VI-related congenital muscular dystrophies (COL6-RD), caused by mutations in any of the three genes coding for collagen type VI (COL6A1, COL6A2, COL6A3), underlie a spectrum of disorders ranging from severe life-threatening early onset Ullrich muscular dystrophy via intermediate phenotypes to the milder Bethlem type, typically presenting with generalized muscle weakness, proximal joint contractures, and respiratory failure. At present, there are no treatment options available for individuals affected with these diseases. The fact that the majority of COL6-RD cases are carriers of inherited or de novo dominant mutations, acting as dominant-negative, poses a challenge for the development of targeted therapies. In contrast to gene replacement, allele-specific silencing has the potential to treat these disorders, as it would convert the dominant-negative state into a clinically asymptomatic haploinsufficient state. Therefore, in the laboratory we aim at exploring targeted RNA interference (RNAi) approaches as a potential therapeutic approach for dominant COL6-RD. We have previously demonstrated the allele-specificity and efficacy of siRNA oligos to downregulate the expression of a mutant COL6A3 transcript in vitro in patient-derived fibroblasts. In preparation of in vivo testing we have now extended our study to cells isolated from a mouse model of the disorder, which carries the most frequent dominant-negative mutation, a deletion of exon 16 on Col6a3. We transfected a series of small interfering RNA (siRNA) oligonucleotides into Col6a3del16+/- fibroblast cells, isolated from skin and muscle. To assay efficacy we used outcome measures such as unsaturated PCR, quantitative RT-PCR, and immunofluorescence. In addition, we performed in vivo electroporation of siRNA oligonucleotides in FDB muscles of Col6a3del16+/- mice. We found that siRNA oligonucleotides were effective in Col6a3del16+/- cells, to specifically knockdown the expression from the mutant allele and to restore the production of a collagen VI matrix in culture. This study provides further proof-of-concept of the use of RNAi as a potential treatment for COL6-RD.

Results of a two-year pilot study of clinical outcome measures in collagen VI- and laminin alpha2-related congenital muscular dystrophies

Potential therapies are currently under development for two congenital muscular dystrophy (CMD) subtypes: collagen VI-related muscular dystrophy (COL6-RD) and laminin alpha 2-related dystrophy (LAMA2-RD). However, appropriate clinical outcome measures to be used in clinical trials have not been validated in CMDs. We conducted a two-year pilot study to evaluate feasibility, reliability, and validity of various outcome measures, particularly the Motor Function Measure 32, in 33 subjects with COL6-RD and LAMA2-RD. In the first year, outcome measures tested included: Motor Function Measure 32 (MFM32), forced vital capacity (FVC) percent predicted sitting, myometry, goniometry, 10-meter walk, Egen Klassification 2, and PedsQLTM Generic and Neuromuscular Cores. In the second year, we added the North Star Ambulatory Assessment (NSAA), Hammersmith Functional Motor Scale (HFMS), timed functional tests, Measure of Activity Limitations (ACTIVLIM), Quality of Upper Extremity Skills Test (QUEST), and Patient-Reported Outcomes Measurement Information System (PROMIS) fatigue subscale. The MFM32 showed strong inter-rater (0.92) and internal consistency (0.96) reliabilities. Concurrent validity for the MFM32 was supported by large correlations (range 0.623–0.936) with the following: FVC, NSAA, HFMS, timed functional tests, ACTIVLIM, and QUEST. Significant correlations of the MFM32 were also found with select myometry measurements, mainly of the proximal extremities and domains of the PedsQLTM scales focusing on physical health and neuromuscular disease. Goniometry measurements were less reliable. The Motor Function Measure is reliable and valid in the two specific subtypes of CMD evaluated, COL6-RD and LAMA2-RD. The NSAA is useful as a complementary outcome measure in ambulatory individuals. Preliminary concurrent validity of several other clinical outcome measures was also demonstrated for these subtypes.

G.P.213: Investigating the molecular mechanisms underlying the progression of collagen VI-related muscular dystrophies

Ullrich congenital muscular dystrophy (UCMD) presents at birth or in infancy with progressive muscle weakness, joint contractures and respiratory failure, and is caused by mutations in the three genes coding for collagen VI. Dysfunction of the collagen VI microfibrills in the extracellular matrix perturbs the normal extracellular matrix/muscle interface, leading to yet incompletely characterized downstream effects. Review of muscle biopsies from UCMD patients show that the histological appearance changes with disease progression, suggesting changing disease-driving pathways throughout the progression of the disease. In preparation for a molecular investigation of such pathways, we analyzed 39 UCMD patient muscle biopsies with an automated image analysis algorithm using the degree of atrophy, fibrosis, and regeneration as criteria to group the biopsies. We performed microarray-based expression profiling on the grouped patient biopsies and age-matched controls. Expression profiling results correlated with staging obtained from the automated image analysis algorithm. Further studies will establish the involvement of specific molecules in different stages of UCMD to identify suitable targets for therapeutic intervention. (NIH).

T.O.1 Cyclosporin A as a potential treatment for collagen VI-related muscular dystrophy: A cellular study of mitochondrial dysfunction and its rescue

Mutations in COL6A1, COL6A2 and COL6A3, the genes which encode the extracellular matrix component collagen VI, lead to Bethlem myopathy (BM) and Ullrich Congenital Muscular Dystrophy (UCMD). Although the Col6A1 null mouse has an extremely mild neuromuscular phenotype, a mitochondrial defect has been demonstrated in this model which was linked to dysregulation of the mitochondrial permeability transition pore (PTP) opening. The same dysregulation has since been demonstrated in UCMD muscle cells in culture, provoking a move towards clinical trials using cyclosporine A, an inhibitor of PTP opening.

0262 New insights into the genetic diagnosis of collagen VI-related muscular dystrophies

0262 New insights into the genetic diagnosis of collagen VI-related muscular dystrophies