Congenital Muscular Dystrophy Patients Research Articles

Evaluation of clinico-pathological and genetic spectrum of Ullrich congenital muscular dystrophy patients from Indian cohort

Evaluation of clinico-pathological and genetic spectrum of Ullrich congenital muscular dystrophy patients from Indian cohort

Motor Outcome Measures in Pediatric Patients with Congenital Muscular Dystrophies: A Scoping Review

Congenital muscular dystrophies (CMDs) are a heterogeneous group of genetic neuromuscular disorders. They usually occur at birth or in early childhood, with delayed acquisition of motor milestones, and diffuse muscle weakness. A dystrophic pattern is evident on the muscle biopsy. They are highly variable both in terms of severity and clinical evolution and in terms of pathogenetic biochemical mechanisms. The aim of this review is to collect and summarize the current knowledge of motor function in pediatric patients with congenital muscular dystrophies and the instruments used to assess it. This scoping review was conducted using the methodology of PRISMA (extension for Scoping Reviews, PRISMA-ScR). Two databases were queried from January 2002 to November 2022. Articles were identified based on title and abstract. Full-text papers published in peer-reviewed English-language journals were selected. It emerged that motor functional aspects are still underinvestigated in CMD patients, probably due to the rarity of these conditions and the phenotypic variability. The scales used to assess motor function are heterogeneous, as are the age groups considered. Finally, the predominant type of research design is cross-sectional; few studies analyze the progression of motor function over time. All these factors make it difficult to correlate the results of different publications and stress the need for more accurate and shared protocols for assessing motor function in these patients.

EP394: Investigation and functional characterization of genomic signatures in congenital muscular dystrophy and congenital myopathy patients from India

Congenital muscular dystrophies (CMDs) and congenital myopathies (CMs) are a group of genetically and clinically heterogeneous degenerative primary muscle disorders with onset at birth or during infancy. The aim of this study was to genetically diagnose a cohort of 36 difficult-to-diagnose CMD and CM cases of Indian origin using next-generation sequencing methods. Furthermore, functional characterization of the novel pathogenic stop-gain variant NM_001927.4:c.448C>T in the DES gene identified in one patient of our cohort was done in order to understand their pathological role in disease phenotypes.

Megaconial congenital muscular dystrophy secondary to novel CHKB mutations resemble atypical Rett syndrome.

Megaconial congenital muscular dystrophy (CMD)(OMIM #602541), related to CHKB mutation, is a rare autosomal recessive disorder. To date, only 35 confirmed patients are recorded. We present a detailed description of the clinical, histopathological, imaging, and genetic findings of five children from four Indian families. The children had moderate-to-severe autistic behavior, hand stereotypies, and global developmental delay mimicking atypical Rett syndrome. In addition, generalized hypotonia was a common initial finding. The progression of muscle weakness was variable, with two patients having a milder phenotype and three having a severe form. Interestingly, the majority did not attain sphincter control. Only patient 1 had classical ichthyotic skin changes. Muscle biopsy in two patients showed a myopathic pattern with characteristic peripherally placed enlarged mitochondria on modified Gomori trichrome stain and electron microscopy. Genetic analysis in these patients identified three novel null mutations in CHKB [c.1027dupA (p.Ser343LysfsTer86);c.224 + 1G > T (5' splice site); c.1123C > T (p.Gln375Ter)] and one reported missense mutation, c.581G > A (p.Arg194Gln), all in the homozygous state. Megaconial CMD, although rare, forms an important group with a complex phenotypic presentation and accounted for 5.5% of our genetically confirmed CMD patients. Atypical Rett syndrome-like presentation may be a clue towards CHKB-related disorder.

Whole-exome analyses of congenital muscular dystrophy and congenital myopathy patients from India reveal a wide spectrum of known and novel mutations.

Congenital muscular dystrophies (CMDs) and congenital myopathies (CMs) are a group of genetically and clinically heterogeneous degenerative primary muscle disorders with onset at birth or during infancy. Due to vast heterogeneity, clinical examination and protein-based analyses often fail to identify the genetic causes of these diseases. The aim of this study was to genetically diagnose a cohort of 36 difficult-to-diagnose CMD and CM cases of Indian origin using next-generation sequencing methods. Whole-exome sequencing (WES) was performed to identify pathogenic mutations in previously reported CMD and CM-related genes using variant calling and stringent variant filtration process. Subsequently, in silico homology modelling and molecular dynamics simulations (MDS) studies were undertaken for a number of novel and missense variants. A total of 33 and 21 rare and deleterious mutations were identified in 28 genes previously reported in CMD and CM based on OMIM, ClinVar and Orphanet, respectively. We could accurately diagnose 54% patients (n=12/22) in the CMD group and 35% patients (n=5/14) in the CM group. Furthermore, MDS studies for mutations located in LMNA, LAMA2 and RYR1 suggest that the wild-type proteins are more stable than their mutant counterparts, implying a potential mechanism of pathogenesis. The WES findings led us to identify reported as well as novel variants for the first time in Indian patients with CMD and CM. This allowed us to achieve an accurate genetic diagnosis, which was difficult using conventional diagnostic tools. Transferring these WES findings to clinical practice will help guide clinical care of the affected patients and inform genetic counselling.

LARGE expression in different types of muscular dystrophies other than dystroglycanopathy

BackgroundAlpha-dystroglycan (αDG) is an extracellular peripheral glycoprotein that acts as a receptor for both extracellular matrix proteins containing laminin globular domains and certain arenaviruses. An important enzyme, known as Like-acetylglucosaminyltransferase (LARGE), has been shown to transfer repeating units of -glucuronic acid-β1,3-xylose-α1,3- (matriglycan) to αDG that is required for functional receptor as an extracellular matrix protein scaffold. The reduction in the amount of LARGE-dependent matriglycan result in heterogeneous forms of dystroglycanopathy that is associated with hypoglycosylation of αDG and a consequent lack of ligand-binding activity. Our aim was to investigate whether LARGE expression showed correlation with glycosylation of αDG and histopathological parameters in different types of muscular dystrophies, except for dystroglycanopathies.MethodsThe expression level of LARGE and glycosylation status of αDG were examined in skeletal muscle biopsies from 26 patients with various forms of muscular dystrophy [Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), sarcoglycanopathy, dysferlinopathy, calpainopathy, and merosin and collagen VI deficient congenital muscular dystrophies (CMDs)] and correlation of results with different histopathological features was investigated.ResultsDespite the fact that these diseases are not caused by defects of glycosyltransferases, decreased expression of LARGE was detected in many patient samples, partly correlating with the type of muscular dystrophy. Although immunolabelling of fully glycosylated αDG with VIA4–1 was reduced in dystrophinopathy patients, no significant relationship between reduction of LARGE expression and αDG hypoglycosylation was detected. Also, Merosin deficient CMD patients showed normal immunostaining with αDG despite severe reduction of LARGE expression.ConclusionsOur data shows that it is not always possible to correlate LARGE expression and αDG glycosylation in different types of muscular dystrophies and suggests that there might be differences in αDG processing by LARGE which could be regulated under different pathological conditions.

CONGENITAL MUSCULAR DYSTROPHIES: P.326Minimal clinically important difference for the Motor Function Measure in patients with congenital muscular dystrophy and congenital myopathy

To determine the minimal clinically important difference (MCID) for the motor function measure (MFM-32) in congenital muscular dystrophy and congenital myopathy patient an observational, retrospective, multicentric study was conducted on 85 congenital muscular dystrophy or congenital myopathy patients, aged 5 to 22 years at the national institute of neurological disorders and stroke of the national institutes of health and 2 French departments of paediatric physical medicine and rehabilitation. Data were collected if at least 2 MFMs were performed (MFM1 and MFM2) within 8 to 36 months of each other and if during MFM2 parents or patients were asked to provide their perceived change in functional status or strength since MFM1. Patients were divided in 3 groups according to their overall assessment of disease evolution: deterioration, stability or improvement. Absolute score changes between MFM1 and MFM2 total score (TS) and each subscore (D1, D2 and D3) were calculated for each patient. The mean score change of each group of patient reported disease evolution was provided and then groups were compared to determine if the difference was statistically significant. The MCID was calculated. Mean scores changes for D1, D2 and TS improved for patients reporting improvement (respectively 2,4±5,6; 2,1±13,3 and 2,5±7,2) and declined for patients reporting deterioration (-3,2±8,1; -1,3±15,7 and -1,3±7,2) or stability (-1,2±7,4; -2,2±10,5 and -1,5±10). The mean score for D3 was stable or improved in all patients, even if they reported an overall deterioration. The MCID was consecutively calculated for D1, D2 and TS. When designing clinical trials in congenital onset neuromuscular diseases, the use of MCID for MFM should be considered as a chief outcome measure to determine if a given intervention effects not only statistically significant change but also clinically meaningful improvements.

CONGENITAL MUSCULAR DYSTROPHIES: P.323Review of the natural history of mental development in Fukuyama congenital muscular dystrophy patients, based on a written questionnaire from their families

Fukuyama congenital muscular dystrophy (FCMD) is characterized by brain malformation caused by abnormal neurocyte migration, and presents with eye manifestations. Ninety percent of FCMD patients have the homozygote insertional mutation of the founder haplotype, and show typical progression of motor functional deficits. However, many patients with a heterozygote mutation show more severe motor and mental functional deficits. Although many prior reports on FCMD patients focused on the natural history of motor development, very few have referenced mental development. We surveyed 49 families of FCMD patients, who belonged to a patient's association, using a descriptive questionnaire. We classified our questions into 4 categories: 1) motor development, 2) social skills, 3) living skills and 4)language development. Forty-nine answers were collected, the median patient age was 7 years (range: 1.3 to 36 years). Twenty-eight patients had the homozygote mutation, 11 the heterozygote, and there was no answer for the other. All motor development milestones were delayed in all patients. Even though 80% of patients achieved single word communication, verbal development reflecting when the necessity for verbal communication arose, yielded a low evaluation in the social skill category. All patients achieved the skills needed for meal consumption more easily than other living skills such as changing their clothes. Many patients never obtained independent gait, while upper limb motions varied among patients. Furthermore, these motor function level affected their mental development. Communication with the others was also found to be an important factor for encouraging mental development. This study is a rare study focusing on the details of the mental development of FCMD. This survey is anticipated to help the families of FCMD patients as they strive to stimulate the development of their children.

Nesprin-1α-Dependent Microtubule Nucleation from the Nuclear Envelope via Akap450 Is Necessary for Nuclear Positioning in Muscle Cells

SummaryThe nucleus is the main microtubule-organizing center (MTOC) in muscle cells due to the accumulation of centrosomal proteins and microtubule (MT) nucleation activity at the nuclear envelope (NE) [1, 2, 3, 4]. The relocalization of centrosomal proteins, including Pericentrin, Pcm1, and γ-tubulin, depends on Nesprin-1, an outer nuclear membrane (ONM) protein that connects the nucleus to the cytoskeleton via its N-terminal region [5, 6, 7]. Nesprins are also involved in the recruitment of kinesin to the NE and play a role in nuclear positioning in skeletal muscle cells [8, 9, 10, 11, 12]. However, a function for MT nucleation from the NE in nuclear positioning has not been established. Using the proximity-dependent biotin identification (BioID) method [13, 14], we found several centrosomal proteins, including Akap450, Pcm1, and Pericentrin, whose association with Nesprin-1α is increased in differentiated myotubes. We show that Nesprin-1α recruits Akap450 to the NE independently of kinesin and that Akap450, but not other centrosomal proteins, is required for MT nucleation from the NE. Furthermore, we demonstrate that this mechanism is disrupted in congenital muscular dystrophy patient myotubes carrying a nonsense mutation within the SYNE1 gene (23560 G>T) encoding Nesprin-1 [15, 16]. Finally, using computer simulation and cell culture systems, we provide evidence for a role of MT nucleation from the NE on nuclear spreading in myotubes. Our data thus reveal a novel function for Nesprin-1α/Nesprin-1 in nuclear positioning through recruitment of Akap450-mediated MT nucleation activity to the NE.

Clinical manifestations and prenatal diagnosis of congenital muscular dystrophy

Objective To summarize the clinical features of 22 probands diagnosed with congenital muscular dystrophy (CMD), and to provide genetic counseling and prenatal diagnosis for 23 fetuses of these pedigrees. Methods Data of 22 CMD patients who were treated in the Pediatric Department of Peking University First Hospital during October 2006 to March 2016 were analyzed. Informed written consents for participation in this study were obtained from the parents or guardians. Prenatal diagnosis was performed using DNA samples extracted from fetal villus cells of 12 cases at 11-13 gestational weeks and amniotic fluid of 11 cases at 18-22 gestational weeks. Direct DNA sequencing by polymerase chain reaction (PCR) and multiplex ligation-dependent probe amplification (MLPA) were used to detect CMD-related gene mutations. Linkage analysis of short tandem repeats (STRs) was used to identify maternal blood contamination and biological parents. Results Thirteen out of the 22 probands with CMD were diagnosed with congenital muscular dystrophy type 1A (MDC1A), and all of them carried compound heterozygous mutations in LAMA2 gene. Prenatal diagnosis of 13 fetuses from these pedigrees found that four fetuses were wild-type, seven were heterozygotes and two carried the same mutations as their proband. Three probands with LMNA-related congenital muscular dystrophy (L-CMD) carried de novo mutations in LMNA gene. In these pedigrees, two fetuses were wild-type and one whose mother was mosaicism carried the same mutations as the proband. One proband with Ullrich congenital muscular dystrophy carried compound heterozygous mutations in COL6A2 gene and the fetus of the same pedigree was wild-type. Five probands were diagnosed with α-dystroglycanopathies. And among them, two cases of muscle-eye-brain disease (MEB) carried compound heterozygous mutations in POMGnT1 gene and the fetuses of the two peidgrees were heterozygotes; one case of congenital muscular dystrophy type 1C (MDC1C) had compound heterozygous mutations in FKRP gene and the fetus carried the same mutations; one patient diagnosed with POMGnT1-related congenital muscular dystrophy with mental retardation (CMD-MR) carried compound heterozygous mutations in POMGnT1 gene, and the fetus was positive for the same mutations; one proband with POMT1-related CMD-MR was positive for compound heterozygous mutations in POMT1 gene and the results of prenatal diagnosis for two fetuses of this pedigree showed that the first fetus had the same mutations as the proband, while the second was heterozygote. Conclusions No effective therapeutic method is available for CMD. Therefore, accurate genetic counseling and prenatal diagnosis are necessary to prevent CMD child from birth. Key words: Muscular dystrophies; Prenatal diagnosis; Genetic testing

Gapmer Antisense Oligonucleotides Suppress the Mutant Allele of COL6A3 and Restore Functional Protein in Ullrich Muscular Dystrophy.

Dominant-negative mutations in the genes that encode the three major α chains of collagen type VI, COL6A1, COL6A2, and COL6A3, account for more than 50% of Ullrich congenital muscular dystrophy patients and nearly all Bethlem myopathy patients. Gapmer antisense oligonucleotides (AONs) are usually used for gene silencing by stimulating RNA cleavage through the recruitment of an endogenous endonuclease known as RNase H to cleave the RNA strand of a DNA-RNA duplex. In this study, we exploited the application of the allele-specific silencing approach by gapmer AON as a potential therapy for Collagen-VI-related congenital muscular dystrophy (COL6-CMD). A series of AONs were designed to selectively target an 18-nt heterozygous genomic deletion in exon 15 of COL6A3 at the mRNA and pre-mRNA level. We showed that gapmer AONs can selectively suppress the expression of mutant transcripts at both pre-mRNA and mRNA levels, and that the latter strategy had a far stronger efficiency than the former. More importantly, we found that silencing of the mutant transcripts by gapmer AONs increased the deposition of collagen VI protein into the extracellular matrix, thus restoring functional protein production. Our findings provide a clear proof of concept for AON allele-specific silencing as a therapeutic approach for COL6-CMD.

Large is required for normal astrocyte migration and retinal vasculature development

BackgroundPersistent fetal vasculature (PFV) is a congenital developmental anomaly of the eye that accounts for about 5% of childhood blindness. The molecular mechanism of PFV remains unclear. As a glycosyltransferase of α-dystroglycan, LARGE mutations have been found in congenital muscular dystrophy patients with brain abnormalities. Spontaneous Large mutant mice displayed similar symptoms of human muscle–eye–brain disorders. However, the detailed roles of Large in ocular vasculature development still need to be uncovered.ResultsIn this paper, we report that a novel Large mutation generated by the piggyBac transposon insertion leads to PFV and abnormal retinal vasculature in mice. Glycosylation of α-DG, an essential component of the extracellular matrix, was significantly impaired in these Large mutants, leading to broken inner limiting membrane (ILM). As a guide of the retinal vasculature development, the distribution of retinal astrocytes became irregular within the retina, and many astrocytes abnormally migrated into the vitreous along with the hyaloid vessels in Large mutants.ConclusionsLarge is essential for ILM formation and retinal astrocyte migration. The novel Large mutant mouse can serve as a new PFV model to further dissect LARGE functions in ocular vasculature development.

Peripheral nerve injury in LAMA2-related congenital muscular dystrophy patients

Objective: To explore the injury pattern and features of peripheral nerve in congenital muscular dystrophy patients caused by LAMA2 gene mutation. Method: Seventeen patients genetically or molecular pathologically diagnosed as LAMA2-related congenital muscular dystrophy were recruited in Peking University First Hospital between 2002 and 2015. All the patients received nerve conduction velocity (NCV) and needle electromyography tests. Clinical and laboratory examination data of the patients was retrospectively analyzed. The correlation between the NCV and disease course was determined by Pearson correlation analysis. Additionally, one patient underwent a sural nerve biopsy. Result: Among these 17 identified patients (13 male and 4 female), all of them were diagnosed as congenital muscular dystrophy, and all of them underwent electrophysiological examination at ages between 1 month to 6 years. Electromyogram indicated seventeen patients of myogenic damage, of whom 10 cases were complicated with reduced NCV. Twenty-six of 95 analyzed nerves showed NCV slower than the normal average of contemporary in 17%-47%. Correlation analysis between NCV and the disease course indicated that NCV of median nerves, ulnar nerves, tibial nerves and common peroneal nerves were negatively associated with the disease course (r=-0.737, -0.771, -0.540 and -0.682, respectively; all P<0.05). Sural nerve biopsy revealed peripheral neuropathy changes of myelin. Conclusion: There is peripheral nerve injury in LAMA2-related muscular dystrophy patients. It mainly manifests as demyelinating lesions. Moreover, the NCV of peripheral nerve will decrease with the increase of the course of the disease.

P.258 - Clinical, radiological, and genetic survey of patients with muscle–eye–brain disease caused by mutations in POMGNT1

BACKGROUND: To evaluate clinical, genetic, and radiologic features of our patients with muscle-eye-brain disease. METHODS: The data of patients who were diagnosed with muscle-eye-brain disease from a cohort of patients with congenital muscular dystrophy in the Division of Pediatric Neurology of Dokuz Eylul University School of Medicine and Gaziantep Children’s Hospital between 2005 and 2013 were analyzed retrospectively. RESULTS: From a cohort of 34 patients with congenital muscular dystrophy, 12 patients from 10 families were diagnosed with muscle-eyebrain disease. The mean age of the patients was 9 � 5.5 years (2-19 years). Mean serum creatine kinase value was 2485.80 � 1308.54 IU/L (700-4267 IU/L). All patients presented with muscular hypotonia at birth followed by varying degrees of spasticity and exaggerated deep tendon reflexes in later stages of life. Three patients were able to walk. The most common ophthalmologic and radiologic abnormalities were cataracts, retinal detachment, periventricular white matter abnormalities, ventriculomegaly, pontocerebellar hypoplasia, and multiple cerebellar cysts. All of the patients had mutations in the POMGNT1 gene. The most common mutation detected in 66% of patients was c.1814 G > A (p.R605H). Two novel mutations were identified. CONCLUSIONS: We suggest that muscle-eye-brain disease is a relatively common muscular dystrophy in Turkey. It should be suspected in patients with muscular hypotonia, increased creatine kinase, and structural eye and brain abnormalities. The c.1814 G > A mutation in exon 21 of the POMGNT1 gene is apparently a common mutation in the Turkish population. Individuals with this mutation show classical features of muscle-eye-brain disease, but others may exhibit a milder phenotype and retain the ability to walk independently. Congenital muscular dystrophy patients from Turkey carrying the clinical and radiologic features of muscle-eye-brain disease should be evaluated for mutations in POMGNT1 gene.

P.254 - Japanese nationwide registry for Fukuyama congenital muscular dystrophy patients

P.254 - Japanese nationwide registry for Fukuyama congenital muscular dystrophy patients

Mutation in lamin A/C sensitizes the myocardium to exercise-induced mechanical stress but has no effect on skeletal muscles in mouse

LMNA gene encodes lamin A/C, ubiquitous proteins of the nuclear envelope. They play crucial role in maintaining nuclear shape and stiffness. When mutated, they essentially lead to dilated cardiomyopathy with conduction defects, associated or not with muscular diseases. Excessive mechanical stress sensitivity has been involved in the pathophysiology. We have previously reported the phenotype of LmnadelK32 mice, reproducing a mutation found in LMNA-related congenital muscular dystrophy patients. Heterozygous LmnadelK32/+ (Het) mice develop a progressive dilated cardiomyopathy leading to death between 35 and 70 weeks of age. To investigate the sensitivity of the skeletal muscles and myocardium to chronic exercise-induced stress, Het and wild-type (Wt) mice were subjected to strenuous running treadmill exercise for 5 weeks. Before exercise, the cardiac function of Het mice was similar to Wt-littermates. After the exercise-period, Het mice showed cardiac dysfunction and dilation without visible changes in cardiac morphology, molecular remodelling or nuclear structure compared to Wt exercised and Het sedentary mice. Contrary to myocardium, skeletal muscle ex vivo contractile function remained unaffected in Het exercised mice. In conclusion, the expression of the LmnadelK32 mutation increased the susceptibility of the myocardium to cardiac stress and led to an earlier onset of the cardiac phenotype in Het mice.

Diagnosis and etiology of congenital muscular dystrophy: We are halfway there.

To evaluate the diagnostic outcomes in a large cohort of congenital muscular dystrophy (CMD) patients using traditional and next generation sequencing (NGS) technologies. A total of 123 CMD patients were investigated using the traditional approaches of histology, immunohistochemical analysis of muscle biopsy, and candidate gene sequencing. Undiagnosed patients available for further testing were investigated using NGS. Muscle biopsy and immunohistochemical analysis found deficiencies of laminin α2, α-dystroglycan, or collagen VI in 50% of patients. Candidate gene sequencing and chromosomal microarray established a genetic diagnosis in 32% (39 of 123). Of 85 patients presenting in the past 20 years, 28 of 51 who lacked a confirmed genetic diagnosis (55%) consented to NGS studies, leading to confirmed diagnoses in a further 11 patients. Using the combination of approaches, a confirmed genetic diagnosis was achieved in 51% (43 of 85). The diagnoses within the cohort were heterogeneous. Forty-five of 59 probands with confirmed or probable diagnoses had variants in genes known to cause CMD (76%), and 11 of 59 (19%) had variants in genes associated with congenital myopathies, reflecting overlapping features of these conditions. One patient had a congenital myasthenic syndrome, and 2 had microdeletions. Within the cohort, 5 patients had variants in novel (PIGY and GMPPB) or recently published genes (GFPT1 and MICU1), and 7 had variants in TTN or RYR1, large genes that are technically difficult to Sanger sequence. These data support NGS as a first-line tool for genetic evaluation of patients with a clinical phenotype suggestive of CMD, with muscle biopsy reserved as a second-tier investigation. Ann Neurol 2016;80:101-111.

Collagen VI–NG2 axis in human tendon fibroblasts under conditions mimicking injury response

In response to injury, tendon fibroblasts are activated, migrate to the wound, and contribute to tissue repair by producing and organizing the extracellular matrix. Collagen VI is a microfibrillar collagen enriched in the pericellular matrix of tendon fibroblasts with a potential regulatory role in tendon repair mechanism. We investigated the molecular basis of the interaction between collagen VI and the cell membrane both in tissue sections and fibroblast cultures of human tendon, and analyzed the deposition of collagen VI during migration and myofibroblast trans-differentiation, two crucial events for tendon repair. Tendon fibroblast displayed a collagen VI microfibrillar network closely associated with the cell surface. Binding of collagen VI with the cell membrane was mediated by NG2 proteoglycan, as demonstrated by in vitro perturbation of collagen VI–NG2 interaction with a NG2-blocking antibody.Cultures subjected to wound healing scratch assay displayed collagen VI–NG2 complexes at the trailing edge of migrating cells, suggesting a potential role in cell migration. In fact, the addition of a NG2-blocking antibody led to an impairment of cell polarization and delay of wound closure. Similar results were obtained after in vitro perturbation of collagen VI extracellular assembly with the 3C4 anti-collagen VI antibody and in collagen VI-deficient tendon cultures of a Ullrich congenital muscular dystrophy patient carrying mutations in COL6A2 gene.Moreover, in vitro treatment with transforming growth factor β1 (TGFβ1) induced a dramatic reduction of NG2 expression, both at protein and mRNA transcript level, and the impairment of collagen VI association with the cell membrane. Instead, collagen VI was still detectable in the extracellular matrix in association with ED-A fibronectin and collagen I, which were strongly induced by TGFβ1 treatment.Our findings reveal a critical role of the NG2 proteoglycan for the binding of collagen VI to the surface of tendon fibroblasts. By interacting with NG2 proteoglycan and other extracellular matrix proteins, collagen VI regulates fibroblasts behavior and the assembly of tendon matrix, thereby playing a crucial role in tendon repair.

G.P.269 - Correlation between crural muscle fatty change and maximum motor function in Fukuyama congenital muscular dystrophy patients

G.P.269 - Correlation between crural muscle fatty change and maximum motor function in Fukuyama congenital muscular dystrophy patients

Whole Exome Sequencing Reveals DYSF, FKTN, and ISPD Mutations in Congenital Muscular Dystrophy Without Brain or Eye Involvement.

BackgroundCongenital muscular dystrophies (CMDs) are a genetically and clinically heterogeneous group of neuromuscular disorders. Several genes encoding extracellular matrix, nuclear envelope, sarcolemmal proteins and glycosylation enzymes have been implicated in CMDs. The large overlap of clinical presentations due to mutations in different genes poses a challenge for clinicians in determining disease etiology for each patient.ObjectiveWe investigated the use of whole exome sequencing (WES) in identifying the genetic cause of disease in 5 CMD patients from 3 families who presented with highly similar clinical features, including early-onset rapidly progressive weakness without brain or eye abnormalities.MethodsWhole exome sequencing was performed on DNA from affected individuals. Potential functional impacts of mutations were investigated by immunostaining on available muscle biopsies.ResultsPathogenic mutations in 3 different genes, DYSF, FKTN, and ISPD were identified in each family. Mutation in DYSF led to absence of dysferlin protein in patient muscle. Mutations in ISPD led to impaired ISDP function, as demonstrated by deficiency of α-dystroglycan glycosylation in patient muscle.ConclusionsThis study highlights the benefit of unbiased genomic approaches in molecular diagnosis of neuromuscular disorders with high clinical heterogeneity, such as the phenotypes observed in our patients. Our results suggest that dysferlin deficiency should be in the differential diagnosis of congenital and rapidly progressive muscular dystrophy, and therefore dysferlin antibody should be in the standard immunohistochemistry panel for muscle biopsies in cases with suspected CMD.