Form Of Congenital Muscular Dystrophy Research Articles

Allele-specific CRISPR-Cas9 editing inactivates a single nucleotide variant associated with collagen VI muscular dystrophy

The application of allele-specific gene editing tools can expand the therapeutic options for dominant genetic conditions, either via gene correction or via allelic gene inactivation in situations where haploinsufficiency is tolerated. Here, we used allele-targeted CRISPR/Cas9 guide RNAs (gRNAs) to introduce inactivating frameshifting indels at a single nucleotide variant in the COL6A1 gene (c.868G>A; G290R), a variant that acts as dominant negative and that is associated with a severe form of congenital muscular dystrophy. We expressed spCas9 along with allele-targeted gRNAs, without providing a repair template, in primary fibroblasts derived from four patients and one control subject. Amplicon deep-sequencing for two gRNAs tested showed that single nucleotide deletions accounted for the majority of indels introduced. While activity of the two gRNAs was greater at the G290R allele, both gRNAs were also active at the wild-type allele. To enhance allele-selectivity, we introduced deliberate additional mismatches to one gRNA. One of these optimized gRNAs showed minimal activity at the WT allele, while generating productive edits and improving collagen VI matrix in cultured patient fibroblasts. This study strengthens the potential of gene editing to treat dominant-negative disorders, but also underscores the challenges in achieving allele selectivity with gRNAs.

Psychological impact of motor impairment in tow forms of congenital muscular dystrophy

IntroductionCongenital muscular dystrophies (CMDs) represent a heterogeneous group of early-onset muscle disorders presenting primarily with hypotonia and delayed motor development. Several genes are known to be responsible for CMDs, including the LAMA2 gene, involved in merosin-deficient type 1A (MDC1A), and the FKRP gene involved in muscular dystrophy-dystroglycanopathy type B5 (MDDGB5). These two forms of CMD are autosomal recessive and are each characterized by the presence of a mutation with a founder effect in South Tunisia. Cognitive development associated with the founder mutation in the LAMA2 gene (c.8007delT) is often conserved, whereas in the founder mutation of the FKRP gene (c.1364 C>A), motor impairment is associated with intellectual disability (ID).ObjectivesTo compare the psychological impact of motor impairment in children presenting these two forms of CMD and their families.MethodsThe study consisted of a survey of parents of children with a confirmed diagnosis of MDC1A (5 from 3 unrelated families) or MDDGB5 (3 from 3 unrelated families). The correspondent founder mutation was already identified in the homozygous state by targeted sequencing. Participants’ parents completed the Parent Strengths and Difficulties Questionnaire (SDQ), a behavioral screening tool designed for children aged from 2 to 17 years. The SDQ assesses emotional symptoms, behavior problems, hyperactivity, and peer relationships; The SDQ Impact Supplement assesses the impact of all these children’s difficulties on their families.ResultsThe average age of the children was 4.95±3.92 with two children who were not assessable by the SDQ (age< 2 years). Unlike children with MDC1A, ID has been reported in all children with MDDGB5. The mean SDQ total score for children with MDC1A was 11, whereas the mean score for children with MDDGB5 was 14.875, reflecting greater difficulty for children with MDDGB5. The family impact score was higher in families with children with MDDGB5 than in children with MDC1A (10,5 vs 7), which may be due to the burden of management of the ID associated with the motor impairment. The more pronounced difficulties associated with MDDGB5 are likely to be related to the associated ID. Whereas in MDC1A, the difficulties observed are related to the direct impact of the motor impairment. The presence of cognitive disorders associated with a motor deficit aggravates behavioral adaptation and makes the management of these children more difficult.ConclusionsIn the absence of a comparable study in the literature, the present is conducting future studies on the behavioral profile of children with CMD to obtain a better understanding of their difficulties in everyday life and to develop interventions adapted to their familiesDisclosure of InterestNone Declared

FP.39 An international retrospective early natural history study of LAMA2-related dystrophies

<i>LAMA2</i>-related dystrophies (LAMA2-RDs), caused by recessively inherited mutations in the <i>LAMA2</i> gene, represent one of the most common forms of congenital muscular dystrophy and are characterized by a complete or partial deficiency of laminin-211 (merosin). Patients with LAMA2-RDs presenting congenitally typically have a phenotype of severe weakness, delayed motor milestones, failure to thrive and progressive respiratory insufficiency. While a comprehensive prospective natural history study has been performed in LAMA2-RD patients >5 years, the early natural history of patients with LAMA2-RD 5 years and younger has not been comprehensively characterized. Extracting data from the CMD international registry, we describe a cohort of 62 patients with LAMA2-RD from 10 countries. Data for ages birth-5 years was retrospectively collected from the medical records. Inclusion criteria required that the patients had either two causative <i>LAMA2</i> variants or one confirmed causative <i>LAMA2</i> variant and a supporting clinical phenotype. Initial analyses reveal key findings including significant elevations of creatine kinase during the neonatal period which declined rapidly within the first few months of life. The mean age of first recognition of abnormal brain white matter appearance on MRI was 12.0 months. The first report of failure to thrive was at a mean age of 23.4 months. Noninvasive ventilation was initiated in half the patients by 24 months of age. This data represents the largest multinational retrospective early natural history study of LAMA2-RD which provides data essential for understanding early clinical history, especially as international, prospective early natural history data collection is in progress. Promising therapies in preclinical development for LAMA2-RD may ameliorate the phenotype of LAMA2-RD, particularly when initiated early in the course of the disease, making the comprehensive understanding of early natural history of LAMA2-RD timely and of great importance.

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.

Megaconial congenital muscular dystrophy due to novel CHKB variants: a case report and literature review

BackgroundCholine kinase beta (CHKB) catalyzes the first step in the de novo biosynthesis of phosphatidyl choline and phosphatidylethanolamine via the Kennedy pathway. Derangement of this pathway might also influence the homeostasis of mitochondrial membranes.Autosomal recessive CHKB mutations cause a rare form of congenital muscular dystrophy known as megaconial congenital muscular dystrophy (MCMD).Case presentationWe describe a novel proband presenting MCMD due to unpublished CHKB mutations. The patient is a 6-year-old boy who came to our attention for cognitive impairment and slowly progressive muscular weakness. He was the first son of non-consanguineous healthy parents from Sri Lanka. Neurological examination showed proximal weakness at four limbs, weak osteotendinous reflexes, Gowers’ maneuver, and waddling gate. Creatine kinase levels were mildly increased. EMG and brain MRI were normal. Left quadriceps skeletal muscle biopsy showed a myopathic pattern with nuclear centralizations and connective tissue increase. Histological and histochemical staining suggested subsarcolemmal localization and dimensional increase of mitochondria. Ultrastructural analysis confirmed the presence of enlarged (“megaconial”) mitochondria. Direct sequencing of CHKB identified two novel defects: the c.1060G > C (p.Gly354Arg) substitution and the c.448-56_29del intronic deletion, segregating from father and mother, respectively. Subcloning of RT-PCR amplicons from patient’s muscle RNA showed that c.448-56_29del results in the partial retention (14 nucleotides) of intron 3, altering physiological splicing and transcript stability. Biochemical studies showed reduced levels of the mitochondrial fission factor DRP1 and the severe impairment of mitochondrial respiratory chain activity in patient’s muscle compared to controls.ConclusionsThis report expands the molecular findings associated with MCMD and confirms the importance of considering CHKB variants in the differential diagnosis of patients presenting with muscular dystrophy and mental retardation. The clinical outcome of MCMD patients seems to be influenced by CHKB molecular defects. Histological and ultrastructural examination of muscle biopsy directed molecular studies and allowed the identification and characterization of an intronic mutation, usually escaping standard molecular testing.

The many roles of dystroglycan in nervous system development and function: Dystroglycan and neural circuit development: Dystroglycan and neural circuit development.

The glycoprotein dystroglycan was first identified in muscle, where it functions as part of the dystrophin glycoprotein complex to connect the extracellular matrix to the actin cytoskeleton. Mutations in genes involved in the glycosylation of dystroglycan cause a form of congenital muscular dystrophy termed dystroglycanopathy. In addition to its well-defined role in regulating muscle integrity, dystroglycan is essential for proper central and peripheral nervous system development. Patients with dystroglycanopathy can present with a wide range of neurological perturbations, but unraveling the complex role of Dag1 in the nervous system has proven to be a challenge. Over the past two decades, animal models of dystroglycanopathy have been an invaluable resource that has allowed researchers to elucidate dystroglycan's many roles in neural circuit development. In this review, we summarize the pathways involved in dystroglycan's glycosylation and its known interacting proteins, and discuss how it regulates neuronal migration, axon guidance, synapse formation, and its role in non-neuronal cells.

A Mosaic Mutation in the LAMA2 Gene in a Case of Merosin-deficient Congenital Muscular Dystrophy

Merosine deficient congenital muscular dystrophy is one of the most common forms of congenital muscular dystrophy. This disease is caused by a primary deficiency or a functionally inactive form of the protein merosin in muscle tissue. The type of inheritance of this disease is autosomal recessive. De novo variants with this type of inheritance are rare, and it is quite possible that the de novo variant may hide a mosaic form in the parent of an affected child. We present a birth family with two affected children who inherited a previously undescribed pathogenic variant c.1755del from their mother and a previously described pathogenic variant c.9253C > T in the LAMA2 gene from their mosaic father. LAMA2 gene mutation analysis was performed by mass parallel sequencing and direct sequencing of genomic DNAs.

Historical aspects of muscle research in the Dubowitz Neuromuscular Centre: the Hammersmith days

Historical aspects of muscle research in the Dubowitz Neuromuscular Centre: the Hammersmith days

OTHER NMDs: EP.350 A study of LINC complex proteins reveals temporal emerin and SUN2 expression changes during myoblast differentiation

Mutations in nuclear envelope (NE) proteins, emerin, lamin A/C, nesprin-1/2 and SUN1/SUN2 have been identified in the causation of Emery-Dreifuss muscular dystrophy (EDMD) and some extremely rare forms of congenital muscular dystrophy (CMD). These NE proteins are all components of the linker of nucleoskeleton and cytoskeleton (LINC) complex, a structure that spans the NE and connects the nuclear lamina (NL) to the cytoskeleton. Some progress has been made to understand the molecular pathways acting downstream of the defective genes, however the roles of these proteins during myoblast development and differentiation are still not fully understood.

Exome reanalysis and proteomic profiling identified TRIP4 as a novel cause of cerebellar hypoplasia and spinal muscular atrophy (PCH1)

TRIP4 is one of the subunits of the transcriptional coregulator ASC-1, a ribonucleoprotein complex that participates in transcriptional coactivation and RNA processing events. Recessive variants in the TRIP4 gene have been associated with spinal muscular atrophy with bone fractures as well as a severe form of congenital muscular dystrophy. Here we present the diagnostic journey of a patient with cerebellar hypoplasia and spinal muscular atrophy (PCH1) and congenital bone fractures. Initial exome sequencing analysis revealed no candidate variants. Reanalysis of the exome data by inclusion in the Solve-RD project resulted in the identification of a homozygous stop-gain variant in the TRIP4 gene, previously reported as disease-causing. This highlights the importance of analysis reiteration and improved and updated bioinformatic pipelines. Proteomic profile of the patient’s fibroblasts showed altered RNA-processing and impaired exosome activity supporting the pathogenicity of the detected variant. In addition, we identified a novel genetic form of PCH1, further strengthening the link of this characteristic phenotype with altered RNA metabolism.

Identification of a novel LAMA2 c.2217G\u2009>\u2009A, p.(Trp739*) mutation in a Moroccan patient with congenital muscular dystrophy: a case report

BackgroundMerosin-deficient congenital muscular dystrophy type 1A (MDC1A) is a rare autosomal recessive genetic condition caused by deleterious mutations in the LAMA2 gene encoding the laminin-α2 chain. It is the most frequent subtype of congenital muscular dystrophies (CMDs) characterized by total laminin-α2 deficiency with muscle weakness at birth or in the first six months of life. To the best of our knowledge, this study reports the first molecular diagnosis and genetic defect of this heterogeneous form of CMD performed in a Moroccan medical genetic center using next-generation sequencing (NGS). It allows us to expand the mutational spectrum of the LAMA2 gene.Case presentationWe report the case of a female Moroccan child with clinical and paraclinical features in favor of a CMD. She has global congenital hypotonia with generalized muscle weakness, psychomotor retardation, increased serum creatine kinase, and normal brain scan at the age of six months. Targeted NGS leads to the identification of a novel homozygous nonsense mutation c.2217G > A, p.(Trp739*) in the exon 16 of LAMA2. Sanger sequencing confirmed this mutation in the affected patient and showed that her parents are heterozygous carriers.ConclusionsA modern genetic analysis by NGS improves the genetic diagnosis pathway for adequate genetic counseling of affected families more precisely. An accession number from the National Center for Biotechnology Information (NCBI) ClinVar database was retrieved for this novel LAMA2 mutation.

Novel Radiological Brain Anomalies in a Patient with Congenital Muscular Dystrophy due to FKRP Mexican Founder Mutation c.1387A > G: Review of the Literature.

Mutations in the FKRP gene result in phenotypes with severe forms of congenital muscular dystrophies (CMD) and limb-girdle muscular dystrophies. We present a Mexican patient with a pathogenic homozygous mutation in the FKRP gene (c.1387A > G, p.Asn463Asp) and CMD with radiological brain anomalies as disseminated hyperintensity lesions and discrete generalized cortical atrophy. These findings have not been reported to the best of our knowledge in other patients with the same mutation. The mutation c.1387A > G, p.Asn463Asp in the FKRP gene has been described to have a founder effect in central Mexico, since all the patients described to date are of Hispanic origin. Therefore, we emphasize studying mutations in the FKRP gene in Hispanic pediatric patients with clinical suspicion of CMD. Clinical and molecular diagnosis of specific CMD subtypes is needed to help clarify the prognosis, management, and genetic counseling to the patient and families.

NAD+ enhances ribitol and ribose rescue of α-dystroglycan functional glycosylation in human FKRP-mutant myotubes.

Mutations in the fukutin-related protein (FKRP) cause Walker-Warburg syndrome (WWS), a severe form of congenital muscular dystrophy. Here, we established a WWS human induced pluripotent stem cell-derived myogenic model that recapitulates hallmarks of WWS pathology. We used this model to investigate the therapeutic effect of metabolites of the pentose phosphate pathway in human WWS. We show that functional recovery of WWS myotubes is promoted not only by ribitol but also by its precursor ribose. Moreover, we found that the combination of each of these metabolites with NAD+ results in a synergistic effect, as demonstrated by rescue of α-dystroglycan glycosylation and laminin binding capacity. Mechanistically, we found that FKRP residual enzymatic capacity, characteristic of many recessive FKRP mutations, is required for rescue as supported by functional and structural mutational analyses. These findings provide the rationale for testing ribose/ribitol in combination with NAD+ to treat WWS and other diseases associated with FKRP mutations.

Limb-Girdle Muscular Dystrophy type R9 linked to the FKRP gene: state of the art and therapeutic perspectives

Mutations in the FKRP gene encoding the fukutin-related protein (FKRP) cause a wide spectrum of myopathies, ranging from severe forms of congenital muscular dystrophies associated with structural abnormalities of the central nervous system, to exertional myalgia or asymptomatic hyperCKemia, and to a form of limb girdle muscular dystrophy, LGMD-R9, (ex-LGMD-2I). LGMD-R9 is characterized by a proximal girdle deficit predominantly in the lower limbs to start with, with respiratory and cardiac damage that may affect the vital prognosis. Serum CK levels are markedly elevated and, on muscle biopsy, is detected a dystrophic formula associated with a reduction in the glycosylation of α-dystroglycan by immunostains and immunoblotting. Muscle MRI typically shows damage to proximal muscles (iliopsoas, adductors, gluteus maximus, quadriceps) with relative preservation of the muscles of the anterior compartment of the thighs (gracilis and sartorius). Genetic analysis, by specific sequencing of the FKRP gene or of a panel grouping together all the genes involved in the glycosylation of α-dystroglycan, or a larger panel of genes, generally confirms the diagnosis, the most frequent mutation being the missense p.(Leu276Ile). Currently, treatment of LGMD-R9 is symptomatic, requiring a multidisciplinary approach. A prospective study of the natural history of the disease is currently underway in Europe (GNT-015-FKRP). New therapeutic approaches are envisaged, such as gene therapy mediated by vectors derived from the adeno-associated virus (AAV). This is effective in animal models, allowing correction of defects in the glycosylation of alpha-dystroglycan and an increase in its binding capacity to the extracellular matrix. At the same time, preclinical studies have shown, in an animal model, the efficacy of ribitol, an alcohol pentose found in natural compounds, which has led to a phase I trial whose clinical development is underway.

CONGENITAL MUSCULAR DYSTROPHIES: P.192 Gene therapy approach for LAMA2-related muscular dystrophy using linker proteins

LAMA2-related muscular dystrophy (LAMA2 MD or MDC1A) is the most frequent form of congenital muscular dystrophies. It is caused by mutations in LAMA2, the gene encoding laminin-α2, the long arm of the heterotrimeric (α2, β1, γ1) basement membrane protein laminin-211 (Lm-211). Patients with the early-onset form lack Lm-211 due to biallelic loss-of-function mutations in LAMA2. The large size of the cDNA encoding laminin-α2 and the heterotrimeric structure of Lm-211 present a challenge for gene replacement or gene editing strategies.

Merosin-deficient muscular dystrophy: pathogenesis, clinical manifestations and therapeutic strategies

Merosin-deficient muscular dystrophy is the most common form of congenital muscular dystrophies (СMD), characterized by genetic heterogeneity and a severe course in most cases. CMD pathogenesis is associated with a partial or complete absence of laminin 2 chains in the basal membrane of muscle fiber caused by a mutation in theLAMA2gene. The clinical manifestations of LAMA2-associated muscular dystrophy vary from severe СMD (СMD 1A) with an early onset to a relatively mild course with a late onset and phenotype of limb-girdle muscular dystrophy. CMD type 1A is characterized by a delay in motor development from the first months of the life (while the vast majority of children do not master the ability to walk independently), facial muscles weakness, ptosis, ophthalmoplegia, spine rigidity, early occurrence of contractures in the shoulder, elbow, hip and knee joints, restrictive respiratory disorders, nutritional problems, such as disorders of swallowing and chewing, gastroesophageal reflux, low body weight; some children suffer from mental retardation and epilepsy.

Novel mutation identification and copy number variant detection via exome sequencing in congenital muscular dystrophy.

BackgroundCongenital muscular dystrophy type 1A (MDC1A), also termed merosin‐deficient congenital muscular dystrophy (CMD), is a severe form of CMD caused by mutations in the laminin α2 gene (LAMA2). Of the more than 300 likely pathogenic variants found in the Leiden Open Variant Database, the majority are truncating mutations leading to complete LAMA2 loss of function, but multiple copy number variants (CNVs) have also been reported with variable frequency.MethodsWe collected a cohort of individuals diagnosed with likely MDC1A and sought to identify both single nucleotide variants and small and larger CNVs via exome sequencing by extending the analysis of sequencing data to detect splicing changes and CNVs.ResultsStandard exome analysis identified multiple novel LAMA2 variants in our cohort, but only four cases carried biallelic variants. Since likely truncating LAMA2 variants are often found in heterozygosity without a second allele, we performed additional splicing and CNV analysis on exome data and identified one splice change outside of the canonical sequences and three CNVs, in the remaining four cases.ConclusionsOur findings support the expectation that a portion of MDC1A cases may be caused by at least one CNV allele and show how these changes can be effectively identified by additional analysis of existing exome data.

Clinical and genetic characteristics of congenital muscular dystrophies (Part 1)

Congenital muscular dystrophy is an extremely heterogeneous group of hereditary neuromuscular diseases that are clinically characterized by muscular hypotonia, progressive muscle weakness, and dystrophic changes in the muscles. Overlapping clinical symptoms and many genes that have to be analyzed to determine the specific form of the disease in the patient make diagnosis difficult. The molecular genetic stage of diagnosis includes many different methods depending on the clinical hypothesis and their application has not lost its relevance even in the era of massive parallel sequencing. In addition to DNA sequence analysis, the analysis of muscle protein expression can also play a significant role in the diagnosis of congenital muscular dystrophy. In the review, we will consider the most important etiological, pathophysiological, clinical and laboratory data of the main forms of congenital muscular dystrophy known today.

Exon-Skipping Oligonucleotides Restore Functional Collagen VI by Correcting a Common COL6A1 Mutation in Ullrich CMD

Collagen VI-related congenital muscular dystrophies (COL6-CMDs) are the second most common form of congenital muscular dystrophy. Currently, there is no effective treatment available. COL6-CMDs are caused by recessive or dominant mutations in one of the three genes encoding for the α chains of collagen type VI (COL6A1, COL6A2, and COL6A3). One of the most common mutations in COL6-CMD patients is a de novo deep intronic c.930+189C > T mutation in COL6A1 gene. This mutation creates a cryptic donor splice site and induces incorporation of a novel in-frame pseudo-exon in the mature transcripts. In this study, we systematically evaluated the splice switching approach using antisense oligonucleotides (ASOs) to correct this mutation. Fifteen ASOs were designed using the RNA-tiling approach to target the misspliced pseudo-exon and its flanking sequences. The efficiency of ASOs was evaluated at RNA, protein, and structural levels in skin fibroblasts established from four patients carrying the c.930+189C > T mutation. We identified two additional lead ASO candidates that efficiently induce pseudo-exon exclusion from the mature transcripts, thus allowing for the restoration of a functional collagen VI microfibrillar matrix. Our findings provide further evidence for ASO exon skipping as a therapeutic approach for COL6-CMD patients carrying this common intronic mutation.

Cellular rescue in a zebrafish model of congenital muscular dystrophy type 1A

Laminins comprise structural components of basement membranes, critical in the regulation of differentiation, survival and migration of a diverse range of cell types, including skeletal muscle. Mutations in one muscle enriched Laminin isoform, Laminin alpha2 (Lama2), results in the most common form of congenital muscular dystrophy, congenital muscular dystrophy type 1A (MDC1A). However, the exact cellular mechanism by which Laminin loss results in the pathological spectrum associated with MDC1A remains elusive. Here we show, via live tracking of individual muscle fibres, that dystrophic myofibres in the zebrafish model of MDC1A maintain sarcolemmal integrity and undergo dynamic remodelling behaviours post detachment, including focal sarcolemmal reattachment, cell extension and hyper-fusion with surrounding myoblasts. These observations imply the existence of a window of therapeutic opportunity, where detached cells may be “re-functionalised” prior to their delayed entry into the cell death program, a process we show can be achieved by muscle specific or systemic Laminin delivery. We further reveal that Laminin also acts as a pro-regenerative factor that stimulates muscle stem cell-mediated repair in lama2-deficient animals in vivo. The potential multi-mode of action of Laminin replacement therapy suggests it may provide a potent therapeutic axis for the treatment for MDC1A.