Project description:Introduction: Myotonic dystrophy of type 1 (DM1), the most common dystrophy in adults, is an autosomal dominant inherited disease, affecting around 1 in 8000 person. Patients suffering from DM1 develop essentially muscle disorders such as myotonia, muscle weakness, muscle loss and atrophy. The disease is caused by the mutation of the DMPK "Dystrophia Myotonica Protein Kinase" gene. The mutation correspond to an abnormally large expansion of CTG tri-nucleotides repeats located in the 3'-untranslated region of this gene. Expanded CTG repeats are normally transcribed, but accumulates in RNA aggregates that sequester RNA-binding proteins such as the splicing regulator MBNL1. Consequently, due to MBNL1 sequestration, DM1 is characterized by aberrant splicing of a wide number of mRNA, which are themselves responsible for the symptoms observed in the disease. Purpose: To determine as much as possible novel splicing misregulations taking place in DM1 skeletal muscle, we performed a paired-end RNA sequencing (RNA-seq) using muscles samples of normal individuals (CTRL, n=3) versus muscles of DM1 patients (DM1, n=3). The data was analyzed by a bioinformatical software, called MISO, in order to map the alternative splicing changes between normal and DM1 muscle. The aim of this study was to get a broad and precise view of the splicing changes occurring in DM1 muscle.
Project description:Myotonic dystrophy type 1 (DM1) is the most common form of adult-onset muscular dystrophy and is caused by an repeat expansion [r(CUG)exp] located in the 3' untranslated region of the DMPK gene. Symptoms include skeletal and cardiac muscle dysfunction and fibrosis. In DM1, there is a lack of established biomarkers in routine clinical practice. Thus, we aimed to identify a blood biomarker with relevance for DM1-pathophysiology and clinical presentation.
Project description:Distinct RNA-mediated impacts on alternative splicing and extracellular matrix gene expression in a mouse model of myotonic dystrophy. Myotonic dystrophy (DM1) is associated with expression of expanded CTG DNA repeats as RNA (CUGexp RNA). To test whether CUGexp RNA creates a global splicing defect, we compared skeletal muscle of two mouse DM1 models, one expressing a CTGexp transgene, and another homozygous for a defective Mbnl1 gene. Strong correlation in splicing changes for ~100 new Mbnl1-regulated exons indicates loss of Mbnl1 explains >80% of the splicing pathology due to CUGexp RNA. In contrast, only about half of mRNA level changes can be attributed to loss of Mbnl1, indicating CUGexp RNA has Mbnl1-independent effects, particularly on mRNAs for extracellular matrix (ECM) proteins. We propose that CUGexp RNA causes two separate effects: loss of Mbnl1 function, disrupting splicing, and loss of another function that disrupts ECM mRNA regulation, possibly mediated by MBNL2. These findings reveal unanticipated similarities between DM1 and other muscular dystrophies. MBNL1 knockout and HSALR mice on FVB background. To test whether CUGexp RNA creates a global splicing defect, we compared skeletal muscle of two mouse DM1 models, one expressing a CTGexp transgene, and another homozygous for a defective Mbnl1 gene. These samples were compared to the skeletal muscle of a wildtype mouse.
Project description:The prevailing patho-mechanistic paradigm for myotonic dystrophy (DM) is that the aberrant presence of embryonic isoforms is responsible for many, if not most, aspects of the pleiotropic disease phenotype. In order to identify such aberrantly expressed isoforms in skeletal muscle of DM type 1 (DM1) and type 2 (DM2) patients, we utilized the Affymetrix exon array to characterize the largest collection of DM samples analyzed to date, and included non-DM dystrophic muscle samples (NMD) as disease controls. For the exon array profiling on the Human Exon 1.0 ST array (Affymetrix Santa Clara, CA) we used a panel of 28 skeletal muscle biopsies from DM1 (n=8), DM2 (n=10), Becker muscular dystrophy, BMD, (n=3), Duchenne muscular dystrophy, DMD (n=1), Tibial muscular dystrophy, TMD, (n=2) and normal skeletal muscle (n=4). Normal control RNAs were purchased commercially. .CEL files were generated with a pre-commercial version of the Affymetrix processing software, and the headers might be non-standard. In our lab, users of the Partek software could use them, whereas users of GeneSpring had to modify the header information.
Project description:Misregulated alternative splicing appears to be a major factor in the pathogenesis of myotonic dystrophy. The present study was done to further explore alternative splicing in this condition by doing exon-level analysis of mRNA from skeletal muscle of 8 subjects with type 1 myotonic dystrophy, 7 subjects with type 2 myotonic dystrophy, 8 disease controls (subjects with facioscapulohumeral muscular dystrophy), and 8 healthy controls . The ratios of signals from the various exons of a gene provided an index of altered exon inclusion/exclusion that was independent of the overall expression of that gene. There were numerous transcripts for which there was evidence of abnormal alternative splicing in subjects with myotonic dystrophy. For many of these transcripts, the abnormal splicing was confirmed by an independent RT-PCR approach. 31 subjects, one sample per subject, four groups: healthy subjects (n = 8), facioscapulohumeral dystrophy (n = 8), type 1 myotonic dystrophy (n = 8), type 2 myotonic dystrophy (n = 7)
Project description:We have developed an inducible, skeletal muscle-specific mouse model of DM1 (CUG960) that expresses 960 CUG repeat-expressing animals (CUG960) in the context of human DMPK exons 11-15. CUG960 RNA-expressing mice induced at postnatal day 1, as well as adult-onset animals, show clear, measurable muscle wasting accompanied by severe histological defects including central myonuclei, reduced fiber cross-sectional area, increased percentage of oxidative myofibers, the presence of nuclear RNA foci that colocalize with Mbnl1 protein, and increased Celf1 protein in severely affected muscles. Importantly, muscle loss, histological abnormalities and RNA foci are reversible, demonstrating recovery upon removal of toxic RNA. RNA-seq and protein array analysis indicate that the balance between anabolic and catabolic pathways that normally regulate muscle mass may be disrupted by deregulation of platelet derived growth factor receptor beta signaling and the PI3K/AKT pathways, along with prolonged activation of AMP-activated protein kinase alpha signaling. Similar changes were detected in DM1 skeletal muscle compared with unaffected controls.
Project description:Misregulated alternative splicing appears to be a major factor in the pathogenesis of myotonic dystrophy. The present study was done to further explore alternative splicing in this condition by doing exon-level analysis of mRNA from skeletal muscle of 8 subjects with type 1 myotonic dystrophy, 7 subjects with type 2 myotonic dystrophy, 8 disease controls (subjects with facioscapulohumeral muscular dystrophy), and 8 healthy controls . The ratios of signals from the various exons of a gene provided an index of altered exon inclusion/exclusion that was independent of the overall expression of that gene. There were numerous transcripts for which there was evidence of abnormal alternative splicing in subjects with myotonic dystrophy. For many of these transcripts, the abnormal splicing was confirmed by an independent RT-PCR approach.
Project description:Distinct RNA-mediated impacts on alternative splicing and extracellular matrix gene expression in a mouse model of myotonic dystrophy. Myotonic dystrophy (DM1) is associated with expression of expanded CTG DNA repeats as RNA (CUGexp RNA). To test whether CUGexp RNA creates a global splicing defect, we compared skeletal muscle of two mouse DM1 models, one expressing a CTGexp transgene, and another homozygous for a defective Mbnl1 gene. Strong correlation in splicing changes for ~100 new Mbnl1-regulated exons indicates loss of Mbnl1 explains >80% of the splicing pathology due to CUGexp RNA. In contrast, only about half of mRNA level changes can be attributed to loss of Mbnl1, indicating CUGexp RNA has Mbnl1-independent effects, particularly on mRNAs for extracellular matrix (ECM) proteins. We propose that CUGexp RNA causes two separate effects: loss of Mbnl1 function, disrupting splicing, and loss of another function that disrupts ECM mRNA regulation, possibly mediated by MBNL2. These findings reveal unanticipated similarities between DM1 and other muscular dystrophies.
Project description:Myotonic dystrophy type 1 (DM1) is a dominantly inherited disease that affects multiple organ systems. Cardiac dysfunction is the second leading cause of death in DM1. We quantified gene expression in heart tissue from a heart-specific DM1 mouse model (EpA960/MCM) which inducibly expresses human DMPK exon 15 containing 960 CUG expanded repeats and that reproduced Celf1 up regulation. To assess if, in addition to splicing and miRNA defects, CUGexp RNA also perturbed the steady state mRNA levels of genes, we carried out a microarray study on wildtype E14, adult, MCM controls and DM1 mouse hearts. As anticipated we noted a large number of genes to be developmentally regulated in wildtype hearts, however, within 72h of induction of CUGexp RNA there appeared to be a coordinate adult-to-embryonic shift in steady state levels of many genes. We identified transcripts over-expressed or under-expressed in hearts of wildtype adult mice, wildtype embryonic day 14 (E14), and DM1 mice induced to express CUGexp RNA for 72h and 1wk, when compared to MCM controls. Multiple group comparison.
Project description:Myotonic dystrophy (DM) is the most common autosomal dominant muscular dystrophy and encompasses both skeletal muscle and cardiac complications. Myotonic dystrophy is nucleotide repeat expansion disorder in which type 1 (DM1) is due to a trinucleotide repeat expansion on chromosome 19 and type 2 (DM2) arises from a tetranucleotide repeat expansion on chromosome 3. Developing representative models of myotonic dystrophy in animals has been challenging due to instability of nucleotide repeat expansions, especially for DM2 which is characterized by nucleotide repeat expansions often greater than 5000 copies. To investigate mechanisms of human DM, we generated cellular models of DM1 and DM2. We used regulated MyoD expression to reprogram urine-derived cells into myotubes. In this cell model, we found impaired dystrophin expression, MBNL foci, and aberrant splicing in DM1 but not in DM2 cells. We generated induced pluripotent stem cells (iPSC) from healthy controls, DM1 and DM2 subjects and differentiated these into cardiomyocytes. DM1 and DM2 cells displayed an increase in RNA foci concomitant with cellular differentiation. IPSC-derived cardiomyocytes from DM1 but not DM2 had aberrant splicing and MBNL sequestration. High resolution imaging revealed tight association between MBNL clusters and RNA FISH foci in DM1. Ca2+ transients differed between DM1 and DM2 IPSC-derived cardiomyocytes and from healthy control cells. RNA-sequencing from DM1 and DM2 iPSC-derived cardiomyocytes both altered gene expression as well as distinct splicing patterns as differential between DM1 and DM2. Together these data support that DM1 and DM2, despite some shared clinical and molecular features, have distinct pathological signatures.