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: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. 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:Myotonic dystrophes (DM), the most common adult muscular dystrophy, are the first recognized examples of RNA-mediated diseases in which expression of mutant RNAs containing expanded CUG or CCUG repeats interfere with the splicing of other mRNAs. Using whole-genome microarrays, we found that alternative splicing of the BIN1 mRNA is altered in DM skeletal muscle tissues, resulting in the expression of an inactive form of BIN1 deprived of phosphoinositide-binding and membrane-tubulating activities. BIN1 is involved in tubular invaginations of the plasma membrane and is essential for biogenesis of the muscle T-tubules, which are specialized skeletal muscle membrane structures essential to correct excitation-contraction (E-C) coupling. Mutations in the BIN1 gene cause centronuclear myopathy (CNM) that shares some histopathological features with DM, and both diseases are characterized by muscle weakness. Consistent with a loss-of-function of BIN1, muscle T-tubules were altered in DM patients, and membrane tubulation was restored upon expression of the correct splicing form of BIN1 in DM muscle cells. By deciphering the mechanism of BIN1 splicing mis-regulation we demonstrate that the splicing regulator, MBNL1, which is sequestered by expanded CUG and CCUG in DM, binds the BIN1 pre-mRNA and regulates directly its alternative splicing. Finally, reproducing BIN1 splicing alteration in mice is sufficient to reproduce the DM features of T-tubule alterations and muscle weakness. We propose that alteration of BIN1 alternative splicing regulation leads to muscle weakness, a predominant pathological feature of DM. Exon-Array analysis of control and CDM1 muscle primary cultures 10 days of differentiation
Project description:Myotonic dystrophes (DM), the most common adult muscular dystrophy, are the first recognized examples of RNA-mediated diseases in which expression of mutant RNAs containing expanded CUG or CCUG repeats interfere with the splicing of other mRNAs. Using whole-genome microarrays, we found that alternative splicing of the BIN1 mRNA is altered in DM skeletal muscle tissues, resulting in the expression of an inactive form of BIN1 deprived of phosphoinositide-binding and membrane-tubulating activities. BIN1 is involved in tubular invaginations of the plasma membrane and is essential for biogenesis of the muscle T-tubules, which are specialized skeletal muscle membrane structures essential to correct excitation-contraction (E-C) coupling. Mutations in the BIN1 gene cause centronuclear myopathy (CNM) that shares some histopathological features with DM, and both diseases are characterized by muscle weakness. Consistent with a loss-of-function of BIN1, muscle T-tubules were altered in DM patients, and membrane tubulation was restored upon expression of the correct splicing form of BIN1 in DM muscle cells. By deciphering the mechanism of BIN1 splicing mis-regulation we demonstrate that the splicing regulator, MBNL1, which is sequestered by expanded CUG and CCUG in DM, binds the BIN1 pre-mRNA and regulates directly its alternative splicing. Finally, reproducing BIN1 splicing alteration in mice is sufficient to reproduce the DM features of T-tubule alterations and muscle weakness. We propose that alteration of BIN1 alternative splicing regulation leads to muscle weakness, a predominant pathological feature of DM.
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:Mapping MBNL-regulated genome-wide alternative polyadenylation: We report that depletion of Mbnl proteins in mouse embryo fibroblasts (MEFs), DM mouse model quadriceps muscle, and DM-autopsy muscle tissue leads to mis-regulation of alternative polyadenylation We compared WT, Mbnl1/2KO, Mbnl1/2KO/3siRNA, and Mbnl1/2KO/scrambled siRNA MEFs (n=2 for each group) to evaluate alternative polyadenylation shifts that occur due to progressive loss of Mbnl proteins. We also compared WT (1 day old, and 4 months old, n=2 each) and HSALR mouse model (4 months old, n=2) of myotonic dystrophy for developmental alternative polyadenylation defects in myotonic dystrophy. Finally, we compared control and DM1 autopsy muscle tissues (n=3) for changes in alternative polyadenylation. We performed HITS-CLIP analysis of binding sites of Mbnl1, Mbnl2 and Mbnl3 in MEFs (n=3 each). We also performed HITS-CLIP analysis for major skeletal muscle Mbnl protein, Mbnl1 in FVB WT adult muscle (4 months, n=3). Finally we performed HITS-CLIP analysis for CPSF6 in WT and Mbnl1/2 KO MEFs (n=3 each) Please note that the 'readme_Table.txt' describes the contents of 'Table S*.xlsx' files, and the readme_method.txt include additional details about experiemenal procedures.
Project description:Skeletal muscle excitation-contraction (EC) coupling is independent of calcium influx. In fact alternative splicing of the voltage-gated calcium channel CaV1.1 actively suppresses calcium currents in mature muscle. Why this might be necessary is not known. However, splicing defects causing aberrant expression of the calcium-conducting embryonic CaV1.1e splice variant correlate with muscle weakness in myotonic dystrophy. Here we deleted CaV1.1 exon 29 in mice. The continued expression of CaV1.1e resulted in increased calcium influx during EC coupling and spontaneous calcium sparks. While overall motor performance was normal, muscle force was reduced, endurance enhanced, and the fiber type composition shifted toward slower fibers. In contrast, oxidative enzyme activity and the mitochondrial content declined. Together with the dysregulation of key regulators of the slow program these findings indicate that limiting calcium influx during skeletal muscle EC coupling is important for the calcium signalâs secondary function in the activity-dependent regulation of fiber type composition. Differential gene expression between soleus and EDL muscle fibres from wildtype and Cav1.1 delta E29 mice.
Project description:MBNL1 is a known splicing factor and is related to Myotonic Dystrophy (DM). This study examines the tissue specific splicing patterns of MBNL1 using a mutant and wild type mouse across three tissues (heart,brain,quadricep) related publications: Aberrant alternative splicing and extracellular matrix gene expression in mouse models of myotonic dystrophy. Du H, etal Nat Struct Mol Biol. 2010 Feb;17(2):187-93. and Hum Mol Genet. 2006 Jul 1;15(13):2087-97. Failure of MBNL1-dependent post-natal splicing transitions in myotonic dystrophy. Lin X, Miller JW, Mankodi A, Kanadia RN, Yuan Y, Moxley RT, Swanson MS, Thornton CA. We examined quadricep,heart and brain of a mouse MBNL1 mutant to test whether MBNL mutants creates a tissue specific splicing defect. These samples were compared to the tissues of a wild type mouse.
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.