Myotonic dystrophy (type 1) (DM1) is the most prevalent form of muscular dystrophy in adults and is caused by a CTG expansion in the 3' untranslated region of the DMPK gene. Pathogenesis in DM1 is due to a gain of function of the DMPK mRNA that contains expanded CUG repeats (CUGexp RNA). The CUGexp RNA alters the functions of RNA binding proteins such as members of the muscleblind like (MBNL) and CUGBP, Elav-like family (CELF) families. MBNL1 is sequestered on the expanded CUG repeats producing a loss of function while CELF1 is up regulated due to activation of protein kinase C (PKC) leading to its phosphorylation and stabilization. While much has been learned regarding the molecular consequences of CUGexp RNA expression, the mechanisms by which CUGexp RNA causes progressive muscle wasting remains unknown. To study the pathogenic mechanism in muscle, we developed a muscle specific tetracycline inducible transgenic mouse model expressing the last 1200 nucleotides of the DMPK mRNA containing 960 CUG repeats. Animals induced to express the CUGexp RNA develop progressive and severe histopathology and muscle wasting. We will use this model to determine the role of age in disease progression and identify the features of chronic wasting that do and do not regress upon removal of the CUGexp RNA. We will use genetic approaches in the mouse model to determine whether the loss of CELF1 or gain of MBNL1 and/or MBNL2 prevents or rescues the muscle phenotype. We will determine whether the PKC pathway is activated in DM1 skeletal muscle, as has been shown in DM1 heart, and whether PKC inhibition rescues the muscle phenotype. RNA-seq data from muscle of DM1 mouse models and DM1 muscle samples will be used to identify and then test the roles of critical aberrant gene expression and alternative splicing events in muscle pathology. We will also perform studies to identify CELF/MBNL-independent mechanisms of muscle pathology. The goal of this study is to develop an understanding of the molecular mechanisms by which CUGexp RNA leads to progressive muscle loss and thereby increase the number of potential therapeutic targets.
Myotonic dystrophy is the most common cause of adult onset muscular dystrophy and sixty percent of affected individuals die from chronic muscle wasting. This proposal studies the mechanisms responsible for muscle wasting in myotonic dystrophy type 1, the more common form of the disease in the US. The results are likely to provide information to develop new therapeutic approaches as well as augment therapeutic approaches being developed.
|Blue, R Eric; Koushik, Amrita; Engels, Nichlas M et al. (2018) Modulation of alternative splicing of trafficking genes by genome editing reveals functional consequences in muscle biology. Int J Biochem Cell Biol 105:134-143|
|Morriss, Ginny R; Rajapakshe, Kimal; Huang, Shixia et al. (2018) Mechanisms of skeletal muscle wasting in a mouse model for myotonic dystrophy type 1. Hum Mol Genet 27:2789-2804|
|Singh, Ravi K; Kolonin, Arseniy M; Fiorotto, Marta L et al. (2018) Rbfox-Splicing Factors Maintain Skeletal Muscle Mass by Regulating Calpain3 and Proteostasis. Cell Rep 24:197-208|
|Brinegar, Amy E; Xia, Zheng; Loehr, James Anthony et al. (2017) Extensive alternative splicing transitions during postnatal skeletal muscle development are required for calcium handling functions. Elife 6:|
|Manning, Kassie S; Rao, Ashish N; Castro, Miguel et al. (2017) BNANC Gapmers Revert Splicing and Reduce RNA Foci with Low Toxicity in Myotonic Dystrophy Cells. ACS Chem Biol 12:2503-2509|
|Sharpe, Joshua J; Cooper, Thomas A (2017) Unexpected consequences: exon skipping caused by CRISPR-generated mutations. Genome Biol 18:109|
|Morriss, Ginny R; Cooper, Thomas A (2017) Protein sequestration as a normal function of long noncoding RNAs and a pathogenic mechanism of RNAs containing nucleotide repeat expansions. Hum Genet 136:1247-1263|
|Manning, Kassie S; Cooper, Thomas A (2017) The roles of RNA processing in translating genotype to phenotype. Nat Rev Mol Cell Biol 18:102-114|
|Cox, Diana C; Cooper, Thomas A (2016) Non-canonical RAN Translation of CGG Repeats Has Canonical Requirements. Mol Cell 62:155-156|
|Giudice, Jimena; Loehr, James A; Rodney, George G et al. (2016) Alternative Splicing of Four Trafficking Genes Regulates Myofiber Structure and Skeletal Muscle Physiology. Cell Rep 17:1923-1933|
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