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.

Public Health Relevance

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.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
2R01AR045653-16
Application #
8757225
Study Section
Skeletal Muscle and Exercise Physiology Study Section (SMEP)
Program Officer
Boyce, Amanda T
Project Start
1999-02-08
Project End
2019-08-31
Budget Start
2014-09-10
Budget End
2015-08-31
Support Year
16
Fiscal Year
2014
Total Cost
$424,377
Indirect Cost
$155,216
Name
Baylor College of Medicine
Department
Pathology
Type
Schools of Medicine
DUNS #
051113330
City
Houston
State
TX
Country
United States
Zip Code
77030
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Echeverria, Gloria V; Cooper, Thomas A (2014) Muscleblind-like 1 activates insulin receptor exon 11 inclusion by enhancing U2AF65 binding and splicing of the upstream intron. Nucleic Acids Res 42:1893-903
Giudice, Jimena; Xia, Zheng; Wang, Eric T et al. (2014) Alternative splicing regulates vesicular trafficking genes in cardiomyocytes during postnatal heart development. Nat Commun 5:3603
Gao, Zhihua; Cooper, Thomas A (2013) Reexpression of pyruvate kinase M2 in type 1 myofibers correlates with altered glucose metabolism in myotonic dystrophy. Proc Natl Acad Sci U S A 110:13570-5
Gao, Zhihua; Cooper, Thomas A (2013) Antisense oligonucleotides: rising stars in eliminating RNA toxicity in myotonic dystrophy. Hum Gene Ther 24:499-507
Lee, Johanna E; Bennett, C Frank; Cooper, Thomas A (2012) RNase H-mediated degradation of toxic RNA in myotonic dystrophy type 1. Proc Natl Acad Sci U S A 109:4221-6
Orengo, James P; Ward, Amanda J; Cooper, Thomas A (2011) Alternative splicing dysregulation secondary to skeletal muscle regeneration. Ann Neurol 69:681-90
Kalsotra, Auinash; Cooper, Thomas A (2011) Functional consequences of developmentally regulated alternative splicing. Nat Rev Genet 12:715-29
Ward, Amanda J; Rimer, Mendell; Killian, James M et al. (2010) CUGBP1 overexpression in mouse skeletal muscle reproduces features of myotonic dystrophy type 1. Hum Mol Genet 19:3614-22

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