Myotonic dystrophy (DM) is the second most common cause of muscular dystrophy and the most common cause of adult onset muscular dystrophy. The disease is dominantly inherited, multisystemic, and phenotypically variable. The mutations that cause DM are expanded tri- (CTG) and tetra- (CCTG) nucleotide repeats located within untranslated regions of transcribed genes. Pathogenesis involves a novel mechanism in which RNA transcribed from the expanded allele exerts a toxic gain-of-function. Recent evidence indicates that an RNA gain-of-function is an important component of other microsatellite expansion disorders such as Spinocerebellar Ataxia 8 (SCA8), Fragile X-associated Tremor/Ataxia Syndrome (FXTAS), and Huntington Disease-Like 2 (HDL2). One mechanism by which the expanded repeat RNA exerts a gain-of-function in DM is by sequestration of RNA binding proteins such as the muscleblind-like (MBNL) family, resulting in a loss-of-function. We have identified a second mechanism in which expanded repeat RNA activates protein kinase C (PKC) and induces PKC-dependent phosphorylation of a second RNA binding protein, CUG-binding protein 1 (CUGBP1), resulting in its stabilization and up-regulation. MBNL and CUGBP1 normally regulate pre-mRNA alternative splicing during development and the disruption of their functions in DM results in the splicing defects that have previously been linked with causation of disease symptoms. The finding that RNA from a microsatellite expansion induces a signaling event has broad implications to the mechanism of pathogenesis. The goals of this proposal are to determine the mechanism by which expanded repeat RNA activates a signaling event, investigate the immediate effects on CUGBP1 function, determine the broader consequences, and relate these effects of the expanded repeats to mechanisms of inhibited skeletal muscle differentiation in cell culture and wasting of skeletal muscle tissue. The latter aspect of the investigation will be performed using a newly developed DM1 mouse model that reproduces features of the disease including severe skeletal muscle wasting. At the completion of these studies, we will have established the contributions to disease pathogenesis of a newly discovered signaling event stimulated by microsatellite-derived RNA. These results will provide new therapeutic targets to prevent or circumvent the molecular events leading to muscle wasting.

Public Health Relevance

Myotonic dystrophy is the second most common cause of muscular dystrophy in the United States. It is caused by an unusual kind of mutation and a previously unknown mechanism. We will use cell culture and mouse models of the to determine the mechanism of disease. This information will be used to develop therapeutic approaches to reverse or circumvent disease processes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR045653-14
Application #
8240552
Study Section
Special Emphasis Panel (ZRG1-MOSS-L (07))
Program Officer
Nuckolls, Glen H
Project Start
1999-02-08
Project End
2014-03-31
Budget Start
2012-04-01
Budget End
2013-03-31
Support Year
14
Fiscal Year
2012
Total Cost
$521,202
Indirect Cost
$181,657
Name
Baylor College of Medicine
Department
Pathology
Type
Schools of Medicine
DUNS #
051113330
City
Houston
State
TX
Country
United States
Zip Code
77030
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
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
Brinegar, Amy E; Cooper, Thomas A (2016) Roles for RNA-binding proteins in development and disease. Brain Res 1647:1-8

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