Myotonic dystrophy (DM) is caused by the expansion of CTG and CCTG microsatellites in the non-coding regions of two different genes, DMPK and ZNF9/CNBP. Upon transcription, these repeat expansions fold into stable RNA hairpin structures that are toxic because they alter the activities of two families of alternative splicing factors, the muscleblind-like (MBNL) and CUGBP/ETR-3-like factor (CELF) proteins. Although this RNA-mediated pathogenesis model accounts for many aspects of adult-onset DM, the molecular events underlying congenital DM (CDM) are less clear since this form of the disease is only associated with very large CTG repeat expansions in the DMPK gene. While searching for factors involved in CDM pathogenesis, we discovered that Mbnl3 expression is restricted to embryonic muscle development and postnatal muscle regeneration. Based on these, and additional, results, this proposal is designed to test the hypothesis that Mbnl3 activity is essential for normal muscle development and regeneration and loss of this activity leads to delayed myogenesis in CDM followed by muscle weakness/wasting in adults. To test this hypothesis, Mbnl3 conditional knockout mice have been generated to test the effects of Mbnl3 loss on the development and regeneration of skeletal muscle. Additionally, RNA targets for Mbnl3 will be identified in both developing and regenerating muscle followed by assays designed to determine how loss of Mbnl3 leads to mis-regulation of these targets and specific pathological outcomes. Since we have discovered that Mbnl3 encodes both nuclear and cytoplasmic proteins, functional differences between these isoforms will be investigated and the hypothesis that MBNL proteins form different types of complexes on CUG versus CCUG expansion RNAs will be tested. Finally, we will generate Mbnl double and triple muscle-specific knockout mice to test our model that myotonic dystrophy is an MBNL loss-of-function disease. The goal of these studies is to understand the molecular events which lead to CDM and adult-onset DM and use this knowledge for the development of novel disease therapies.

Public Health Relevance

While myotonic dystrophy (DM) is the most common form of muscular dystrophy in adults, this disorder also affects newborn children. Our research is directed at understanding the disease-associated molecular events which lead to congenital and adult-onset DM. The study proposed in this grant is specifically focused on understanding how this disease affects the development and regeneration of skeletal muscle and this knowledge should allow us to develop novel therapeutic approaches for this disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR046799-15
Application #
8688744
Study Section
Special Emphasis Panel (ZRG1-MOSS-Q (02))
Program Officer
Nuckolls, Glen H
Project Start
2000-04-01
Project End
2015-06-30
Budget Start
2014-07-01
Budget End
2015-06-30
Support Year
15
Fiscal Year
2014
Total Cost
$304,528
Indirect Cost
$92,848
Name
University of Florida
Department
Genetics
Type
Schools of Medicine
DUNS #
969663814
City
Gainesville
State
FL
Country
United States
Zip Code
32611
Mohan, Apoorva; Goodwin, Marianne; Swanson, Maurice S (2014) RNA-protein interactions in unstable microsatellite diseases. Brain Res 1584:3-14
Batra, Ranjan; Charizanis, Konstantinos; Manchanda, Mini et al. (2014) Loss of MBNL leads to disruption of developmentally regulated alternative polyadenylation in RNA-mediated disease. Mol Cell 56:311-22
Goodwin, Marianne; Swanson, Maurice S (2014) RNA-binding protein misregulation in microsatellite expansion disorders. Adv Exp Med Biol 825:353-88
Hernandez-Hernandez, Oscar; Guiraud-Dogan, Celine; Sicot, Geraldine et al. (2013) Myotonic dystrophy CTG expansion affects synaptic vesicle proteins, neurotransmission and mouse behaviour. Brain 136:957-70
Xia, Guangbin; Santostefano, Katherine E; Goodwin, Marianne et al. (2013) Generation of neural cells from DM1 induced pluripotent stem cells as cellular model for the study of central nervous system neuropathogenesis. Cell Reprogram 15:166-77
Poulos, Michael G; Batra, Ranjan; Li, Moyi et al. (2013) Progressive impairment of muscle regeneration in muscleblind-like 3 isoform knockout mice. Hum Mol Genet 22:3547-58
Poulos, Michael G; Batra, Ranjan; Charizanis, Konstantinos et al. (2011) Developments in RNA splicing and disease. Cold Spring Harb Perspect Biol 3:a000778
Batra, Ranjan; Charizanis, Konstantinos; Swanson, Maurice S (2010) Partners in crime: bidirectional transcription in unstable microsatellite disease. Hum Mol Genet 19:R77-82
Du, Hongqing; Cline, Melissa S; Osborne, Robert J et al. (2010) Aberrant alternative splicing and extracellular matrix gene expression in mouse models of myotonic dystrophy. Nat Struct Mol Biol 17:187-93
Daughters, Randy S; Tuttle, Daniel L; Gao, Wangcai et al. (2009) RNA gain-of-function in spinocerebellar ataxia type 8. PLoS Genet 5:e1000600

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