Myotonic dystrophy (DM) is an autosomal dominant disorder affecting 1 in 8500 people worldwide. Individuals with DM exhibit progressive muscular dystrophy, arrhythmias and CNS damage. Mutations are expanded CTG or CCTG repeats in untranslated regions of DMPK and ZNF9 genes respectively. The expanded repeats are expressed as CUG (DM1) or CCUG (DM2) repeat RNA, which accumulate as discrete foci in nuclei. The pathogenesis of DM1 involves misregulation of alternative splicing resulting in expression of inappropriate protein isoforms causing specific symptoms. However, the mechanism by which expanded repeats alter pre-mRNA alternative splicing is unclear. Two RNA binding proteins have been implicated in DM1 pathogenesis: MBNL1 and CUG-BP1. CUG-BP1 regulates alternative splicing of cardiac troponin T (cTNT), insulin receptor (IR) and chloride channel (CIC-1) pre-mRNAs that are mis-spliced in DM1 striated muscle. The functional consequences of mis-splicing of CIC-1 and IR directly correlate with myotonia and insulin resistance, respectively, observed in DM1. The splicing patterns observed for these pre-mRNAs are consistent with increased CUG-BP1 activity observed in DM1 striated muscle. MBNL proteins bind and colocalize with the foci of expanded CUG repeat RNA in DM1 cells. MBNL proteins directly regulate splicing of cTNT and IR alternative exons. Therefore, MBNL1 and CUG-BP1 proteins are the major regulators of alternative splicing of pre-mRNAs that are misregulated in DM1. The goal of this proposal is to understand how expanded CUG repeat RNA disrupts the regulation by CUG-BP1 and MBNL1. In this study I will: i) establish and characterize stable cell lines which inducibly express CUG repeat RNA, ii) characterize the effects of CUG repeat RNA on steady state levels and nuclearcytoplasmic distribution of CUG-BP1 and MBNL1, iii) determine whether CUG repeat RNA affects post-translational modifications of CUG-BP1 and MBNL1 and characterize the significance of these modifications on alternative splicing.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
5F32AR052630-03
Application #
7215638
Study Section
Special Emphasis Panel (ZRG1-F08 (20))
Program Officer
Boyce, Amanda T
Project Start
2005-04-01
Project End
2008-03-31
Budget Start
2007-04-01
Budget End
2008-03-31
Support Year
3
Fiscal Year
2007
Total Cost
$50,428
Indirect Cost
Name
Baylor College of Medicine
Department
Pathology
Type
Schools of Medicine
DUNS #
051113330
City
Houston
State
TX
Country
United States
Zip Code
77030
Wang, Guey-Shin; Kuyumcu-Martinez, Muge N; Sarma, Satyam et al. (2009) PKC inhibition ameliorates the cardiac phenotype in a mouse model of myotonic dystrophy type 1. J Clin Invest 119:3797-806
Kuyumcu-Martinez, N Muge; Wang, Guey-Shin; Cooper, Thomas A (2007) Increased steady-state levels of CUGBP1 in myotonic dystrophy 1 are due to PKC-mediated hyperphosphorylation. Mol Cell 28:68-78