My recent study identified Serum response factor (SRF), an obligatory cardiogenic transcription factor, as a prominent caspase-3 target in human failing hearts. SRF cleavage led to the generation of a dominant negative inhibitor, SRF-N (N-terminus of SRF). This novel discovery is provocative, and raises the question of potential pathogenic role of SRF-N in cardiac dysfunction. To address this question, I generated multiple independent lines of transgenic mice that expressed SRF-N specifically in the heart. Mice with high expression level of SRF-N developed a dilated, hypertrophic cardiomyopathy and eventually died of heart failure. This provides a mouse model that mimics the progression of human heart disease. Microarray and quantitative PCR (Q-PCR) analyses revealed a significant downregulation of miR-133a and miR-1 in the SRF-N transgenic hearts, which coincided with overt upregulation of Mef2a, CaM and NFATc4. Together with recent discovery of RhoA and Cdc42 as miR-133a targets, we believe that the dysregulation of miR-133a and miR-1 and the consequent upregulation of a group of hypertrophy-associated genes may constitute one of the potential mechanisms contributing to SRF-N-mediated cardiomyopathy. These preliminary results underpin the application's central hypothesis that the dominant negative SRF-N directs the onset of cardiomyopathy and facilitates the progression to overt heart failure through the downregulation of miR-133a and miR-1 gene.
Three aims are proposed.
Aim I is to characterize the transgenic mouse phenotype. The transgenic mice will be assessed by comprehensive studies including functional, morphological and molecular assessments.
Aim II and III are to elucidate the molecular mechanism of SRF-N-mediated cardiomyopathy. Dysregulation of the two cardiac microRNAs will be assessed. A group of miR-133a and miR-1 regulated target genes will be evaluated. Two new enhancers directed for miR-133a expression and one new target for miR-133a will be verified. Rescue experiments will be conducted to test if the introduction of miR-133a and -1 could correct/rescue the murine heart phenotype. The ultimate outcome of the application will be to establish a direct link between the dominant negative SRF-N and the development of heart failure. The novelty includes 1) the demonstration of SRF-N-mediated cardiomyopathy in intact heart;2) the identification of two SRF-dependent enhancers regulating miR-133a expression;and 3) the elucidation of the molecular mechanism directing disease progression.

Public Health Relevance

The study is focused on the mechanistic view of dominant negative cardiogenic transcription factor SRF-N (N-terminus of serum response factor) in propelling heart failure.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21HL094844-01A2
Application #
7896947
Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
Program Officer
Adhikari, Bishow B
Project Start
2010-04-15
Project End
2012-03-31
Budget Start
2010-04-15
Budget End
2011-03-31
Support Year
1
Fiscal Year
2010
Total Cost
$146,500
Indirect Cost
Name
Texas A&M University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
835607441
City
College Station
State
TX
Country
United States
Zip Code
77845
Yang, Xiangsheng; Wang, Tiannan; Lin, Xi et al. (2015) Genetic deletion of Rnd3/RhoE results in mouse heart calcium leakage through upregulation of protein kinase A signaling. Circ Res 116:e1-e10
Jie, Wei; Andrade, Kelsey C; Lin, Xi et al. (2015) Pathophysiological Functions of Rnd3/RhoE. Compr Physiol 6:169-86
Yue, X; Yang, X; Lin, X et al. (2014) Rnd3 haploinsufficient mice are predisposed to hemodynamic stress and develop apoptotic cardiomyopathy with heart failure. Cell Death Dis 5:e1284
Li, Qi; Guo, Junli; Lin, Xi et al. (2013) An intragenic SRF-dependent regulatory motif directs cardiac-specific microRNA-1-1/133a-2 expression. PLoS One 8:e75470
Lin, Xi; Liu, Baohui; Yang, Xiangsheng et al. (2013) Genetic deletion of Rnd3 results in aqueductal stenosis leading to hydrocephalus through up-regulation of Notch signaling. Proc Natl Acad Sci U S A 110:8236-41
Wong, Jerry; Zhang, Jingchun; Yanagawa, Bobby et al. (2012) Cleavage of serum response factor mediated by enteroviral protease 2A contributes to impaired cardiac function. Cell Res 22:360-71
Zhang, Xiaowei; Wang, Xiaohong; Zhu, Hongyan et al. (2012) Hsp20 functions as a novel cardiokine in promoting angiogenesis via activation of VEGFR2. PLoS One 7:e32765
Lin, Xi; Yang, Xiangsheng; Li, Qi et al. (2012) Protein tyrosine phosphatase-like A regulates myoblast proliferation and differentiation through MyoG and the cell cycling signaling pathway. Mol Cell Biol 32:297-308
Zhou, Cissy Chenyi; Chang, Jiang; Mi, Tiejuan et al. (2012) Targeted expression of Cre recombinase provokes placental-specific DNA recombination in transgenic mice. PLoS One 7:e29236
Kim, Eun Young; Chen, Li; Ma, Yanlin et al. (2012) Enhanced desumoylation in murine hearts by overexpressed SENP2 leads to congenital heart defects and cardiac dysfunction. J Mol Cell Cardiol 52:638-49

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