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Microarray analysis of heart gene expression in wild type and JMJD2A heart specific transgenic mice after sham and thoracic aortic constriction surgery

ABSTRACT: Cardiac hypertrophy and failure are accompanied by a reprogramming of gene expression that involves transcription factors and chromatin remodeling enzymes. Little is known about the role of histone methylation and demethylation in this process. To understand the role of JMJD2A, a trimethyl demethylase for histone 3 lysine 9 and 36, in cardiac hypertrophy, we generated heart specific JMJD2A deletion (JMJD2A hKO) and overexpression (JMJD2A-Tg) mouse lines. JMJD2A hKO and JMJD2A-Tg mice are viable and have no overt baseline phenotype. However, they have altered responses to cardiac stresses. While inactivation of JMJD2A in hKO mice resulted in an attenuated hypertrophic response to transverse aortic constriction (TAC)-induced pressure overload compared to that of control littermates, JMJD2A-Tg mice have exacerbated cardiac hypertrophy after TAC. We identified four-and-a-half LIM domains 1 (FHL1) as a novel target of JMJD2A. JMJD2A binds to the FHL1 promoter in response to TAC and upregulates the expression of FHL1. Binding of JMJD2A to the FHL1 promoter is associated with downregulation of trimethylated H3K9. Upregulation of FHL1 by JMJD2A is mediated through SRF and myocardin, and requires its demethylase activity. The expression of JMJD2A is upregulated in human hypertrophic cardiomyopathy patients. Our studies reveal that JMJD2A promotes cardiac hypertrophy by synergistically upregulating SRF/myocardin-targeted genes and suggest a novel mechanism of reprogramming of gene expression involved in cardiac hypertrophy.

ORGANISM(S): Mus musculus

PROVIDER: GSE27689 | GEO | 2011/06/02

SECONDARY ACCESSION(S): PRJNA138145

REPOSITORIES: GEO

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Project description:Aims: Cardiac hypertrophy is a compensatory response to pressure overload, leading to heart failure. Recent studies have demonstrated that Rho is immediately activated in left ventricles after pressure overload, and that Rho signaling plays crucial regulatory roles in actin cytoskeleton rearrangement during cardiac hypertrophic responses. However, the mechanisms by which Rho and its downstream proteins control actin dynamics during hypertrophic responses remain not fully understood. In this study, we identified the pivotal roles of mammalian homologue of Drosophila diaphanous (mDia) 1, a Rho-effector molecule, in pressure overload-induced ventricular hypertrophy. Methods and Results: Male wild-type (WT) and mDia1-knockout (mDia1KO) mice (10–12 weeks old) were subjected to a transverse aortic constriction (TAC) or sham operation. The heart weight/tibia length ratio, cardiomyocyte cross-sectional area, left ventricular wall thickness, and expression of hypertrophy-specific genes were significantly decreased in mDia1KO mice 3 weeks after TAC, and the mortality rate was higher at 12 weeks. Echocardiography indicated that mDia1 deletion increased the severity of heart failure 8 weeks after TAC. Importantly, we could not observe apparent defects in cardiac hypertrophic responses in mDia3-knockout mice. Microarray analysis revealed that mDia1 was involved in the induction of hypertrophy related genes, including immediate early genes (IEGs), in pressure overloaded hearts. Loss of mDia1 attenuated activation of the mechanotransduction pathway in TAC-operated mice hearts. We also found that mDia1 was involved in stretch-induced activation of the mechanotransduction pathway and gene expression of c-fos in neonatal rat ventricular cardiomyocytes (NRVMs). mDia1 regulated the F/G-actin ratio in response to pressure overload in mice. Additionally, increases in nuclear myocardin-related transcription factors (MRTFs) and serum response factor (SRF) were perturbed in response to pressure overload in mDia1KO mice and to mechanical stretch in mDia1 depleted NRVMs. Conclusions: mDia1, through actin dynamics, is involved in compensatory cardiac hypertrophy in response to pressure overload.

Project description:Muscle ring finger-1 (MuRF1) is a muscle-specific protein implicated in the regulation of cardiac myocyte size and contractility. MuRF2, a closely related family member, redundantly interacts with protein substrates, and hetero-dimerizes with MuRF1. Mice lacking either MuRF1 or MuRF2 are phenotypically normal whereas mice lacking both proteins develop a spontaneous cardiac and skeletal muscle hypertrophy indicating cooperative control of muscle mass by MuRF1 and MuRF2. In order to identify the role that MuRF1 plays in regulating cardiac hypertrophy in vivo, we created transgenic mice expressing increased amounts of cardiac MuRF1. Adult MuRF1 transgenic (Tg+) hearts exhibited a non-progressive thinning of the left ventricular wall and a concomitant decrease in cardiac function. Experimental induction of cardiac hypertrophy by trans-aortic constriction (TAC) induced rapid failure of MuRF1 Tg+ hearts. Microarray analysis identified that the levels of genes associated with metabolism (and in particular mitochondrial processes) were significantly altered in MuRF1 Tg+ hearts, both at baseline and during the development of cardiac hypertrophy. Surprisingly, ATP levels in MuRF1 Tg+ mice did not differ from wild type mice despite the depressed contractility following TAC. To explain this discrepancy between the ongoing heart failure and maintained ATP levels in MuRF1 Tg+ hearts, we compared the level and activity of creatine kinase (CK) between wild type and MuRF1 Tg+ hearts. Although mCK and CK-M/B protein levels were unaffected in MuRF1 Tg+ hearts, total CK activity was significantly inhibited. We conclude that MuRF1’s inhibition of CK activity leads to increased susceptibility to heart failure following TAC, demonstrating for the first time that MuRF1 regulates cardiac energetics in vivo. Keywords: Genetic modification, physiological manipulation. Three-condition experiment, MuRF1 Tg+ vs. WT mice. Biological replicates: 4 WT baseline, 3 MuRF1 Tg+ baseline, cardiac overpressure hypertrophy induced by trans-aortic banding at 1 week (3 WT, 3 MurF Tg) and 4 weeks (3 WT, 3 MurF Tg), hearts harvested. One replicate per array.

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Microarray analysis of heart gene expression in wild type and JMJD2A heart specific transgenic mice after sham and thoracic aortic constriction surgery

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