Project description:The role of SRF in the regulation of microRNA expression and microRNA biogenesis in cardiac hypertrophy has not been well established. In this report, we employed a distinct transgenic mouse model to study the impact of SRF on cardiac microRNA expression and microRNA biogenesis. Cardiac-specific overexpression of SRF (SRF-Tg) led to altered expression of a number of microRNAs.
Project description:The role of SRF in the regulation of microRNA expression and microRNA biogenesis in cardiac hypertrophy has not been well established. In this report, we employed a distinct transgenic mouse model to study the impact of SRF on cardiac microRNA expression and microRNA biogenesis. Cardiac-specific overexpression of SRF (SRF-Tg) led to altered expression of a number of microRNAs. To study the effect of SRF level on cardiac gene expression and function in the mouse heart, we employed the cardiac-specific transgenic approach to increase the SRF protein level in one mouse model. The ventricular tissue samples used for the microRNA array analysis were obtained from 6-month-old wild-type mice and age-matched SRF-Tg mice. The RNA sample isolation and microRNA array were performed in triplets for both wild-type and transgenic mice.
Project description: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. Six to eight years old wildtype and JMJD2A heart specific transgnic mice were undergone either sham or TAC surgery. After 3 weeks, mice were sarcirificed to harvest heart. RNA was extracted from heart samples and treated with DNase, followed by biotin-labeling and microarray hybridization.
Project description: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.
Project description:To identify in vivo new cardiac SRF target genes and to study the response of these novel genes to SRF overexpression, we employed a cardiac-specific, transgenic mouse model that has a phenotype in young adulthood which resembles that of the typically aged heart. Using this “cardiac aging” model, we identified 207 genes that are important to cardiac function that were differentially expressed in vivo. Among them, 192 genes had SRF binding motifs (56 with CArG and 136 with CArG-like elements) in their promoter region. Fifty-one of 56 genes with classic CArG elements were not previously reported. These SRF target genes were grouped into 12 categories based on their function. It was observed that genes associated with cardiac energy metabolism shifted toward that of carbohydrate metabolism and away from that of fatty acid metabolism. The expression of genes that are involved in transcription and ion regulation were decreased, but expression of cytoskeletal genes were significantly increased. Using public databases of mouse models of stress, we also found that altered expression of the SRF target genes occurred in these hearts as well. Thus, SRF target genes are actively regulated under various physiological and pathological conditions, including hemodynamic stress. The mild elevation of SRF protein in the rodent heart that is observed during typical adult aging may have a major impact on many SRF target genes, thereby affecting cardiac structure and performance. In addition, these results could help to enhance our understanding of SRF regulation of cellular processes, including metabolic and cytoskeletal function. The generation and characterization of transgenic mice with mild cardiac-specific overexpression of SRF was previously reported (Zhang et al., 2003). At 6 months of age, the transgenic mice manifested cardiac changes suggestive of an “aged heart” (Zhang et al., 2003). Therefore, 6-month-old transgenic and non-transgenic mice were used in this study. Cardiac gene expression in SRF Tg heart was compared to that of wild-type mice.
Project description:Numerous studies found intestinal microbiota alterations which are thought to affect the development of various diseases through the production of gut-derived metabolites. However, the specific metabolites and their pathophysiological contribution to cardiac hypertrophy or heart failure progression still remain unclear. N,N,N-trimethyl-5-aminovaleric acid (TMAVA), derived from trimethyllysine through the gut microbiota, was elevated with gradually increased risk of cardiac mortality and transplantation in a prospective heart failure cohort (n=1647). TMAVA treatment aggravated cardiac hypertrophy and dysfunction in high-fat diet-fed mice. Decreased fatty acid oxidation (FAO) is a hallmark of metabolic reprogramming in the diseased heart and contributes to impaired myocardial energetics and contractile dysfunction. Proteomics uncovered that TMAVA disturbed cardiac energy metabolism, leading to inhibition of FAO and myocardial lipid accumulation. TMAVA treatment altered mitochondrial ultrastructure, respiration and FAO and inhibited carnitine metabolism. Mice with γ-butyrobetaine hydroxylase (BBOX) deficiency displayed a similar cardiac hypertrophy phenotype, indicating that TMAVA functions through BBOX. Finally, exogenous carnitine supplementation reversed TMAVA induced cardiac hypertrophy. These data suggest that the gut microbiota-derived TMAVA is a key determinant for the development of cardiac hypertrophy through inhibition of carnitine synthesis and subsequent FAO.
Project description:MicroRNAs (miRNAs) are important regulators in the process of cardiac hypertrophy and heart failure. Previous studies showed that miR-199a is upregulated in pressure-overload cardiac hypertrophy and overexpression of miR-199a induces cardiac hypertrophy in vivo. However, the therapeutic role of anti-miR-199a treatment in cardiac hypertrophy is of little known. Here, we showed a novel and effective way to treat mice cardiac hypertrophy and restored cardiac function through injection of adeno-associated virus (AAV) which expressed anti-miR-199a tough decoys (TuDs). We performed the RNA-seq profiling in both AAV9-EGFP control and AAV9-anti-miR-199a TuDs injected cardiac hypertrophic mice. The transcriptome analysis indicates that genes related to cytoplasmic translation, mitochondrial respiratory chain complex assembly were upregulated by anti-miR-199a treated recovered hearts.
Project description:To identify in vivo new cardiac SRF target genes and to study the response of these novel genes to SRF overexpression, we employed a cardiac-specific, transgenic mouse model that has a phenotype in young adulthood which resembles that of the typically aged heart. Using this “cardiac aging” model, we identified 207 genes that are important to cardiac function that were differentially expressed in vivo. Among them, 192 genes had SRF binding motifs (56 with CArG and 136 with CArG-like elements) in their promoter region. Fifty-one of 56 genes with classic CArG elements were not previously reported. These SRF target genes were grouped into 12 categories based on their function. It was observed that genes associated with cardiac energy metabolism shifted toward that of carbohydrate metabolism and away from that of fatty acid metabolism. The expression of genes that are involved in transcription and ion regulation were decreased, but expression of cytoskeletal genes were significantly increased. Using public databases of mouse models of stress, we also found that altered expression of the SRF target genes occurred in these hearts as well. Thus, SRF target genes are actively regulated under various physiological and pathological conditions, including hemodynamic stress. The mild elevation of SRF protein in the rodent heart that is observed during typical adult aging may have a major impact on many SRF target genes, thereby affecting cardiac structure and performance. In addition, these results could help to enhance our understanding of SRF regulation of cellular processes, including metabolic and cytoskeletal function. The generation and characterization of transgenic mice with mild cardiac-specific overexpression of SRF was previously reported (Zhang et al., 2003). At 6 months of age, the transgenic mice manifested cardiac changes suggestive of an “aged heart” (Zhang et al., 2003). Therefore, 6-month-old transgenic and non-transgenic mice were used in this study.
Project description:To explore the role of miR-22 in the heart, we generated miR-22 null and transgenic mice. Cardiac transgenic overexpression of miR-22 in vivo led to cardiac hypertrophy that evolved into progressive dilated cardiomyopathy (DCM) in unstressed hearts. We found that miR-22 directly regulates two transcriptional antagonists, purine rich element binding protein B (PURB), a repressor, and serum response factor (SRF), an activator, in the heart. Through these gain- and loss-of-function experiments in mice, we suggest that a primary function of miR-22 is to fine tune the relative expression and activity of these two transcriptional antagonists to influence contractile gene expression, function, growth and adaptation of the heart to stress.