Transcription factor CHF1/Hey2 regulates EC coupling and heart failure in mice through regulation of FKBP12.6.
ABSTRACT Heart failure is a leading cause of morbidity and mortality in Western society. The cardiovascular transcription factor CHF1/Hey2 has been linked to experimental heart failure in mice, but the mechanisms by which it regulates myocardial function remain incompletely understood. The objective of this study was to determine how CHF1/Hey2 affects development of heart failure through examination of contractility in a myocardial knockout mouse model. We generated myocardial-specific knockout mice. At baseline, cardiac function was normal, but, after aortic banding, the conditional knockout mice demonstrated a greater increase in ventricular weight-to-body weight ratio compared with control mice (5.526 vs. 4.664 mg/g) and a significantly decreased ejection fraction (47.8 vs. 72.0% control). Isolated cardiac myocytes from these mice showed decreased calcium transients and fractional shortening after electrical stimulation. To determine the molecular basis for these alterations in excitation-contraction coupling, we first measured total sarcoplasmic reticulum calcium stores and calcium-dependent force generation in isolated muscle fibers, which were normal, suggesting a defect in calcium cycling. Analysis of gene expression demonstrated normal expression of most genes known to be involved in myocardial calcium cycling, with the exception of the ryanodine receptor binding protein FKBP12.6, which was expressed at increased levels in the conditional knockout hearts. Treatment of the isolated knockout myocytes with FK506, which inhibits the association of FKBP12.6 with the ryanodine receptor, restored contractile function. These findings demonstrate that conditional deletion of CHF1/Hey2 in the myocardium leads to abnormalities in calcium handling mediated by FKBP12.6 that predispose to pressure overload-induced heart failure.
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ABSTRACT: Strong associations have been observed between exposure to fine ambient particulate matter (PM2.5) and adverse cardiovascular outcomes. In particular, exposure to traffic related PM2.5 has been associated with increases in left ventricular hypertrophy, a strong risk factor for cardiovascular mortality. As much of traffic related PM2.5 is derived from diesel exhaust (DE), we investigated the effects of chronic DE exposure on cardiac hypertrophy and heart failure in the adult mouse by exposing mice to DE combined with either of two mouse models of cardiac hypertrophy: angiotensin II infusion or pressure overload induced by transverse aortic banding. Wild type male C57BL/6 J mice were either infused with angiotensin II (800 ng/kg/min) via osmotic minipump implanted subcutaneously for 1 month, or underwent transverse aortic banding (27 gauge needle 1 week for observing acute reactions, 26 gauge needle 3 months or 6 months for observing chronic reactions). Vehicle (saline) infusion or sham surgery was used as a control. Shortly after surgery, mice were transferred to our exposure facility and randomly assigned to either diesel exhaust (300 or 400 mug/m3) or filtered air exposures. After reaching the end of designated time points, echocardiography was performed to measure heart structure and function. Gravimetric analysis was used to measure the ventricular weight to body weight ratio. We also measured heart rate by telemetry using implanted ambulatory ECG monitors. Both angiotensin II and transverse aortic banding promoted cardiac hypertrophy compared to vehicle or sham controls. Transverse aortic banding for six months also promoted heart failure in addition to cardiac hypertrophy. In all cases, DE failed to exacerbate the development of hypertrophy or heart failure when compared to filtered air controls. Prolonged DE exposure also led to a decrease in average heart rate. Up to 6-months of DE exposure had no effect on cardiac hypertrophy and heart function induced by angiotensin II stimulation or pressure overload in adult C57BL/6 J mice. This study highlights the potential importance of particle constituents of ambient PM2.5 to elicit cardiotoxic effects. Further investigations on particle constituents and cardiotoxicity are warranted.Particle and Fibre Toxicology 10/2013; 10(1):49. · 9.18 Impact Factor
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ABSTRACT: CHF1/Hey2 is a Notch-responsive basic helix-loop-helix transcription factor involved in cardiac development. Common variants in Hey2 are associated with Brugada syndrome. We hypothesized that absence of CHF1/Hey2 would result in abnormal cellular electrical activity, altered cardiac conduction system (CCS) development, and increased arrhythmogenesis. We isolated neonatal CHF/Hey2-knockout (KO) cardiac myocytes and measured action potentials and ion channel subunit gene expression. We also crossed myocardial-specific CHF1/Hey2-KO mice with cardiac conduction system LacZ reporter mice and stained for conduction system tissue. We also performed ambulatory ECG monitoring for arrhythmias and heart rate variability. Neonatal cardiomyocytes from CHF1/Hey2-KO mice demonstrate a 50% reduction in action potential dV/dT, a 50-75% reduction in SCN5A, KCNJ2, and CACNA1C ion channel subunit gene expression, and an increase in delayed afterdepolarizations from 0/min to 12/min. CHF1/Hey2 cKO CCS-lacZ mice have a ∼3-fold increase in amount of CCS tissue. Ambulatory ECG monitoring showed no difference in cardiac conduction, arrhythmias, or heart rate variability. Wild-type cells or animals were used in all experiments. CHF1/Hey2 may contribute to Brugada syndrome by influencing the expression of SCN5A and formation of the cardiac conduction system, but its absence does not cause baseline conduction defects or arrhythmias in the adult mouse.-Hartman, M. E., Liu, Y., Zhu, W.-Z., Chien, W.-M., Weldy, C. S., Fishman, G. I., Laflamme, M. A., Chin, M. T. Myocardial deletion of transcription factor CHF1/Hey2 results in altered myocyte action potential and mild conduction system expansion but does not alter conduction system function or promote spontaneous arrhythmias.The FASEB Journal 03/2014; · 5.70 Impact Factor
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ABSTRACT: The Cre-loxP recombination system has been used to promote DNA recombination both in vitro and in vivo. For in vivo delivery, Cre expression is commonly achieved through the use of tissue/cell type-specific promoters, viral infection, or drug inducible transcription and protein translocation to promote targeted DNA excision. The development of cell permeable (or penetrating) peptide tagged proteins has facilitated the delivery of Cre recombinase protein into cells in culture, organotypic slide culture, or in living animals. In this report, we generated bacterially expressed, his-tagged Cre protein with either a cardiac targeting peptide (CTP) or an antennapedia peptide (ANTP) at the C-terminus and demonstrated efficient uptake and recombination in both cell culture and mice. To facilitate delivery to cardiac and skeletal muscle, we mixed proteins with pluronic F-127 hydrogel and delivered Cre protein into reporter Rosa26mTmG mouse skeletal muscle or Rosa26LacZ cardiac muscle via ultrasound guided injection. Activation of reporter gene expression indicated that these Cre proteins were enzymatically active. Recombination events were detected only in the vicinity of injection areas. In conclusion, we have developed a method to deliver enzymatically active Cre protein locally to skeletal muscle and cardiac muscle that may be adapted for use with other proteins. © 2014 Wiley Periodicals, Inc.genesis 04/2014; · 2.58 Impact Factor