Novel Roles for the Transcriptional Repressor E4BP4 in Both Cardiac Physiology and Pathophysiology [4 mouse lines]

Circadian clocks temporally orchestrate biological processes critical for cellular/organ function. For example, the cardiomyocyte circadian clock modulates cardiac metabolism, signaling, and electrophysiology over the course of the day, such that, disruption of the clock leads to age-onset cardiomyopathy (through unknown mechanisms). Here, we report that genetic disruption of the cardiomyocyte clock results in chronic induction of the transcriptional repressor E4BP4. Importantly, E4BP4 deletion prevents age-onset cardiomyopathy following clock disruption. These studies also indicate that E4BP4 regulates both cardiac metabolism (eg, fatty acid oxidation) and electrophysiology (eg, QT interval). Collectively, these studies reveal that E4BP4 is a novel regulator of both cardiac physiology and pathophysiology. Comparative gene expression profiling analysis of RNA-seq data for biventricular heart tissue isolated from 4 mouse lines: 1) cardiomyocyte-specific Bmal1 knockout (CBK; Bmal1flox/flox/MHCalphaCre+/-) and littermate control (Bmal1flox/flox/MHCalphaCre-/-) mice; 2) cardiomyocyte-specific E4bp4 knockout (CEK; E4bp4flox/flox/MHCalphaCre+/-) and littermate control (E4bp4flox/flox/MHCalphaCre-/-) mice; 3) cardiomyocyte-specific Bmal1/E4bp4 double knockout (CBK/CEK; Bmal1flox/flox/E4bp4flox/flox/MHCalphaCre+/-) and littermate control (Bmal1flox/flox/E4bp4flox/flox/MHCalphaCre-/-) mice; and 4) Cre recombinase control (MHCalphaCre+/-) and littermate wild-type mice. Individual Bmal1flox/flox, E4bp4flox/flox, and MHCalphaCre+/- mouse lines昼夜节律时钟（circadian clocks）可时序性调控对细胞与器官功能至关重要的生物学过程。例如，心肌细胞昼夜节律时钟会在一日内调节心脏代谢、信号传导与电生理活动，该时钟的紊乱可通过未知机制引发老年起病型心肌病。本研究报道，心肌细胞时钟的遗传紊乱会持续性诱导转录抑制因子E4结合蛋白4（E4BP4）的表达。值得注意的是，敲除E4BP4可阻止时钟紊乱后出现的老年起病型心肌病。本研究同时表明，E4BP4可调控心脏代谢（如脂肪酸氧化）与电生理活动（如QT间期）。综上，本系列研究揭示E4BP4是心脏生理与病理生理过程的新型调控因子。本研究对从4种小鼠品系中分离得到的双心室心脏组织的RNA测序（RNA-seq）数据开展比较基因表达谱分析：1）心肌细胞特异性Bmal1敲除（CBK; Bmal1flox/flox/MHCalphaCre+/-）小鼠及其同窝对照（Bmal1flox/flox/MHCalphaCre-/-）小鼠；2）心肌细胞特异性E4bp4敲除（CEK; E4bp4flox/flox/MHCalphaCre+/-）小鼠及其同窝对照（E4bp4flox/flox/MHCalphaCre-/-）小鼠；3）心肌细胞特异性Bmal1/E4bp4双敲除（CBK/CEK; Bmal1flox/flox/E4bp4flox/flox/MHCalphaCre+/-）小鼠及其同窝对照（Bmal1flox/flox/E4bp4flox/flox/MHCalphaCre-/-）小鼠；以及4）Cre重组酶对照（MHCalphaCre+/-）小鼠及其同窝野生型小鼠。单独的Bmal1flox/flox、E4bp4flox/flox与MHCalphaCre+/-小鼠品系