Transcription profiling of mouse ERRalpha wild type vs. knockout hearts, baseline

We hypothesized that the estrogen-related receptor a (ERRa), which recruits PGC-1a to metabolic target genes in heart, exerts protective effects in the context of stressors known to cause heart failure. ERRa-/- mice subjected to left ventricular (LV) pressure overload developed signatures of heart failure including chamber dilatation and reduced LV fractional shortening. 31P-NMR studies revealed abnormal phosphocreatine depletion in ERRa-/- hearts subjected to hemodynamic stress, indicative of a defect in ATP reserve. Mitochondrial respiration studies demonstrated reduced maximal ATP synthesis rates in ERRa-/- hearts. Cardiac ERRa target genes involved in energy substrate oxidation, ATP synthesis, and phosphate transfer were downregulated in ERRa-/- mice at baseline or with pressure overload. These results demonstrate that ERRa, a potential therapeutic target, is indispensable for the adaptive bioenergetic response to hemodynamic stressors known to cause heart failure. Experiment Overall Design: Microarray analyses were performed with two samples each of ERRawt and ERRako to compare baseline changes in gene expression. Validation real-time PCR (n=7) was subsequently performed to characterize expression changes of gene targets identified in microarray and ChIP-chip studies in hearts of ERRa wt and KO mice at baseline and subjected to pressure overload stress.本研究提出如下假说：雌激素相关受体α（estrogen-related receptor α, ERRα）可将PGC-1α招募至心脏的代谢靶基因，在已知可诱发心力衰竭的应激因素作用下发挥保护作用。对ERRα敲除（ERRα-/-）小鼠施加左心室（left ventricular, LV）压力负荷后，其可出现心力衰竭相关表型，包括心室扩张及左心室短轴缩短率降低。31P核磁共振（31P-NMR）检测结果显示，暴露于血流动力学应激的ERRα-/-小鼠心脏中存在磷酸肌酸异常耗竭，提示三磷酸腺苷（ATP）储备存在缺陷。线粒体呼吸功能检测证实，ERRα-/-小鼠心脏的最大ATP合成速率显著降低。在基础状态或施加压力负荷后，ERRα-/-小鼠心脏中参与能量底物氧化、ATP合成及磷酸转运的ERRα靶基因表达均出现下调。上述结果表明，作为潜在治疗靶点的ERRα，对于已知可诱发心力衰竭的血流动力学应激的适应性生物能应答不可或缺。 实验整体设计：分别采集ERRα野生型（ERRαwt）与ERRα敲除型（ERRαko）小鼠心脏样本各2份，开展基因芯片分析，以比较基础状态下的基因表达差异。随后通过实时定量聚合酶链反应（real-time PCR, n=7）进行验证，以表征在基础状态及施加压力负荷应激后，ERRα野生型与敲除型小鼠心脏中，基因芯片及染色质免疫沉淀-芯片（chromatin immunoprecipitation-chip, ChIP-chip）所鉴定得到的靶基因的表达变化情况。