Investigation of a transgenic mouse model of familial dilated cardiomyopathy.
Investigation of a transgenic mouse model of familial dilated cardiomyopathy.
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DOI：
10.1016/j.yjmcc.2010.05.009
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发表时间：
2010-09
影响因子：
5
通讯作者：
Weihua Song;Emma C. Dyer;Daniel J Stuckey;M. Leung;M. Memo;C. Mansfield;M. Ferenczi;Ke Liu;C. Redwood;Kristen Nowak;S. Harding;K. Clarke;D. Wells;Steven B Marston
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文献类型：
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作者：
Weihua Song;Emma C. Dyer;Daniel J Stuckey;M. Leung;M. Memo;C. Mansfield;M. Ferenczi;Ke Liu;C. Redwood;Kristen Nowak;S. Harding;K. Clarke;D. Wells;Steven B Marston
我们研究了一种遗传性扩张型心肌病的转基因小鼠模型，该模型稳定表达ACTC E361 G突变，约占心脏总肌动蛋白的50%。从ACTC E361 G小鼠心脏中分离的F-肌动蛋白与天然人原肌球蛋白和肌钙蛋白掺入细丝中，并通过体外运动试验与NTG小鼠肌动蛋白进行比较。两组间滑动速度、运动肌丝分数及Ca ~（2+）敏感性无显著差异（EC_（50）E_（361）G/NTG=0.95±0.08）。ACTC E361 G小鼠皮肤小梁的Ca ~（2+）敏感性略高于NTG（EC_（50）E361 G/NTG=0.78±0.04）。当肌钙蛋白去磷酸化时，显示了分子表型;含E361 G的细丝的Ca 2+敏感性现在低于NTG（EC 50 E361 GdPTn/NTGdPTn=2.15±0.09）。我们通过比较磷酸化和去磷酸化细丝的钙敏感性，证明这是由于钙敏感性与肌钙蛋白I磷酸化解偶联所致。含NTG肌动蛋白的细丝EC_（50）native/dPTn=3.0±0.3，而含E_361G的细丝EC_（50）native/dPTn=1.04± 0.07。我们通过电影MRI、超声心动图和电导导管在4至18个月的时间内测量了心脏性能，发现NTG和ACTC E361 G小鼠在基础条件下的系统差异极小。然而，与NTG相比，ACTC E361 G小鼠在多巴酚丁胺治疗后室间隔增厚、射血分数、心率和心输出量的增加显著较少。我们认为ACTC E361 G突变使肌钙蛋白I磷酸化对肌丝Ca 2+敏感性不偶联，并减弱了对肾上腺素能刺激的反应，导致心脏储备减少，从而在应激下发生收缩功能障碍，导致扩张型心肌病。
We have investigated a transgenic mouse model of inherited dilated cardiomyopathy that stably expresses the ACTC E361G mutation at around 50% of total actin in the heart. F-actin isolated from ACTC E361G mouse hearts was incorporated into thin filaments with native human tropomyosin and troponin and compared with NTG mouse actin by in vitro motility assay. There was no significant difference in sliding speed, fraction of filaments motile or Ca2+-sensitivity (ratio EC50E361G/NTG=0.95±0.08). The Ca2+-sensitivity of force in skinned trabeculae from ACTC E361G mice was slightly higher than NTG (EC50E361G/NTG=0.78±0.04). The molecular phenotype was revealed when troponin was dephosphorylated; Ca2+-sensitivity of E361G-containing thin filaments was now lower than NTG (EC50E361GdPTn/NTGdPTn=2.15±0.09). We demonstrated that this was due to uncoupling of Ca2+-sensitivity from troponin I phosphorylation by comparing Ca2+-sensitivity of phosphorylated and dephosphorylated thin filaments. For NTG actin-containing thin filaments EC50native/dPTn=3.0±0.3 but for E361G-containing thin filaments EC50native/dPTn=1.04±0.07.We studied contractility in isolated myocytes and found no significant differences under basal conditions. We measured cardiac performance by cine-MRI, echocardiography and with a conductance catheter over a period of 4 to 18months and found minimal systematic differences between NTG and ACTC E361G mice under basal conditions. However, the increase in septal thickening, ejection fraction, heart rate and cardiac output following dobutamine treatment was significantly less in ACTC E361G mice compared with NTG. We propose that the ACTC E361G mutation uncouples myofilament Ca2+-sensitivity from Troponin I phosphorylation and blunts the response to adrenergic stimulation, leading to a reduced cardiac reserve with consequent contractile dysfunction under stress, leading to dilated cardiomyopathy.