Maeda M, Holder E, Lowes B, Valent S, Bies R D
Division of Cardiology, VA Medical Center, Denver, CO, USA.
Circulation. 1997 Jan 7;95(1):17-20. doi: 10.1161/01.cir.95.1.17.
The cytoskeleton plays an important role in maintaining cell structure and integrity. Defects in cytoskeletal proteins can cripple cell strength and may cause cardiomyopathy. We analyzed heart tissues from subjects with dilated cardiomyopathy for abnormalities in the cardiac cytoskeleton. Metavinculin, a cardiac isoform of the cytoskeletal protein vinculin, connects actin microfilaments to the intercalated disk and membrane costameres of the heart.
Metavinculin and vinculin transcripts and protein were analyzed by polymerase chain reaction (PCR) and Western blotting. Thirty-three human heart specimens were studied, including 5 normal controls, 4 subjects with ischemic cardiomyopathy, 1 with X-linked cardiomyopathy, and 23 with idiopathic dilated cardiomyopathy (IDC). PCR of cardiac cDNA detected absence of the metavinculin transcript in cardiac tissue from a subject with IDC. PCR of genomic DNA showed that the metavinculin exon was present but not utilized in the cardiac transcript. Western blot analysis demonstrated absence of metavinculin protein in the heart from this subject. Immunostaining of cardiac vinculin in this heart showed disorganized intercalated disk structures. Metavinculin deficiency was associated with normal cardiac expression of the cytoskeletal proteins vinculin, alpha-actinin, and dystrophin. Normal metavinculin expression in the other heart specimens suggests that the defect is specific in the IDC subject identified.
These results demonstrate an association between metavinculin deficiency and dilated cardiomyopathy due to a defect in alternative mRNA splicing.
细胞骨架在维持细胞结构和完整性方面发挥着重要作用。细胞骨架蛋白的缺陷会削弱细胞强度，并可能导致心肌病。我们分析了扩张型心肌病患者的心脏组织，以寻找心脏细胞骨架的异常情况。间线蛋白是细胞骨架蛋白纽蛋白的一种心脏异构体，它将肌动蛋白微丝连接到心脏的闰盘和膜性肌小节。
通过聚合酶链反应（PCR）和蛋白质印迹法分析间线蛋白和纽蛋白的转录本及蛋白质。研究了33个人类心脏标本，包括5例正常对照、4例缺血性心肌病患者、1例X连锁心肌病患者和23例特发性扩张型心肌病（IDC）患者。对心脏cDNA进行PCR检测发现，一名IDC患者的心脏组织中不存在间线蛋白转录本。对基因组DNA进行PCR检测表明，间线蛋白外显子存在，但未在心脏转录本中使用。蛋白质印迹分析显示该患者心脏中不存在间线蛋白。对该心脏中的心脏纽蛋白进行免疫染色显示闰盘结构紊乱。间线蛋白缺乏与细胞骨架蛋白纽蛋白、α-辅肌动蛋白和肌营养不良蛋白的正常心脏表达相关。其他心脏标本中间线蛋白表达正常，表明所鉴定的IDC患者中的缺陷是特异性的。
这些结果表明，由于选择性mRNA剪接缺陷，间线蛋白缺乏与扩张型心肌病之间存在关联。
