Zajdel R W, McLean M D, Lemanski S L, Muthuchamy M, Wieczorek D F, Lemanski L F, Dube D K
Department of Anatomy and Cell Biology, State University of New York Health Science Center at Syracuse, 13210, USA.
Dev Dyn. 1998 Dec;213(4):412-20. doi: 10.1002/(SICI)1097-0177(199812)213:4<412::AID-AJA6>3.0.CO;2-C.
Expression of tropomyosin protein, an essential component of the thin filament, has been found to be drastically reduced in cardiac mutant hearts of the Mexican axolotl (Ambystoma mexicanum) with no formation of sarcomeric myofibrils. Therefore, this naturally occurring cardiac mutation is an appropriate model to examine the effects of delivering tropomyosin protein or tropomyosin cDNA into the deficient tissue. In this study, we describe the replacement of tropomyosin by using a cationic liposome transfection technique applied to whole hearts in vitro. When mouse alpha-tropomyosin cDNA under the control of a cardiac-specific alpha-myosin heavy chain promoter was transfected into the mutant hearts, tropomyosin expression was enhanced resulting in the formation of well-organized sarcomeric myofibrils. Transfection of a beta-tropomyosin construct under control of the same promoter did not result in enhanced organization of the myofibrils. Transfection of a beta-galactosidase reporter gene did not result in the formation of organized myofibrils or increased tropomyosin expression. These results demonstrate the importance of alpha-tropomyosin to the phenotype of this mutation and to normal myofibril formation. Moreover, we have shown that a crucial contractile protein can be ectopically expressed in cardiac muscle that is deficient in this protein, with the resulting formation of organized sarcomeres.
原肌球蛋白是细肌丝的重要组成部分，在墨西哥钝口螈（美西螈）的心脏突变体中，原肌球蛋白蛋白的表达大幅降低，且未形成肌节肌原纤维。因此，这种自然发生的心脏突变是一个合适的模型，可用于研究将原肌球蛋白蛋白或原肌球蛋白cDNA导入缺陷组织的效果。在本研究中，我们描述了通过应用阳离子脂质体转染技术对体外完整心脏进行原肌球蛋白的替代。当在心脏特异性α-肌球蛋白重链启动子控制下的小鼠α-原肌球蛋白cDNA转染到突变心脏中时，原肌球蛋白表达增强，导致形成组织良好的肌节肌原纤维。在相同启动子控制下转染β-原肌球蛋白构建体并未导致肌原纤维组织增强。转染β-半乳糖苷酶报告基因未导致形成有组织的肌原纤维或原肌球蛋白表达增加。这些结果证明了α-原肌球蛋白对该突变表型和正常肌原纤维形成的重要性。此外，我们已经表明，一种关键的收缩蛋白可以在缺乏该蛋白的心肌中异位表达，并导致形成有组织的肌节。
