Li Z, Marchand P, Humbert J, Babinet C, Paulin D
Biologie Moléculaire de la Différenciation, Université Paris 7, France.
Development. 1993 Mar;117(3):947-59. doi: 10.1242/dev.117.3.947.
During the development of the mouse embryo, desmin is one of the first muscle proteins detected in both the heart and the somites. The expression of the desmin gene differs from most other muscle genes, since it is initiated in replicating myoblasts and accumulates as the muscle differentiates. We have characterized a muscle-specific enhancer which directs the expression of desmin in vitro in the myoblasts and myotubes of C2 cells but not in non-myogenic cells. We report here on the generation and characterization of transgenic mice bearing a transgene in which the 1 kb DNA 5' regulatory sequence of the desmin gene is linked to a reporter gene coding for Escherichia coli beta-galactosidase (Des1-nlacZ). The enhancer activity of the desmin promoter is very strong and the reporter gene expression is easily detected in tissue sections. We have demonstrated that the regulatory elements present in the transgene Des1-nlacZ are sufficient to direct muscle-specific and developmentally regulated expression of nlacZ in skeletal muscles. Endogenous desmin expression and transgene activity were found to be correlated during the development of skeletal muscles. The transgene was expressed in the committed mononucleate myoblasts as well as in the myotubes. In addition, we have shown that the desmin-derived sequences direct a highly selective expression of nlacZ in cells that leave the somites and invade the limb bud, indicating that the cells that migrate from the somites are already predetermined for myogenesis. In contrast, smooth and cardiac muscle cells were beta-galactosidase negative both during embryonic and foetal development. Interestingly, the transgene was found to be expressed in the conduction system of the heart, which exhibits many features characteristic of skeletal muscles.
在小鼠胚胎发育过程中，结蛋白是最早在心脏和体节中检测到的肌肉蛋白之一。结蛋白基因的表达与大多数其他肌肉基因不同，因为它在正在复制的成肌细胞中开始表达，并随着肌肉分化而积累。我们鉴定了一种肌肉特异性增强子，它在体外可指导C2细胞的成肌细胞和肌管中结蛋白的表达，但在非肌源性细胞中则无此作用。我们在此报告携带转基因的转基因小鼠的产生和特性，该转基因中结蛋白基因的1 kb DNA 5'调控序列与编码大肠杆菌β-半乳糖苷酶的报告基因相连（Des1-nlacZ）。结蛋白启动子的增强子活性非常强，并且在组织切片中很容易检测到报告基因的表达。我们已经证明，转基因Des1-nlacZ中存在的调控元件足以指导nlacZ在骨骼肌中的肌肉特异性和发育调控表达。在骨骼肌发育过程中，发现内源性结蛋白表达与转基因活性相关。转基因在定向单核成肌细胞以及肌管中表达。此外，我们已经表明，结蛋白衍生的序列在离开体节并侵入肢芽的细胞中指导nlacZ的高度选择性表达，这表明从体节迁移的细胞已经预先确定用于肌生成。相比之下，平滑肌细胞和心肌细胞在胚胎和胎儿发育过程中均为β-半乳糖苷酶阴性。有趣的是，发现转基因在心脏的传导系统中表达，该传导系统表现出许多骨骼肌特有的特征。
