Grieshammer U, Sassoon D, Rosenthal N
Department of Biochemistry, Boston University School of Medicine, Massachusetts 02118.
Cell. 1992 Apr 3;69(1):79-93. doi: 10.1016/0092-8674(92)90120-2.
In transgenic mice, muscle-specific regulatory elements from the myosin light chain (MLC) 1/3 locus drive graded expression of a linked CAT reporter gene in selected fast muscles along the anteroposterior axis of the adult animal. The gradient of MLC-CAT transcripts is established early in development, during the generation of somites from the paraxial mesoderm and the activation of myogenic factor gene expression, and is not reflected in the expression of the endogenous MLC1 gene. At later embryonic stages, the gradient of MLC-CAT transcripts persists in intercostal and intervertebral muscles, but is not maintained in other axial muscles. Profiles of CAT transgene activity reveal that the gradient is generated during the maturation of increasingly caudal somites, opposite to the direction of somite development, and is retained in dissociated somite cultures. We propose that coexpression of myogenic factors is necessary but not sufficient to regulate expression of the MLC-CAT transgene, which is responsive to additional positional cues in the embryo.
在转基因小鼠中，来自肌球蛋白轻链（MLC）1/3基因座的肌肉特异性调控元件驱动成年动物前后轴上选定的快肌中相连的CAT报告基因的分级表达。MLC-CAT转录本的梯度在发育早期，即从轴旁中胚层产生体节以及肌源性因子基因表达激活期间就已建立，并且在内源性MLC1基因的表达中未体现出来。在胚胎后期，MLC-CAT转录本的梯度在肋间肌和椎间肌中持续存在，但在其他轴肌中未维持。CAT转基因活性图谱显示，该梯度是在越来越靠尾侧的体节成熟过程中产生的，与体节发育方向相反，并且在解离的体节培养物中得以保留。我们提出，肌源性因子的共表达对于调节MLC-CAT转基因的表达是必要的，但并不充分，该转基因对胚胎中的其他位置线索有反应。
