Ruzicka D L, Schwartz R J
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
J Cell Biol. 1988 Dec;107(6 Pt 2):2575-86. doi: 10.1083/jcb.107.6.2575.
The expression of cytoplasmic beta-actin and cardiac, skeletal, and smooth muscle alpha-actins during early avian cardiogenesis was analyzed by in situ hybridization with mRNA-specific single-stranded DNA probes. The cytoplasmic beta-actin gene was ubiquitously expressed in the early chicken embryo. In contrast, the alpha-actin genes were sequentially activated in avian cardiac tissue during the early stages of heart tube formation. The accumulation of large quantities of smooth muscle alpha-actin transcripts in epimyocardial cells preceded the expression of the sarcomeric alpha-actin genes. The accumulation of skeletal alpha-actin mRNAs in the developing heart lagged behind that of cardiac alpha-actin by several embryonic stages. At Hamburger-Hamilton stage 12, the smooth muscle alpha-actin gene was selectively down-regulated in the heart such that only the conus, which subsequently participates in the formation of the vascular trunks, continued to express this gene. This modulation in smooth muscle alpha-actin gene expression correlated with the beginning of coexpression of sarcomeric alpha-actin transcripts in the epimyocardium and the onset of circulation in the embryo. The specific expression of the vascular smooth muscle alpha-actin gene marks the onset of differentiation of cardiac cells and represents the first demonstration of coexpression of both smooth muscle and striated alpha-actin genes within myogenic cells.
利用mRNA特异性单链DNA探针原位杂交技术，分析了禽早期心脏发生过程中细胞质β-肌动蛋白以及心肌、骨骼肌和平滑肌α-肌动蛋白的表达情况。细胞质β-肌动蛋白基因在早期鸡胚中普遍表达。相比之下，α-肌动蛋白基因在心脏管形成的早期阶段在禽心脏组织中被依次激活。在心肌外膜细胞中大量平滑肌α-肌动蛋白转录本的积累先于肌节α-肌动蛋白基因的表达。发育中心脏中骨骼肌α-肌动蛋白mRNA的积累比心肌α-肌动蛋白落后几个胚胎阶段。在汉伯格-汉密尔顿第12期，平滑肌α-肌动蛋白基因在心脏中被选择性下调，以至于只有随后参与血管干形成的圆锥继续表达该基因。平滑肌α-肌动蛋白基因表达的这种调节与心肌外膜中肌节α-肌动蛋白转录本的共表达开始以及胚胎中循环的开始相关。血管平滑肌α-肌动蛋白基因的特异性表达标志着心脏细胞分化的开始，并且是肌源性细胞内平滑肌和横纹肌α-肌动蛋白基因共表达的首次证明。
