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.
Sequential activation of alpha-actin genes during avian cardiogenesis: vascular smooth muscle alpha-actin gene transcripts mark the onset of cardiomyocyte differentiation.
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D L Ruzicka, R J Schwartz; Sequential activation of alpha-actin genes during avian cardiogenesis: vascular smooth muscle alpha-actin gene transcripts mark the onset of cardiomyocyte differentiation.. J Cell Biol 1 December 1988; 107 (6): 2575–2586. doi: https://doi.org/10.1083/jcb.107.6.2575
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