Sequential activation of alpha-actin genes during avian cardiogenesis: vascular smooth muscle alpha-actin gene transcripts mark the onset of cardiomyocyte differentiation.
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.
Ruzicka
D L
DL
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
Schwartz
R J
RJ
D000199:Actins / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D002454:Cell Differentiation; D002642:Chick Embryo; D003593:Cytoplasm / Q000032:analysis; D015342:DNA Probes; D005786:Gene Expression Regulation; D006321:Heart / Q000196:embryology*; D009131:Muscle, Smooth, Vascular / Q000032:analysis*; D009132:Muscles / Q000032:analysis; D009206:Myocardium / Q000032:analysis; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000032:analysis
D000199:Actins; D015342:DNA Probes; D012333:RNA, Messenger