Einat P, Shani M, Yaffe D
Department of Cell Biology, Weizmann Institute of Science, Rehovot, Israel.
Differentiation. 1990 Jul;44(1):36-41. doi: 10.1111/j.1432-0436.1990.tb00534.x.
Both skeletal muscle and cardiac actins are co-expressed in the newborn heart. However, the amount of the skeletal muscle actin and its mRNA rapidly decreases during early development and the cardiac actin predominates in the adult heart. In BALB/c and DBA mice there is a mutation in the cardiac actin gene which is associated with decreased levels of cardiac actin mRNA and high levels of the skeletal muscle actin transcript in the adult heart. To examine the possibility that the amount of cardiac actin gene product modulates the expression of the skeletal muscle actin gene in the heart, transgenic mice carrying a tagged skeletal muscle actin gene were produced, and the expression of the endogenous and endogenous and exogenous actin gene was analyzed in offspring carrying different combinations of the cardiac actin alleles. It was found that both the endogenous and exogenous skeletal muscle actin genes were expressed at low levels in the heart of adult mice homozygous for the wild-type cardiac actin gene allele, at abnormally high levels in mice homozygous for the mutated cardiac actin allele, and at intermediate levels in heterozygous mice. This shows that the level of expression of the cardiac actin gene has a trans effect on the expression of the skeletal muscle actin gene.
骨骼肌肌动蛋白和心肌肌动蛋白在新生心脏中共同表达。然而，在早期发育过程中，骨骼肌肌动蛋白及其mRNA的量迅速减少，而心肌肌动蛋白在成年心脏中占主导地位。在BALB/c和DBA小鼠中，心肌肌动蛋白基因存在突变，这与成年心脏中心肌肌动蛋白mRNA水平降低和骨骼肌肌动蛋白转录本水平升高有关。为了研究心肌肌动蛋白基因产物的量是否调节心脏中骨骼肌肌动蛋白基因的表达，制备了携带标记的骨骼肌肌动蛋白基因的转基因小鼠，并在携带不同心肌肌动蛋白等位基因组合的后代中分析了内源性和外源性肌动蛋白基因的表达。结果发现，内源性和外源性骨骼肌肌动蛋白基因在野生型心肌肌动蛋白基因等位基因纯合的成年小鼠心脏中低水平表达，在突变型心肌肌动蛋白等位基因纯合的小鼠中异常高水平表达，在杂合小鼠中表达水平居中。这表明心肌肌动蛋白基因的表达水平对骨骼肌肌动蛋白基因的表达具有反式作用。
