cDNA Clone and Expression Analysis of Rodent Fast and Slow Skeletal Muscle Troponin I mRNAs

作者：Regine Koppe, Patricia L. Hallauer, George Karpati, Kenneth E.M. Hastings · 发表于：Journal of Biological Chemistry · 年份：1989 · DOI：10.1016/s0021-9258(18)71681-5 · 被引用次数：80 · 研究领域：RNA Research and Splicing、Cardiomyopathy and Myosin Studies、Muscle Physiology and Disorders

We have characterized the structure and expression of rodent mRNAs encoding the fast and slow skeletal muscle isoforms of the contractile regulatory protein, troponin I (TnIfast and TnIslow). TnIfast and TnIslow cDNA clones were isolated from mouse and rat muscle cDNA clone libraries and were used as isoform-specific probes in Northern blot and in situ hybridization studies. These studies showed that the TnIfast and TnIslow mRNAs are expressed in skeletal muscle, but not cardiac muscle or other tissues, and that they are differentially expressed in individual muscle fibers. Fiber typing on the basis of in situ hybridization analysis of TnI isoform mRNA content showed an excellent correlation with fiber type as assessed by myosin ATPase histochemistry. These results directly demonstrate that the differential expression of skeletal muscle TnI isoforms in the various classes of vertebrate striated muscle cells is based on gene regulatory mechanisms which control the abundances of specific TnI mRNAs in individual muscle cells. Both TnIfast and TnIslow mRNAs are expressed, at comparable levels, in differentiated cultures of rat L6 and mouse C2 muscle cell lines. Thus, although neuronal input has been shown to be an important factor in determining fast versus slow isoform-specific expression in skeletal muscle, both TnIfast and TnIslow genes can be expressed in muscle cells in the absence of nerve. Comparison of the deduced rodent TnI amino acid sequences with previously determined...