Complex fiber-type-specific expression of fast skeletal muscle troponin I gene constructs in transgenic mice

作者：Patricia L. Hallauer, Holly L. Bradshaw, Kenneth E.M. Hastings · 发表于：Development · 年份：1993 · DOI：10.1242/dev.119.3.691 · 被引用次数：69 · 研究领域：Muscle Physiology and Disorders、Cardiomyopathy and Myosin Studies、Viral Infections and Immunology Research

We analyzed, in transgenic mice, the cellular expression pattern of the quail fast skeletal muscle troponin I (TnIfast) gene and of a chimeric reporter construct in which quail TnIfast DNA sequences drive expression of E. coli beta-galactosidase (beta-gal). Both constructs were actively expressed in skeletal muscle and specifically in fast, as opposed to slow, muscle fibers. Unexpectedly, both constructs showed a marked differential expression among the adult fast fiber subtypes according to the pattern IIB > IIX > IIA. This expression pattern was consistent in multiple lines and differed from the endogenous mouse TnIfast pattern, which shows approximately equal expression in all fast fibers. These observations indicate that distinct regulatory mechanisms contribute to high-level expression of TnIfast in the various fast fiber subtypes and suggest that the outwardly simple pattern of equal expression in all fast fiber types shown by the endogenous mouse TnIfast gene is based on an intricate system of counterbalancing mechanisms. The adult expression pattern of the TnIfast/beta-gal construct emerged in a two-stage developmental process. Differential expression in fast versus slow fibers was evident in neonatal animals, although expression in fast fibers was relatively weak and homogeneous. During the first two weeks of postnatal life, expression in maturing IIB fibers was greatly increased whereas that in IIA/IIX fibers remained weak, giving rise to marked differential express...