TnIfast IRE enhancer: multistep developmental regulation during skeletal muscle fiber type differentiation.

To identify developmental steps leading to adult skeletal muscle fiber-type-specific gene expression, we carried out transgenic mouse studies of the IRE enhancer of the quail TnIfast gene. Histochemical analysis of IRE/herpesvirus tk promoter/beta-galactosidase reporter transgene expression in adult muscle directly demonstrated IRE-driven fast vs. slow fiber-type specificity, and IIB>IIX>IIA differential expression among the fast fiber types: patterns similar to those of native-promoter TnIfast constructs. These tissue- and cell-type specificities are autonomous to the IRE and do not depend on interactions with a muscle gene promoter. Developmental studies showed that the adult pattern of IRE-driven transgene expression emerges in three steps: (1) activation during the formation of primary embryonic (presumptive slow) muscle fibers; (2) activation, to markedly higher levels, during formation of secondary (presumptive fast) fibers, and (3) differential augmentation of expression during early postnatal maturation of the IIB, IIX, IIA fast fiber types. These results provide insight into the roles of gene activation and gene repression mechanisms in fiber-type specificity and can account for apparently disparate results obtained in previous studies of TnI isoform expression in development. Each of the three IRE-driven developmental steps is spatiotemporally associated with a different major regulatory event at the fast myosin heavy chain gene cluster, suggesting that diverse muscle gene families respond to common, or tightly integrated, regulatory signals during multiple steps of muscle fiber differentiation.

Hallauer PL ，Hastings KE 《DEVELOPMENTAL DYNAMICS》

Modular elements of the MLC 1f/3f locus confer fiber-specific transcription regulation in transgenic mice.

Neville C ，Gonzales D ，Houghton L ，McGrew MJ ，Rosenthal N ... -  《developmental genetics》

Developmental regulation of troponin I isoform genes in striated muscles of transgenic mice.

Zhu L ，Lyons GE ，Juhasz O ，Joya JE ，Hardeman EC ，Wade R ... -  《DEVELOPMENTAL BIOLOGY》

Transcriptional control of muscle plasticity: differential regulation of troponin I genes by electrical activity.

Calvo S ，Stauffer J ，Nakayama M ，Buonanno A ... -  《developmental genetics》

Loss of myostatin expression alters fiber-type distribution and expression of myosin heavy chain isoforms in slow- and fast-type skeletal muscle.

Girgenrath S ，Song K ，Whittemore LA 《MUSCLE & NERVE》