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

C Neville, D Gonzales, L Houghton, M J McGrew, N Rosenthal

Research output: Contribution to journalArticlepeer-review


The two proteins encoded by the fast alkali myosin light chain (MLC) 1f/3f locus are developmentally regulated, muscle specific, and expressed exclusively in fast-twitch fibers. Their expression is independently regulated by two separate promoters and a downstream enhancer. Previous studies showed a reporter gene directed by the rat MLC If promoter and MLC enhancer to exhibit correct skeletal muscle-specific expression in transgenic mice during development and to be preferentially expressed in fast-twitch Type IIB fibers [Donoghue et al., (1991) J. Cell B.ol. 115:423-434]. The MLC 3f promoter also directed muscle-specific expression of a CAT reporter gene in adult transgenic mice and showed little dependence upon the enhancer. Here, we show that the MLC 3f promoter also directs transgene expression in the fast-twitch fibers of adult skeletal muscle, but almost exclusively to fiber Types IIA and IIX. MLC 3f transgene expression occurs in only a subset of the fiber types that express the endogenous locus, indicating modular elements included in the transgene confer fiber-specific transcription regulation. MyoD protein was also found to be restricted to fiber Types IIA and IIX, providing evidence for its possible role in mediating fiber-specific gene expression.
Original languageEnglish
Pages (from-to)157-62
Number of pages6
JournalDevelopmental Genetics
Issue number2
Publication statusPublished - 1996


  • Animals
  • Chloramphenicol O-Acetyltransferase
  • Enhancer Elements, Genetic
  • Gene Expression Regulation, Developmental
  • Genes, Reporter
  • Mice
  • Mice, Transgenic
  • Muscle Development
  • Muscle Fibers, Fast-Twitch
  • Muscle Proteins
  • Muscle, Skeletal
  • MyoD Protein
  • Myosin Light Chains
  • Rats
  • Recombinant Fusion Proteins
  • Regulatory Sequences, Nucleic Acid
  • Transcription, Genetic
  • Transgenes


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