Gene targeting the myf-5 locus with nlacZ reveals expression of this myogenic factor in mature skeletal muscle fibres as well as early embryonic muscle
Article first published online: 7 DEC 1998
Copyright © 1996 Wiley-Liss, Inc.
Volume 206, Issue 3, pages 291–300, July 1996
How to Cite
Tajbakhsh, S., Bober, E., Babinet, C., Pournin, S., Arnold, H. and Buckingham, M. (1996), Gene targeting the myf-5 locus with nlacZ reveals expression of this myogenic factor in mature skeletal muscle fibres as well as early embryonic muscle. Dev. Dyn., 206: 291–300. doi: 10.1002/(SICI)1097-0177(199607)206:3<291::AID-AJA6>3.0.CO;2-D
- Issue published online: 7 DEC 1998
- Article first published online: 7 DEC 1998
- Manuscript Accepted: 29 JAN 1996
- Manuscript Received: 15 AUG 1995
- Homologous recombination;
- Mature skeletal muscle;
We have introduced the nlacZ reporter gene into the locus of the myogenic factor gene myf-5 by homologous recombination in embryonic stem (ES) cells. Targeted ES clones were injected into precompaction morula, and the β-galactosidase expression pattern was monitored. These mice permit the sensitive visualization of myf-5 expression throughout the embryo, and provide a standard for comparing it with that seen with different myf-5/nlacZ transgenes. Thus, in a comparison using ES cells in chiameric embryos containing the targeted or randomly integrated myf-5/nlacZ construct, we demonstrate that 5.5 kbp of myf-5 upstream flanking sequence including exon1 and most of intron1 directs some skeletal muscle expression, but this is neither qualitatively nor quantitatively equivalent to that of the endogenous gene. Myf-5 is expressed early, before terminal myogenesis takes place in the medial half of the somite, and subsequently it is a major myogenic factor as skeletal muscle forms. All skeletal muscle shows β-galactosidase activity, even after birth, indicating that myf-5 expression is not confined to primary myotubes, which are derived from embryonic myoblasts, but is also present in muscles containing different adult fibre types. The presence of myf-5 transcripts from the endogenous gene in older muscle was confirmed by in situ hybridization. These results suggest that the myf-5 gene is not activated in only a subset of muscle cells and are consistent with the results on the MyoD knockout mice. © 1996 Wiley-Liss, Inc.