The transgenic construct contains a human skeletal muscle alpha actin promoter and first exon (- 2,000 to + 239 relative to the transcription start site) promoter, a beta-globin intron II and a poly(A) tail followed by a modified reverse tetracycline-regulated transactivator (rtTA) from Tet3G. Mice from founder line 6 were found to have robust H2B-GFP expression in both slow- and fast-twitch muscles of the lower hind limbs. (J:336174)