Fig. 3. Structure of myostatin-GFP (green fluorescent protein) construct and activity of myostatin promoter in zebrafish embryos. (Top) The myostatin-GFP construct contains a 1.2 kb zebrafish myostatin 5' flanking sequence including the 5'UTR (5'-untranslated region). To ensure proper processing of the RNA transcripts, the rabbit ß-globin intron-2 sequence (in) and the SV40 polyadenylation and transcription termination signals are included in the myogenin-GFP construct. (A) GFP expression in myofibers and forebrain region of zebrafish injected with the myostatin-GFP construct at 24 h.p.f. (hours post-fertilization). Forebrain expression is indicated by the white arrow. (B) Higher magnification view showing GFP expression in muscle fibers. (C) GFP expression in the floor plate (white arrows) of zebrafish embryos injected with the myostatin-GFP construct at 24 h.p.f. (D) Whole-mount anti-GFP staining confirming GFP expression in myofibers and brain (arrow) of injected zebrafish embryos (24 h.p.f.). (E) Higher magnification view of anti-GFP staining in muscle fibers. (F) Expression of GFP in the forebrain region (arrow) of a myostatin-GFP injected embryo, revealed by whole-mount antibody staining. Scale bars, 500 µm (A,D); 200 µm (B,C,E,F).