Fig. 1

A tamoxifen-inducible Cre/lox method for mosaic cell labeling and lineage tracing in the adult zebrafish caudal fin. (A) Embryos carrying both dusp6:Cre-ERT2 and EAB:EGFP-FlEx-mCherry transgenes are briefly exposed to tamoxifen to sporadically induce rare genetic recombination events that permanently switch those cells and their descendants to mCherry from EGFP expression. (B, C) Whole mount epifluorescent images of 3 day old Tg(dusp6:Cre-ERT2, EAB:EGFP-FlEx-mCherry) fish that were treated with tamoxifen (1 μM) at 30% epiboly for 48 h. Mosaic mCherry⁺ cells (magenta) are observed in various tissues (B), including pectoral fin mesenchyme (C). The white arrow highlights mCherry⁺ cells. (D, E) The EAB:EGFP-FlEx-mCherry transgene is expressed in various cell lineages that make up the adult caudal fin. Longitudinal (D) and transverse (E) sections of adult caudal fins of Tg(EAB:EGFP-FlEx-mCherry) animals. EGFP expressing cells (green) were are stained with Hoechst to visualize nuclei (magenta). (F–I, F*–I*) Tg(dusp6:Cre-ERT2, EAB:EGFP-FlEx-mCherry) adult animals, treated as above, exhibit spatially restricted mCherry⁺ mosaics in four distinct classes. The dashed box marked with an asterisk represents the region shown at higher magnification in the panels directly below (F*–I*). (F and F*) Class 1 epidermal mosaics. (G and G*) Class 2 fibroblast mosaics. (H and H*) Class 3 osteoblast mosaics. (I and I*) Class 4 putative macrophage mosaics. In each panel (F-I*), the expression of EGFP (green) and mCherry (magenta) is shown. The top and bottom of each panel correspond to the distal and proximal regions of the fin, respectively.