Fig. 4

Blastula transplantations reveal cardiomyocytes expressing both donor and host transgenes. a Schematic drawing of transplantation experiment shown in b–d. Tg(myl7:EGFP) cells were transplanted into Tg(myl7:nDsred2) hosts at the blastula stage. b–d Cardiomyocytes expressing both host-derived myl7:EGFP (green cytoplasm) and donor-derived myl7:nDsred2 (red nucleus) transgenes (b) are evident from orthogonal sections (c) and Y axis rotation of a 3D volume rendering (d). EGFP⁺nDsred2⁺ cardiomyocytes (white circle) were detected in 9 out of 18 mosaic hearts at 3 dpf. e Schematic drawing of transplantation experiment shown in f–h. Tg(actb2:loxP-mCherry-loxP-EGFP) cells were transplanted into Tg(myl7:creER) hosts at the blastula stage. Transplanted animals were treated with 4-OHT starting at 24 hpf. New 4-OHT was added to the embryo medium daily. f A single focal plane of a confocal stack shows a dorsal view of a 3 dpf chimeric heart, anterior up. Donor-derived mCherry⁺ cells (red) and fusion-derived EGFP⁺ cardiomyocytes (green, arrows) were detected by live imaging in 5 out of 13 mosaic hearts (mixed genotypes, creER⁺ and creER⁻). g Maximum intensity projection of a 50 μm confocal stack shows a lateral view of a 7 dpf chimeric heart, anterior up, dorsal to the left. Tg(actb2:loxP-mCherry-loxP-EGFP) donor cells are shown in red. Host-derived Cre-mediated recombination of the donor transgene was detectable by EGFP immunofluorescence (green) in 11 out of 39 mosaic hearts (mixed genotypes, creER⁺, and creER⁻). h Magnified image showing area outlined by red box in g. Scale bars: 20 μm