Fig. 2.

Mosaic EGFP expression after FLPe recombinase RNA microinjection. Forty-eight hours post fertilization, mosaic expression of fluorescence can be observed in FLPe RNA-injected transgenic zebrafish embryos (a, b). Individual muscle cells that have not had the FRT-flanked transgene excised can be seen fluorescing green. In contrast, non-injected transgenic controls (c, d), show evenly distributed EGFP expression throughout the muscles of the zebrafish. e PCR confirmation of recombinase-mediated site-specific recombination. Genomic DNA from finclips of FLPe RNA-injected transgenic zebrafish was used as a DNA template for PCR to confirm excision of the FRT-flanked EGFP transgene. In FLPe-injected zebrafish (1–8), site-specific recombination produced an 803-bp fragment, indicative of excision. In the non-injected transgenic control, an unexcised 3.7-kb band is expected. Excision products were cloned and sequenced to verify precise FLPe-mediated site-specific recombination in zebrafish