RedEfish: Generation of the Polycistronic mScarlet: GSG-T2A: Ttpa Zebrafish Line.

The vitamin E regulatory protein, the alpha-tocopherol transfer protein (Ttpa), is necessary for zebrafish embryo development. To evaluate zebrafish embryo Ttpa function, we generated a fluorescent-tagged zebrafish transgenic line using CRISPR-Cas9 technology. One-cell stage embryos (from Casper (colorless) zebrafish adults) were injected the mScarlet coding sequence in combination with cas9 protein complexed to single guide RNA molecule targeting 5' of the ttpa genomic region. Embryos were genotyped for proper insertion of the mScarlet coding sequence, raised to adulthood and successively in-crossed to produce the homozygote RedEfish (mScarlet: GSG-T2A: Ttpa). RedEfish were characterized by in vivo fluorescence detection at 1, 7 and 14 days post-fertilization (dpf). Fluorescent color was detectable in RedEfish embryos at 1 dpf; it was distributed throughout the developing brain, posterior tailbud and yolk sac. At 7 dpf, the RedEfish was identifiable by fluorescence in olfactory pits, gill arches, pectoral fins, posterior tail region and residual yolk sac. Subsequently (14 dpf), the mScarlet protein was found in olfactory pits, distributed throughout the digestive tract, along the lateral line and especially in caudal vertebrae. No adverse morphological outcomes or developmental delays were observed. The RedEfish will be a powerful model to study Ttpa function during embryo development.