Figure 1. Comparing fluorescent reporter expression and transgenic efficiency in transgenic embryos generated by nuclear transfer, PiggyBAC or Tol2 transgenesis.

Six red fluorescent proteins were examined for bright expression in Xenopus oocytes (A). Using the brightest red fluorescent gene, Katushka, constructs with a ubiquitous promoter (CMV) were examined by three methods: nuclear transfer, PiggyBAC transposition and Tol2 transposition. 250 embryos were injected in four independent experiments using CMV-Katushka constructs, and the number of surviving and transgenic embryos were assessed (Table S1); significantly fewer transgenic embryos (p-value <0.005) were generated by nuclear transfer and PiggyBAC, where large numbers of the surviving Tol2 embryos were transgenic (B). Tol2 transgenics were found to give the brightest and most reliable expression in Xenopus (C).