Figure 1.

siRNA suppression of heterologous gene expression in Xenopus embryos. (A) Temporal expression of the luciferase gene during early embryogenesis. Plasmid pCS2-Luc (150 pg in 5 nl), an expression vector for the GL3 version of luciferase, was microinjected into both blastomeres of 2-cell stage embryos. Injected embryos were collected at different stages, lysed and assayed for luciferase activity. All values represent the means of four groups of embryos and error bars indicate standard deviation from the mean. Experiments were repeated twice with similar results. (B) Gene-specific inhibition of luciferase expression by siRNA. Luciferase expression plasmid pCS2-Luc (150 pg) and the indicated siRNAs (20 µM) were co-injected into embryos as in (A). The injection volume was 5 nl. Embryos were collected at stages 16 and 20. The average luciferase activity recovered from control embryos without siRNA was set as 100%. GL3 siRNA, siRNA targeting GL3 luciferase; GL2 siRNA, siRNA targeting the GL2 version of luciferase; mock siRNA, siRNA targeting irrelevant human but not Xenopus sequences. Similar results were obtained using 10 µM siRNA (data not shown).