RNA interference in adult mice. a, Representative images of light emitted from mice co-transfected with the luciferase plasmidpGL3-control and either no siRNA, luciferase siRNA or unrelated siRNA. A pseudocolour image representing intensity of emitted light (red, most intense; blue, least intense) superimposed on a greyscale reference image (for orientation) shows that RNAi functions in adult mice. Annealed 21-nucleotide siRNAs (40 mg; Dharmacon) were co-injected into the livers of mice with 2 mg pGL3-control DNA (Promega) and 800 units of RNas in (Promega) in 1.8 ml PBS buffer in 5-7 s. After 72 h, mice were anaesthetized and given 3 mg luciferin intraperitoneally 15 min before imaging. b, siRNA results(six mice per group) from a representative experiment. Mice receiving luciferase siRNA emitted significantly less light than reporter-alone controls (one-way ANOVA with post hoc Fisher's test). Results for reporter alone and unrelated siRNA were statistically similar. c, pShh1-Ff1, but not pShh1-Ff1rev, reduced luciferaseexpression in mice relative to the reporter-alone control. pShh1-Ff1or pShh1-rev (10 mg) were co-injected with 2 mg pGL3-control in1.8 ml PBS buffer. d, Average of three independent shRNA experiments (n=5). Average values for the reporter-alone group are designated as 100% in each of the three experiments. Animals were treated according to the US National Institutes of Health's guidelines for animal care and the guidelines of Stanford University.