Transcript levels of the Upf1-3 and Smg1 genes in 13 murine tissues. Transcript levels (copy number per 50 pg of RNA extracted from each of the mentioned tissues) were measured by quantitative RT-PCR using the same samples as previously, and normalized to the level of Hprt1 and β-actin transcripts. Each bar on the graph represents the mean value of at least 3 independent measurements (± standard deviation) in four samples of the same tissue (two samples only were used for testis and ovary). Please note that the scale showing the normalized number of transcripts is different for each gene. Ov: ovary; Te: testis; Br: brain; He; heart; St; stomach; Ad: adrenal gland; Li: liver; Sp: spleen; M.G.: mammary gland; Ki: kidney; Lu: lung; In: intestine; Th: thymus.