Fig. 2

Method of analyzing tissue EST profile. a Data presentation format as presented in X-axis and Y-axis and tissue order is applied to all the genes examined. As an example, the gene expression profile of human house-keeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH Hs.544577) in 22 human tissues is shown. The gene expression data was normalized by the β-actin (Hs. 520640) expression data from the same tissue, which is presented on the left Y-axis. The arbitrary unit for comparing gene expression level among all tissues was generated by normalizing the gene expression data (after normalization by β-actin) in the tissue with the median expression level among all the tissues, which is presented on the right Y-axis. In order to define confidence interval for statistically high expression level of a given gene, we calculated the mean of confidence intervals [mean (X) + 2 × standard deviations (SD) = 3.63] of three randomly chosen house-keeping genes including GAPDH, hypoxanthine phosphoribosyltransferase 1 (HPRT1 Hs.412707), and glucuronidase, beta (GUSB Hs.255230). The expression variations of given genes in tissues, when they were larger than 3.63-fold, were defined as the high expression levels with statistical significance (the right Y-axis). In this example, GAPDH is highly expressed in muscle. b Same strategy applies to mouse genes among 18 tissues. The mean of [X + 2 × SD = 4.12] was determined as the confidence interval for mouse genes expression