Although the analysis can be per formed for any tissues with available microarray data where Ne is the total number of expression profiles in the experiment set, and Nc is the total number of expression profiles in the control set. Third, for each selected probe set, its expression level in the experiment set is compared with that in the con trol set. Our assumption is selleck chem that potential tissue selective genes should show higher expression in the experiment arrays than in the control arrays. Score2 is calculated as follows, we present in this paper the results from three case studies on brain, liver and testis selective gene expression. Brain selective gene expression The human brain is highly complex, and contains 50 100 billion neurons. There are many different brain regions with specific functions.

For example, the frontal lobe is involved in higher mental functions and long term memories, whereas the occipital lobe is the visual processing center. In this study, the microarray expres sion profiles of different brain regions were combined into the experiment set, and compared where X e is the mean expression level of the selected probe set in the Se experiment arrays with significant expression, and X c is the mean expression level in con trol arrays. In this study, the control arrays were sorted according to their expression values for the selected probe set, and the top Se control arrays with the highest expression values were used to compute the mean, X c. The probe sets with Score2 0 were excluded from con sideration for tissue selective genes.

Finally, the potential tissue selective gene targets are prioritized according to the overall score, which is calcu lated as follows, with the expression profiles of non brain tissues in the control set. Thus, the brain selective genes identified in this study might be involved in basic neuron functions such as neural signal processing and transmission via synapses. Table 2 shows the top 20 high scoring genes from one of the analyses with different parameter settings. In this analysis, significant expression was defined by the detec tion call being Present and the relative expression value no less than 1. 00. The minimum number of significant expression in the experiment group was set to 62, and the maximum number of significant expression in the control group was set to 24.

With the above parameters, 222 genes have been identified as brain selective targets with the prior ity score ranging from 1. 18 to 4. 69. The permutation analysis suggests that the brain selective expression patterns of all the selected genes are statistically significant. In Figure 3, the gene Anacetrapib expression patterns are visualized with the heat map generated by using TM4 MeV. Clearly, the transcripts of the selected genes are predominantly detected in brain samples.