Metagene characteristics: Metagene expression profiling map of the 67 tissues studied (panel a), population (b), variability (c, Eq. (2)), metagene over- (d) and underexpression (e) maps. Panel a): Metagene profiles are shown by thick curves whereas thin grey ones show the profiles of associated real genes. The vertical axis is the logged expression change relatively to the mean expression of the selected gene averaged over all tissues. All tiles use the same vertical scale. The number in each tile gives the population of the respective metagene cluster with real genes. The bars color-code the tissue samples (compare with headings in Figure 1). The circles indicate over- and under-expression in selected tissues listed in the boxes (see text). One sees that the metagenes in the top left and the bottom right corner cluster genes strongly overexpressed in nervous (grey circle) and immune system (blue circle) tissues, respectively. Panel d) and e): Red/maroon spots mark overexpression, blue ones underexpression. Selected spots are marked by letters (capital and lower case letters refer to maxima and minima, respectively). They are assigned to different tissues in Table 1.