Validation of expression data by independent confirmation. (a) The P value of Spearman's Rank correlations (see Materials and methods) is shown for all possible comparisons among the 13 tissues common to all three studies (ours and those by Su et al.  and Bono et al. ) and 1,109 genes for which the same isoform is unambiguously represented on the arrays used in each of the studies (see Materials and methods). (b) Microarray data and RT-PCR results for 47 known and predicted XM genes are shown. Genes were selected to represent primarily those without GO Biological Processes (GO-BP) assignment and to encompass expression in all 18 tissues, and were biased towards those with functions predicted by support vector machines (SVMs) in categories of interest (or expressed in tissues of interest). The three columns on the far right show whether each XM gene was uncharacterized (not annotated) in GO-BP, and whether it is represented by a cDNA or EST.