Average mRNA expression of the predicted target genes for each miRNA. (a) Schematic diagram illustrating how the average expression levels of individual miRNA predicted target gene sets are calculated and then compared with that of all predicted target genes. In this example miR-124a and miR-29 are shown to map to different, but overlapping, subsets of target genes. The average expression values of all predicted target genes and the miR-124a and miR-29 predicted targets are calculated. The probability that the expression levels of the genes predicted to be targeted by miR-124a and miR-29 in this tissue are drawn at random from the expression levels of all predicted target genes is calculated. (b) Ranked mean expression values (y-axis) of all predicted target genes for each miRNA (x-axis) with target genes expressed in liver are depicted as red circles (± standard error). These include the predicted mRNA targets of the known liver-specific miR-122 (extreme left). Several miRNAs have higher than expected target gene expression, for example, miR-1 and miR-205 (extreme right). (c) Red circles indicate the probability (log10, y-axis) that the set of target gene expression levels for each miRNA (x-axis) is drawn at random from the whole population of expressed target genes for all miRNAs (t-test, p < 0.1). For each miRNA the mean probability (± standard error) derived from five random sets of predicted target genes is plotted in grey.