Analysis of tissue-specific 3’UTR isoforms. We calculated the proportions of genes in each tissue that have tissue-specific 3’UTR isoforms and how many of these 3’UTRs have predicted microRNA targets. (A) Charts displaying the proportion of genes containing tissue-specific 3’UTR isoforms (blue). The intestine expresses approximately two times as many tissue-specific 3’UTR isoforms as muscle tissues. (B) We compared the proportion of microRNA targeted genes with tissue-specific 3’UTRs (blue) to the same number of randomly selected genes (grey) in each tissue. Significantly more genes with tissue-specific 3’UTR isoforms have microRNA targets. microRNA targets were predicted using PicTar Software, using three species and five species conservation criteria, and from ALG-1 pull-down experiments (Zisoulis et al. 2010 ). *P-value <0.05, **P < 0.01, based on two-tailed Student’s t-test.