Frequency of miRNA editing across tissues and species. (A) Estimated miRNA frequencies in brain (B), cerebellum (C), heart (H), kidney (K) and testis (T). From left to right, the animal silhouettes represent human, macaque, mouse, opossum, platypus and chicken. The miRNA identifiers are given in the left-hand column and are followed by the position of the edited site within the mature or star miRNA. The color of each circle corresponds to the proportion of edited reads, while the size of the circle corresponds to the total number of reads for the miRNA in question. Note that these data are not normalized and that expression levels therefore should not be compared across samples. Gray shading indicates the absence of an annotated miRNA ortholog in that particular species, based on the information in Table S1 in Additional file 2. The data used to generate this figure are provided in Table S2 in Additional file 2. (B) Comparison of editing frequencies in neural (brain and cerebellum) versus non-neural (heart, kidney and testis) tissues in human, macaque and mouse, for miRNAs with at least 10 reads in all relevant samples. The median frequency is indicated by a blue line. (C) Comparison of editing frequencies in human and mouse samples for the same miRNAs as in (B). The median frequency is indicated by a blue line. (D) Hierarchical clustering of the same miRNAs as in (B), based on editing frequencies in five tissues in human (hsa), macaque (mml) and mouse (mmu). Orthologous miRNAs have been given the same color. The clustering was performed using the R function hclust and Ward’s method.