Overall nucleotide composition of miRNAs in different tissues, as assessed by miRNA expression-unweighted (A) and -weighted criteria (B).

<p>Different Roman numerals (I, II, III, and IV) above the bars represent significant differences between occurrence frequencies of nucleotides within the tissue, and different alphabetical letters (a, b, and c) represent the significant difference between occurrence frequencies of a nucleotide among the different tissues (n = 3–4, one-way ANOVA with Tukey’s <i>post hoc</i> test, <i>P</i> < 0.05). * indicates that the occurrence frequency of a nucleotide is smaller in the expression-unweighted criterion than -weighted counterpart within the tissue, or vice versa (Student’s <i>t</i>-test, <i>P</i> < 0.05).