Fig. 4

CircRNAs expression profiles in vertebrate brain tissues. a CircRNAs identified in six vertebrate brain tissues (RNase R + Ribomiuns treatment) by CIRI-full. The number of shared circRNAs is shown on the phylogenetic tree. The table on the right shows the RNA-seq data set size and the numbers of identified circRNAs, cirexons, intronic/intergenic circRNA fragments (ICFs), and full-length circRNAs. The histogram on the right shows the length distribution of reconstructed circRNAs; blue, orange, and gray represent complete, nearly complete and partial circRNAs, respectively. b Overlap of highly expressed mRNAs and circRNAs in closely related species. Obviously, mRNA expression is more conserved than circRNA expression in closely related species (human vs. macaque, mouse vs. rat). c Expression levels of circRNAs and their corresponding mRNA genes. a, b, c, and d represent the four ancestral nodes, as shown in panel a. Species-specific circRNAs in four species (shown in blue) have much lower expression levels than the shared circRNAs present in ancestral nodes. d Percentage of circRNAs (BSJ ≥ 10 reads) containing four types of alternative splicing events. e Expression profiles of circRNA isoforms in the six species. The relative abundance of circRNA isoforms were normalized between 0 and 1