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Fig. 1 | BMC Genomics

Fig. 1

From: Intron and gene size expansion during nervous system evolution

Fig. 1

Neuronal intron and gene size expansion in diverse animal species. a Expression of the longest genes is enriched in neuronal tissues of vertebrates and invertebrates. Each plot shows smooth-quantile-normalized transcriptome data across multiple tissues or cell types from individual species. Each line represents mean gene expression in cube root transcripts per million (TPM) versus gene length (kb). Genes were segregated into 100 bins according to gene length, and points show average gene length of each bin. Transparent ribbons show 95% confidence intervals. Red lines show neuronal tissues and grey lines show non-neuronal tissues (see Additional file 2: Table S1 for a full list of tissues for each species). Tissue transcriptomes were obtained from the EMBL Expression Atlas [21] for all species except Drosophila melanogaster [18] and Octopus bimaculoides [19]. Branch lengths for the phylogenetic tree were obtained from TimeTree.org [22]. Organism outlines were depicted by author MJM from the following image references in accordance with respective licensing: Homo sapiens [23]; Bos taurus [24]; Monodelphis domestica [25]; Gallus gallus [26]; Anolis carolinensis [27]; Octopus bimaculoides [28]; Drosophila melanogaster [29]; Caenorhabditis elegans [30]; and Zea mays [31]. b Mean intron length (kb) versus ordinal position in neuronal (red) and non-neuronal tissues (grey) across the same species presented in Fig. 1a. Genes with only slight expression fold-difference of the top expressing tissue over the next highest-expressing tissue (< 2 fold-difference; left) are contrasted against genes with more than 5 fold-difference in expression (right). Error bars show standard error

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