Figure. Transcriptome summary 
Summary of structural elements from input GTF. Structural elements include the frequency of genes within each range of transcript per gene values (top row, histogram). For each range of transcripts per gene, the distribution of exon regions per gene (second row, box plot) represent the number of exons disregarding alternative donors and acceptors, the number of unique exons per gene (third row, box plot) represents alternative donor/acceptors and alternative exons, the proportion of transcripts with intron retention (fourth row, heatmap), the proportion of exon regions with alternate donors/acceptors (fifth row, heatmap), the proportion of variable exon regions (sixth row, heatmap) represents the alternative exons disregarding alternative donors and acceptors, and the proportion of variable nucleotides (bottom row, heatmap) represents nucleotides that are contained in alternative exons and alternative donors and acceptors. Transcriptome analyses performed by TranD [1].  

1. Nanni, A., Titus-McQuillan, J., Moskalenko, O., Pardo-Palacios, F., Liu, Z., Conesa, A., Rogers, R. L., & McIntyre, L. M. (2021). The evolution of splicing: transcriptome complexity and transcript distances implemented in TranD. bioRxiv, 2021.2009.2028.462251. https://doi.org/10.1101/2021.09.28.462251. https://github.com/McIntyre-Lab/TranD. 

Disclaimer:  While automated captions of TranD have been carefully constructed, users are advised to verify caption contents before use and report any errors to the TranD github.