Figure 7. CircRNA increases during aging are largely independent of host gene expression.

(a) Barplots comparing the percentage of RNAs differentially expressed between 22 mo versus 1 mo samples from each tissue. FC = Fold Change. For cortex and hippocampus, the trend for age-upregulation is much stronger globally for circRNAs compared to linear RNAs. In contrast, a greater upregulation trend is seen for linear RNAs compared to circRNAs in heart. (b) Density plots comparing the log₂ fold changes in circRNA transcripts per million (TPM) in 22 mo versus 1 mo samples on the Y-axis and the corresponding fold change FPKM of linear RNAs (22 mo versus 1 mo) from the corresponding gene on the X-axis. Cortex circRNA/mRNA density plot shows a strong trend for circRNA accumulation independent of cognate linear RNA expression from the same gene. (c) Hippocampus circRNA versus mRNA density plot shows similar trends as cortex. (d) Heart circRNA/mRNA density plot lacks circRNA age-upregulation trend.