Figure 1

Principal component analysis (PCA) and volcano plot of differentially abundant transcripts. (A) PCA plot of log₂ gene expression data showed the greatest variability in RNA-Seq data was due to the age of the donor. The second and third components are also shown as changes in the first and second components are due to differing sample sizes between young and old groups. (B) Volcano plot represents log₂ FC × log₂ CPM plot (counts per million mapped reads) CPM plot. Low expression genes (log₂ CPM of less than −5) are coloured orange. Significant differentially expressed genes (DEGs) are coloured in red. A set of DEGs between young and old tendon was identified. With the common dispersion in edgeR [30], 325 DEGs were identified with a P value of less than 0.05 (red).