Fig. 2: Summary of gene expression changes in the gastrocnemius muscle during aging across species.

a–c Principal component analysis (PCA) of transcript abundances during muscle aging in mice in (a), rats in (b) and humans in (c). Each dot corresponds to one sample with colors indicating organism age. The numbers associated with PCs indicate the fraction of the variance in gene expression across samples along the corresponding PC. d–f Distribution of the coefficients of variation (CVs) of individual genes per age/age group for mice in (d), rats in (e) and humans in (f). The higher the CV, the more variable the expression of the gene across replicates. Thin blue lines are baselines indicating the median CV for the youngest age/age group. Median values of CVs for other ages/age groups (thick blue lines within violin plots) are mostly located over the baseline, especially for older ages/age groups, indicating higher heterogeneity across replicates for these ages/age groups in comparison to the youngest one. Limits for y-axis were set to include both the 25th and 75th percentiles of data points and up to 1.5 times the interquartile range in both directions from percentiles (red). g–i Cumulative distribution of absolute log2-fold changes in gene expression between the youngest and oldest age groups of mice in (g), rats in (h) and humans in (i). Differential expression analysis was performed with the EdgeR tool³¹. Dashed lines designate the position of the log2-fold change of 1, numbers correspond to the fraction of genes with significantly different expression among all genes in the group of oldest compared to the group of youngest individuals (FDR < 0.01). Group numbers for age groups of biological replicates are: n = 8–9 for mouse, n = 9–10 for rat and n = 5–79 for human.