Fig. 2. Mechanistic insights into human MuSC aging.
a, UMAP visualization of MuSC subpopulations identified from scRNA-seq. b, Tree visualization of the GO terms enriched among marker genes for every MuSC subpopulation. Top 10 clusters of GO terms defined based on semantic similarity are shown. c, Beeswarm Milo plot showing the distribution of log2(FC) in cell abundance with age across neighborhoods of MuSC subtypes; significantly differentially abundant neighborhoods are colored. d, Ribosome biogenesis enrichment score of MuSC subpopulations in young (five donors) versus aged (seven donors) individuals. P value: two-tailed Mann–Whitney–Wilcoxon test. *P < 0.05. e, Dot plot of ribosome biogenesis and RNA polymerase I complex genes in MuSC subpopulations. Dot size represents the proportion of cells expressing the gene in aged group, color represents log2(FC) in young versus aged. Significantly upregulated and downregulated genes were defined using the direction of log2 (FC), the proportion of cells > 0.05 and LTSR > 0.9 (significance value, ranging from 0 to 1, where 1 is confident estimate). See Source Data. f–j, Expression of senescence-associated (g) and ribosome assembly (h) genes in cultured human primary myoblasts (f) by both qPCR (three biological repeats per group) (g,h) and western blot (i,j). Three independent experiments were performed for western blot with similar results. P value: unpaired two-tailed t-test. *P < 0.05; **P < 0.01; ***P < 0.001. Illustration in f was created with BioRender.com. k,l, qPCR (three donors for both panels) of genes in FACS-sorted MuSC subpopulations. P value in k: one-way ANOVA test; P value in l: unpaired two-tailed t-test. *P < 0.05; **P < 0.01. m, Violin plots of CCL2, TNFAIP3 and NFKBIZ in ICA+ MuSCs from scRNA-seq data. P value: unpaired two-tailed t-test. n, qPCR of CHUK, NFKBIZ and CCL2 in FACS-sorted ICA+ MuSCs (three young versus three or four aged donors). P value: unpaired two-tailed t-test. *P < 0.05. All data presented in d, g, h, j–l and n are mean ± s.e.m. with individual data points shown. The exact P values are shown in the Source Data.