Unchanged aging phenotypes and altered transcriptome of old HSCs relocated into young BM niches. (A) γH2AX/FBL immunofluorescence staining for the indicated HSC populations. Scale bar, 10 µm. (B) Single-cell division kinetics (n = cells) for the indicated HSC populations. (C) Principal component (PC) analysis of RNA sequencing data for young and old control HSCs and HSCs isolated from the indicated parabiosed pairs. (D) Number of DEGs with log2 fold change greater than or equal to 1 or less than or equal to −1 and FDR < 0.05 for the indicated comparisons. (E) Gene-set enrichment analyses of O/Y-Het HSCs compared with either Y-Het HSCs (left) or O-Het HSCs (right). Bold highlights pathways commonly found enriched in old HSCs in Fig. S4 A. NES, normalized enrichment score with FDR–adjusted P values. Data are means ± SD; *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001. Y-Het and O-Het HSC results in A and B are from Fig. 5 and are shown for comparison. SRP, signal recognition particle; UTR, untranslated region.