Fig. 1: Cxcl12-creER marks a quiescent subset of CXCL12⁺LepR⁺ BMSCs.

a Structure of Cxcl12-iCreER-bGHpA bacterial artificial chromosome (BAC) transgene. b–o Short-chase analysis of Cxcl12-creER⁺ cells. b Cxcl12^GFP/+; Cxcl12-creER; R26R^tdTomato (pulsed at P21) distal femurs with growth plates on top. Gray: DIC. Scale bar: 500 µm. n = 3 mice. c, d Immunostaining for endomucin (Emcn, c) and CD31 (d). Sn: sinusoids, At: arterioles. Arrows: sinusoid-attaching GFP^hightdTomato⁺ cells. Gray: DAPI. Scale bar: 10 µm. n = 5 mice. e Percentage of cells attaching Emcn⁺ sinusoids among GFP^hightdTomato^neg (green) or GFP^hightdTomato⁺ (red) cells. n = 5 mice. f Flow cytometry analysis of CD45/Ter119/CD31^neg bone marrow cells. Blue lines: control cells. n = 5 mice. g Leptin receptor (LepR) expression based on flow cytometry analysis. Blue line: isotype control. n = 3 mice. h LepR staining. Gray: DAPI (Center), DIC (metaphysis and endosteal zone). Scale bar: 20 µm. i Quantification based on histology. Percentage of BMSCs expressing Cxcl12-GFP (green dots), Cxcl12^CE-tdTomato (red dots) and LepR (purple dots). n = 7 fields from four mice (central marrow and endosteal surface), n = 5 fields from 4 mice (metaphysis). j Percentage of CD45/Ter119/CD31^neg subpopulations in S/G2/M phase. n = 5 mice. k Intracellular CXCL12 protein levels of CD45/Ter119/CD31^neg subpopulations. MFI: median fluorescence intensity. n = 4 mice. l EdU serial pulse assay of Cxcl12-creER⁺ cells. Cxcl12-creER; R26R^tdTomato mice were pulsed with tamoxifen at P21, then with EdU every 8 h for 3 days prior to analysis. Percentage of EdU⁺ cells among GFP^hightdTomato^neg (green) or GFP^hightdTomato⁺ (red) cells. n = 5 mice. m Intracellular SCF protein levels of CD45/Ter119/CD31^neg subpopulations. MFI median fluorescence intensity. n = 5 mice. n, o Col1(2.3 kb)-GFP; Cxcl12-creER; R26R^tdTomato. n Left panel: trabecular bone. Right panel: endosteal space. Gray: DIC. Scale bar: 20 µm. n = 4 mice. o Flow cytometry analysis of CD45/Ter119/CD31^neg cells harvested from Col1(2.3 kb)-GFP; Cxcl12-creER; R26R^tdTomato at P28 (pulsed at P21) bone marrow. Blue lines: control cells. n = 4 mice. ****p < 0.0001, ***p < 0.001, **p < 0.01, *p < 0.05, two-tailed, Mann–Whitney’s U test (e, l). Two-tailed, one-way ANOVA followed by Tukey’s post hoc test (i–k, m). All data are presented as mean ± s.d. Source data are provided as a Source Data file.