HSC^α-cats, dormant LR HSCs, and nondormant non-LR HSPCs all have similar BM niche signatures. (A-H) Comparative niche distance quantification of LR and non-LR HSPCs in femurs of DOX-treated SCL-tTA;H2B-GFP mice or of HSC^α-cats in α-catulin^GFP/+ reporter mice. (A-C) BODIPY⁺ adipocytes (A; n = 4 each); Col.1⁺/Opn⁺ bone surfaces (B; n = 13 each); and GFAP⁺ Schwann cells (C; n = 4 each) were not physically associated with HSPCs. (D-G) Some LR, non-LR HSPCs and HSC^α-cats located randomly near MKs (D; LR/non-LR, n = 4; HSC^α-cat, n = 12). Most were randomly associated with laminin⁺ vasculature (E; LR/non-LR, n = 7; HSC^α-cat, n = 9), whereas a few associated with Sca1⁺ arteries and arterioles (F; n = 4 each) or periarteriolar niches (G; n = 4 each). (H) LR and non-LR HSPCs, as well as HSC^α-cats randomly associated with CD105⁺ sinusoids (H; LR/non-LRC, n = 4; HSC^α-cat, n = 12). (I, J) Scatterplots showing 2-dimentional distance quantification of single LR HSPCs (green), non-LR HSPCs (gray dots), and RDs (purple dots) in relation to the entire vasculature and MKs (I; 90 LR, 270 non-LR and 383 RDs) or bone (J; 90 LR, 270 non-LR and 383 RDs). Data in panels A-H represent mean ± standard deviation. Statistical significance in the 0- to 5-μm bin was assessed by 2-tailed nonparametric Mann-Whitney U test. ns, not significant.