Despite anatomical differences, femoral and sternal HSC^α-cats and femoral HSC^MFGs mainly associate with sinusoids and Cxcl12 stroma cells, reflecting frequencies of imaged BM. (A) Overview of HSC reporter mouse lines and corresponding bones used for full-bone, multicolor, quantitative imaging and analysis. (B-J) HSC-niche distance quantification in femurs and sterna of α-catulin^GFP/+ and Mds1^GFP/+Flt3^Cre reporter mice. (B-D) BODIPY⁺ adipocytes (B; n = 4 each); Col.1⁺/Opn⁺ bone surfaces (C; α-catulin^GFP/+ femur, n = 13; Mds1^GFP/+Flt3^Cre femur, n = 12; α-catulin^GFP/+ sternum, n = 14); and GFAP⁺ Schwann cells (D; n = 4 each) were not associated with HSC^α-cats. (E-G) Both femoral and sternal HSC^α-cats randomly associated with GP1bβ MKs (E; α-catulin^GFP/+ femur, n = 12; Mds1^GFP/+Flt3^Cre femur, n = 9; α-catulin^GFP/+ sternum, n = 8); Cxcl12 stroma (F; α-catulin^GFP/+ femur, n = 5; Mds1^GFP/+Flt3^Cre femur and α-catulin^GFP/+ sternum, n = 4); and laminin⁺ entire BM vasculature (F-G; α-catulin^GFP/+ femur, n = 9; Mds1^GFP/+Flt3^Cre femur and α-catulin^GFP/+ sternum, n = 8). (H-J) Only a minority of femoral and sternal HSC^α-cats localized near Sca1⁺ arteriolar (H; n = 4 each) and NG2⁺ periarteriolar niches (I; n = 4 each), whereas most were randomly associated with CD105⁺ sinusoids (J; α-catulin^GFP/+ femur, n = 12; Mds1^GFP/+Flt3^Cre femur, n = 4; α-catulin^GFP/+ sternum, n = 8). Data in panels B-J represent mean ± standard deviation. Statistical significance for the 0- to 5-μm bin was assessed by 2-tailed nonparametric Mann-Whitney U test. *P < .05; **P < .01; ***P < .001.