Extended Data Figure 3. Osteolectin⁺ cells create a niche for CLPs but not other hematopoietic stem/progenitor cells.

(a) 2-month-old Oln^iCreER/+; Rosa26^{loxp-tdTomato/+} mice were sublethally irradiated 3 days after tamoxifen administration. Two weeks later, none of the adipocytes in the bone marrow were Tomato⁺ (image representative of 3 independent experiments; scale bar = 60μm). (b) Representative H&E stained sections from ossicles formed by Oln-Tomato⁺ (left) or Oln-Tomato⁻ (right) stromal cells sorted from Oln^mT/+ mice showing bone (arrowheads), hematopoietic cells (arrow), and adipocytes (asterisk; images are representative of 5 independent experiments; scale bar = 100μm). (c-e) Oln^iCreER/+; Scf^fl/fl and Scf^fl/fl littermate controls were treated with tamoxifen at 2-months of age. One month later, blood from Oln^iCreER/+; Scf^fl/fl mice showed normal white blood cell (c), red blood cell (d) and platelet (e) counts (6 mice per genotype analyzed in 3 independent experiments). (f-k) Oln^iCreER/+; Scf^fl/fl mice and littermate controls exhibited no significant differences in the frequencies of B220⁺ B cells (f), CD3⁺ T cells (g), Gr-1⁺Mac-1⁺ myeloid cells (h), CD41⁺ megakaryocyte lineage cells (i), CD71⁺/Ter119⁺ erythroid lineage cells (j), HSCs or MPPs in the spleen (k; 6 mice per genotype analyzed in 3 independent experiments). (l) Bone marrow cells from Oln^iCreER/+; Scf^fl/fl mice and littermate controls gave similar levels of donor cell reconstitution upon competitive transplantation into irradiated mice (5 donor mice per genotype analyzed in 3 independent experiments). The differences between Oln^iCreER/+; Scf^fl/fl and Scf^fl/fl mice were not statistically significant in c-l. (m) Oln^mT/+; Scf^GFP/+ femur bone marrow showing Oln-Tomato⁺ osteoblasts at the endosteum were negative for Scf-GFP, while peri-arteriolar Oln-Tomato⁺ stromal cells were positive for Scf-GFP (representative of 3 independent experiments; scale bar = 80μm). (n) Oln^mT/+; Col1a1*2.3-EGFP femur bone marrow showing Col1a1*2.3-EGFP⁺ osteoblasts at the endosteum were Oln-Tomato⁺ (representative of 3 independent experiments; scale bar = 100μm). All data represent mean ± SD. Statistical significance was assessed using matched samples two-way ANOVAs followed by Sidak’s (c-e, and k-l) or Tukey’s (f-j) multiple comparisons tests.