Extended Data Figure 1. Oln^mT reporter mice showed that Osteolectin is expressed by osteoblasts, osteocytes, and chondrocytes in addition to peri-arteriolar LepR⁺ stromal cells.

(a-c) The mouse Osteolectin gene was modified to insert an mTomato-WPRE-pA cassette between the 5’ untranslated region and exon 3 to generate the targeting vector. These sites were selected to avoid disrupting conserved intronic sequences. Open boxes indicate untranslated regions and black boxes indicate translated regions of Osteolectin. The targeted founder mouse (F0) was identified by southern blotting (b) using 5’ and WPRE probes (black bars). (c) PCR genotyping of genomic DNA confirmed germline transmission of the Oln^mT allele. Mice were backcrossed at least three times onto a C57BL/Ka background before analysis. (d) Osteolectin transcript levels by qRT-PCR in Oln-Tomato⁺ and Oln-Tomato⁻ bone marrow cells (3 mice analyzed in 3 independent experiments). (e) Flow cytometry gates to distinguish Oln-mTomato⁺LepR⁺ from Oln-mTomato⁻LepR⁺ stromal cells in enzymatically dissociated bone marrow. (f) Osteolectin transcript levels by qRT-PCR in Oln-Tomato⁺LepR⁺ and Oln-Tomato⁻LepR⁺ bone marrow cells (4 mice analyzed in 4 independent experiments). (g) We did not detect Oln-Tomato in VE-cadherin-expressing bone marrow endothelial cells (4 mice per genotype analyzed in 4 independent experiments). (h and i) Femur epiphysis (h) and diaphysis (i) from Oln^mT/+; Col1a1*2.3-EGFP mice (images are representative of 3 independent experiments from 8–10-week-old mice). In panel h, the arrowhead points to Oln-Tomato⁺Col1a1*2.3-EGFP⁺ osteoblasts in trabecular bone and the arrow points to Oln-Tomato⁺Col1a1*2.3-EGFP⁻ hypertrophic chondrocytes in the growth plate (scale bar = 100μm). Panel i shows Oln-Tomato⁺Col1a1*2.3-EGFP⁺ osteoblasts at the endosteum (arrow), Oln-Tomato⁺ osteocytes (arrowhead), and Oln-Tomato⁺ periosteal cells (asterisk) (scale bars = 40μm). All data represent mean ± SD.