(A and B) Bone marrow sections from Nes-Gfp (A–A′′) and Hoxb6-CreERT2;RCE (B–B′′) E18.5 embryos (tamoxifen-induced at E10.5) immunostained with Osterix antibodies (Osx, red) to label osteoprogenitor cells. GFP+ Osx+ mesodermal-derived osteoprogenitors are marked with asterisks (insets 2–3). (C–C′′′) Perinatal recombination in Nes-CreERT2 mice efficiently targets bone marrow stromal Nes-GFP+ cells. Bone marrow section of a P7 Nes-Gfp;Nes-CreERT2;R26-Tomato mouse that received tamoxifen at birth, showing Nes-GFP+ cells (green), Nes-derived progeny (red), and double-positive cells (arrowheads). (D–F) Fate mapping of the progeny of nestin+ cells and limb mesoderm in E18.5/19.5 femoral bone marrow from Nes-CreERT2;RCE (D–D′′, F–F′) and Hoxb6-CreER;RCE fetuses (E). (D) GFP (green) and nuclei counterstained with DAPI (gray) in bone of E18.5 fetus induced with tamoxifen at E13.5. Neither proliferating (*) nor hypertrophic (**) chondrocytes showed GFP fluorescence (inset 1). (D′–D′′) Nes-derived cells with a similar morphology and distribution to Nes-GFP+ cells were detected near the cartilage–perichondrium interface (arrows) and within the chondro–osseous junction (arrowheads). (E and F) Bone marrow sections of (E) Hoxb6-CreER;RCE and (F) Nes-CreERT2;RCE E18.5 embryos induced with tamoxifen at E10.5 and E8.5, respectively, stained with S100 antibodies to label chondrocytes (red). High magnification views of cartilage (inset 2) showing abundant double-positive chondrocytes (arrowheads). (F) Nes-traced cells (green) were not chondrocytes (red, *) but infiltrated the chondro–osseous junction and trabecular bone (arrowheads). Scale bars: 200 μm (A–A′, B–B′), 100 μm (A′′, B′′), 50 μm (B′′3, C). BM, bone marrow; C, cartilage; GIFM, genetic inducible fate mapping.