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Fig. 2
Co-expression of chondrocyte and osteoblast genes in repair cartilage. (A) Colorimetric in situ hybridization shows gene expression in the cartilage callus anterior to the cut site of the lower jawbone. The chondrocyte markers sox9a and col2a1a are seen in the cartilage callus by 6dpr, with a peak of expression at 8dpr. Expression of the hypertrophic chondrocyte marker col10a1 begins at 8dpr. The osteoblast markers runx2b and col1a1a are expressed in mesenchyme and early cartilage at 6dpr and beyond. By 10dpr, expression of the osteoblast marker spp1 is evident in the cartilage callus. (B) Two-color fluorescent in situ hybridization shows co-expression of col2a1a with col1a1a or runx2b at 10dpr. Dashed lines show resection sites and magnified regions (white boxes) demonstrate that individual cells co-express both markers. Hoechst labels nuclei in blue. (C) Summary of the time course of expression within the cartilage callus. Scale bars: 100µm.