Fig. 3. Fluorescent double in situ hybridizations showing expression of Coll IX, Coll II and Opn relative to each other and to the domains of Runx2, PTHrP-R, Bmp4 and Bmpr1b expression. (A-C) Direct comparison of the Opn and Coll IX expression domains. (C) There are cells that express Coll IX only (red; broad arrows), Opn only (green; arrowheads) or that co-express Opn and Coll IX (yellow; narrow arrows). (D-F,J-O) Considerable overlap is detected between Opn and Bmp4 (D-F), between Runx2 and Coll IX (J-L), and between Coll IX and PTHrP-R (M-O). (G-I) Expression domains of Opn (green) and Runx2 (Cbfa1; red) have very little or no overlap. The same is true for the expression domains of Coll II versus BspII (S-U) and Ihh versus Opn (V-X). Some overlap is detected for the expression domains of Bmpr1b versus Ptc1 (P-R). Scale bar: 200 µm.