Fig. 2. Co-expression of Adamts3 and Col2a1 in musculoskeletal tissues. (A-G) In situ hybridization is used to show expression of Adamts3 in developing cartilage from 12.5 dpc to 17.5 dpc. In A-D, images include hybridization of Col2a1 to adjacent serial sections. Hoechst 33258 stained images are included on the far right for morphological correlation; the age of the embryo from which the section was taken is shown on the right. (A) Expression in initial sites of chondrogenesis in the developing ribs (arrows). (B) Expression in primordial cartilage of the ankle joint. T, tibia; Ts, Talus; C, calcaneus. (C) Expression in the proximal humerus growth plate. Note that expression is restricted to the proliferating zone (PZ). Hypertrophic zone chondrocytes (HZ) do not express Adamts3. Col2a1 is not expressed in the bone of the primary ossification center (B). Adamts3 is expressed in the perichondrium (arrow) and bone. (D) Proximal femur. The arrow indicates a tendon insertion site where Adamts3, but not Col2a1 is expressed. (E-G) 17.5 dpc skeletal elements, demonstrating that Adamts3 is not expressed by hypertrophic chondrocytes. (E) Absence of Adamts3 expression in the hypertrophic chondrocytes (HC) of the manubrium sterni. Note Adamts3 expression in developing intercostal muscle (arrow). (F) Ribs and vertebral lateral process. The rib elements contain hypertrophic chondrocytes (asterisk) that do not express Adamts3. By contrast, the lateral process of a thoracic vertebra (v) has small chondrocytes and these express Adamts3. The black oval indicates a spurious signal from erythrocytes. (G) Sagittal section through the basi-occiput (BO) and the dens (d) of the second cervical vertebra. Note the strong expression of Adamts3 in regions containing small chondrocytes and absence from the hypertrophic zone (asterisk). Expression is seen in the perichondrium (arrows). Scale bar: 100 µm.