Figure 4.

Runx2 and Sox9 expression in craniofacial bone and cartilage during embryonic development. (A and A’) Wild type embryos at E14.5 have more Runx2 positive cells along calvarial bone plates than in END tissue (arrows). (B and B’) The cartilages in craniobase at E14.5 and (C and C’) E18.5 exhibited more Runx2 positive cells in wild type than in END, particularly some prehypertrophic and hypertrophic chondrocytes at E18.5 in wild type mouse (arrows) were strongly stained with Runx2 as compared to END tissue (arrow). In contrast to Runx2, (D and D’) the temporal cartilaginous tissue and (E and E’) cranial base at E14.5 revealed large number of Sox9 positive cells in both wild type and END tissues (arrows). However, (F and F’) the temporal cartilaginous tissue and (G and G’) cartilage in cranial base at E18.5 in END mouse contained more Sox9 positive chondrocytes than wild type late embryos (arrows), but the staining intensity was significantly less than that at E14.5. Results of Runx2 and Sox9 immunohistochemistry were quantitated by average pixel numbers positive staining per 400× field. Scale bar: 25um for A-G’.