Figure 2.

Chondrocyte differentiation at E16.5. Hematoxylin/eosin staining (a–c) and type X collagen mRNA in situ hybridization (d–f) of wild-type, PTH/PTHrP-R^–/–, and PTHrP^–/– phalanges at E16.5. In contrast to PTHrP^–/– bones, which exhibit a spatial and temporal progression in chondrocyte differentiation (c and f), PTH/PTHrP-R^–/– bones show a delay in chondrocyte differentiation, as shown by the decrease in type X collagen expression (b and e), when compared with wild-type bones (a and d). However, the spatial distribution of the abnormally differentiated hypertrophic cells is identical (b, c and e, f).