Fig. 4. In situ hibridization analysis for cartilage differentiation. Newborn tibial sections were hybridized with riboprobes specific for (A) collagen II (Col2a1, a marker for non-hypertrophic chondrocytes), (B) collagen X (Col10a1, a marker for hypertrophic and distal prehypertrophic chondrocytes), (C) Indian hedgehog (Ihh) and (D) PTH/PTHrP receptor (PP-R) (markers for prehypertrophic chondrocytes). In the mutant the expression domain of Col10a1 was slightly reduced compared to that in the wild type, whereas the other markers were expressed normally. ec, epiphyseal cartilage; h, hypertrophic zone; p, proliferative zone; ph, prehypertrophic zone. Bar, 100 µm.