Fig. 5. Enhanced delay of chondrocyte hypertrophy in ß-catenin and Ptch1 double mutant embryos. Consecutive sections of the developing tibia at 14.5 dpc were examined by Safranin O staining and in situ hybridization with the indicated ³⁵S-labelled riboprobes. Hypertrophic chondrocytes are enlarged and stained light red by Safranin O. The expression domains of Ihh and ColX were smaller in both Ptch1^c/-; Col2a1-Cre and Catnb^c/-; Col2a1-Cre mutant embryos, and were missing in the Ptch1^c/-; Catnb^c/-; Col2a1-Cre double mutant (arrows). Pthrp expression was similarly upregulated in Ptch1^c/-; Col2a1-Cre and Ptch1^c/-; Catnb^c/-; Col2a1-Cre mutants (arrows).