Fig. 5. Analysis of Hh response and Ihh expression in skeletal elements. In situ hybridization using ³⁵S-labeled riboprobes for Ihh (A,B) and Ptc1 (CE) on longitudinal sections of the tibia at P3. Signals are shown in red and the sections are counterstained with Toluidine Blue. The boxed region in C is shown at a higher magnification in E. The straight lines in E demarcate the region populated by cells with morphology that is distinct from that of the marrow cells, similar to that defined in C and D of Fig. 4.