Fig. 4. Gene expression of cartilage-to-bone-associated genes and the formation of primary spongiosa are inhibited in Kif3a-deficient synchondroses. (A,F) Parasagittal serial sections of P7 control (A) and mutant (F) spheno-occipital synchondrosis were stained with fast green/Safranin O to reveal bone tissue (dark blue). Notice the marked reduction of primary bone spongiosa in mutant tissue (F), which is highly visible in controls (A, arrowheads). (B-E,G-J) Expression of the indicated genes as revealed by in situ hybridization with serial sections of control (B-E) and mutant (G-J) tissue. The hybridization signal was given artificial colors and images were superimposed with hematoxylin histologic images of the corresponding field. Scale bar: 80 µm in E for A-J.