Fig. 6. Removal of Smo activity in chondrocytes reduces chondrocyte proliferation. (A) Similar reduction in chondrocyte proliferation between Cre10; Smoⁿ/Smo^c and Ihhⁿ/Ihhⁿ embryos. Proliferation was scored in tibal sections after in utero labeling of E14.5 embryos with BrdU. (B) In situ hybridization of a ³⁵S-labeled Ptc1 probe to tibial sections of Cre10; Smoⁿ/Smo^c embryos indicates a complete absence of Ihh signaling in proliferating chondrocytes at E13.5. Perichondrial signaling is unaffected. (C) Alcian Blue staining of the tibia at E13.5 indicates a similar reduction in growth between Cre10; Smoⁿ/Smo^c and Ihhⁿ/Ihhⁿ embryos. (D) In situ hybridization (³⁵S-labeled probes) of cyclin D1 on tibial sections of E14.5 embryos. Expression of Cyclin D1 is downregulated in chondrocytes of both Cre10; Smoⁿ/Smo^c and Ihhⁿ/Ihhⁿ embryos.