Fig. 1. BMP signaling regulates chondrocyte differentiation. (A-D) Forelimbs of E14.5 mouse embryos were cultured for 4 days and photographed before (A) and after (B-D) culture. Serial sections of these limbs were hybridized with riboprobes for Ihh (E-H) or ColX (I-L). Uncultured limbs (A) display the characteristic expression domains of Ihh in prehypertrophic (E) and ColX in hypertrophic (I) chondrocytes. Limbs cultured for 4 days increase in size (C) but display the normal distribution of Ihh- (G) and ColX- (K) expressing cells. Treatment with BMP2 results in a further enlargement of the cartilage elements (D) and an increased size of the Ihh (H) and ColX (L) expression domains. By contrast, Noggin treatment blocks limb growth (B) and results in reduced expression of Ihh (F) and ColX (J). (A-D) Ruler indicates relative size units. In E-L ulna is upwards and radius is downwards.
