Through the utilization of cultured chondrocytes, metatarsal organs, and genetic mouse models, researchers have discovered that the proliferation of chondrocytes is inhibited by FGFR3 signaling.41, 42, 43, 44 The incorporation of [3H]thymidine labeling in the epiphyseal chondrocytes of cultured fetal rat metatarsals was reduced by FGF2 treatment,45 while severely reduced proliferation was found in the chondrocyte cell line CFK2 expressing the mutant FGFR3 that causes ACH. This evidence concerns the gene FGFR3 and achondroplasia.