Fig. 7. Pattern of cell proliferation in the knee joint at E13.5 in wild-type and homozygous ColII-FGFR31^ach line 2 mice. (A) Wild-type and (B) homozygous transgenic tissue stained for BrdU incorporation. Box a and Box c outline the growth plates of the tibia and femur, respectively. Box b outlines the region of the presumptive joint. The number of proliferating cells in the growth plates of the tibia and femur is comparable between wild-type and homozygous transgenic tissue, whereas there is a significant decrease in the number of proliferating cells in the presumptive joint space in transgenic tissue compared with wild-type tissue.