Fig. 6. Mosaic ablation of PPR in chondrocytes. (A) Mosaic activity of Cre recombinase of Ost-Cre transgenic mice in the growth plate. Ost-Cre:R26R doubly transgenic, an E17.5 embryo was stained with X-gal. ß-gal activity was seen in about 30% of the columnar chondrocytes. ß-gal-positive cells are few in the periarticular region. (B-I) In situ hybridization of E17.5 proximal tibias of Ppr^fl/fl (B,D,F,H) and Ost-Cre:Ppr^fl/fl (C,E,G,I). (D,E) Ihh is expressed in the hypertrophic region as well as ectopically differentiated hypertrophic cells in the Ost-Cre:Ppr^fl/fl growth plate. (F,G) Expression of Ptc (F,G) and Pthrp (H,I) is upregulated in the periarticular region in the mutant growth plate (arrowheads). (J) BrdU labeling. Increased labeling ratio despite the small periarticular region in Ost-Cre:Ppr^fl/fl. The areas indicated by red lines were subjected to BrdU-positive cell counting. Insets are magnified views of the periarticular region. Nine sections from three animals of each genotype were counted. *P<0.01.