Fig. 4. Expression of osteoblast-specific marker genes in long bones. In situ detection of marker genes expressed in osteoblasts of proximal tibiae sections derived from 4-week-old control (middle panel) and junB^–/– Ubi-junB littermates (right panel): type-I collagen (col-I, A-C), matrix metalloproteinase 13 (mmp13, D-F), osteopontin (opn, G-I) and osteocalcin (oc, J-L). The arrow indicates accumulation of osteocalcin-positive osteoblasts at the chondrocyte/osteoblast junction in mutant sections. Hybridisation of control sections with sense probes (left panel) served as controls for specificity. Sections were counterstained with Haematoxylin and Eosin. Magnification was 10x.