FIGURE 6.
PIIBNP, but not integrin αv, is present in developing cartilage. Immunohistochemistry for the type II collagen protein (A and C) and the integrin αv (B and D) in mouse embryonic E14.5 (A and B) humerus and E17.5 (C and D) digits. The type II collagen protein can be detected in the entire humerus or digit, including the developing cartilage (c) and the newly formed hypertrophic regions (h) (the region surrounding the nascent bone (b) in the digits). Detection of the integrin αv is primarily in the synovial cells lining the developing joint cavity (indicated by arrows) and in the hypertrophic region and appears to be excluded from the developing cartilage. Bar (A–G), 200 mm. E, Western blot detection of the PIIBNP protein in normal 56-day embryonic human limb using the chicken anti-exon 3–8 antiserum. Marker molecular weights are indicated. The control lane is recombinant GST-PIIBNP cleaved with thrombin showing the molecular mass of the PIIBNP to be ∼15 kDa. In the last three lanes, increasing concentrations of limb extract are shown with bands reacting with PIIBNP antibody at 16.1 kDa. The band at 16.1 is equivalent to the recombinant PIIBNP that migrates more slowly due to the hydroxylation of proline residues.